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it will make maintaining a patent airway and mask seal more diffi cult. be exacerbated by a ventilation rate that exceeds the suggested rate for age. Gastric Distention Gastric infl ation and subsequent vomiting and aspiration are signifi cant risks associated with face-mask ventilation.57–59 Although proper ventilation technique will minimize the risk Street Smart of gastric infl ation, the risk cannot be eliminated. Therefore, the Paramedic must monitor for increasing abdominal girth, vomiting, and diffi culty performing ven- Continuously monitored pulse oximetry allows the tilation as signs of gastric infl ation. If gastric infl ation is Paramedic to monitor oxygenation saturation during detected, several interventions can be performed to minimize procedures such as suctioning and intubation. When its impact. the saturation begins to drop, stop the procedure and At the fi rst sign of gastric infl ation, the airway manager should reassess the ventilation rate, volume, and airway pres- ventilate/oxygenate the patient. sures. These should be corrected if needed. In addition, suc- tion should be prepared and made immediately available. If signifi cant gastric infl ation has occurred and is interfering In addition, the pulse oximetry will give a preliminary with ventilation, it must be corrected by placing either a naso- pulse rate and the hemoglobin oxygen saturation. The blood gastric or orogastric tube and attaching it to suction. Normal Poor Figure 22-17 Normal and abnormal pulse oximetry waveform. A good waveform indicates adequate perfusion to produce an accurate numerical value. 410 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. one of three ways. For all three methods, the mouth must be Street Smart opened using either a chin-lift technique or a crossed fi nger technique in which the thumb and index fi nger “cross” each other and push the teeth in opposite directions. Any visible A nasogastric tube is less likely to initiate a gag refl ex foreign bodies should be removed. than an orogastric tube and is a better choice for the In the fi rst method, the tongue is controlled with a tongue conscious, responsive patient. depressor or by the Paramedic using a jaw-thrust technique. The oral airway is inserted with the curvature in the same direction as the curvature of the airway and the tip of the oral airway toward the glottis. The oral airway is advanced until Failed Ventilation the fl ange rests on the lips and the positioning is reassessed to assure that the tongue has not been pushed posteriorly. This If the fi rst attempt at ventilation is unsuccessful, the Paramedic method is recommended for pediatric patients. must make an assessment of the causes of failure. This The second and third methods are similar in that neither assessment should reevaluate the provider, the patient, and requires a tongue depressor and in both the tip of the airway is the equipment being used. Once this assessment is complete, initially not pointing toward the glottis. Instead, the distal tip further consideration of additional interventions and equip- of the airway is either pointed toward the cheek (method 2) or ment must be made. toward the palate (method 3). The oral airway is advanced to Reevaluation approximately half its length and then rotated so that the distal tip points toward the glottis. The fl ange is again advanced to the In reevaluating the provider, the Paramedic must examine his lips and its position is confi rmed. own technique. Single-person bag-mask assembly ventila- Placement of the nasopharyngeal airway requires the tion, limited in the best of circumstances, may simply not be Paramedic to assess which nostril is more likely to accom- possible and another rescuer may be needed. All providers, modate the airway. Evidence of nasal fracture or septal devia- however, should have suffi cient skill and training to provide tion should be noted. Once the nare has been chosen, the tip two-person bag-mask assembly ventilation. of the nose should be pushed superiorly so that the nares are The patient should also be reassessed. The most com- closer to parallel with the face. With the bevel facing toward mon cause of ventilatory failure is that the airway was not the septum, the nasopharyngeal airway is inserted parallel to appropriately opened. Therefore, the airway opening tech- the fl oor of the nasal cavity. nique and the patient positioning should be evaluated. Ideally, Due to the design of nasal airways, different initial orien- the airway opening maneuver should be performed again.60 tation is required based on which nare is used. If the airway In addition, the patient should be reassessed to determine if is inserted in the right nare, the curvature of the nasal air- anatomic or pathologic features are making ventilation dif- way should be in the same direction as the curvature of the fi cult. Conditions which make forming a mask seal diffi cult nasopharynx. If the nasal airway is inserted into the left nare, were discussed earlier. The Paramedic must consider if any of however, the curvature is upside down. This is due to the way these conditions are present. the bevel is designed. Once the bevel is entirely within the left The Paramedic must then assess the equipment. side of the nasal cavity, the nasal airway is then rotated 180° Equipment failure is not uncommon and can occur at highly and the airway advanced. inopportune times. Masks may leak and oxygen sources may The airway is advanced until the fl ange rests against be empty. Mechanical ventilators may suffer part fatigue or the opening of the nare. If resistance is met, the nasal air- failure. If there is any suggestion of equipment malfunction, way should be gently rotated from side to side but should an alternative device should be considered and utilized. not be forced. The patient may gag and vomit; therefore, the Paramedic should be prepared to suction the patient if needed. Oropharyngeal and Nasophayngeal If the patient is gagging excessively or appears to be having Airway Placement diffi culty breathing, the Paramedic should remove the nasal Once the Paramedic has reassessed and repositioned the airway and replace it with a shorter one. patient, he must consider the use of ancillary techniques and equipment. The insertion of an oropharyngeal or nasopharyn- geal airway is therefore appropriate. Suctioning As discussed previously, oropharyngeal airways help to While reevaluating the airway, it may become evident that displace the tongue and, ultimately, the hyoid anteriorly. There vomit or fl uids in the airway need to be suctioned. The suc- are multiple methods for inserting oral airways. Personal pref- tion unit should have already been prepared for just such an erence, at least for the adult patient, is the best guide. eventuality. Although the fi nger sweep (discussed later) or The ultimate position of the oral airway is with the fl ange the use of the Magill forceps (discussed in Chapter 23) may resting at the lips and the curve of the oral airway matching be necessary to manage foreign bodies, blood and vomit can the curve of the oropharynx. The airway can be inserted in usually be handled with standard suctioning procedures. The Non-Intubating Airway Management 411 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. primary goal of suctioning is to minimize the risk of aspira- tion and to prevent it, if possible. All suctioning efforts must be directed toward that end. The rigid Yankauer or tonsil tip suction is the device of choice for suctioning the oral cavity and the oropharynx. If possible, the patient should be pre- and postoxygenated; how- ever, this may not be possible if the patient is apneic and the Paramedic has not been able to ventilate the patient. The tip should be placed in the mouth and advanced to the posterior oropharynx. At no time should the distal end of the tip be com- pletely out of sight. Suction is applied as the tip is withdrawn. The Paramedic should avoid applying suction to mucous mem- branes or other attached structures. No more than 15 seconds of suction should be applied continuously in order to avoid hypox- ia.61 After suctioning, the airway should be reassessed and, if appropriate, the patient should be ventilated and oxygenated. If on reassessment there remains a signifi cant amount of material that interferes with ventilation, resuction the patient. Obstructed Airway Management If after the second ventilation attempt it is impossible to ven- tilate the patient, the patient should be assumed to have an Figure 22-18 Infant back blows. airway obstruction. There are a number of causes of airway obstruction including the epiglottis, the soft palate, foreign bodies, laryngospasm, laryngeal edema, and airway trauma. If proper airway opening techniques were applied, then the then the patient must be transported rapidly or turned over to a epiglottis and soft palate should have been addressed. On the caregiver capable of performing advanced airway management other hand, obstruction laryngospasm, laryngeal edema, and procedures. No further value is gained by delaying on-scene. signifi cant airway trauma cannot be dealt with at a basic air- way management level. Efforts must focus on ventilating as best as possible and transporting the patient rapidly. Foreign Assisted Ventilation body obstruction, however, can and should be addressed. Although most patients who receive face-mask ventilation If the patient is conscious and has evidence of complete in the prehospital environment are apneic, some breathing airway obstruction, then abdominal thrusts should be applied patients will benefi t from ventilatory support. These patients from behind. It is important, whenever possible, to treat an may be tachypneic or bradypneic. The most important char- airway obstruction while the patient is conscious.62–65 Once acteristic of these patients is that their ventilatory effort is a patient with an airway obstruction becomes unconscious, insuffi cient to meet their metabolic demands. mortality increases rapidly.66 Therefore, aggressive manage- Assisted ventilation is the process of augmenting the ment of the conscious patient with a possible airway obstruc- breaths a patient is taking to provide more effective respira- tion is mandatory. tions. The device most commonly used for this process is the If, however, the patient becomes unconscious or is found BVM. The key to this technique is that the Paramedic must unresponsive and has a foreign body airway obstruction, the time ventilation with the patient’s own inspiratory effort and techniques of abdominal thrusts described in the following assure a minimum minute ventilation. In the patient who is text should be used. very bradypneic, it may be necessary to provide additional For infants, back blows are the preferred method of clear- breaths between the assisted breaths to meet the minimum ing the airway (Figure 22-18). Otherwise, the sequence of minute ventilation. On the other hand, for a patient who is back blows, airway assessment, and attempts at ventilation tachypneic, it is not necessary to supplement every ventila- remain the same. tion. The goal of assisted ventilation is to provide patients The fi nger sweep is a technique of limited value in the with approximately 12 to 20 breaths/minute that meet the EMS environment. Suction and laryngoscopy perform the patient’s appropriate tidal volume (6 to 8 cc/kg). task of foreign body management much more effectively. If the patient remains responsive, it is important to explain Finger sweeps are probably most useful in the patient who is what will be done and why it is being done. For the patient vomiting more than the suction can handle. who is already hypoxic, the face mask may cause claustro- If the patient still cannot be ventilated after suctioning, phobia and a sense of suffocation. In addition, the patient repositioning, and obstructed airway skills have been applied, may feel |
some resistance to inhalation. In addition, use of 412 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. an anxiolytic such as diazepam or midazolam may make the CPAP is essentially a way of assuring that in all phases of patient more comfortable during assisted ventilation.67 the respiratory cycle the airway pressure is above zero (zero An appropriate-sized mask is selected and the Paramedic being the atmospheric pressure). During the normal respi- makes a one-handed mask seal. The other hand gently com- ratory cycle, the intrathoracic pressure becomes negative presses the bag and stops when the bag is slightly dimpled. during inspiration, zero at the end of inspiration, positive dur- The Paramedic waits until the patient begins to inhale before ing expiration, and zero again at the end of expiration. These squeezing the bag to provide a full ventilation. When the pressures are generated not by external forces but rather patient begins to exhale, the bag is released. This process through the musculature and bony structures of the chest of supplementing the patient’s own inspiration should occur cavity. The mechanism for producing negative pressure was 12 to 20 times/minute. discussed in Chapter 20. Positive pressure is generated by the The most diffi cult part of this skill is the timing of the elastic recoil of the chest wall. The alveoli are held open via ventilation. If the ventilation is delivered while the patient is surfactant and their indirect attachment to the chest wall. At exhaling, not only will it be ineffective but also high airway the zero pressure end of expiration, however, the alveoli can pressures, barotrauma, and gastric infl ation may occur. If the collapse, resulting in atelectasis. This is the issue that CPAP breath is delivered too early, the patient will feel suffocated attempts to address. and uncomfortable. Therefore, the timing of the assisted In the healthy adult, sighing is a refl ex mechanism that breath is critical. The Paramedic must be able to sense when opens collapsed areas of the lung. Grunting against a closed the patient is beginning to inspire and deliver the assisted glottis achieves the same end. These mechanisms become ventilation at that time. There are three ways in which the less effective during disease. For the patient with emphy- start of inspiration can be determined. The fi rst is to simply sema, the alveolar walls break down, decreasing effective observe the patient’s chest. When the chest begins to expand, oxygen exchange surface and increasing the risk of col- the patient is inspiring, and the breath should be delivered. lapse. Patients with congestive heart failure (CHF) are also Unfortunately, these patients will not usually tolerate being more susceptible to alveolar collapse. At the end of expi- laid fl at and the Paramedic will often stand behind the upright ration, the surfactant in these patients may be insuffi cient patient. Therefore, observation may be ineffective. to keep open the airways, allowing the alveoli to collapse The two other methods of determining the start of inspi- during exhalation. These patients may not then have the ration do not require direct patient observation. The fi rst ability to re-expand the collapsed alveoli, and so they have involves placing a fi nger on the bag-mask assembly and less gas exchange surface and become more hypoxic and mandibular soft tissues. When the patient begins to inspire, hypercarbic. the mouth will usually open slightly and the larynx will pull CPAP uses a combination of gas fl ow and resistance to superiorly. These movements can be palpated and recognized exhalation to increase the minimum airway pressure. High- as the time to initiate ventilation. The other method involves fl ow gas (oxygen mixed with room air) is fed into the mask dimpling the bag with the fi ngers before providing the ven- at 50 to 100 LPM. The mask is tightly sealed against the tilation. By applying a slight amount of pressure to the bag, patient’s face, only allowing exhaled gas to escape through the pressure within the mask can be monitored. When the bag an exhalation port and CPAP valve. The CPAP valve is a begins to compress easily, the patient has begun to inspire and special valve designed to open at a set pressure (typically the bag should be squeezed to deliver the appropriate tidal 5 to 15 cm water). If that pressure is not present, the valve volume. Although this technique requires some practice, it is will not open. a very effective method of determining when to ventilate. As respiratory gasses can only escape through the CPAP The patient should be continuously assessed during valve, gas will build up in the system, resulting in increased assisted ventilation. While the increased tidal volume and pressure. The whole connected system includes the CPAP adequate minute ventilation may cause the patient to improve, generator, the large volume tubing, the face mask, the patient’s the patient’s underlying disease process may cause him to airways, and the lungs. The pressure will eventually equalize decompensate. The Paramedic must be vigilant to assure that throughout the system. Since the gas fl ow is so high, the pres- the patient is receiving adequate ventilatory support. sure in the system quickly reaches the opening pressure of the CPAP valve. If the CPAP valve is set to open at 10 cm H O, 2 then the pressure throughout the entire system, including the Continuous Positive alveoli, will be at least 10 cm H O. This air pressure prevents 2 Airway Pressure alveoli from collapsing and helps to open alveoli that are already collapsed.73,74 With almost 70 years of use in the hospital and home set- A number of other physiologic benefi ts have also been ting, continuous positive airway pressure (CPAP) devices are found with CPAP. The continuous pressure results in more slowly but surely making their way into the fi eld of prehospi- laminar (less turbulent) airfl ow. It has been associated with tal care.68–72 Simple, more lightweight, and considerably less improved oxygenation and ventilation, mainly through expensive technology has placed this mode of airway care improved diffusion and greater gas exchange surface area. into the reach of most EMS systems. There are a number of clinical benefi ts from these effects. Non-Intubating Airway Management 413 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. However, there are some limitations to CPAP. It does not gas leak through the CPAP valve. Although most patients will provide positive pressure ventilation; there is no difference receive adequate gas fl ow from a fi xed fl ow generator, there are in gas fl ow between inhalation and exhalation. Furthermore, some whose inspiratory effort and negative pressure will be the effects of CPAP are limited to the alveoli and the small in excess of the gas fl ow. When this happens, the CPAP valve airways. Large airway diseases are not effectively treated. closes and the pressure in the system drops below the level of CPAP has been used in a number of disease processes. the CPAP valve. For these patients, the variable fl ow genera- The most common prehospital application has been for tor allows the Paramedic to increase the gas fl ow to compen- patients with congestive heart failure. Not only does CPAP sate for the patient’s high demand. In addition, although the address atelectasis, but it also helps to drive edema back into hypoxia these patients experience is usually due to a diffusion the circulatory system by decreasing preload and afterload problem (not enough oxygen moving from the alveoli to the via increased intrathoracic pressure. Several prehospital trials bloodstream), some patients do need higher oxygen concentra- suggest that using CPAP decreases intubation rates, improves tions. The variable fl ow generators usually allow the Paramedic patient symptoms, and decreases myocardial damage during to adjust the oxygen concentration as well. Therefore, although the acute phase of CHF.75–80 No trial to date has demonstrated the variable fl ow generators are more complicated to use, they a long-term mortality difference. Nonetheless, there are more give the Paramedic fl exibility for the occasional patient whose important markers of the effectiveness of the treatment of needs exceed the capabilities of the fi xed fl ow generators. CHF than just mortality and CPAP has certainly been demon- CPAP is relatively simple to use (Skill 22-1). The CPAP strated to be effective in regards to these other markers. generator is attached to a 50 PSI oxygen source. A fi lter is CPAP has also been used in the treatment of COPD and attached to the air intake valve and the high-volume tubing asthma. There appear to be two main effects. First, turbulent is attached to the generator output port. An appropriate-sized airfl ow increases the work of breathing. The laminar airfl ow mask is selected, the high volume tubing is attached to the produced by CPAP, therefore, decreases the work of breathing. input port, and the head restraint is attached to the mask, leav- Additionally, infl ammation plays an important role in asthma ing one side open if possible. If the mask uses interchange- and chronic bronchitis. During acute exacerbations, CPAP able CPAP valves, the appropriate valve (usually 5 to 10 cm may help to decrease the edema in the walls of the airways. H O) is attached. If there is an adjustable valve, it is set to the 2 Although CPAP has been studied extensively in COPD, there lowest setting. If there is a built-in CPAP valve, no further is minimal literature on its utility in acute asthma. Therefore, preparation is necessary. the two main prehospital indications for CPAP are COPD Next, the oxygen is turned on. If the generator has exacerbations and acute pulmonary edema. an on/off knob or switch, it should also be turned on. The CPAP devices have become smaller and much easier to system will begin fl owing oxygen. The mask is handed use. Although nasal CPAP devices are used effectively in the to the patient, who should hold it to his face without sleep apnea populations and in some inpatient settings, full sealing the mask. The patient should be allowed to exhale face-mask CPAP is the most commonly used modality in against the CPAP valve without the mask being completely the prehospital and emergency department settings. The two sealed; this will reduce the feeling of suffocation the patient main categories of CPAP devices for prehospital use are the experiences. Once the patient begins to feel comfortable fi xed fl ow devices and the variable fl ow devices. breathing against resistance, the mask should be fi rmly sealed The fi xed fl ow devices are typically the easiest to use. against the face. The head strap should then be brought into They have no moving parts and no adjustments. The device is place and the last leg attached. The mask and head strap designed to deliver a fi xed fl ow of gas at a set oxygen percent- should be adjusted so that the mask seals against the face and age (usually 30% to 35%). The CPAP generator is attached there are no leaks. to a 50 PSI oxygen source, the mask and tubing are attached, The patient should then be assessed for comfort and abil- and a CPAP valve is selected. Some devices use a fi xed level ity to breathe with the level of CPAP. If the patient cannot of CPAP, others allow the user to switch between different tolerate the CPAP, the level can be reduced (if not already valves (typically 5, 7.5, and 10 cm H O), and some use an at its |
lowest level) or the mask seal can be broken to slightly 2 adjustable valve. Thus, although the gas fl ow and oxygen con- decrease the pressure in the system. If the patient is tolerating centrations are preset with these devices, the level of CPAP the CPAP he is on, it may be possible to increase the level. can usually be adjusted. Usually a level of 5 to 10 cm H O is appropriate. Generally 2 In contrast, the variable fl ow devices allow the Paramedic 15 cm H O is considered to be the upper limit. If a CPAP 2 some degree of choice in determining gas fl ow and oxygen of 15 cm H O or greater is used, a nasogastric (NG) tube 2 concentration. In order to maintain the minimum CPAP pres- should be placed. There should always be a small air leak sure (the valve pressure) throughout the entire respiratory from the CPAP valve, even during inspiration. If there is no cycle, there must be suffi cient gas fl ow to keep the CPAP valve leak and a variable fl ow generator is being used, the fl ow can slightly open at the point of most negative intrathoracic pres- be increased until there is an air leak. In addition, the patient sure. This point occurs during early inspiration. During the may benefi t from an anxiolytic. However, care must be taken rest of the respiratory cycle, there will be a more signifi cant not to depress the respiratory drive. 414 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. The patient must be observed for tolerance, improvement, The posterior occiput is signifi cantly more prominent or decompensation.81 Since the CPAP provides no ventilatory in the pediatric patient than in the adult.82 Therefore, when support, the patient must not be apneic. The patient is, how- the pediatric patient lays on a fl at surface, the neck is fl exed ever, at an increased risk for pneumothorax. Additionally, and the airway partially obstructed. To counter this, the the patient may begin to fatigue and decompensate before Paramedic should place a folded towel beneath the shoul- atelectasis begins to resolve. If this happens, the patient may ders so that the head rests in a neutral position. Conversely, need to be intubated or the CPAP switched to assisted ventila- the pediatric trachea is smaller and more susceptible to tion. The patient should be attached to a pulse oximeter, vital kinking. When the head is extended, there is a potential for signs should be obtained, and the EKG (rhythm strip) should the trachea to kink and become occluded. Therefore, head be monitored. extension should be done carefully, again with the intent to In addition, end-tidal carbon dioxide monitoring can be per- keep the head in a relatively neutral position. formed. This has never been formally studied but, anecdotally, a In addition, the nasal bridge of the pediatric patient is small but consistent waveform is seen. Therefore, the end-tidal fl atter than an adult’s. The mask, therefore, is more diffi cult CO monitor may offer an apnea alarm. to seal. Due to the fl exibility of the airway, however, increas- 2 If the patient is switched to positive pressure assisted venti- ing pressure on the mask puts the patient at increased risk lation, it may be possible to attach a positive end expiratory pres- for airway obstruction. Therefore, a two-rescuer approach to sure valve to the exhalation port and, in essence, provide CPAP if ventilation is often more successful. the patient is also breathing on his own. There are no studies on Ventilating the pediatric patient requires care to pre- using the PEEP valves this way, but they should serve the same vent overpressurization. Causing a pneumothorax in a function if a good mask seal is maintained. pediatric patient is relatively easy and may be diffi cult CPAP has clearly been demonstrated to decrease intu- to diagnose in the prehospital environment. Additionally, bation rates and to provide symptomatic improvement in pediatric patients are more susceptible to gastric infl a- prehospital patients with congestive heart failure. It is also tion and are less able to tolerate it. Therefore, ventilation effective for patients with COPD and may be effective with should be suffi cient to just cause the chest to start to rise. asthma as well. CPAP is easy to use and may free a provider Although cricoid pressure can be used to decrease the risk who would otherwise need to provide assisted ventilation. of gastric infl ation and vomiting, the relatively malleable Concurrent treatment for the underlying disease should also trachea puts the pediatric patient at risk for complete air- be performed: loop diuretics, morphine, nitrates, and oxygen way obstruction with excessive pressure. for CHF and albuterol, ipratropium bromide, and steroids for Pediatric patients generally suffer cardiac arrest sec- COPD and asthma. When used appropriately, improved pre- ondary to respiratory arrest, as opposed to adults who suf- hospital outcomes should be seen. fer primary cardiac arrest.83–85 Once a pediatric patient goes For a step-by-step demonstration of Application of into cardiac arrest, a grim prognosis is almost assured. Continuous Positive Airway Pressure, please refer to Therefore, Paramedics must be more aggressive about pro- Skill 22-1 on page 416. viding early interventions and early respiratory support. As Gausche–Hill and her colleagues have demonstrated, the key to management of pediatric respiratory emergencies is Pediatric Considerations in Basic not in the advanced skills, but rather in the basic airway Airway Management manipulation and face-mask ventilation.86 Therefore, con- stant retraining and practical experience are key elements to In general, the techniques of basic adult and pediatric airway performing effective pediatric airway management. management are the same. However, there are a few impor- tant differences with which the Paramedic must be familiar. These relate to differences in anatomy and physiology. Non-Intubating Airway Management 415 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Skill 22-1 Application of Continuous Positive Airway Pressure 2 Set fl ow rate on device per manufacturer’s recommendations and protocol. 1 Assemble equipment. 3 Apply face mask to patient and snug down straps. 416 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Skill 22-1 (continued) 4 Coach patient to breathe with the mask. 5 Monitor and reassess the patient. Non-Intubating Airway Management 417 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Although tracheal intubation remains the “gold standard” of airway management, basic airway management is the most critical and fundamental airway management that the Paramedic can perform. Whether that provider is an EMT, a Paramedic, a nurse, or a physician, knowledge and skill in basic airway management is mandatory. Expertise with a number of skills and devices allows the Paramedic to ventilate patients through simple face-mask techniques. In addition, CPAP and other advances in airway technology allow critically ill patients to be managed without the need for intubation. The Paramedic should advocate for the best possible care for his patients and basic airway management is often just what the patient needs. Key Points: • Preoxygenation for any patient in need of active • The use of a venturi mask in the prehospital setting airway management or ventilatory support increases is generally limited to specialty care services. the diffusion gradient of oxygen into the plasma. It also provides a “reservoir” of oxygen in the lungs • Oropharyngeal and nasopharyngeal airways in the event the patient becomes apneic. Oxygen facilitate displacement of the most common therapy can also decrease the patient’s respiratory anatomic structures that obstruct the airway: the distress, in turn decreasing catecholamine release soft palate and the epiglottis. and myocardial oxygen demand. • The bag-mask assembly is the most commonly used • Compressed oxygen cylinders are the most common device for providing assisted ventilation and is method of storing oxygen in the prehospital available in adult and pediatric sizes. environment. • Excellent bag-valve-mask technique is important to • A regulator is used to decrease the pressure from prevent overventilation of the patient and gastric which oxygen is stored to a tolerable level suitable infl ation. In addition to technique, the mask must for patient use. be appropriately sized. • The nasal cannula is a pronged device designed for • Barrier devices and pocket masks can provide a nasal oxygen delivery at a rate of 0.5 to 6 LPM and good alternative to one-rescuer bag-mask assembly can deliver up to a 40% FiO2. ventilation until assistance arrives. • The simple face mask seals over the mouth and nose • Manually triggered fl ow-regulated, oxygen-powered and delivers oxygen and room air drawn in through ventilation devices deliver high oxygen fl ow rates an open side port. The mixture of room air and (40 LPM) while using oxygen only during the oxygen at 10 LPM can produce a FiO2 of 40% to 60%. “inhalation” phase of ventilation. • Oxygen delivered via a nonrebreather mask is not • Manually triggered fl ow-regulated, oxygen-powered diluted by room air and uses a reservoir bag and ventilation devices have a limited amount of one-way valve to ensure a continuous inspiratory research that compares these devices to other fl ow of oxygen to the patient. The nonrebreather ventilation devices. face mask can deliver up to 80% FiO2. • Automatic transport ventilators (ATVs) are • A demand valve regulator can provide 100% FiO mechanical devices that deliver a specifi ed volume 2 by delivering high LPM fl ows of 100% oxygen upon of respiratory gas and allow one rescuer to deliver inspiration. consistent tidal volumes at a set rate. 418 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. • The suction unit is used to remove vomit, blood, • It is diffi cult for a single rescuer to provide effective and some foreign bodies from a patient’s airway. tidal volumes while simultaneously forming a • proper mask seal, maintaining an open airway, and The patient should be pre- and postoxygenated and squeezing the bag. Two-rescuer, and even t hree- the Paramedic should suction for no more than rescuer, ventilation techniques are more commonly 15 seconds while withdrawing the tip. performed and preferred. • A rigid pharyngeal suction catheter known as a • While continuously monitoring the patient, the Yankauer or a soft sterile suction catheter is useful most important assessments are observation, in the prehospital environment. auscultation, and physiologic monitoring. • The most common anatomical cause of airway • A complete reassessment of airway, breathing, obstruction is the epiglottis |
and the soft palate, and circulation, including lung fi elds and epigastric so airway management techniques are oriented auscultation, should be performed anytime a toward establishing a patent hypopharynx. patient’s status changes. After observation and • The modifi ed jaw thrust must be used for patients auscultation, the patient should have physiologic with suspected cervical spine injury. signs measured and monitored. These include pulse, blood pressure, EKG, and pulse oximetry. • Cricoid pressure is a non-invasive technique that, when maintained continuously, can limit the risk • While reevaluating the airway, the Paramedic of aspiration and decrease gastric infl ation during should be prepared to suction any foreign bodies, positive pressure ventilation. blood, or vomit from the airway. • Limitations to cricoid pressure include excessive • Some conscious and breathing patients may present with insuffi cient ventilatory efforts and will benefi t posterior pressure with patients with suspected from assisted ventilatory support commonly C-spine injuries, possible laryngeal trauma or provided via a BVM. esophageal rupture, and in pediatric patients possible occlusion of the trachea. • During the normal respiratory cycle, the • intrathoracic pressure becomes negative during Bag-valve-mask ventilation requires an effective inspiration, zero at the end of inspiration, positive mask seal plus an open airway. during expiration, and zero again at the end • When ventilating, the trachea usually offers the of expiration. The alveoli can collapse at zero path of least resistance but excessive volumes of air pressure, resulting in atelectasis. will end up in the stomach. • Continuous positive airway pressure (CPAP) is used • It is best to deliver a tidal volume of 6 to 8 cc/kg to re-expand collapsed alveoli caused by alveolar ideal body weight/breath. wall breakdown or insuffi cient surfactant that would otherwise decrease gas exchange surface area. • With ventilatory rates of 12 to 16 breaths per minute for adults and 20 breaths per minute • Two main prehospital indications for CPAP are COPD for pediatric patients, the inspiratory phase of exacerbations and acute pulmonary edema. ventilation should occur over two seconds and • CPAP delivery devices for prehospital use are either the expiratory phase should take about the same fi xed fl ow devices or variable fl ow devices. Variable amount of time. fl ow devices allow the Paramedic to increase gas • The average adult bag-valve-mask assembly fl ow to compensate for a patient’s high demand or holds 1,600 mL, and approximately one third of adjust the oxygen concentration, FiO2. the volume of that bag would be delivered for • When using CPAP, the patient must be observed for a 70 kg patient. tolerance, improvement, or decompensation. Non-Intubating Airway Management 419 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. • For pediatric patients, head fl exion and extension • More successful outcomes of pediatric respiratory may partially obstruct or occlude the airway when emergencies have been demonstrated not with performing airway maneuvers and ventilations. The advanced skills but rather with basic airway pediatric patient’s head should rest in a relatively manipulation and face-mask ventilation. neutral position and a two-rescuer approach to ventilation is recommended. Review Questions: 1. Why is preoxygenation important for any 7. When using an automatic transport ventilator, patient in need of active airway management or what should the Paramedic specifi cally monitor ventilatory support? for while performing her ongoing assessment? 2. Compare and contrast the characteristics of, 8. Why is it important to know how much air a bag and indicated uses for, a nasal cannula and a valve device holds? nonrebreather face mask. 9. Describe one-, two-, and even three-rescuer 3. Describe the process measuring oropharyngeal ventilation techniques. and nasopharyngeal airways. 10. After opening the patient’s airway and 4. Before ventilating the patient with a bag-valve successfully ventilating him, what continuing mask, how is the appropriate size selected for ventilatory care should be carried out? the patient? 11. Name two indications for CPAP and explain 5. Describe the proper technique for mask-to-face how CPAP is benefi cial to both. interface. 12. How would one assess the adult and pediatric 6. What is the signifi cance of the 30 cm water patients for appropriate ventilation? when ventilating the patient? Case Study Questions: Please refer to the Case Study at the beginning of the 3. What hemodynamic effects does CPAP cause? chapter and answer the questions below: 4. What physiologic signs must the Paramedic assess 1. How does CPAP decrease the work of breathing? when using CPAP? 2. Describe how CPAP increases oxygenation. 420 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. References: 1. Larmon B, Schriger DL, Snelling R, Morgan MT. Results of a 21. Taylor DM, Bernard SA, Masci K, Macbean CE, Kennedy MP. 4-hour endotracheal intubation class for EMT-Basics. Ann Emerg Prehospital noninvasive ventilation: a viable treatment option in Med. 1998;31(2):224–227. the urban setting. 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Cricoid pressure: teaching mask ventilation devices. Respir Care. 1989;34(3):191–195. the recommended level. Anesth Analg. 1996;83(4):859–863. 57. Weiler N, Heinrichs W, Dick W. Assessment of pulmonary 40. Ewart L. The effi cacy of cricoid pressure in preventing gastro- |
mechanics and gastric infl ation pressure during mask ventilation. esophageal refl ux in rapid sequence induction of anaesthesia. Prehosp Disaster Med. 1995;10(2):101–105. J Perioper Pract. 2007;17(9):432–436. 58. Ho-Tai LM, Devitt JH, Noel AG, O’Donnell MP. Gas leak and 41. Stanton J. Literature review of safe use of cricoid pressure. gastric insuffl ation during controlled ventilation: face mask versus J Perioper Pract. 2006;16(5):250–251, 253–257. laryngeal mask airway. Can J Anaesth. 1998;45(3):206–211. 42. Butler J, Sen A. Best evidence topic report. Cricoid pressure 59. Vyas H, Milner AD, Hopkin IE. Face mask resuscitation: does it in emergency rapid sequence induction. Emerg Med J. lead to gastric distension? Arch Dis Child. 1983;58(5):373–375. 2005;22(11):815–816. 60. American Heart Association. Part 4: adult basic life support. 43. Gobindram A, Clarke S. Cricoid pressure: should we lay off the Circulation. 2005;112(24Supplement):IV-19–IV-34. pressure? 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AMA Council on Scientifi c Affairs.Choking: the Heimlich rescuer CPR: the method of choice for fi refi ghter CPR? Ann maneuver (abdominal thrust) vs. back blows. Conn Med. Emerg Med. 1995;26(1):25–30. 1984;48(9):609–612. 48. Higdon TA, Heidenreich JW, Kern KB, Sanders AB, Berg RA, 65. Dupre MW, Silva E, Brotman S. Traumatic rupture of the Hilwig RW, et al. Single rescuer cardiopulmonary resuscitation: stomach secondary to Heimlich maneuver. Am J Emerg Med. can anyone perform to the guidelines 2000 recommendations? 1993;11(6):611–612. Resuscitation. 2006;71(1):34–39. 66. Kumar P, Athanasiou T, Sarkar PK. Inhaled foreign bodies in 49. Srikantan SK, Berg RA, Cox T, Tice L, Nadkarni VM. Effect of children: diagnosis and treatment. Hosp Med. 2003;64(4): one-rescuer compression/ventilation ratios on cardiopulmonary 218–222. resuscitation in infant, pediatric, and adult manikins. Pediatr Crit 67. Masip J. Non-invasive ventilation. Heart Fail Rev. 2007;12(2): Care Med. 2005;6(3):293–297. 119–124. 50. Willis DH, Jr., Liberti JP. Post-receptor actions of somatomedin 68. Goss JF, Zygowiec J. Positive pressure: CPAP in the treatment of on chondrocyte collagen biosynthesis. Biochim Biophys Acta. pulmonary edema & COPD. Jems. 2006;31(11):48, 50, 52–58 1985;844(1):72–80. passim; quiz 64. 51. Conlon NP, Sullivan RP, Herbison PG, Zacharias M, Buggy DJ. 69. Sullivan R. Prehospital use of CPAP: positive pressure positive The effect of leaving dentures in place on bag-mask ventilation at patient outcomes. Emerg Med Serv. 2005;34(8):120, 122–124, 126. 422 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. 70. Hubble MW, Richards ME, Jarvis R, Millikan T, Young D. 78. Pang D, Keenan SP, Cook DJ, Sibbald WJ. The effect of positive Effectiveness of prehospital continuous positive airway pressure pressure airway support on mortality and the need for intubation in the management of acute pulmonary edema. Prehosp Emerg in cardiogenic pulmonary edema: a systematic review. Chest. Care. 2006;10(4):430–439. 1998;114(4):1185–1192. 71. Kosowsky JM, Gasaway MD, Stephanides SL, Ottaway M, Sayre 79. Park M, Sangean MC, Volpe Mde S, Feltrim MI, Nozawa E, Leite MR. EMS transports for diffi culty breathing: is there a potential PF, et al. Randomized, prospective trial of oxygen, continuous role for CPAP in the prehospital setting? Acad Emerg Med. positive airway pressure, and bilevel positive airway pressure 2000;7(10):1165. by face mask in acute cardiogenic pulmonary edema. Crit Care 72. Hatlestad D. Calming the waters: noninvasive positive pressure Med. 2004;32(12):2407–2415. ventilation in prehospital care. Emerg Med Serv. 2002;31(5): 80. Mehta S, Jay GD, Woolard RH, Hipona RA, Connolly EM, 67–71, 74. Cimini DM, et al. Randomized, prospective trial of bilevel versus 73. Schreiter D, Reske A, Stichert B, Seiwerts M, Bohm SH, continuous positive airway pressure in acute pulmonary edema. Kloeppel R, et al. Alveolar recruitment in combination with Crit Care Med. 1997;25(4):620–628. suffi cient positive end-expiratory pressure increases oxygenation 81. Duncan AW, Oh TE, Hillman DR. PEEP and CPAP. Anaesth and lung aeration in patients with severe chest trauma. Crit Care Intensive Care. 1986;14(3):236–250. Med. 2004;32(4):968–975. 82. Gausche-Hill M. Pediatric Airway Management for the Pre- 74. Karmrodt J, Bletz C, Yuan S, David M, Heussel CP, Markstaller Hospital Professional. Sudbury: Jones and Bartlett Publishers, K. Quantifi cation of atelectatic lung volumes in two different Inc.; 2005. porcine models of ARDS. Br J Anaesth. 2006;97(6):883–895. 83. Bardella IJ. Pediatric advanced life support: a review of the 75. Moritz F, Brousse B, Gellee B, Chajara A, L’Her E, Hellot AHA recommendations. American Heart Association. Am Fam MF, et al. Continuous positive airway pressure versus bilevel Physician. 1999;60(6):1743–1750. noninvasive ventilation in acute cardiogenic pulmonary edema: a 84. Wright JL, Patterson MD. Resuscitating the pediatric patient. randomized multicenter trial. Ann Emerg Med. 2007;50(6): Emerg Med Clin North Am. 1996;14(1):219–231. 666–675. 85. Hickey RW, Cohen DM, Strausbaugh S, Dietrich AM. Pediatric 76. Ursella S, Mazzone M, Portale G, Conti G, Antonelli M, patients requiring CPR in the prehospital setting. Ann Emerg Gentiloni Silveri N. The use of non-invasive ventilation in the Med. 1995;25(4):495–501. treatment of acute cardiogenic pulmonary edema. Eur Rev Med 86. Gausche M, Lewis RJ, Stratton SJ, Haynes BE, Gunter Pharmacol Sci. 2007;11(3):193–205. CS, Goodrich SM, et al. Effect of out-of-hospital pediatric 77. Winck JC, Azevedo LF, Costa-Pereira A, Antonelli M, Wyatt JC. endotracheal intubation on survival and neurological outcome: a Effi cacy and safety of non-invasive ventilation in the treatment controlled clinical trial. Jama. 2000;283(6):783–790. of acute cardiogenic pulmonary edema—a systematic review and meta-analysis. Crit Care. 2006;10(2):R69. Non-Intubating Airway Management 423 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. KEY CONCEPTS: Upon completion of this chapter, it is expected that the reader will understand these following concepts: • The implements of intubating airway management • End-tidal carbon dioxide monitoring, the “gold standard” of proper placement • Principles of patient airway assessment and how to make the fi rst attempt at endotracheal intubation the best attempt • A backup plan, using rescue devices when faced with a diffi cult airway • Post-intubation care and special considerations in airway management Case Study: The patient was in cardiac arrest and emergency medical responders had been doing CPR before the arrival of the Paramedics. The patient’s stomach was distended and she had vomited. Despite the best efforts of the responders, the airway could not be cleared with suctioning alone and the risk of aspiration was growing. “This patient will need to be intubated to protect that airway as soon as possible,” thought the arriving Paramedic. 424 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Intubating Airway Management 425 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. OVERVIEW Endotracheal intubation remains the defi nitive airway management technique, even though it is a complex procedure which requires constant practice in order to remain profi cient. Even under the best of circumstances, there are times when the Paramedic cannot intubate a patient. Therefore, it is important for the Paramedic to have a plan for that situation and alternative ways of managing the airway. The Paramedic must also provide continuous care for the intubated patient and be prepared for aberrant circumstances in airway management. The Advanced Airway Management Algorithm, together with the skills covered in this chapter and the last, should provide the Paramedic with the necessary tools to perform airway management and continuing supportive care. This chapter examines the use of intubating airway management and the principle of patient airway assessment to make the Paramedic’s fi rst attempt at endotracheal intubation the best attempt. The Intubating Airway the patient is in need of active airway management. The Paramedic begins by preoxygenating the patient and, if neces- Management Algorithm sary, ventilating the patient using the techniques discussed in The Intubating Airway Management Algorithm (Figure 23-1) Chapter 22. Once these interventions have been assured, the begins with the same assessment completed in Chapter 21: Paramedic must prepare his or her equipment. Patient assessment: Patient needs to be intubated Preoxygenate, ventilate PRN, prepare equipment If patient is breathing, consider nasal intubation Yes Attempt orotracheal intubation: • Confirm position Successful? with 3 methods. No • Secure tube. • Monitor patient. Ventilate. Reassess provider, patient, and equipment. • Confirm position with 3 methods. Yes • Secure tube. Attempt intubation (x 2): Successful? • Monitor patient. No Ventilate, prepare Blind Insertion Airway Device • Confirm position Yes with 3 methods. Attempt BIAD placement: Successful? • Secure tube. No • Monitor patient. Attempt to ventilate with BVM/ATV: Yes Monitor patient, Successful? transport No emergently Consider obstructed airway. If unable to clear Yes Monitor patient, obstruction, attempt surgical airway: Successful? transport No emergently Transport patient emergently. Consider requesting physician intercept. Figure 23-1 Intubating airway management algorithm. 426 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Equipment for Intubating Airway Management By far, the most common technique used to intubate patients is orotracheal intubation using direct laryngoscopy. A lar- yngoscope is used to visualize the larynx and the vocal cords, and an endotracheal tube is observed to pass through the vocal cords. Although simple in description, there are nuances to the equipment and procedure that can make intubation more or less easy. In addition, numerous other methods of intubation—such as nasotracheal intubation, digital intubation, fi beroptic assisted intubation, and lighted wand techniques— exist and are potentially important tools in the Paramedic’s armamentarium. Endotracheal intubation offers many advantages over Figure 23-2 Endotracheal intubation equipment. other techniques. An endotracheal tube offers direct access to a patient’s airway that is relatively protected. Intermittent p ositive pressure ventilation, tracheobronchial suctioning, and medication delivery are all possible. Although an endotracheal Table 23-1 List of Suggested Contents tube does not absolutely prevent aspiration, it signifi cantly of an Airway Management Kit decreases the likelihood of aspiration. One of the g reatest • Laryngoscope handles (adult and pediatric) advantages of the endotracheal tube over non- intubated ven- • Miller blades (00 to 4) tilation is that it does not cause gastric insuffl ation and the • Macintosh blades (1 to 4) resulting distention, impingement on thoracic expansion, and • Full set oral airways vomiting. However, there are some disadvantages to endotracheal |
• Full set nasal airways intubation. Endotracheal intubation bypasses the natural • Uncuffed endotracheal tubes (2.5 to 5.5) functions of the upper airways including fi ltration, warm- • Cuffed endotracheal tubes (5.0 to 10) ing, and humidifi cation. Complications of intubation include • 10 cc syringe (2) bleeding from the placement of the tube and from the manip- • Stylettes (adult and pediatric) ulation of soft tissues with the laryngoscope. Laryngospasm, • Elastic gum bougie (adult and pediatric) laryngeal swelling, mucosal necrosis and erosion, and vocal • Tape cord damage can all result from endotracheal intubation. In • Rescue device (King airway, LMA, etc.) addition, the direct connection from the ventilation device • Magill forceps (adult and pediatric) to the lungs increases the risk of barotrauma and ventilator- a ssociated pneumonia. Overventilation of the lungs can • Tube-securing device (adult and pediatric) impede venous return by increasing intrathoracic pressure, • Esophageal intubation detection device which can decrease the systemic blood pressure. However, • End-tidal carbon dioxide detector or adapters for capnometry/ prehospital endotracheal intubation occurs in the setting of capnography life-threatening diseases. If a patient requires intubation, then • Stethoscope the benefi ts far outweigh the risks. • Spare bulbs and batteries Although each different intubation technique necessi- • Extra PPE tates the use of a specifi c set of equipment, there are some fundamental pieces of equipment which are standard tools of the Paramedic. These include endotracheal tubes, laryn- goscope handles, laryngoscope blades, syringes, stylettes, gum bougie, continuous positive airway pressure (CPAP), endotracheal tube securing supplies, and Magill forceps and surgical airway management techniques—may also be (Figure 23-2, Table 23-1). In addition, endotracheal tube con- part of a Paramedic’s practice. Understanding the prepara- fi rmation equipment (stethoscopes, end-tidal carbon dioxide tion and use of these devices is critical for excellent airway monitors and detectors, and esophageal detection devices) management. and airway rescue devices (King airway, laryngeal mask air- ways, and esophageal tracheal Combitubes) should also be Endotracheal Tubes part of the Paramedic’s standard airway management equip- The basic tool of endotracheal intubation is the endotra- ment. Finally, some specialty devices—such as direct fi berop- cheal tube (Figure 23-3). The endotracheal tube provides tic intubation devices, direct visualization devices, the elastic a conduit for oxygenation and ventilation between the Intubating Airway Management 427 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. patient’s small fi nger or nare, or length-based tapes that give the Paramedic all of the appropriate sizes of equipment and drug doses. Although there is some evidence to suggest that length-based tapes are superior to other methods,2–4 it has been demonstrated that Paramedics can accurately determine weights of pediatric patients. Therefore, any method may be used as long as it is practiced and used consistently. Nasotracheal intubation, placing an endotracheal tube through the patient’s nostril and into the trachea, is another commonly used technique for managing a breath- ing patient’s airway. Blind nasotracheal intubation can only be performed on a breathing patient. While a standard endotracheal tube can be used for nasotracheal intubation, special tubes for nasal intubation are different in many ways from a standard oral endotracheal tube (Figure 23-4). Nasal tubes are softer and more pliable than standard tubes to allow them to curve more easily along the pos- Figure 23-3 Endotracheal tubes. terior oropharynx. Endotrol® tubes also have a small ring or “trigger” that, when pulled, decreases the radius of the tube’s curvature and curves the tip of the tube anteriorly. patient’s lungs and the ventilator (person or machine). The When compared to using standard endotracheal tubes for primary components of an endotracheal tube are the tube, nasotracheal intubation, “trigger tubes” increase the rates the cuff (on cuffed tubes), and the 15 mm adapter. The tube of successful intubation.5 acts as a gas conduit. The adapter allows the tube to be con- Once the Paramedic has selected the appropriate size and nected to a bag-valve-mask device or ventilator. The cuff style of endotracheal tube, the next matter is to check and (used on adult tubes) infl ates to secure the tube and to form prepare the tube. The Paramedic opens the tube packaging a tight seal below the level of the cords. Pediatric tubes are and places a small amount of lubricant at the distal end of the uncuffed because the pediatric trachea cones down in diam- tube. Although not a “sterile” technique, airway management eter below the cricoid ring, allowing the uncuffed tube to should at least be a “clean” technique. Efforts should be made seal itself there. However, cuffed endotracheal tubes can be to minimize contamination of the endotracheal tube. If the used in pediatric patients, particularly at the transition ages tube is cuffed, the Paramedic should place 5 to 10 cc of air in (ages 5 to 8). the cuff with a syringe and gently squeeze the cuff to assure There are some common features of all endotracheal that it is not leaking. tubes. The length of the tube is noted on the outside and is The syringe should be removed from the infl ation port measured in centimeters. These markings allow the Paramedic to assure that the valve is working and then reattached to to measure the depth to the end of the endotracheal tube. The aspirate the air from the cuff. The syringe should be fi lled distal end of an endotracheal tube is beveled. In addition, with 10 cc of air and left attached to the infl ation port so there is a “Murphy eye” on the distal right side of the tube. that it is ready and easy to fi nd at the time of intubation. The The Murphy eye improves ventilation to the right upper lobe 15 mm adapter should be assessed to make sure it is snugly and allows for some ventilation through the tube if the distal attached. For orotracheal intubation, a stylet (described in the end becomes occluded. following text) is placed and appropriately shaped, and the Endotracheal tubes are sized based on their internal prepared tube (still in its package) is placed within reach of diameter (I.D.). The smallest tube commonly used is the 2.5 the Paramedic at the patient’s side. mm I.D. tube, while the largest is the 11.0 mm I.D. tube. The well-prepared Paramedic recognizes that, although Endotracheal tubes increase in half-millimeter steps from 2.5 there are general size ETTs used for general “groups” (adult to 11.0 mm. Selection of the size of the endotracheal tube male, adult female, etc.), the availability of multiple sizes of for use with a given patient is made based on experience and endotracheal tubes (typically one smaller and one larger than the circumstances of the particular intubation. In general, an the expected size) allows the Paramedic to quickly use an adult male will be able to accommodate an 8.0 to 8.5 mm appropriately sized tube if the fi rst attempt was not success- tube while an adult female will accommodate a 7.5 to 8.0 mm ful due to endotracheal tube size. Some endotracheal tubes tube. However, patients with airway edema or trauma may are available preloaded with a stylet (“Slick Set®” Stylettes). require a smaller endotracheal tube. Regardless of how the Paramedic prepares for an inappropri- Sizing endotracheal tubes for pediatric patients can ately sized tube, it is important that she at least be aware that be done based on formulas that calculate an appropriate the fi rst ETT may not work and have a plan for what to do if size based on age,1 estimates based on the diameter of the that happens. 428 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Figure 23-4 Endotrol “trigger” endotracheal tube. The Laryngoscope The laryngoscope is the primary device used to visualize the larynx. Since its original design, the laryngoscope has under- gone a number of revisions to make it a more compact and self-contained device, affording improved visualization in some instances. Regardless of these changes, the basic prin- ciple remains the same: to allow direct visualization of the larynx. There are two major components of the laryngoscope: the handle and the blade. The handle serves as a power source (or power and light source in the case of fi beroptic laryn- goscopes) and grip point for the Paramedic. There are four Figure 23-5 Variety of handle sizes. common sizes of handles (Figure 23-5): large adult, adult, pediatric, and neonatal. One of the two adult sizes and a pediatric handle are the typical complement for an intuba- tion kit. The neonatal handles may be seen in the obstet- ric and neonatal transport setting. Although the handles are labeled adult and pediatric, perhaps the more important dif- ferentiation is the Paramedic’s hand size. A single laryngo- scope s ystem (standard versus fi beroptic and reusable versus disposable) should be used to prevent having incompatible blades and handles in a single kit. If this rule is followed, then all the handles should work with all of the blades in the set. A Paramedic with small hands may fi nd that using the pediat- ric handle with an adult blade is the best for him. Although there are multiple types of laryngoscopic blades available, the two most commonly used styles of blades are Figure 23-6 The two most common types of the Macintosh and Miller blades (Figure 23-6). Regardless laryngoscope blades are the Macintosh on the left of the type of blade, almost all blades in service are right and the Miller on the right. Intubating Airway Management 429 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. handed; that is, the laryngoscope is held in the left hand and children under 5, the epiglottis tends to be fl oppy and the the intubation is performed with the right hand. Although vallecular placement of the Macintosh blade does not pro- left-handed blades are available, unless the Paramedic plans vide suffi cient epiglottic control. The use of the Macintosh to purchase his own set, it is best to learn to use right-handed blade is described later. blades. Blades are designed to provide a view of the laryn- The Miller blade is a straight blade with common sizes geal opening through control of the tongue and the epiglottis. from 00 to 4. The small and curved fl ange is not designed The major differences between Macintosh and Miller blades, to displace the tongue in the same manner as the Macintosh refl ected in their design, are in the manner in which they con- blade (Figure 23-9). Rather, the straight blade is designed to trol the tongue and epiglottis. open a conduit to the larynx on the right side of the mouth The Macintosh blade is a curved blade with common and hold the tongue in the midline to the left side of the sizes from 1 to 4 (Figure 23-7). Its large fl ange and fl at sur- mouth. The tip of the blade is designed to capture and lift the faces refl ect a design to control the tongue. The tip of the epiglottis (Figure 23-10). This feature makes the Miller more blade is intended to fi t into the vallecula (Figure 23-8) and desirable for the child under 5 years of age. |
The 00 Miller is elevate the epiglottis via the hyoepiglottic ligament. Although designed for premature neonates. The use of the Miller blade not intended to do so, some Paramedics use the tip to directly is described later. hook the epiglottis and control it in that manner. Selecting the appropriate size and type of blade depends Although small (size 1) Macintosh blades are avail- on the patient’s size and the clinical context. Commonly, a able, they are typically not used in children under age 5. In chart (or, in pediatric patients, a color-coded tape) is used Figure 23-7 Macintosh blade. Figure 23-9 Miller blade. Epiglottis Vallecula Epiglottis Figure 23-8 Proper placement of the Figure 23-10 Proper placement of the Macintosh blade. Miller blade. 430 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. to select the appropriate-sized blade. As mentioned, Miller Murphy’s eye on the endotracheal tube to decrease the risk of blades are typically used for children under 5 years of age. the stylet injuring the airway. For patients older than 5, selection of the appropriate blade Although the use of a stylet is not mandatory, it is a use- depends upon the provider’s comfort level. There is a recom- ful adjunct that almost always makes intubation easier. There mendation to use a Miller blade in trauma patients because it are adult and pediatric sizes as well. A technique of nasal may provide a better view with less cervical spine manipu- intubation using a stylet has been described, although, gener- lation. However, the Paramedic must select the blade with ally speaking, nasal intubation is carried out without a stylet. which he is most comfortable, as he will have to use that However, for all oral intubations, the use of a stylet should be blade in high-stress situations. the rule, not the exception. Once the Paramedic has selected the correct blade, it is important to prepare and test the laryngoscope. The blade is Securing Devices attached to the crossbar of the laryngoscope’s handle until Once an endotracheal tube is placed, it is important it clicks into place. The blade is then rotated until the power that it be secured to keep it from moving out of the tra- points or fi beroptic channel are in contact with the oppo- chea. Numerous devices, such as the Thomas tube holder site points on the handle and the blade locks into the top (Figure 23-12), are available commercially. In addition, of the handle. At this point, the light should activate. The many other ties have been used and can be equally effec- light should be “white, tight, and steady bright”: white in tive. Regardless of the device or technique used to secure color (clean blade), the bulb tightly screwed into the blade the endotracheal tube, it is important that the endotracheal receptacle (not necessary in fi beroptic laryngoscopes), and tube not be able to move. Although taping the endotracheal steady and bright in intensity (good contact and good batter- tube to a patient’s face may be an acceptable practice in an ies). The laryngoscope should be turned with the blade down operating room setting where the patient is not moved during (the position of intubation) to assure that contact is main- the procedure, it is not suffi cient for the prehospital envi- tained in that position. Finally, the blade should be folded ronment. The risks of accidental tube dislodgment during back down on the handle to keep the batteries draining and patient movement are high. Not only is it important to secure the bulb from getting too hot (hot enough to burn the patient) the tube with an adequate device or technique, but it is also or burning out. important to place a cervical collar to minimize neck exten- sion and fl exion.6 However the Paramedic plans to secure the Stylet neck, it is important that the equipment be prepared prior to The stylet, a commonly used adjunct to oral intubation, pro- the intubation. vides rigidity to the endotracheal tube. Made of a malleable material such as copper or alumi- Secondary Confi rmation Equipment num, the stylet is a long, thin rod placed in the endotracheal Although the process of confi rming tube placement will tube to combat the inherent fl exibility of the ETT. By straight- be described later, it is important that the Paramedic ening the proximal three quarters of the stylet and bending prepare his equipment for tube placement confi rmation the lower quarter into a “hockey stick” shape (Figure 23-11), prior to beginning intubation. The three most commonly the tube can be shaped to maximize control of its distal tip accepted methods of confi rming endotracheal tube place- and improve the chances of successful placement. It is impor- ment in the prehospital environment are auscultation, tant that the distal end of the stylet not extend beyond the esophageal detection devices (EDD), and end-tidal carbon Figure 23-11 Stylet in place. Figure 23-12 Thomas tube holder. Intubating Airway Management 431 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. dioxide measurement. Visualization of the endotracheal fact, the tube is actually in the trachea. This can occur when tube p assing through the vocal cords, although valuable the tip of the tube is on the carina or pushed against the tra- and highly recommended, may not be possible due to other chea’s wall. In addition, in patients with limited functional factors (e.g., traumatic airway, use of a elastic gum bougie, residual capacity—such as those in CHF, adult respiratory or nasotracheal intubation). distress syndrome, or the morbidly obese—the devices may Auscultation of lung sounds, listening to the lung fi elds infl ate slowly or with resistance.11,13 Therefore, the devices with a stethoscope, is a commonly accepted technique for must be used in conjunction with other methods. To pre- assessing endotracheal tube placement. The only equipment pare the equipment, the Paramedic needs only to open the necessary for this is a stethoscope. Therefore, a stethoscope packaging. should be immediately available. Although auscultation of the End-tidal carbon dioxide (ETCO ) measurement and 2 axilla alone to detect esophageal intubation is only 85% sen- monitoring has become a standard method of both confi rm- sitive (and therefore misses 15% of esophageal intubations), ing endotracheal tube placement and monitoring patient status, the combination of auscultation over the epigastrium and in ventilation, and continuing tube placement.14 Carbon dioxide is the axilla, when sounds can be well heard, has been shown a colorless, odorless gas that is produced during cellular metab- to be 100% sensitive (detected all) for detecting esophageal olism. It is the primary exhaled waste product and its concen- intubation.7 tration in the exhaled respiratory gasses depends on adequacy Esophageal intubation detection devices should also of ventilation and circulation. End-tidal carbon dioxide mea- be used to confi rm endotracheal tube placement. Two major surement is used to assess endotracheal tube positioning and to styles of these devices exist: self-infl ating bulbs and syringe monitor the adequacy of ventilation. The three classes of end- style aspirators (Figure 23-13). These devices operate on the tidal carbon dioxide measurement are colorimetric measure- principle that the esophagus is composed of soft, fl oppy mus- ment, capnometry, and capnography. culature while the trachea is held open by rings of cartilage. End-tidal carbon dioxide monitoring, in all of its forms, Therefore, if suction is applied to an endotracheal tube placed has been demonstrated to be a reliable and highly sensi- in the esophagus, the walls of the esophagus will collapse on tive method for assessing endotracheal tube placement and the tip and prevent infl ation. Conversely, the trachea will be monitoring tube placement over time.15–19 End-tidal carbon held open by cartilaginous rings. Therefore, the esophageal dioxide monitoring has become the gold standard of con- intubation detection device should infl ate rapidly and com- fi rming endotracheal tube placement. There are, however, pletely with air. conditions which can limit its reliability. Therefore, it is A number of studies have been performed on both the important to understand their impact on the use of these syringe type and self-infl ating bulb devices. The results are devices. Perhaps the most fundamental limit is that the encouraging for its use. In several studies,8–11 all of the esoph- patient must be producing carbon dioxide in order to exhale ageal intubations were detected. Although there are reports it. In patients in cardiac arrest, the lack of exhaled carbon of the devices failing to detect esophageal intubations in dioxide may be mistaken for an esophageal intubation.20 Of patients with massive gastric insuffl ations,12 this has not been much more c oncern, however, is the risk of mistaking an seen universally. The greatest limitation seems to be that the esophageal intubation for a tracheal intubation. Bag-mask devices will often indicate an esophageal intubation when, in assembly ventilation with gastric insuffl ations,21 ingestion of c arbonated beverages and antacids,22 and hypopharyn- geal endotracheal tube placement23 have all been shown to produce waveforms that would indicate tracheal intubation. However, with the exception of hypopharyngeal placement, after six ventilations (approximately 30 to 60 seconds of ventilation), the waveforms diminish and eventually vanish. Therefore, end-tidal carbon dioxide measurements should always be accompanied by other methods of assessing endo- tracheal tube placement. The least expensive, and probably most commonly used, device for measuring end-tidal carbon dioxide is the colorimetric device (Figure 23-14). These devices are simply encapsulated pieces of litmus paper over which the exhaled breath fl ows. When carbon dioxide is in the pres- ence of water, it forms carbonic acid; the pH sensitive lit- mus paper in the colorimetric device detects this acid and changes color. These devices are as reliable as infrared cap- nometry and capnography for detecting esophageal and tra- cheal intubations20 and are reliable in infants and children Figure 23-13 Esophageal detector devices. larger than 15 kg.24 The devices are designed to be attached 432 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. usually considerably less expensive than capnography devices although they are also much more expensive than disposable colorimetric caps. Most of these devices have a numerical as well as a bar graph display. Although they do not display trends over time nor show a graph of the exhalation curve, if the Paramedic records the peak ETCO over time it is possible 2 to collect trending data. In addition, these devices are usually equipped with an apnea alarm and can alert the Paramedic to sudden changes in ventilatory function. Preparation of the equipment for use involves assuring that there is suffi cient power. For a mainstream device, the probe must be attached to the monitor and an adapter that connects to the endotra- cheal tube (or alternative airway device) which should be attached to the probe. Sidestream and microstream monitors Figure 23-14 Colorimetric end-tidal carbon will have an adapter with a sampling tube that attaches to the dioxide detector. exhalation stream. End-tidal capnography gives the most information to the Paramedic. While numeric values for peak and trough between the 15 mm adapter on the endotracheal tube or an ETCO levels are displayed, the monitor also displays a graph 2 alternative airway device and the BVM. Some manufactur- of the exhalation |
curve (Figure 23-15). This graph allows for ers produce bag-mask assemblies with colorimetric ETCO 2 trending over time; demonstration of changes associated with devices built into the exhalation valves. When CO is < 0.5%, 2 complications such as displaced, kinked, and occluded tubes; the paper is purple. When the CO is between 0.5% and 2 and respiratory mechanics.19 Capnography monitors are by 2.0% of the exhaled gas, the paper becomes tan. Finally, far the most expensive, although they are often integrated when the exhaled CO is > 2%, the paper turns yellow. Over 2 into other multifunction devices such as cardiac monitors. time (approximately two hours for most in-line devices), the Preparation of these devices for use, as with the capnometer, paper turns permanently yellow. Exposure to water, vomit, depends on whether the capnographer is a mainstream or pulmonary secretions, medications, and so on, will hasten sidestream/microstream device. the deactivation of the device. Preparation of the colori- metric end-tidal CO monitor involves simply opening the Rescue Devices 2 packaging. For a patient requiring airway and ventilatory assistance, the The remaining two classes of monitoring—capnometry ideal situation is placement of an endotracheal tube. However, and capnography—are, outside of the operating room, based there will always be scenarios in which endotracheal intuba- on infrared analysis of exhaled gasses. By shooting an infrared tion will not be possible. A review of the airway management beam through a sample of exhaled gas, it is possible to measure algorithm clearly demonstrates that, after a third failed endo- the amount of CO in the sample based on the absorption of 2 tracheal intubation attempt, the Paramedic should strongly light in the correct wavelength. The infrared beam and sensor consider another approach to airway management. One class can either be attached directly to the gas exhaust stream, called of rescue devices available are placed blindly and provide mainstream or in-line monitoring, or can be housed in a device an airway that is superior to face-mask ventilation, yet not that takes a small sample from the exhaled gasses, called side- as protective as an endotracheal tube. These devices are col- stream or microstream monitoring. lectively called supraglottic airway devices or blind inser- Although mainstream measurements have the advantage tion airway devices (BIADs). The most common supraglottic of being instantaneous, the probes are more vulnerable to devices are the King LTS-D airway, the esophageal tracheal breakage and are more expensive. Sidestream devices protect Combitube (ETC or Combitube), and the laryngeal mask air- the infrared sensors, but they have a delay in measuring due way (LMA). Although the esophageal obturator airway (EOA) to the distance the gas sample must travel from the exhalation to the sample chamber. Microstream devices have less of a delay than standard 40 sidestream devices. Microstream devices may also be better suited for use in pediatric patients with very small tidal vol- umes than standard sidestream devices or bulky mainstream devices that can kink an endotracheal tube.25 Regardless of the sampling system, however, the data interpretation and display methods differentiate between capnometry and capnography. 0 Devices that perform capnometry give a single, numeric peak reading of the exhaled CO . These monitors are 2 Figure 23-15 Capnography waveform. Intubating Airway Management 433 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. mmHg and esophageal gastric tube airway (EGTA) were commonly operating room. Introduced in the mid-1980s, this device was used before the advent of the supraglottic airways, the need designed to be used in situations where face-mask ventila- to maintain an adequate mask seal and inability to protect the tion was inappropriate but the invasiveness of endotracheal trachea have decreased the use of the EOA and EGTA. intubation was not necessary.26 Although not originally The King LTS-D airway (Figure 23-16) is one example of designed as a “diffi cult airway” or “rescue” device, its poten- a supraglottic airway. It is designed to be placed in the esopha- tial was recognized early on. In the pilot study on its use, gus and seal off the pharynx and esophagus with two balloons two of the patients were classifi ed as having potentially dif- fi lled through a single port. A standard BVM adapter at the fi cult airways.27 Subsequent studies and clinical experience end of the device is used to ventilate the patient via small holes have demonstrated that the LMA adequately fi lls the role of located between the balloons. A channel located in the ante- a blind insertion airway rescue device in emergency airway rior between the two balloons allows the use of an elastic gum management.28 Furthermore, introduction of devices such as bougie or endotracheal tube exchanger to replace the device the intubating LMA (ILMA) and disposable LMAs (LMA with a standard endotracheal tube. Finally, a posterior lumen Unique®) have expanded the role of the LMA in prehospital allows for passage of a nasogastric tube into the stomach once airway management.29,30 the King airway is in place, allowing stomach decompression. The laryngeal mask airway, in essence, moves the mask Due to the ease of use, this device is becoming popular in the of face-mask ventilation from the face to the opening of the prehospital community. larynx. The LMA is composed of a single lumen tube with a The laryngeal mask airway (Figure 23-17), a blind standard 15 mm adapter at the proximal end and an infl atable rescue airway device, was originally designed for use in the mask at the distal end. The mask is designed to cover the open- ing of the larynx and, with the mask infl ated, provide a seal. The intubating LMA, in addition to placing the mask over the larynx, is designed to pass an endotracheal tube through the lumen and direct it into the trachea. The LMA Unique®, as a disposable device, is most likely to be used in the prehospital environment. The LMA does require some preparation before use. Once it is removed from the package, the mask should be infl ated to assure that it holds air. The LMA mask must then be pressed against a fi rm surface and the air aspirated from the mask. This causes the rim of the mask to fold backwards and allows for easier placement. Finally, the distal tip of the mask should be lubricated to improve ease of placement. The design of the esophageal-tracheal Combitube (ETC) (Figure 23-18) refl ects a response to the complica- tions associated with the esophageal obturator airway (EOA) and the esophageal-gastric tube airway (EGTA). Like the Figure 23-16 King LTS-D airway. Figure 23-17 Larnygeal mask airway. Figure 23-18 Esophageal-tracheal Combitube. 434 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. EOA and EGTA, the ETC is placed into the esophagus; how- King airway is not designed to be used if placed in the tra- ever, tracheal placement of the ETC is possible. The double- chea. If tracheal placement of the King airway is suspected, lumen design allows for endotracheal as well as esophageal immediately remove the device. intubation. Preparation of these devices is similar to that of an endo- The Combitube is a double-lumen device with two sepa- tracheal tube. They must be removed from their packages rate and distinct lumens, a proximal and distal lumen named and the cuffs infl ated to test their integrity and the function- by where they exit from the tube. Each lumen has a standard ing of the valves. For the King airway and Combitube, this is 15 mm connector at the proximal end to allow attachment to done with the syringes that are prepackaged with the device. a ventilation device. Each has two cuffs: a large proximal cuff The distal end of the tube should be lubricated with a water- designed to seal the hypopharyngeal portion of the airway soluble lubricant and the devices returned to the packaging. and a smaller distal cuff designed to seal the esophagus or trachea, depending on the placement. Elastic Gum Bougie There are several advantages and disadvantages to In those situations where intubation is diffi cult due to patient the use of supraglottic airway devices. Since they can be anatomy, often it is only possible to visualize the posterior passed blindly, no special equipment is needed other than arytenoids. Although any tube that passes anterior to the the device itself. The Combitube has been demonstrated to arytenoids will be passing through the larynx, it is often dif- cause less C-spine movement than conventional endotra- fi cult to physically place the tube in that location. A small cheal intubation,31 which may be clinically signifi cant in the diameter, semi-rigid device that would be easier to place patient with known or suspected C-spine injury. The devices would assist with intubation. The elastic gum bougie and are easy to place and have success rates of almost 100%.32 several similar devices meet that need. Placement is easier with these devices than with standard First introduced in 1949, the elastic gum bougie, or sim- intubation when patients are in unusual positions.33 There are, ply gum bougie, appears at fi rst glance to simply be a very however, multiple disadvantages to these devices. The King long stylet34 (Figure 23-19). However, it is somewhat larger airway and Combitube are currently only available for adult in diameter, is made entirely of wound gum rubber, and has patients. They must be inserted orally and, when placed in a hard, smooth, and round plastic tip. The device is directed the esophagus, are diffi cult to intubate around, owing to their through the vocal cords and into the trachea to serve as a large size and rigidity. Furthermore, caustic ingestions and guide for an endotracheal tube. The distal end is designed to known esophageal trauma or disease are contraindications minimize the chance of trauma to the larynx. Furthermore, the to use of these devices. Finally, they are considerably more small plastic “button” at the end “clicks” as it passes over tra- expensive than standard endotracheal tubes. cheal rings, giving the user feedback about placement. Once Both devices are intended for esophageal placement, the device has been placed, the endotracheal tube is threaded which occurs approximately 90% to 99% of the time. In the over the proximal end and advanced into the trachea. It has esophageal position, the distal cuff seals the esophagus while been shown to improve intubation rates in diffi cult airway the proximal cuff seals the hypopharynx. The proximal lumen situations.35–37 ventilates through a number of small holes between these There are multiple variants on the elastic gum bou- two cuffs. Since the opening to the larynx lies between these gie including plastic bougies,38 large-diameter feeding cuffs, ventilatory gasses passing through the proximal lumen tubes, and endotracheal tube exchanges. This last class can only go into the larynx and subsequently to the lungs. is of interest because some manufacturers make devices There are some limitations to the esophageal placement. Most importantly, epiglottic, perilaryngeal, and laryngeal injury or deformity (burns, trauma, edema, etc.) can prevent effective ventilation. Furthermore, respiratory secretions and bleeding between the two cuffs will be aspirated. Finally, medication administration and deep suctioning of the lungs are not pos- sible with esophageal placement. It is possible to obtain endotracheal placement of the Combitube. Anecdotally, increased rates of tracheal place- ment occur with well-performed cricoid pressure. When the devices are placed in the trachea, the distal cuff serves to seal the trachea (like the cuff of an endotracheal tube) while the proximal cuff helps stabilize the device. Ventilation is per- formed through the distal lumen that opens at the end of the tube, distal to |
the smaller cuff. Tracheal placement allows the device to function as an endotracheal tube and all procedures and medications normally performed with an endotracheal tube can be performed with the Combitube. In contrast, the Figure 23-19 Elastic gum bougie. Intubating Airway Management 435 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. through which a patient can be ventilated. All of these be placed in the endotracheal tube with the distal end of the devices are used similarly to the elastic gum bougie. There stylet 1 to 2 cm inside the distal end of the endotracheal tube. is no preparation of the devices other than to remove them The stylet is then bent into a “J” and the whole device placed from their packaging. If a disposable tube exchanger is aside for use. packaged in a bent-in-half position, the bend should be straightened as this will improve control of the device and Surgical Airways help thread the tube. One of the other advantages of the trachea’s close proximity to the anterior neck is that surgical airway management can Lighted Stylettes/Translaryngeal be achieved rapidly and effectively. There are three common Illumination Intubation variants on the technique. The fi rst is the classical surgical Due to the close proximity of the trachea to the anterior sur- cricothyroidotomy, a surgical procedure to gain entry to the face of the neck, it is possible to visualize light on the ante- trachea through the anterior neck. The other two techniques rior neck if a bright light source is placed on the trachea. are the needle and percutaneous cricothyrotomy techniques. Lighted stylettes (Figure 23-20) are, essentially, malleable Many manufacturers produce percutaneous cricothyro- stylettes with a bright light source at the distal end and a tomy kits that enable the placement of a single lumen tube power source at the proximal end. When placed in the tra- either similar to a large IV catheter or to a tracheostomy chea, a bright, well-circumscribed light is seen in the midline tube. The preparation and use of these kits is highly specifi c of the trachea. Placement in either pyriform fossa results in to the manufacturer and will only be discussed in general a light off the midline while esophageal placement results in terms. It is important to note that a surgical airway should be a diffuse, dim glow. performed only if that patient cannot be intubated, a rescue There are advantages and disadvantages to the use of device cannot be placed, and the patient cannot be ventilated lighted stylettes. Although the lighted stylettes were designed with standard face-mask techniques. The only exception to for use as adjuncts to standard orotracheal intubation,39 sub- the last requirement is if a patient can be ventilated with a sequent work has demonstrated their effi cacy as an alter- face-mask technique but the situation (prolonged transport, native to laryngoscopic intubation.40,41 Lighted stylettes can diffi cult extrication, or circumstances that would make surgi- be placed while the Paramedic is positioned either above a cal airway placement diffi cult at a later time) requires a more patient’s head or while the Paramedic is positioned along- secure airway. side the patient. They minimize C-spine movement and Opening a true or classical surgical airway is a relatively are therefore excellent devices for management of trauma simple process that involves the identifi cation of the crico- airways. thyroid membrane, cutting a hole through the cricothyroid There are a few disadvantages to the use of lighted membrane, and placing an endotracheal tube or cuffed tra- stylettes. If a patient has a very large neck, it may be impos- cheostomy through that hole. The process has been used suc- sible to differentiate between esophageal and tracheal cessfully in a number of prehospital systems and provides an placement. Bright lighting or sunlight may make visualiza- effective method of obtaining airway control when standard tion of the neck on the anterior neck diffi cult. Finally, there orotracheal intubation and rescue device utilization have is some evidence that lighted stylettes may cause laryngeal failed.43 There are complications associated with the proce- injury.42 dure. These include bleeding, carotid artery and jugular vein The lighted stylet should be removed from its package. injury, thyroid injury, accidental tracheostomy, pneumotho- Preparation for use is dependent on the manufacturer, but rax, mediastinal intubation, and esophageal perforation and there are some universal preparations. The device should be intubation.44 The procedure is contraindicated in patients turned on to test the batteries and the stylet portion should under the age of 12, with needle cricothyroidotomy being the procedure of choice for these patients, and in patients without recognizable anatomic landmarks. Extreme caution is needed in patients with neck injuries; if a hematoma has formed from a vascular injury, accidental decompression of the hematoma can make airway and bleeding control impos- sible. The hematoma may also obscure landmarks or devi- ate the trachea to one side, increasing the diffi culty of the procedure. Little equipment is needed for a surgical airway. A scalpel, a tracheal hook, and a 6.0 or 6.5 endotracheal tube or tracheostomy tube are all that are needed. The endotra- cheal tube should be prepared as described previously and the scalpel and hemostats should be removed from their Figure 23-20 Lighted stylet. packaging. 436 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Needle cricothyrotomy, also known as translaryngeal prepare for a needle cricothyrotomy, the IV catheter should cannula ventilation and/or transtracheal jet ventilation be removed from its packaging and attached to the syringe. (TTJV)—ventilation of the lungs using special high-pressure This will not work with safety catheters. If a safety cath- devices—is a commonly taught and performed technique for eter is being used, the syringe is not used. The TTJV device emergent oxygenation.45 In this technique, a large bore IV should be attached to the oxygen regulator if it is not already. catheter (12 to 16 gauge) is placed through the cricothyroid The oxygen should then be turned on and the device acti- membrane and a high pressure (50 PSI) oxygen source deliv- vated to assure that the control valve works properly and does ers oxygen to the lungs. As with the other surgical techniques, not stick. translaryngeal cannula ventilation is only indicated if less There are a number of different manufacturers of percu- invasive techniques have failed. taneous cricothyrotomy kits. Each device and technique has There are some important contraindications to this tech- advantages and disadvantages, so it is important to obtain nique. The equipment and technique rely on high pressure samples of each device and test them before adopting any to move a large volume of oxygen through a small device. specifi c device. Many have multiple parts that are easily lost Exhaust valves are not built into the device and therefore all in the uncontrolled prehospital environment. Others require exhalation must occur through the patient’s own upper airway. fi ne motor dexterity to utilize. If the patient has a complete airway obstruction (inspiratory It is best to choose a device that is simple to use, has a and expiratory), high-pressure ventilation without escape of minimal number of parts that can be lost, and is easily stored gasses results in overpressurization injuries. and adapted to equipment already being used. Past teaching stated that this technique provides only a method of oxygenation and that there is no ventilation (carbon dioxide exhalation). However, a number of animal studies46,47 Patient Preparation and human studies48,49 have demonstrated normal, and even Once the decision to intubate has been made and the appro- low (overventilation), carbon dioxide levels if a fl ow rate of priate equipment has been prepared, the next step is to pre- 1,600 mL/sec (the fl ow rate through a 21 gauge catheter with pare the patient for intubation. Preparing the patient occurs a 50 PSI oxygen source) is used. Therefore, transtracheal jet in three ways: assessment of the patient, positioning of the ventilation with appropriate equipment is a valid method of patient, and, if needed, medication administration. oxygenating and ventilating a patient in whom an airway can- It is important to assess all patients before undertaking not otherwise be established. an intubation (or any airway management). There are a num- The equipment for needle cricothyrotomy consists of a ber of anatomic features that may suggest diffi culty will be large bore IV catheter (12 to 16 gauge), a 5 to 10 cc syringe, encountered during the airway management. Although the and a high pressure (50 PSI) oxygen source. Although various presence or absence of the characteristics will not change methods of ventilating through a needle catheter have been the need to manage the airway, they do infl uence decisions described, including syringe to BVM adapters44 and oxygen such as the use of medications for sedation and paralysis as tubing with a small hole cut in the side to control “on” and well as optimal patient positioning and equipment selection. “off ”,45 many commercial TTJV devices are available and are Therefore, the Paramedic should assess all patients before the best choice for this technique (Figure 23-21). attempting airway management. These devices attach to the high pressure output ports of Several studies have looked at the problem of anticipated standard oxygen regulators either by screwing onto the regu- and unanticipated diffi cult airways.50–54 Several factors have lator or via a previously attached quick-connect device. To been identifi ed as predictors for diffi cult airway management and/or diffi cult tracheal intubation (Table 23-2). Although some of these characteristics cannot be eas- ily identifi ed before the intubation (i.e., a fl oppy epiglottis), others can and have led to mnemonics and memory aids for anticipating a diffi cult airway. Two of the most useful are the 3-3-2 rule and the LEMON law, both developed as part of the National Emergency Airway Course.55 The 3-3-2 rule is a simple method for rapidly evaluat- ing a patient’s anatomy. In an “easy” airway, the Paramedic should be able to: ■ Place three fi ngers between the tip of the chin and the hyoid bone ■ Place three fi ngers between the upper and lower teeth at the maximal mouth opening ■ Place two fi ngers between the thyroid notch and the Figure 23-21 Transtracheal jet ventilation. fl oor of the mouth Intubating Airway Management 437 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Table 23-2 Diffi cult Intubation Conditions The LEMON law similarly provides a rapid mnemonic for evaluating a patient. The elements of the LEMON law • Male gender are to: • Obesity ■ L—Look externally for anything that will hinder • Age between 40 to 59 ventilation or intubation • Decreased mouth opening ■ E—Evaluate the 3-3-2 rule to assess the airway anatomy • Shortened thyromental distance ■ M—Mallampati classifi cation (Figure 23-22) • Poor visualization of the hypopharynx ■ O—Obstruction, either new or chronic, should be • Limited neck extension evaluated • Receding chin ■ N—Neck mobility should be determined if not • Abnormal dentition contraindicated (contraindicated in suspected C-spine • Large tongue injury) • Beards These two rules, if applied to every patient, should help • Supraglottic mass to predict a diffi cult airway and help the Paramedic to pre- • Floppy epiglottis pare accordingly. |
Of these guidelines, the Mallampati score • Trauma patient is the most diffi cult to determine in the fi eld. The score is most accurate when the patient is assessed in a seated posi- • Pregnant patient tion, opens her mouth, and sticks out her tongue. This is • Mallampati score > 2 (Figure 23-22) not practical for most patients requiring prehospital airway management. Positioning the patient is one of the most critical steps in improving the rates of successful fi rst intubation attempts. Although every intubation attempt should be a best attempt, in the emergent setting of prehospital intubations the fi rst attempt is often made from the position in which a patient is found. Unfortunately, each attempt at intubation increases edema and bleeding in the airway, making subsequent attempts more diffi cult. Therefore, although the temptation exists to “just get a tube in,” the reality is that without forethought, a diffi cult airway can be made into an impossible-to-intubate- or-ventilate airway. Although intrinsic issues such as suspected cervical spine trauma may preclude optimal patient positioning, in most other cases some simple interventions can properly position a patient for intubation. The ideal position, described by Chevalier Jackson in 1913, is the “sniffi ng” position56 Class l: soft palate, uvula, Class ll: soft palate, fauces, pillars visible uvula, fauces visible (Figure 23-23). No difficulty No difficulty Class lll: soft palate, Class lV: hard palate base of uvula visible only visible Moderate difficulty Severe difficulty Figure 23-22 Mallampati classifi cation. Figure 23-23 Sniffi ng position. 438 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Bannister and MacBeth, in 1944, clarifi ed the posi- require less force for glottic visualization.61 The use of this tion as one in which the oral axis, the pharyngeal axis, and position is contraindicated in suspected cervical spine or the laryngeal axis are all aligned through fl exion of the back injuries. neck to 30 degrees and extension of the head on the atlanto- In trauma patients, the issue of positioning becomes occipital joint.57 more diffi cult. Clearly, neck fl exion and head extension are Although there is some research to suggest that simple contraindicated. However, anterior displacement of the jaw head extension, which is obtained in a “head-tilt, chin-lift” via a modifi ed jaw thrust partially mimics head extension. In maneuver (Figure 23-24), may be as effective as the sniffi ng addition, proper application of backward, upward, and right- position in providing a good laryngoscopic view,58 this has ward pressure (the BURP technique discussed later in this not been validated.59 Therefore, for anatomical and theoreti- chapter) may improve the view. Finally, having an assistant cal reasons, the sniffi ng position is considered to be the posi- open the cervical collar and provide in-line stabilization from tion of choice for patient positioning during intubation.60 the inferior direction will allow greater mobility of the jaw. At the time of intubation, most patients will already be All of these techniques substitute for ideal positioning in the in the “head-tilt, chin-lift position” commonly used for face- trauma patient. mask ventilation. This position places the head in extension The fi nal step in patient preparation is the appropriate use along the atlanto-occipital joints, bringing the pharyngeal of sedatives and paralytic agents. A full discussion of these and laryngeal axes—but not the oral axis—into alignment. agents, as well as the techniques of medication facilitated and By lifting the head anteriorly approximately 7 cm, the neck is rapid sequence intubation, can be found in Chapter 24. fl exed to 30 degrees and the oral, pharyngeal, and laryngeal axes are brought into alignment. This alignment allows for Oral Endotracheal Intubation the best view during intubation. It is important to note that it may be diffi cult to obtain Once the equipment and patient have been prepared, it is time neck fl exion in obese patients or patients with very short to perform the intubation. The vast majority of intubations are necks. Sitting these patients upright can “create” a neck performed via the oral route and it is therefore likely to be the and change a diffi cult intubation into a relatively easy intu- fi rst technique the Paramedic performs on a given patient. The bation. This position can be obtained by sitting the patient process can be broken down into four important steps: visualiz- upright on a chair, packing multiple blankets underneath his ing the vocal cords, passing the endotracheal tube, confi rming shoulders and back, or positioning the stretcher at a 50 to endotracheal tube placement, and securing the endotracheal 70 degree angle and placing a folded blanket or towel behind tube. Mastery of each of these steps increases the chances of a the head. successful intubation. The head elevated laryngoscopic position (HELP) is It is important to note that endotracheal intubation is a a patient position that places the head in extension along team activity. Although Paramedics often fi nd themselves the atlanto-occipital joints, bringing the pharyngeal, laryn- with minimal assistance, it is important that all available geal, and oral axes into alignment using an elevation pillow. resources be used effectively. There should be at least two It can also be used in patients who are unable to lay fl at team members performing the intubation—the Paramedic (i.e., CHF patients or morbidly obese patients) or to help and an assistant. It is the assistant’s job to check and assemble clear secretions. In addition, patients in the HELP position equipment, assist in preparing the patient, and then provide extra hands during the intubation. The two common tasks of the assistant are handing equipment to the intubator and providing digital pressure to the upper airway during the intubation. There are three ways in which the assistant can provide digital airway pressure. The fi rst technique, cricoid pressure maneuver, applies 10 pounds of backward pressure on the cri- coid ring. This pressure minimizes the risk of passive regurgi- tation. Unfortunately, cricoid pressure maneuver may worsen the laryngoscopic view of the tracheal opening. In addition, often the pressure is mistakenly applied to the thyroid carti- lage. Thyroid pressure not only does not seal the esophagus (the thyroid cartilage is an incomplete ring posteriorly) but it does not improve the laryngoscopic view; in fact, it often tips the vocal cords even more anteriorly, making them more diffi cult to see. A superior method to improve laryngoscopic view is backward, upward, and rightward pressure (the BURP tech- Figure 23-24 Head-tilt, chin-lift position. nique62). Finally, if the Paramedic is performing two-handed Intubating Airway Management 439 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. laryngoscopy or external laryngeal manipulation, the assis- the epiglottis anteriorly and reveals the vocal cords. It is also tant may be asked to hold the larynx in the position that pro- possible for the tip of the Macintosh blade to capture the epi- vides the Paramedic the best view of the vocal cords. glottis in the same manner as the Miller blade. If this happens and the vocal cords are visualized, do not move the blade. If, Visualizing the Vocal Cords however, the blade obscures the view of the vocal cords then it needs to be repositioned in the vallecula. To visualize the vocal cords, the Paramedic must use the laryn- The Miller blade is designed to pin the epiglottis against goscope to provide lighting and a direct line of sight through the base of the tongue anteriorly and provide a straight-on the mouth to the larynx. Although there are differences in view of the vocal cords. The Paramedic should therefore see technique between the two most commonly used blades—the the tip of the blade slide posteriorly to the epiglottis and, when Macintosh (curved) and Miller (straight) blade—there are the blade is lifted anteriorly and inferiorly, the tip should lift many similarities as well. up the epiglottis to reveal the vocal cords. It is important to The patient’s mouth must fi rst be opened. If the patient note that since the Miller blade provides less displacement of was already receiving face-mask ventilation, an oropharyn- the tongue, the view is more likely to be down the right side geal airway will probably already be in place. If this is the of the mouth as opposed to down the midline, as is the case case, it should be removed while the head and jaw are held with a Macintosh blade. still to maintain an open airway. If the mouth has not already Obtaining a view of the vocal cords is often the most dif- been opened, a crossed fi nger technique using the thumb on fi cult part of the intubation. Once the Paramedic has begun the lower teeth and the index fi nger on the upper teeth should the intubation, it is important to assess the degree of diffi culty be used. Once the airway is opened, the laryngoscope, held in seeing the cords. Although a simple “easy” or “diffi cult” in the left hand, is inserted in the right side of the mouth, lat- system can be used, there are quantitative measures. The most eral to the tongue. The laryngoscope should be held with the commonly used is the Cormack-Lehane grading system tips of the fi ngers and the thumb as the procedure is one of (Figure 23-25). skill and fi nesse, not brute force. The laryngoscope is swept The system grades the view of the glottic opening by how to the midline. In the case of the Macintosh blade, the large much is occluded by the tongue—Grade I is a clear view of fl ange should completely displace the tongue to the left and the entire glottic opening whereas IV is visualization of the the blade can be moved slightly past the midline. The Miller tongue or soft palate only. Proper patient position and exter- blade will not completely displace the tongue and should nal laryngeal manipulation, described later, can improve the therefore be swept no further than the midline. Once this has view by one to two grades. been done, the Paramedic should have a clear view of the oropharynx. The tip of the laryngoscope is advanced under direct visualization. Once the epiglottis is identifi ed, the blade tip is appropriately placed and the whole laryngoscope is pushed anteriorly and laterally, essentially lifting the man- dible away from the pharynx and larynx at a 45-degree angle to the body. The direction of movement should be like aim- ing for the junction of the ceiling and wall on the opposite side of the room. This anterior and lateral lifting prevents the Paramedic from tilting the handle superiorly and damaging the upper teeth. At this point, the laryngeal structures should be visible. The paraglossal approach to intubation involves insert- ing the entire length of the laryngoscope blade blindly into Grade 1 Grade 3 the esophagus and then slowly withdrawing the blade under direct visualization.63,64 When using this method, both curved and straight blades are used to capture and lift the epiglottis. Although there is no evidence to support this method or the methods described in the following text, there is anecdotal evidence that this method can be performed consistently and is less traumatic than other methods. The tip of the Macintosh blade is designed to fi t into the vallecula. Therefore, the Paramedic should see the tip of the blade slip between the tongue anteriorly and the epiglottis Grade 2 Grade 4 posteriorly. When the blade is lifted anteriorly and laterally, the tip pulls on the hyoepiglottic ligament, which in turn pulls Figure 23-25 Cormack-Lehane grading system. 440 |
Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Aside from patient positioning there are several techniques the Paramedic should attempt to move it with Magill forceps that can be performed once the laryngoscope is in place. Two (Figure 23-27). The attempts should be made under direct of the most effective are external laryngeal manipulation visualization to avoid pushing the foreign body further into (“two-handed laryngoscopy”) and retraction of the right cor- the airway. If the foreign body is subglottic and cannot be ner of the mouth. These two techniques improve visualization grasped with the Magill forceps, it should be pushed into a of the glottic opening. External laryngeal manipulation has mainstem bronchus with an endotracheal tube and the tube been well described in the ear-nose-and-throat65,66 and airway withdrawn to above the carina to allow at least one lung to be management literature.67, 68 In this technique, the Paramedic ventilated. performs direct laryngoscopy with his left hand while manip- ulating the larynx with his right hand (Figure 23-26). Once he has an improved view of the glottic opening, the Paramedic Street Smart has an assistant take over the external laryngeal manipula- tion, holding the larynx absolutely still. Alternately, the assistant may place his hand on the cricoid The tips of the Magill forceps, due to their shape, cartilage while the Paramedic grasps and guides the assistant’s grip best on smaller and irregularly shaped objects. hand with his right hand. In this variant, once the proper posi- Large, smooth objects are almost impossible to grasp tioning is attained, the assistant already has his hand in the cor- and may require pinning the object between the rect position. External laryngeal manipulation greatly improves successful glottic visualization. Magill forceps and the suction catheter to lift it. Often it is diffi cult to see past the lips. Having an assistant hook the right corner of the mouth with a fi nger and retract the corner of the mouth may provide a suffi cient opening to Ambient light may also make visualization of the glot- allow visualization of the glottic opening. It is important that tis diffi cult. Very bright light can “wash out” the structures the assistant’s fi nger not be placed between the teeth in the and cause refl ections off of secretions that make landmark event the patient has a seizure, suffers a muscle spasm, or identifi cation impossible. Turning lights down or off while decides to bite. This technique is particularly useful in the inside a building or in the back of an ambulance can make patient with large cheeks, lips, or a large, diffi cult-to-control visualization much easier. If it is impossible to decrease the tongue. ambient light, placing a large sheet or blanket—or fl ipping a Foreign bodies and body fl uids such as mucus or vomit coat—over the Paramedic’s and patient’s heads should prove can make visualization of the glottic opening diffi cult. If suc- adequate shade to allow better visualization. tioning is required, a rigid suction catheter should be used. No more than 15 seconds of suction should be applied and Passing the Endotracheal Tube the suctioning should be performed under direct laryngos- Once the glottis has been visualized, the next step is pass- copy. By suctioning with visualization, airway and soft-tissue ing the endotracheal tube through the vocal cords. The tube trauma is minimized. If a large foreign body is encountered, should either be in a location where the Paramedic can fi nd Figure 23-26 External laryngeal manipulation. Figure 23-27 Magill forceps. Intubating Airway Management 441 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. it without looking away from the vocal cords, or the assistant should hand the tube to the Paramedic, since looking away increases the risk of movement and the need to revisualize the glottic opening. The tube is grasped in the right hand and introduced from the right side of the mouth. It is often easiest to place the tube in the mouth sideways with the inside of the curve toward the right side of the mouth so the Paramedic can watch the tip move toward the cords without the rest of the tube obstructing his view. Once the tip of the tube is at the level of the vocal cords, the tube should be rotated counterclockwise 90 degrees so that the curve of the tube is in the same direction as the curve of the airway. The tube is advanced through the cords under direct visualization until the cuff is 2 to 3 cm below the cords or, in pediatrics, the cords lie between the two black rings. (a) If the cords are closed, as occurs with laryngospasm, or only partially open, it will be diffi cult to advance the tube. In the case of laryngospasm, gentle pressure of the lip of the tube bevel between the cords may cause them to relax suf- fi ciently to pass the tube. The Paramedic should not “force” the tube or the stylet between the cords. If this does not work, alternative approaches (e.g., a surgical airway) may be nec- essary. If the cords are partially open, placing the tip of the tube into the space between the cords and applying gentle pressure may allow the tube to advance. Again, the Paramedic should not force the tube. Gently turning the tube clockwise and counterclockwise may also allow it to advance. Finally, having the assistant remove the stylet while the tip of the tube gently presses against the vocal cords may give the tube enough fl exibility to advance. (b) Once the endotracheal tube has passed between the cords, the Paramedic should look at the depth of the tube Figure 23-28 (a) Auscultation of epigastric and as measured by the centimeter marking at the lip line and (b) breath sounds. not let go of the tube until it has been secured in place. The depth will typically be 22 to 24 cm in the average sized adult patient. However, if the cuff was advanced 2 cm below the Equal sounds heard bilaterally strongly suggest proper vocal cords, then the endotracheal tube is in the correct posi- tube placement. Due to the anatomy of the carina and the tion. The stylet should be removed and the cuff infl ated. The mainstem bronchi (see Chapter 20), an endotracheal tube that tube position should be confi rmed and the tube secured. At is inserted too deeply will more often advance into the right this time, the Paramedic may release the tube. mainstem bronchus. If this occurs, lung sounds will be heard on the right but will be diminished or absent on the left. If this Confi rming Endotracheal occurs, the cuff of the endotracheal tube should be defl ated and the tube withdrawn 1 to 2 cm. After tube movement, the Tube Placement cuff should be reinfl ated and the lungs reauscultated. This pro- Once the tube has been placed, a bag-mask assembly device cedure is repeated until equal breath sounds are heard or the or automatic transport ventilator should be attached to venti- tube is pulled from the larynx. The second situation implies left late the patient. Ideally, an end-tidal carbon dioxide detector or lung pathology or a pneumothorax, depending on the clinical measuring device should be in-line from the fi rst ventilation. context. It is important to recognize that left mainstem intuba- When the fi rst breath is delivered, the epigastrium should be tions can occur and should be treated in the same manner as auscultated (Figure 23-28a). Loud noises over the epigastrium right mainstem intubations. with abdominal distention and no chest movement strongly Once the tube position is assessed by auscultation, the suggest esophageal placement. The tube should be removed Paramedic should assess placement using end-tidal carbon immediately while cricoid pressure is maintained. If no sounds dioxide measurement. Although ETCO measurement does 2 are heard at the epigastrium, auscultation at the mid-axillary have some limitations as previously described, it is considered lines at the level of the nipple line should be performed bilater- by many to be the gold standard of endotracheal tube place- ally (Figure 23-28b). ment assessment in the patient with spontaneous circulation. 442 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. If a disposable colorimetric capnometer is used, the Suction must be prepared. The misplaced tube is removed appropriate size (adult or pediatric) should be selected carefully. The patient is ventilated until the hypoxia resolves and placed between the ventilation device and the 15 mm while the tube is re-prepared or a second tube is prepared. adapter on the endotracheal tube. Six breaths should be Further steps to be taken before the repeat intubation attempt delivered to wash out carbon dioxide from the stomach in are discussed in the following text. case an esophageal placement has occurred. The device will A mnemonic that can help the Paramedic remember the originally be purple. If the tube is properly placed, the color causes of problem intubations is DOPE. The D in dope stands will change to yellow with each breath and fade back to a for displaced endotracheal tube; the O stands for obstructions yellow-purple color during inspiration. If the color change of the endotracheal tube, such as a mucous plug; the P sug- is intermediate between purple and yellow, tube placement gests the possibility of a pneumothorax; and the last letter, E, must be confi rmed by other methods. indicates equipment failure. If a continuous monitoring device is used, the sampler adapter is attached between the ventilation device and the Securing the Endotracheal Tube 15 mm adapter on the endotracheal tube. If a mainstream Once endotracheal tube position is confi rmed, the tube must device is being used, the infrared device must also be attached. be secured to prevent movement. The most common way to The Paramedic should watch the numerical readings (capnom- do this is through the use of a commercial or homemade tube etry) or the waveform (capnography). Although readings of tie. If a commercial device is used, be sure to confi rm endo- 30 to 40 are considered normal, the more important informa- tracheal tube depth before placing the device as many pre- tion is that the numbers or the wave rises and falls appropriately vent visualization of the tube at the lips. If a homemade tie is with ventilation, that the waveforms are consistent in shape, used, the Paramedic must confi rm that the tube cannot slip or and that no abrupt changes occur. It is important to realize move once the tie is complete. Taping the endotracheal tube that while different waveforms have different implications, the to the face, although appropriate in the operating room, is not presence or absence of a waveform (or consistent numerical appropriate in the prehospital setting due to the amount of trends with a capnometer) is the most valuable piece of infor- patient movement that will occur. mation for confi rming tube placement. It is also important to There is growing evidence that many endotracheal tubes note that end-tidal carbon dioxide detectors will not assess for found in the esophagus or the hypopharynx once the patient mainstem intubation or for hypopharyngeal placement |
of the reaches the emergency department are not misplaced tubes, endotracheal tube. but rather are displaced tubes. That is, the tube was origi- The limitations of end-tidal carbon dioxide detectors in nally in the trachea, but during patient movement it became patients without spontaneous circulation are clear: a patient displaced. Therefore, it is important that the tube position be who is not producing carbon dioxide nor circulating it to the assessed after each move. In addition, the biggest determinant lungs will not exhale carbon dioxide. Therefore, using an of tube movement is neck fl exion and extension. It has been esophageal detector device for confi rmation of endotracheal demonstrated that placement of a cervical collar and cervi- tube placement is appropriate. If a squeeze bulb is used, it cal immobilization device (head blocks and backboard) on should be squeezed and attached to the 15 mm endotracheal all intubated patients decreased the rates of displaced tubes.69 tube adapter. Immediate (less than 4 seconds) silent infl ation Therefore, all intubated medical and trauma patients should confi rms tracheal placement while noisy, fl atus-like sound or have a cervical collar placed and be immobilized on a long delayed infl ation suggest esophageal intubation. If a syringe- spine board, if possible (Skill 23–1 and Figure 23-29). type device is used, 40 mL of air in adults and 10 mL of air in children older than 2, that is withdrawn without resistance, confi rms tracheal placement. Resistance or inability to with- draw air suggests esophageal placement. It is important that the syringe plunger be all the way down and that the bulb be squeezed before attachment to the endotracheal tube. If an esophageal intubation occurs, the Paramedic must make a choice. If the patient is still well-oxygenated, a sec- ond intubation attempt can be made with the esophageal tube in place. This method has the advantage of the esophagus already being occupied by the misplaced endotracheal tube. The second endotracheal tube is placed in the only remain- ing opening, the larynx. The disadvantage of this technique is that it can be diffi cult to intubate around a tube that is already in place. Additionally, the patient is at increased risk for hypoxia. If the patient is hypoxic or it is impossible to intubate Figure 23-29 Intubated patient immobilized to around the esophageal tube, several steps must be taken. prevent dislodgement of the endotracheal tube. Intubating Airway Management 443 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. For a step-by-step demonstration of becoming detached from the adapter and the patient aspirat- Orotracheal Intubation, please refer to Skill 23-1 ing the endotracheal tube. on page 455. Confi rming Placement The endotracheal tube placement is confi rmed in the same Nasotracheal Intubation manner as in an orotracheal intubation. Lung sounds should If the patient is breathing, the Paramedic has the choice of be auscultated, an esophageal intubation detection device performing a nasotracheal intubation. Nasotracheal intuba- should be attached, and end-tidal carbon dioxide should be tion is particularly well suited for patients who, due to their measured. One important difference is that patients who are disease process (e.g., COPD exacerbation, CHF), are likely to nasally intubated are breathing spontaneously. Therefore, experience rapid decompensation if they lay fl at. In addition, auscultation may be misleading. Additionally, if the patient’s patients who are diffi cult to access (e.g., entrapped patients) status does not improve after the intubation, reassessment for may be easier to nasotracheally intubate than to orotracheally tube placement is necessary as the patient may appear to be intubate. Contraindications to nasotracheal intubation include tracheally intubated but in fact be esophageally intubated. apnea, evidence of basilar skull fracture, or inability to pass the tube through a nare (e.g., from a deviated septum). Securing the Endotracheal Tube Most commercial devices designed for securing an oral endo- Patient Preparation tracheal tube are not suited for securing nasal intubations. If the decision is made to nasotracheally intubate a patient, Folded tape, ties, or IV tubing is much better suited for secur- the patient must be prepared. The optimal position is the ing the tube. The tie should go the whole way around the head “sniffi ng position” with the patient sitting upright. The neck to provide maximum security. Again, the patient’s head and is fl exed and the head slightly extended across the atlanto- neck should be secured with a cervical collar and cervical occipital joint. The nose must be prepared with anesthesia and immobilization device if the patient is able to tolerate these lubricant. The patient should be asked for a history of nasal devices (Skill 23-2). fracture, surgery, or septal deviation. Although the larger nos- For a step-by-step demonstration of tril is most likely to provide the greatest success, once the Nasotracheal Intubation, please refer to Skill 23-2 nose is anesthetized, internal palpation with the small fi nger on page 456. may provide a good deal of information about obstructions and anatomy. Once the patient is properly positioned, the nose should be premedicated with a mixture of a nasal decongestant con- Street Smart taining neosynephrine and viscous lidocaine or lidocaine jelly (if the patient is not allergic to lidocaine). If possible, the The phrase “the hose follows the nose” describes the patient should inhale as these medications are administered to maximize the area reached. Use of the nasal decongestant behavior of an endotracheal tube. When the neck is decreases the risk of bleeding while the topical anesthetic extended (nose moves up), the endotracheal tube is improves patient comfort. Placing a nasopharyngeal airway displaced superiorly. When the neck is fl exed (nose coated with lidocaine jelly also helps anesthetize the mucosa and prepares the patient for the sensation of a device in moves “down”) the ETT is displaced inferiorly. This the nose. rule predicts the effects of head movement. Intubation If possible, an endotracheal tube designed for nasal intuba- tion should be used. The tube should be placed in the most Failed Intubation patent nare with the tip of the tube parallel to the fl oor of the If the intubation fails, the Paramedic must perform a rapid nose. The tube is advanced until breath sounds are audible assessment of why the failure occurred. If the fi rst attempt through the tube. A Beck Airway Airfl ow Monitor (BAAM) failed, performing the exact same techniques with the should be used, if available. This device changes the sound exact same equipment almost guarantees a second failure. of airfl ow to a whistle. The tube is rotated until breath sounds Therefore, it is important that the Paramedic understand or the whistle is at its loudest. The tube is then advanced why the failure occurred and what remedies will correct through the cords during inspiration. The patient may cough the failure. as the endotracheal tube passes through the cords; the The assessment of a failed intubation should focus on oper- Paramedic should continue to advance the tube. The tube ator failure, patient preparation failure, and equipment failure should be advanced until approximately 2 cm protrude from or incorrect selection. Operator failure is an honest assessment the nose. If the tube is advanced to the hub, it is at risk for of the Paramedic’s ability to perform the intubation. The best 444 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Paramedics are the ones who recognize when they are faced with an airway that is beyond their abilities to manage. This recognition in no way implies that the Paramedic is incompe- tent. Some patients’ anatomy is not compatible with oral or nasal endotracheal intubation without adjunctive devices such as intubating LMAs or fi beroptic devices. If the Paramedic is sure that ability is not the issue, then the next step is to assess patient positioning failure. Once the laryngoscope is in the patient’s mouth, it is often possible to recognize that a different position would allow for optimal oral, pharyngeal, and laryngeal axis align- ment. If this is the case, repositioning the patient, adding or subtracting padding behind the head, or changing to a HELP position are all acceptable actions. Often times the fi rst intu- bation attempt is made in an “as found” position. This should be corrected for any subsequent intubation attempts. The fi nal area of assessment is of equipment. The most basic question is whether or not the equipment is functioning correctly. A burnt-out laryngoscope bulb makes airway visu- alization impossible. The second question is the appropriate- ness of the equipment. If the incorrect blade or blade size has been chosen, an appropriate substitution should be made. The fi nal decision is the appropriateness of the technique and adjunctive devices. There are several intubation techniques and adjuncts that can be used to facilitate endotracheal intubation on the Figure 23-30 Digital intubation. second and third intubation attempts. These include digital intubation, use of the elastic gum bougie, translaryngeal illu- mination, and use of a fi beroptic stylet or bronchoscope. It is important to note that the Paramedic should not use these For a step-by-step demonstration of Digital Intubation, techniques for the fi rst time during an emergency situation. please refer to Skill 23-3 on page 458. Instead, they should be practiced in controlled circumstances, for example in an OR or simulation lab. The Elastic Gum Bougie Digital Intubation The elastic gum bougie is a useful adjunctive device for the management of the diffi cult airway. It is placed under direct Digital intubation is an endotracheal intubation technique visualization with a laryngoscope. It is most useful when that uses the Paramedic’s hand to identify laryngeal struc- the only anatomy that can be visualized are the posterior tures and to guide tube placement. It should only be used arytenoids. The tip of the bougie is advanced anterior to the for patients who are at no risk of biting the Paramedic. Like posterior arytenoids until the tip “clicks” along the tracheal nasal intubation, it is a blind technique. Therefore, multiple rings. An endotracheal tube is threaded over the external end techniques of tube placement confi rmation are critical. One of the bougie and advanced into the trachea. The external end advantage of digital intubation is that the patient’s head of the bougie should be stabilized to prevent it from becom- remains in a neutral position without movement. In addition, ing displaced. The cuff is infl ated and the gum bougie is with- digital intubation can be performed on a patient in a sitting drawn. The tube is confi rmed and secured in the usual fashion position and from below the head, which is useful for patients (Skill 23-4). for whom access to the head is limited. For a step-by-step demonstration of Elastic Gum The Paramedic prepares the endotracheal tube in the stan- Bougie, please refer to Skill 23-4 on page 459. dard manner. The patient’s tongue is grasped with gauze and retracted out of the mouth by an assistant. The Paramedic’s hand is then advanced to the posterior oropharynx. The index Translaryngeal Illumination fi nger is used to palpate and lift the epiglottis while the mid- Translaryngeal illumination, using a lighted stylet, takes dle fi nger palpates the arytenoid cartilages (Skill 23-3 and advantage of the larynx’s proximity to the anterior surface Figure 23-30). The dominant hand is used to advance the tube of the neck for endotracheal intubation. The patient should between the epiglottis and the arytenoids. Once the tube is in be placed into a neutral position for the intubation. If pos- place, it is confi rmed and secured in the standard manner. sible, the scene |
should be made as dark as possible. Placing a Intubating Airway Management 445 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. blanket over the Paramedic and the patient may make it pos- decreases the success of other methods of securing the air- sible to perform the technique during daylight conditions. way and of being able to face-mask ventilate the patient. Turn the stylet on and advance it into the midline of the phar- Continuing attempts could potentially lead to a completely ynx, following the mouth’s curvature. The stylet is advanced unmanageable airway. until a focal, bright midline glow is visible at the level of the The second reason for setting a limit to the number of larynx. It is advanced another 1 to 2 cm and then the stylet is airway attempts is that it drives the Paramedic to abandon removed. The cuff of the endotracheal tube is infl ated and the a technique (endotracheal intubation) that is not working. tube confi rmed and secured. By having a set limit on intubation attempts, the Paramedic must move on to other, more productive techniques. This limit prevents the “I’ll get it on the next attempt” syndrome Fiberoptic Stylettes/Bronchoscope that can only hinder patient care. Therefore, after three In some circumstances, obtaining a view from the distal failed intubations, the Paramedic should move on to other end of the endotracheal tube can improve the chances of techniques. successful intubation. Although expensive, these devices may turn an unobtainable airway into an obtainable one. It Supraglottic Airway Devices is unlikely that they will be commonly used in most EMS systems, but they may have a place in specialty systems. Once conventional endotracheal intubation has failed, the Two classes of devices—bronchoscopes (in which the tip next step is to use a supraglottic airway device. These devices can be controlled by the operator) and fi beroptic viewing provide a method of at least partially securing the airway in stylettes (in which the stylet is molded into shape before the the diffi cult-to-intubate patient. The three most commonly intubation but cannot be moved during the intubation)—are used devices, as described earlier, are the King LTS-D air- used. The second class of devices is less expensive. Both way, the laryngeal mask airway, and the esophageal-tracheal are limited in their utility if there is blood or vomit in the Combitube. airway; the view through the scope is rapidly degraded by these substances. King LTS-D Airway The devices should be prepared according to the manu- Prepare the patient as previously described for endotracheal facturer’s specifi cations. The endotracheal tube is loaded onto intubation, including preoxygenation, monitoring, and supine the scope and the viewing tip of the scope treated with antifog position. With the left hand, grasp the tongue and jaw and solution. If a fi beroptic viewing stylet is used, it should be lift toward the ceiling. With the right hand, insert the King molded into a hockey stick shape before insertion. The scope airway from the right side of the mouth and direct it toward and tube are advanced under direct visualization until the tip the oropharynx. As the King airway is advanced, rotate the of the scope passes through the cords. If a bronchoscope is airway counterclockwise as it seats in the proper position. used, the tip can be manipulated to direct the scope into the Advance the airway until the orogastric port is approximately larynx. The endotracheal tube is then advanced through the at the level of the front teeth. Infl ate the balloons and venti- cords, the scope is withdrawn, and the cuff is infl ated. Usual late the patient. Auscultate breath sounds while gently pulling methods of confi rming tube placement and securing the tube back on the airway until the sounds are the loudest. Secure are used. the King airway in position after confi rming placement Fiberoptic devices can also be used to confi rm endo- (Skill 23-5). tracheal tube placement in diffi cult intubations. Once For a step-by-step demonstration of King the endotracheal tube has been placed, the scope can be Airway Placement, please refer to Skill 23-5 passed through the tube under direct visualization. Once on page 461. the scope advances beyond the tip of the endotracheal tube, the Paramedic can identify the trachea by the presence of tracheal rings or the esophagus by the lack of rings and The Laryngeal Mask Airway the collapsing walls. Although other methods, such as The laryngeal mask airway transfers the seal of the face end-tidal carbon dioxide monitoring and the esophageal mask from the patient’s face to his larynx. The prepared intubation detection devices, are generally reliable, direct device, as previously described, has the cuff mask defl ated visualization of tracheal rings is another way of confi rming and the tip lubricated. The mask should be picked up with tube placement. the thumb in the space between the tube and the mask. The The Paramedic should make the most of each intu- mask is placed in the oropharynx with the tip against the bation attempt. He should make no more than three hard palate. It is advanced into the hypopharynx with gentle attempts to intubate the patient. There are two main rea- pressure from the thumb. The mask is pushed until resis- sons for establishing a clear limit to the number of intu- tance is met. If the appropriate-sized mask is used, it will bation attempts. The fi rst is that each intubation attempt sit with the tip in the proximal esophagus and automatically causes airway trauma and makes each subsequent intubation position the mask. The pilot balloon will indicate the correct attempt more diffi cult. In addition, each intubation attempt volume of infl ation for the mask. When the mask is infl ated, 446 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. the tube should “lift” slightly out of the mouth as it seals until it rests securely at its appropriate depth (depth markers (Figure 23-31). on the tube should be at the level of the teeth). If resistance Laryngeal mask airway placement is confi rmed by aus- is met, the device should not be forced. A small amount of cultation, end-tidal carbon dioxide measurement, and assess- cricoid pressure may increase the chances of a tracheal place- ment of patient status. The esophageal intubation detector ment, and should be avoided. device does not function with the LMA. Even when the epi- Once the Combitube has been inserted, the pharyngeal glottis is folded over, the LMA provides highly effective ven- cuff is infl ated fi rst with 100 cc of air. Then, the distal cuff tilation.70 The LMA is secured with the tube curved toward is infl ated with 10 to 15 cc. The patient is ventilated through the feet with a wrap of tape. the pharyngeal lumen. Chest rise and lung sounds indicate esophageal placement and ventilation is continued through The Esophageal-Tracheal Combitube this tube. If no lung sounds are appreciated and the chest The Combitube offers an effective method of securing the does not move, the patient is ventilated through the tracheal airway in either esophageal placement or tracheal placement. lumen; the patient should now have lung sounds and chest Once the equipment is prepared as previously described, rise (Figure 23-32). the jaw is grasped and lifted anteriorly with the thumb in Device placement is confi rmed with auscultation and the mouth and the fi ngers under the mandible. The device is end-tidal carbon dioxide monitoring. The esophageal intuba- inserted following the curvature of the oro- and hypopharynx tion device will not work on the pharyngeal lumens and has not been confi rmed as reliable for use on the tracheal lumens; it should therefore not be used. The patient’s status must be continuously monitored. Although the pharyngeal balloon contributes greatly to tube security, the device must still be secured with a tie and the patient should have a C-collar and cervical immobilization. Despite their ease of use, both devices do have compli- cations associated with them. Excessive force during inser- tion can cause tracheal and esophageal injury. The devices can become dislodged and misidentifi cation of tube posi- tion has been reported in some cases. Therefore, careful monitoring and frequent patient reassessment is necessary. If a blind insertion airway device does not successfully secure the airway, the Paramedic must move on to other options. Bag-Valve Mask and Automatic Transport Ventilator Figure 23-31 LMA placement. Face-Mask Ventilation If the Paramedic has attempted to intubate and to place a blind insertion airway device without success, he is faced with a “can’t intubate” situation and his options are lim- ited. Two alternatives remain, either manual ventilation or a surgical airway. If it is possible to face-mask venti- late the patient, then no further interventions are needed (Figure 23-33). Constant vigilance and frequent patient reassessment is the key to good, high-quality non-intubated face-mask ventilation and airway management. An oropharyngeal or nasopharyngeal airway should be inserted in these patients. It is possible that a patient who cannot be intubated can also not be ventilated (a “can’t intubate, can’t ventilate” situ- ation). Trauma, facial hair, burns, or anatomic distortion may lead to this condition. If this is the case, the patient must be Figure 23-32 Combitube placement. prepared for a surgical airway. Intubating Airway Management 447 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. fi ngers to palpate—but not occlude—the patient’s carotid pulses and stabilize the trachea. Once the landmarks have been identifi ed and stabilized, hold a #20 scalpel low in the right hand at a 90-degree angle to the membrane. Make a stab incision in a horizontal plane through the skin and membrane and hold the scalpel in place. The left hand can now release the trachea, grasp the tracheal hook, and place the hook into the incision. Gently pull against the cricoid ring toward the patient’s feet to again stabilize the trachea. Once the cricoid ring is stabilized by the tracheal hook, remove the scalpel. Now, using the right hand, pick up the tracheostomy tube or endotracheal tube and place it into the trachea through the incision. If you are using an endotracheal tube, take care not to insert the tube too far Figure 23-33 Face-mask ventilation using an into the trachea. A mainstem bronchus can easily be intu- automatic transport ventilator. bated with this procedure due to the relatively long length of the endotracheal tube. It is important to note that the patient will bleed dur- Surgical Airway ing this procedure; it is to be expected. Even if the patient is bleeding heavily, the Paramedic’s fi rst priority must be to In the patient that can neither be intubated nor ventilated, secure the airway. Once a tube is safely in place, the issues of emergency access of the trachea via a surgical technique is bleeding can be addressed. mandatory. This technique can be life-saving for the patient Endotracheal tube placement should be assessed in the who has an otherwise unmanageable airway. The three most usual manner. The tube should be secured with a strap which common methods of obtaining this type of airway access ties completely around the neck. The endotracheal tube should are the surgical |
cricothyroidotomy, needle cricothyroido- be trimmed to the shortest length possible without damag- tomy, and placement of a percutaneous cricothyrotomy ing the cuff infl ation system. If a C-collar with an opening device. on the anterior surface is available, this should be placed as Surgical Cricothyroidotomy well. However, the Paramedic must be able to constantly reas- sess the neck for signs of air infi ltration (swelling or crepitus) The surgical cricothyroidotomy is a conceptually simple pro- (Skill 23-6). cedure that involves cutting through the cricothyroid mem- For a step-by-step demonstration of Rapid Four-Step brane and placing an endotracheal tube through that hole. In Surgical Cricothyrotomy, please refer to Skill 23-6 on practice, it is a diffi cult procedure in that it is done under page 462. emergency situations and the factors that make intubation and ventilation diffi cult (trauma, anatomical distortion, or anomalies) also make performing a surgical cricothyroido- Needle Cricothyroidotomy tomy diffi cult. Like all airway procedures, it is best practiced The technique of needle cricothyroidotomy is a simple, fast, before it is needed. and effi cient method of turning an “emergency” (no airway or The equipment needs, discussed previously, include a ventilation) into an “urgency” (defi nitive airway still needed scalpel, a tracheal hook, and a 6.0 to 6.5 mm ID endotracheal but patient now oxygenating). The keys to the technique are tube. The patient should be placed in a supine position and, if good landmark identifi cation and care in ventilation to pre- possible, the neck prepped with an iodine-containing solution vent overpressurization. or alcohol. The patient is positioned supine with the neck in a neutral Although there are a number of ways to perform a surgi- position. The non-dominant hand is used to stabilize the larynx cal cricothyroidotomy, the rapid four-step cricothyroidotomy while the dominant hand locates the cricothyroid membrane. If method71 is simple, relatively safe for the Paramedic, and an a safety catheter is being used, it is inserted through the crico- easy-to-perform procedure. The four steps to this procedure thyroid membrane directed toward the feet in the same manner include identifi cation, incision, traction, and intubation. Each as the insertion into a vein (Figure 23-34). of these steps will be reviewed individually. When resistance decreases, the IV is in the trachea and First, stand or kneel to the left of the patient. Using the the catheter should be advanced to the hub while the needle is left hand, palpate the cricothyroid membrane with the index slowly withdrawn. Once the IV catheter has been advanced to fi nger. If diffi culty is experienced in locating the cricothy- the hub, the safety mechanism on the IV is activated. If a non- roid membrane, begin palpating at the sternal notch and safety IV catheter is used, the device is attached to a 5 to 10 cc move toward the head until the uppermost tracheal ring is syringe. The syringe is aspirated during insertion, which is felt. This is the cricoid cartilage. Use the thumb and middle also toward the feet. When air returns, the whole device is 448 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. with a removable trochar, insertion of a small device with subsequent dilators, or a Seldinger (over the wire) technique. The fi rst class of devices (Figure 23-36) uses a relatively large catheter to puncture the cricothyroid membrane. Once in the trachea, the needle is removed and the catheter advanced Branches of Thyroid cricothyroid cartilage to its maximum depth. It is secured in place and attached to artery a BVM with a built-in 15 mm adapter. These devices have a minimum of parts and are easy to use. The second class of devices (Figure 23-37) is placed through the use of a smaller needle for puncture. Once a small needle is introduced into the airway, serial dilation or placement of a through-the-needle larger catheter allows the size of the original catheter to be increased. Once the largest device is in place, the trochar is removed and the device is secured. There is an adapter on the largest cannula that allows Cricoid a BVM or ventilator to be attached. These devices are also cartilage Vocal void Laryngeal ventricle Figure 23-34 Needle insertion for needle cricothyroidotomy. advanced 5 mm and then the needle is carefully withdrawn while the catheter is advanced to the hub. The catheter is stabilized in place while the high-pressure oxygen source and fl ow control device are attached (they attach with a standard threaded adapter). Although the cath- eter should be secured with tape, it should also be stabilized by hand throughout the entire management so that high pres- sures and movement do not dislodge the catheter. The gas fl ow through a 21 gauge catheter with a 50 PSI source is 1,600 mL/ sec.72 Therefore, ventilation time is 0.5 to 1 second with 3 to 5 seconds (an inspiration to expiration ratio of 1 to 3) between each ventilation to allow adequate expiration. One variant of the needle cricothyroidotomy is the use of an Arrow Rapid Infusion Catheter (RIC) set (Figure 23-35) to increase the size of the catheter. Once a 21 or 16 gauge cath- Figure 23-35 Rapid Infusion Catheter (RIC) set. eter is in place, a small wire is inserted through that catheter (Courtesy of Telefl ex Medical/Arrow International) until the distal end of the wire is in the trachea. The origi- nal IV catheter is removed, a small nick is made in the skin, and the RIC catheter and dilator are threaded over the wire and inserted through the skin to the hub. The dilator and the wire are then removed and the larger RIC catheter remains in place. Percutaneous Devices There are a number of manufacturers of percutaneous airway management kits. As each manufacturer’s device and inser- tion technique is different and new kits are being introduced, it is not practical to examine each specifi c device. Instead, it is important to recognize that there are three general techniques and most devices use a variant of one of these techniques. The three techniques are direct insertion of a larger device Figure 23-36 Needle and trochar-type device. Intubating Airway Management 449 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Post-Intubation Care Once a patient has been intubated, the tube placement con- fi rmed, and the tube secured, there are some procedures that may need to be performed to maximize the patient’s respiratory care. Although ongoing ventilation is the most obvious of these pro- cedures, other care should also be considered. Other procedures include placement of a nasogastric or orogastric tube and tra- cheobronchial suctioning. Post-Intubation Ventilation It is important for the Paramedic to recognize that the major goal of emergency airway management is to oxygenate the patient. Therefore, proper post-intubation ventilation is criti- Figure 23-37 Percutaneous cricothyroidotomy cal to minimize hypoxia. using dilators. Most providers will use the bag-valve-mask device as their standard “ventilator.” Although adequate ventilation can be obtained with the BVM, the fi ner details of its use are not intuitive. The volume of an adult-sized BVM device will range based on the manufacturer but will usually be between 1,500 and 2,000 mL. For an intubated patient, ventilation volumes of 7 cc/kg ideal body weight (3 to 3.5 cc/lb ideal body weight) are usually adequate. At a ventilatory rate of 12 breaths per minute, a 70 kg adult will have a minute ventilation of approximately 6 liters. This is adequate for most patients; those with asthma or other pulmonary disease, however, may require minute ventila- tions of up to 20 LPM. Therefore, ventilation must be adjusted to suit the patient’s clinical condition. Unfortunately, it may be diffi cult to adequately gauge minute ventilation when using a BVM as it is diffi cult to determine exactly what volume is being delivered. Furthermore, using a BVM requires a provider to squeeze the bag, thereby tying up someone who could be Figure 23-38 Percutaneous cricothyroidotomy providing other care. using Seldinger technique. Many services, particularly those performing critical care transports, have begun to use more and more sophisticated ventilators to provide ventilation to intubated patients. These easy to use but tend to have more parts than direct insertion devices may range from selecting preset volume/rate combi- devices. nations to being able to independently control volume, rate, The third class of devices (Figure 23-38) uses a Seldinger, and end-expiratory pressures to being able to select between or over the wire, method of placing a tracheostomy-like tube. pressure control modes, volume control modes, and support A small catheter is used to cannulate the airway and a wire is modes. The most basic parameters to be set are the rate and placed through that catheter. The original catheter is removed volume (or peak pressure); these two parameters establish the and progressively larger catheters are placed until a fi nal, minute ventilation. By being able to set the minute ventila- large tube is placed. The wire is then removed and the device tion, the patient will receive consistent ventilation without secured. Although these devices allow for the placement of factors such as human fatigue playing a role. a large fi nal airway, they have many parts and require some Every manufacturer has special features and charac- degree of dexterity to use. Therefore, their application in the teristics of its ventilators. Therefore, it is important that all prehospital environment is somewhat limited. Paramedics familiarize themselves with the ventilator that Regardless of the percutaneous technique used, there they will be using. The manufacturer should be able to provide are some important rules. Landmark recognition is a critical training and reference materials for the use of its equipment component of correct performance of this skill. Furthermore, and special features of that particular type of ventilation. bleeding is expected. As with other techniques, the Paramedic There are a number of advantages and disadvantages must fi rst secure the airway and then focus on bleeding con- to automatic transport ventilators. Most importantly, they trol. Finally, all of these techniques should be practiced regu- provide consistent and predictable ventilation. They also larly as they require some motor skill and familiarity with the free a provider from the task of squeezing a BVM device. equipment. They are lightweight, relatively inexpensive, and most are 450 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. oxygen powered. Many have high-pressure alarms and other alerts that notify the Paramedic of changes in the airway or of the patient’s condition. Disadvantages include an inabil- ity to detect sudden changes in compliance (e.g., displaced tube, pneumothorax), the start-up costs of the devices, the need to have disposable ventilator circuits available, and the dependence on an oxygen source to provide ventilation. Nonetheless, many agencies fi nd the overall convenience and utility of ventilators offset their disadvantages. Orogastric and Nasogastric Tube Placement All patients who receive positive pressure ventilation before intubation have some degree of gastric infl ation. In adults, this gastric distention increases the risk for vomiting and aspira- Figure 23-39 Nasogastric tube. tion and, to some degree, compromises respiratory mechanics. In the pediatric patient, the same concerns for vomiting and aspiration exist. However, the ventilatory compromise that should be marked or otherwise noted |
as this is the proper occurs with gastric infl ation can make ventilation completely depth of insertion for the tube. ineffective. Therefore, the placement of an orogastric tube, a The tip of the tube is then lubricated and inserted into the single-lumen tube passed through the mouth into the stomach nare parallel to the fl oor of the nose. A common mistake is to to evacuate air from the stomach, in all patients who have angle the tube superiorly during insertion. This tendency can received non-intubated bag-valve-mask ventilation should be be eliminated by putting the index fi nger of the non-dominant considered mandatory. In addition, conscious patients with hand on the tip of the nose and lifting up to pull the nostrils bowel obstruction or toxic ingestions may benefi t from the upward. The tube is then advanced until it strikes the pos- placement of a nasogastric tube, a single-lumen tube passed terior nasopharynx. Gentle pressure and rotation will make through the nose into the stomach to evacuate air from the it turn downward. It should be advanced to the previously stomach. noted insertion depth. Although the patient may gag with cor- There are contraindications to the placement of gastric rect placement, coughing or loss of the ability to speak sug- tubes. Patients with esophageal obstruction cannot have a gas- gest placement of the gastric tube through the vocal cords. In tric tube placed. In addition, caution must be used in placing that case, the tube should be partially withdrawn. Having the a gastric tube in a patient with a history of esophageal disease patient swallow while the tube is being advanced will increase (varices or caustic ingestion) and, in the case of nasogastric the chances of successful placement. tubes, in patients at risk for basilar skull fractures. Once the tube is at its proper insertion depth, immedi- Gastric tubes are long, thin tubes of various internal diam- ate return of stomach contents indicates a gastric placement. eters designed to be blindly placed into the stomach. The tube Even if nothing returns, 500 cc of air should be injected into is sized based on its purpose (decompression of the stomach the tube while the Paramedic auscultates over the epigastrium. or evacuation of contents), the size of the patient, and if naso- Loud sounds confi rm proper tube placement. The tube is then gastric (smaller tube) or orogastric (larger tube) placement is secured to the nose and face with tape and the stomach either planned. A gastric tube, a catheter tip syringe, and some form suctioned or allowed to equilibrate with the outside pressure of lubricant (Figure 23-39) are needed to place the tube. (Skill 23-7). Placement of a nasogastric tube is typically done in an awake patient who will not tolerate an orogastric tube. The For a step-by-step demonstration of Nasogastric patient and equipment must be prepared. Unless contraindi- Tube Placement, please refer to Skill 23-7 on cated, use of a nasal decongestant (e.g., Afrin®) and a topi- page 463. cal anesthetic (e.g., viscous lidocaine or lidocaine jelly) to Orogastric tube placement is generally performed in the premedicate the patient is advised. The patient should be unresponsive, apneic patient after intubation. The patient will examined for nasal pathology (e.g., tumors, trauma, and sep- typically be supine. The tube is measured from the point tal deviation) which would preclude use of the nostril. The just below the tip of the xyphoid to the angle of the jaw and patient should then sit in a neutral position. then to the lips. The patient is prepared by performing a jaw If possible, prewarming the gastric tube will make it pass lift. The gastric tube, already lubricated, is inserted into the more easily. The tube must be measured for size. For a naso- mouth and advanced until it strikes the posterior orophar- gastric tube, the tip of the tube is placed just inferior to the ynx. Gentle manipulation should cause it to turn inferiorly. xyphoid. The tube is then measured to the ear and bent anteri- It is advanced to its proper depth and position is confi rmed orly where it is measured to the tip of the nose. This distance in the same way as for the nasogastric tube. Generally the Intubating Airway Management 451 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. until resistance is met. The catheter is then withdrawn with a total time of no more than 15 seconds. The patient is then oxygenated and ventilated before another suction attempt is made (Skill 23-8). For a step-by-step demonstration of Tracheobronchial Suctioning, please refer to Skill 23-8 on page 465. Special Circumstances Although the Advanced Airway Management Algorithm will provide guidance for most airway management issues, there are a few circumstances that are not easy to predict and do not fall into a single category of action. It is therefore important Figure 23-40 Flexible French suction catheters. for the Paramedic to be well versed in the management of special circumstances. These circumstances include patients with stomas, trauma patients, and pediatric patients. gastric tube is secured separately from the endotracheal tube Stoma Management to prevent a mishap with one from affecting the other. Patients may have stomas for any number of reasons. For Gastric tubes are not without their complications. the Paramedic, it is important to recognize whether the Complications associated with both oral and nasal placement patient only has a tracheostomy (where the airway is oth- include supragastric placement, curling in the oropharynx, erwise intact) or if the patient has had a laryngectomy as endotracheal placement, and tube obstruction. Endotracheal well (where the trachea is rerouted to the skin and there is placement can even occur in the patient who is already endo- no connection between the upper airway and the trachea). tracheally intubated, particularly if a smaller diameter gastric Patients with complete laryngectomies are completely tube is used. For nasogastric (NG) placement, nasal trauma dependent on the patency of their tracheostomy to venti- can lead to extensive bleeding. The patient with an orogastric late. Patients may also have a well-healed stoma or may (OG) tube is at risk of biting the OG tube if some type of bite still have a tracheostomy tube in place. If there is a tube block protection is not used. Excessive force during place- in place, it is at risk for occlusion and displacement with ment can cause airway injury, laryngeal injury, and esopha- subsequent obstruction. geal injury. Tracheostomy tubes and stomas may become occluded with mucus or other substances. Often, simple suction Tracheobronchial Suctioning maneuvers are suffi cient to clear these orifi ces. Suctioning Many patients who require intubation have some degree of lung is performed by preoxygenating the patient and injecting pathology. This can range from aspiration to thick mucus plug- 2 to 3 cc of normal saline into the stoma. The patient exhales ging to blood. Once a patient has been intubated, the Paramedic and a soft-tip catheter is inserted until resistance is met. The has access to the trachea and bronchial tree for suctioning in site is then gently suctioned. If there is an inner cannula to the a way that is not possible without intubation. Therefore, the tracheostomy tube, it can be removed and either replaced or technique of deep tracheal or tracheobronchial suctioning, cleaned and returned. direct suctioning of the secretions in the bronchial tree, is an Over time, a stoma may undergo stenosis or narrowing. important skill to master. This can be a life-threatening condition if stoma stenosis pre- Soft, long, and thin suction catheters (Figure 23-40) are vents ventilation and the patient can acutely decompensate. used for tracheobronchial suctioning. These catheters can The patient should have an endotracheal tube placed through either be single-use catheters or can be designed as a pre- the stoma immediately to relieve the obstruction. assembled component of a ventilator circuit. This second Tube replacement is accomplished through the use of a type of catheter offers the advantage of not requiring that the tracheostomy tube or an endotracheal tube. In addition, criti- v entilator be unhooked from the endotracheal tube before cally ill patients with stomas who need to be ventilated should suctioning. These devices do, however, add more dead air have a tube placed to facilitate ventilation. The tracheostomy space to the ventilator circuit. tube or cuffed endotracheal tube is lubricated. It is advanced The patient should be prepared for deep tracheal suction- through the stoma until the cuff is in approximately 2 cm. ing with aggressive preoxygenation. If the patient has copi- The cuff is then infl ated, the position confi rmed, and the tube ous or thick secretions, a 3 to 5 cc saline fl ush down the endo- secured to the neck. Care must be taken to avoid excessive tracheal tube followed by two to three quick ventilations may movement of the tube as there is only a small amount of the help. The catheter should be advanced carefully and inserted tube in the airway. 452 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. The Trauma Patient The Pediatric Patient Airway management of the trauma patient is not fundamen- Pediatric patients present the Paramedic with a special set of tally different from airway management of any patient. There issues and problems. Although the fundamental equipment are some important considerations, however. These include and techniques are the same, the anatomic and physiologic concerns about airway injuries, cervical spine movement, the differences discussed in Chapter 20 result in differences in need for early interventions for respiratory compromise from the airway management of these patients. As was discussed in chest wall or pulmonary injuries, and consideration for the Chapter 22, good face-mask ventilatory skills are mandatory early and aggressive use of sedation and paralysis. for pediatric airway management. Any patient experiencing a traumatic injury is at risk for trauma to the airway itself. When assessing a trauma patient, the Paramedic must quickly evaluate the impact of all injuries Best Practice on the airway and how they will affect his decisions and tech- Traditionally, it has been accepted that prehospital intubation niques. Burns tend to produce early and signifi cant airway of pediatric patients is good care. Studies have demonstrated damage requiring rapid intubation. Laryngeal trauma can dis- that Paramedics can perform pediatric endotracheal intuba- tort anatomy, obstruct the airway, and produce copious airway tion74 although usually with higher complication rates and bleeding. Tracheal transection makes successful orotracheal lower success rates than for adults.75–77 Most of these stud- intubation unlikely. An open tracheal transection, however, ies have been retrospective in nature and therefore are some- invites intubation through the wound. When managing a trau- what limited by study design and data collection. The only matized airway, suction and good tube placement confi rma- major prospective trial on prehospital pediatric endotracheal tion skills are critical. intubation demonstrated a trend toward worse outcomes with All trauma patients with an altered level of conscious- intubation.78 ness or an appropriate mechanism must be considered to have Although no single trial should completely change prac- a cervical spine injury. Therefore, all of these intubations tice, the fi ndings of this study should cause all Paramedics must be performed with the patient’s head in a neutral posi- and medical directors to give strong consideration to review- tion. One provider should be assigned the task of maintaining ing system pediatric intubation success rates and outcomes. C-spine immobilization and the C-collar should be opened At present, there is no recommendation for or against pedi- anteriorly to facilitate jaw movement. Always remember that atric |
intubation. What is clear, however, is that excellent apnea in an otherwise apparently uninjured patient may rep- non-intubated face-mask ventilation skills are important in resent a spinal cord transection. the management of critically ill children. Trauma to the chest can cause considerable injury. Two important injury processes—fl ail chest and tension The Advanced Airway pneumothorax—will have an impact on airway and ventila- Management Algorithm tion management. In fl ail chest, two or more fractures of two or more consecutive ribs disrupt the stability to the rib cage, There are signifi cant anatomical and physiological differences resulting in paradoxical collapse inward of that section of between adult and pediatric patients. Earlier in this chapter, the chest wall during inspiration. This results in underinfl a- differences in the size of equipment were noted, although the tion of the affected lung. In addition, the trauma necessary to equipment itself is fundamentally the same. In addition, the produce a fl ail segment will also usually injure the underly- Advanced Airway Management Algorithm can be applied to ing lung. Therefore, early stabilization of the fl ail segment is adults and pediatric patients. There are some important dif- important to maximize the patient’s ventilatory function. ferences, however, in the techniques that should be applied. A pneumothorax may also cause signifi cant respiratory compromise. Although there is emerging evidence that pre- Patient Preparation hospital needle decompression does not have a signifi cant The anatomic differences of the pediatric head make posi- impact on patient outcome,73 few would argue that a patient tioning much more important. Laying a child supine without with respiratory compromise, unilateral diminished or absent padding will result in neck fl exion with “crimping off ” of the lung sounds, and shock should not receive the benefi t of a airway (Figure 23-41). However, excessive head extension needle decompression. Early recognition and rapid diagnosis can also “crimp off ” the airway. Therefore, neutral position- of the injury is absolutely necessary. ing is much more ideal. Trauma patients, particularly multi-trauma patients, Airway manipulation of children under age 8 increases often are suffi ciently ill to have lost their airway refl exes and vagal tone and may become a major concern during airway to be combative, but not to be obtunded. This is particularly management. These children can rapidly become brady- true if the patient has a head injury. Early and aggressive cardic and asystolic. Therefore, premedication with atropine use of medication-facilitated and rapid sequence intubation (0.02 mg/kg, minimum 0.1 mg, maximum 0.5 mg) is manda- techniques to secure these patient’s airway is warranted. The tory in all of these children. Use of atropine or glycopyrrolate issue will be discussed in greater detail in Chapter 24. will also help to minimize secretions. Intubating Airway Management 453 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. markers and should be positioned on either side of the vocal cords. Although ultimately the tube may need to be moved due to fi ndings on patient examination, these markers gener- ally do an excellent job of placing the tip of the endotracheal tube at about the middle of the trachea. Tube Placement Confi rmation Confi rming the endotracheal tube placement in pediatric patients can be challenging. Due to the smaller body size, lung sounds and epigastric sounds may be hard to distin- guish. The esophageal intubation detector device may report an esophageal intubation despite placement in the trachea due to low lung volumes. However, in a patient with a pulse, an appropriately sized colorimetric end-tidal carbon dioxide detector or capnography device will work. Therefore, con- Figure 23-41 Overextension can cause stant reassessment of the end-tidal carbon dioxide and vigi- obstruction in a pediatric airway. lant monitoring of the patient’s status is critical. Once the tube position is confi rmed, continuous moni- Pediatric Intubation toring for a displaced endotracheal tube is also critical. The Techniques for selecting the proper-sized blade and endotra- smaller size of pediatric patients puts them at high risk for cheal tube were discussed previously. In most children under tube dislodgment. Any changes in the patient status should 4 to 5 years of age, a straight blade is the most appropriate make one consider the “DOPE” mnemonic: displaced endo- blade to use. For older children, the Paramedic should use the tracheal tube, obstructed tube, pneumothorax, or equipment blade type with which she is most comfortable. failure. Immobilization of the patient is an important preven- When intubating, the redundant and loose oral mucosa tative measure against tube dislodgement. has the potential to compromise visualization of the vocal cords. Therefore, purposeful precise movement to control Airway Rescue Devices as much tissue as is possible is mandatory. In addition, care The major difference between adult and pediatric patients must be taken to minimize bleeding from these very friable regarding rescue devices is that the King airway and the tissues. Suction, if used, should be applied judiciously and Combitube are not sized for pediatric patients. However, there never directly to the tissue. is evidence that the laryngeal mask airway (LMA) is an excel- The pediatric patient has minimal respiratory reserve. lent rescue device for children.79, 80 The LMA is sized for infants Therefore, hypoxia occurs early and prolonged intubation and children and is easily placed. Therefore, the LMA should attempts put the patient at risk for rapid desaturation. Failed be the rescue airway of choice for pediatric patients in whom intubation attempts should be abandoned early in favor of orotracheal intubation cannot be performed. face-mask ventilation. In addition, as face-mask ventilation may result in better outcomes than intubation anyway, a sin- Surgical Airway Options gle failed intubation attempt should cause the Paramedic to The small size of the pediatric airway and the signifi cant risk consider whether further attempts are warranted or if face- of airway scarring contraindicates all surgical airway manage- mask ventilation is the better choice. ment techniques with the exception of the needle cricothyroido- When passing the endotracheal tube, the smallest diam- tomy. This technique can be performed on children of all ages. eter of the pediatric airway is at the cricoid ring. Therefore, if Catheter placement should be performed in the same manner the tube passes through the vocal cords but does not advance as the placement of an IV in a vein. Although the ideal location any further, a smaller tube may be needed. A small air leak is through the cricothyroid membrane, it is often impossible around the tube is acceptable and, if airway pressure manom- to locate this structure in very small infants. Therefore, a gen- etry is being performed, the leak should occur at around eral location of the thyroid cartilage should be determined 10 cm H O. This leak acts as a “safety valve” for preventing 2 and the catheter placed in the midline just inferior to the thy- acute barotrauma. roid cartilage. Short inhalation times and a smaller catheter The pediatric endotracheal tube has a pair of black lines at should also be used to minimize peak pressures, to deliver appro- the distal end of the endotracheal tube. These lines are depth priate volumes, and to minimize the risk of acute barotrauma. 454 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Skill 23-1 Orotracheal Intubation 1 Prepare equipment. 2 Position patient. 3 Holding laryngoscope in the left hand, place it in the right 4 Pass endotracheal tube. side of the mouth and sweep to the left. 5 Confi rm placement. 6 Secure the endotracheal tube. Intubating Airway Management 455 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Skill 23-2 Nasotracheal Intubation 1 Prepare equipment. 2 Position patient. 3 Use afrin and lidocaine jelly to prepare nostril. 4 Insert right nostril. 5 Pass into nasopharynx. 6 Listen for loudest breath sounds. 456 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Skill 23-2 (continued) 7 Advance during inhalation. 8 Confi rm placement. 9 Secure nasotracheal tube. Intubating Airway Management 457 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Skill 23-3 Digital Intubation 1 Prepare equipment and confi rm absence of gag refl ex. 2 Insert hand into mouth and walk fi ngers down tongue. 3 Lift epiglottis with middle fi nger. 4 Guide endotracheal tube into trachea. 5 Confi rm placement. 6 Secure endotracheal tube. 458 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Skill 23-4 Elastic Gum Bougie 1 Perform laryngoscopy in the usual fashion. 2 Place bougie by aiming the tip midline and anterior. Bougie Cartilage rings Vocal cord 3 The bent tip will click as it passes across the cartilage rings 4 Assistant passes endotracheal tube over bougie while and advance until the black band is at the corner of the mouth. keeping the tissues out of the way with the laryngoscope. Intubating Airway Management 459 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Skill 23-4 (continued) 5 Insert endotracheal tube. 6 Remove bougie. 7 Confi rm placement and secure endotracheal tube. 460 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Skill 23-5 King Airway Placement 1 Grasp tongue and jaw, lifting toward ceiling. Place tip of tube 2 Rotate the airway counterclockwise as it is advanced. toward oropharynx, approaching from the patient’s right. 3 Advance until the orogastric port is at the level of the teeth. 4 Infl ate balloon, bag-ventilate the patient, and auscultate breath |
sounds. 5 Slowly withdraw while listening until breath sounds are the 6 Confi rm placement and secure airway. loudest. Intubating Airway Management 461 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Skill 23-6 Rapid Four-Step Surgical Cricothyrotomy 1 Position to the patient’s left side. 2 Palpate landmarks and stabilize cricoid ring with left hand. 3 Make stab incision with scalpel over the cricothyroid 4 With the left hand, place tracheal hook around the cricoid membrane. In obese patients, make a vertical incision and use cartilage and gently pull toward the patient’s feet. the handle to bluntly dissect the tissue until you visualize the cricothyroid membrane. Hold scalpel in space. 5 Place endotracheal or tracheostomy tube. 6 Confi rm placement, control bleeding, and secure tube. 462 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Skill 23-7 Nasogastric Tube Placement 2 Position and premedicate if possible. 1 Prepare equipment. 3 Measure for length. 4 Insert lubricated tube in nostril. Intubating Airway Management 463 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Skill 23-7 (continued) 5 Ask patient to swallow as tube is advanced. 6 When tube is at length, confi rm placement by instilling 60 cc of air with a Toomey syringe while auscultating the epigastrium. 7 Secure the tube with tape. 464 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Skill 23-8 Tracheobronchial Suctioning 1 Prepare equipment and don sterile gloves. 2 Place 3 to 5 cc of saline down endotracheal tube as a fl ush. 3 Advance suction catheter until resistance is met. 4 Apply suction. 5 Twist the catheter while withdrawing with suction on. 6 Suction sterile saline to clear suction catheter. Intubating Airway Management 465 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. It is critically important that the Paramedic master basic, non-intubating airway management. However, the defi nitive management of the airway involves endotracheal intubation. Even under the best of circumstances, however, there are times when the Paramedic cannot intubate a patient. Therefore, it is important for the Paramedic to have a plan and alternatives. The Advanced Airway Management Algorithm, used along with the Paramedic’s skills, should provide the Paramedic with the tools necessary to perform defi nitive advanced airway management. Key Points: • An endotracheal tube (ET tube) offers direct • ET tubes are sized based on their internal diameter access to a patient’s airway. Even though it does and range from 2.5 to 10.0 mm. Selection of size not absolutely prevent aspiration, it signifi cantly for pediatric patients can be done based on age, decreases the rates of aspiration. estimating the diameter of the patient’s small fi nger or nare or using length-based tapes. • The endotracheal tube also allows the Paramedic to perform intermittent positive pressure ventilation, • Nasotracheal intubation is the placement of an tracheobronchial suctioning, and medication endotracheal tube through the patient’s nostril and delivery. Perhaps the greatest advantage over into the trachea. Blind nasotracheal intubation can non-intubated ventilation is that it does not cause only be performed on a breathing patient. Nasal tubes gastric insuffl ation. are softer and more pliable than standard tubes to allow them to curve more easily along the posterior • Disadvantages of endotracheal intubation include oropharynx. They may have a small ring or “trigger” the fact that air is no longer fi ltered, warmed, or that is used to curve the tip of the tube anteriorly. humidifi ed by the upper airway. Complications • Although not a “sterile” technique, airway of intubation include bleeding, laryngospasm, management should at least be a “clean” laryngeal swelling, mucosal necrosis and erosion, technique and efforts should be made to minimize and vocal cord damage. Patients are also at risk for contamination of the endotracheal tube. barotrauma and infections related to ventilation devices. Overventilation of the lungs can increase • Preparation of the endotracheal tube includes intrathoracic pressures, causing a decrease in applying lubricant, checking the cuff for leaks, and systemic blood pressures. placing a stylet. Several other sizes of ET tubes should also be available. • The endotracheal tube provides a conduit for • The laryngoscope is the primary device used to oxygenation and ventilation between the patient’s visualize the larynx. The handle serves as a power lungs and the ventilator (person or machine). source and grip point for the Paramedic and the • blades are designed to provide a view of laryngeal The primary components of an endotracheal tube opening through control of the tongue and the are the tube, the cuff that infl ates to secure and epiglottis. The two most commonly used styles of seal the tube below the level of the cords, and the blades are the Macintosh and Miller blades. 15 mm adapter that can be connected to a BVM or ventilator. Pediatric tubes are often uncuffed. • The Macintosh blade is a curved blade with a large fl ange and fl at surfaces. Common sizes range from • Common features of the endotracheal tube include 1 to 4. The tip of the blade is intended to fi t into length markings in centimeters and a beveled distal the vallecula and elevate the epiglottis via the end with a “Murphy eye.” hyoepiglottic ligament. 466 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. • The Miller blade is a straight blade with common intubation. Conversely, an esophageal intubation sizes from 00 to 4. The straight blade is designed to may be mistaken for an endotracheal intubation open a conduit to the larynx on the right side of the with gastric insuffl ation, leading to ingestion of mouth and hold the tongue in the midline to the left carbonated beverages and antacids. side of the mouth. The tip of the blade is designed to capture and lift the epiglottis. • The least expensive, and probably most commonly used, device for measuring end-tidal carbon dioxide • Selecting the appropriate size and type blade is the colorimetric device. These devices are simply depends on the size of the patient and the clinical encapsulated pieces of litmus paper over which the context. Miller blades are typically used for children exhaled breath fl ows. A color change indicates CO2 under 5 years of age and for trauma patients. is being exhaled and the ET tube is properly placed. • The blade is attached to the crossbar of the handle • Capnometry devices give a single, numeric peak until it clicks into place. Once the blade is rotated reading of the exhaled CO2. End-tidal capnography in place, the light should activate. The Paramedic provides the Paramedic with the numeric values for should make sure the light is white in color, the both the peak and trough ETCO2 levels and displays bulb is tightly screwed into the blade, and the light a graph of the exhalation curve. is steady and bright in intensity. • Supraglottic airway devices or blind insertion airway • The stylet is placed inside an endotracheal tube devices (BIADs) include the King LTS-D airway, the to provide rigidity and can be shaped to maximize esophageal-tracheal Combitube (ETC or Combitube), control of its distal tip and improve the chances of and the laryngeal mask airway (LMA). The laryngeal successful placement. It is important that the distal mask airway, in essence, moves the mask of face- end of the stylet not extend beyond the Murphy’s mask ventilation from the face to the opening of the eye on the endotracheal tube. A stylet is generally larynx. The mask should be infl ated to assure that not used for nasotracheal intubations. it holds air and the distal tips of the mask should be • lubricated to improve ease of placement. There are numerous devices for securing the endotracheal tube. Regardless of the device, it • The esophageal-tracheal Combitube (ETC) is a is important that the endotracheal tube not be double-lumen device with two separate and distinct able to move. Because the risks of accidental tube lumens that are placed in the esophagus (90% to 99% dislodgment during patient movement are high, of the time). However, tracheal placement of the a cervical collar can be applied to the patient to ETC is possible. Each has two cuffs: a large proximal minimize neck extension and fl exion. cuff designed to seal the hypopharyngeal portion • of the airway and a smaller distal cuff designed to To confi rm the proper placement of an ET tube, the seal the esophagus or trachea, depending on the Paramedic should have a stethoscope immediately placement. available for the auscultation of lung sounds. An esophageal detection device should also be • No special equipment is needed for supraglottic available to use to confi rm endotracheal tube airway devices. It has been demonstrated to placement. cause less C-spine movement than conventional • endotracheal intubation. The devices are easy to End-tidal carbon dioxide (ETCO2) measurement place and may be a useful alternative when patients and monitoring has become the gold standard for are in unusual positions. Disadvantages include the both confi rming endotracheal tube placement inability of medication administration and deep and monitoring patient status, ventilation, and suctioning of the lungs. An elastic gum bougie is a continuing tube placement. A limit to ETCO2 is small diameter, semi-rigid device that is directed that, in patients in cardiac arrest, the lack of through the vocal cords and into the trachea to carbon dioxide may be mistaken for an esophageal serve as a guide for an endotracheal tube. The Intubating Airway Management 467 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. endotracheal tube is then threaded over the Paramedic can utilize the modifi ed jaw-thrust proximal end and advanced into the trachea. maneuver or BURP technique to create ideal • positioning. Lighted stylettes are |
essentially malleable stylettes with a bright light source. When placed in the • The fi nal step in patient preparation is the trachea, provide a bright, well-circumscribed light appropriate use of sedatives and paralytic agents. that can be seen in the midline of the trachea. • The process for intubation can be broken down into • One of the other advantages, besides illumination, four steps: of the close proximity of the trachea to the anterior 1. Visualizing the vocal cords neck is that surgical airway management can be 2. Passing the endotracheal tube achieved rapidly and effectively. A true or classical 3. Confi rming endotracheal tube placement surgical airway is a relatively simple process that 4. Securing the endotracheal tube involves the identifi cation of the cricothyroid membrane, cutting a hole through the cricothyroid • Endotracheal intubation is a team activity, and the membrane, and placing an endotracheal tube or Paramedic may ask other EMS personnel to provide cuffed tracheostomy through that hole. cricoid pressure, BURP technique, or external laryngeal manipulation. • It is important to note that a surgical airway should be performed only if that patient cannot • The tip of the MacIntosh blade is designed to fi t into be intubated, a rescue device cannot be placed, the vallecula. When lifted anteriorly and inferiorly, and the patient cannot be ventilated with standard the blade lifts the hyoepiglottic ligament, which face-mask techniques. pulls the epiglottis anteriorly and reveals the vocal cords. • Needle cricothyrotomy ventilates the lungs using special high-pressure devices after a needle • The Miller blade is designed to pin the epiglottis device is used to introduce a catheter or against the base of the tongue anteriorly and tracheostomy tube. provide a straight-on view of the vocal cords. The tip of the blade lifts up the epiglottis to reveal the • To prepare the patient for intubation, the vocal cords. Paramedic should fi rst assess the level of diffi culty before attempting airway management. The • The Cormack-Lehane grading system grades the 3-3-2 rule and the “LEMON” law are two methods view of the glottic opening by how much is occluded for assessing a patient’s airway along with the by the tongue. Grade I is a clear view of the entire Paramedic assigning a Mallampati score. glottic opening while IV is visualization of the tongue or soft palate only. • When positioning the patient for endotracheal intubation, the sniffi ng position is considered to be • To assist the Paramedic in visualizing the cords, an the intubation position of choice. Both the sniffi ng assistant can use a fi nger or rigid suction catheter to position and head-tilt, chin-lift maneuvers help hook and retract the corner of the patient’s mouth. to align the oral, pharyngeal, and laryngeal axes, • Suctioning itself may be used to improve allowing for the best view during intubation. visualization and minimize airway and soft tissue • For patients who are unable to lie fl at, the Head trauma. Elevated Laryngoscopic Position (HELP) may • Magill forceps are used to remove large foreign be used. bodies occluding the airway. If the foreign body is • Neck fl exion and head extension are contraindicated subglottic and cannot be grasped with the Magill in trauma patients. While providing in-line forceps, it should be pushed into a mainstem stabilization from the inferior direction, the bronchus with an endotracheal tube. The tube is 468 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. then withdrawn to above the carina to allow at • The endotracheal tube placement is confi rmed in least one lung to be ventilated. the same manner as in an orotracheal intubation. • If the cords are closed due to laryngospasm or only • If the intubation fails, the Paramedic should assess partially open, the Paramedic should apply gentle reasons why it failed and make attempts to correct pressure to the lip of the tube bevel between the it before attempting intubation a second time. cords, which may cause them to relax suffi ciently to pass the tube. The tube or the stylet should not be • A digital intubation is a blind technique that is “forced” between the cords. useful not only for supine patients, but patients who • are in a sitting position or for whom access to the When the fi rst breath is delivered, the epigastrium head is limited. should be auscultated. Loud noises over the epigastrium with abdominal distention and no chest • The elastic gum bougie is placed under direct movement strongly suggest esophageal placement. visualization with a laryngoscope. The tip of • the bougie is advanced anterior to the posterior Diminished or absent lung sounds on the left are arytenoids until the tip “clicks” along the tracheal often due to the endotracheal tube being placed in rings. An endotracheal tube is threaded over the the right mainstem bronchus. external end of the bougie and advanced into the • Once the tube position is assessed by auscultation, trachea. the Paramedic should assess placement using end- tidal carbon dioxide measurement. The Paramedic • When the Paramedic is performing translaryngeal should look for readings of 30 to 40 with a wave that illumination with a lighted stylet, the stylet is rises and falls appropriately with ventilation and has advanced until a focal, bright midline glow is visible a consistent shape. at the level of the larynx. • For patients without spontaneous circulation, the • Supraglottic airway devices provide a method of at Paramedic should use an esophageal detector device least partially securing the airway in the diffi cult- for confi rmation of endotracheal tube placement. to-intubate patient. The three most commonly used devices, as described earlier, are the • The mnemonic DOPE can help the Paramedic 1. King LTS-D airway remember the causes of problem intubations. 2. The laryngeal mask airway • 3. The esophageal-tracheal Combitube It is important that the tube position be assessed after each move. • When performing a needle cricothyroidotomy, • proper technique requires good landmark Nasal intubation is indicated for patients who are identifi cation and care in ventilation to prevent diffi cult to access or, due to their disease process, overpressurization. are likely to experience rapid decompensation if they lay fl at. • Percutaneous devices include the direct insertion of • a larger device with a removable trochar, insertion Contraindications to nasotracheal intubation include of a small device with subsequent dilators, or use of apnea, evidence of basilar skull fracture, or inability a Seldinger (over the wire) technique. to pass the tube through a nare. • • Post-intubation care involves ventilating, monitoring The tube should be placed in the most patent nare the airway, placing a nasogastric or orogastric tube, with the tip of the tube parallel to the fl oor of the and performing tracheobronchial suctioning. nose. A Beck Airway Airfl ow Monitor (BAAM) should be used to detect breath sounds. The tube is then • Automatic transport ventilators can provide the advanced through the cords during inspiration until Paramedic consistent and predictable ventilation; approximately 2 cm protrude from the nose. control over volume, rate, and expiratory pressures; Intubating Airway Management 469 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. and high-pressure alarms. Disadvantages include • Face-mask ventilation skills are important in the its dependence on an oxygen source to provide management of critically ill children. ventilation. • The Paramedic should note that the pediatric • To reduce the risk of vomiting or aspiration caused patient has minimal respiratory reserve. Prolonged by gastric infl ation, the Paramedic should place an intubation attempts put the patient at risk for rapid orogastric or nasogastric tube. desaturation. • Soft, long, and thin suction catheters are used for • The LMA should be the rescue airway of choice for tracheobronchial suctioning. pediatric patients in whom orotracheal intubation • cannot be performed. Any patient experiencing a traumatic injury is at risk for trauma to the airway itself. • Needle cricothyroidotomy can also be performed on • children of all ages. With the assessment fi ndings of a fl ail chest injury or tension pneumothorax, the conditions should be • To minimize peak pressures, short inhalation times treated during airway and ventilatory management. and a smaller catheter should be used to deliver • appropriate volumes, and to minimize the risk of Early and aggressive use of medication-facilitated acute barotrauma. and rapid sequence intubation techniques to secure these patients’ airways is warranted with trauma patients who have lost their airway refl exes and are combative, but not to be obtunded. Review Questions: 1. Weigh the advantages and disadvantages of 6. What does continuous end-tidal capnography endotracheal intubation. offer the Paramedic? 2. Describe the components of an endotracheal 7. For each of the following blind insertion and nasotracheal tube. airway devices, describe the preparation and 3. Create a chart that compares and contrasts the technique for insertion: King LTS-D airway, Miller blade with the Macintosh blade. the esophageal-tracheal Combitube (ETC or 4. A Paramedic is presented with a patient Combitube), and the laryngeal mask in severe respiratory distress who is airway (LMA). decompensating quickly. How would the 8. How can the use of an elastic gum bougie make Paramedic quickly and effi ciently assess the the fi rst attempt at endotracheal intubation the patient’s airway? best attempt? 5. The Paramedic decides that the patient 9. The process for intubation can be broken down requires endotracheal intubation. While the into four steps. Describe each step. team members are performing bag-valve- 10. Why is it important for the Paramedic to mask ventilations with cricoid pressure, what reassess tube position each time the patient equipment must the Paramedic have prepared, is moved? What are some causes of tube checked, and ready before breaking the displacement, and how would the Paramedic mask seal? know that it is out of place? 470 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. 11. If attempts to intubate and place a BIAD fail, done to remedy this situation and improve the what two alternatives remain for the Paramedic? patient’s oxygenation and ventilation? 12. Describe the technique for landmark 14. Who should receive an orogastric or nasogastric identifi cation for a needle cricothyroidotomy. tube? How is each prepared for placement in 13. After intubation, the Paramedic notices copious the patient? thick secretions, decreased O2 saturation, and 15. What considerations must be made for poor ventilatory compliance. What can be intubating the pediatric patient? Case Study Questions: Please refer to the Case Study at the beginning of the 2. What could they have done to help prevent the chapter and answer the questions below: patient’s vomiting? 1. Why were the emergency medical responders 3. What indications did the Paramedic have to experiencing problems with the patient intubate the patient? vomiting? References: 1. Hazinski MF, eds. PALS Provider Manual. Dallas: AHA; 2001:100. 10. Zaleski L, Abello D, Gold MI. The esophageal detector device: 2. Vilke GM. Estimation of pediatric patient weight by EMT-Ps. does it work? Anesthesiology. 1993;79(2):244–247. J Emerg Med. 2001;21(2):125–128. 11. Tanigawa K, Takeda T, Goto E, Tanaka K. Accuracy and reliability of 3. Hofer CK. 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Can J Anaesth. 1989;36(6):624–628. respiratory therapists. Ann Emerg Med. 1994;24(2):260–263. 48. Jacobs HB. Transtracheal catheter ventilation: clinical experience 30. Levitan RM, Ochroch EA, Stuart S, Hollander JE. Use of the in 36 patients. Chest. 1974;37(6):36–40. intubating laryngeal mask airway by medical and nonmedical 49. Weymuller EA, Paugh D, Pavlin EG, et al. Management of personnel. Am J Emerg Med. 2000;18(1):12–16. the diffi cult airway problems with percutaneous transtracheal 31. Agro F, Frass M, Benumof JL, Krafft P. Current status of ventilation. Ann Oto Rhino Laryngol. 1987;96(6):34. the CombitubeTM: A review of the literature. J Clin Anesth. 50. Koay CK. Diffi cult airway management—analysis and management 2002;14(4):307–321. in 37 cases. Singapore Medical Journal. 1998;39(33):112–114. 32. Gaitini LA, Vaida SJ, Mostafa S, et al. The Combitube in elective 51. Rose DK, Cohen MM. The airway: problems and predictions in surgery: a report of 200 cases. Anesthesiology. 2001;94(1):79–82. 18,500 patients. Can J Anaesth. 1994;41(5):372–383. 33. Frass M, Rodler S, Frenzer R, et al. Esophageal tracheal 52. McIntyre JRW. The diffi cult intubation. Can J Anesth. Combitube, endotracheal airway, and mask: comparison of 1987;34(2):204–213. ventilatory pressure curves. J Trauma. 1989;29(11):1476–1479. 53. Jones AEP, Pelton DA. An index of syndromes and their 34. MacIntosh RR. An aid to oral intubation. BMJ. 1949;1(4591):28. anesthetic implications. Can Anaesth Soc J. 1976;23(6):207–226. 35. McGill JW, Vogel EC, Rodgerson JD. Use of the gum elastic 54. Mathew M, Hanna LS, Aldrete JA. Preoperative indices bougie as an adjunct for orotracheal intubation in the emergency to anticipate a diffi cult tracheal intubation. Anaesth Analg. department [Abstract]. Acad Emerg Med. 2000;7(5):526. 1989;68(2 Supplement):S187. 36. Dogra S, Falconer R, Latto IP. Successful diffi cult intubation. 55. Murphy MF, Walls RM. The diffi cult and failed airway. In: Tracheal tube placement over a gum elastic bougie. Anesthesia. Walls RM, Luten RC, Murphy MF, Schneider RE, eds. Manual 1990;45(9):774–776. of Emergency Airway Management. Philadelphia: Lippincott 37. Gataure PS, Vaughan RS, Latto IP. Simulated diffi cult intubation. Williams and Wilkins; 2000:31–39. Comparison of the gum elastic bougie and the stylet. Anesthesia. 56. Adnet F, Borron S, Lapostolle F, Lapandry C. The three axis 1996;51(10):935–938. alignment theory and the “sniffi ng position”: Perpetuation of an 38. Moscati R, Jehle D, Christiansen G, et al. Endotracheal tube anatomic myth? Anesthesiology. 1999;91(6):1964. introducer for failed intubations: a variant of the gum elastic 57. Bannister FB, MacBeth RG. Direct laryngoscope and tracheal bougie. Annals Emerg Med. 2000;36(1):52–56. intubation. Lancet. 1944;55(2):651–654. 472 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. 58. Adnet F, Baillard C, Borron SW, et al. Randomized study 69. Grove P. Endotracheal tube stability in the resuscitation comparing the “sniffi ng position” with simple head extension for environment. Aust Crit Care. 2000;13(1):6–8. laryngoscopic view in elective surgery patients. Anesthesiology. 70. Landsman IS. The laryngeal mask airway. Int Anesthes Clin. 2001;95(6):836–841. 1997;35(3):49–65. 59. Benumof JL. Comparison of intubating positions: the end point 71. Brofeldt BT, Panacek EA, Richards JR. An easy cricothyrotomy should be measured. Anesthesiology. 2002;97(3):750. approach: the rapid four-step technique. Academic Emergency 60. Benumof JL. Patient in “sniffi ng position.” Anesthesiology. Medicine. 1996;3(11):1060–1063. 2000;93(5):1365–1366. 72. Gaughan SD, Ozaki GT, Benumof JL. Comparison in a lung 61. Hochman II, Zeitels SM, Heaton JT. Analysis of forces and model of low and high fl ow regulators for transtracheal jet position required for direct laryngoscopic exposure of the anterior ventilation. Anesthesiology. 1992;77(1):189–199. vocal folds. Ann Oto Rhino Laryn. 1999;108(8):715–724. 73. Sullivan DM. Myths in trauma. In: Ferrera PC, Colucciello SA, 62. Takahata O, Kubota M, Mamiya K, et al. The effi cacy of the Marx JA, Verdile VP, Gibbs MA, eds. Trauma Management: An “BURP” maneuver during diffi cult laryngoscopy. Anesthesia and Emergency Medicine Approach. St. Louis: Mosby; 2001: Analgesia. 1997;84(2):419–421. 702–709. 63. Henderson JJ. The use of paraglossal straight blade laryngoscopy 74. Brownstein D, Shugerman R, Cummings P, Rivara F, Copass M. in diffi cult tracheal intubation. Anaesthesia. 1997;52(6):552–560. Prehospital endotracheal intubation of children by Paramedics. 64. Schneider RE. Basic airway management. In: Walls RM, Luten Ann Emerg Med. 1996;28(1):34–39. RC, Murphy MF, Schneider RE, eds. Manual of Emergency 75. Aijian P, Tsai A, Knopp R, et al. Endotracheal intubation Airway Management. Philadelphia: Lippincott Williams and of pediatric patients by Paramedics. Ann Emerg Med. Wilkins; 2000:43–57. 1989;18(5):489–494. 65. Brunnings W. Autoscopy by counterpressure. In: Phillips W, 76. Stratton SJ, Underwood LA, Whalen S. et al. Prehospital ed. Direct Laryngoscopy, Bronchoscopy, and Esophagoscopy. pediatric intubation: a survey of the United States. Prehospital London: Balliere, Tindall, and Cox; 1912:110–115. and Disaster Medicine. 1993;8(4):323–326. 66. Zeitels SM, Vaughn CW. “External counterpressure” and 77. Pointer JE. Clinical characteristics of Paramedics’ performance “internal distention” for optimal laryngoscopic exposure of of pediatric endotracheal intubation. Am J Emerg Med. the anterior glottic commissure. Ann of Oto, Rhino, and Laryn. 1989;7(4):364–366. 1994;108(8):669–675. 78. Gauche M, Lewis RJ, Stratton SJ, et al. Effect of out-of-hospital 67. Ochroch AE, Levitan RM. A videographic analysis of laryngeal pediatric endotracheal intubation on survival and neurological exposure comparing the McCoy levering laryngoscope blade outcome: a controlled clinical trial. JAMA. 2000;283(6):783–790. and external laryngeal manipulation. Anesthesia and Analgesia. 79. Mason DG, Bingham RM. The laryngeal mask airway in 2001;92(1):267–270. children. Anesthesia. 1990;45(9):760–763. 68. Benumof JL, Cooper SD. Qualitative improvement in 80. McGinn G, Haynes SR, Morton NS. An evaluation of the laryngoscopic view by optimal external laryngeal manipulation. laryngeal mask airway during routine paediatric anaesthesia. J Clin Anesth. 1996;8(2):136–140. Paediatr Aneasth. 1993;3(1):23–28. Intubating Airway Management 473 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. KEY CONCEPTS: Upon completion of this chapter, it is expected that the reader will understand these following concepts: • Differentiating between medication-facilitated and rapid sequence intubation • Physiology of neuromuscular blockers including differentiation between depolarizing and non-depolarizing neuromuscular blocking agents • Patients who are candidates for paralytic agents • The protective effect of preoxygentaion • Knowing the “Nine P’s of RSI” Case Study: It was prom night. Although many police agencies presented material regarding the dangers inherent in partying, the young people in the Honda Civic didn’t get the message. Their car hit a pole at a fast speed and the driver had head and chest injuries from the impact. His breathing was impaired and he was combative. The closest trauma center was 35 minutes away by air. The Paramedics made the decision to intubate the driver prior to the helicopter’s arrival. 474 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial |
review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Medication-Facilitated Intubation 475 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. OVERVIEW Although medication-facilitated and rapid sequence intubation have been relative newcomers to paramedicine, they have become very useful tools in airway management. This chapter outlines the key differences in sedative agents used for intubation and the mechanisms of action for both depolarizing and non-depolarizing neuromuscular blockers. Not all patients should receive paralytic agents. This chapter will examine the issue of whether or not paralytics should be used in the prehospital environment. This review will then be followed by a discussion of the medications used for medication-facilitated and rapid sequence intubation. The “Nine P’s of RSI” will be reviewed, as well as patient assessment and the decision to administer paralytics. Medication-Facilitated Intubation the Paramedic takes a patient with an ability to maintain his airway and ventilate and then eliminates those abilities. Paramedics have always done an excellent job of taking pro- Extraordinary clinical judgment is necessary for anyone in cedures and techniques developed for the in-hospital setting the position to paralyze a patient. Nonetheless, there is clear and adapting them for use in the prehospital environment. evidence that patients who receive paralytics have better out- In addition, many medications have been validated in the comes than those who receive only sedatives.2 When used prehospital setting, sometimes before being validated in properly, sedation and paralysis enable otherwise impossible the hospital environment. It is therefore no surprise that in the intubations and eliminate the need for face-mask ventilation arena of airway management, the techniques of medication- and its associated complications (aspiration, gastric disten- facilitated and rapid sequence intubation have been trialed tion, etc.). Paralytics, therefore, play an important role in and applied in the prehospital setting. As with some other managing patients’ airways. techniques, however, the question of whether Paramedics It is important to recognize that if a Paramedic is going should perform these skills was not nearly as well researched to perform rapid sequence intubation with paralytics, then he as whether EMS providers could perform them. Only recently or she must be properly trained and profi cient in adequate has that question been addressed. alternative airway techniques. Although proper patient selec- Medication-facilitated intubation is not a new tech- tion should minimize the risk of paralyzing a patient who can nique. In fact, it has been used for decades in the operating neither be intubated nor ventilated, the risk exists that this room and emergency department settings. The use of adjunc- situation might occur. If it does, an alternative is mandatory tive medications, like any other adjunct to intubation, has to prevent hypoxic complications. Although the question of been (and should be) seen as one more tool to protect patients whether or not Paramedics should be using paralytics may and improve their quality of care. Broadly speaking, medica- not be clearly answered, the fact remains that many provid- tions for airway management can be divided into those that ers are using paralytics and therefore it is incumbent on the provide sedation and those that cause muscular paralysis. Paramedic to be familiar with this tool. In general, many more intubations are performed with sedatives alone. Many EMS agencies and medical direc- tors are more comfortable with sedative-facilitated intu- Prehospital Provider Use of Paralytics bation than with the use of paralytics. Using a variety of The use of paralytic agents to facilitate intubation is a long- sedative agents, Paramedics are able to make patients more standing source of controversy among Paramedics and medi- comfortable, less anxious, and amnestic to the events of the cal directors. The research for and against the use of paralytics intubation. Some newer agents such as etomidate are able has not clearly demonstrated that paralytics have a defi nitive to provide suffi cient sedation to often eliminate the need role in daily EMS practice. Conversely, there is strong evi- for paralytics.1 Sedative-facilitated intubation is therefore dence that paralytics can be used safely by selected groups of becoming a common approach to intubation of the non- Paramedics providing that they have adequate training, good cardiac arrest patient. medical direction and medication utilization review, and a Paralytic agents can be some of the most dangerous rescue device. medications Paramedics can administer. By providing and One of the largest studies in support of prehospital use performing the emergency care which causes paralysis, of succinylcholine is a 20-year retrospective study by Wayne 476 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. and Friedland.3 Spanning 20 years of practice, this retro- Pharmacological Adjuncts spective review evaluated 1,657 consecutive intubations. for Intubation Overall, a 95.5% successful intubation rate was found. There was a 0.3% unrecognized esophageal intubation rate As was discussed previously, the pharmacological agents that that was almost eliminated with the addition of capnography facilitate intubation can be divided into those that provide and esophageal detector device use. The remaining patients sedation and those that cause paralysis. In addition, adjunc- who could not be intubated were successfully managed with tive medications that are often used in RSI include vagolytics alternative methods. This study provides strong support for (atropine) and lidocaine. It is important to be familiar with the prehospital use of paralytics. Similarly, a retrospective all of these medications as they are used in the setting of study by Hedges et al.4 conducted 10 years before Wayne intubation. and Friedland’s study had suggested a similar effi cacy and Sedatives safety profi le for succinylcholine-assisted intubation. Sev- eral other small studies have also addressed the issue, each Sedative agents are medications that are used to decrease a demonstrating that out-of-hospital providers can success- patient’s level of consciousness, cause muscular relaxation, fully perform rapid sequence intubation.5–7 and cause amnesia to the intubation. There are a number A more recent study by Ochs et al.8 has clarifi ed some of different sedatives with varying hemodynamic effects, questions concerning the utility of paralytic-assisted intuba- respiratory effects, and side effects. It is important that the tions. Their study, which focused on head injured patients P aramedic be an expert on the agents that he or she will use. with otherwise unmanageable airways, demonstrated an 84% It is important to recognize that no one agent is ideal for all successful intubation rate. Of the remaining patients, all but patients. Therefore, familiarity with a number of agents and one were successfully managed with a Combitube. The last their characteristics allows for an educated decision about patient was successfully managed with BVM ventilation. which agent to use. Four of the most commonly used agents Although this study certainly indicates that prehospital use of (and representative of the major classes of prehospital agents) succinylcholine will result in some degree of airway manage- are midazolam (a benzodiazepine), etomidate, ketamine, and ment in the vast majority of patients, the intubation failure fentanyl (a narcotic). Understanding these medications and rate of 16% raises concerns about whether or not fi eld EMS others in their respective classes will allow the Paramedic to providers get enough experience with routine intubations to select the most appropriate medication for a patient. expertly manage every airway with which they are faced. Midazolam Nonetheless, the study population is certainly one in whom airway management has been demonstrated to be critical.9,10 As a class, benzodiazepines are probably the most com- Furthermore, the use of a supraglottic airway device (dis- monly used medications for sedation in the emergency air- cussed in Chapter 23) is a clearly recognized and appropriate way management arena. This use comes from familiarity alternative to airway management in the patient with an oth- and a history of safe and effective utilization. Midazolam erwise unmanageable airway. This study, therefore, provides is chosen as a representative of this class because it is short support for the prehospital use of paralytics for critically ill acting, shares the characteristics of the other benzodiaz- trauma patients. epines, and has been studied in the prehospital environment Consistently, the most important factors in the success of as a sole agent to facilitate intubation.2,11 Other benzodiaz- RSI programs have been the involvement of an active medi- epines that are used for intubation include diazepam and cal director, review of each intubation, and strong educational lorazepam. components. If the decision is made to add RSI to an agency’s The benzodiazepines are best known for their ability to airway management options, it must be made with an effec- provide excellent amnesia. Other effects include sedation, tive monitoring program in place and with the recognition muscular relaxation, CNS relaxation, treatment of active that, if the program is not performing well, it must be stopped seizures, and anxiolysis. Midazolam may also decrease and evaluated. intracranial pressure. They work directly on a benzodiaz- epine receptor in the brain. The onset of action relates to how Medication-Facilitated quickly the agents pass into the brain, with midazolam having an onset of action of 30 to 60 seconds. The benzodiazepines and Rapid Sequence Intubation are metabolized by the liver; the half-life for midazolam is The use of medication-facilitated and rapid sequence intuba- 1.5 to 2.5 hours. tion has the potential to greatly increase a Paramedic’s ability The greatest diffi culty in using midazolam for sedation to successfully intubate a patient. To use these tools effec- is the wide variability in patient response to the agent. Doses tively, it is important to understand the medications, how they as low as 1 mg have caused apnea in some patients while function, and their indications and contraindications. The fol- others require up to 0.3 mg/kg to achieve adequate sedation. lowing covers the most important points of the medications In g eneral, male patients and elderly patients require the from the Paramedic’s perspective. smallest doses. Medication-Facilitated Intubation 477 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. The most signifi cant complication associated with mida- Other than drug allergy, there are no true contraindica- zolam is a dose-related vasodilation and myocardial depres- tions to the use of etomidate. It is not routinely used in chil- sion. Therefore, although midazolam has been routinely used dren under 10 years of age. It should be used with caution in in trauma patients and others with potential for hypotension the elderly (as should any sedative agent), and the dose can be and hypovolemia, it does pose a risk for converting a patient titrated to effect in hemodynamically unstable patients. in compensated shock to a state of decompensated shock. Etomidate is generally dosed at 0.2 to 0.3 mg/kg in Indications for midazolam, therefore, are broad, although the adult patient. A standard intubating dose in an average- it must be used with caution in the elderly and in patients at risk sized adult is 20 mg. A dose of 0.1 mg/kg is often used for for signifi cant cardiovascular decompensation. Glaucoma has procedural sedation and is a good starting point for elderly been identifi ed as a contraindication to benzodiazepine use. patients. Because there is minimal drug accumulation, it can The dosing for midazolam, because of the diffi culty in be redosed if needed. Typical time |
to onset is 1 to 2 minutes. predicting response, requires some degree of titration. The The lack of hemodynamic effects, the cerebroprotective standard dose is 0.2 mg/kg, although this varies from 0.05 effect, and the relative ease of use have made etomidate the to 0.3 mg/kg. A dose of 0.1 mg/kg, followed by additional fi rst choice of many Paramedics for trauma airway manage- doses as needed, will result in a relatively safe side effect pro- ment. It is also an excellent choice for the unstable medical fi le. The onset of action is about 2 minutes. The variability in patient. It must always be used in conjunction with a second dose response, however, may result in a patient who is under- sedative agent once the intubation is complete. sedated during paralysis. This is manifested by hypertension and tachycardia. If these hemodynamic changes are noted, Ketamine the patient should be given additional sedation. Ketamine is a dissociative anesthetic with several unique Midazolam is also useful as a post-intubation sedative. properties. A derivative of PCP, ketamine provides excellent Repeated doses of 20% to 50% of the original dose every 30 amnesia, analgesia, and anesthesia during procedures and to 60 minutes as dictated by the patient’s level of conscious- intubation. Most notably, however, it has minimal respiratory ness and cardiovascular parameters should provide excellent depression even at very high doses. In addition, it increases sedation. heart rate and blood pressure through the release of cate- cholamines. Finally, it has the pulmonary effect of reducing Etomidate bronchospasm through smooth muscle relaxation.13 Etomidate is a newer agent that functions primarily as a hyp- Ketamine’s properties have made it an excellent “spe- notic, although it also is an excellent amnestic. Its increasing cialty” sedative in airway management. Its bronchodilatory popularity in the emergency airway management setting is properties make it an excellent choice for the asthmatic because it has minimal hemodynamic effects and only mod- patient. In addition, hypotensive patients without evidence of erate respiratory depression at induction doses. In addition, it head injury benefi t from the catecholamines that are released. provides excellent relaxation and often does not require the Its effi cacy in the pediatric population is also clearly estab- addition of a paralytic to achieve an intubation, thus making lished.16 Although an IV would clearly be preferable in the it a good agent when paralysis is contraindicated.1,12 emergency airway management setting, ketamine can be Although the hemodynamic stability associated with given IM as well. etomidate is perhaps its greatest asset, it also has a cerebro- There are patients in whom ketamine is not a good agent protective effect. It both attenuates an increased ICP and for induction. Research in the early 1970s reported an increase decreases the negative effects of laryngoscopy.13 in intracranial pressure associated with the use of ketamine.17 Etomidate is not without side effects, however. Transient Although recent research brings this fi nding into question,18 muscle jerks are common and trismus has been reported.14 the current standard is to avoid the use of ketamine in patients In addition, many patients experience nausea and vomit- with head injuries or those at risk of increased intracranial ing, although this more often occurs on awakening and is pressure. In addition, the catecholamines released during ket- therefore less important in the airway management setting.15 amine administration increase myocardial oxygen demand, Finally, patients may experience burning at the site of infu- making this a poor sedative for the patient with known or sion; this can be decreased by using a large vein and a rapid suspected coronary artery disease. Drug allergy, as always, is IV fl uid rate. Etomidate, when used as a continuous drip, can also a contraindication. cause adrenal suppression. This has not been reported in the Ketamine has a number of side effects, only a few of single-dose setting of airway management. which are relevant to airway management. Increased saliva- It is important to recognize that the hypnotic effects of tion is associated with ketamine use, particularly in pediat- etomidate end approximately 20 to 30 minutes after admin- ric patients. Prior administration of atropine can minimize istration. When used with a long-acting paralytic such as this effect. Although patients usually experience relaxation vecuronium, it is critical that additional sedation (usually after ketamine administration, some will become restless in the form of a benzodiazepine) be administered after the and move purposelessly. Finally, ketamine is associated with intubation to assure that the patient is not awake and remains “emergence reactions” or hallucinations. These occur more paralyzed. commonly in adults than in children and should not be an 478 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. issue in emergency airway management as the patient will be push for sedation. If morphine is used, the Paramedic should sedated, usually with a benzodiazepine, after the intubation expect a greater hemodynamic response (e.g., hypotension). is complete. The onset of action is usually rapid (30 to 60 seconds) and Ketamine is given in doses of 1 to 2 mg/kg IV or, if given the duration of fentanyl is typically 22 to 30 minutes. Narcot- IM, 2 to 4 mg/kg. The onset of action is typically 30 seconds ics may be redosed in 22 to 30 minutes as needed. They may to a minute and can be recognized by the roving eye move- be used for short-term sedation after an intubation, although ments called nystagmus and the awake but unaware appear- longer-acting agents such as benzodiazepines are preferred. ance of the patient. The effect of ketamine typically lasts up to 10 minutes for intravenous administration and up to Neuromuscular Blocking Agents 25 minutes for intramuscular administration. (Paralytics) Although somewhat of a specialized drug, ketamine is an Neuromuscular blocking agents are medications that block important drug in the airway management of selected patients. transmission of nerve impulses to skeletal muscle at the Its minimal respiratory effects, bronchodilation, and positive neuromuscular junction. When a nerve impulse reaches the hemodynamics make it a useful medication for sedation. neuromuscular junction, the molecule acetylcholine, a neu- Fentanyl rotransmitter, is released into the synapse from the presynap- tic membrane of the nerve. The acetylcholine moves across Narcotics, a class of drugs known for their ability to induce the synapse to the postsynaptic membrane of the muscle. a profound state of sedation, as a general rule, are rarely There it binds to receptors and causes the muscle to contract used as the sole sedative agents in emergency airway man- (Figure 24-1). Normally, the contraction stops when the ace- agement. Nonetheless, they may be the only agent a prehos- tylcholine is broken down by acetylcholinesterase. pital provider has available. In addition, they are often used Skeletal muscle paralytics block the binding of ace- adjunctively in airway management, making them important tylcholine to the receptors on the postsynaptic membrane. medications with which to be familiar. Narcotics provide There are two major classes of neuromuscular blockers: analgesia and hypnosis as well as some degree of amnesia. In depolarizing agents and non-depolarizing agents. The main addition, they attenuate the increased ICP that is a refl exive difference between the two is whether the medication binds response to laryngoscopy.13 Although fentanyl is used as a to the receptor and causes a muscular contraction (a depolar- sole indication agent at very high doses (22 to 30 µg/kg) in izing agent) or simply blocks acetylcholine from binding to the operating room, lower doses of narcotics can be used in the receptor without causing the receptor to activate (a non- emergency airway management to achieve some degree of depolarizing agent). There is only one depolarizing agent that patient sedation. is commonly used (succinylcholine) while there are multiple Fentanyl is a synthetic opioid that is highly potent. It is non-depolarizing agents. known for not causing histamine release, unlike morphine. Therefore, the patient exhibits minimal hypotension when Depolarizing Neuromuscular Blockers used in small (1 to 4 µg/kg) doses. Like other narcotics, fentanyl causes respiratory depression and therefore places Succinylcholine is the most commonly used depolarizing neu- patients at risk for hypoxia and hypercarbia; this should not romuscular blocker. It is called a depolarizing agent because, be a problem during airway management as the patient will when it binds to the acetylcholine receptor on the muscle, it be continuously monitored. causes the muscle to depolarize or contract. This contraction Fentanyl, at high doses and rapid administration rates, is is limited in duration and is recognized by the Paramedic as associated with chest and abdominal wall muscular rigidity. fasciculations that occur shortly after the succinylcholine is This is an idiosyncratic reaction and results in the patient’s administered (Figure 24-2). Molecularly, succinylcholine is inability to breathe or to be ventilated. Generally speaking, composed of two acetylcholine molecules hooked back to this effect is not reversible and the patient must be paralyzed back. It is metabolized by pseudocholinesterase, an enzyme immediately. Other common effects of narcotics include nau- found throughout the body (but not actually in the neuromus- sea and vomiting. Fentanyl is often associated with an itchy cular junction). nose sensation. Succinylcholine is the most commonly used neuro- Fentanyl is indicated in the patient who may experience muscular blocker for rapid sequence intubation. It offers a signifi cant harm if there is a large catecholamine release. number of advantages over the non-depolarizing agents. Patients with acute MI, increased intracranial pressure, or vas- The two greatest assets are a rapid onset of action (30 to cular disease such as aortic dissection or aneurysm fall into 60 seconds) and rapid termination of effect (3 to 12 minutes)19 this classifi cation. In addition, any patient may benefi t from the with return of suffi cient ventilation to sustain life in 8 to analgesia and hypnosis associated with narcotics during airway 10 minutes.20 Although the duration of action is suffi ciently management, particularly if a narcotic (usually morphine) is long that a patient receiving no ventilatory support would the only agent that the Paramedic has available to her. become hypoxic,21 the short duration means that assisted Fentanyl is given in doses of 1 to 3 µg/kg slow IV push. ventilation will be needed for a much shorter time than with Morphine can be given in doses of 0.05 to 0.1 mg/kg slow IV non-depolarizing agents. Medication-Facilitated Intubation 479 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Transmitter Motor nerve cell substance (ACh) Sarcolemma Muscle cell Transmitter binding site NORMAL ACh Acetyl- cholinesterase Brief depolarization Figure 24-1 Physiology of a neuromuscular junction. Despite its possession of very desirable pharmacoki- Since succinylcholine causes muscular contraction when netic properties, succinylcholine does have a signifi cant side it initially binds to the acetylcholine receptor, the Paramedic effect profi le. Side effects of greatest importance in the pre- will see transient muscular fasciculations approximately hospital environment include fasciculations, hyperkalemia, 22 seconds after the medication is administered. These fas- and bradycardia. ciculations are associated with an increase in intragastric 480 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. succinylcholine and some other inhaled anesthetics), burns more than 24 hours old, or degenerative muscle disease. Patients with recent traumatic muscle denervation or crush DE B P L O injuries more than seven days prior should also not |
be given O L C A K RIZIN Neuromuscular succinylcholine. Finally, paralytics are contraindicated in all G blocking agents patients who cannot be face-mask ventilated in case the Para- medic is unable to intubate the patient. Depolarizing agent Succinylcholine dosing is based on the fact that very little creates an succinylcholine actually travels to the neuromuscular junc- overwhelming, tion. Since incomplete paralysis makes intubation much more persistent stimulation to receptors. diffi cult, a general rule is to use larger (rather than smaller) Membranes become doses. For an adult patient, 1.5 mg/kg of succinylcholine is exhausted and administered via rapid IV push. It can also be administered unresponsive to ACh. IM at a dose of 3 mg/kg, although it is not as predictable Acetylcholinesterase Muscle contraction in effi cacy. For children under 10, a dose of 2 mg/kg IV is Prolonged depolarization cannot recur until appropriate, and for infants and neonates, 3 mg/kg rapid IV return of resting state. push should be used. Figure 24-2 Depolarization of the Despite its signifi cant side effect profi le, succinylcholine neuromuscular junction. remains the neuromuscular blocker of choice for emergency airway management. Some thought should be given to the contraindications and side effects of the medication, but mul- pressure, intraocular pressure, and intracranial pressure. The tiple studies have demonstrated its safety and effi cacy in the increase in intragastric pressure may put the patient at risk for emergency airway management arena. regurgitation and aspiration; cricoid pressure is mandatory as soon as pretreatment medications are administered (sedatives, Non-Depolarizing (Competitive) etc.). In theory, the increase in intraocular pressure could Neuromuscular Blockers cause globe contents to herniate in the case of traumatic eye Non-depolarizing neuromuscular blockers (NMBAs) also injury. It is enlightening to note that many anesthesiologists cause paralysis through blocking acetylcholine, although still use succinylcholine without a defasciculating dose of a through a somewhat different mechanism than succinyl- non-depolarizing agent (discussed in the following text) in choline. These agents compete with acetylcholine for the the setting of open globe injuries.20 The rise in intracranial acetylcholine receptor on the postsynaptic membrane pressure of approximately 5 mmHg is of no known clinical (Figure 24-3), but do not cause the receptor to fi re. Therefore, signifi cance22 but can be blunted through pretreatment, as there are no fasciculations. The molecular model for non- will be discussed later. depolarizing neuromuscular blockers is curare. Succinylcholine administration has also been associated There are a number of non-depolarizing neuromuscular with an increase in serum potassium levels. This tends to blockers available for the Paramedic, all of which are of the happen in patients with a precipitating event (burns, neuro- aminosteroid class of NMBAs. The most commonly used muscular disease, pre-existing hyperkalemia, crush injuries, and muscle denervation). In addition, for those patients with traumatic causes, the effect is not seen for two to seven days from the event. Therefore, although the Paramedic must con- sider whether a patient is at risk for hyperkalemia, there are NO DE N few prehospital situations (other than in patients with known P - B hyperkalemia, neuromuscular disease, or in the critical care L O O L C A K RI transport environment) where the risk for hyperkalemia will ZING be important. ACh There is increased vagal tone that occurs with the a dministration of succinylcholine. Although the clinical signifi cance is low for adults after a single dose of succinyl- Non depolarizing choline, the effect can be dramatic in children, leading to agent acts to block bradycardia and even asystole. The effect is easily mitigated ACh receptor sites in an overwhelming, with pretreatment with atropine. competitive manner. There are a few absolute contraindications to the admin- No depolarization istration of succinylcholine. These include a personal or Neuromuscular family history of malignant hyperthermia (a skeletal blocking agents muscle disease that leads to a life-threatening reaction to Figure 24-3 Neuromuscular blockade. Medication-Facilitated Intubation 481 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. agent in the prehospital environment is vecuronium; other patient. A defasiculating dose is a small dose of a non- agents of this class include rocuronium, pancuronium, and d epolarizing paralytic which, when administered before rapacuronium. Although these agents have a much less sig- administering succinylcholine, prevents the fasciculations nifi cant side effect profi le than succinylcholine, they gener- associated with succinylcholine. ally have a longer time to onset at standard doses and they all The only risk associated with this technique is that the have a prolonged duration of action. Two agents, rocuronium patient may occasionally become apneic and fully paralyzed and rapacuronium, have onset of action in about 60 seconds with the defasciculating dose. The Paramedic must therefore be and rapacuronium has a duration of action that is almost the prepared to administer the full paralytic dose and intubate the same as succinylcholine.23,24 Therefore, these agents offer the patient. potential to replace succinylcholine in the emergency airway Non-depolarizing agents are also commonly used for management setting. post-intubation care. In the prehospital environment, it is Unfortunately, rapacuronium, the most promising of the usually more important that an intubated patient be protected agents (30- to 60-second onset, 20-minute paralysis without from himself and the risk of accidental self-extubation than reversal, 10-minute paralysis with reversal agent), also has it is to perform serial neurological exams. This is particularly the most signifi cant side effect profi le. important in the air medical environment where re-intubation Fasciculations, hyperkalemia, and increased intracra- can be extraordinarily diffi cult. Therefore, most prehospital nial pressure are not seen with the use of non-depolarizing patients who are rapid sequence intubated are given a full NMBAs. Therefore, in patients at risk for adverse outcomes paralyzing dose of vecuronium to minimize patient move- from those side effects of succinylcholine, a non-depolarizing ment and the risks of extubation. NMBA is the paralytic agent of choice. Since the duration of action of the vecuronium (30 to In most other cases, the delay in onset of paralysis and 60 minutes) will typically be longer than the duration of action the prolonged paralysis make these agents less desirable. of most sedatives, it is important to monitor for tachycardia Pancuronium and rapacuronium have both been associated and hypertension, both of which suggest that the patient is with tachycardia, and rapacuronium has also been associated paralyzed but not sedated. with transient hypotension and bronchospasm. vecuronium As noted, vecuronium is the most commonly used non- and rocuronium have relatively few side effects. depolarizing neuromuscular blocker used in the prehospital Neostigmine, an acetylcholinesterase inhibitor, can setting. The usual dose is 0.1 mg/kg. As mentioned, doses of be used to reverse the effects of the competitive (non- 0.3 mg/kg can be given to attain paralysis in 60 to 90 seconds, depolarizing) NMBAs. They do this by inhibiting acetylcho- but the patient will be paralyzed for up to 100 minutes. This is linesterase, the enzyme that breaks down acetylcholine. With a problem if the patient cannot be intubated and must be face- acetylcholinesterase blocker, more acetylcholine builds up in mask ventilated. At a dose of 0.1 mg/kg, the usual onset of the synapse, displacing the NMBA and decreasing recovery action is in two to three minutes. Since most sedative agents time. Although neostigmine does not instantly reverse the have an earlier onset of action, administering the vecuronium NMBA, it can cut the recovery time in half. and awaiting signs of muscular weakness before administer- There are three primary indications for the use of a non- ing the sedative may decrease the incidence of apnea before depolarizing neuromuscular blocking agent. The fi rst is a adequate paralysis occurs. paralytic patient with a contraindication to the use of succi- The non-depolarizing neuromuscular blocking agents nylcholine. The only true contraindication that succinylcho- offer many advantages over succinylcholine in terms of their line and the non-depolarizing NMBAs share is the one against side effect profi le. Unfortunately, they are limited in their use their use in patients who cannot be effectively f ace-mask ven- by their delayed onset of action and prolonged paralysis. Cur- tilated. Paralyzing a patient who can neither be intubated nor rently, they are used primarily for defasciculation and post- ventilated is truly the worst case scenario in airway manage- intubation paralysis. Newer agents with more rapid paralysis ment using RSI. It is important to note that if vecuronium and short duration of action may offer a reasonable alterna- is used for paralysis, the patient will usually become apneic tive to succinylcholine in the future. before adequate paralysis occurs and the patient will need face-mask ventilation. This problem can be mitigated if a Adjunctive Medications large (0.3 mg/kg) dose of vecuronium is used or a priming (0.01 mg/kg 2 to 3) dose of vecuronium is administered two Lidocaine and atropine are two agents that are commonly to three minutes before the intubating dose is administered. used as adjuncts to emergency rapid sequence intubation. Non-depolarizing NMBAs possess the unique ability to Both of these drugs are used to counter the effects of paralyt- block fasciculations. In doses of one tenth its intubating dose ics and of airway manipulation. (e.g., 0.01 mg/kg), vecuronium given two to three minutes before succinylcholine will prevent fasciculations and the side Lidocaine effects associated with fasciculations (increased ICP, etc.). Lidocaine, a drug thought to offer some neuroprotection, is The use of a defasciculating dose of a non-d epolarizing commonly used during the RSI of patients with head trauma, agent is most often used in the setting of the head-injured evidence of increased intracranial pressure, and bronchospastic 482 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. airway disease.25 Although there is controversy about the clin- The Paramedic should also verify the last oral intake, ical signifi cance of the effects of lidocaine, when used, it is if possible. most often used for patients with head trauma. Through a combination of deepened sedation and mul- tiple cerebral hemodynamic effects, lidocaine is thought to provide some cerebral protection for patients undergoing air- Street Smart way manipulation and may be protective against the effects of succinylcholine. In addition, lidocaine may blunt the sym- It is important that the preparation phase should be pathetic response to laryngoscopy, although this has not been the same whether the patient is undergoing intubation defi nitively demonstrated. When used, IV lidocaine at a dose of 1.5 mg/kg is administered at least three minutes before with or without pharmacological adjuncts. The administration of succylcholine. preparation step assures that “the fi rst attempt is the Atropine best attempt.” Inadequate preparation for airway management results in delays in intubation Airway management, particularly in pediatric patients under 10 years old, can cause excessive vagal stimulation. and hypoxia. Furthermore, large or multiple doses of succinylcholine put patients at risk of increased vagal tone. Therefore, atropine, a parasympathetic blocker that decreases vagal response, must be available for the treatment of these patients. In addition, atropine decreases oral secretions, an Predict the Degree of Diffi culty effect that is useful for patients sedated with ketamine or Prediction is the most important step in making the decision with excessive secretions.19 to perform a medication-facilitated or rapid sequence intuba- All patients under 5 years of age should be pretreated tion. The actual skill of intubating a person who is chemi- (two to three minutes before paralysis) with 0.2 mg/kg of IV cally paralyzed is no more diffi cult than if that person were atropine (0.1 mg < dose < 0.5 mg). In addition, any adult completely comatose with no muscle tone (i.e., a patient in patient receiving a second dose of succinylcholine should cardiac arrest). The difference |
lies in the fact that a person either be pretreated with 0.5 mg IV or atropine should be who is alive, breathing, and protecting his airway enough to immediately available if the patient becomes bradycardic. prevent intubation without medications is still alive. If the Paramedic proceeds to paralyze this patient, he takes full responsibility for the consequences of removing the patient’s The 9 P’s for Medication (limited) ability to care for himself. Therefore, extraordinary Facilitated Intubation judgment must be exercised before deciding to sedate and, more importantly, chemically paralyze a patient. The most and Rapid Sequence Intubation critical deciding factor is whether or not the Paramedic will be able to intubate the patient and, if not, provide face-mask The most commonly used tool to guide safe and effective ventilation. The guiding principle of all medical care is Pri- intubation is the rule of the “Nine P’s of RSI.” The nine mum non nocere or “fi rst, do no harm.” Chemical paralysis “P’s” are: provides the opportunity to do grave and irreparable harm to 1. Preparation a patient. 2. Predict the degree of diffi culty 3. Preoxygenate 4. Pretreat Table 24-1 Equipment List for MFI 5. Pressure on the cricoid 6. Paralyze • Continuous cardiac monitoring 7. Pass the tube • Continuous pulse-ox 8. Position (confi rm) and secure • BVM attached to 100% O2 9. Post-intubation care • Oral airway Correctly applying each of these “P’s” greatly enhances • Suction set-up the safety and effi cacy of the intubation. • ETCO2 detector/continuous monitoring ETCO2 • Ventilator attached and ready (if using) Preparation • RSI medications drawn up Preparation for medication-facilitated or rapid sequence • IV established intubation involves assuring that all necessary equipment is • Intubation equipment properly assembled and ready for use (Table 24-1). Medication-Facilitated Intubation 483 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. The need to perform an airway evaluation on all patients example, succinylcholine and etomidate have almost the before and during airway management is self-evident. Two same time of onset and therefore are administered almost tools—the LEMON law and the 3-3-2 rule—were intro- simultaneously. Midazolam, on the other hand, has a two to duced in Chapter 23. It is important to apply the LEMON law three minute time of onset and must be administered well in before any rapid sequence intubation. The Paramedic must advance of succinylcholine. As was discussed previously, if recognize when conditions exist which will prevent him or vecuronium is going to be used, it should probably be admin- her from being able to intubate the patient after paralysis. If istered before the sedative to minimize the risk of apnea. the patient’s airway is simply too diffi cult for a Paramedic’s The Paramedic must be alert during the pretreatment skill level, then the patient should not be paralyzed. phase. Some patients, particularly those who already have a In addition to assessing the diffi culty of the intuba- signifi cantly altered mental status, may become apneic after tion, however, it is also important to assess how diffi cult receiving pretreatment medications. Therefore, all equipment it will be to perform face-mask ventilation. Facial hair, for the intubation must be ready for immediate use and the facial trauma, micrognathia (small jaw), and other ana- patient closely monitored. tomic anomalies may make face-mask ventilation diffi cult or impossible. Any patient who cannot be face-mask ven- Cricoid Pressure tilated should not receive paralytic agents or sedatives in While sedative or defasciculating medications are being doses that could cause apnea. Although this may be a diffi - administered, an assistant should be assigned to apply cricoid cult decision, medication-facilitated intubation is as much pressure to minimize the risk of aspiration. A patient who has about deciding not to give the medications as it is about received sedatives will have decreased airway refl exes and giving the medications. may have a decreased lower esophageal pressure. These two factors put the patient at risk for vomiting and aspirating. Preoxygenate If the Paramedic is performing a sedation-aided intuba- It is possible to extend the time allowed for an intubation tion, the intubation attempt is made now (see the “Pass the attempt by adequately preoxygenating a patient. Adminis- Tube” section later). In addition, many providers will make tration of high fl ow oxygen for three to fi ve minutes or for an attempt at intubation before paralytics are administered if 10 to 22 deep breaths removes nitrogen from the lungs and the patient appears to be suffi ciently sedated. If the patient is replaces it with oxygen. Respiratory gasses at the level of successfully intubated with sedation alone, many of the risks alveoli include 75% nitrogen for the patient breathing room of paralysis can be avoided. air. By “washing out” the nitrogen through preoxygenation, a much larger reserve of alveolar oxygen is created. Patients Paralyze can therefore be apneic for prolonged periods (two to fi ve Once the patient has been pretreated and an appropriate time minutes) before oxygen desaturation occurs. Since hypoxia interval has passed, the paralytic agent should be given. One is so potentially damaging, this safety reserve can protect of the most signifi cant mistakes a Paramedic can make is to a patient during the prolonged apnea that can be associated attempt to intubate the patient too quickly after the paralytic with the use of sedatives and paralytics. is given. If an intubation attempt is made before the patient is completely paralyzed, not only will the patient fi ght the Pretreat attempt but the risk of aspiration is also greatly increased. Once the decision has been made to perform sedation-aided or Therefore, either a clock/watch should be used or the Para- rapid sequence intubation and the patient is preoxygenated, it medic should count out 45 seconds once succinylcholine is is important to administer any pretreatment medications that administered. No attempts to intubate should be made before will be used. Sedatives are considered “pretreatment” since then and, unless the patient desaturates, no face-mask ventila- they are used to prepare a patient for paralytics. Lidocaine, tion should be applied. If a non-depolarizing agent is used, a atropine, and defasciculation doses of non-d epolarizing similar approach of waiting for complete paralysis should be neuromuscular blockers are the other commonly used followed. pretreatment medications. Pass the Tube There is no evidence that routine use of pretreatment medications (other than sedatives) in patients without spe- Once the patient is completely paralyzed, standard methods cifi c indications (i.e., increased ICP, pediatric patients.) of oral endotracheal intubation should be used. Suction must improves patient outcomes. Therefore, atropine, lidocaine, be immediately available in the event the patient vomits. and defasciculating drugs (e.g., vecuronium 0.01 mg/kg IV) External laryngeal manipulation and/or the BURP maneuver should only be used if an indication exists. If they are going should be used to optimize visualization. to be given, they should be administered two to three minutes before the paralytic agent. Position (Confi rm) and Secure The timing of the sedative’s administration will depend Once the patient has been intubated, the tube position must be on its onset of action and the paralytic that will be used. For confi rmed with at least three methods. The paralyzed patient 484 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. is completely dependent on being ventilated. If the patient is The second important medication is a long-acting seda- esophageally intubated, he cannot continue to breathe around tive (e.g., midazolam). If etomidate is used for the intubation, the tube the way a non-paralyzed, non-apneic patient can. it will begin to wear off in 10 to 20 minutes after administra- Therefore, confi rmation must be rapid and accurate. The para- tion. Although other sedatives (e.g., midazolam, ketamine) lyzed patient is also at risk for complications from a displaced may have a longer duration of action, their duration will still tube, particularly after receiving post-intubation sedation and be less than that of vecuronium. Therefore, the patient should paralysis. Use of continuous end-tidal carbon dioxide moni- be monitored for signs (tachycardia and hypertension) of toring decreases the risk of a missed displaced tube. inadequate sedation. Properly securing the endotracheal tube also decreases the risk of tube dislodgment. Any method is acceptable as long as it prevents the endotracheal tube from moving. The Street Smart depth of the endotracheal tube at the lips should be noted and recorded to verify that there is no tube movement. The neck should be secured with a cervical collar to prevent fl exion The Paramedic will recognize that induced paralysis and extension and the patient should be secured to a long- does not alter sensation. The patient is acutely aware spine board for transport. of noise, lights, odors, pain, and other sensations Post-Intubation Care such as pressure. These stimuli should be reduced Once the patient has been successfully intubated and the tube or eliminated by altering the environment or is secured, there are several important post-intubation tasks administering appropriate medications. to be performed. All patients who are intubated should have a nasogastric or orogastric tube placed to allow active or pas- sive decompression of the stomach. This is particularly true The Paramedic should be aware and monitor for signs of for pediatric patients who can suffer signifi cant respiratory malignant hyperthermia. This is a genetic muscular disease compromise from gastric infl ation. that affects some people after receiving inhaled anesthetics There are also two important post-intubation medications or succinylcholine. Signs of malignant hyperthermia include that should be administered. The fi rst important medication to fever, muscular rigidity (as opposed to being fl accid), tachy- administer is a long-acting non-depolarizing neuromuscular cardia, and tachypnea. Although most EMS providers will blocker, generally vecuronium. As was discussed previously, not have access to Dantrolene, the medication used to treat post-intubation paralysis decreases the risk of accidental malignant hyperthermia, the patient can be cooled with cold extubation. If vecuronium was used to perform the intuba- packs and exposure. In addition, the receiving facility should tion, it is not necessary to administer a second dose. be notifi ed of the patient’s condition. Medication-Facilitated Intubation 485 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Medication-facilitated and rapid sequence intubation offer the Paramedic an expanded range of tools for patient care. Patients who could not previously be intubated can receive the benefi ts of translaryngeal endotracheal intubation. These medications, however, are not without side effects and their use is associated with complications. The actual acts of administering the medications and performing the intubation are no different than in any other patient. The most critical difference, particularly for the use of paralytics, is the judgment required to make the initial decision to paralyze the patient. Chemical paralysis cannot be done lightly or without forethought; it is an intervention with the potential to kill a patient. Nonetheless, there are clear benefi ts to performing rapid sequence intubation and therefore the Paramedic should be familiar with the procedure. Key Points: • The most important factors in the success of RSI minimal hemodynamic effects and only moderate programs have been the involvement of an active respiratory depression at induction doses. medical director, review of each intubation, strong Etomidate also attenuates an increased ICP and educational components, and |
an overall effective decreases the negative effects of laryngoscopy. monitoring system. Side effects may include transient muscle jerks • and trismus. Many patients experience nausea and The use of pharmacological agents to facilitate vomiting upon awakening. intubation can be thought of as those that provide sedation and those that cause muscular paralysis. • Ketamine is a dissociative anesthetic that provides In addition, adjunctive medications that are often excellent amnesia, analgesia, and anesthesia during used in RSI include vagolytics (atropine) and procedures and intubation. Ketamine also has minimal lidocaine. respiratory depression; it increases heart rate and • blood pressure through the release of catecholamines Sedative agents are medications that are used to and has the pulmonary effect of reducing decrease a patient’s level of consciousness, effect bronchospasm through smooth muscle relaxation. It muscular relaxation, and cause amnesia to the should be avoided in the head-injured patient. intubation. Four of the most commonly used agents are midazolam (a benzodiazepine), etomidate, • Narcotics provide analgesia and hypnosis as well ketamine, and fentanyl (a narcotic). as some degree of amnesia. In addition, they • attenuate the increased ICP that is a refl exive Midazolam, a short-acting benzodiazepine, has an response to laryngoscopy. Lower doses of narcotics onset of action of 30 to 60 seconds and a half-life can be used in emergency airway management to of 1.5 to 2.5 hours. achieve some degree of patient sedation. • Response to midazolam varies widely. In general, male patients and elderly patients require the smallest • Fentanyl is a synthetic opioid that is highly potent doses. The most signifi cant complication associated and has minimal hemodynamic effects. Like with midazolam is the development of shock. other narcotics, it causes respiratory depression. It may be indicated in the patient who may • Etomidate is a newer agent that functions experience signifi cant harm if there is a large primarily as a hypnotic and amnestic. It has catecholamine release. 486 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. • Neuromuscular blockers prevent transmission (5) pressure on the cricoid, (6) paralyze, (7) pass the of nerve impulses to skeletal muscle at the tube, (8) position (confi rm) and secure, and (9) post- neuromuscular junction by either binding to intubation care. the receptor, causing a muscular contraction (a depolarizing agent), or simply blocking • To prepare for medication-facilitated or rapid acetylcholine from binding to the receptor sequence intubation, and to assure the “fi rst without causing the receptor to activate (a non- attempt is the best attempt,” the Paramedic depolarizing agent). should ensure all necessary equipment is properly assembled and ready to use. • Succinylcholine is a depolarizing agent. It binds to the acetylcholine which binds to the receptor, • Predicting the degree of diffi culty is the most causing the muscle to contract, and then prevents important step in making the decision to perform further contractions. a medication-facilitated or rapid sequence intubation. • Contraindications for succinylcholine include a personal or family history of malignant • Preoxygenation of the patient is performed by hyperthermia, burns more than 24 hours old, administering high fl ow oxygen for three to fi ve degenerative muscle disease, and crush injuries minutes or for 10 to 22 deep breaths. This removes more than seven days prior. nitrogen from the lungs and replaces it with oxygen • which can extend the time allowed for an intubation Paralytics are contraindicated in all patients attempt. who cannot be face-mask ventilated in case the Paramedic is unable to intubate the patient. • Pretreatment medications—lidocaine, atropine, • and defasciculating doses of non-depolarizing Vecuronium, rocuronium, pancuronium, and neuromuscular blockers—should be given two to rapacuronium are non-depolarizing agents that do three minutes before the paralytic agent. not cause fasciculations. These agents generally have a longer time to onset at standard doses and • While sedative or defasciculating medications are they all have a prolonged duration of action. being administered, a patient care provider should • apply cricoid pressure to minimize the risk of Neostigmine inhibits acetylcholinesterase, allowing aspiration. more acetylcholine to build up in the synapse, displacing the NMBA and decreasing recovery time. • Once the patient has been pretreated and an • appropriate time interval has passed, the paralytic A non-depolarizing neuromuscular blocking agent is agent should be given. Once succinylcholine commonly used to block fasciculations through a low is administered, no face-mask ventilation should be dose administration called a defasciculating dose. applied and the Paramedic should count out • Lidocaine and atropine are used to counter the 45 seconds before attempting to intubate. effects of paralytics and of airway manipulation. • After paralysis is achieved, standard methods of oral • Airway management, particularly in pediatric endotracheal intubation should be used. patients under 5 years old, can cause excessive vagal stimulation, primarily bradycardia. • Following intubation, tube position must be confi rmed rapidly and accurately with at least • The most commonly used tool to guide safe and three methods. Standard methods for securing the effective intubation is the rule of the “Nine P’s of RSI.” tube are then performed, and continuous end-tidal The nine “P’s” are (1) preparation, (2) predict the carbon dioxide monitoring is used to monitor for degree of diffi culty, (3) preoxygenate, (4) pretreat, tube displacement. Medication-Facilitated Intubation 487 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Review Questions: 1. What two general categories of medications 8. List two reasons why succinylcholine is exist for airway management? used preferentially to non-depolarizing 2. What are the key differences between the NMBAs. following sedative agents: midazolam, 9. Name two adjunctive medications for RSI and etomidate, ketamine, and fentanyl? give their indications. 3. What is the mechanism of action of a 10. What are the “Nine P’s of RSI”? depolarizing neuromuscular blocking agent 11. How should the Paramedic assess the airway (NMBA)? for medication-facilitated and rapid sequence 4. What is the mechanism of action of a non- intubation? depolarizing NMBA? 12. Explain the protective effect of preoxygenation. 5. How does neostigmine affect neuromuscular 13. Identify two post-intubation medications and blockade? explain why they are used. 6. Describe four side effects of succinylcholine. 7. Explain the difference between a “defasciculating” and a “paralytic” dose of a non-depolarizing NMBA. Case Study Questions: Please refer to the Case Study at the beginning 3. Approximately 15 minutes into the fl ight, the of the chapter and answer the questions below: fl ight medic observes an increase in heart rate 1. List at least three reasons for using medications and blood pressure. What might cause this during intubation of this patient. response? What actions are indicated? 2. What adjunctive medications are indicated for this patient? Why? 488 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. References: 1. Bozeman WP, Young S. Etomidate as a sole agent for 14. Chohan N, ed. Physician’s Drug Handbook (8th ed.). endotracheal intubation in the prehospital air medical setting. Philadelphia, Lippincott, Williams and Wilkens; 1999:424–425. Air Med. 2002;21(4):32–36. 15. O’Connor RE, Levine BJ. Airway management in the trauma 2. Wang HE, O’Connor RE, Megargel RE, et al. The utilization of setting. In: Ferrera PC, Colucciello SA, Marx JA, et al. Trauma midazolam as a pharmacologic adjunct to endotracheal intubation Management: An Emergency Medicine Approach. St. Louis: by Paramedics. Prehosp Emerg Care. 2002;4(1):14–18. Mosby; 2001:52–74. 3. Wayne MA, Friedland E. Prehospital use of succinylcholine: a 16. Chohan N, ed. Physician’s Drug Handbook (8th ed.). 20-year review. Prehosp Emerg Care. 1999;3(2):107–109. Springhouse: Philadelphia, Lippincott, Williams and Wilkens; 4. Hedges JR, Dronen SC, Feero S, Hawkins S, Syverud SA, Shultz 1999:593–594. B. Succinylcholine-assisted intubations in prehospital care. Ann 17. Gibbs JM. The effect of intravenous ketamine on cerebrospinal Emerg Med. 1988;17(5):469–472. fl uid pressure. Br. J. Anesth. 1972;44(12):1298–1302. 5. Vilke GM, Hoyt DB, Epperson M. et al. Intubation techniques in 18. Sloan T. Anesthetics and the brain. Anesthiol Clin North America. the helicopter. J Emerg Med. 1994;12(2):217–224. 2002;20(2):265–292. 6. Syverud SA, Borron SW, Storer DL, et al. Prehospital use 19. Yamamoto LG. Rapid sequence anesthesia induction and of neuromuscular blocking agents in a helicopter ambulance advanced airway management in pediatric patients. Emerg Med program. Ann Emerg Med. 1988;17(3):236–242. Clin North America. 1991;9(3):611–638. 7. Sing RF, Reilly PM, Rotondo MF, et al. Out-of-hospital rapid- 20. Schneider R. Muscle relaxants. In: Walls R et al., eds. Manual sequence induction for intubation of the pediatric patient. Acad of Emergency Airway Management. Philadelphia: Lippincott, Emerg Med. 1996;3(1):41–45. Williams, and Wilkins; 2000:122–128. 8. Ochs M, Davis D, Hoyt D, Bailey D, Marshall L, Rosen P. 21. Benumof JL. Succinylcholine duration and critical Paramedic-performed rapid sequence intubation of patients with hemoglobin desaturation in the healthy adult. Anesthesiology. severe head injuries. Ann Emerg Med. 2002;40(2):159–167. 1998;88(6):1686–1688. 9. Winchall RJ, Hoyt DB. Endotracheal intubation in the fi eld 22. Storer DL. The pharmacology of airway control. Emerg Care Q. improves survival in patients with severe head injury. Trauma 1991;7(1):64. Research and Education Foundation of San Diego. Arch Surg. 23. DeMay JC, Debrock M, Rolly G. Evaluation of the onset and 1997;132(6):592–597. intubation conditions of rocuronium bromide. Eur J Anesthesiol 10. Karch SB, Lewis T, Young S, et al. Field intubation of trauma Suppl. 1994;9 (Suppl):37–40. patients: complications, indications, and outcomes. Am J Emerg 24. Fleming NW, Chung F, Glass PS, et al. Comparison of the Med. 1996;14(7):617–619. intubation conditions provided by rapacuronium (ORG9487) or 11. Dickinson ET, Cohen JE, Mechem CC. The effectiveness succinylcholine in humans during anesthesia with fentanyl and of midazolam as a single pharmacologic agent to facilitate propofol. Anesthesiology. 1999;91(5):1311–1317. endotracheal intubation by Paramedics. Prehosp Emerg Care. 25. Schneider R. Drugs for special clinical circumstances. In: 1999;3(3):191–193. Walls R, et al., eds. Manual of Emergency Airway Management. 12. Reed DB. Regional EMS experience with etomidate for Philadelphia: Lippincott, Williams, and Wilkins; 2000: facilitated intubation. Prehosp Emerg Care. 2002;6(1):50–53. 135–139. 13. Schneider R. Sedatives and induction agents. In: Walls R, et al., eds. Manual of Emergency Airway Management. Philadelphia: Lippincott, Williams, and Wilkins; 2000:129–139. Medication-Facilitated Intubation 489 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. KEY CONCEPTS: Upon completion of this chapter, it is expected that the reader will understand these following concepts: • The formation of acid from respiratory and metabolic mechanisms and physiological pH • Three important chemical buffers found in the bloodstream • Respiratory and renal compensation by deriving the acid–bicarbonate formula • Acidosis as an imbalance Case Study: The Paramedics were called to the local community college for an instructor suffering an acute asthma attack. Mr. Byrnes had a lengthy history of asthma beginning in high school. His last attack, four months ago, had required intubation and two days on ventilatory support. The nurse in the health offi ce had placed Mr. Byrnes on oxygen along with monitoring pulse oximetry. He had tried to use his rescue inhaler but could not take deep enough breaths. Even though his pulse oximetry reading was |
at 97%, one look indicated that he was laboring, tachypneic, and fearful. 490 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Ventilation 491 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. OVERVIEW Ventilation is more than just the movement of air in and out the lungs. For the Paramedic, examining ventilation involves understanding the physiology of gas exchange and the different ways the body maintains a balanced pH. Metabolically, the body’s organs work together to maintain an acid−base balance. This chapter examines the basic chemistry of pH, the chemical buffers, and how ventilation provides a fi rst line of defense from acid imbalance. Respiratory and renal mechanisms also play an important role by driving the acid–bicarbonate formula, which works to regulate pH. Respiratory acidosis is seen as an imbalance that the Paramedic can recognize and treat. Respiration and Oxygen is an ineffective method for carrying oxygen to the tissues because oxygen does not easily dissolve into liquid and Transportation only a small amount of oxygen can be delivered. A more The term “respiration” has several defi nitions applicable to effective mechanism for oxygen transport involves binding Paramedic practice.1 The fi rst defi nition of respiration is the the oxygen molecules directly to a compound or structure movement of respiratory gasses in and out of the lungs. As within the blood for transportation to the tissues. This trans- discussed in Chapter 16, one respiration is the cycle of inspi- port mechanism is responsible for the other 97% of oxygen ration and expiration which moves air in and out of the lungs. transported to the tissues and involves red blood cells and On a cellular level, respiration is defi ned as “the chemical the hemoglobin molecule that makes up the majority of the processes by which an organism supplies its cells and tissues red blood cell. with the oxygen needed for metabolism and relieves them of Each red blood cell contains approximately 270 mil- the carbon dioxide formed in energy-producing reactions.” lion hemoglobin molecules. Each hemoglobin molecule can Respiration includes everything from inspiration, movement normally bind up to four oxygen molecules (Figure 25-3). of oxygen into the bloodstream, absorption of oxygen into When the hemoglobin molecule attaches at least one oxygen the cells, utilization of oxygen to make energy, the movement molecule, it is called oxyhemoglobin. The hemoglobin mol- of carbon dioxide to the bloodstream and ultimately across ecule that is not attached to any oxygen molecules is called into the air in the alveoli, and the exhalation of carbon diox- deoxyhemoglobin. As oxygen attaches to each of the binding ide into the atmosphere (Figure 25-1). Through this process, sites, the shape of the hemoglobin molecule opens up around the human body is able to live and function. the other oxygen-binding sites, making it easier to bind oxy- The components of this process that the Paramedic can gen to the next site. Due to this property, it takes a smaller affect during the breathing step in the resuscitation involve increase in partial pressure of oxygen (see the discussion on several actions that improve oxygenation and ventilation. partial pressures in Chapter 20) to saturate the hemoglobin Before we can assess those components, let’s review how the molecules with oxygen when hemoglobin is in the deoxyhe- body transports oxygen and carbon dioxide. moglobin state. As hemoglobin nears complete saturation, it then takes a larger change in partial pressure of oxygen to fully saturate all oxygen-binding sites. Figure 25-4 demon- Oxygen Transport strates this relationship between partial pressure of oxygen Oxygen comprises 21% of room air. As discussed in Chap- and hemoglobin saturation. It should be noted that arte- ter 20, the fraction of inspired oxygen, FiO , can be increased rial blood typically has a saturation of approximately 97%, 2 by providing supplemental oxygen to the patient through one whereas venous blood will typically have a oxygen saturation of several oxygen delivery devices. Inspiration fi lls the lungs of approximately 75%.2 with oxygen-rich air. Oxygen diffuses across the alveoli and There are several factors that affect oxygen’s ability to capillary wall because of the higher concentration of oxygen bind to hemoglobin. Some of these factors are used by the in the alveoli compared with the lower concentration of oxy- body to enhance the release of oxygen as part of normal gen in the blood surrounding the alveoli (Figure 25-2). transport, whereas others occur when the body is ill or injured Oxygen is transported to the tissues by two different (Table 25-1). The factors that increase oxygen binding in mechanisms. Approximately 3% of oxygen that enters the effect shift the curve in Figure 25-4 to the left. By shifting the bloodstream is dissolved into the plasma, or liquid portion curve to the left, it takes a smaller change in partial pressure of the blood, similar to the way carbon dioxide is dissolved of oxygen to increase the saturation of the hemoglobin. Con- into liquid to produce the fi zz in carbonated beverages. This versely, the factors that decrease oxygen binding move the 492 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Inhalation Exhalation Oxygen moves into bloodstream O2 CO2 O2 CO O 2 2 CO O2 2 O2 O2 Movement of CO2 into alveoli Capillary bed O2 O2 O2 Absorption of oxygen into cells CO2 CO2 Figure 25-1 The process of respiration. Hemoglobin O2 O2 O Oxygen molecule 2 Red blood cell O2 O2 O Alveoli 2 O2 O2 O2 O2 O2 O O 2 2 O2 O2 Hemoglobin carries O2 oxygen throughout O2 the body Pulmonary capillaries Figure 25-3 Red blood cells contain hemoglobin, the oxygen-carrying portion of the Figure 25-2 Oxygen movement across the blood, which can transport up to four oxygen alveoli–capillary membrane. molecules per hemoglobin molecule. Ventilation 493 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Dissolved O2 100 (Total O2) 20 90 Normal P 18 O2 80 16 70 14 60 12 O2 Combined 50 with Hb 10 40 8 30 6 20 4 10 Dissolved O2 2 0 0 10 20 30 40 50 60 70 80 90 100 PO2 (mm Hg) Figure 25-4 The oxygen–hemoglobin dissociation curve. In the lower portion of the curve, it takes a small increase in partial pressure of oxygen to produce a large increase in oxygen saturation. Table 25-1 Factors That Affect the Ability Temperature also affects hemoglobin’s ability to off-load to Bind Oxygen to Hemoglobin oxygen at the tissues. Decreased temperatures shift the curve to the left while increased temperatures will shift the curve to Increased Decreased the right. This is why patients who have sustained traumatic • Alkalosis • Acidosis injury, who are often cold from exposure, even in warmer cli- • Decreased CO2 • Increased CO mates, should be kept warm and provided with supplemental 2 • Decreased temperature • Increased temperature oxygen to compensate for the diffi culty in off-loading oxygen • Decreased 2,3-BPG • Increased 2,3-BPG as a result of decreased body temperature. Once the hemoglobin circulates to the tissues, some of the oxygen bound to hemoglobin dissociates, or is released, from the hemoglobin into the blood and taken into the cells. curve to the right, requiring a larger change in partial pres- The environment in the capillary blood has a lot of the fac- sure of oxygen to saturate the hemoglobin molecules. tors that enhance oxygen release from hemoglobin, including Both alkalosis and acidosis will be discussed later in this increased carbon dioxide and increased levels of 2,3-BPG. chapter. Alkalosis will cause a shift in the curve to the left, In the cell, oxygen is used with glucose to produce energy increasing the affi nity of hemoglobin to oxygen, and acidosis to carry out the cell’s functions (e.g., contraction for muscle will cause a shift in the curve to the right, decreasing the affi n- cells, chemical production for an endocrine cell, or to fi ght ity of hemoglobin for oxygen. This change in affi nity helps bacterial invaders). the hemoglobin either hold on to the oxygen molecules or enhances the release of oxygen molecules from hemoglobin. Carbon Dioxide Transport A second way the body enhances release of oxygen from Carbon dioxide is a by-product of cellular respiration. During hemoglobin is through a compound called 2,3-BPG. 2,3-BPG the chemical processes within the cell, oxygen and glucose occurs naturally in the hemoglobin, enhancing the release of are used to produce energy for the cell. Carbon dioxide and oxygen from hemoglobin at the tissues to provide oxygen for water are produced as waste products of this reaction. The the energy production process at the cellular level. This com- carbon dioxide diffuses across the cell membrane and into pound can be found in higher concentration in situations where the blood. Once in the blood, some carbon dioxide is taken the amount of oxygen inhaled into the lungs is decreased or in up and carried to the lungs in the red blood cells while some conditions where there is chronic tissue hypoxia. This is a way stays dissolved in the plasma. for the body to compensate for less available oxygen at high alti- Carbon dioxide is 20 times more soluble than oxygen in tudes or for advanced chronic respiratory conditions. Increased the blood at the same partial pressure, and much of the car- production of 2,3-BPG helps to prevent hypoxia in the tissues. bon dioxide transported by the blood is dissolved within the 494 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. % Hb Saturation O2 Content mL/100 mL (vol%) plasma. Some of the dissolved carbon dioxide is then absorbed couple with other molecules, even if it means uncoupling into the red blood cells and then released back into the blood one chemical molecule from another and bringing about the as bicarbonate, which is then transported to the lungs. A small destruction of the molecule compound in order to allow the amount of carbon dioxide travels back to the lungs attached hydrogen to attach, or bond, with another chemical. to the hemoglobin molecules, at a different site from the oxy- In some cases, a molecule may be negatively charged, gen molecules, and some carbon dioxide molecules combine such as the hydroxyl molecule (OH). These chemicals are with other compounds in the blood. Therefore, carbon diox- called bases and bases lack a proton and want to accept the ide is transported to the lungs in one of three ways: dissolved protons from acid |
in order to become electrically balanced. in the blood plasma, attached to hemoglobin, or contained For example, if an acid (H) was to join with a base (OH), with bicarbonate. the result would be water (H O). The acid is then said to be 2 At the lungs, the bicarbonate is changed back to carbon buffered, or rendered neutral (i.e., not having an electrical dioxide and water. The dissolved carbon dioxide off-gasses charge) once it combined with a base to form water. and the hemoglobin releases its carbon dioxide. The carbon Trying to describe the different amounts of acidity or dioxide then diffuses across the alveolar membrane and into alkalinity in a solution can be diffi cult, since there can be as the alveolar air, ready for exhalation. The transport of car- much as a thousand-fold difference from one extreme to the bon dioxide is affected by many factors including both the other. Practically speaking, using such a range is diffi cult. To amount of carbon dioxide produced by the cells (metabolism ease the process of describing the strengths of acids and rate) and the amount of blood volume circulated through bases, the pH scale (abbreviated for potential hydrogen) was the lungs. If the patient is hypotensive, there is less blood developed to describe the differing degrees of acidity or alka- circulating through the lungs and reduced transportation of linity. Mathematically, pH is the negative logarithm of the carbon dioxide to the lungs. Similarly, if the patient has hem- hydrogen ion concentration (pH log10[H]). The range orrhaged than there are fewer red blood cells, which means of pH is from 0 to 14, with 7 being neutral; pure distilled less hemoglobin to bind oxygen and plasma to carry the car- water is neutral. A weak acid has a pH closer to 7, somewhere bon dioxide. in the range of 5 to 7, whereas a weak base has a pH some- These factors culminate to increase carbon dioxide levels where in the 7 to 9 range. Human blood has a pH of 7.35 in the tissues. Carbon dioxide, together with water, forms a to 7.45, and is slightly alkaline. When the concentration of weak acid called carbonic acid (H CO ). The level of carbonic hydrogen ions increases, the solution becomes more acidic, 2 3 acid in the body is referred to as the “acid load.” and the pH decreases. When the concentration of hydrogen During any form of shock there is an increase in the ions decreases, the solution becomes more basic, and the pH body’s acid load. An increased acid level in the body can have increases (Figure 25-5). devastating effects to the normal metabolic functions of the Excessive amounts of acid in the tissues, in sum total body if not corrected. called an acid load, can be devastating to proteins within the cells. Excess acid can eventually break down (i.e., dena- Acid–Base Balance ture) proteins in the cells and eventually lead to cell death or necrosis. Acids are created in the course of both aerobic (with oxygen) Acid is eliminated from the interstitial space when the and anaerobic (without oxygen) metabolism. The majority of acid dilates the capillary beds. The acid passes into the capil- acid in the body is formed when excess carbon dioxide reacts lary bed and the acid is washed out in the blood. Upon enter- with water to form carbonic acid (H CO ) before conversion 2 3 ing the bloodstream, the acid can now be acted upon by the into bicarbonate. It is called the respiratory acid as it is the body’s buffering mechanisms. intermediary step in carbon dioxide transport. Other acids (e.g., lactic acid and pyruvic acid formed during anaerobic metabolism, and amino acids formed by the breakdown/ Buffering Systems oxidation of proteins) are called the metabolic acids. Regard- Any acid, whether metabolic or respiratory, entering the less of the source, an overabundance of acid can interfere bloodstream immediately encounters the three chemical buf- with the normal enzyme action within the cells.Acid levels fers that circulate throughout the body in the bloodstream. must be controlled by the body. Bicarbonate (HCO –), the most common chemical buffer, 3 An acid, by defi nition, is a molecule that has a proton almost instantaneously couples and neutralizes the acid (a positively charged atomic particle) that is not orbited by a (H), releasing heat in the process. The result is carbonic paired negatively charged atomic particle called an electron. acid (H O ). Carbonic acid then reverts into water (H O) and 2 3 2 The particle that exists in nature with one proton is the hydro- carbon dioxide (CO ) in the lungs. The water (H O) is then 2 2 gen particle and thus hydrogen is considered a primary acid. either absorbed or excreted by the kidneys and the carbon And acids are chemical compounds with positively charged dioxide (CO ) is exhaled in the breath. 2 hydrogen (H) particles or ions attached; ions being charged While bicarbonate is a powerful buffer, the amount of particles. Being positively charged, these hydrogen ions are bicarbonate in the bloodstream is limited and only provides extremely reactive, meaning that the hydrogen ion wants to approximately one half of the blood buffering capacity. Ventilation 495 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. [OH– 100 10–1 10–2 10–3 10–4 10–5 10–6 10–7 10–8 10–9 10–10 10–11 10–12 10–13 10–14 ] [OH–] Neutral [ H+ ] = [OH–] Increasing alkalinity Increasing acidity OH– H+ [H+] 10–14 10–13 10–12 10–11 10–10 10–9 10–8 10–7 10–6 10–5 10–4 10–3 10–2 10–1 100 [H +] pH 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 pH Oven Milk of cleaner Magnesia Coffee Lemon juice; (pH 13.5) (pH 10.5) (pH 5) gastric juice (pH 2) Urine Grapefruit (pH 5-8) Household juice (pH 3) ammonia Saliva; milk Sauerkraut (pH 11.5-11.9) (pH 6.5) (pH 3.5) Household Distilled Tomato juice bleach (pH 12) water (pH 7) (pH 4.2) Human blood; semen (pH 7.4) Egg white (pH 8) Saltwater (pH 8.4) Figure 25-5 pH scale with common acids and bases shown. Another chemical buffer, phosphate (PO ), also helps to buf- metabolism, there are two other ways the body can compen- 4 fer acids. Phosphate buffers bind with acid and carry the acid sate for increased acid production. Both respiratory compen- to the kidneys to be excreted, thus making urine acidic. sation and renal compensation kick in during times when the Finally, the proteins in the blood have a limited ability to body is producing additional acids, whether through increased buffer acid. All blood proteins, including albumin the most metabolic load, disease, or lack of oxygen. The three means of abundant blood protein, are made of chains of amino acids. buffering—chemical, respiratory, and renal—are interlinked These amino acids became neutralized when bonded in chains, and any weakness in one is compensated for by the others. but these proteins are capable of accepting more acids. There- fore, albumin is important to helping maintain an acid–base Respiratory Compensation balance. Albumin is so important that patients who have liver The lungs also have an ability to help rid the body of acid by disease, and subsequently reduced albumin, are more likely to driving the acid–bicarbonate formula. The acid–bicarbonate have problems with maintaining acid–base balance. reaction is easily reversible, releasing acid back into the blood- Blood proteins also include the hemoglobin molecules stream in the form of carbonic acid (H CO ) (Figure 25-6). 2 3 contained within the red blood cells (erythrocytes). Hemo- Sensitive central chemoreceptors monitor cerebrospinal fl uid globin can preferentially bind to either oxygen (O ) or acid (CSF) for an increase in carbonic acid, the respiratory acid, 2 (H), and therefore it releases its oxygen at the capillary and stimulate the medulla to increase respirations. Increased level and picks up acid at the venous side for removal in the respirations increase removal of carbon dioxide and drive the lungs or kidneys. Patients who have lost large volumes of formula to the left, forcing the conversion of acids into bicar- blood will have diffi culty with maintaining an acid–base bal- bonate, then carbon dioxide and water, which are removed ance because they have lost hemoglobin. through ventilation and urination. This process of increasing In addition to the chemical buffering that occurs to the respiratory rate in response to increased acidity of the cere- handle the day-to-day production of acids in response to bral spinal fl uid occurs rapidly, within several minutes. 496 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. H H H – the environment is slightly more acidic than in the central cir- + O C O + O C C H H O O O + O H culation. The process of cellular respirartion starts with meta- O O bolically active cells. These cells produce acid as one of the Carbon dioxide Water Acid Carbonic acid Bicarbonate by-products of metabolism. These cells also need more oxygen to sustain their aerobic (with oxygen) metabolism. The acid Figure 25-6 The acid–bicarbonate reaction. causes the capillary beds to dilate, permitting more oxygen- Increased ventilation forces this chemical carrying hemoglobin red blood cells in the blood to enter the equation to move to the left, increasing capillary. Once the blood is in the capillary bed, and in the production of carbon dioxide and water, which are presence of the acid, the oxygen is released from the hemoglo- then removed from the body. bin and moved into the cells. The use of oxygen in the cell is a process called cellular respiration. Renal Compensation A problem occurs when the blood in the central circula- tion becomes acidotic from a large “acid load” developing In the triad of buffering systems, the kidneys are the last within the body. Under normal conditions the acid in the line of defense. When carbonic acid reaches the kidneys, an blood, as carbonic acid, changes to carbon dioxide, diffuses in enzyme called carbonic anhydrase (an- – “without”, hydra – the alveoli, and is exhaled. With the acid eliminated from the “water”, -ase – “enzyme”) breaks the carbonic acid down into blood, the oxygen in the alveoli can be attached to hemoglo- bicarbonate (HCO –) and acid (H). The acid is excreted in 3 bin and carried out to the capillary beds. If the acid load in the the urine. In the process, the bicarbonate (HCO –) is regener- 3 central circulation is too great (e.g., secondary to hypoventi- ated for use in the bloodstream. The kidneys also can create lation or an increase in metabolic acids), then the oxygen will ammonia from the breakdown of the amino acid glutamine not be released into the tissues and the patient may experi- by the enzyme glutaminase, an enzyme that works best in an ence hypoxemia. Due to the effect of acid and temperature on acidic environment. Ammonia (NH ) then couples with acid 3 the oxyhemoglobin curve described in Figure 25-4, the oxy- (H) to become ammonium (NH ) and is excreted in the 4 gen saturation of a patient who has a fever or who has a large urine. Ammonium is a volatile acid, meaning that it off- gasses acid load, as is the case with a septic patient from a severe into the atmosphere and gives urine its distinctive odor. infection, will be lower than expected. The oxygen saturation This process of enzyme activation, reabsorption of bicar- may remain lower than expected despite the presence of high- bonate, and excretion |
of acids can take up to 49 hours to fully fl ow oxygen via nonrebreather face mask until the underlying activate. For this reason, compensation by the kidneys is inef- metabolic cause—in this case, the infection—is treated. fective during an acute emergency. Renal compensation only comes into action in patients who are chronically ill or who Acidosis and Medication have been acutely ill for several days. Acidosis, excessive acid in the system, can have a profound Effects of an Acidic Environment effect upon the body’s uptake, distribution, and the effectiveness The effi ciency of all of the body’s chemical processes, of medications administered by the Paramedic as well. Once a whether in the bloodstream, within the cells, or in the space medication is in the bloodstream and enters the interstitial space between the cells, depends on the local pH where the process it must cross the cell wall, a lipid–protein matrix. This semiper- takes place. If the local environment becomes too acidic or meable membrane readily accepts those medications that are not too basic, the chemical process may not occur at all. Trans- ionized (i.e., did not dissolve in solution). These “lipid-soluble” port of materials across cell membranes may also not occur medications easily diffuse across the lipid–protein cell mem- if the pH of the blood is too far outside the normal range. brane (i.e., “like dissolves like”). The problem occurs when a This can affect important body functions (e.g., produce car- medication enters the bloodstream and is dissolved, meaning diac dysrhythmias, affect oxygen transport, and affect muscle the medication becomes divided into two charged or “ionized” strength). Two important areas pertaining to Paramedic prac- portions. Some medications start as a salt and then dissolve in tice are oxygen transport and the effect of medications. solution to become ionized as either a weak acid or weak base. These ionized (charged) medications are repelled by the cell Acidosis and Oxygen Transport membrane and are called lipophobic (lipo- – “fat”, phobic – “fear”) medications. Lipophobic medications require carriers or As discussed earlier in this chapter, oxygen is picked up by the other compounds (e.g., bicarbonate or an amino acid) to carry hemoglobin in the red blood cells and transported to the tissues the medication into the cell. When the surrounding tissues are where it is released and used to produce energy. Hemoglobin’s acidotic, the medication is not dissolved normally and absorp- attraction, or affi nity, for oxygen is due to the iron molecules tion is reduced, thus reducing the drug’s effi ciency. that make up the hemoglobin. However, acids have a greater affi nity for oxygen. When acid is present, it will cause oxygen to separate (dissociate) from the hemoglobin. This phenom- Acid–Base Disorders enon, called the Bohr effect, is responsible for oxygen entering Changes in the acid–base balance in the body can have dra- the tissues at the cellular level in the interstitial space, where matic effects on the patient’s signs, symptoms, physiology, Ventilation 497 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. and the effects of medications on the patient. Even in the brief and ventilation. This may include administration of supple- patient contact time as part of many EMS calls, the Paramedic mental oxygen or invasive airway management maneuvers as can detect subtle signs of these derangements and initiate discussed in previous chapters. treatment that can prevent or slow catastrophic deterioration in the patient’s condition. These disorders are typically identi- fi ed through either an arterial blood gas or a venous blood gas, Metabolic Acidosis where a blood sample from either an artery or a vein is analyzed During metabolism, the body makes acids other than carbon for the pH, the partial pressures of carbon dioxide and oxygen dioxide. These metabolic acids can cause systemic acidosis (pCO and PO ), the bicarbonate, and the oxygen saturation. as well. The quintessential example of metabolic acidosis is 2 2 These parameters are examined to assess for an acid–base dis- the patient experiencing diabetic ketoacidosis. During hypo- order. While the interpretation of arterial and venous blood gas glycemic conditions, the body breaks down fats for energy is outside the scope of the typical street Paramedic, there are and produces ketonic acids in the process, leading to ketoaci- several causes for each and associated signs and symptoms. dosis, or ketonic acids in the blood. Other causes of metabolic The blood can either become acidotic if the pH falls acidosis include cyanide poisoning and carbon monoxide poi- below 7.35 or alkalemic if the pH rises above 7.45. Each of soning. Both of these conditions deprive the cells of oxygen these main disorders has respiratory causes and metabolic and force anaerobic (without oxygen) respiration. causes for the acidosis and alkalosis. Therefore, the four main While too much lactic acid, pyruvic acid, or ketonic acid acid–base disorders, in order of most common to least com- can produce metabolic acidosis, the absence of bicarbonate mon for Paramedics, are respiratory acidosis, metabolic aci- can also result in a relative metabolic acidosis. Under normal dosis, metabolic alkalosis, and respiratory alkalosis. conditions, the kidneys and the bowels reabsorb bicarbonate, making it available for reuse. Therefore, any gastrointestinal Acidosis or urinary disease can cause serious problems with maintain- ing acid–base balance. For example, the gallbladder secretes The blood becomes acidotic if the pH falls below 7.35. As bicarbonate to neutralize the acid created by the stomach. previously discussed, the blood in the capillaries is slightly This bicarbonate is then reabsorbed in the intestines. When more acidotic than the blood in the central circulation, which massive or persistent diarrhea occurs, then the intestines can- assists in the off-loading of oxygen and removal of carbon not reabsorb the bicarbonate. When a patient experiences dioxide from the tissues. Acidosis can occur as a result of renal failure, the kidneys cannot absorb the bicarbonate that either problems with the respiratory acids or the metabolic is excreted into the urine. The patient may become acidotic acids. It is possible to have a mixed respiratory and metabolic from the lack of the bicarbonate buffer. cause for a patient’s acidosis when a chronically ill patient Metabolic acidosis can also be caused by ingestion of has an acute exacerbation of her disease or when more than substances that are toxic or in toxic doses. Certain alcohols one active disease process is present. cannot be metabolized by the body and produce metabolic acids as a result of this incomplete metabolism. Respiratory Acidosis Aspirin is another medication that can lead to acidosis. The problem of respiratory acidosis can be further subdivided Aspirin is a medication that many people take to decrease into two categories: either too much carbonic acid production the risk of a heart attack, whereas some people take it as an or too little ventilation. The classic case of too much carbonic analgesic. Aspirin is the active ingredient in many over the acid production is the patient with a fever, pyrexia, whose counter (OTC) medications. In high doses, aspirin, (chemi- body is hypermetabolic. The acute nature of fever causes the cal name: acetylsalicylic acid and abbreviated as ASA) can body’s metabolism to increase, producing additional carbon cause metabolic acidosis. In severe cases of aspirin overdose dioxide and other by-products. aspirin inhibits the respiratory center in the medulla, leading The more traditional cause of respiratory acidosis is to hypoventilation and compounding the metabolic acidosis hypoventilation. Conditions such as strokes, brain trauma, with a respiratory acidosis. and drug intoxication—especially with opiates—can depress Treatment of acidosis from a metabolic cause typically the respiratory drive at the respiratory center in the medulla. involves fi rst ensuring adequate circulation. This may include Spinal cord trauma and diseases that affect the nerves or the administering intravenous fl uids, administering medica- muscles can cause either the respiratory muscles or the nerves tions to increase the patient’s blood pressure, administering controlling the respiratory muscles to provide inadequate antibiotics to treat infection, or performing chest compres- ventilation, which in turn causes hypoventilation. Illness and sions during cardiac arrest. These supportive measures help injury to the lungs themselves can result in hypoventilation. the body resolve the acidosis naturally. Sodium bicarbonate Any condition, either traumatic or medical, that impairs gas is sometimes administered intravenously in an attempt to exchange reduces the lungs’ ability to exchange oxygen and correct a severe metabolic acidosis by providing additional carbon dioxide, producing a respiratory acidosis. bicarbonate to buffer the acid. Treatments for the patient experiencing respiratory aci- As acidotic patients tend to hyperventilate as a way of dosis focus on ensuring the patient has adequate oxygenation compensating for the metabolic acidosis, if the Paramedic 498 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. needs to secure the airway, the Paramedic must remember to (e.g., when a person jumps up from a resting position and either ventilate the patient at a higher rate or set the respi- runs a quarter mile sprint), the respiratory rate increases ratory rate on the ventilator to a higher-than-normal rate in rapidly in response to the increased metabolic CO produc- 2 order to maintain an adequate ventilatory rate for that com- tion. At the end of the race, when the metabolic production pensation. If too low of a respiratory rate is provided, and the of CO decreases, the respiratory rate will decrease to the 2 underlying metabolic process is not corrected, the patient will baseline rate over the course of several minutes. In some continue to become more acidotic until the patient goes into conditions, however, there is a mismatch between the respi- a cardiac arrest. Cardiac arrest in these cases often does not ratory rate and CO production, with the patient breathing at 2 respond to treatment because of the severe acidosis. a faster rate than required to handle the production of CO . 2 This increased minute ventilation lowers the CO level, pro- 2 Alkalosis ducing the alkalosis. When a patient has a condition that The blood becomes alkalotic if the pH rises above 7.45. As causes metabolic acidosis, this mechanism compensates for with acidosis, this can be due to either a respiratory or meta- the acidosis and helps move the pH back toward the normal bolic cause. Alkalosis from a metabolic cause occurs more range. However, when the patient does not have an existing often than from respiratory etiologies. metabolic acidosis, this increased ventilation stimulus pro- duces the respiratory alkalosis. Metabolic Alkalosis There are several causes for the increased stimulation. Normally, if hypoxemia occurs in the central circulation, Metabolic alkalosis is caused by an increase in the produc- receptors in the aorta and carotid arteries will signal the tion of bicarbonate in the blood. This can be due to a meta- respiratory center to increase the respiratory rate in order to bolic process in the body and can also be due to increased compensate for the decreased oxygenation. However, in some kidney reabsorption of bicarbonate from the urine. Common situations, the central circulation is not hypoxemic. However, causes of metabolic alkalosis include severe volume deple- the tissues are hypoxic, and cause an increase in respiratory tion and acid loss, as occurs in dehydration from vomiting, rate. Any condition that decreases the off-loading of oxy- and electrolyte disturbances (e.g., low potassium), which gen at the tissue level (e.g., shock or anemia) can cause an triggers reabsorption of bicarbonate by the kidneys. Certain increase in the respiratory rate. endocrine disorders can also produce a metabolic alkalosis A second abnormal stimulus for increased ventilation by decreasing the serum potassium level. The use of some can occur with abnormal stimulation of the stretch |
receptors diuretics, specifi cally those that spill potassium into the urine located in the alveoli and smaller air passages in the lungs. (e.g., potassium wasting diuretics), can cause a metabolic Normally, the stretch receptors help signal the start and stop alkalosis because they cause an increase in reabsorption of of ventilation. However, in the case of irritation of the alve- bicarbonate. oli from pneumonia, pleural effusion (abnormal liquid in- Treatment of metabolic alkalosis depends upon the between the pleural layers), or congestion in the pulmonary cause. In the case of volume depletion (e.g., from vomit- capillaries, the stretch receptors can trigger increased ventila- ing, diarrhea, or overdiuresis), administering normal saline tion, producing a respiratory alkalosis. will help correct the volume loss. It is important to moni- The respiratory center can be directly stimulated by a tor the patient’s oxygenation, as the body’s primary means of variety of conditions and produce increased ventilation. Cer- compensating for a metabolic alkalosis is to hypoventilate, tain toxins, either ingested or produced by other conditions producing a mild respiratory acidosis to compensate for the (e.g., liver failure or renal failure) can trigger increased venti- metabolic alkalosis. In patients with normal respiratory func- lation. Fever or the toxins in sepsis can also increase ventila- tion, the effect of the hypoventilation is minimal. However, tion and produce a respiratory alkalosis. Certain hormones in patients who have a signifi cant respiratory condition (e.g., can also stimulate increased ventilation. This occurs as a chronic obstructive pulmonary disease (COPD)), hypoventi- normal part of pregnancy to increase respiratory rate late in lation may not be tolerated well and the patient may become pregnancy to compensate for diffi culty in fully expanding the hypoxic. Supplemental oxygen may be required to treat the lungs due to the growing fetus. Changes in blood chemistry hypoxia. In patients who are paralyzed and on a ventilator, that occur when at altitude also produce a mild hyperventila- the respiratory rate can be decreased to help treat the meta- tion to compensate for the lower partial pressure of oxygen bolic alkalosis. at high altitude. Respiratory Alkalosis Finally, psychologically induced hyperventilation can occur as a response to fear, anxiety, pain, or any number of Respiratory alkalosis occurs when ventilation is greater than emotional stressors. This increased respiratory rate can be the body’s CO production. As previously discussed, the CO 2 2 either involuntary or voluntary and often responds to calming generated by the body is primarily removed by the respi- and reassurance. With severe hyperventilation, the decrease ratory system. Changes in the respiratory rate occur very in blood CO causes vasoconstriction of cerebral blood ves- 2 rapidly in response to an increase or decrease in the circu- sels, reducing blood fl ow. In some cases, this can cause light- lating CO level. When the metabolic rate increases quickly 2 headedness or even syncope. Ventilation 499 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. in Chapter 16 and during the airway management chapters Street Smart (Chapters 22 and 23). In this section, we will discuss some of the objective measures of oxygenation and ventilation, including pulse oximetry, capnography, co-oximetry, and It is very easy to blame hyperventilation on a arterial blood gas sampling. psychological cause. Be aware that many other conditions can produce hyperventilation, including Pulse Oximetry hypoxia, shock, and sepsis. Search for these Pulse oximetry is a non-invasive measure of the percentage of causes during your patient assessment and treat hemoglobin sites in the red blood cells that are bound to oxy- gen, or oxyhemoglobin. This percentage of oxyhemoglobin is them appropriately. Do not allow the patient to called oxygen saturation and is abbreviated as SpO . A normal 2 breathe into a paper bag or an oxygen mask that SpO is between 95% and 100%. An SpO reading between 2 2 is disconnected from supplemental oxygen! This 90% and 95% indicates mild hypoxemia, and a reading between 85% and 90% indicates moderate hypoxemia. A reading below rebreathing will produce an abnormal increase in CO2. 85% indicates severe hypoxemia requiring intervention by the For the patient that is hyperventilating in response to Paramedic. There are two ways to report oxygen saturation: a pathologic cause, this increase in CO2 may produce One is displaying a quantitative measure of the oxygen satu- unconsciousness, profound metabolic derangements, ration and the other is displaying the oxygen saturation as a waveform over time. For oximeters that only display a numeri- and cardiac arrest. cal value, there is an indication of signal strength that provides the Paramedic with an indication of the strength of the blood Treatment of respiratory alkalosis depends on the cause. fl ow across the sensor. For oximeters that provide a waveform If the patient is hypoxic or there is a reason for tissue hypoxia display in addition to the numerical value, the shape of the (e.g., shock), then providing supplemental oxygen or treat- waveform provides the Paramedic with a visual indication of ment of shock may improve the alkalosis. If psychogenic the strength of the blood fl ow across the sensor (Figure 25-7). causes are present, attempt to calm the patient, provide reas- Technology surance, and appropriately treat pain and anxiety. Consider other respiratory or central causes when developing a para- Measurement of the SpO involves beaming a light wave 2 medical diagnosis, ensure the patient’s ABCs, and provide across the patient’s capillary bed and detecting the wave- supportive care. length on the opposite side of the capillary bed. The light Mixed Disorders The four acid–base disturbances should not be thought of as isolated entities. In reality, the body is complex and will respond both acutely and chronically to compensate for these dysfunctions. Some disease processes, or combination of disease processes, may cause a mixed acid–base disorder, where a primary disorder (e.g., respiratory acidosis) is par- tially compensated by the body by another disorder (e.g., a metabolic alkalosis). In some cases, the acidosis and alkalo- sis can have both a respiratory and metabolic cause (e.g., a respiratory and metabolic acidosis that can occur with some conditions). These disorders can be challenging to sort out. When in doubt, fall back to the ABCs and ensure the patient has a patent airway, is well ventilated and oxygenated, and is not in shock. This can be easily summarized as supporting the ABCs. This initial attempt at resuscitation and stabilization can go a long way in improving the patient’s condition. Assessment of Oxygenation and Ventilation The Paramedic has several tools at her disposal to help assess Figure 25-7 Pulse oximeters may display a oxygenation and ventilation in the critical patient. Clinical numerical indication of SpO2 or waveform display assessment of oxygenation and ventilation was discussed of SpO2. 500 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. wave is combined red and infrared frequencies. As the wave SpO reading (Figure 25-8). The waveform amplitude fl uc- 2 passes through the capillary bed, the light is absorbed by the tuates normally, corresponding to the fl ow of blood through hemoglobin differently depending on if it is in the oxyhemo- the capillary bed. If the Paramedic encounters a poor quality globin form or the deoxyhemoglobin form. The oxyhemo- waveform (Figure 25-9), the Paramedic will need to place the globin form absorbs more infrared light than red (therefore sensor on a different site. explaining the bright red color of oxygenated blood) and deoxyhemoglobin absorbs more red light than infrared. The Clinical Application wavelengths at the light source are known and compared to There are several factors that affect the accuracy of the wave- the wavelengths detected at the sensor. The ratio between the form or the perfusion index. In low blood fl ow states (e.g., wavelengths transmitted and received is compared with a hypotension from shock or cardiac arrest), there may not be database of known values and is used to calculate the SpO . a suffi cient movement of blood through the capillary bed to 2 These known values are only available in the range of 70% to provide an accurate reading. Decreased capillary blood fl ow 100% saturation as this information was derived from actual can also occur when the sensor site is cold and the blood ves- patients. sels are constricted. Vasoconstriction is a normal response The most common source used to measure SpO is the to cold, shunting warm blood toward the core to maintain 2 tip of a fi nger. Light travels easily through the fi ngertip and a normal body temperature; however, it can be problematic the capillary bed is relatively superfi cial to the skin surface. when attempting to obtain an accurate SpO reading. Vibra- 2 Alternatively, the earlobe can also be used for a similar rea- tion from shivering and motion artifact during transport may son. Two other sites include tip of the toes, useful in children, also affect the quality of the waveform, although this is not and the skin on the forehead, useful in hypothermic patients. as much of an issue with the later models of pulse oximeters. The strength of the signal detected by the pulse oximeter Nail polish may affect the ability of the light to pass through is reported as the perfusion index on oximeters that do not the fi ngertip and may need to be removed if a poor waveform display a waveform. The perfusion index is measured from or inadequate perfusion index is noted. Finally, the pulse oxi- 0.02% to 20%, with the larger number indicating a stronger meter is inaccurate below an SpO of 70% because the refer- 2 signal. The higher the perfusion index, the more accurate the ence database in the machine does not contain information reading. Therefore, when using device pulse oximeter, the below 70%. Paramedic can use the perfusion index indicator to know if A normal SpO reading doesn’t mean the patient does not 2 the pulse SpO reading displayed is an accurate reading. In require supplemental oxygen. While anemia, or decreased 2 some cases, the Paramedic will need to try several different hemoglobin, does not affect the SpO , total blood oxy- 2 sites before obtaining an accurate SpO reading. The pulse gen content—and therefore the delivery of oxygen to the 2 rate is calculated from the time between peaks of the fl uctuat- tissues—is decreased. Total blood oxygen content depends ing pulse oximetry wave. on the amount of hemoglobin in the blood and the amount For devices that display a waveform, the shape of the of oxygen diffused into the blood. The total amount of dis- waveform can be used to determine the accuracy of the solved oxygen in the blood can be increased by administering Figure 25-8 Normal pulse oximetry waveform. Ventilation 501 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Figure 25-9 Poor waveform that affects the accuracy of the SpO2 reading. supplemental oxygen to patients suspected of anemia from are available that can detect the presence of these two condi- acute blood loss, and may help prevent tissue hypoxia from tions. This will be discussed later in this chapter. inadequate oxygen transport. Patients in respiratory distress Pulse oximetry also does not provide an indication or or shock often increase their respiratory rate and pulse rate |
in measure of the patient’s ventilatory status. This is especially order to move more oxygen into the blood and circulate more true when the patient is on high-fl ow supplemental oxygen. oxygen to the tissues in response to a lack of oxygen at the The supplemental oxygen can replace the other gasses in the tissues. In many cases, a patient in respiratory distress will lungs, increasing the oxygen gradient between the alveoli be able to improve his SpO by increasing his respiratory rate and the pulmonary capillary blood. This encourages trans- 2 and compensating for his hypoxemia. The use of supplemen- port of oxygen into the blood, even when there is insuffi cient tal oxygen should not be based on SpO alone, but also on airfl ow in and out of the lungs. That airfl ow in and out of 2 other clinical assessment of respiratory distress as discussed the lungs (ventilation) is required to remove carbon dioxide in Chapter 16. from the system. With inadequate airfl ow, the carbon dioxide Certain conditions will also affect the SpO reading. Car- levels increase in the alveoli, decreasing the gradient from 2 bon monoxide also attaches to hemoglobin; because, it has the blood to the alveoli, reducing carbon dioxide transport a signifi cantly higher affi nity than oxygen. This means that and therefore increasing blood carbon dioxide levels. Pulse carbon monoxide is 200 times more likely to attach to the oximetry alone would not detect this hypoventilation. This hemoglobin molecule than oxygen, creating carboxyhemo- is well illustrated in a case report from 1993, approximately globin. Though the hemoglobin is bound to carbon monoxide 5 to 10 years after pulse oximetry’s introduction into regular rather than oxygen, the wavelengths of light used in fi rst gen- clinical use.3 In this case report, an elderly woman was moni- eration pulse oximeters are not capable of differentiating the tored after a surgical procedure with blood pressure, ECG, two hemoglobins. A patient who has had carbon monoxide and pulse oximetry on supplemental oxygen after her proce- poisoning may demonstrate a normal SpO . Other forms of dure. The patient became less and less responsive. Finally, the 2 hemoglobin (more specifi cally, one form called methemoglo- nurses could not wake the patient up. The patient was seen by bin) will also provide a false SpO reading. Methemoglobin is the anesthesiologist, was noted to be ventilating very poorly, 2 a form of hemoglobin that is chemically different from hemo- and was intubated and placed in the ICU until she woke up. globin and cannot carry oxygen. This is often the form hemo- The pCO on her blood gas was 280 mmHg, with a normal 2 globin takes as it reaches the end of its useful life. A small pCO at 40 mmHg. Most patients who acutely develop a 2 amount of methemoglobin is present in the blood at all times. pCO over 80 or 90 mmHg become minimally responsive or 2 However, the level can be markedly increased in some condi- unresponsive. The patient’s SpO never fell below 96%. The 2 tions, decreasing oxygen transport. Fortunately, co-oximeters take-home message from this case is while pulse oximetry is 502 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. an excellent tool to help assess a patient’s oxygenation and endotracheal confi rmation then utilize continuous waveform ability to oxygenate a patient, it cannot detect hypercapnea, capnography or capnometers. or a rise in CO , from inadequate ventilation. This is where Quantitative capnometers provide a numerical value 2 capnography can help. for the EtCO , reporting the CO measurement at the end of 2 2 exhalation. In contrast, waveform capnography records the Capnography values of exhaled carbon dioxide throughout the inspiration– expiration cycle and graphs that value over time, producing a Capnography, the measurement of the amount of carbon diox- waveform that can be clinically useful to interpret. ide exhaled from the lungs, is a newer technology that can help guide the Paramedic with treatment in several clinical situa- tions. Several different methods of capnography are available Technology to measure exhaled carbon dioxide. The measurement often As previously described, the colorimetric capnometers uti- cited is the end-tidal carbon dioxide, which is the amount of lize a paper impregnated with a chemical that changes color carbon dioxide in the air at the end of exhalation. End-tidal depending upon the amount of carbon dioxide in the exhaled carbon dioxide is abbreviated as EtCO . The three methods of 2 air. For quantitative capnometry and waveform capnogra- measuring EtCO include colorimetric capnometry, quantita- 2 phy, the amount of carbon dioxide in exhaled air is found tive (numerical) capnometry, and waveform capnography. by shining a beam of infrared light through a sample of the Colorimetric capnometry is a familiar form of EtCO for 2 exhaled breath. The intensity of the light is then compared to many Paramedics. This device consists of a piece of litmus a measurement taken from an air sample that does not contain paper within the sensor’s body. This paper is impregnated with carbon dioxide. The certain wavelengths of infrared light are a chemical that changes color when exposed to exhaled car- absorbed by the presence of carbon dioxide compared to the bon dioxide (Figure 25-10). This device is placed in-line with air that does not contain carbon dioxide. This is converted the endotracheal tube immediately after endotracheal intuba- into a numerical measure of the carbon dioxide. tion to help confi rm that the the endotracheal tube is in the tra- Exhaled air for use in capnography or capnometer is chea. If the endotracheal tube is in the trachea the capnometer sampled in one of two different methods. Mainstream cap- should change color from purple up to yellow depending on nography involves placing the sensor in-line with the exhaled the amount of carbon dioxide in the exhaled air. One exception air stream and can only be used in intubated patients (Figure is when a patient has been in cardiac arrest for a prolonged 25-11a). The sensor is placed between the endotracheal tube period of time. In this situation, very little CO is transported 2 and the ventilation device (e.g., bag-valve mask assembly). to the lungs because of circulatory collapse, therefore there is The second method is called sidestream sampling. Side- little in the lungs and a low level in exhaled gas. stream capnography involves taking a sample of the exhaled The colorimetric capnometer is a qualitative device, air by aspirating a small amount of it from the exhaled air meaning it gives gross estimations of the presence or absence stream, either from the endotracheal tube or through the use of carbon dioxide and not specifi c levels of carbon dioxide. of a modifi ed nasal cannula (Figure 25-11b). Sidestream This, and other limitations, give colorimetric capnometry technology allows capnography to be used in patients who limited utility in the prehospital setting. Some Paramedics are not intubated. only use colorimetric capnometer as an initial method of One disadvantage to sidestream capnography/ capnometer is that there is some loss of carbon dioxide from the air sam- ple that occurs between the patient and the monitor. This is overcome in many capnography/capnometer devices by cali- brating the EtCO2 monitor whenever the monitor switches measurement methods from endotracheal measurements to nasal cannula. A second disadvantage of nasal cannula sidestream c apnography/capnometer is if the patient is receiving high- fl ow oxygen (e.g., using a nonrebreather or CPAP mask) at the time of sampling, the result will be artifi cially low because the high-fl ow oxygen blowing past the sampling port will wash out much of the carbon dioxide in the exhaled air. The sampled exhaled air is taken to a chamber where a beam of infrared light is directed through the sample. The carbon dioxide present in the air absorbs some of the infra- Figure 25-10 The EasyCap® colorimetric red light, changing the wavelength of the light that contin- capnometer. The color changes from purple when ues through to the sensor. This change in wavelength varies exposed to > 4 mmHg CO2, to tan, and then to with the amount of carbon dioxide present in the sample. The yellow when exposed to > 15 mmHg CO2. sample taken from exhaled air is compared with infrared light Ventilation 503 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. (a) (b) Figure 25-11 Mainstream versus sidestream sampling. (a) In mainstream capnography, the sensor is located between the endotracheal tube and the bag-mask assembly. (b) A modifi ed nasal cannula is used to sample carbon dioxide from exhaled air. beamed through a sample with a known concentration of car- Measured bon dioxide. This comparison determines the level of exhaled EtCO2 carbon dioxide in the patient’s breath. In the absence of respi- III ratory disease, this measure of exhaled carbon dioxide should be within 5 mmHg of the partial pressure of carbon dioxide β (PaCO ) of the patient’s arterial blood. α Alveolar 2 0 plateau Capnography: Waveform Interpretation II Unlike capnometers which either provide a visible color change or a numeric readout, a capnography provides a graph I Expiratory Inspiratory of the EtCO measurement as it changes during inspiration 2 upstroke downstroke and expiration (Figure 25-12), The capnography waveform has several components, each representing a phase. Respiratory Phase I is the respiratory baseline and occurs at the time baseline between inhalation and exhalation. It should be at zero, as it (should be 0 mmHg) represents the carbon dioxide in free air, that is found in the anatomical dead space in the lungs.4 The next part of the wave- Figure 25-12 Anatomy of a typical end-tidal form, Phase II, is also called the expiratory upstroke and rep- capnography waveform. resents the beginning of exhalation of air from the lungs that contains carbon dioxide. The third part of the waveform, known as Phase III or the alveolar plateau, represents exhalation of The fi rst angle on the waveform, the alpha angle, is the angle alveolar air during exhalation. The peak of this plateau at the between Phase I and II and indicates the correlation between end of exhalation is the EtCO measurement displayed on the ventilation and perfusion in the lung (i.e., the movement of air 2 monitor. The fi nal portion of the waveform is the inspiratory in and out versus the fl ow of blood through the lungs). The sec- downstroke or Phase 0, and represents the patient’s inspiration. ond angle, the beta angle, the angle between Phase III and 0, is During the inspiratory downstroke, the EtCO falls rapidly to usually close to a 90-degree angle. However, it will increase if 2 zero, as the inspired air should contain little carbon dioxide. the patient is rebreathing exhaled carbon dioxide, as can occur 504 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. if the oxygen fl ow rate on a nonrebreather is inadequate and the not only represents a signifi cant means of improving patient reservoir bag does not refi ll between breaths. safety but also is a risk management tool used to protect Para- medics from allegations of malpractice.. Clinical Application Changes in the shape of the |
capnography waveform can also provide valuable information to the Paramedic regard- The earliest clinical use of capnometry in the prehospital setting ing the patient’s respiratory disease, circulatory status, and was using colorimetric capnometer to confi rm proper place- equipment failure. For example, with severe bronchospasm, ment of the endotracheal tube after orotracheal or nasotracheal the patient will have diffi culty exhaling. This is refl ected in a intubation. After intubation, and auscultation of breath and epi- sloping of the alveolar plateau (often referred to as a “shark gastric sounds, the colorimetric capnometer is placed between fi n shape”) and a longer alveolar plateau (Figure 25-14) rep- the bag-valve mask assembly and the endotracheal tube and resenting the prolonged expiration that occurs in patients with the bag is squeezed several times. If the endotracheal tube is bronchospasm. As the patient is treated with medications that located within the trachea, then carbon dioxide should be pres- reduce the bronchospasm, the waveform should return to a ent in the exhaled air. If the endotracheal tube is located in the normal or near normal shape. esophagus, there should be no carbon dioxide in the exhaled For intubated and paralyzed patients, waveform capnog- air. If the endotracheal tube is located in the trachea, the cap- raphy can indicate when the paralytic medication is wearing nometer should turn from a purple color during inhalation to a off. As the paralytic medication wears off, the patient will start yellow color during patient exhalation. attempting to breathe. The Paramedic will fi rst notice this by The Paramedic should provide at least six ventilations observing a dip in the alveolar plateau as the patient attempts before relying on the colorimetric capnometer’s color change to take a shallow breath; an increasing carbon dioxide level to indicate proper position. In patients who have ingested car- stimulates the patient to breath (Figure 25-15). This will often bonated beverages, such as beer, just prior to intubation, it is precede muscular movement and provide an early indication of possible for the carbon dioxide in the stomach from the bev- erage to provide a false indication of the presence of carbon dioxide.5 While this is clinically an uncommon event, the Para- medic should be aware of this potential pitfall. Regardless of whether colorimetric capnometry or waveform capnography are used, the level of carbon dioxide present in the stomach in that situation will rapidly decrease to zero during ventilation, thus confi rming the endotracheal tube is in the esophagus. 0 Continuous waveform capnography can provide the Para- medic with an assurance that the properly placed endotracheal Figure 25-13 A sudden loss of the capnography tube remains in the trachea during transport. The prehospital waveform often signals dislodgement of the environment is full of situations wherein patient care can eas- endotracheal tube from the trachea. ily dislodge the properly placed endotracheal tube, from log- rolling the patient onto a backboard at the scene to moving the patient from the EMS stretcher to the emergency depart- ment gurney. When the patient is monitored with continuous waveform capnography, dislodgement of the endotracheal tube is immediately indicated by a loss of capnography waveform (Figure 25-13). As discussed in Chapter 24, a well-o xygenated patient without signifi cant respiratory disease can endure 0 nearly eight minutes of apnea time before her SpO falls below 2 90%. With the loss of exhalation waveform from continuous Figure 25-14 Characteristic shape of the waveform for a patient with bronchospasm. waveform capnography, the Paramedic immediately recognizes endotracheal tube dislodgement. This was well demonstrated clinically in a study that examined the rate of misplaced endo- tracheal tubes in intubated patients transported to their trauma center by various EMS services.6 Some EMS services had implemented endotracheal tube placement monitoring with continuous waveform capnography while others had not. In the group of patients that were monitored with continuous wave- 0 form capnography, zero patients arrived with an endotracheal tube in the esophagus compared with 23% of the patients in the Figure 25-15 The “curare cleft” in the alveolar group that was not monitored using continuous waveform cap- plateau is the fi rst sign that the paralytic nography. Continuous monitoring with waveform capnography medication is wearing off. Ventilation 505 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. the need to administer additional paralytic medication before of carbon dioxide in the blood or in the lungs, but because the patient begins to resist positive pressure ventilation by of the lack of carbon dioxide diffusion secondary to lack of coughing against inhalation, called “bucking” the ventilator. circulation due to cardiac arrest. Capnography or capnometry Waveform capnography can also alert the Paramedic alone may not be suffi cient to confi rm proper placement of to technical or equipment problems. From failure of valves the endotracheal tube in a patient who has been in cardiac in the bag-valve-mask assembly to kinking of the endotra- arrest for a prolonged period of time due to the lack of circu- cheal tube, equipment failure can reduce airfl ow both in lation. Once adequate chest compressions begin, the EtCO 2 inspiration and expiration and cause changes in the wave- rises as there is generally enough circulation to produce a form (Figure 25-16). This pattern is also seen in partial noticeable level of exhaled carbon dioxide. If the EtCO level 2 obstruction of the endotracheal tube which can occur with remains below 10 mmHg after 20 minutes of the usual resus- excessive mucus or other material in the airway. A raising citation efforts, there is a 0% chance of survival.7,8 baseline suggests that the patient may need deep endotracheal suctioning. A gradual rise in the Phase I baseline often indicates con- tamination of the sensor when using mainstream capnography (Figure 25-17). This can occur from either foreign material or a buildup of condensation on the sensor that changes the infrared light transmission across the exhaled air. Disconnect- ing and cleaning the sensor generally resolves this problem. 0 Capnography can also detect hyper- and hypoventila- tion, both in spontaneously breathing patients and ventilated Figure 25-16 Abnormalities in both the Phase III patients. A gradual decrease in the height of the waveform and 0 parts of the waveform may indicate kinking indicates hyperventilation (Figure 25-18a). This occurs as the or partial obstruction of the endotracheal tube. increased alveolar minute volume removes additional carbon dioxide, decreasing the amount of carbon dioxide in subse- quent breaths. This can be used during bag-valve ventilation to maintain a constant rate and depth to prevent hyperventi- lating the patient. Conversely, a gradual increase in the height of the waveform with a constant baseline indicates hypoventi- lation (Figure 25-18b) and may indicate to the Paramedic that he needs to intervene to improve the patient’s ventilation. 0 Another use for capnography is to predict the likelihood Figure 25-17 The gradual increase in of survival in cardiac arrest. The initial EtCO readings in a 2 respiratory baseline often indicates a problem patient in cardiac arrest are near zero, not because of the lack with the mainstream capnography sensor. ETCO2 mmHg 60 60 40 40 20 20 NORMAL TIMEBASE (a) ETCO2 mmHg 60 60 40 40 20 20 NORMAL TIMEBASE (b) Figure 25-18 Gradual changes in the waveform height while maintaining a zero baseline can indicate (a) hyperventilation or (b) hypoventilation. 506 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Upon return of spontaneous circulation, the EtCO level will when the patient has developed methemoglobinemia. Carbon 2 sharply rise, often before the pulse is palpable.9,10 Capnography monoxide differs from carbon dioxide in that carbon monox- has also been suggested to help guide the effectiveness of chest ide only has one oxygen atom in the molecule. Carbon mon- compressions in cardiac arrest. However, it is not known whether oxide attaches to the same site as oxygen on the hemoglobin this translates into improved survival from cardiac arrest.11 molecule, only it attaches 200 times stronger than oxygen. End-tidal carbon dioxide level will change with changes in This displaces oxygen and decreases the overall ability to the patient’s hemodynamics and may be a useful tool in guid- transport oxygen to the tissues. A pulse oximeter, however, ing trauma resuscitation.12 It is important to note that while will still see the hemoglobin as saturated, and report a nor- specifi c EtCO levels do not correspond to specifi c levels of mal SpO . Methemoglobinemia occurs when the hemoglobin 2 2 shock, sudden changes or trends can assist the Paramedic in molecule undergoes a change in its form that removes one guiding treatment. As previously discussed, EtCO will change electron from the atom. This form of hemoglobin cannot carry 2 with changes in blood fl ow due to decreased perfusion and car- oxygen. The pulse oximeter will often read falsely low SpO 2 bon dioxide transport to the lungs. The issue with using EtCO in patients with a low level of methemoglobinemia and falsely 2 in guiding trauma is the reading is not only dependent on cir- high SpO in higher percentages of methemoglobinemia.14 2 culatory fl ow, but also dependent on carbon dioxide transport Carboxyhemoglobin (COHgb) and methemoglobin from the blood into the alveoli and constant alveolar minute (MetHgb) levels are often obtained in the hospital using a sam- volume, which varies based on the tidal volume and ventilation ple of either arterial or venous blood and requiring a s pecial rate. Changes in EtCO levels should refl ect changes in circula- co-o ximeter. More recently, a non-invasive co-oximeter was 2 tion if the alveolar minute volume is held constant. For trauma developed to non-invasively measure SpO , COHb, and MetHB. 2 patients who have sustained a chest or respiratory system injury signifi cant enough to impede gas exchange, changes in Technology the EtCO reading may refl ect worsening pulmonary condition 2 The Masimo® RAD-57 was introduced as the fi rst handheld rather than circulatory status. Sublingual capnometry using non-invasive co-oximeter. Eight different wavelengths of light a non-invasive probe that sits underneath the tongue showed are transmitted through the capillary bed.15 Changes in the some promise in more accurately detecting tissue perfusion wavelength of these eight different beams are used to compute without relying on maintaining a constant ventilation minute a percentage of SpO , COHgb, and MetHgb in the blood in the 2 volume. However, the manufacturer recalled the probes and capillary bed. This particular co-oximeter also reports the per- the device is not currently available.13 fusion index, which is helpful in determining signal strength, Finally, capnography can be used during procedural seda- and ultimately the accuracy of the patient’s SpO . 2 tion as a way of monitoring the patient’s respiratory rate and ventilation status during the sedation. The most common use Clinical Applications for procedural sedation in the prehospital setting is for cardio- The Masimo® RAD-57 may show some promise in the pre- version, which involves applying an electric shock across the hospital environment in helping to triage a large number of chest to stop a fast heart rhythm, or when electrically pacing patients who may have been exposed to carbon monoxide, the patient, which involves periodically applying electricity thus minimizing transports.16 The Paramedic’s ability to across the chest to produce a mechanical cardiac contraction. non- invasively monitor COHgb levels in fi refi ghters during Both of these procedures are painful. Medications that are fi reground operations may detect elevated COHgb in inte- used for sedation also have the side effect of depressing res- rior fi refi ghters during both fi re suppression and overhaul piration and decreasing ventilation. As discussed in |
the case operations.17,18 This may impact fi refi ghter health by keeping study described in the pulse oximetry section, it is possible to fi refi ghters out of the rotation while treating mildly elevated have a well-oxygenated and poorly ventilated patient who can levels of COHgb, as it has been established that carbon mon- progress to respiratory failure. Capnography adds a level of oxide exposure can cause long-term cardiac effects.19 safety by providing a graphical representation of the patient’s respiratory rate, depth of respiration, and EtCO . As the patient 2 Arterial Blood Gas becomes more sedated, and ventilation deteriorates, the EtCO 2 will rise, providing an alert to the Paramedic that she may need The gold standard measurement of oxygenation and venti- to intervene by either assisting ventilations or reducing the lation in medicine before the advent of pulse oximetry and level of sedation before the patient suffers respiratory failure. capnography was the arterial blood gas (ABG). Even today, in the emergency department and critical care setting, the ABG provides a lot of useful information about not only the Co-oximetry patient’s oxygenation and ventilation, but also data used to As discussed under the section on pulse oximetry, one of the assess the patient for acid–base disorders. While the ABG is pitfalls of pulse oximetry is that other forms of hemoglobin the most accurate measure and provides a signifi cant amount can change the wavelength of the light beam in such a way of information, the process to obtain the ABG can be a pain- that it mimics oxyhemoglobin. Two situations where this can ful procedure for most patients. While ABG sampling is often occur are when a patient has carbon monoxide poisoning and not an EMS procedure, Paramedics working in a critical care Ventilation 507 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. transport environment will be exposed to blood gas analysis Table 25-2 Components of the Arterial and may need to use this information to guide therapy dur- Blood Gas ing transport. For Paramedics working in the traditional street EMS environment, conceptual knowledge of ABG analysis Component What Is Measured Normal Range will help them understand the underlying pathophysiology pH Amount of hydrogen atoms 7.35–7.45 present in their patient. in the blood sample Below 7.35 is academia What Is Measured? and above 7.45 is alkalemia The ABG sample is taken from a superfi cial artery and is rap- pCO2 Partial pressure of carbon dioxide 35–45 mmHg idly analyzed using a blood gas analyzer. The most common dissolved in the blood sample location for sampling is the radial artery at the wrist; how- Less than 35 is hypocapnea ever, the brachial artery near the elbow or the femoral artery and greater than 45 is in the groin can also be used to obtain a sample. Critical hypercapnea patients who are undergoing transport may have an arterial PO2 Partial pressure of oxygen 70–100 mmHg line (Figure 25-19) placed by the sending hospital to con- dissolved in the blood sample tinuously monitor the patient’s blood pressure and serve as Less than 70 is hypoxia and a means of painlessly acquiring multiple ABG samples in an greater than 100 is hyperoxia unstable patient. HCO - 3 Amount of bicarbonate ions in 22–30 mmol/L The ABG sample is measured for the pH, pCO , PO , the blood sample 2 2 bicarbonate (HCO –), and oxygen saturation. The ABG Less than 22 is hypocarbia 3 analyzer may also include serum electrolytes, lactate, glu- and greater than 30 is cose, hemoglobin, and base excess or defi cit (Table 25-2). hypercarbia The values from the ABG sample can be used to determine if the patient has an acid–base disorder and, if a disorder is <7.35 >7.45 pH present, identify the acid–base disorder. HCO3–<24 pCO2>40 HCO – 3 <24 pCO2<40 Interpretation of Arterial Blood Gasses Acidosis Alkalosis This section uses a simple method to identify the primary acid–base disorder (Figure 25-20). The primary acid–base Metabolic Respiratory Metabolic Respiratory disorder is the disorder that is the primary cause of the aca- Acidosis Acidosis Alkalosis Alkalosis demia or alkalemia. As previously discussed, the body will work to compensate for the primary disorder in an attempt to Figure 25-20 Algorithm for interpreting arterial blood gas.20 bring the arterial blood pH back toward normal. In reviewing the algorithm, notice that if the pH and bicarbonate move in the same direction (e.g., both increase or both decrease), then the primary disorder is a metabolic disorder. If the pH and the pCO move in opposite directions (e.g., pH decreases and the 2 pCO increases), then the primary disorder is respiratory. 2 An ABG sample taken from a patient returns with a pH of 7.25, a pCO of 60 mmHg, and an HCO – of 25 mmol/L. 2 3 Starting at the top, the pH is below 7.35, which moves toward the acidosis arm. Looking at the pCO of 60 mmHg, 2 this is greater than 45, indicating a primary respiratory aci- dosis. As previously discussed, this would likely be due to hypoventilation. Mixed disorders have a component of two primary acid– base disorders. In order to detect the presence of a mixed disorder, the Paramedic needs to determine the degree of compensation by the body for the primary disorder. If the degree of compensation is not as expected, this suggests a mixed disorder is present. There are two ways to determine the degree of compen- Figure 25-19 An arterial line painlessly sation. The fi rst is to use formulas to compare the measured allows multiple ABG samples as well as invasive values in the ABG with the expected values (Table 25-3). monitoring of the patient’s blood pressure during With this method, the Paramedic fi rst uses the algorithm in transport. (Photo courtesy of Keith D. Lamb, RRT) Figure 25-20 to determine the primary disorder. Next, the 508 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Table 25-3 Formulas used to Determine if the Paramedic looks in Table 25-3 to determine what formula to Patient Is Compensating for His Primary Disorder21 apply to determine compensation. For example, a Paramedic determines that her patient has a respiratory acidosis. Under Primary Disorder Expected Change respiratory acidosis in Table 25-3, the Paramedic computes Metabolic acidosis pCO2 1.5 [HCO – 3 ] 8 the expected bicarbonate using the formula for acute respira- (range of ± 2) tory acidosis. If the actual bicarbonate on the blood gas is Metabolic alkalosis pCO2 0.7 [HCO – 3 ] 20 different, then the Paramedic computes the expected bicar- (range of ± 5) bonate using the formula for chronic respiratory acidosis. If Respiratory acidosis Acute: HCO – 3 24 ((pCO2 – 40)/10) the expected value still is not close to the measured value, this Chronic: HCO – 3 24 4 ((pCO2 – 40)/10) suggests that a mixed acid–base disorder is present. Respiratory alkalosis Acute: HCO – 3 24 – 2 ((40 – pCO2)/10) A second method of determining the degree of compen- Chronic: HCO – 3 24 – 5 ((40 – pCO2)/10) sation is to use a nomogram (Figure 25-21) after using the (Range of ± 2) algorithm in Figure 25-20 to identify the primary disorder. pCO2 (mm Hg) 110 100 90 80 70 60 50 45 40 60 NORMAL 35 55 50 30 45 40 25 35 p 20 C 30 O2 RESP A IR C A ID TO O R S Y I 25 S 24 15 RESP A I 20 L R K A A T L O O R S Y IS LIC pCO2 AC ID OS ISAB O 10 15 ME T 10 5 NORMAL 0 7.00 7.10 7.20 7.30 7.40 7.50 7.60 7.70 7.80 Acidosis Alkalosis Arterial pH Figure 25-21 Acid–base interpretation nomogram. Ventilation 509 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Plasma (HCO3 ) mEq/L ME A TL AK BA OLO LIS CIS pCO2 (mm Hg) The pH is listed across the bottom of the chart, the HCO – is taken from a peripheral vein instead of an artery. This is 3 listed along the left side, and the curved lines are the values much less painful for the patient and can often be drawn for the pCO . The three values for the pH, HCO –, and pCO from an existing intravenous line. While the PO is dras- 2 3 2 2 are plotted on the chart. Depending on where the intersection tically different between an arterial and venous sample, of those three values falls on the chart, the shaded areas on the pH is approximately 0.04 less than the arterial sample, the nomogram will indicate the type of disorder present. If pCO is within 6 mmHg of the arterial sample, and HCO – is 2 3 the point falls outside the shaded area, this indicates a mixed within 1.5 mmol/L.22 While in some patients this may not disorder is present. adequately refl ect their acid–base status, in many patients this will provide suffi cient information to detect the pres- Venous Blood Gas ence of, and determine, the primary acid–base disorder with A venous blood gas is analyzed in the same way as an arte- less patient discomfort. rial blood gas. The difference between the arterial blood gas and venous blood gas in the venous blood gas sample is 510 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. This chapter has discussed several methods to objectively assess a patient’s oxygenation and ventilation through the use of pulse oximetry, capnography, co-oximetry, and arterial blood gas analysis. The technology and clinical applications of each of these devices were discussed as well as their limitations. The physiology of acid–base disorders and their effects was also discussed. As with all technology, it is important to remember to treat the patient as a whole and not rely solely on one device or technology in determining the paramedical diagnosis and developing an appropriate patient treatment plan. Key Points: • Acids are produced by either respiratory or • The lungs also have the ability to help rid metabolic processes. Although highly necessary for the body of acid. They do this by driving the human survival, a superfl uous amount of acid can acid–bicarbonate formula to the left by exhaling be dangerous to the cells. additional CO2. To do so, the lungs can increase • ventilation, which converts more carbonic acid An acid is a molecule that has a proton without a to CO2 and water. Chemoreceptors monitor paired negatively charged atom. This molecule, cerebrospinal fl uid for an increase in carbonic when exposed to nature, takes the form of a acid, followed by a stimulation of the medulla to positively charged hydrogen (H) ion with one increase respirations. proton. Bases are |
negatively charged molecules, sometimes called hydroxyl molecules (OH), which • The kidneys are the last line of defense when the accept the positively charged molecules of an acid three interlinked buffering systems are unable to to create a more neutral or buffered molecule. suffi ce. The kidneys perform two processes: They • break down excess carbonic acid into bicarbonate, A pH scale was developed in order to describe the which is reabsorbed into the bloodstream, and differing degrees of acidity or alkalinity. This scale excrete excess acids and ammonium in the urine. ranges from 0 to 14. The lower the number, the Kidney compensation is seen in chronically ill more acidotic a molecule, whereas the higher the patients and not acute emergencies due to the fact number, the more alkaline a molecule. A value of 7 that these processes take a long time to activate. is considered neutral. • • Hemoglobin, which is found in the blood, has a An acid that enters the bloodstream encounters high attraction to oxygen. It binds to oxygen and three chemical buffers: bicarbonate (HCO – 3 ), transports it to the body’s tissues, where it is phosphate (PO4) and blood proteins. Bicarbonate released. binds with an acid to eventually create water and CO2 that is eventually exhaled. Phosphate binds • Active cells need oxygen to survive. These cells with acid, which in turn gets excreted into the produce acid, which in turn dilates the capillaries kidneys. This leads to the acidity of urine. Blood and allows more oxygen bound to hemoglobin to proteins, including molecules like hemoglobin, enter. The acid then causes the oxygen to separate bind with acid from the veins and eventually are from its hemoglobin. removed in the lungs or kidneys. Ventilation 511 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. • If the acid in the blood is not released from patient can either produce too much carbonic acid, the body as CO2, oxygen will not attach to its which may cause the metabolism to race, or cause hemoglobin again and be carried out to the a patient to hypoventilate. Hypoventilation is, in capillaries. This will cause a patient to become part, due to certain damage caused by drug abuse, hypoxic. strokes, and brain injuries. • Acidosis, excessive acid in the body, can also hinder • During metabolism, the body makes a variety of the effects of a drug upon the body. If the tissues acids. The production of too many acids can cause are acidotic, it causes a decrease in drug absorption metabolic acidosis (i.e., diabetic ketoacidosis). The into the cell, thus reducing the drug’s effectiveness. body’s organs work together to maintain an acid– • base balance. Any illness or problem with the organs Acidosis can be caused by either respiratory or can deter this process. metabolic acids. In terms of respiratory acidosis, a Review Questions: 1. What two types of acid are products of aerobic 5. Describe the three chemical buffers found in and anaerobic metabolism and what are they the blood and how they help regulate pH. formed from? 6. How do the lungs compensate for an increase 2. By defi nition, what defi nes a substance as an in carbonic acid? acid or a base? What happens when an acid is 7. Using an oxyhemoglobin curve, defi ne the joined with a base? relationship between oxygen saturation and 3. Create a pH scale and label it with the following acid load. terms: weak acid, strong acid, neutral, weak 8. What are two causes of acidosis and how can the base, and strong base. Paramedic recognize them? 4. Explain how carbon dioxide is transported from the cells through the bloodstream and released into the exhaled air. Case Study Questions: Please refer to the Case Study at the beginning of the endotracheal tube in a spontaneously breathing chapter and answer the questions below: patient? 1. How could Mr. Byrnes be having respiratory 3. The Paramedic observes that Mr. Byrnes’ diffi culty and still have a 97% oximetry reading? capnography exhibits a shark fi n pattern. Explain 2. If Mr. Byrnes requires intubation, what this fi nding. methods exist to confi rm placement of the 512 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. References: 1. Merriam-Webster on-line medical dictionary. Available at: http:// 12. Kupnik D, Skok P. Capnometry in the prehospital setting: www2.merriam-webster.com/cgi-bin/mwmednlm?bookMed are we using its potential? Emergency Medicine Journal. ical&varespiration. Accessed December 16, 2007. 2007;24(9):614–617. 2. Ganong WF. Review of Medical Physiology (21st ed.). New York: 13. Creteur J. Gastric and sublingual capnometry. Current Opinion in McGraw-Hill; 2003:670. Critical Care. 2006;12(3):272–277. 3. Davidson JAH, Hosie HE. Limitations of pulse oximetry: 14. Lee DC, Fergusen KL. Methemoglobinemia. Available at: http:// respiratory insuffi ciency—a failure of detection. BMJ. www.emedicine.com/emerg/topic313.htm. Accessed January 18, 1993;307(6900):372–373. 2008. 4. Ward KR, Yealy DM. End-tidal carbon dioxide monitoring 15. Masimo product website. Available at: http://www.masimo.com/ in emergency medicine, part 1: basic principles. Academic Rainbow/rb-overview.htm. Accessed January 18, 2008. Emergency Medicine. 1998;5(6):628–636. 16. Hampson NB, Weaver LK. Noninvasive carbon monoxide 5. Garnett AR, Gervin CA, Gervin AS. Capnographic waveforms in measurement by fi rst responders: a suggested management esophageal intubation: effect of carbonated beverages. Annals of algorithm. JEMS. 2006;31(5):S10–12. Emergency Medicine. 1989;18(4):387–390. 17. Cone DC, MacMillin DS, Van Gelder C, et al. Noninvasive 6. Silvestri S, Ralls GA, Krauss B, et al. The effectiveness of fi reground assessment of carboxyhemoglobin levels in out-of-hospital use of continuous end-tidal carbon dioxide fi refi ghters. Prehospital Emergency Care. 2005;9(1):8–13. monitoring on the rate of unrecognized misplaced intubation 18. Dickinson ET, Mechem CC, Thom SR, et al. Noninvasive within a regional emergency medical services system. Annals of carboxyhemoglobin monitoring of fi refi ghters engaged in fi re Emergency Medicine. 2005;45(5):497–503. suppression and overhaul operations. Prehospital Emergency 7. Levine LR, Wayne MA, Miller CC. End tidal carbon dioxide Care. 2008;12(1):96–97. and outcome of out of hospital cardiac arrest. N Engl J Med. 19. Henry CR, Satran D, Lindgren B, et al. Myocardial injury 1997;337(23):1694–1695. and long term mortality following moderate to severe carbon 8. Grmec S, Klemen P. Does the end-tidal carbon dioxide monoxide poisoning. JAMA. 2006;295(4):398–402. concentration have prognostic value during out of hospital 20. Abelow, B. Understanding Acid Base. Baltimore, Williams & cardiac arrest? European Journal of Emergency Medicine. Wilkins; 1998. 2001;8(4):263–269. 21. Acid Base Physiology. Bedside rules for assessment of 9. Hatlestad D. Capnography as a predictor of the return of compensation. Available at: http://www.anaesthesiamcq.com/ spontaneous circulation. Emergency Medical Services. AcidBaseBook/ab9_3.php. Accessed January 16, 2008. 2004;33(8):75–80. 22. Rang LCF, Murray HE, Wells GA, MacGougan CK. Can 10. Kraus B. Capnography in EMS. Journal of Emergency Medical peripheral venous blood gases replace arterial blood gases in Services. 2003;28(1): 29–41. emergency department patients? CJEM. 2002;4(1): pp. 7–15. 11. Anderson CT, Breen PH. Carbon dioxide kinetics and capnography during critical care. Critical Care. 2000;4(4):207–215. Ventilation 513 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. KEY CONCEPTS: Upon completion of this chapter, it is expected that the reader will understand these following concepts: • The metric system of measurement • Basic drug calculations including weight-dependent drugs and intravenous infusion rates • The six rights of medication administration • Routes for medication administration • Topical anatomy and proper technique for injections Case Study: Mr. Whittendam was a pleasant and proper gentleman with a lengthy cardiac history. He had the new Paramedic enthralled with his recall of previous heart attacks and all of the treatments that he had received in the tiny country hospital many years prior. He said that he had once needed two doses of morphine 1/6gr for severe pain. The senior Paramedic smiled and said he hadn’t thought about grains in a long time. Their current protocols were written in metric measurement. 514 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Principles of Medication Administration 515 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. OVERVIEW The Paramedic has many responsibilities before administering any medication to a patient. These tasks include the six rights of medication administration as well as an ability to carry out calculations using the metric system. This chapter discusses techniques for proper medication administration for the various enteral and parenteral medication routes. Each medication route has pros and cons that will be explored to ensure safety and effectiveness. Medication Administration fl avored with camphor, aniseed, and benzoic acid. Sweeten- ing any tincture makes it into an elixir. The resulting elixir In some instances, it is not so much the medicine adminis- in this case is called paregoric, Greek for something that tered that is crucial but rather the way in which it is given. soothes. Paregoric is very effective against diarrhea, a com- A medicine that is not absorbed into the central circulation, mon malady in developing countries plagued with dysentery where it can be carried to the target organ, is ineffectual. It is and cholera. Paregoric is still listed in the United States Phar- a Paramedic’s responsibility to choose the right drug and the macopoeia as camphorated opium tincture. right dose for the patient, as well as to administer it by the Liquid oral medications commonly face the problem of right route at the right time in order to achieve the optimal tasting badly. The old adage that “a teaspoon of sugar makes therapeutic effect. the medicine go down” shows yet another attempt at making the taking of medicine more pleasant. Medicines mixed with Forms of Medication sugar and water are called syrups. Many cough formulas, some with the opiate codeine, contain sugar water (syrup). The statement “form follows function” holds true for medi- Some medications will not dissolve in a solvent and thus cations. For the untrained layperson, an easy-to-swallow pill remain as fi nely pulverized particles fl oating in the liquid. may appear to be the best carrier for a medication. How- This medication form is called a suspension. It is important ever, for the very old, the very young, and the infi rmed, who that a suspension be shaken before being administered. For- have diffi culty swallowing, a liquid medicine may be better getting to shake the suspension leaves an uneven distribution accepted. of medicine in the solution. Subsequently, the fi rst dose may Numerous forms of medicine have been created over the completely lack the medication if the drug has settled out and centuries. These forms can be grossly categorized into liq- therefore may be impotent, whereas the last dose will be satu- uids, solids, and |
injectable liquids. rated with medication and very potent. Powdered drugs with particles so large that they are vis- Liquid Medication Forms ible when they are mixed, or suspended, in water are called The earliest liquid medications were called spirits. Spirits, magmas. Examples of magmas include milk of magnesia. brewed from various materials, are liquids which have a volatile Oil is also used as an alternative to water as a carrier. Finely oil that evaporates at room temperature and leaves a distinctive pulverized particles placed into oils, such as cod liver oil, are odor in the air. For example, spirit of ammonia has a distinctive called emulsions. The oil in these emulsions also acts as a pungent smell that makes it easily distinguishable from other nutritional supplement; for example, cod liver oil is rich in spirits. An ancient spirit thought to cure a large variety of mala- omega-3 fatty acids as well as vitamins A and D. dies is the “spiritus fermenti.” The modern term for the spiri- Medications meant for the skin (i.e., topical medicine) tus fermenti is whiskey. Alcoholic beverages, including spirits, placed in water are called lotions, whereas those placed in have long been recognized for their medicinal value. either lanolin, an oil from sheep’s wool, or petroleum jelly are Tinctures are medicinal substances that are dissolved called ointments. The choice of oil, water, or chemical base in alcohol. Alcohol has long been used in pharmacy, in part is dependent on whether the medicine is too dry to place on because of its excellent solvent properties and, in part, because the skin or to be absorbed into the skin. of its ready availability. Examples of tinctures include tincture of merthiolate, an early antiseptic, and tincture of benzoin (Friar’s balsam), a combination of balsamic acids whose aromatic vapors Solid Medication Forms are used to relieve nasal congestion and soothe bronchitis. During manufacturing, many medicines can be either Laudanum, a simple tincture of opium, is highly effective extracted chemically or synthesized and then reduced to a dry in relieving a number of maladies including pain and con- powder. The advantage to dry powders is that they are easier stipation. However, its unpleasant aftertaste made it highly to store, they can be stored for a longer period of time without objectionable. To improve its palatability, laudanum was gross deterioration, and they are generally easier to handle. 516 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Use of dried medicine makes sense as most medicines to injected drug levels, without the annoyance of a needle. are reconstituted in the water within the body, and water is a Troches come in more than a dozen fl avors, including blue- universal solvent. When the patient swallows the powder, the berry, butterscotch, caramel, chocolate, peanut butter, and body’s water dissolves the medicine. It is then absorbed into watermelon, and are conveniently packaged in a molded plas- the digestive tract and passes through the portal circulation. tic container which can be carried in a pocket or purse. Some dry medicines still come in a loose powder, usually Other forms of medication that are typically given inter- placed in a waterproof envelope made of wax paper. Goody’s nally for a local effect are suppositories. Suppositories con- headache powder® is an example of a loose powder medi- tain the medicine within a wax carrier which melts at body cation. However, most powdered medications are processed temperature. There are vaginal suppositories, used for yeast into a convenient shape for easy swallowing. A dry medicinal infections, urethral suppositories, and rectal suppositories. powder that is compressed into a pill shape is called a tab- Some rectal suppositories contain chemicals that irritate the let. Tablets are often scored, adding a depression across the bowel lining, triggering defecation and elimination of feces. middle that makes dividing the tablet in half easier. Some Rectal suppositories can also carry medications meant tablets also have a number or letter code embossed across the for systemic effect. The hemorrhoidal venous network in the tablet’s face for easy identifi cation. rectum readily absorbs medications, at levels comparable to Medicinal powder placed within a gelatin casing is called venous injection, into the central circulation.4-6 Use of rectally a capsule. Capsules are generally easier to swallow and, per- inserted diazepam, available in a gel, is an acceptable means haps more importantly, do not dissolve in the water-based of administering this life-saving medication during status saliva of the mouth very easily. epilepticus when ordinary venous access is unobtainable. Some medicines are altered by the acids in the stomach, making them impotent, whereas some medicines, specifi cally those that are acid-based, can irritate the stomach lining, lead- Injected Medications ing to ulcerations. To protect the medicine and/or the stom- Injectable medications come in either ampoules, generally ach, pharmacists have covered tablets in a protective enteric reserved for single patient use, or vials, intended for multiple coating. Enteric coating permits the tablet to travel, unaltered, patients. Glass ampoules were originally used to store a med- through the stomach and into the intestine for absorption. ication that was volatile and would easily evaporate. A beer The elderly, the infant, and the infi rmed often have dif- bottle might be an example of an ampoule to carry a spirit. fi culty swallowing tablets and capsules. In some cases, it In some instances, the medicine was very valuable, or very is acceptable to crush the tablet, with a mortar and pestle, dangerous, and an ampoule was used to preserve the security or open the capsule and place the medicine in another car- of the medication. To obtain the medicine from the ampoule rier, such as apple sauce. However, not all medicines can in those cases, one had to break the neck of the ampoule, be administered in this way. A clear example would be any making pilferage obvious. Morphine was originally stored in enteric-coated tablet. It is important to refer to the manufac- a tear-shaped cobalt-blue ampoule, in part for this reason. turer’s recommendations and the information available from In a sense, vials are resealable ampoules. Typically, the a pharmacist before altering the form of the medicine. glass container, and now a plastic bottle, has a rubber stopper In some instances, it is desirable to have the medicine which can be breached with a needle and syringe, or a needle- dissolve in the mouth. Such medicines exert a local or topical less system, and a volume of medicine withdrawn. A concern effect (e.g., they may be used to treat sore throats). Medi- with vials is sterility. Whenever the integrity of a container cines intended to dissolve in the mouth are called lozenges. has been breached there is a concern about bacterial con- The lozenge, also called troches, owes its origins to the tra- tamination. For this reason, many intravenous medications ditional French anise candy, called pastilles, popular in the are manufactured in single-use ampoules. More discussion eighteenth century. Like elixirs, medicine mixed in a sweet regarding the use of ampoules and vials is contained further medium is more palatable, which makes patient compliance in this chapter. with the prescription more likely. Troches dissolve and are absorbed in the mouth through the oral mucosa. Medication absorbed into the oral mucosa also enters the central circulation, bypassing fi rst pass metabolism within Street Smart the liver.1–3 First pass metabolism is a chemical degrada- tion of the drug by the liver that markedly reduces the drug’s bioavailability. For this reason, it is sometimes advantageous Generally all drugs used in emergencies are to administer a medication orally (i.e., sublingual or in the clear, except diazepam. Diazepam is yellow. Any buccal pocket). An example of a drug administered in this discoloration of any drug should alert the Paramedic fashion would be nitroglycerin. that the drug is potentially contaminated and should Some antibiotics and natural hormone replacements (NHR) are now carried in a troches. This method of medica- be discarded. tion administration results in drug levels that are comparable Principles of Medication Administration 517 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Drug Measurement and Dosing One of the earliest attempts at standardization was the development of the Troy system. These efforts at standardiza- As drugs become more refi ned and newer, more potent com- tion have also led to a great deal of confusion. For example, pounds are developed, the importance of precise measurements a pound apothecary equals 12 ounces, whereas a pound Troy becomes increasingly important. In the past, medicines were equals 16 ounces (avdp). Avdp is the abbreviation for avoir prescribed in teaspoons and grains, and as a result inaccuracies de pois, a French term meaning “goods sold by weight” and is abounded. Today medicines are prescribed in micrograms, a placed after a notation to indicate that it is avoir de pois. unit so small as to be barely visible with the naked eye. A constant in using systems of measurement was busi- The correct measurement of drug quantity can make ness community needs.7,8 For commerce to occur, industry the difference between a therapeutic dose and a toxic dose, needed a common system to count, with accuracy, the goods between better health and iatrogenic death. Needless to say, sold and bartered in trade. Despite its apparent inaccuracies, it is every Paramedic’s responsibility to try and administer the the common household system remains the predominant sys- correct therapeutic dose of drug to the patient. tem of measurement in the United States and Canada. Systems of Measurement Metric System The ancient Egyptians measured length in a cubit, the distance Advances in science demanded a more accurate system of from one’s elbow to the outstretched thumb. As one might measurement, and so the metric system was born out of neces- imagine, this led to a great number of inaccuracies, However, sity. The metric system, from the Greek word metron, trans- precision was not as important then. As time went on three lated to mean “to measure,” was advanced by the Frenchman systems of standardized measurement would be developed; Msr. Gabriel Mouton in 1670. His system of measurement in order, they were the apothecary, the common household, depended on a universal standard from which other measure- and the metric system. Each took generations to accept and ments could be obtained in units of 10. This system of mea- each took generations to unlearn when the newer system was surement made scientifi c measurements easier to calculate. introduced. In each case, the previous system was phased out The French quickly adopted the metric system and called for in favor of the more precise new system. its international adoption. Many countries followed suit, and Le Systeme Internationale d’unites, the international system of units Apothecary System (noted as SI following the number), became widely accepted in In medieval times, apothecaries would dispense medications. both the scientifi c as well as the business community. A com- The root of the word “apothecary” is the Greek “apotheke,” parison of metric standard measurements to household common which means storing place. Apothecaries were storing places measurements shows their differences (Table 26-1). for different substances (some mineral and some animal) and The standard for length measurement adopted was the compounds that would be mixed by the apothecary on the meter. The meter, originally defi ned as one ten millionth of order of a physician. These apothecaries developed a system the distance from the north pole and the equator, was later of measuring small quantities of medication. An apothecary redefi ned to be the distance that light, in a specifi ed spectrum, is somewhat |
analogous to the modern pharmacist. travels over in 1/299,792,458 of a second (light-second) while Apothecary measurements included the grain (gr), which in a perfect vacuum. equaled the weight of one grain of wheat, and the minim, the Interestingly, the SI unit of volume is not the liter but weight of water equal to a grain. Needless to say, the weight of the cubic meter, the amount of water that could be contained a grain of wheat could vary dramatically, infl uenced by such within one cubic meter. However, the liter has become widely factors during the growing season as drought and fl ood. accepted in both the Americas as well as Europe. A cubic However, without a satisfactory alternative, the apothecary system fl ourished for centuries. Notations in the apothecary sys- Table 26-1 Metric Equivalents of Household tem included the use of a Roman numeral representing the quan- Common Measurements tity after the unit of measurement. This arrangement of notation Metric Household still persists in the prescriptions of some physicians who might note ii, meaning two, indicating the number of tablets. This 0.06 mL 1 drop would be preceded by the letters “ap” meaning apothecary. 1 mL 15 drops 5 mL 1 teaspoon 60 gtt Common Household System 15 mL 1 tablespoon 180 gtt The common household system, also referred to as the United 30 mL 2 tablespoons 1 ounce States customary system, contains such units of measurement 180 mL 1 teacup 6 ounces as the foot, the ounce, and the teaspoon. Some measurements 240 mL 1 cup 8 ounces (e.g., the yard, which equals the distance from the king’s nose 500 mL 1 pint 16 ounces to the tip of his outstretched thumb) were widely accepted despite their obvious inadequacies. 1,000 mL 1 quart 32 ounces 518 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. centimeter (cc) of water equals 1 milliliter (mL) of water; Mathematical Conversions therefore, the two are often used interchangeably. Conversions of metric measurements from one unit to another By convention, all abbreviations of SI units are in low- are relatively simple because all units are based on a factor of ercase. For example, 1 meter is abbreviated 1 m. To recog- 10, either 10 times greater or 10 times lesser. For example, a nize that liters are not SI units, the abbreviations for liters kilogram is 1,000 times greater than a gram and a milligram are abbreviated in capital letters. For example, 1 milliliter, a is 1,000 times less than a gram. Therefore, to change a gram thousandth of a liter, would be properly abbreviated 1 mL. to kilograms, the Paramedic only need move the decimal Also by convention, all quantities of the measurement three spaces to the right: 1 gram equals 0.0001 kilogram. are placed in front of the unit of measurement and noted in Conversely, to change a gram to a milligram, the Para- Arabic numerals, not Greek. For example, 10 liters would be medic need only move the decimal three spaces to the left: noted as 10 L and not L 10. Finally, to decrease confusion, 1 gram equals 1,000 milligrams. a space is always placed between the number and the unit, The key in understanding these conversions is to under- indicating that the metric system is being used. stand the prefi xes that precede the unit. All multiplications above 1 gram are noted in the Greek prefi xes kilo-, hector-, and deca-, whereas all divisions of a gram are noted by the Street Smart Latin prefi xes deci-, centi-, milli-, and micro- (Table 26-2). While most Paramedics can access preprinted tables and personal digital assistant (PDA) devices for Street Smart many drug calculations, every Paramedic should be knowledgeable about how to perform these The abbreviation in the laboratory for micro- (for rudimentary calculations in case the battery in the example, in the measurement micrograms) is PDA dies or the drug sheets are lost. the Greek symbol g. However, this notation is impractical in keyboard-based documentation and potentially confused with mg (milligram). Necessarily, Special Units healthcare providers have adopted the abbreviation The dose of some medications has to be determined by bio- logical assay or bioassay, a method of determining the relative mc to indicate micro- (for example, mcg equals strength of a substance by testing it on an organism. To stan- microgram). dardize these bioassay measurements, scientists have created the international unit (IU). Examples of medications that The importance of accurate drug calculations is rein- are measured and administered in international units include forced by the most recent MedMAX data. MedMAX is an insulin and penicillin. anonymous national database of medication errors. Of 40,936 Insulin is frequently self-administered by the patient. To medication errors reported in 2000, 23% were errors in the decrease errors in converting from metric to international quantity of the dose of the medication given. These errors units, and thus improve patient compliance, special insulin could be, in part, due to miscalculation.9–11 syringes are manufactured which are marked in international The more diffi cult calculations are the conversions of units. Confusion can occur when a Paramedic tries to use a household common measurements to the metric system. standard syringe for insulin administration and mistakenly While common conversion factors are available (Table 26-3), thinks that the measurements on the barrel of the syringe are international units when in fact they are minims, an old Table 26-2 Metric Prefi xes apothecary measure. Standard Weight: Gram Measurement Devices Multiply (Greek) Deca- 10 The timeless medicine glass is the quintessential example of a medicine measurement device. Marked with metric units on Hecto- 100 one side and apothecary units on the other, pharmacists and Kilo- 1,000 families alike have used the medicine glass to measure all Divide (Latin) forms of medicine, from cough syrup to antiseptics. Deci- ÷10 Another traditional measurement device is the medicine Centi- ÷100 dropper. The medicine dropper draws up a precise volume into its stem and the medicine is then dispensed, drop by drop, Milli- ÷1,000 into a substance such as juice or water. Micro- ÷1,000,000 Principles of Medication Administration 519 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Table 26-3 Conversion of Measurements the drug’s concentration. For simplicity of calculation, and in in the Common Household order to establish a common denominator, concentrations are and International Metric System described as the amount of drug in 1 milliliter (mL) of a solu- tion. For example, if the drug on hand is 5 mg of diazepam in Unit US Conversion Unit Metric a 2 mL prefi lled syringe, then the concentration of the drug Inch 26.4 Millimeter (mm) Ounce 28.3 Gram (gm) would be 2.5 mg per mL. To make drug calculations easier Pound 0.453 Kilogram (kg) during an emergency, many pharmaceutical companies now Gallon 3.79 Liter (L) provide the concentration in notations on the sides of the drug box and/or on the prefi lled syringe. Metric Conversion Unit US Millimeter 39.6 (1/25.4) Inch (in.) Dilution Gram 0.035 (1/28.3) Ounce (oz) Kilogram 2.25 (1/0.453) Pound (lb) Some medications (e.g., Solumedrol) lose potency when in Liter 0.264 (1/3.79) Gallon (gal) solution for a prolonged period of time. These medications Note: The symbol for a pound lb comes from the Latin libria meaning scales. are necessarily mixed at the patient’s side in order to ensure Note: The term “mile” comes from the Latin mille passus, meaning a thousand maximum effectiveness. A medication being mixed is called paces. the solute and the liquid that the medication is being mixed into is called the solvent. When combined, the solute and sol- vent make a solution. If the mixture is a one-to-one, one part these conversions are not exact and errors of 10% are not solvent to one part solution, then the resulting drug is said to uncommon. be at 100% strength. The conversion of household common to metric standard In some cases, it is desirable to weaken a drug by dilu- measurements in the fi eld is rare. The medical community in tion. For example, 50% dextrose in sterile water (D50) is too the United States has adopted metric measurements as the hypertonic for a child’s blood but may be all that is available standard and all medications come with metric notation. and on hand. The D50 would then be called the stock solu- tion. To decrease its tonicity, D50 can be cut in half, to make Conversion of Weight D25, by adding an equal volume of sterile water. The result- The exception to the rule regarding mathematical conver- ing mixture would be half-strength, yet have a dilution of 1 to sions is the calculation of the patient’s weight. Patients usu- 3—one part dextrose in three parts of solution (Table 26-4). ally know their weight in pounds, not kilograms, forcing the Paramedic to translate pounds into kilograms. Weight in a Volume The most accurate method of converting a patient’s In some instances, it is necessary for a Paramedic to know the weight from pounds to kilograms is dividing the patient’s amount of a drug in a volume of solution. For example, how weight in pounds by 2.26. For example, a 185-pound patient much dextrose is in a 500 mL bag of Dextrose 5% in sterile would weigh approximately 83.71 kilograms. water (D W)? 5 While this is the most accurate method, it is not the most A percent weight/volume is defi ned as 1 gram of sol- convenient. Many Paramedics prefer to divide the patient’s ute dissolved in 100 mL of solvent to obtain a 1% solution. weight, in pounds, in one-half, then subtract 10% off from Therefore, 5 grams of solute is dissolved in 100 mL of sol- the result. For example, half of 185 pounds would be roughly vent to make a 5% solution. If the total volume of the solution 92 / 0.5, then subtract 9 from 92 for an approximate is 500 mL, and there are 5 grams per 100 mL, then there are weight of 83 kilograms. Such gross estimates of a patient’s 25 grams in 500 mL of D W. 5 weight while in the fi eld are acceptable, provided the esti- mated weight is within 10% of the actual weight. Table 26-4 Drug Dilutions Street Smart C1V1 c2v2 Concentration of stock (C1) 50% The Paramedic should use the more accurate Volume of stock (V1) 50 mL Concentration desired (c2) 25% method of determining weight in any child under the Volume of new solution (v2) x mL age of 8. (50)*(50) (25)*(x) (2,500) (25x) x 2,500/25 v2 = x 100 mL Concentration Therefore, to obtain D25, add 50 mL of sterile water to 50 mL of stock A common fi rst step in any drug calculation is determining solution to obtain a volume of 100 mL of D25. the amount of drug on hand. This is typically referred to as 520 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Elements of a Drug Order Physician orders 20 mg furosemide IV bolus. In the drug box is 40 mg A standard drug order, whether written in a standing order or of furosemide |
(i.e., a concentration of 10 mg per mL). given verbally to the Paramedic, will contain the following 10 mg 20 mg elements: the amount of the drug, the name of the drug, and 1 mL x mL the route that is to be administered. (10) (x) (20) (1) It is important that the Paramedic listen carefully to, 10x 20 and note (preferably on paper), the specifi cations within the 20 drug order. The order has essential information regarding the x 10 necessary calculations which must be performed in order to x 2 mL administer the correct dose to the patient. For example, if the physician gives an order of x mg of Figure 26-1 Proportional method of drug a drug to be given in y number of mg per unit weight over calculation. z minutes, then the Paramedic must calculate the amount on hand, the patient’s weight, and the fl ow rate of this infusion to obtain the correct dose of drug. (i.e., injection, tablet, etc.) is a function of the medication. As related earlier, a drug’s concentration must be known The issue for the Paramedic is determining if there is suf- before it can be administered in almost every case. Therefore, it fi cient drug on hand to administer to the patient. One simple is common practice for Paramedics to obtain this value imme- method, referred to as the proportional/ratio method, exists diately, either by consulting the drug packaging or by calculat- for calculating this value. On one side of the equation the ing the concentration mentally and making a notation. Paramedic lists the order (i.e., what is desired; for example, Similarly, many drugs are weight-dependent, especially 10 mg given intravenously). On the other side of the equa- pediatric medications. Therefore, it is common practice for tion the Paramedic lists what is on hand. The problem the the Paramedic to immediately obtain, either directly from the Paramedic is solving is the x (i.e., the volume that needs to be patient or by estimation, the patient’s weight and then convert given). Through a process of cross-multiplication, the value that weight from pounds into kilograms. is obtained (Figure 26-1). Once those basic values have been obtained, the Para- medic can then review the order at hand. If the order contains Weight-Dependent Drug Order the term “per kilogram” then the patient’s weight must be Calculation of weight-dependent drug doses is simple if the included in the calculation. Paramedic follows the order of calculation in a disciplined, If the term “per minute” is included in the order, then the step-wise fashion. Whenever an order is received for a drug drug must be a solution that is to be infused intravenously and to be given (so many milligrams per kilogram), then the Para- the drip factor of the intravenous administration set must be medic must calculate the patient’s weight fi rst, using one of included in the calculation. By convention, all drug infusions the two methods previously described. Having obtained the are administered via a micro-drip administration set. All patient’s weight in kilograms, the Paramedic proceeds to the micro-drip administration sets, regardless of manufacturer, next step, multiplying the patient’s weight times the dose produce 1 mL per every 60 drops of solution. ordered. The result is the amount of drug that must be admin- istered. The fi nal step for the Paramedic would be to compare the amount of drug on hand to the dose ordered to ensure that Street Smart a suffi cient quantity is available. Then, the Paramedic pro- ceeds to administer that dose. Medications can have two names: proprietary and generic. If this was not confusing enough, some generic names sound alike as well. To decrease Street Smart confusion, and a possible medication error, the Paramedic should always confi rm orders after Since many of the drugs a Paramedic uses are receiving them, using a communications technique administered during an emergency, prefi lled ampoules referred to as echo technique. If the drug name is in are standardized to contain the dose that an average doubt, ask the physician to spell it out. 70-kg patient would need. Therefore, if after a drug calculation the result appears to require 10 ampoules, Standard Drug Order then the calculations should be rechecked. Typically, A standard drug order would mean x amount of drug is a misplaced decimal explains the error. to be given to the patient. The manner in which it is given Principles of Medication Administration 521 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Example for a child who is 52 inches Table 26-5 Calculation of a Continuous tall and weighs 90 pounds Infusion Height For children of BSA Weight Order 126 mL per hour cm in normal height M2 in lb kg Administration set drip factor 60 gtts/mL for weight 180 90 80 1.30 Step 1: x gtts/min 126 mL 60 gtts/mL/60 minutes 160 80 1.20 70 2.0 140 Step 2: x gtts/min 7,500/60 240 70 1.10 60 90 1.8 120 220 1.00 50 Step 3: x 126 gtts/min 85 60 1.6 100 200 80 .90 1.5 75 50 1.4 90 40 * By convention, all microdrop administration sets provide 1 mL for every 190 60 drops. 180 70 .80 1.3 80 40 *1.2 70 170 65 .70 1.1 30 160 60 60 1.0 25 150 30 .60 55 0.9 50 Table 26-6 Drip Factors and Ratios 140 .55 45 20 130 0.8 40 for Common Administration Sets 50 .50 20 0.7 35 120 .45 15 45 30 Drip Factor Ratio 110 .40 0.6 25 Micro-drip 60 drops equals 1 mL 1:1 Macro-drip 10 drops equals 1 mL 6:1 Figure 26-2 Pediatric nomogram. 15 drops equals 1 mL 4:1 20 drops equals 1 mL 3:1 Pediatric Dosing patient. Some Paramedics use the abbreviation TKO, meaning The vast majority of pediatric medications are adjusted for the to keep open, to indicate this minimal infusion. child’s weight. In many cases, the order is given as a weight- In certain circumstances, the patient’s condition requires dependent dose. When an adult dose must be adjusted to a an infusion of a specifi c volume. If the volume is infused pediatric dose, and the pediatric dosing is not available, then rapidly over several seconds or minutes, then the infusion is the child’s total body surface area (BSA) is divided against called a bolus. If the volume is to be evenly administered the adult’s total body surface area (approximately 1.73 meters over the course of an hour, then the infusion is called a con- squared for a six-foot tall, 150-pound adult). The resulting tinuous infusion. percentage is then taken from the adult dose and is roughly equal to the pediatric dose. Continuous Infusion Calculation of a child’s BSA is easy when a pediatric nomogram is used. The Paramedic would obtain the child’s The task facing the Paramedic, once the order for a continu- height and weight, then cross-reference on the nomogram to ous infusion is given, is to determine how many drips per the child’s BSA (Figure 26-2). minute must occur. There are two methods of determining the drip rate for a continuous infusion. Intravenous Infusions The formula method enlists all of the necessary informa- tion into the calculation and the result is a defi ned drip rate. Continuous infusion of intravenous fl uids is frequently To obtain this number, the Paramedic multiples the drip fac- required in the out-of-hospital care of an ill or injured patient. tor of the tubing (every tubing has a drip factor; for example, When the patient’s condition requires that a large fl uid bolus so many drops equals 1 mL), then divides the total by the be infused (e.g., in order to increase a blood pressure for number of minutes that the infusion is to last (Table 26-5). perfusion), then the intravenous fl uid is usually infused rap- The other method is the ratio/factor method. Understand- idly, or wide open (WO). The number of liters of volume- ing that there are 60 minutes in one hour and that a micro- expanding fl uid—traditionally lactated Ringer’s solution drip administration set provides 1 mL for every 60 drops of (LR) or normal saline solution (NSS)—infused should be fl uid, then a 1:1 relationship has been established between adequate to ensure a minimally acceptable blood pressure in minutes to drops and time to volume. It is apparent that, the range of 80 to 90 mmHg systolic is maintained. because of the 1:1 relationship, the number of milliliters per At other times, the aggressive fl uid resuscitation just hour is always going to be equal to the number of drops per described would be inappropriate. However, constant venous minute (Table 26-6). This 1:1 relationship is only true in the access (e.g., for purposes of medication administration) would case where a micro-drip administration set is used. However, be desirable. Without any fl uids infusing, the IV catheter could by understanding this 1:1 relationship, similar ratios can be become occluded by a blood clot. To prevent occlusion, a mini- established for other intravenous administration sets. mal infusion of solution is continued, typically at an infusion For example, if the drip factor of a macro-drip administra- rate equaling 30 mL per hour. The primary purpose of this slow tion set is 15 drops equals 1 milliliter, or one-fourth less drops infusion is to keep the vein open (KVO) in the IV catheter than a micro-drip administration set, then a 4:1 ratio has been 522 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. established between this macro-drip administration set infusion of drug on-hand (1 gram or 200 mg), if a 4:1 mixture can be rate and a standard micro-drip administration set infusion rate. made (i.e., 250 mL or 50 mL), then the clock method can be To use an example, if the order is for 200 mL per hour, used (Table 26-8). then the drip rate with a micro-drip administration set would be 200 gtts per min. However, if a 15 drop macro-drip admin- Weight-Dependent Intravenous istration set was used, then the order, 200 mL/hr, would be Drug Infusion divided by a factor of 4. The resulting drip rate would be Some drugs are so potent that it is important to precisely infuse 50 drops per minute. (i.e., titrate) the drug to the patient’s weight. As complicated Intravenous Drug Infusion as the process sounds, a weight-dependent intravenous drug infusion only adds the patient’s weight to the standard drug Intravenous drug infusions require precise control (i.e., titra- infusion calculations (Table 26-9). tion) of the drug in order to provide the intended effect. Errors, plus or minus the ordered drug infusion, can result in undesirable effects. Before an order for an intravenous drug Table 26-8 Calculation of Intravenous Drug infusion can begin to be administered, the Paramedic must Infusion Rate Using the Clock Method fi rst prepare the solution, or access a premixed solution, then Order 3 mg per minute (3 mg/min) determine the number of drops per minute to be infused. Administration set 60 drops per mL There are two methods of determining the drop rate. The Solution on-hand 250 mL physiologic saline fi rst method, the formula method, requires the Paramedic to mul- Drug on-hand 1 gram tiply the dose in the order given times the drip factor, then times the solution in order to obtain the desired drip rate (Table 26-7). Drip rate X Alternatively, Paramedics can use the clock method to Step |
1: Calculate the concentration determine the infusion rate. By observing a few fundamen- 1 gram in 250 mL 2 milligrams per 1 milliliter tal conditions, the clock method of drug infusion permits the 1,000 gram/250 mL 2 mg/mL Paramedic to mentally visualize a clock with a sweep hand (Conversion to common units makes calculations easier) pointing out the drug infusion rate. When the sweep hand is Step 2: Step up the clock at the 15 second point, that represents 1 milligram of drug at 1 mg 15 drops per min 30 mL/hour 15 drops per minute or 15 milliliters an hour. When the sweep 2 mg 30 gtt/min 30 mL/hr hand is at the 30 second position, it represents 2 milligrams 3 mg 45 gtt/min 45 mL/hr of the drug infusing at 30 drops per minute, and so forth. Foundational to the clock method is the condition that 4 mg 60 gtt/min 60 mL/hr the drug’s concentration is 4 to 1. Regardless of the amount Table 26-9 Weight Dependent Drug Infusion Table 26-7 Calculation of Intravenous Drug Order 5 microgram per kilogram per minute Infusion Rate Using a Formula (5 mcg/kg/min) Order 3 mg per minute (3 mg/min) Administration set 60 drops per mL Administration set 60 drops per mL Solution on-hand 500 mL physiologic saline Solution on-hand 500 mL physiologic saline Drug on-hand 1 gram Drug on hand 1 gram Drip rate X Drip rate X Patient weight 70 kg Formula Order Solution Administration set Formula Order Solution Patient’s weight (kilograms) Drip rate of administration set ÷ Concentration of the drug Step 1: Calculate the concentration 1 gram in 500 mL 2 milligrams per 1 milliliter Step One: Calculate the concentration 1,000 gram/500 mL 2 mg/mL 1 gram in 500 mL 2 milligrams per 1 milliliter (Conversion to common units makes calculations easier) 1,000 gram/500 mL 2 mg/mL 2,000 mcg/mL Step 2: Set up the formula Step Two: Set up the formula Order Drip factor/Drug concentration Order Drip factor Patient weight ÷ Drug concentration 3 mg/min 60 gtt/mL/2 mg/mL X 5 mcg/kg/min 60 gtt/mL 70 kg/2,000 mcg/mL X Step 3: Eliminate like units Step Three: Eliminate like units 3 min 60 gtt/2 X 5 60 gtt 70 min/2,000 X 180 gtt/min/2 X 25,000 gtt/min/2,000 X 90 gtt/min X 10.5 gtt/min X Principles of Medication Administration 523 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. The Paramedic’s failure to convert a patient’s weight Similarly, the Fahrenheit scale does not have water freezing from pounds (household common) to kilograms (metric) is at zero degrees but at 32 degrees. Therefore, to balance the a source of error in some calculations. It is essential that all two scales 32 must be either added or subtracted from the Paramedics convert all units to a common system before per- result. To convert Fahrenheit to Celsius (medical standard forming drug calculations. temperature measurement) the EMS provider must fi rst sub- tract 32 from the number and then multiply the Fahrenheit Temperature Measurement temperature by 5/9. For example, for a temperature of 103°F, subtract 32 and multiply the result by 5/9 to get the tem- A patient’s body temperature has come to be regarded as a perature on the Celsius scale—(103 32) 5/9 (71)5/9 key indicator of a patient’s health or illness (i.e., a vital sign). 39.4°C. The opposite would be true to convert Celsius to A fever greater than 101°F, might indicate the presence of an Fahrenheit. infectious process inside a patient’s body or that the patient’s body has undergone a signifi cant heat stress. A fever greater than 100.4°F but less than 101°F, may indicate an infl amma- Administration of Medication tory response. Regardless of the source of a patient’s elevated The administration of medications may be one of the great- (or depressed) temperature, the body can only tolerate a very est responsibilities that a Paramedic has to perform. Because narrow range of temperature change from its baseline and still of the nature of a medical emergency, Paramedics are per- function. Core temperatures above or below this range can mitted to administer powerful and potentially lethal drugs. lead to cessation of essential metabolic processes and chemi- When given correctly, these medications can help to improve cal reactions critical to all organ function. Understanding the a patient’s condition or relieve some suffering. Given incor- importance of body temperature as a vital sign, Paramedics rectly, the Paramedic may make a bad situation worse. There- often obtain a temperature using a red-dyed alcohol thermom- fore, Paramedics are ever mindful of their responsibilities eter or, more recently, a tympanic membrane thermometer. whenever drugs are being administered. Like nurses, Para- While Galileo Galilei invented the water thermometer in medics practice the fi ve rights of medication administration 1593, then called a thermoscope, the invention of the fi rst (right person, medication, dose, route, and time). The fi ve accurate and functional mercury thermometer was attributed rights simply represent an intelligence, a way of thinking, that to a meteorologist named Daniel Gabriel Fahrenheit in 1714. decreases the potential for medication errors. Using a water and salt solution as a standard, he established The fi rst right refers to the right patient. Although this is a freezing point for the solution, at 0°F, then established the an infrequent request, the Paramedic may be asked to assist in freezing of water alone (30°F) and temperature of the human giving medications to patients with whom he is not familiar, body (90°F). These values (later adjusted to 32°F and 98.6°F, such as during a mass casualty incident, while practicing in an respectively), when obtained by thermometer, established expanded role, or while acting within an emergency depart- a rapid and objective means of assessing a person’s body ment as part of the staff. In those instances, the Paramedic temperature. would be expected to identify the patient. If the patient is Shortly after establishing the Fahrenheit scale, Anders awake, alert, and able to communicate, then a personal iden- Celsius, a Swedish astronomer, replaced the previously used tifi cation may be attempted. If the patient is part of a system salt solution with pure water and again froze and then boiled where personal identifi cation, usually in the form of an iden- the pure water at sea level (standard atmospheric pressure). tifi cation band, is provided, then the Paramedic may check Using these measurements as a baseline, he evenly divided the band to verify the patient’s identity as well as identify the the difference into 100 increments, or a centigrade scale, with patient personally. zero being frozen water and 100 being boiling water. This The remaining rights refer to the actual administration of centigrade scale, also called the Celsius scale, was adopted the medication. At the beginning, the Paramedic will check by an international conference on weights and measures, held to be sure that the right medication is being given. Generic in 1948, as the offi cial temperature scale. medications can have names that either sound alike or are Analogous to the duality of household common and met- spelled similarly. Careful attention to detail, such as the spell- ric measurement systems, the public (particularly in English- ing in the order and the spelling on the medicine container, speaking countries) adopted the Fahrenheit scale whereas the will prevent a medication error. scientifi c community adopted the Celsius scale. It is good practice to verify a medication’s name when it While many thermometers produced have both Celsius is obtained from stock (whether that is a drug box or medi- and Fahrenheit scales imprinted on the glass cylinder, in some cine cart), when it is being measured, and then fi nally when instances a Paramedic may be asked to convert Fahrenheit to it is being administered. This triple check of the medication’s Celsius or vice versa. The most apparent difference between identity is expanded to include verifi cation of the drug’s expi- these two scales is that one is based upon 180 even divisions ration as well as the clarity of the medication in the container. between freezing and boiling, whereas the other is based upon If there is any suspicion of potential contamination, then the 100 even divisions. Therefore, any conversions will necessar- drug should be immediately and safely discarded and a new ily involve a 9/5 or a 5/9 adjustment to make the scales equal. supply of the drug obtained from stock. 524 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. As a drug is being prepared for administration, the Para- The fi nal right, the right time, speaks to the adminis- medic should be attentive to the next right, the right dose. tration of drugs on a repetitive schedule. At fi rst blush, this While measuring a dose of medicine, the Paramedic may be might seem inapplicable to EMS. However, some drugs are at greatest risk of committing an error. given repeatedly in the fi eld in order to obtain and main- As previously mentioned, most emergency drugs are pre- tain a certain therapeutic effect. For example, epinephrine pared so that one prefi lled ampoule will be the correct dose is usually repeated every three to fi ve minutes during a car- for the average 70-kg patient. Unfortunately, patients do not diac arrest until there is a return of spontaneous circulation always weigh 70 kg, so adjustments must be made. Further- (ROSC).12–14 In other situations, medications need to be given more, almost all pediatric medications, a large number of in a specifi c order (i.e., at the right time). For example, during medications for the elderly, and an ever-increasing number of a cardiac arrest, vasopressin or epinephrine always precedes adult medications require weight specifi c dosing. an antidysrhythmic and paralytic drugs follow pre-induction Calculating a weight-dependent dose, described earlier medications. in this chapter, is often diffi cult in the out-of-hospital setting. After being given a drug, the patient is re-evaluated to see Poor lighting as well as patient urgency can lead to unin- if the drug was effective. No exceptions should be made. Even tended errors. The creation of drug charts and use of personal the benefi t of a seemingly innocent drug such as oxygen must digital assistants (PDA) have helped alleviate some of the dif- be followed up with a re-evaluation of the patient’s condition. fi culty of calculating the correct dose. Nevertheless, respon- This re-evaluation, and subsequent documentation of patient sible Paramedics typically confi rm—and then re-confi rm—a response to medication, is so important that some Paramedics drug calculation with another Paramedic. If another provider refer to it as the sixth right, the right documentation. is not immediately available, then communication with the The initials DARE, a simple mnemonic, can help Para- hospital emergency department is advocated. A colleague, medics remember the elements of documentation for every such as a registered nurse or physician’s assistant, seated in medication administration. First, what was the data (D) that a well-lit room with abundant resources at hand (including a was obtained and what action (A) was taken in response to calculator) can offer reassurance to a Paramedic who is alone that data? The documentation of the action, if it was a medi- calculating a critical medication dose. cation administration, should include the drug’s name, the exact dose |
of the drug, and the administration route, as well as the time of administration. After an appropriate interval, usually determined by the drug’s onset of action and peak Street Smart effect, the patient’s response (R) to the drugs is assessed, both subjective and objective information obtained, and an evalu- ation (E) of the effi ciency made. In some instances, the drug To decrease confusion and errors, medication orders may be effective and further treatment is not indicated, while of fractions of a whole are documented as 0.X instead in other cases the drug has to be repeated. of .X (e.g., 0.5 instead of .5). When given orally, they are said as “zero point X.” By adhering to this practice, Medication Routes when an order for a one-half milligram dose of a drug Practical necessity generally determines the route that a med- is heard, it will not be mistaken for 5 milligrams of ication is given. If time is of the essence and it is important the drug. Similarly, whole numbers are listed as the to get a precise dose to a target organ, without risk of fi rst digit (i.e., 1 is 1, not 1.0) and thereby prevent the pass metabolism, then the intravenous route is preferred. If a local effect (e.g., skin preparation for a large bore intravenous accidental administration of 10 mg of a drug. needle) is needed, then a topically applied cream or subcuta- neous injection would be appropriate. Each medication route offers specifi c advantages as well as disadvantages over other The next right, the right route, may seem at fi rst blush to medication routes. Therefore, the route of medication admin- be obvious, as Paramedics usually administer drugs intrave- istration is chosen with an express advantage or specifi c pur- nously. Even when a drug is given intravenously, however, if pose in mind. the drug is not followed by a bolus to clear it from the intra- venous administration set, or external chest compressions are Preparation for Medication not performed to circulate the drug, then the drug will not get to the target organ. In other instances, medications adminis- Administration tered subcutaneously to a hypoperfused patient will not be Regardless of the route of medication administration, whether absorbed and the patient will not benefi t from the medication. it is a local route or a systemic route, the Paramedic must pre- The Paramedic should give heed to the warning (right route) pare both the patient and himself. The patient has the right and consider the method of which he is about to administer a to know what is being done and what medications are being medication in terms of its effi ciency and effectiveness. given. A review of the discussion on informed consent is Principles of Medication Administration 525 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. advised if the Paramedic is unsure of whether—and under Otic Medication what conditions—a patient can give informed consent. Medications applied into the ear are called otic medications. The process of obtaining an informed consent from a While it is rare for a Paramedic to instill medications into a competent patient can be summarized by the mnemonic AIR. patient’s ear, if the occasion should arise the patient should First, the Paramedic must ask the patient if he has any allergies be instructed to tilt the head so that the affected ear is facing (A), particularly to the medication that is to be given. Then the upward. After the correct volume of medicine has been drawn patient should be advised of the intended (I) effect of the medi- into the medicine dropper, the Paramedic would approach the cation. Finally, the patient must be advised of reasonable (R) patient. With the ear canal exposed and no visible drainage or risks associated with the procedure and the medication. After obstruction noted, the Paramedic would place the dorsum of obtaining the patient’s consent, the Paramedic should practice the dominant hand on the patient’s temple with the ear dropper medical asepsis, including hand washing and donning gloves. fi rmly held in the hand and poised over the ear opening. This position prevents the ear dropper from being inadvertently dropped into the patient’s ear if the patient should startle and Street Smart jerk. Grasping the pinna of the ear with the nondominant hand and pulling upward and outward, the medicine can be safely instilled into the ear. If the patient is incapable of cooperat- When asking about allergies, the Paramedic should ing with care, then consider placing the patient in the lateral specifi cally ask the patient about allergies to latex, recumbent position. If drainage is desired afterward, simply since a signifi cant number of patients with chronic have the patient roll over to the opposite side. medical illnesses or healthcare workers have Local Nasal Medication developed an allergy to latex. The Paramedic may The inner mucosa of the nostrils has a rich capillary bed that fi nd it diffi cult to differentiate whether the patient’s is an excellent route for the administration of systemic medi- allergic symptoms were from the medication itself cations, discussed later in this chapter. However, this same or the latex within products used to administer that quality also makes the nose prone to bleeding (a nosebleed is medication. If the patient advises the Paramedic called an epistaxis). Epistaxis is an all-too-common event whenever a nasal pha- that he is latex-sensitive/allergic, then non-latex ryngeal airway or an endotracheal tube is introduced into the products must be used during care. Manufacturers are nostril. Subsequent bleeding can drain back into the hypophar- increasingly removing latex from their products for ynx and into the stomach, inducing nausea and possible regurgi- tation. To decrease the incidence of epistaxis, many Paramedics this reason. prepare the nostril with a topically applied vasoconstrictor, such as phenylephrine (Neosynephrine®). Placing the tip of an atom- izer into the intended nostril, the atomizer bulb is given one or Local Routes two squeezes, propelling the medicine against the mucosa. Local routes of medication administration are intended to tar- Following this application of a local vasoconstrictor, some get a specifi c organ or function and confi ne the effects of the Paramedics lubricate the patient’s nares with a topical anes- medication used to that area. For example, medications topi- thetic, such as lidocaine gel. Using a nasal pharyngeal airway cally applied to the eyes are called optic medications. Para- as an introducer, the Paramedic would liberally coat the airway medics occasionally apply a local anesthetic (e.g., pilocaine) and then insert the airway as usual. It is important that the to the eyeball to anesthetize it in preparation for irrigation. Paramedic ascertain if the patient has any allergies to these The eye is an important sense organ and administration errors medications before use. Alternatively, a water-based gel can can lead to blindness. Strict adherence to medical asepsis can be used to lubricate the nare. Under no conditions should a decrease the potential for this complication. petroleum-based gel, such as Vaseline®, be used to lubricate When a medication is an ointment or gel, then a ribbon the nostril prior to introduction of the airway device. of the medicine is placed along the inside of the lower lid. To Phenylephrine and epinephrine (1:10,000) are also used gain access to the inside of the lower lid, the Paramedic should in the treatment of severe epistaxis prior to packing. Approxi- fi rst withdraw the eyelid from the eyeball and then roll the eye- mately 90% of nosebleeds are anterior nosebleeds. Topical lid over a cotton swab, inverting the eyelid in the process. The application of these potent vasoconstrictors provides local ribbon of medication should then be applied from the inner vasoconstriction that helps to decrease bleeding. canthus, proximal to the bridge of the nose, outward. To avoid the risk of cross-contamination and infection, Local Oral Medications optic drops, ointments, and disks are single-patient use only. Like the nose, the mouth has a capillary-rich mucosa that After use, the medication should be immediately discarded to will rapidly absorb any medicine and distribute it systemi- avoid any opportunity for re-use. cally. Systemic medications are typically placed in the buccal 526 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. pocket of the cheek or underneath the tongue in the sublingual rapidly absorb medications. It drains into the lingual vein and space. This route of medication administration is discussed in then into the systemic circulation, sometimes at levels com- further detail later in the chapter. However, the implication parable to intravenous injection. is clear. Large doses of topical oral medication can have a A distinctive advantage of sublingual medication admin- systemic effect and the patient should always be monitored istration is that it bypasses the liver and thus avoids hepatic carefully for untoward effects. fi rst pass metabolism.15 Some medications are extremely sen- Various forms of topical oral medications are available. sitive to this fi rst pass metabolism; for example, a healthy Gargles, such as a salt-water gargle, can be used to cleanse the liver inactivates approximately 90% of oral nitroglycerine.16 mouth of contaminations, such as a blood splash, as well as dilute Furthermore, variations in blood fl ow, including hypotension- any potential pathogens. Hard lozenges and troches are designed induced shock-liver, as well as variations in hepatic enzyme to dissolve in the mouth, extending the duration of contact that activity, secondary to competition, make the drug’s metabo- the medicine has with the mucosa, perhaps to sooth ulceration. lism in the liver unpredictable. Sublingual medication can be given as either a liquid or a Topical Medications solid (pill). The Paramedic starts by lifting the tongue (assis- While a variety of options are used to apply medicine to the tance with a tongue blade is helpful) and depositing the medi- skin, such as liniments and lotions, and for a wide variety of cine into the sublingual space. If the medication is a tablet or purposes, from muscle aches to sunburn, Paramedics typi- pill, it must dissolve to be effective. If the patient lacks saliva, cally do not apply many topical medications. The exception a squirt from a pearl of sterile water can provide the needed may be the application of a topical antibiotic at the inser- solvent to accomplish liquefaction of the medication. tion site of an intravenous catheter. The benefi ts of topically Patients who have received sublingual medication should applied antibiotic ointment are discussed in Chapter 27. be discouraged from smoking immediately afterward. Nico- tine present in the smoke will produce vasoconstriction, hin- Other Local Routes dering the absorption of the medication. For completeness, both douches and enemas should be men- tioned. Paramedics rarely perform either of these procedures Buccal Route unless they are acting in an extended role. Both douches Administering medications using the buccal route is similar (solutions introduced into the vagina via an apparatus) and to administering medications sublingually. In cases in which enemas (solutions similarly introduced into the anus via an the patient has diffi culty with lifting the tongue to the roof of apparatus) instill these solutions into those body cavities. the mouth (e.g., following a stroke), then the medication can Adding a medication to these solutions can provide a local be placed in the buccal pocket created by the cheek. Plac- therapeutic effect, such as when treating a yeast infection. ing drugs in the buccal pocket has been a common practice since antiquity. Peruvian Indians used to stuff chewed coca Routes for Systemic Medications leaves into their buccal pockets, thus absorbing the stimulant directly into the bloodstream. |
Tobacco has also been placed in Medications can have a local effect or they can have a sys- the buccal pocket, as tobacco chew, and the nicotine absorbed temic effect (i.e., an impact on more than one internal organ into the central circulation. system). Medications that are intended to have a systemic effect may be given via the gastrointestinal tract or via an Oral Route injection. The fi rst route, also referred to as the enteral route, is more common and includes taking oral medications, in Clearly, the vast majority of medications that are self- the form of pills, as well as suppositories. The second route a dministered are swallowed. The medication—solid pill, bypasses the gastrointestinal system and is called the paren- capsule, or liquid—is then absorbed into the gastrointestinal teral route. The parenteral route is preferred during an emer- tract where it is passed, via the portal circulation, through the gency because of the rapidity of onset of the medication’s liver and on into the central circulation. The image of a nurse action as well as predictability of the drug levels. passing pills in a paper medicine cup, also called a souffl é The next section reviews the enteral route of drug admin- cup, leaps to mind when one thinks of hospital care. However, istration, from head to toe, followed by a discussion of the Paramedics seldom use this route to administer medicine. parenteral routes of medication administration by inhalation First, the absorption of medications via the gastrointesti- and injection. nal route can be protracted and erratic. Local conditions such as the presence or absence of food, stomach acidity, gastric Enteral Drug Administration motility, and mesenteric blood fl ow all infl uence drug absorp- tion. Perhaps more importantly from an EMS perspective, the Sublingual Route patient must be able to maintain the airway independently and The fi rst enteral route to be discussed is the sublingual route. swallow the medication. Paramedics are often called to the The lingual space is an area inferior to the tongue. The fl oor scene of a patient who is semiconscious, making this route of the sublingual space has abundant capillaries which can impractical. Principles of Medication Administration 527 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Gastric Tubes One means of passing medication to an obtunded or coma- Street Smart tose patient is via a gastric tube. Gastric tubes have been used for decades to administer medications and treatments, and for Gastric tubes can also be passed directly through a variety of other purposes, but have only recently seen use the abdominal wall via a surgical stab wound. A in the fi eld. John Hunter was credited with inventing the fi rst gastric Paramedic may be called to care for the patient tube in 1869, using the skin of an eel to pass liquids into with an indwelling gastrostomy tube which has the stomach of a patient who had diffi culty swallowing (dys- been misdirected or even accidentally removed. phagia). Subsequently, Matas and Meyer used gastric tubes to treat paralytic ileus, a common post-operative complication. The Paramedic should not attempt to replace the The purposes of a gastric tube are numerous. Gastric gastrostomy tube without special training. tubes can be placed to instill feedings (either intermittently or continuously), as well as instill medications (either liquid or solid drug that is pulverized and then mixed in a liquid placement, verifi cation of placement, and either evacuation carrier). One of the earliest gastric tubes, called the Levin of the stomach or instillation of medications. tube, is a simple red rubber catheter that is often placed for A rudimentary understanding of fl uid dynamics is needed this purpose. before the Paramedic selects the appropriate tube. Fluids tend Gastric tubes can also be used to remove air; decompress- to fl ow from areas of higher pressure to areas of lower pres- ing the stomach. Insuffl ation of the stomach during ventilation sure, measurable as milliliters per hour (mL/hr). Naturally, the of the unconscious patient frequently requires the placement thicker the fl uid, the more pressure is needed to cause fl ow. of a gastric tube to decompress the stomach and permit more The viscosity of the fl uid, and the resultant friction, plays a effective ventilation. Decompression of the stomach with an large role in the selection of the proper tube. The speed of the orogastric tube is important for ventilation of children. Over- fl ow is a function of the pressure that is being exerted upon it. infl ation of the stomach in a child decreases diaphragmatic Pressure is measured as the height that a column of water or excursion, increases resistance to ventilation, and decreases mercury would raise under the same pressure and is labeled compliance, culminating in decreased effi ciency in ventila- either cm H O or mmHg. 2 tion of the child. For this reason, it is routine practice to insert The diameter of the inner portion of the tube (the lumen) an orogastric tube during pediatric intubation. also contributes to the friction loss. The smaller the tube, the Gastric tubes can also be used to remove liquid and small greater the friction loss. Therefore, greater pressure will be bits of solid matter from the stomach, such as pill fragments.17 needed to create fl ow. Gastric tube lumens are measured in Evacuation of the stomach using a large diameter tube, such the French scale, where a smaller number means a smaller as an Ewald tube, may be a part of decontamination after a lumen. The length of a gastric tube also contributes to friction potentially lethal ingestion. loss. However, since the lengths tend to vary marginally, the In addition, gastric tubes can be used to compress the contribution of length of the gastric tube is often discounted. inside of the stomach and the esophagus. Bleeding from Most Paramedics insert an orogastric tube in order to esophageal varices or gastric ulcers can be signifi cant and evacuate or decompress the stomach. The application of suc- potentially life-threatening. Use of a special gastric tube, called tion to the end of an orogastric tube can effectively accom- a S engstaken-Blakemore tube, permits the Paramedic to apply plish this function. Suction, a pressure that is less than direct pressure, internally, to the source of bleeding.18,19 atmospheric (a negative pressure), creates a fl ow in a fl uid, A gastric tube may be inserted either orally or nasally. either gas or liquid. Most ambulances and portable suction Nasogastric tubes are typically inserted into patients who are units can provide substantial continuous suction, greater than awake, those with an intact gag refl ex, or those for whom the 180 mmHg. gastric tube is expected to be long-term. However, application However, continuous suction will cause a single-lumen of a local anesthetic (e.g., Hurricane spray®) can deaden the gastric tube, such as a Levin tube, to adhere to the gastric gag refl ex and permit passage of the gastric tube orally in an mucosa, leading to local irritation and bleeding. To prevent awake patient. Alternatively, a gastric tube may also be passed this predictable complication, dual-lumen tubes (such as the orally in the obtunded or unconscious patient. This is the most Salem sump) were invented. Dual-lumen gastric tubes always common route and the preferred route for EMS providers. have one port open, a port that entrains air into the stomach As in all procedures, the Paramedic should fi rst discuss and prevents suction from adhering to the stomach wall. the procedure with the patient, inquiring about allergies, If a dual-lumen tube is not available, then intermittent advising the patient of the intended effect, and warning the suction can be accomplished by periodically turning the suc- patient about reasonably expected side effects. tion off, allowing the gastric tube to dislodge. Healthcare The process of orogastric tube insertion includes facilities frequently have wall-mounted suction devices which selection, preparation, and measurement of the tube; tube permit intermittent suction for this purpose. 528 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Alternatively, an OG tube is directly advanced over the Street Smart midline of the tongue until the posterior pharynx is reached. Care should be taken to not strike the posterior pharynx as it might elicit a gag refl ex. If the blue atmosphere port of a dual-lumen gastric The gastric tube, now in the proximity of the posterior tube is lower than the stomach, stomach contents pharynx, is ready to be passed. If the patient is willing and will drain through the atmosphere port by gravity. As able to cooperate, then ask the patient to sip a glass of water happens on occasion, the Paramedic may unwittingly through a straw. This facilitates the passage of the gastric tube into the esophagus by closing the glottis over the trachea, allow the tube to fall to the patient’s side. thereby preventing accidental tracheal intubation. Subsequently the tube drains the stomach contents If the patient has persistent paroxysms of gagging and onto the Paramedic’s shoes and/or the fl oor. To retching, then visualize the posterior oropharynx with a pen- light. It is not uncommon to fi nd the gastric tube coiled in prevent this complication, the tube should be plugged the posterior pharynx. In that case, withdraw the gastric tube and the tail of the tube pinned to the patient’s until it is unfurled and then proceed once more. clothing near the collar. Once the gastric tube is in the esophagus, approximately one-half the length of the measurement, then the gastric tube should be advanced briskly. If the patient begins to cough, then Initially, preparation for gastric tube insertion entails col- the gastric tube may be in the trachea and pressing against the lecting the necessary equipment fi rst. Either a single-lumen carina. Withdraw the tube approximately 6 inches and retry. gastric tube (such as a red rubber Levin or an Ewald tube), After the gastric tube has been completely passed, then or a dual-lumen gastric tube (such as a Salem sump) should its placement must be confi rmed. The Paramedic would fi rst be chosen. All gastric tubes are approximately 50 inches draw up 10 to 20 mL of air in a slip-tip syringe and place it at (127 cm) long and come in sizes 12 to 18 French. An average the distal opening. The Paramedic would then place a stetho- adult will accept a 16 French gastric tube. scope fi rmly against the epigastrium and instill the air into the If the nasogastric route is to be attempted, a tube of water- tube. If the gastric tube is properly placed, then a swooshing sound will be heard over the epigastrium.20-22 soluble lubricant should be available, as well as towels, emesis basin, soft-tip or covered clamps, a large syringe (30 mL), and The same sound will not be heard over the lungs; therefore, a stethoscope. auscultating the lungs may not be a reliable indicator of misplace- After obtaining the necessary consent, the patient is ment. Instead, the Paramedic should ask the patient to speak. placed in the high-Fowler’s position. If the patient is unable A gastric tube misplaced into the lungs will separate the vocal to be placed in the high-Fowler’s position, then the patient cords and the patient will have diffi culty speaking (dysphonia). can be placed in the left lateral recumbent position. Finally, the Paramedic should aspirate the gastric tube. If a nasogastric tube is to be inserted, then the Paramedic The presence of gastric contents is proof positive that the gas- should fi rst visualize |
the external nare and choose the largest tric tube is in the right place. Other signs of a misplaced tube nostril, avoiding nasal polyps or a deviated septum. Premedi- include condensation in the tube as well as dropping pulse cation with phenylephrine and lidocaine gel, as previously oximetry readings, indicating desaturation of the blood. described for nasopharyngeal airway insertion, will reduce The gastric tube can then be attached to wall suction the trauma associated with this approach. and low suction can be applied, approximately 90 mmHg. Next, the gastric tube must be premeasured. A nasogastric The patient should be continually monitored throughout this (NG) tube is measured from the bridge of the nose to an earlobe, procedure. Signs of hypoxia, such as premature ventricular then from the earlobe to the xiphoid process. An orogastric (OG) contractions (PVC), and altered level of responsiveness may tube is measured from the corner of the lips to the xiphoid pro- indicate that the gastric tube is misplaced into the trachea, or cess instead. Once measured, the Paramedic should make note of has migrated from its original position into the trachea, and the measurement. Most gastric tubes have incremental markings, the suction is drawing air out of the lungs. consisting of black bands placed every so many centimeters. Once placement of the gastric tube has been confi rmed, Once the tube is measured and the patient prepared, the the Paramedic should proceed to secure the gastric tube to pre- Paramedic then lubricates the last 6 inches of the gastric tube vent accidental displacement. An approximately 6-inch piece with a water-soluble gel, and proceeds to pass the tube. An of 1-inch tape placed in a chevron fashion over the nose will NG tube is advanced perpendicular to the plane of the face secure the NG tube. An OG tube can be secured to the corner and directly into the nares. If resistance is felt, then the tube of the mouth with a tie-wrap, similar to an endotracheal tube. should be slightly withdrawn, approximately 1 inch, and then Alternatively, if an endotracheal tube is in place, then the OG rotated in the fi ngers 90 degrees. Then another attempt should tube can be secured to the endotracheal tube itself. be made. A twisting action with the tip of the tube will help On occasion, the fl ow from the gastric tube may stop, sug- the tube pass over the turbinates in the nose. gesting that the gastric tube is not functioning. Under those conditions, the Paramedic should disconnect the suction and Principles of Medication Administration 529 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. reassess placement to eliminate the possibility of displace- ment. If the gastric tube is not displaced, then the Paramedic Street Smart should assess the gastric tube for obstructions. To accomplish this, the Paramedic irrigates the gastric tube. To irrigate a gastric tube, approximately 30 mL of saline or sterile water Continuous seizures in children (pediatric status is instilled into the tube via a syringe. If a great deal of resis- epilepticus) can be life-threatening. Diazepam is tance is met, then the Paramedic should clamp the gastric the drug of choice to terminate the convulsions, tube closed. and the rectal route is a viable alternative for its For ease during transfer, the patient can be disconnected administration.23,24 from the suction and the gastric tube clamped. The atmo- One form of diazepam comes as sphere port of a dual-lumen gastric tube (the blue pigtail on a a gel. It is convenient for rectal administration, and Salem sump) can be connected with the other port, making a actually comes with a rectal administration device. closed circuit. Soft-tip clamps can be used for single-lumen Lacking commercially available gelled diazepam, gastric tubes, but care should be taken to ensure that the teeth of the clamp do not perforate the wall of the gastric tube. the Paramedic can, using a 3½-half inch intravenous needle, improvise a rectal administration device. Rectal Route After withdrawing the needle, the Paramedic attaches Although Paramedics rarely use the rectal route for a medica- the hollow plastic catheter to the ampoule of tion administration, the rectal route has a number of distinc- diazepam and proceeds as normal, passing the plastic tive advantages that make it a desirable site for medication catheter into the child’s rectum and depositing the administration. The rectum has a rich blood supply via the hemorrhoidal venous plexus. Drugs that are absorbed from medication. the rectum avoid inactivation by stomach acids and intestinal enzymes. In fact, 50% of the absorbed drug bypasses the por- tal circulation, minimizing the impacts of fi rst pass metabo- Parenteral Drug Administration lism and biotransformation. These factors, in combination, When a rapid onset of drug action is required (e.g., during allow for comparable drug levels between intravenous admin- an emergency), the most direct route to the target organs istration and rectal administration. The rectal administration sidesteps the gastrointestinal system (enteral administration) route is also useful when the patient is unable to accept oral and enters drugs directly through the central circulation. This medications, such as in the case of infants or if the patient has administration route is called the parenteral route because it persistent vomiting. goes around the gastrointestinal, or enteral, system. Before administering medication using the rectal route, Parenteral drug administration has several distinct advan- and after obtaining consent, the patient must be properly tages over enteral drug administration. Enterally administered positioned. The Paramedic should ask the patient to assume drugs have to be absorbed from the lumen of the intestines a left lateral recumbent position. Once in that position, the where absorption can be erratic. Gastrointestinal drug absorption patient is asked to bring her right knee to the chest as far can also be adversely affected by a number of factors, includ- as practical. The Paramedic should then take care to only ing the presence of gastric secretions, mesenteric circulation, expose what is necessary to accomplish the task at hand, gastrointestinal motility, co-ingested foodstuffs, and a host of while leaving the remainder of the body covered. This mod- other variables.25–27 Drugs deposited into the intestines are also ifi ed left lateral position, called the Sim’s position, provides acted upon by a number of enzymes which can immediately optimal access to the anus while minimally compromising deactivate certain drugs. Conversely, drugs administered via the the patient’s dignity. parenteral route circumvent all of these factors, plus they avoid With the patient in position, the Paramedic would then the liver’s fi rst pass metabolism. Therefore, parenterally admin- take a well-lubricated suppository, or rectal medication istered serum drug levels are more predictable than enterally administration device, and insert the device into the rectum administered serum drug levels for these reasons. approximately 4 inches in adults and 2 inches in children. Finally, drugs administered parenterally can be given The Paramedic should ask the patient to breathe through her to patients who are uncooperative or incapable of coopera- open mouth to help her relax during medication administra- tion (i.e., unconscious). These several advantages combine tion. Once the medication administration device is in place, to make parenteral drug administration routes the preferred the medication is deposited in close proximity to the hemor- drug route in an emergency. rhoidal venous plexus. On occasion, as the medication administration device is Intranasal Route advanced, the Paramedic may feel resistance from a stool that A medication administration route recently adopted by Para- is within the rectal vault. In that case, the device should be medics, is the intranasal route. The intranasal route takes withdrawn and an alternative route considered. advantage of the nasal passages. These nasal passages are 530 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. lined with very vascular mucous membranes which can Table 26-10 Intranasal Medications absorb medications quickly and have a shared connection with the brain. This allows these medications to go directly Drug Use to the brain, without the risk of fi rst pass metabolism associ- Atropine Organophosphate poisoning ated with enteral routes of drug administration.28–30 This fac- Epinephrine Cardiac arrest tor makes intranasal medication administration desirable for Fentanyl Pain management Paramedics under certain conditions. Glucagon Hypoglycemia For example, the combination of a patient with altered Infl uenza Flu prophylaxis mental status, especially one who is combative, and/or a mov- ing ambulance can make obtaining intravenous access diffi cult. Insulin Hyperglycemia/Crush injury The intranasal medication route, which is both quick and easy, Lidocaine Cardiac arrest makes success under these trying conditions more likely. How- Midazolam Seizure control ever, the clear advantage of intranasal administration of drugs Naloxone Opiate overdose is the decreased risk of accidental needle injury. The federal Nitroglycerin Hypertensive crisis/acute coronary syndrome Centers for Disease Control and Prevention (CDC) estimates that as many as 600,000 needlestick injuries may occur annu- Steroids Reactive airway disease ally in the United States. With minimal training, a Paramedic can effectively and safely administer medications while avoid- ing needlestick injury. In some cases, newer Paramedics can Cultural / Regional differences be trained just before use (called “just in time training”). The use of intranasal medication administration technol- In some regions, a common street practice is to mix ogy, a truly needleless system, is an example of an “engi- neered control.” Engineered controls are means of preventing cocaine (an upper) with heroin (a downer), a practice exposure to potentially infectious materials (PIM). In this called speedballing, snowballing, or smack and crack. case, the risk of exposure is through accidental needlestick. The intended effect is to fi rst get high, then “coast” Prevention methods are mandated by OSHA and intranasal down with the heroin. Some “double” inject the two medication administration is consistent with the intent of the Needlestick Safety and Prevention Act of 2000.31 drugs, whereas others inject the heroin and inhale, One drug that shows promise for Paramedic practice is or snort, the cocaine through the nostrils. When naxolone (Narcan®). A study in Denver’s EMS demonstrated the heroin, or co-ingested substances like alcohol, that naxolone can be safely and effectively administered to patients who are suspected of opioid overdose.32 Paramedics depress the respiratory system, the Paramedic could in Denver administered 1 mg in 1 mL per nostril of naxolone consider the use of intranasal naxolone to reverse to patients who met the criteria. For those with suspected opi- the opioid-induced respiratory depression. However, oid overdose, the mean response time was 3.9 minutes. As a if the cocaine was snorted, then the vasoconstrictive result, the Denver Paramedics started 29% fewer IV lines in that patient population. effects of the cocaine may prevent the absorption of However, the use of intranasal naxolone is considered an the naxolone. off-label use. The term “off-label use” implies that using the drug in that manner has not been approved by the federal Food and Drug Administration (FDA), which requires experimental Obtaining intravenous access while a patient is having an studies to approve a drug or the use of a drug in another man- unremitting seizure, a condition called status epilepticus, can ner. In some cases, pharmaceutical companies are not willing to be diffi cult. Intranasal administration of anticonvulsants, such underwrite the expenses of experimental studies for non-patent as midazolam, would be advantageous in controlling the sei- drugs. This should not be construed to mean that a drug cannot zure. One study of intranasal midazolam showed that it had a be used in this manner. Physicians, during the practice of medi- 73% bioavailability when compared to intravenous administra- cine, can order drugs administered in an off-label use. Some tion33 and that it |
had the added advantage of rapid onset. drugs can be given intranasally, some off-label (Table 26-10). The volume administered intranasally should be no more Respiratory Route than 1 mL of liquid and the drug should be atomized to a par- Inhalation of medications has several distinct advantages ticle size of between 10 mcg and 50 mcg, the optimal particle over other means of medication administration. Inhala- size for absorption. Currently several different devices are tion of a drug-laden vapor can quickly lead to therapeutic available that can meet these operational criteria. Contraindi- drug levels in the bloodstream via absorption through the cations for use of intranasal atomizers for medication admin- c apillary-covered alveoli. Inhalation also avoids fi rst pass istration include epistaxis, septal wall defects, and intranasal metabolism in the liver, allowing a rapid buildup of the drug cocaine use. in the systemic circulation. This method avoids the use of Principles of Medication Administration 531 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. needles, thus lessening the threat of blood-borne pathogens a reduction in the velocity of airfl ow cause particles between for the Paramedic. 6 and 20 microns to “fall out” in the nose and particles greater Inhalation therapy also has several drawbacks which tend than 6 microns to fall out in the trachea. As the pulmonary to reduce its effi ciency. Inhalation therapy requires that the tree divides further, more fallout occurs; particles greater than patient be able to assist with treatment (i.e., perform inhala- 2 microns fall out in the bronchi and 2 micron particles fall tion). A lack of coordination is the most frequent cause of out in the bronchioles. The result is that nearly particulate- ineffectual breathing treatments. Inhalation therapy is also free air enters the alveoli.36,37 dependent upon the patient’s breathing pattern, particularly While fallout generally serves a protective function, act- upon the period of holding one’s breath during inspiration. ing as a particle trap to keep contagions and pollution out of the lungs, it also tends to keep large droplets of aerosolized Pulmonary Treatments medications from penetrating the terminal bronchioles and To a large extent, the treatment of pulmonary disorders from distal alveoli. This dramatically reduces the effectiveness of asthma to emphysema is focused on the delivery of respira- many respiratory drugs. tory agents directly into the pulmonary tree. These broncho- To complicate matters further, the propellants used to dilators, such as albuterol (Ventolin®), and anticholinergics, deliver these medications use cold gasses (room temperature such as ipratropium bromide (Atrovent®), are inhaled using gasses) to deliver these medications into the bronchi. Upon one of the several respiratory therapy devices discussed later contact with cold air, the bronchi and bronchioles refl exively to provide immediate relief from bronchospasm. Other respi- spasm air to protect the sensitive alveoli. Paradoxically, the ratory drugs, such as the anti-infl ammatory drug cromolyn respiratory medications which are given to treat broncho- sodium, and even antibiotics, such as tobramycin, can be spasm can induce more bronchospasm. inhaled to treat respiratory disease. Metered Dose Inhaler In the past, the majority of inhaled medications were The metered dose inhaler (MDI) remains the gold standard designed to exert a local pulmonary effect and to treat reactive for respiratory therapy. Portable and simple to operate, the airway disease. Currently, research is underway to administer MDI enjoys a high degree of patient acceptance. This is due vaccines and other antimicrobial treatments which would have in part because it does not require extraordinary breathing a more systemic impact via the pulmonary system. There is maneuvers. Also important to the Paramedic is that the sealed even development and study of an inhaled insulin (Exubera®) pressurized unit is tamper-proof and its contents are protected which uses the capillary-rich lung fi elds to absorb powdered from degradation by light and water. insulin instead of requiring subcutaneous injection.34,35 While the MDI is a preferred personal respiratory treat- ment platform for many, it is relatively ineffective, depositing Personal Protective Equipment less than 20% in the distal lung fi elds. To improve effi ciency, Drug-ladened exhaust from the various respiratory treatment as well as to assist those patients with abnormal breathing pat- platforms present the Paramedic with a potential threat. To terns, a spacer device can be utilized.38-40 The spacer allows a minimize that threat, the federal Centers for Disease Control more controlled inhalation of smaller, ideal-sized drug particles and Prevention (CDC) recommends that Paramedics use a suspended in the vapor within the chamber (see Figure 26-3). mask and gloves while administering these medications. EMS Dry Powder Inhalers vehicles should also be designed so that stale air in the patient compartment is expelled and fresh air circulated frequently. Dry powder inhalers (DPI), such as the Diskhaler®, use a solid In some cases, where vapor is visible, it may be reasonable for drug which is pulverized into micro-fi ne particles for inhala- a Paramedic to wear eye protection, such as a splatter shield tion. The DPI, while an effective platform for the delivery of or goggles, while in close proximity to the patient. pulmonary medications, depends upon the patient’s inspiration for uptake of the drug and proper dispersal of the drug across Fluid Dynamics the lung fi elds. If the patient has a reduced inspiratory fl ow, less Air, like water, is fl uid and is subject to laws of fl uid dynam- than 60 L/min, then the drug will not reach the distal alveoli. ics. For example, the more resistance air encounters (e.g., in a narrowed airway), the more turbulent the airfl ow. Turbulent airfl ow is slower. The structure of the lungs takes this fact into Street Smart account and the airways divide some 23 times before they reach the alveoli, allowing nearly non-existent airfl ow at the Healthcare providers have complained of headaches, alveolar level. This dead air in turn permits easier diffusion of bronchospasm, and conjunctivitis from secondhand gasses such as oxygen and carbon dioxide. The slowing of air in the airways also serves another pur- exposure to the dust exhausted from a DPI. Use of PPE pose—it encourages fallout. Fallout occurs whenever large can help to reduce the incidence of passive exposure particles carried in the air current settle out as airfl ow velocity to the droplets. is lost. An example of this is dust settling out. Turbulence and 532 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Figure 26-3 Use of an MDI with spacer. Small Volume Nebulizer The small volume nebulizer (SVN) is an alternative plat- form for the delivery of inhaled medications. More diffi cult to set up and operate, it is thought to produce a better particle size for inhalation. Hypothetically, more of the drug is depos- ited in the patient’s alveoli. The medication is suspended in a stream of air which is then smashed against a round surface in the SVN. The resulting liquid shear creates micro-fi ne particles, in the 1 to 3 micron range, which are ideal for inhalation. Three factors combine to alter the effi ciency of this mechanism: jet design, gas pressure, and fl uid dynamics. Figure 26-4 Assembly and operation of the SVN. It is critical that the gas-emitting jet of the SVN has the ideal orifi ce diameter, as well as distance to the baffl e, for assembly, SVN-BVM-ET, changes the conditions under atomization. For an SVN to function properly, the gas pres- which an SVN normally operates. sure must be adequate, but not excessive. In addition, the sur- First, an average 26 cm long, 8 mm internal diameter face tension of the aqueous solution, usually a function of (ID) endotracheal tube decreases dead space from an aver- the liquid’s viscosity, must be within acceptable limits. These age of 75 mL in the trachea to approximately 60 mL, but factors being equal, the SVN is a good platform for the deliv- does so at a cost. The smaller dead space is owed to a smaller ery of pulmonary medications to the patient in respiratory airway lumen. A smaller airway lumen immediately results in distress. greater airway resistance. Greater airway resistance produces Prior to using an SVN, the Paramedic should obtain a greater fallout of the inspired vapor. Decreasing the lumen history from, and perform a physical on, the patient. A dem- of the airway (e.g., from an oral endotracheal tube size of onstrated history of responsiveness to MDI bronchodilators 8 mm to a nasal endotracheal tube size of 6 mm) increases the indicates a greater likelihood of success with the SVN ( Figure airway resistance exponentially, in this case 4.2 times more 26-4). The physical examination should include auscultation resistance. for wheezes or, more ominously, absent breath sounds, as well Resistance is also increased with the higher ventilatory as pulse oximetry. Some Paramedics obtain a baseline peak fl ow rates, typically seen in manual or mechanical ventila- fl ow meter reading as well. Key to assessing the effectiveness tion. The combination of increased airway resistance, and of any SVN treatment is the patient’s subjective judgment airway turbulence, combine to generally cause less medica- regarding her own dyspnea. tion disposition in the alveoli, from a normal of 20% to less than 15%.41 Use of an In-Line Small Volume Nebulizer To defeat these disadvantages, the American Association in Bag-Valve-Mask Assembly of Respiratory Therapists recommends that intubated adult In special circumstances, an intubated patient could benefi t patients, who are receiving respiratory treatments, should be from a respiratory treatment. In those cases, an SVN may ventilated with a smaller tidal volume (< 500 mL). Gentle be attached in-line with the bag-valve-mask assembly. This ventilation with reduced fl ow, as well as the addition of an Principles of Medication Administration 533 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. inspiratory pause at the height of each positive pressure ven- between repeated patient uses. Today, most Paramedics use tilation, should be employed. plastic syringes, prepacked in sterile wrappers, for individual patient use. However, glass syringes are still available for use Topical Route in circumstances in which the drug would adversely react For sustained systemic delivery of a medication, an alter- with the plastic syringe. native administration is the topical route. Medication, con- The components of a hypodermic syringe include the tained within a cream carrier, is applied to the skin and is then syringe and the needle. The connection of the syringe to the absorbed directly into the subcutaneous capillary beds, where needle is called the adaptor and the connection of the needle it passes on to the central circulation. The rate of absorption to the syringe is called the hub. Some needle adaptors attach is variable and dependent upon several circumstances. to the syringe hub by use of a twist connection, called a luer Factors affecting topical medication absorption, also lock, where the adaptor on the syringe is grooved and will called transdermal medicine, include the skin’s vascularity mate with a fl ange on the needle hub. This provides a more and perfusion, as evidenced by capillary refi ll and tempera- secure connection, decreasing the chances of accidental dis- ture (warmth). Furthermore, skin conditions such as rashes, connection. Other syringe adaptors simply slide inside the eczema, and open lesions can also affect absorption. |
needle hub and are called slip-tip adaptors. A number of medications are available in transdermal The shaft of the syringe is called the barrel. Syringes patches including nicotine, hormone replacement, opiate are labeled according to the volume within the barrel analgesics, and nitroglycerine. An example of a topical (i.e., 1, 3, 5 mL) and the calibrations on the side of the barrel. medication applied by Paramedics in the fi eld is nitroglycer- Traditional hypodermic syringes are marked in divisions of ine paste. A Paramedic takes a ribbon of paste, measured in a milliliter, and those would be called a 1 mL syringe, 3 mL inches, and applies it to an impermeable paper barrier which syringe, and so on. Many hypodermic needles have dual cali- is then applied onto the skin. Assuming that the patient bration: tenths of milliliter on one side (metric) and minims is not hypoperfused and/or hypothermic, the medication- (common household) on the other. Paramedics should be laden nitroglycerine cream melts, is absorbed through the cautious and not confuse 0.10 mL with 10 minims, as they epidermis, and enters the subcutaneous capillary beds are not equivalent measures. underneath. Nitroglycerine can have a profound effect on An insulin syringe is an exception to the rule of syringe blood pressure, inducing almost immediate hypotension. marking. Insulin is not administered in milligrams per millili- Therefore, the location of the paste/patch should be in an ter (mg/mL), as most standard medications are, but in interna- easy-to-reach place such as the upper arm or posterior tional units (IU) determined by bioassay. Therefore, a special shoulder. To remove the nitroglycerine paste quickly and syringe, marked in units, is manufactured for insulin injec- effectively, a tongue blade can be scraped across the skin in tion. The insulin syringe looks similar to the 1 mL syringe the direction of hair growth. frequently used for tuberculosis testing. Paramedics should look at the syringe carefully to avoid confusing a tuberculin syringe with an insulin syringe. The purpose of a syringe is to either inject a liquid Street Smart medication out of the barrel or to withdraw blood into the barrel. In both cases, the barrel of the syringe is fi lled with The cream used in the manufacture of nitroglycerine a liquid. When the horizontal surface of a liquid interfaces paste is similar to the conductive medium used for with the vertical wall of the barrel, cohesive forces (i.e., surface tension) tend to pull it away from the wall while manual defi brillation. It is prudent to remove any adhesive forces between the syringe’s wall and the liquid nitroglycerine patch or paste prior to defi brillation/ tend to pull it toward the wall of the barrel. As a result, the cardioversion.42 Failure to remove a patch/paste may liquid moves upward. These two forces—surface tension result in arcing and a loss of defi brillation energy. and wall adhesion—cause the liquid’s surface to form into a concave-curved shape called a meniscus. As a matter of practice, Paramedics compare the bottom of the meniscus with the calibrations on the barrel in order to determine the Injections volume of drug in the syringe. Tools for Injections To facilitate injecting drugs, or withdrawing blood, a plunger is placed inside the barrel. The head of the plunger The quintessential tool for parenteral drug injection is the is fi tted tightly inside the barrel, thus preventing liquid from hypodermic syringe. Whether it is used for a subcutaneous seeping past the plunger. However, on occasion, an imperfect injection, an intramuscular injection, or to gain intravenous match will occur. If this happens, liquid will seep past the access, a syringe is a key component of the assembly. plunger and drip the drug onto the Paramedic’s hands. For In the past, glass syringes with calibrations carefully this reason, Paramedics are advised to always wear gloves etched on their sides were used in the hospital and sterilized whenever a syringe is used. 534 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. At the apex of the plunger’s head is a convex head. The a given volume of liquid at a faster rate. To reduce the pres- head’s shape is intended to offset the meniscus, leaving a fl at sure being applied, the Paramedic may alternatively choose a surface that is easier to measure. In the past, nurses would larger diameter (smaller gauge) needle. draw up approximately 0.1 mL of air, an air bubble, into the The length of a needle, the other physical characteristic syringe to offset the effect of the meniscus. However, the con- of a needle, is also typically a function of the task at hand. A vex head of the plunger corrects this problem, making the shorter needle, approximately 1 inch, is used when injecting a practice unnecessary. If the plunger head is convex, then the drug into the medication port of an intravenous set. By using Paramedic should measure the volume of drug from where a longer needle, the Paramedic would risk bypassing the pro- the plunger touches the barrel of the syringe. tection afforded by the hard plastic of the medication port and To administer a liquid drug, the Paramedic merely has piercing the tubing’s soft sidewalls. to push down on the shaft of the plunger to push the drug A longer needle is used when an intramuscular injection out of the syringe. However, the pressure applied to push the of medication is given to an obese patient. In some cases, a drug out can cause the patient some discomfort. To ease the needle as long as 4 inches is needed so that the medication patient’s pain and to give the Paramedic added control of reaches the muscular layer. the syringe, most syringes have a fl ange at the top. By plac- A needle is essentially a hollow wire which is cut to ing her fi rst and second fi nger under the fl ange and pushing length. The end of the wire is often cut obliquely, in such a upward on the fl anges while simultaneously pushing down- fashion that a sharp leading edge is created, called the point. ward with her thumb on the plunger, the Paramedic can con- The sharper the point, the easier the needle will enter into the trol both the rate of administration as well as the pressure patient’s skin or the stopper in a vial. applied to the patient’s skin. The needle now has an angled surface called the bevel. The bevel, the angle of the needle point, is calculated for Hypodermic Needle a specifi c purpose. A regular bevel is designed to quickly The heart of the hypodermic syringe is the needle. Needles pierce the skin with a minimum of pain. A Huber bevel is are generally made of surgical-quality stainless steel and intended to pierce a stopper without coring it, preventing may be either pre-assembled with the syringe or individually leakage of the contents within the catheter from leaking out packaged in a sterile wrap. The parts of the needle include the of the stopper when the needle is withdrawn. Blunt bevels, hub and the shaft. The hub, generally made of plastic, has an used for intradermal injections, are designed to deposit the external fl ange designed to mate with the syringe adaptor. medication just below the skin without penetrating deeper Like syringes, needles come in a variety of sizes and layers of skin below. lengths, each according to their intended purpose. Needles are measured in gauges—the smaller the number means the larger Needle Safety the diameter of the needle (e.g., 14 gauge > 20 gauge). The decision of which gauge to choose is largely a func- The majority of exposures healthcare workers, including Para- tion of two factors. The fi rst factor is the viscosity of the fl uid. medics, experience to blood-borne pathogens are the result of The thicker the fl uid to be injected or withdrawn through the accidental puncture of the skin with a hollow-bore needle. needle, the larger the needle that will have to be used. The United States Centers for Disease Control and Preven- tion estimates that over 600,000 needlesticks will occur annu- ally. Many of them are preventable. Infection control expert Kathrine West, RN, estimates that each needlestick injury Street Smart will cost employers approximately $1,200 in emergency care, lost hours and wages, and medical follow-up for a case with Paramedics seldom use less than an 18 gauge needle a non-infectious exposure.43 when drawing blood, either through an intravenous In response to this occupational hazard, the U.S. Con- gress strengthened the Occupational Safety and Health catheter or via direct needle insertion. Smaller Administration (OSHA) blood-borne pathogens rule, enacted catheters tend to break the red blood cells apart in 1991, with the Needlestick Safety and Prevention Act of in the turbulence, called lysing of the red blood 2000, effective the April 18, 2001. The Needlestick Safety cells. Lysed red blood cells spill the cell’s contents, and Prevention Act requires wider use of engineering con- trols which can prevent needlestick injury.44 Examples of including potassium, into the plasma. The result is engineering controls which can help prevent needlestick false plasma values obtained from the laboratory. injury include retractable needles, needles that are withdrawn into the syringe barrel by a spring-action mechanism, self- sheathing needles, needles that have a retractable hard case The other factor in needle selection is the speed of deliv- that is advanced over the needle as the needle is withdrawn, ery. A smaller diameter needle creates greater resistance to and hooded needles that have a protective covering over fl ow (i.e., friction loss) and requires higher pressures to push the needle. Principles of Medication Administration 535 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Manufacturers, in an effort to eliminate the needle entirely, have created needleless medication systems which use non-needle connections at the medication ports. They also have created jet injection systems that use high-pressure air to open the skin temporarily while medicine is deposited beneath the skin. However, there are still circumstances in which a needle will be used. Therefore, the Paramedic must be familiar with its use. Every Paramedic is responsible for safely disposing of used/contaminated needles into a safe sharps container. The sharps container should be close at hand, within arm’s reach, and be easy to access. Under no circumstances should a nee- dle be bent or cut. Cutting a needle can create a microspray of drug and/or blood in the air, which can be inhaled or settle into the eyes. Figure 26-5 Preparing a prefi lled medication Medication Containers syringe. Medications are packaged in either vials or ampoules. The Paramedic must withdraw the drug from its container, into a needle and syringe, before use. Ampoules, a single-use, single-patient drug container, is manufactured alone or as a part of an ampoule with syringe delivery system, sometimes called a “preloaded ampoule.” In the emergency setting, where time is of the essence, these prefi lled ampoule/syringe systems are commonplace. They are generally fi lled with the amount of drug needed to treat a 70-kg patient. When using one of these ampoule systems, the Bristo- jet®, the Paramedic removes the two end caps which pro- tect the ampoule and the syringe. With the caps removed, the Paramedic would mate the two pieces, twisting them together so that a recessed needle within the syringe portion would penetrate the stopper. When this step is completed, the Paramedic would discard any extra drug and air which may be contained within the ampoule and proceed to intro- duce the syringe’s preset needle |
into the medication port of the administration set or to inject the drug into the patient (Figure 26-5). The Paramedic should use caution when discarding excess drug so as to avoid accidental injury. Drugs, carelessly discarded into the air, can splash onto the ambulance ceiling and fall back into the eyes of unsuspecting occupants in the patient compartment, including the patient. Some ampoules still have to be broken before the medi- cation can be withdrawn (Figure 26-6). The Paramedic should fi rst shake the medicine down out of the ampoule’s neck and into its body. Once accomplished, the Paramedic would then place the ampoule on a fl at fi rm surface and grasp Figure 26-6 Safely break the glass stem of the ampoule’s body with the thumb and forefi nger of the the ampoule before inverting the ampoule and nondominant hand. Using either a commercially available withdrawing the medication. ampoule breaker (which is preferred) or a 2-inch gauze pad, the Paramedic would grasp the ampoule’s head and, while holding it in a direction away from him, smartly snap the Paramedic would introduce the syringe, with a glass-fi ltering ampoule’s neck. The Paramedic should avoid the sharp shards needle, into the medication just below the meniscus. of glass from fl ying into the eye. The Paramedic is advised to In some cases, the Paramedic may elect to invert the wear protective eyewear, as splinters of glass can fl y from ampoule and withdraw the medication. The medication will the ampoule into the eye. Having accessed the ampoule, the remain in the ampoule, provided the needle does not touch 536 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. the walls of the ampoule and break the liquid surface tension. However, most Paramedics, particularly when in the back of a moving ambulance, prefer to keep the ampoule on a fi rm surface with the bottom down in order to aspirate the drug into the syringe. When the medication has been withdrawn, and the ampoule is useless, then the glass ampoule should be discarded like any other sharp, into an approved sharps container. Vials are intended for multiple use and therefore are more likely to become contaminated. Some EMS organiza- tions and healthcare institutions require that the vial’s con- tents be used within a specifi c period of time (e.g., 24 hours) and then discarded in order to avoid possible contamination. Many Paramedics discard vials after use and do not use vials on multiple patients. Figure 26-7 Withdrawal of medication from a The risk of contamination is higher when a Paramedic vial. is in the high-pressured, time-limited environment of an emergency. Innocent errors in medical asepsis are frequent enough that single-patient ampoules, and individually pack- the nondominant hand, the needle is then withdrawn quickly aged patient supplies, are routinely used by Paramedics to (Figure 26-7). avoid these problems. Inserting a needle into a dime-sized stopper held over the When a vial is used, the Paramedic should fi rst remove Paramedic’s head, especially while in a moving ambulance, is the plastic cover, then take a moment and clean the stopper dangerous and places the Paramedic at risk for a needlestick with an alcohol-soaked pad or gauze, commonly called a prep injury. pad, to remove gross surface contaminants. On occasion, air bubbles will inadvertently arise, typi- After calculating the proper volume for the dose, based cally if the medication is withdrawn too fast. If the air bub- on the drug’s concentration, the Paramedic would then draw bles are visible in the barrel of the syringe, a smart tap with up an equal volume of air. Vials are a closed system, and the forefi nger will generally dislodge them, allowing them to withdrawing a volume from the vial without replacing it with rise to the top of the syringe. The air can then be expressed an equal volume would create a vacuum, one that could draw from the syringe. in any surface contamination. Furthermore, the Paramedic will encounter diffi culty withdrawing the medication if the pressures are not equalized. Therefore, it is essential that the Street Smart Paramedic fi rst inject air, in equal volume, into the vial before withdrawing the medicine. Some Paramedics use a large-bore “mixing” needle Conversely, overpressurizing the vial, with additional volume of injected air from the syringe may make the drug to draw the medication up quickly from a vial, then withdrawal quicker and easier. However, as the needle is replace it with the smaller needle used for injection. withdrawn a fi ne mist of medicine will escape into the air. This helps decrease potential contamination as Some commonly used medications which are packaged in well as speeding up the process of medication a multidose vial (e.g., epinephrine) can be very caustic to the Paramedic’s unprotected eyes when aerosolized in this administration. fashion. To withdraw medicine from the vial, the vial should be placed on a fi rm fl at surface and held in place by the thumb Routes of Injection and forefi nger of the nondominant hand. As the Paramedic Hypothetically, the best means to get a drug directly into a introduces the needle into the vial’s stopper, the bevel should target organ is to inject the organ directly. Intrathecal (within be facing upward and a slight downward pressure exerted. the spinal column), intrapleural (between the lung’s pleura), The downward pressure will ensure that the needle’s bevel intra-articular (within a joint), and intracardiac (within the slices the stopper and does not core it. With the needle in heart) injections are just some examples of medication injec- place, visible just beyond the stopper, the Paramedic would tions into target organs. invert the vial, inject the premeasured volume of air into the With the exception of intracardiac injections performed vial, and then withdraw the medicine from the vial. by early Paramedics before the advent of current intravenous Once the syringe is fi lled, the Paramedic would then techniques, Paramedics generally have injected drugs into the invert the vial again and place it back onto the fl at surface. peripheral circulation and depended on the circulatory system With the vial stabilized between the thumb and forefi nger of to get the medication to the target organ. Even drugs injected Principles of Medication Administration 537 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. into the endotracheal tube depend on absorption from the With the needle in place, the Paramedic would gently alveolar capillary beds. aspirate to ensure that the needle was not inadvertently placed The greatest drawback of indirect parenteral injection may into a vein. If a blood fl ash is witnessed, then the needle should be its dependence on adequate circulation to reach the target immediately be withdrawn, the medication pulled back into organ. In many cases, the patient presents to the Paramedic the syringe, and new equipment prepared. The bloody medi- with inadequate circulation (these patients are hypoperfused). cation solution should not be injected. Instead, a new dose of Subsequently, insuffi cient quantities of drug get to the target medication should be drawn up in a new syringe. organs when injected via an indirect parenteral route. Intradermal Injection Preparation for Parenteral Injection Paramedics perform intradermal injections under a limited set of circumstances. Intradermal injection is used when pre- As in all procedures performed, the Paramedic would iden- paring an intravenous site with a local anesthetic. Intradermal tify the patient, introduce oneself, inquire about the patient’s injection is also used for tuberculosis testing. The objective allergies, advise the patient about the procedure’s intended of an intradermal injection is to place a small quantity of effects, and then explain what reasonable and foreseeable medicine just under the epidermis and in close proximity of risks could be experienced. the subcutaneous tissue. Because the space within the skin After obtaining informed consent, the Paramedic should is very small, no more than 0.5 mL should be injected into practice medical asepsis, starting with hand washing with one site. soap and water or an acceptable hand sanitizer and then don The tools that the Paramedic needs to assemble for an gloves. Generally, non-sterile gloves are adequate for the intradermal injection include a 1 mL syringe and a short nee- tasks at hand. dle about 3/8 inch to 1/2 inch that is either 26 or 27 gauge. Success in many of these injection techniques can be Sites for intradermal injection include the anterior forearm, improved if the Paramedic takes the time to fi rst position the the upper chest, and the posterior shoulders. After drawing up patient. With the patient resting comfortably, the Paramedic a small quantity of the medication (typically 0.01 to 0.1 mL), would proceed by selecting a site, chosen in accordance the patient is prepared as previously described. with commonly accepted sites used for that particular injec- Grasping the syringe as one would a sewing needle, the tion technique. When assessing the various sites for injec- Paramedic would place the needle gently on the surface of tion, before choosing one, care should be taken to ensure that the skin, with the needle at a 15-degree angle, and advance the selected site is not hard, swollen, or tender and is free of the needle under the skin. With the length of the needle rashes, moles, birthmarks, burns, scars, or broken skin. under the skin, a small 1 cm blister is created by injecting the After identifying the intended injection site, the Paramedic medication. This blister, called a bleb, is about the size of a would place an isopropyl-soaked pad on the site and, working mosquito bite. The needle should remain visible just under outward in ever-expanding circles, prepare an area approxi- the skin the entire time. mately twice the length of the needle. The purpose of the alco- When the task is completed, the needle is withdrawn in hol bath is to remove any gross contaminates from the skin’s the same direction as it was advanced and immediately placed surface as well as oils that would prevent the bandage from in a sharps container. If capillary bleeding is evident, then an adhering to the skin. The alcohol bath itself does not render the adhesive bandage can be placed loosely over the site. skin sterile, just clean. Incidental surface contamination (bac- teria and the like), which may be dragged into the wound cre- ated by the injection is dealt with by the body’s defenses. Capillary Blood Draw Iodine-based solutions, such as Betadine®, are generally Paramedics are increasingly requested to perform capillary not used because iodine seeping into the stab wound created by blood sampling in the fi eld. The capillary blood can then the injection can be irritating. It may also delay new cell growth be used for blood glucose analysis or fi eld Troponin levels. and damage sensitive tissues in the vicinity of the injection. These point of care blood tests enhance the Paramedic’s abil- With the patient prepared and the area prepped, the Para- ity to provide immediate emergency services while still in the medic would then pick up the prefi lled syringe in the domi- fi eld and to transmit critical information to the emergency nant hand and remove the needle guard. The Paramedic must department. then stabilize the skin with the nondominant hand. With the The most common capillary blood draw is the fi n- needle and syringe fi rmly in hand, the Paramedic would then ger stick. However, a heel stick may be preferred for small proceed to fi rmly, and with authority, insert the needle under infants or children. With the limb in the dependent |
position, the skin. Studies have shown that the speed of insertion does encouraging peripheral vascular congestion, the Paramedic not decrease the pain which the patient may experience.45 would proceed with the routine battery of questions in order However, hesitation on the Paramedic’s part is telegraphed to obtain consent. to the patient, which may cause the patient’s anxiety may Once consent is given, the side of the fi nger tip proximal increase. Patient anxiety has been shown to have a positive to the pad of the fi nger tip is cleansed with an alcohol prep correlation to the perception of pain. pad (wipe). While the alcohol is drying, the lancet is picked 538 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. A complication of frequent subcutaneous injections at one site, such as may occur with repeated insulin injections, is tissue fi brosis. Tissue fi brosis occurs when phagocytes infi ltrate the area and attempt to remove the irritating foreign matter (the medication) and create a sterile abscess. Drugs injected into fi brotic tissues cannot be absorbed readily and will adversely affect the patient’s response to the medication. Generally, a 1 mL to 3 mL syringe is used for subcuta- neous injections. The syringe is tipped with a 1/2-inch 26 to 30 gauge needle. With the syringe loaded with no more than 1.5 mL of medication for one injection and held in the domi- nant hand, the Paramedic would gently grasp the skin around the site with the nondominant hand. With the skin tented approximately 1 inch between the fi ngers, the Paramedic Figure 26-8 Capillary blood draw. would insert the needle into the skin at a 45-degree angle. If the skin is tented approximately 2 inches, then it is acceptable to insert the needle at a 90-degree angle. Once the needle is up by the dominant hand and prepared. In some cases, a pro- inserted into the skin, the Paramedic would gently aspirate tective cover must be removed from the lancet. In other cases, for blood and then inject into the subcutaneous pocket which the lancet is spring-loaded and retracts back into a protective has been created by pinching the skin. sheath. In those cases, the lancet may have to be activated (armed) before use. Intramuscular Injections Grasping the patient’s fi nger with the gloved nondomi- nant hand, the Paramedic would place the lancet over the Intramuscular injection is a common method of medication site and either pierce the skin in a quick darting motion or administration. Once the drug is deposited between the lay- depress the actuator of the spring-loaded lancet. Once the ers of the muscle, and below the subcutaneous tissue, it can skin is pierced, it should bleed freely. In some cases, it may be escape into the surrounding capillary beds within the muscles necessary to gently milk the tip of the fi nger to get a hanging and provide rapid systemic action. Intramuscular injection is drop of blood. Vigorous or forceful pressure on the tip of the frequently used for the uncooperative patient who is in need fi nger may damage local tissue. It might also introduce new of sedation/chemical restraint to prevent harm to himself or fl uids into the sample, possibly causing any subsequent blood others. Antipsychotic agents, such as haloperidol, can be test results to be invalid. given in this manner during a psychiatric or behavioral emer- After immediately disposing of the lancet in an approved gency. However, not all medications should, or can, be given sharps container, the Paramedic would collect the droplet via intramuscular injection. Digoxin, diazepam, and pheny- sample and then apply a gauze pad or self-adhesive bandage toin are just some of the medications that are poorly absorbed to the fi ngertip. The patient should be encouraged to elevate via intramuscular injection. the arm above the heart (Figure 26-8). Intramuscular injection has an advantage over intra- venous injection in the elderly and immunocompromised patient. Intravenous injection bypasses the majority of the Subcutaneous Injections body’s defenses against infection, whereas intramuscular Subcutaneous injection of medication is the slowest and least injection preserves several of those defenses. dependable means of obtaining therapeutic drug levels in the Intramuscular injections depend on adequate periph- bloodstream. Local conditions in the skin, such as capillary eral circulation. Intramuscular injections, and intramuscular perfusion and adipose tissue, combine to make drug absorp- injections in certain sites, may be contraindicated in patients tion slower and more erratic than intravenous injection.46-48 with peripheral vascular disease and disease states which cre- Yet for some medications, such as heparin and insulin, the ate Hypoperfusion (e.g., anaphylactic shock). Intramuscular subcutaneous route is acceptable. injections also create trauma during the injection, creating a After providing the appropriate information and obtain- puncture wound. Some patients with coagulation disorders, ing consent, an acceptable site is prepared. A variety of sites such as the patient with hemophilia or one who is status-post are acceptable for subcutaneous injections including the fi brinolysis, may experience signifi cant bleeding (a hema- abdomen, the lateral aspects of the upper arm, and the ante- toma) at the injection site. rior thigh, as well as the ventrodorsal gluteal area. Studies The slow distribution of intramuscular medications makes have shown that the subcutaneously injected medication is intramuscular injection a preferred route for so-called depot absorbed quickest from the abdomen, followed by the upper medications. Depot medications are medications deposited arm and then the anterior thigh. There is no data comparing under the skin which produce sustained therapeutic levels the gluteal injections to the other sites. over a longer period of time. Principles of Medication Administration 539 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. The intramuscular needle range is between 18 to 24 gauge Greater Vastus Injection and the selection of the length of the needle is more impor- trochanter lateralis site tant than the gauge. If the patient is less than 110 pounds (50 kg), a 1-inch needle will generally reach the muscle below the skin. If the patient weighs between 110 and 220 pounds (50 to 100 kg), then a ½- to 2-inch needle is appropriate. For patients over 220 pounds, a needle longer than 2 inches may be needed. In the case of the morbidly obese patient, it may be necessary to use a 4-inch needle.49 It is important that Femoral Rectus Lateral artery femoris femoral the Paramedic carefully assess the injection site. Variations condyle in muscle development can alter the Paramedic’s decision regarding needle length. Figure 26-10 Vastus lateralis injection site. Because of the barrel’s diameter, a 3 mL syringe is gen- erally used for intramuscular injections as it provides better control. However, the syringe chosen is dependent on the vol- ume to be administered per injection which is, in turn, depen- dent upon the site selected. After the patient has consented and is properly prepared, Acromion the site is selected. There are four common intramuscular process injection sites to choose from, and each site has specifi c Clavicle advantages over the other sites. Scapula Deltoid The fi rst site, the ventrogluteal (VG), is located on the muscle Humerus lateral thigh proximal to the hip.50–52 The muscles underly- Axilla ing the VG are the gluteus medius and the gluteus minimus. Radial nerve What may be more important is that no large veins, arteries, Deep brachial or nerves underlie the area. Beyea and Nicoll reported that artery the ventrogluteal site had the lowest risk of nerve damage, muscle spasm, gangrene, and pain of any of the other injec- Figure 26-11 Deltoid injection site. tion sites. To locate the site, the patient is placed in a side-lying position (lateral recumbent). The Paramedic would then pal- up the medication in the syringe and prepares the patient for pate the bony prominence where the femur inserts into the the injection. Up to 2 mL of medication can be injected in pelvis. Placing the palm of the hand over the insertion, the the vastus lateralis without causing the patient signifi cant Paramedic would grasp the anterior superior iliac crest with discomfort. the fi ngers. The injection site is between the fi rst fi nger and Paramedics generally prefer to use the deltoid muscle the thumb (Figure 26-9). (Figure 26-11) because it requires less patient exposure and An alternative intramuscular injection site is the vastus is easier to access. The deltoid muscle overlays the shoulder lateralis (VL) (Figure 26-10). After positioning the patient and extends downward toward the elbow, forming an inverted in the supine or semi-Fowler’s position, the anterior thigh is triangle in the process. With the patient in high-Fowler’s posi- exposed. The Paramedic mentally divides the vastus lateralis tion, the Paramedic would instruct the patient to bend the arm muscle into three equal portions. Choosing the middle sec- at the elbow, thus relaxing the deltoid muscle. The Paramedic tion of the VL, the Paramedic prepares the intended injection would then palpate the bony prominence where the humerus site with an alcohol-soaked pad. Next, the Paramedic draws inserts into the shoulder. Locating the humerus, the Paramedic would measure approximately three fi nger-breadths down to Anterosuperior Greater the middle, or belly, of the deltoid muscle and prepare the site iliac spine trochanter with an alcohol-soaked pad. Approximately 1 mL of medica- tion can be given into each deltoid. The deltoid site should not be used for children who lack the muscle development in the shoulders appropriate for the injection. The most common intramuscular injection site is the dor- sogluteal (DG) (Figure 26-12). A large muscle, the gluteus medius, underlies the injection site and provides an excellent location for a depot of medicine. The patient is typically in Injection site the prone position (an uncommon position for patients to be transported by EMS) and then the patient’s buttocks exposed. Figure 26-9 Ventrogluteal injection site. Alternatively, the patient can be placed in the side-lying 540 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Injection Iliac crest disk or a cream that is applied to the intended injection site site and left in place for a minimum of 60 minutes. Following Posterosuperior removal of the dollop of cream, or the patch, the skin should iliac spine be anesthetized.53,54 While EMLA cream may not be con- Superior venient for use in the fi eld, it should be considered in cases gluteal artery where repeated injections of medicine may be needed. Gluteus and vein Alternatively, fl uori-methane has great potential for maximus muscle use in the fi eld.55–57 Fluori-methane, a topical refrigerant, numbs the skin at the injection site in as little as 15 seconds. Fluori-methane, also referred to as a vapocoolant spray, can be either applied directly to the skin, though some patients Figure 26-12 Dorsogluteal injection site. complain of transient sharp discomfort, or onto a cotton ball for topical application. One study suggested that a vapocool- ant spray was equally as effective as EMLA cream. Another position, or lateral recumbent position, and only the upper study indicated that placing ice alone on the skin, for 30 sec- portion of the buttocks and the patient’s fl ank is exposed. It onds, was not effective in reducing pain during injection. should be noted that the gluteus is not synonymous |
with the The next potential source of injection pain is the trauma buttock. The gluteus is located proximal to the inferior por- created by the needle’s insertion. One study suggests that the tion of the patient’s fl ank. biomechanics of injection (i.e., proper injection technique) As the gluteus medius is relatively large, compared to is important to the patient’s comfort.58–61 A needle held and the muscles underlying the other injection sites, use of the inserted in a linear manner, perpendicular to the plane of the DG site is advantageous during a restraint situation. In those skin, reduces the “path width” compared to the path width situations where the patient needs sedation and/or chemical seen with a curved (arcing) needle path. Tissue shearing is restraint for a behavioral emergency, the DG offers a large minimized and therefore patient discomfort lessened. “target” and thus a greater chance of success. After the patient Finally, there is the matter of the medication deposited has been given sedatives, he should be placed in the supine, within the muscle. This discomfort is, in large part, due to the face-up position as soon as possible in order to monitor respi- leakage of the caustic and irritating drugs into the pain recep- rations and avoid positional asphyxia. tors of the subcutaneous tissues. The deeper muscle layers To ascertain the location of the DG injection site, the are relatively free of pain receptors. The application of a few entire one buttock is mentally divided into four quadrants. easy to perform techniques which “lock” the drugs into the The uppermost and outermost quadrant, proximate to the muscle will decrease the patient’s discomfort and improve the iliac crest, is prepared. Great care should be taken estimating Paramedic’s confi dence with injection skills. the injection site as the sciatic nerve transverses two of the Two techniques have been developed by nurses to other three quadrants. Unintended injection into the sciatic decrease this leakage and the accompanying discomfort. nerve can lead to paresthesia, paralysis, and permanent nerve Both techniques involve careful attention to the particulars damage. Alternatively, the Paramedic can draw an imaginary of the injection technique. The fi rst technique, the airlock, is line from the height of the iliac crest to the insertion of the performed while preparing the drug in the syringe for injec- femur and choose the midpoint of that line. tion. The second technique, the Z-track, involves manipula- Generally, the DG injection site is reserved for adults. tion of the injection site during the injection. Children must be walking before a DG injection site should The airlock technique has the Paramedic injecting a small be considered. In the adult patient, a maximum of 5 mL can bubble of air into the injection, essentially sealing off the drug be injected into each DG site. However, the Paramedic should below from leaking out to the subcutaneous tissues above. To consider splitting the dose and doubling the sites for injection create an airlock, the Paramedic fi lls the syringe with the medi- to increase patient comfort. cation as usual. With the syringe clear of the ampoule, the Para- medic would then withdraw the plunger further, clearing the Painless Injections drug from the needle and entraining about 0.1 mL of air into the Patients complain, sometimes bitterly, about the discomfort syringe. It is important that the Paramedic verify that the correct which can accompany an intramuscular injection. This dis- volume of drug remains in the syringe (Figure 26-13). comfort can be related to the needle puncture and the tear- Quickly inverting the syringe should cause an air ing/shearing of the dermis and muscle as the needle passes bubble to be created at the apex of the plunger. With the air through the tissue layers, as well as the presence of the medi- bubble in place, the Paramedic would proceed to the injec- cation within the tissue. tion. For the airlock technique to work, it is essential that the Several products are available that help to reduce the syringe remain at an upright 90-degree plane from the injec- pain of needle insertion. The fi rst, a eutectic mixture of local tion surface. This ensures that the air bubble is injected at anesthetics (EMLA), is a cream of lidocaine 2.5% and prilo- the end of the injection. The ventrogluteal (VG) site and the caine 2.5%. EMLA is available as a self-adhesive anesthetic dorsal gluteal (DG) site are conducive to this technique. Principles of Medication Administration 541 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Skin pulled taut Skin released Figure 26-14 Z-track injection technique. Injection Site Massage Some controversy surrounds the common practice of mas- saging the area surrounding the injection site immediately after the injection. In some cases, it is acceptable to gently massage the area surrounding the injection. Gentle pressure applied to the area dissipates the impact of the sharp pain receptors through competition with various pain fi bers. How- ever, some medications are caustic to the muscle tissue. With these medications, massaging the area distributes the medi- cation over a larger area, creating more discomfort for the patient. The Paramedic should be knowledgeable about the med- Figure 26-13 Airlock technique. ication before just routinely proceeding with massaging all injection sites. For example, it is acceptable to massage the Another technique that can help prevent drug leakage site following an injection of morphine sulfate in order to into the subcutaneous tissue is the Z-track technique. The decrease the patient’s discomfort, but massaging the site after Z-track technique creates an offset injection pathway, using an injection of diazepam would only serve to increase the subcutaneous tissue to block leakage.62 patient’s discomfort. To create a Z-track, the Paramedic with the drug-fi lled Also at issue with the routine practice of massaging an syringe in the dominant hand, bevel up, would pull gentle injection site is its impact on absorption. While intramuscu- traction on the injection site with the nondominant hand. Fre- lar injection of insulin is uncommon, its rate of absorption quently, Paramedics will grasp the upper arm, if the deltoid is quicker via intramuscular injection than subcutaneous is used, and pull traction with the thumb of the nondominant injection. This quality makes intramuscularly injected insu- hand. With a smart fl ick of the wrist, as if one was throwing lin attractive during a diabetic emergency. However, massage a dart, the needle is inserted into the skin. After aspiration of the injection site can dissipate the insulin even further, confi rms proper placement, the drug is injected in a delib- making its uptake more rapid and creating a risk of unan- erate fashion. Injecting the drug too quickly can create dis- ticipated hypoglycemia. If the Paramedic is unsure if mas- comfort as stretch receptors are stimulated by the presence of saging the injection site is acceptable, then the maxim of “do the space-occupying depot of medicine. Alternatively, inject- no harm” should be followed and the injection site should not ing, or “pushing,” the drug too slowly can cause increased be massaged. patient apprehension. Practice establishes the best rate of administration. Special Populations The next actions taken by the Paramedic are critical to The two extremes of age—elderly and children—each present the success of the Z-track technique (Figure 26-14). Before a special challenge for the Paramedic who must perform an the needle is withdrawn from the skin, the Paramedic must injection. Both the patient and the provider alike are anxious release the traction on the skin. Thus, when the needle is during a pediatric injection. To develop strategies to improve completely withdrawn the skin overlying the muscle will slide success, the Paramedic must take into account the child’s over the medication depot, closing it off to the surface. developmental stage and adjust the approach accordingly. 542 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. In many cases, the infant is unaware of the events sur- mass, limiting available injection sites. These emaciated rounding him or her, but is acutely aware of the discomfort patients, with less muscle mass and loss of the capillary beds, that follows. In those cases, it may be acceptable to have the tend to absorb medications less readily. infant held in the mother’s arms to be comforted after the procedure. The greatest challenge may be the toddler. The toddler is keenly aware of his or her environment, is able to com- Street Smart prehend the situation, and receives a great deal of emotional feedback from parents as well as caregivers. Typically, a tod- Uninformed Paramedics mistakenly think it is dler must be temporarily restrained during the injection. One technique is to place the toddler on the parent’s lap, chest to preferable to inject medications below the level chest, with the parent’s arms entrapping the child. The tod- of injury of a paraplegia patient, eliminating the dler’s legs would then be aside and behind the parent. The pain which can accompany an injection. The drug Paramedic would approach the parent from behind, grasp the absorption below the level of the spinal injury is outstretched leg, and perform the injection. The elderly patient presents a challenge of another kind. erratic and unpredictable. The combination of age and poor nutrition reduces muscle Principles of Medication Administration 543 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. The large number of medication administration routes and techniques represent a substantial portion of the universe of skills that a Paramedic must master. Each medication route has its advantages and its drawbacks, its indications and its contraindications. It is the Paramedic’s responsibility to ensure that the patient’s medication needs and the preferred medication route are compatible. Key Points: • It is a Paramedic’s responsibility to choose the in pounds, in half, then subtract 10% off from the right drug and the right dose for the patient, and to result for an approximate weight. administer it by the right route at the right time in order to achieve the optimal therapeutic effect. • A drug concentration is described as the amount of drug in 1 milliliter (mL) of a solution. • Forms of medication can be grossly categorized into liquids, solids, and injectable liquids. • Some prehospital medications must be mixed just before use to ensure maximum effectiveness. • Injectable forms of medication come in either ampoules or vials. Vials are essentially resealable • A standard drug order states the amount of the drug, the name of the drug, and the route that is to ampoules and may be used for multiple patients. be administered. • The apothecary system of measurements includes units of grain (gr) and is rarely used today by • When an adult dose must be adjusted to a pediatric dose, and the pediatric dosing is not available, then physicians. the child’s total body surface area (BSA) is divided • The common household system or United States against the total body surface area of an adult— customary system contains such units as the ounce approximately 1.73 meters squared for a 6-foot and the teaspoon and remains the predominant tall, 150-pound adult. The resulting percentage is system of measurement in the United States and then taken from the adult dose and is roughly equal Canada. to the pediatric dose. |
• The metric system is based in units of 10. • Intravenous fl uids may be infused at a “wide open” rate to administer a large volume of fl uid quickly, • Insulin and penicillin are examples of medications at a prescribed rate per hour or minute, or at a that are measured in international units (IU). KVO rate of 50 mL per hour to keep the catheter This unit represents the relative strength of the patent. substance after it has been tested on an organism. • Methods for determining an intravenous drug • Conversions of metric measurements are based on infusion rate include the formula method and the a factor of 10. All multiplications above 1 gram clock method. are noted in the Greek prefi xes kilo-, hecto-, and deca-, whereas all divisions of a gram are noted by • Weight-dependent intravenous drug infusions the Latin prefi xes deci-, centi-, milli-, and micro-. include the patient’s weight in the standard drug infusion calculation. • The most accurate method of converting a patient’s weight from pounds to kilograms is • To convert Fahrenheit to Celsius (medical standard dividing the patient’s weight in pounds by 2.26 and temperature measurement), the EMS provider obtaining the weight in kilograms. However, the subtracts 32 from the Fahrenheit result and then Paramedic may also divide the patient’s weight, multiplies by 5/9. 544 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. • Paramedics practice the fi ve rights of medication • The vast majority of self-administered medications administration. are swallowed. The solid pill, capsule, or liquid is • then absorbed in the gastrointestinal tract, where After being given any drug, the patient is re- it is passed (via the portal circulation) through evaluated to see if the drug was effective. This the liver and on into the central circulation. From re-evaluation, and subsequent documentation of an EMS perspective, the patient must be able to patient response to medication, is so important that maintain the airway independently and swallow the some Paramedics refer to it as the sixth right, the medication. right documentation. • • Gastric tubes can be placed to instill feedings The initials DARE, a simple mnemonic, can as well as medications in the form of liquids or help Paramedics remember the elements of suspensions. Most Paramedics insert an orogastric documentation for every medication administration. tube in order to evacuate or decompress the • The Paramedic can use the mnemonic AIR to obtain stomach. Use of a special gastric tube, called a an informed consent from a competent patient. Sengstaken-Blakemore tube, permits the Paramedic to apply direct pressure inside the stomach or • Local routes of medication administration are esophagus to the source of bleeding. intended to target a specifi c organ or function. Optic medications are applied directly to the eye, • Intermittent suction or the placement of a dual- and otic medications are applied to the ear. lumen gastric tube helps prevent a gastric tube from adhering to the gastric mucosa, leading • The inner mucosa of the nostrils has a rich capillary to local irritation and bleeding. After the bed that is an excellent route for the administration placement of a gastric tube, the patient should be of systemic medications. Local nasal medications monitored for signs of hypoxia, such as premature can be applied via an atomizer into the intended ventricular contractions (PVC), and altered nostril, propelling the medicine against the mucosa. level of responsiveness. If the gastric tube is Like the nose, the mouth has a capillary-rich obstructed, the Paramedic can irrigate the tube mucosa that will rapidly absorb any medicine and with saline or sterile water instilled into the tube distribute it systemically. via syringe. • Though not widely used, local topical medications may • Drugs that are absorbed from the rectum avoid include the application of a topical antibiotic at the inactivation by stomach acids and intestinal insertion site of an intravenous catheter. Other local enzymes. Around 50% of the absorbed drug bypasses medications can be douches (solutions introduced the portal circulation, minimizing the impacts of into the vagina via an apparatus) or enemas (solutions fi rst pass metabolism and biotransformation. To introduced into the anus via an apparatus). administer the medication, the patient is placed in a modifi ed left lateral position, called the • The enteral route of systemic drug administration Sim’s position. The rectal administration route is refers to medications given via the gastrointestinal useful when the patient is unable to accept oral tract (e.g., oral medications). Parenteral routes of medications, such as in the case of persistent medication administration include inhalation and vomiting or continuous seizures in children. injection. • When a rapid onset of drug action is required • The sublingual route is an enteral route whereby (e.g., during an emergency), the parenteral route medication, in a liquid or solid form, is placed offers the most direct route to the target organs, in the space inferior to the tongue, where it is sidestepping the gastrointestinal system (enteral rapidly absorbed. The distinct advantage to the administration) and delivering drugs directly to sublingual route is that it bypasses the liver and the central circulation. Advantages of these routes thus avoids hepatic fi rst pass metabolism. Using the include circumventing the GI absorption process, buccal route, or cheek, is similar to administering maintaining more predictable serum drug levels, medications sublingually. Principles of Medication Administration 545 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. and using them with patients who are uncooperative the medication depends on the patient’s inspiratory or incapable of cooperation (e.g., unconscious). effort. • Intranasal administration takes advantage of • By suspending the medication in a stream of air, the the nasal passages. They are lined with very small volume nebulizer (SVN) is thought to produce vascular mucous membranes that can absorb a better particle size for inhalation (about 1 to medications quickly and without the risk of fi rst 3 microns). Prior to using an SVN, the Paramedic pass metabolism associated with enteral routes of should conduct a history to determine the patient’s drug administration. The intranasal route works responsiveness to MDI bronchodilators. He should well with patients with altered mental status also perform a physical, auscultating for wheezes or combativeness, and/or when the Paramedic or absent breath sounds. Key to assessing the is in a moving ambulance. Several drugs can be effectiveness of any SVN treatment is the patient’s administered intranasally. The clear advantage of subjective judgment regarding her own dyspnea. For intranasal administration of drugs is the decreased intubated patients, a SVN may be attached in-line risk of accidental needle injury. with the bag-valve-mask assembly. • Naxolone is a drug used for suspected opioid • Topical medication absorption into the overdoses. The use of naxolone intranasally is subcutaneous capillary beds, or transdermal considered “off-label use,” meaning the FDA has medicine, offers a drug administration route not approved the drug for use in this manner. The that can have sustained systemic delivery of a volume administered intranasally should be no medication. Medications given via a transdermal more than 1 mL of liquid, and the drug should be patch can include nicotine, hormone replacement, atomized to a particle size of between 10 mcg and opiate analgesics, and nitroglycerine. 50 mcg, the optimal particle size for absorption. • The components of a hypodermic syringe include • The inhalation of medications is the inhalation of the syringe and the needle, often connected via a drug-laden vapors into the bloodstream via the luer lock or slip-tip adaptor. Syringes are labeled respiratory route. Pulmonary treatments focus on according to the volume within the barrel (e.g., the delivery of respiratory agents directly into the 1, 3, 5 mL) and the calibrations on the side of the pulmonary tree. The common drawback to both barrel. The exception is insulin syringes, which are these methods is the dependence on the patient’s labeled in international units (IU). Surface tension respiratory function. and adhesion of water to the walls of the syringe • form a meniscus. The volume of the drug in the As air enters the lungs, it meets resistance as syringe is determined by comparing the bottom of the structures narrow. The resistance slows the the meniscus with the calibration on the barrel. air down; by the time it reaches the alveoli, it is nearly still. This encourages fallout, as large • The needle is the second component of the particles carried in the air settle out as the velocity hypodermic syringe. Measured in gauges, the is lost. The result is that nearly particulate-free smaller the number means the larger the diameter air enters the alveoli. This works against large of the needle (e.g., 14 gauge > 20 gauge). The droplets of aerosolized medications and reduces the Paramedic should choose a needle size dependent effectiveness of many respiratory drugs. on the viscosity of the fl uid and speed of delivery. • Injecting a drug into a medication port of an The metered dose inhaler (MDI) is a portable and intravenous set, or performing an intramuscular, well-accepted respiratory treatment platform. subcutaneous, or intradermal injection, all require a However, it is relatively ineffective, depositing specifi c size and length needle. less than 20% of the medication in the distal lung fi elds. A spacer device can be used to increase • Retractable needles, self-sheathing needles, MDI’s effectiveness. Dry powder inhalers (DPI) use a needles that have a retractable hard case that pulverized solid drug for inhalation with a delivery is advanced over the needle as the needle is device similar to an MDI. Again, the effectiveness of withdrawn, and hooded needles that have a 546 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. protective covering over the needle are all efforts • Subcutaneous injection of medication is the made through engineering controls to help prevent slowest and least dependable means of obtaining needlestick injury. therapeutic drug levels in the bloodstream. • Acceptable sites for subcutaneous injections It is every Paramedic’s responsibility to safely including the abdomen, the lateral aspects of the dispose of used/contaminated needles into a safe upper arm, and the anterior thigh, as well as the sharps container. The sharps container should be ventrodorsal gluteal area. Frequent subcutaneous close at hand, within arm’s reach, and be easy to injections at one site, such as may occur with access. repeated insulin injections, result in tissue fi brosis. • Medications are packaged in either vials or • Intramuscular injection deposits the drug ampoules. There are prefi lled ampoules/syringe between the layers of the muscle, and below the systems as well as glass ampoules that have to be subcutaneous tissue, providing rapid systemic broken before the medication can be withdrawn. action. Intramuscular injections are contraindicated When withdrawing air from a vial, it is essential that in patients with peripheral vascular disease and the Paramedic fi rst inject air, in equal volume, into disease states which create hypoperfusion (e.g., the vial before withdrawing the medicine to prevent anaphylactic shock). Intramuscular injection is a a vacuum. preferred route for so-called depot medications • There are many routes of injection that deliver deposited under the skin to produce sustained a drug directly into the |
target organ. Indirect therapeutic levels over a longer period of time. parenteral injections are also effective means of • There are four common sites for intramuscular delivering medications. However, the greatest injection. The fi rst site, the ventrogluteal (VG) drawback is its dependence on adequate circulation muscle, is located on the lateral thigh proximal to to reach the target organ. the hip. A more anterior injection site is the middle • Positioning the patient is the fi rst step in portion of the vastus lateralis (VL) muscle of the preparation for an injection. The injection site thigh. Requiring less exposure and easier access is selected should not be hard, swollen, or tender the deltoid muscle. The most common intramuscular and must be free of rashes, moles, birthmarks, injection site is the dorsogluteal (DG) muscle. The burns, scars, or broken skin. The Paramedic should gluteus is located proximal to the inferior portion of place an isopropyl-soaked pad on the site and, the patient’s fl ank. working outward in ever-expanding circles, prepare • EMLA cream, a topical anesthetic, can be used to an area approximately twice the length of the reduce the pain of needle insertion. Fluori-methane needle. The skin is stabilized with the Paramedic’s and vapocoolant spray are also applied directly nondominant hand and, with the needle in the to the skin for anesthetic effects. The deeper dominant hand, the needle is inserted under the muscle layers are relatively free of pain receptors, skin. With the needle in place, the Paramedic would although irritation may occur from a drug if leaked gently aspirate to ensure that the needle was not into subcutaneous tissues. To prevent this, the inadvertently placed into a vein. airlock and Z-track techniques may be used by the • Intradermal injections may be used when preparing Paramedic for intramuscular injections. an intravenous site with a local anesthetic or • The elderly and children each present a special for tuberculosis testing. The objective of an challenge to the Paramedic who must perform an intradermal injection is to place a small quantity injection. To develop strategies to improve success of medicine just under the epidermis and in close of a pediatric injection, the Paramedic must take proximity of the subcutaneous tissue. Point of care into account the child’s developmental stage and blood testing can be performed with blood glucose adjust the approach accordingly. For the elderly, analysis or fi eld troponin levels. A fi nger stick or, the combination of age and poor nutrition reduces for pediatric patients, a heel stick is performed to muscle mass, limiting available injection sites. obtain a small sample of blood for analysis. Principles of Medication Administration 547 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Review Questions: 1. Before administering any medication, what are calculate the number of drops per minute that the six rights a Paramedic is responsible for should be administered. confi rming? 5. Identify and describe the characteristics of solid 2. Explain how medication levels comparable and liquid forms of medication. to venous injection can be provided using 6. Explain why the metric system or SI is used rectally inserted medications for medication calculation as opposed to (e.g., suppositories). household measurements. 3. Defi ne what the international unit (IU) 7. What is the relationship between cubic represents and give two examples of centimeters of water and milliliters of water? medications that are administered using this 8. What complications exist when treating a system of measurement. patient with either an inhaler or nebulized 4. The Paramedic is presented with a patient medication? What can the Paramedic do to who weighs 260 pounds. Medical control overcome these challenges? has ordered that the Paramedic administer 9. Using proper anatomical terminology, describe dopamine 5 mcg/kg/min using a 60 drop the four locations for intramuscular injections. administration set. The Paramedic has one vial 10. Describe the two techniques that have been of dopamine 400 mg in 4 mL and a 250 cc bag developed to decrease the leakage and of normal saline. Write out the formula and discomfort of IM injections. Case Study Questions: Please refer to the Case Study at the beginning of the 3. What are two measures of temperature? chapter and answer the questions below: 4. You have contacted medical control, given 1. What systems of measurement exist? Why are report, and have now been given an order for protocols written in metric measurements? a medication. What are the elements of a drug 2. What are the standard metric units for length, order that should be performed when receiving a volume, and weight? medication order? 548 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. References: 1. Pond SM, Tozer TN. First-pass elimination. Basic concepts and 20. Brimacomb J, Keller C, et al. Reliability of epigastric clinical consequences. Clin Pharmacokinet. 1984;9(1):1–25. auscultation to detect gastric insuffl ation. Br J Anaesth. 2. Foulkes J, Wallace DM. Haemorrhage from stomal varices in an 2002;88(1):127–129. ileal conduit. Br J Urol. 1975;47(6):630. 21. Neumann MJ, Meyer CT, et al. Hold that x-ray: aspirate pH and 3. Flomenbaum N, Goldfrank L, Hoffman R, Howland M, Lewin auscultation prove enteral tube placement. J Clin Gastroenterol. N, Nelson L. Goldfrank’s Toxicologic Emergencies. New York: 1995;20(4):293–295. McGraw-Hill Professional; 2006. 22. Elpern EH, Killeen K, et al. 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Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. 36. Dolovich MA. Infl uence of inspiratory fl ow rate, particle size, 50. Donaldson C, Green J. Using the ventrogluteal site for and airway caliber on aerosolized drug delivery to the lung. intramuscular injections. Nurs Times. 2005;101(16):36–38. Respir Care. 2000;45(6):597–608. 51. Small SP. Preventing sciatic nerve injury from intramuscular 37. Thompson PJ. Drug delivery to the small airways. Am J Respir injections: literature review. J Adv Nurs. 2004;47(3):287–296. Crit Care Med. 1998;157(5 Pt 2):S199–S202. 52. Greenway K. Using the ventrologluteal site for intramuscular 38. Geller DE. Comparing clinical features of the nebulizer, injection. Nurs Stand. 2004;18(25):39–42. metered-dose inhaler, and dry powder inhaler. Respir Care. 53. Zempsky WT, Cravero JP. Relief of pain and anxiety in 2005;50(10):1313–1321; discussion 1321–1322. pediatric patients in emergency medical systems. Pediatrics. 39. Buxton LJ, Baldwin JH, et al. The effi cacy of metered-dose 2004;114(5):1348–1356. inhalers with a spacer device in the pediatric setting. J Am Acad 54. Blouin A, Molez S, et al. A novel procedure for daily Nurse Pract. 2002;14(9):390–397. measurements of hemodynamical, hematological, and 40. De Benedictis FM, Selvaggio D. Use of inhaler devices in biochemical parameters in conscious unrestrained rats. pediatric asthma. Paediatr Drugs. 2003;5(9):629–638. J Pharmacol Toxicol Methods. 2000;44(3):489–505. 41. MacIntyre NR, Cheng KC, et al. Applied PEEP during pressure 55. Yoon WY, Chung SP, et al. Analgesic pretreatment for antibiotic support reduces the inspiratory threshold load of intrinsic PEEP. skin test: vapocoolant spray vs ice cube. Am J Emerg Med. Chest. 1997;111(1):188–193. 2008;26(1):59–61. 42. Wrenn K. The hazards of defi brillation through nitroglycerin 56. Cohen Reis E, Holubkov R. Vapocoolant spray is equally patches. Ann Emerg Med. 1990;19(11):1327–1328. effective as EMLA cream in reducing immunization pain in 43. West K. Infection-control basics. A common sense review for school-aged children. Pediatrics. 1997;100(6):E5. EMS personnel. Jems. 2002;27(5):115–118, 120, 122–125. 57. Williams RH, Nollert MU. Platelet-derived NO slows thrombus 44. Tatelbaum MF. Needlestick safety and prevention act. Pain growth on a collagen type III surface. Thromb J. 2004;2(1):11. Physician. 2001;4(2):193–195. 58. Warren BL. Intramuscular injection angle: evidence for practice? 45. Redd DA, Boudreaux AM, et al. Towards less painful local Nurs Prax N Z. 2002;18(2):42–51. anesthesia. Ala Med. 1990;60(4):18–19. 59. Katsma DL, Katsma R. The myth of the 90 degrees-angle 46. Hildebrandt P. Subcutaneous absorption |
of insulin in insulin- intramuscular injection. Nurse Educ. 2000;25(1):34–37. dependent diabetic patients. Infl uence of species, physico- 60. Petousis-Harris H. Needle angle when giving i.m. vaccinations. chemical properties of insulin and physiological factors. Dan Nurs Prax N Z. 2002;18(2):52–53. Med Bull. 1991;38(4):337–346. 61. Chung JW, Ng WM, et al. An experimental study on the use of 47. Hildebrandt P, Birch K. Basal rate subcutaneous insulin infusion: manual pressure to reduce pain in intramuscular injections. J Clin absorption kinetics and relation to local blood fl ow. Diabet Med. Nurs. 2002;11(4):457–461. 1988;5(5):434–440. 62. Rodger M.A. King L. Drawing up and administering 48. Hildebrandt PR, Vaag AA. Local skin-fold thickness as a clinical intramuscular injections: a review of the literature. J Adv Nurs. predictor of depot size during basal rate infusion of insulin. 2000;31(3):574–582. Diabetes Care. 1993;16(1):1–3. 49. Zaybak A, Gunes UY, et al. Does obesity prevent the needle from reaching muscle in intramuscular injections? J Adv Nurs. 2007;58(6):552–556. 550 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. KEY CONCEPTS: Upon completion of this chapter, it is expected that the reader will understand these following concepts: • Fluid balance • Indications for intravenous access • Method for venipuncture • Complications of intravenous access • Techniques and strategies for pediatric phlebotomy and intravenous access • Alternative access points and central venous access devices Case Study: As the second unit rolled up onto the scene of a two-car MVC, the Paramedics heard from the fi rst unit that they should set up a trauma line for the driver of car #2. She was being extricated now and had signifi cant injuries. Oh, and by the way, the driver was Mrs. Gorino. Everyone knew Mrs. Gorino. She was a pleasant woman who had battled back from breast cancer but needed frequent hospitalizations for a myriad of medical problems. Only the best of the best Paramedics could fi nd IV access on her. 552 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Intravenous Access 553 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. OVERVIEW Intravenous access allows the Paramedic to administer medications and manage a patient’s intravascular volume. To effectively care for the patient, the Paramedic must have a commanding knowledge of the equipment used for intravenous access, as well as complete assessment skills and techniques. By examining the sources of fl uid loss and clinical signs of fl uid displacement, the Paramedic can determine the need for intravenous access and develop an appropriate treatment plan. Needs and skills vary according to age and clinical condition. Intravenous Access Medical lines, sometimes called lifelines, are a means of giving medications directly into the circulation. A number and Paramedics of methods have been devised to gain venous access, yet one The public distinguishes the Paramedic from basic life sup- constant remains for all of them—intravenous access is nec- port providers by the Paramedic’s ability to start intravenous essary for medication administration. access (IV). The public knows that an IV permits the Para- The second indication for intravenous access is trauma. medic to give pain medicine and other life-saving drugs. Blood losses can make the patient who has experienced Perhaps no other ALS skill is practiced as often as intrave- trauma hypovolemic. A trauma line is inserted into the vas- nous access. Therefore, the Paramedic should be an expert at cular space so that intravascular volume can be replaced and establishing intravenous access. homeostasis restored. In some cases, a patient with traumatic injury may need medications. Conversely, a medical patient may experience a signifi cant loss of fl uid and require volume Physiology Review replacement, though there has been no trauma. It is apparent that the divisions are not clean and each type of line is some- The human body is primarily made up of water, about 30 times used for the other purpose. liters of water, which is distributed across three compart- ments. When thinking of body fl uids, the fi rst compartment generally considered is the intravascular space in which the Sources of Fluid Loss blood volume is contained within the arterial, capillary, and Fluid loss, due to either illness or injury, is an indication for venous vessels. However, the bulk of the water is contained intravenous access. By understanding the sources of fl uid within the second compartment, the intracellular compart- loss, the Paramedic can anticipate the need for intravenous ment (ICF), while the remaining volume is contained in the access. Fluid loss is a normal function of the body. Such loss third compartment, the extracellular fl uid (ECF). The extra- may be apparent, such as urination, or may be unsuspected cellular fl uid (ECF) bathes the cells as interstitial fl uid. (insensible). Insensible loss is that volume of fl uid that is The constant ebb and fl ow of these fl uids across these lost from the body in the form of perspiration off the skin three compartments, exchanging gasses, hormones, glucose, (1.1 liters/daily) and the vapor in the breath. Normally, the fatty acids, and wastes, is the basis for nutritional fl ow. Using patient would replace this loss through fl uid intake as well as this nutritional fl ow to an advantage, Paramedics can inject a the water contained in the foodstuffs ingested. concentrated quantity of medication, called a bolus, into the The amount of fl uids normally lost, both sensible and intravascular space and reasonably expect that the medication insensible losses, can be accelerated by disease. Paramed- will make it into the cells of the target organ. ics who are confronted with a patient who has a medical complaint and has signs of hypoperfusion should perform a Medical vs Trauma complete history and physical assessment of the patient to ascertain the source of the fl uid loss as well as ascertain the The rationale for obtaining intravenous access can be grossly degree of hypovolemia. broken down into two categories: medical and trauma. Both A common cause of increased insensible fl uid loss is patient populations undoubtedly need venous access in cases increased perspiration secondary to fevers due to infection.1,2 of emergency, and the risk/benefi t of obtaining an intravenous This loss, combined with the anorexia (lack of appetite) line leans so decidedly toward providing benefi t that Para- that often accompanies a fever, can result in an imbalance medics attempt venous access almost all emergent patients of fl uid intake versus output. Add the vomiting and diarrhea and most urgent patients. What remains undecided is the use which often accompanies many illnesses, and the patient may of intravenous infusions in specifi c cases. quickly develop a signifi cant fl uid imbalance. 554 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. During a 24-hour period, the average person will itself is a diuretic, the impact of liver cirrhosis is probably excrete—and then reabsorb—approximately one-half of her greater upon the patient’s fl uid volume state. When the liver intravascular volume into the lumen of the intestines. This is not producing suffi cient blood proteins, such as albumin, process of excretion and reabsorption of nutrient ladened fl u- secondary to cirrhosis, the colloidal osmotic pressure (COP) ids constitutes nutritional fl ow and is essential to the body’s within the blood falls, and with it the patient’s intravascular sustenance. Any process which interferes with that fl ow can volume. create fl uid imbalances. Hyperglycemia can be another cause of acute fl uid loss. Beyond the fl uid loss that accompanies vomiting and Hyperglycemia, the hallmark of new onset diabetes mellitus, diarrhea, other gastrointestinal problems can create hypo- acts as an osmotic diuretic and draws fl uid from the interstitial volemia secondary to the fl uid loss. For example, a patient space into the central circulation. As this volume increases, with a small bowel obstruction will not be able to reabsorb the kidneys increase urine output to excrete the excess vol- the fl uids in the large bowel as the patient normally would. ume. The patient, whose tissues are now dehydrated, craves Subsequently, the fl uids excreted into the small bowel are water. Despite drinking steadily (polydipsia), the patient can- sequestered behind the obstruction, leading to a distended not take in enough fl uids to offset the excessive output from abdomen. The volume of fl uids is not returned to the central urination (polyuria). circulation as would normally occur. Draining abdominal fi stula, ileostomy, colostomy, and Physical Examination for Dehydration aggressive nasogastric tube suctioning, as well as overuse or misuse of renal diuretics, are other examples of important The patient who has lost signifi cant intravascular volume, sources of fl uid loss. secondary to dehydration, may manifest signs of hypoper- However, it is trauma, with its problematic hemorrhage, fusion which will be evident during the initial assessment. that can cause the quickest fl uid loss. Rupture of solid organs, These signs include decreased level of responsiveness, tac- such as the spleen and liver, following either blunt or pene- hypnea, tachycardia, hypotension, or postural hypotension. trating trauma can quickly create profound hypovolemia. The When these signs culminate to present a clinical picture of Paramedic is well-advised to consider occult trauma when- hypoperfusion, the Paramedic may decide to institute fl uid ever confronted with hypoperfusion of unknown origin. replacement immediately. A number of other signs may precede this presentation and suggest dehydration and impending hypoperfusion. These Past Medical History signs, in a head-to-toe fashion, are lackluster eyes, eyes that A number of pre-existing medical conditions can also contrib- are sunken into their sockets and appear dull. The absence of ute to increased fl uid loss. The following short list of medical tears in a child’s eyes should alert the Paramedic to the pres- conditions can lead to increased and/or excessive fl uid loss ence of dehydration. leading to hypovolemia; this list not all inclusive of medical Dry and cracked lips along with pale mucous membranes conditions that can lead to fl uid loss. in the oropharynx are signs of dehydration. The tongue may Diabetes insipidus, secondary to brain tumor or any other be the best external measure of the patient’s hydration. Nor- space-occupying lesion, can cause life-threatening dehydra- mally, a tongue is plump, and moistened with saliva. How- tion within hours. Diabetes insipidus causes the kidneys to ever, when a patient is dehydrated the tongue becomes dry pass the fi ltrate from the plasma almost unchanged. Normally and furrowed (furrows being long fi ssures |
in the tongue). 99% of this fi ltrate is reabsorbed. Next, the Paramedic should examine the neck, particu- Emphysema, with its accompanying persistent tachy- larly the jugular veins. Some Paramedics regard the jugular pnea, can lead to signifi cant insensible fl uid loss through rapid veins as the “dipstick” of the heart. Under normal condi- respiration. Coupled with the diuretic action of many respira- tions when a patient is lying fl at, the external jugular veins tory drugs such as aminophylline, and without adequate fl uid are at least minimally distended and clearly visible, indicat- replacement, the patient can become markedly dehydrated. ing a suffi cient blood volume. In the case of the patient who Initially, the thought of congestive heart failure summons is dehydrated, the jugular veins will lie fl at against the neck thoughts of fl uid overload, and during an acute exacerbation when the patient lies fl at. this may be the case. However, the combination of forward The next indicator of hydration is the urine output. While failure and subsequent inadequate renal perfusion, coupled not practical in the fi eld, unless the patient has an indwelling with overuse of prescribed diuretics and a constant shifting of urinary catheter, measuring a patient’s hourly urinary output fl uid volumes across all three fl uid compartments, can culmi- is an excellent indicator of vascular volume. When urine out- nate in a complicated clinical picture which can include cel- put drops below 20 mL per hour (oliguria), then the patient lular dehydration, vascular volume depletion, and electrolyte is experiencing signifi cant hypoperfusion of the kidneys, an imbalances. Heart faiulure, therefore, is a problem of fl uid early indicator of shock. maldistribution coupled with interstitial dehydration. In the hospital setting, the gold standard for fl uid bal- Despite an apparent constant intake of fl uids, the alco- ance is the patient’s weight. Even with constant monitoring holic patient is prone to fl uid defi cits as well. While alcohol and recording of intake and output, many critical care units Intravenous Access 555 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. weigh their patients regularly, in some cases daily, in order a secondary intravenous solution, through a primary infusion to monitor fl uid balance. Long-term care facilities also regu- line containing either 0.9% sodium chloride in sterile water larly weigh their patients. (0.9% NaCl) or 5% dextrose in sterile water (D W). 5 The Paramedic who looks for these early signs of dehy- dration and fl uid defi cits will not be surprised when the patient becomes hypotensive. Perhaps more importantly, Street Smart the Paramedic may be able to intervene early and prevent hypotension. A solution of 0.9% sodium chloride in sterile water Intravenous Fluids (0.9% NaCl) contains the same amount of salt as does Intravenous fl uids used for medical patients are intended to the blood. For this reason, many healthcare providers be either intravenous routes for therapeutic medications, or to refer to 0.9% NaCl as normal saline solution (NSS). be therapeutic in and of themselves. Intravenous fl uids used NSS has become an EMS standard solution in many for trauma patients are more often intended to replace lost systems because it is compatible with all medications volume and therefore are therapeutic. In the case of trauma, the optimal fl uid replacement for as well as blood. lost blood would be blood. However, current blood storage requirements and inadequate prehospital equipment make blood replacement in the fi eld impractical. In an effort to Tonicity overcome these obstacles, physicians and scientists are trying A solution is considered balanced if it has the same concentra- to create a variety of blood substitute.To date, trials of these tion of solutes to solvent as there are solutes to solvent pres- blood substitutes are falling short of expectations, but more ent in the blood. Any imbalance of this solute concentration blood substitutes are being researched. would cause an osmotic effect to be created when adminis- These blood substitutes contain proteins, and are thus tered intravenously, potentially overhydrating or dehydrating called a colloid. These colloidial fl uids are capable of both a cell. In other words, tonicity could be thought of as the pulling fl uids from within the interstitial space into the circu- solution’s ability to alter a cell’s internal fl uid balance through lation, to help augment the circulating volume, and remain- osmotic force created by the imbalance between the tonicity ing within the blood stream for a prolonged period of time, of the solution outside of the cell versus the tonicity of the helping to maintain the circulating volume. fl uid within the cell. When the percentage solute in the solu- In the interim, and until these solutions are available, tion is similar to the percentage solute in the blood, such as Paramedics must use electrolyte-containing fl uids during is the case with a balanced solution, the solution is said to trauma resuscitation. These electrolyte solutions, when dehy- be isotonic. Examples of nearly isotonic fl uids include D W, drated, create crystals. Thus, these electrolyte-containing fl u- 5 LR, and NSS. When additional substances or additives are ids are referred to as crystalloids.3-6 added, thus increasing the concentration of the solutes com- The electrolytes commonly found in crystalloid pared to blood, then the solution is said to be hypertonic. s olutions—sodium, chloride, and potassium—are the same Hypertonic solutions will, by osmotic force, draw water out electrolytes found within the blood. In fact, several crystal- of the cell, causing the cell to dehydrate and collapse or cre- loid solutions were created in an effort to reproduce a “blood- nate. Conversely, if pure sterile water, or a solution which like” mixture. British physicist Sidney Ringer was made has fewer solutes than blood, was injected, then the solution famous when he tried to create a “balanced solution” in 1873, would be referred to as a hypotonic solution. Cells would the solution which still bears his name, but was unable to then, by osmotic force, draw water into themselves, expand- bottle the solution because of its effervescence. Improving ing in the process to the point where the cell would burst. on Dr. Ringer’s solution, and solving the problem of effer- Various changes occur when isotonic, hypotonic, and hyper- vescence, Dr. Hartmann added lactate, resulting in lactated tonic solutions are mixed with red blood cells as shown in the Ringer’s solution (LR). Lactated Ringer’s solution remains following fi gure (Figure 27-1). the solution of choice of trauma surgeons (advanced trauma life support, or ATLS) and in the treatment of burn patients (American Burn Foundation or ABF).7–10 Intravenous Fluid Administration When caring for a medical patient, a number of additives Once a solution has been selected, the Paramedic turns his may be added to the solution to provide a therapeutic benefi t. attention to the administration of that fl uid. Intravenous solu- The most common additive is dextrose, a simple sugar which tions come in either plastic containers or, more rarely, glass can be quickly metabolized to meet the ill patient’s higher bottles and in volumes ranging from 25 mL to 3,000 mL. energy demands. Other additives include antibiotics, vaso- Paramedics typically use 250 mL, 500 mL, and 1 L solutions. pressors, antidysrhythmics, and a host of other medications. Glass containers are noncollapsible and must be open to air, Many of these therapeutic solutions are run intermittently, as or vented, to prevent the creation of a vacuum. While plastic 556 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Solute Free water Solute Free water molecule molecule molecule molecule Isotonic environment: The solute concentration and the Hypotonic solution: free water concentration are the same The solute concentration is greater inside and outside the cell. inside the cell; the free water Water flows in and out of the cell at an equal rate. concentration is greater outside. A Free water flows into the cell. B Solute Solute Free water molecule molecule molecule Hypertonic solution: The solute concentration is greater outside the cell; the free water concentration is greater inside. Free water flows out of the cell. C Figure 27-1 (a) Isotonic solution. (b) Hypertonic solution. (c) Hypotonic solution. containers are increasingly more common, glass containers bypasses many of the body’s defenses against infection. are still used for medications which react with or are absorbed Without these protections, the patient’s blood could become into the plastic. IV bags are soft plastic solution containers infected, a condition called septicemia, and the patient could which collapse as the solution is withdrawn, eliminating the develop a potentially life-threatening sepsis. When a Para- need for venting, and create a closed system which helps to medic starts an intravenous access, it is understood that the decrease the risk of outside contamination. Paramedic has the responsibility to take all reasonable pre- A careless infusion of intravenous fl uids can lead to seri- cautions to prevent such an occurrence. ous systemic complications. For example, contaminated intra- There are a number of occasions when the intravenous venous fl uid can lead to septic shock. An intravenous infusion fl uid can become contaminated. The intravenous solution Intravenous Access 557 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. could have become contaminated before the Paramedic han- dled the solution. The container could have been accidentally punctured, or contaminants accidentally introduced along with the additives during the manufacturing process. Under- standing this risk, every manufacturer takes precautions to prevent contamination. However, despite these precautions, contamination can still occur. Most manufacturers will only guarantee a solution’s sterility for a certain period time, a date stamped on the package. Understanding these precautions have already been taken, every Paramedic performs a three-step inspection of the solution before it is opened. After confi rming that the correct solution has been chosen, the Paramedic verifi es that the solution is not expired. The expiration date, stamped or printed on the container, is evidence that the solution is less Figure 27-2 Macro-drop intravenous likely to be contaminated. administration set. Next, the Paramedic examines the solution for clarity. Intravenous solutions are generally clear, with some notable exceptions being medications like diazepam (pale yellow). With the solution held up to a light, the Paramedic should straight line with the fewest obstructions, such as fi lters or inspect the solution for any discoloration or any particulate medication portals, is desirable. These administration sets are matter. If contamination is suspected, then the solution should referred to as macro-drop administration sets (Figure 27-2). be discarded immediately. When careful titration of medicated fl uid is desired (e.g., Finally, the Paramedic should test the container to see if when a medical patient needs a slow infusion of a drug), then it is intact and without microscopic holes that could be por- fi ne control of the infusion stream is needed. These adminis- tals for contamination. A fi rm twist of the bag should reveal tration sets are referred to as micro-drop administration sets. any leaks. If the bag does leak, it should be discarded and Anatomy of an Administration Set another solution chosen. Every administration set has a spike, sometimes called a bayonet, which is used to pierce the fl uid container. As the name implies, the spike |
is very sharp and is as capable of Street Smart cutting fl esh as easily as it is capable of piercing a plastic seal in a bag of intravenous solution. Caution should be observed Some intravenous solutions come with a second when mating the spike of the administration set to the solu- protective outer wrap around the bag. Due to tion bag to prevent inadvertent puncture of the side of the differences in humidity from the site of manufacture solution bag, which can result in a puncture of the Paramed- ic’s fi nger as well. and the present location, condensation may have Below the spike is the drip chamber. Hanging drops are occurred. The Paramedic should fi rst wipe the bag formed inside the drip chamber. These drops can be counted, down and then test the container’s integrity. Follow as drops (gtt) per minute (gtt/min), and the rate of fl ow estab- lished. If the chamber has a thin, or needle, dropper, then the this rule, however: “If in doubt, throw it out.” administration set is called a micro-drop set. By convention, all manufacturers have set 60 drops from a micro-drop set to equal 1 mL. The needle dropper is visible within the drip Administration Sets chamber (Figure 27-3). The next step in preparing to administer an intravenous solu- If the drip chamber does not have a needle dropper, then tion is connecting an administration set to the solution. Dur- the set is called a macro-drop set. Unlike the micro-drop set, ing this procedure, the greatest risk of contamination may macro-drops can vary in size. The variation in the size of the occur. Careful attention to detail is important to prevent drop directly relates to the number of drops per 1 mL. To sterile components from contacting nonsterile surfaces. The determine the drip rate for a particular macro-drop adminis- purpose of an intravenous administration set is to provide a tration set, the Paramedic should refer to the labeling on the sterile pathway for the intravenous fl uid from the container packaging. In some cases, the drip rate is embossed directly into the patient. into the plastic on the spike as well. The selection of an administration set is largely depen- Further down the length of the tubing is a drip rate con- dent upon the patient’s condition. When volume replacement trol device. The drip rate control device allows the Paramedic is needed (e.g., during a trauma resuscitation), then a short, to regulate the fl ow (i.e., the rate of drop formation) so that 558 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Figure 27-3 Micro-drop drip chamber. Figure 27-5 Intravenous administration slide clamp. Figure 27-6 In-line medication port. risk that the venous catheter will become clogged by a blood- clot, rendering it useless. To prevent the catheter from clog- ging, the check valve leaves a standing column of solution in Figure 27-4 Control devices: Roller clamp type. the line. Hard plastic in-line medication ports (Figure 27-6) provide precise volumes can be administered (drops per minute being access for injection of drugs into the solution stream. These equated to mL per hour). Most control devices have either a ports can be either capped with a self-sealing membrane, into roller clamp (Figure 27-4) or screw-type device, both of which which a needle would be inserted, or a needleless check-valve function by compressing the tubing. The roller clamp, a com- system designed to accept a syringe’s luer lock tip. mon control device, has a thumb wheel which compresses the Some intravenous administration sets have a device tubing against a hard plastic back and thus limits fl ow. called a fl ash bulb. The fl ash bulb is a soft in-line pyramid- Another control device, the slide clamp (Figure 27-5), is shaped device. When the tubing is clamped and the fl ash bulb used to cut off fl ow entirely. This is necessary during intrave- is squeezed, a show of blood can be seen in the distal tubing. nous drug boluses to prevent retrograde infusion of the medi- This blood “fl ash” is an indicator that the venous access is still cation into the intravenous tubing rather than into the patient. patent. Some fl ash bulbs are made of self-sealing materials By sliding the tubing into the groove, fl ow is stopped. Similar which permit insert of a needle for injection of medications, to a slide clamp, some administration sets have a squeeze- thus making the fl ash bulb the most proximal medication port clamp which can cut off solution fl ow. to the venous access. Some administration sets come with a mid-line, in-line Some intravenous administration sets also have an in-line check valve designed to prevent the administration set from fi lter. The in-line fi lter is designed to strain the solution for running dry. If an administration set does run dry, there is a large particles of undissolved medication, solution crystals, Intravenous Access 559 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Luer lock and adapter Drip chamber Roller clamp Spike to attatch to intravenous fluid bag Medication administration Tubing Slide clamp port Figure 27-7 Anatomy of an intravenous administration set. Figure 27-8 Trauma tubing. (Courtesy of Arrow International) contaminants, and the like. Disk-like in appearance, these in- line fi lters are usually found proximal to the drip chamber but distal to any medication ports. The place where the administration set inserts into the hub of the venous catheter is called the adaptor. The adaptor is ster- ile where it couples with the catheter hub and a cap is in place over the adaptor to prevent contamination. In some cases, the impervious hard plastic adaptor must be removed in order to allow the solution to be run through the administration set prior to insertion. In those cases, the cap must be retained to re-cover the sterile adaptor once the solution has been run out in order to maintain the sterility of the adaptor. Other adaptors have a semi-porous cap which permits fl uid to run out through the cap without compromising sterility (Figure 27-7). Street Smart Figure 27-9 Pressure bag. When the adaptor’s cap is misplaced, the administration set can be capped with a spare covered Trauma tubing generally has a larger internal diameter, or sterile needle. The diameter of the hub and a needle bore, than standard tubing (Figure 27-8). The combination of are the same. When the administration set is to be a short length and large bore allows the rapid administration of attached to the hub of the venous catheter, the large volumes of solution.15,16 This administration is so rapid, needle is then discarded into a sharps container. in fact, that some trauma tubing sets are also Y-sets, meaning that they have two fl uid connections, each with a spike. This allows two bags of solution to be hung at one time. The addition of a pressure bag can also increase the rate Trauma Tubing of fl ow and decrease the time to infuse a liter of solution. A Factors that infl uence the rate of fl ow for an administration pressure bag is a sleeve with a bladder device. The solution is set are the length of the tubing, the height of the solution bag, placed within the sleeve and the bladder exerts direct pressure and the diameter of the tubing.11–14 Tubing length may have onto the solution bag. The increased pressure subsequently the greatest impact on fl ow rates. Whenever fl uids run down increases the rate of fl ow. Infl ated in the same manner as a a tube, the fl uid strikes the walls of the tubing, creating tur- blood pressure cuff using a bulb with relief screw, a pressure bulence, and the turbulence slows the speed of the fl uid. This bag is infl ated to a preset pressure, visible on the gauge, or phenomenon is called friction loss. The longer the tubing, the until a pressure relief valve activates (Figure 27-9). greater the friction loss, and the slower the fl ow of the solu- Whenever there is a large volume of fl uid to be adminis- tion. For this reason, trauma tubing is generally short in order tered, there is the concomitant risk of inducing hypothermia to facilitate a rapid fl ow of solution into the patient. via infusion of less-than-body-temperature solutions. To 560 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. prevent this predictable complication, special warmth- The volume to be infused in children must be carefully preserving solution sleeves are available (Figure 27-10). These controlled to prevent any incidence of fl uid overload. For sleeves have one pocket for a hot pack and another for the pediatric infusions, a special in-line burette may be added. solution. There is insulation around both to prevent heat loss. A burette has another fl uid chamber above the micro-drop drip chamber. The fi rst chamber is prefi lled with a specifi ed Blood Transfusion Sets volume of fl uid from the solution bag and then the infusion Blood’s viscous nature makes it diffi cult to fl ow and thus rate is adjusted. The solution chamber of the burette is rigid; special large-bore tubing has been created for the transfusion for this reason, it has a vent to equalize pressures. Burettes of blood. Blood tubing also has a large drip chamber with a also have a built-in check valve to prevent the administration sieve-like fi lter at the bottom which prevents clots from being set from running dry. transfused (Figure 27-11). Frequently, an infusion of NSS is When it is necessary to infuse a second bag of solution also co-administered with the blood. The NSS helps to thin (e.g., a medicated solution) and only one venous access is the blood and keep the blood running freely. available, a secondary set can be set up to run through the In special cases, it is desirable to add another drug port primary administration set. This arrangement has several for concomitant drug infusions, or an additional length of advantages. It prevents the need to establish a second venous tubing to the administration set. Optional extension sets are access, which is especially important in venous-impoverished available for this purpose. The extension set connects with patients. It permits continuous hydration between intermit- the adaptor of the administration set and is connected to the tent drug infusions, such as antibiotics. Finally, it permits a venous catheter. secondary drug infusion (e.g., an antidysrhythmia drug) to be temporarily discontinued so that a potentially incompatible drug can be injected through the primary administration set after the tubing is cleared of drug by a fl uid bolus. A descrip- tion of the preparation and use of a secondary set follows later in this chapter. Preparing the Intravenous Administration Set Preparation of an intravenous administration set is done in a deliberate stepwise fashion and after practice becomes almost second nature. However, a moment of inattention to the details can set up a situation that is problematic later. After removing the chosen intravenous administration set from the packaging, taking care to not let any part of the set to drop onto the ground, the Paramedic |
should inspect the set for all of the needed components. For example, if it is anticipated that a medication will be given by injection, Figure 27-10 Intravenous solution warming then a medication port as well as a clamp should be available. sleeve. Administration sets vary and not all components are present on every set. In the next step in the preparation of an administra- tion set, the Paramedic would slide the fl ow rate control device proximal to the drip chamber and clamp the tubing closed. Clamping the tubing shut prevents premature drain- age of the drip chamber. It also places the roller clamp at eye level when the solution is suspended, or hung, and thus permits better eye-to-hand control when adjusting the fl ow rate later. The Paramedic would then set the intravenous admin- istration set aside so that the solution can be prepared. After the Paramedic has ensured that the chosen solu- tion is the correct solution, the solution is not expired, the solution is not contaminated, and the container is intact, the protective covering over the solution’s admin- istration set port can be removed. Some intravenous solu- Figure 27-11 Blood transfusion set. tions come with a medication administration port, used to Intravenous Access 561 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. inject medications into the solution, which is adjacent to In many cases, there is an impervious cap over the admin- the administration set port. If the self-sealing membrane istration set adaptor which must be removed before fl ow will covering the medication administration port is inadver- begin. The Paramedic should carefully place the cap aside, tently removed, the entire contents of the intravenous bag remembering where it was placed, so it can be replaced later. will flow out. Therefore the Paramedic should carefully After the intravenous administration tubing is cleared of choose the correct port. any air and fl uid runs freely from the end, a process called The Paramedic would then pick up the intravenous admin- running the line out, the tubing is clamped and set aside until istration set and remove the protective cover from the spike. after the venous access has been obtained. The Paramedic Carefully aligning the administration set’s spike in line with should ensure that the sterility of the solution is maintained the administration set port, the Paramedic would carefully slide by recapping the end of the administration set and keeping the the spike into the port. When the Paramedic feels resistance tubing from touching the ground. To help ensure the steril- to the spike, a one-half twist of the spike will effectively open ity of the administration set and solution, some roller clamps the administration set port by coring the membrane sealing the have a built-in clip on the roller clamp. The adaptor is simply solution and will seat the spike fi rmly into the administration set slipped into the clip and clamped into place (Skill 27-1). port. Caution should be observed when connecting the intrave- For a step-by-step demonstration of Preparation of an nous solution to the administration set. First, the administration Intravenous Adminsitration Set, please refer to Skill set’s spike is sterile. Contact with the outside of the solution’s 27-1 on page 586. administration port, the Paramedic’s fi ngers, or any other non- sterile surface will contaminate the administration set. If this occurs, then another administration set must be used. Second, Intravenous Access the spike is capable of breaching the sidewall of the administra- Venous access is an assured means of getting drugs into the tion port and piercing the Paramedic’s gloved hand. Firm con- central circulation so that they can go to the target organs and trol and deliberate action can usually avert this problem. exert their intended therapeutic effect. The speed at which a With the administration set in place and the solution held drug can be delivered to the target and confi dence that the upright so that the drip chamber is at eye level, the Paramedic dose delivered will attain the therapeutic window has made would then squeeze the drip chamber and release. If the spike venous access the preferred route for medication administra- is properly set, fl uid will start to fl ow. If there is no fl ow, then tion during an emergency. the Paramedic should advance the spike further into the solu- Emergency venous access can be divided into two types: tion bag and re-attempt the maneuver until successful. A peripheral venous access and central venous access. Periph- one-half-full drip chamber is optimal. The Paramedic should eral venous access has the advantage of ready availability. continue to squeeze the drip chamber until it is one-half full. Peripheral venous access is also compressible in the event An overfull drip chamber is not acceptable, as it does that the venous cannulation attempt is unsuccessful and not allow the Paramedic to see the drops as they form on bleeding occurs. Unfortunately, a number of circumstances, the needle. If the drip chamber is inadvertently overfi lled, the such as cardiovascular collapse during a cardiac arrest, can Paramedic would invert the solution bag and squeeze the drip make peripheral venous access more diffi cult to obtain. chamber again, replacing the solution back into the bag. Central venous access, on the other hand, uses the larger Failure to fi ll the drip chamber is also problematic. If the veins located deep inside the body. The high rate of blood fl ow drip chamber is open when the solution starts to fl ow, the stream in these veins permits drugs that are normally incompatible will entrain air into the solution and the entrained air be seen to be given sequentially and nearly simultaneously. Perhaps along the length of the tubing. While a small number of air more importantly, these large veins are still accessible, even bubbles is generally not harmful to the patient, a larger volume during times of cardiovascular collapse. Unfortunately, these of air could potentially create an air embolism. If air should veins often run parallel and proximal to arteries and nerves, accidentally get into the solution stream, as evidenced by bub- as well as adjunct to several major organs. Inadvertent arterial bles along the length of the tubing, the Paramedic should pull access, nerve damage, and organ damage are attendant risks the tubing taut and gently snap the tubing to dislodge the bub- with central venous access.17–19 For example, a pneumothorax bles, which should then fl oat upward into the drip chamber. is a predictable complication of central venous cannulation of With the drip chamber one-half full, the Paramedic releases the subclavian vein. While central venous access is practiced the clamp and allows solution to fi ll the tubing. If the stream in the fi eld by some Paramedics, the majority of venous access is too fast, then turbulence in the drip chamber will entrain air obtained by Paramedics is peripheral venous access. The fol- into the tubing where it will adhere to the tubing walls. A slow lowing sections discuss the details of obtaining peripheral steady stream of solution clears the tubing of air and prevents venous access and accessing central venous devices. air bubbles from forming along the tubing’s walls. If after releasing the clamp there is no fl ow, then the Paramedic should examine the length of the tubing, starting Peripheral Venous Access Devices at the drip chamber, for a closed slide clamp or other signs of Early intravenous access devices were large hollow-bore obstruction of the tubing. straight needles which were placed, whole-length, into a 562 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. vein. These early needles had to be sharpened by hand on The tip of the needle (small portion lies exposed at the a stone and then sterilized overnight in an autoclave for end of the plastic catheter) has a short bevel tip which permits surgery the next day. Current venous access devices can be easy penetration of the skin while lessening the chance of either metal or plastic and are sterilized when they are pack- accidental puncture of the distal wall of the vein. The length aged. Manufactured with precision machines to exacting of the needle and catheter, like the hypodermic needle, is standards, these catheters are extremely sharp and come in a dependent on the size of the patient. Pediatric IVs may be 1/2 variety of sizes. to 1 inch long, while the average adult IV is 1 1/2 inches long. The size of an intravenous needle is measured as a Extra long needles, 3 to 4 inches long, are used for special gauge—the smaller the gauge, then the larger the needle. populations of patients such as the patient with severe burns Typical intravenous needles start at 12 gauge and go down to (where subcutaneous swelling can literally pull an IV out) 24 gauge. The selection of the gauge, as well as the selection and obese patients. of the intravenous administration set, depends on its intended Butterfl y IV catheters, a throwback to the days of steel use. A larger needle is preferred for trauma patients in that it needles, are still used for pediatric patients. These shorter can be anticipated that either viscous blood or large volumes steel needles are embedded into a plastic anchor device of crystalloids will be infused. Blood transfused through a which has wings, like a butterfl y. Grasping the wings permits smaller gauge needle (less than 18 gauge) can cause physical the Paramedic better control of the needle during insertion, destruction (lysis) of red blood cells.20, 21 as well as a fi rm surface to anchor the device against the skin Smaller gauge needles (e.g., a 20 gauge needle) are pref- when securing the device in place. This makes them popular erable if the Paramedic anticipates the venous access will for use in the pediatric population. be maintained for a longer period of time. A smaller gauge The third venous access device is the needle-over-the- needle decreases the incidence of thrombophlebitis. Throm- catheter device. These devices are used almost exclusively for bophlebitis occurs more readily in veins cannulated with a central venous access, in part because there are more steps to large-bore needle than a small-bore needle because the large- perform during insertion; the Seldinger technique. Use of the bore needle occupies more of the lumen of the vein, slow- needle-over-the-catheter device is discussed further in a later ing blood fl ow, and creating optimal conditions for platelet section on central venous access. aggregation, the nadir for a thrombus. Needle Safety Categories of Venous Access Devices Accidental needlestick injuries present the Paramedic with the The most widely used intravenous (IV) access devices are the greatest risk for an occupational exposure to HIV and other catheter over the needle devices (Figure 27-12). Individually blood-borne pathogens.22 IV catheter manufacturers have packaged, with a large number of gauges and lengths avail- developed a number of “engineered” safety features which able for selection, these IV devices are easy to insert. appear in newer IV catheters, in an effort to decrease the inci- The heart of a catheter-over-the-needle IV device is the dence of preventable needlestick injuries. Paramedics should needle. The hollow-bored needle acts as a rigid introducer make use of this available safety technology ( Figure 27-13). into the vein and allows blood to backup into the needle Whenever an intravenous access is attempted, a sharps con- to become visible to the Paramedic. The catheter-over-the- tainer should be immediately available (i.e., within arm’s needle device allows the Paramedic to thread the plastic cath- reach of |
the Paramedic). eter over the needle and into the vein. When the insertion is complete, the metal needle is withdrawn—all that remains inside the vein is the plastic catheter. Street Smart The phrase “Use and drop” refers to the process of using a needle (IV catheter, IM or SQ needle) and being able to immediately drop it into the sharps container without taking a step away from the patient or turning away from the patient. Peripheral Site Selection While any vein in an extremity is considered a peripheral vein, certain veins have more desirable qualities than others. Figure 27-12 Catheter-over-the-needle devices. These veins are preferred by Paramedics for venous access. Intravenous Access 563 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Figure 27-13 Engineered safety catheter. The following text describes the steps taken to obtain intra- venous access. While it is easy to see some surface veins, deeper and less visible veins may be more desirable. These deeper veins are anchored in subcutaneous fat, helping to stabilize Figure 27-14 Gaining access in the axillary them and prevent them from moving, or rolling, away from vein. the needle. They are also generally larger in diameter. To distend these veins, making them easier to either visual- ize or palpate, a venous tourniquet is applied.23 A venous tourniquet is made of a soft, wide material which can apply a constricting force around the circumference of a limb. Examples of materials used for a tourniquet include leather straps, blood pressure cuffs, and rubber strips. A popular tourniquet is a length of penrose drain. A penrose drain is a tubular rubber hose which lies fl at and provides a wide band of compression. The tourniquet is typically placed around the arm, either above the elbow or above the wrist, and then tied into a slip knot, with the knot on the medial surface. Next, the distal pulse is palpated. A distal arterial pulse should remain pal- pable at all times and the limb should not become cyanotic. If the pulse is obliterated and/or the patient’s limb becomes cyanotic, then the tourniquet should be immediately removed. Figure 27-15 Gaining IV access in a potentially As a general rule, a venous tourniquet should not remain in violent patient using the basilic vein. place for more than a few minutes. In most cases, the Para- medic can accomplish all of the tasks needed to obtain venous access within that time period. The next vein, the basilic vein, runs down the dorsal After a moment, the veins will start to distend and aspect of the arm and ends at the medial wrist. The basilic become more visible. Starting proximal and moving distal, vein is particularly advantageous when trying to start an IV the Paramedic should be able to identify the following veins: on a confused or combative patient. The Paramedic would axillary, basilic, cephalic, and dorsal arch. position himself at the head of the stretcher and pull the The axillary vein (Figure 27-14) runs from the shoulder patient’s arm toward him. With the arm bent at the elbow, the over the biceps toward the elbow. This vein is more prominent arm can essentially be locked into position, permitting unim- in thin people and those who do considerable lifting for a peded access to the vein (Figure 27-15). living. The advantage of the axillary vein is two-fold. One is The vein running down the forearm, immediately oppo- its proximity to the trunk. This is particularly advantageous site the basilic, is the cephalic vein. The cephalic vein runs when administering certain medications, such as adenosine. down the lateral aspect of the forearm and terminates proxi- The axillary vein also has fewer valves than other more distal mal to the thumb. The distal portion of the cephalic vein is veins, making it easier to cannulate. most commonly used by Paramedics (Figure 27-16). 564 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Figure 27-17 Gaining IV access in the dorsal arch. Figure 27-16 Gaining IV access in the cephalic vein. To stabilize the cephalic vein, the Paramedic takes the patient’s hand as if shaking hands. With a fi rm grasp of the hand, the Paramedic palpates for a void at the distal forearm called the autonomic sniff box. The cephalic vein generally lies within the autonomic sniff box. The most distal peripheral veins of the arm are part of the dorsal venous plexus, a group of veins that originate between each digit and from an arch across the dorsum of the hand. Figure 27-18 Gaining IV access in the external While the veins of the dorsal arch are generally the most visi- jugular vein. ble, making them appear attractive to Paramedics, they contain a number of valves and tend to be somewhat torturous. If an the intended insertion side, the external jugular vein should IV is to be attempted here, a short 1-inch needle is preferred. be clearly visible. The EJV starts proximal to the angle of the To start an IV in the dorsal arch of the hand, the Paramedic jaw and inferior to the ear and then takes a relatively straight should fi rst grasp the fi ngers and bend them inward toward the course toward the mid-clavicular line (Figure 27-18). palm. With the fi ngers stabilized by the thumb, the Paramedic The saphenous vein, often overlooked by Paramedics, can proceed with insertion of the IV (Figure 27-17). Gener- provides an excellent point for venous access when the upper ally, the plane of the insertion of the needle is sharper as the extremities are not available, perhaps due to burns or fractures, veins of the hand are more superfi cial. for example.26, 27 The long saphenous vein, one of two superfi cial Although the external jugular vein (EJV), strictly speak- veins in the leg, is the longest vein in the body, stretching from ing, is not a peripheral venous access, it is treated as such by the groin to the foot. The short saphenous vein extends from the many Paramedics because it can be easily visualized, readily top of the foot, proximal to the outer or lateral malleolus, then palpated, and more importantly, it is compressible if extravasa- runs alongside it, then crosses the Achilles tendon to end in the tion should occur. Because of its location, the actual method of middle of the back of the knee and connects with the popliteal preparing the site for insertion of an IV device is slightly differ- vein. Both saphenous veins communicate with deeper veins via ent. To identify the external jugular vein, the patient should be bridging veins called perforators, which literally perforate the placed in a supine position to maximize venous return.24,25 fascia of the muscle bundles to connect with the deeper veins. While it would be impractical to apply a tourniquet This unique aspect of the saphenous vein permits drugs given around a patient’s neck, it is possible to compress (tampon- via this route to gain rapid access to the larger veins of the legs. ade) the vein by applying a thumb to the distal portion of Some patients, particularly patients with diabetes, have the external jugular vein just superior to the clavicle, at the poor circulation in the lower extremities. This poor circula- mid-clavicular line. By turning the patient’s head away from tion tends to retard healing of a wound. Therefore, Paramedics Intravenous Access 565 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. generally avoid starting an IV in the foot if the patient is Diffi cult Venous Access known to have diabetes or poor circulation in the extremi- Patients who are elderly, who have undergone chemotherapy, ties (peripheral vascular insuffi ciency). Other signs of poor who have a poor nutritional status, or who are obese, plus a circulation in the feet include misshapen toenails and distal number of other medical conditions, may have a poverty of cyanosis of the toes when dependent. visible peripheral veins. These patients present a special chal- lenge to the Paramedic. To improve venous fi lling of the peripheral veins, it is Street Smart important to maintain the limb in the dependent position, below the heart. Elevating the limb to “eye level,” instead of Knowing the exact peripheral venous anatomy is kneeling next to the patient, will quickly drain the limb and advantageous to the Paramedic confronted with a the venous distention will be gone. Some Paramedics advocate applying a warm wrap patient who is in cardiovascular collapse or arrest when around the dependent limb approximately 10 minutes before the veins are not visible. By starting distal and working the IV access is to be attempted. This technique is accept- proximal, the Paramedic can make a series of calculated able, but caution is advised when applying heat to the skin of “blind sticks” in an effort to secure venous access for the elderly patient or those with impaired sensation. Uninten- tional burns can occur due to the application of heat pads. the administration of potentially life-saving drugs. Indirect (tangential) lighting from a fl ashlight held to the side of the patient’s arm may also improve venous visibility. The basilic vein, the cephalic vein, and several bridging veins However, the best results are obtained when the Paramedic between the basilic and the cephalic veins, including the cubital has an understanding of peripheral venous anatomy combined vein, exist in the area of the anterior elbow, called the antecubital with gentle palpation of the forearm to detect deeper veins. fossa (AC). Some Paramedics prefer to obtain venous access in When a vein is palpated under the skin, it should rebound this area, perhaps because of their experience of having observed (i.e., feel spongy). If the Paramedic is unsure if the structure test blood drawn (phlebotomy) from the area. The decision to palpated is a tendon or vein, then she should ask the patient attempt an IV access in the antecubital fossa should be made only to move the extremity through a slight range of motion while after careful considerations of the risks. The antecubital fossa is palpating. Tendons will move with the motion whereas the a part of the elbow joint. Intravenous access obtained proximate vein will not. to the elbow joint risks being dislodged if the patient should sud- Every vein should be palpated to ensure that the vein is denly bend the joint or move the arm. To prevent this occurrence, not an artery. In low output states (i.e., hypoperfusion), it may it may be necessary to restrict the patient’s movements by secur- be diffi cult to distinguish an artery from a vein. To compli- ing the arm to a rigid armboard. cate matters, some arteries, nerves, and veins run together as To complicate matters, the median nerve, the brachial a bundle deeper in the extremity and proximal to bone. In the artery, the radial bone, the ulna bone, the humerus bone, the circumstance that an artery is accidentally cannulated, blood basilic vein, and the cephalic vein, plus numerous muscles, ten- may rapidly back up the administration set and pulsations dons, and ligaments, cross through or terminate in the elbow.28, 29 may be visible in the column of blood. In those cases, the Accidental infi ltration |
of an IV that contains hyperosmolar or catheter should be removed immediately and a direct pres- caustic chemicals (e.g., dextrose 50% or dopamine) for exam- sure applied to the arterial puncture site (Skill 27-2). ple, can create tissue ischemia and necrosis of structures within For a step-by-step demonstration of Venous the elbow, possibly leading to permanent disability. Cannulation Using a Catheter-Over-the-Needle Device, please refer to Skill 27-2 on pages 587–588. Street Smart Venous Site Precautions During a cardiac arrest, the veins of the antecubital During an emergency, any venous access is acceptable, how- fossa may represent the Paramedic’s best opportunity ever, when time permits, and under special circumstances, the Paramedic should carefully consider the alternative IV to obtain IV access during the emergency. The diffi culty access sites. For example, if the patient is suspected of hav- arises when the Paramedic has to distinguish an artery ing an acute myocardial infarction, then attempts to obtain IV from a vein. To avoid accidental arterial puncture, access in the right antecubital fossa are reserved until last. The Paramedics routinely attempt the IV access on the right AC is a preferred access site for interventional cardiac procedures, such as angiocatheterization and angioplasty. lateral side, opposite of the location of the brachial As a courtesy to the patient, it is preferred that the IV site artery on the medial side of the antecubital fossa. selected be on the nondominant arm. This allows the patient greater fl exibility and movement, including the ability to 566 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. attend to the activities of daily living (ADL) such as sign- Site Preparation and Disinfection ing admission papers. To quickly ascertain the nondominant Properly preparing the patient prior to placement of the hand, the Paramedic should look for a wristwatch. In most peripheral catheter will help to ensure success. The patient cases, the patient will wear the watch on the nondominant should be assisted to a comfortable position (such as semi- hand. If the watch must be removed to obtain an IV access or Fowler’s, if possible) and an informed consent obtained for to prevent damage to the watch, the Paramedic should make a the IV insertion using the AIR mnemonic. The patient’s arm notation on the patient care report (PCR) including a notation should be removed from his shirt sleeve, or, if practical, the as to whom the watch was given. patient should be instructed to put on a gown. A moment of Several medical conditions, such as long bone fractures, preparation prevents having to “string” the IV solution and burns, and breast cancer, preclude the Paramedic from start- administration set through the patient’s clothing in order to put ing an IV on an affected limb, except under extraordinary on a hospital gown upon arrival at the emergency department circumstances. The Paramedic should make careful note of and risk accidentally dislodging the IV access in the process. these conditions and avoid starting an IV on the affected limb Next, the Paramedic should apply the tourniquet. After if at all possible. applying the tourniquet, the Paramedic should carefully con- The presence of an armboard to stabilize a fracture may sider potential sites for IV access and select a primary site as be seen as an invitation to start an IV on the immobilized well as a secondary site. Then, with the necessary supplies limb. However, the circulation surrounding a bone fracture assembled, including a padded arm splint if the IV access is may be disrupted and infi ltration of intravenous solutions into going to be near a joint, the Paramedic is ready to prepare the the injury may further complicate the patient’s care. There- area. The following procedure is recommended; however, dif- fore, IVs are generally not started on injured limbs. ferent systems have different approaches to IV site prepara- Burns represent another relative contraindication to an tion, so local/regional procedures should be followed. IV access. Whenever alternative access sites are available, the After opening an isopropyl alcohol-soaked gauze (i.e., a Paramedic is encouraged to use them. However, if the patient prep pad), the Paramedic liberally swabs the area, removing has sustained massive burns, and no other sites are available, gross surface contaminates and skin oils. The prep pad is placed some burn authorities advocate starting the IV through the burn exactly where the IV access will be attempted and moved out- tissue. ward in ever-widening circles. The purpose of this fi rst wash is When an intravenous solution is infused, it remains in to remove sweat, dirt, and oils that could undermine the dressing. the circulation until a number of factors, such as decreased Therefore, the area cleansed should be liberal, approximately the colloidal osmotic pressure, combine to create a mismatch same area to be covered by the dressing, bandage, and tape. between the actual tonicity of the patient’s blood and the It is diffi cult to get tape to adhere to the grossly diaphoretic tonicity of the intravenous solution and cause it to shift into patient. One tactic is to apply tincture of benzoin to help the the third space, the interstitial fl uid. For example, it has been dressing remain fast. After placing a small quantity of tincture estimated that NSS only remains in the bloodstream for about 20 to 30 minutes before it “leaks” into the tissues.30, 31 of benzoin on a gauze pad, the Paramedic swabs the area around Thus the perimeter of the IV insertion site. It is important to not swab intravenous infusions can create an increase in interstitial the insertion site directly, as benzoin is not an astringent. After fl uid. Normally, the body’s lymphatic system would help to the benzoin has dried, the tape/dressing can be applied. drain the excess interstitial fl uid out of the tissues, and back in the central circulation, bringing the body’s fl uids back into balance. However, patients with breast cancer frequently Professional Paramedic undergo a procedure called an axillary lymph node dissec- tion, as a part of a diagnostic or therapeutic intervention for the cancer. These patients may no longer be able to drain the Some jurisdictions allow Paramedics to draw a blood excess fl uid from the affected limb, and a condition called alcohol sample for law enforcement offi cers (LEO), lymphedema sets into the affected limb. Lymphedema, provided there is patient consent. In this situation, unchecked, can cause swelling of the limb, compression of nerves, and paralysis. For this reason, Paramedics avoid the Paramedic should use povidone only to prepare starting an IV on the same side as the axillary lymph node the venipuncture site to avoid claims of contamination dissection.32–34 Frequently, these patients have been educated of the sample with the isopropyl alcohol used in the to warn Paramedics about starting an IV, or taking blood pressures, on the affected side, and many wear medical alert wipes. The Paramedic should document the use of bracelets warning that the patient has lymphedema. If the povidone only on his chart. patient is unconscious and has had a mastectomy, or is wear- ing a compression stocking on the arm, or there is surgical scar in the axilla, then the Paramedic should assume that an A germicidal wash follows, such as povidone-iodine-based solu- axillary lymph node dissection has taken place and choose tions (Betadine®), and is applied in the same fashion as the pre- another site for venous access. vious wash, starting at the intended insertion site and sweeping Intravenous Access 567 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. outward in expanding and ever-widening circles. Regardless of the IV needle. The IV needle and catheter should be exam- whether the Paramedic is using a prep pad or a swab for the ger- ined for any burrs which could cause the patient pain. Under micidal wash, the wipe should never re-cross an already washed no circumstances should the catheter be slid up and down the area. The Paramedic is attempting to create a mini-sterile fi eld. needle. Sliding the catheter over the needle in this fashion The area of the circular sterile fi eld should minimally be twice risks shearing the end of the catheter and creating a catheter the length of the IV needle—one length under the IV needle embolism. However, it is not uncommon to rotate the cath- as it approaches the insertion site and another length for the eter around the shaft of the needle to ensure its easy removal distance under the skin where the IV needle will be lodged. The from the needle. Satisfi ed that the IV needle and catheter are germicidal solution should be allowed to dry. This will allow for acceptable, the Paramedic would grasp the IV needle between the maximum germicidal effect. the thumb and forefi nger and approach the selected site. Paramedics can gently palpate the site before the site Some Paramedics use the nondominant hand to grasp preparation, to help identify a viable vein. However, the Para- the skin below the IV site, applying gentle stabilization to medic should not re-palpate the intended IV access site once the vein with the thumb. This helps to prevent the vein from the site preparation has begun. Placing a gloved fi nger on a moving under the skin (i.e., rolling). Rolling veins are more sterile fi eld contaminates the fi eld, forcing the Paramedic to common in the elderly who have less subcutaneous fat and re-cleanse the area. collagen to help stabilize the vein. Other Paramedics prefer to use the nondominant hand to stabilize the limb, encircling the limb with the Paramedic’s own hand below the site. If the Street Smart patient should suddenly try to pull the limb away, once the IV needle has been inserted, the Paramedic can help hold the limb in place while trying to calm the patient. This approach If the patient is sensitive, or allergic, to povidone- is particularly useful in children. iodine-based solutions, then the Paramedic should With the IV needle poised above the intended venous only use an isopropyl alcohol-soaked gauze to cleanse access point, the Paramedic can take one of two approaches for venous cannulation, the process of threading a catheter the site. When practical, alcohol-soaked gauze should into a vein. The fi rst approach is a direct in-line approach in be placed on the site and allowed to remain in place which the IV needle immediately enters the vein. The alterna- until the Paramedic is ready to insert the IV needle. tive approach is the indirect approach. With the indirect approach, the Paramedic inserts the IV needle under the skin and next to the vein. Once the needle is under the skin and next to the vein, the Paramedic changes the line of approach and enters the vein. The indirect approach is Professional Paramedic useful in people with thicker skin as well as children who are likely to fl inch. After the needle has pierced the skin, the Many hospital IV teams use a chlorhexidine Paramedic can pause, allowing the patient to recover from isopropyl alcohol-soaked swab for IV access the pain before proceeding. The indirect approach also helps decrease the incidence of “overdrive,” an accidental through preparation. These are more expensive than plain and through venous puncture. The indirect approach is some- alcohol and povidone-iodine but may offer improved times preferred by less-experienced Paramedics who are try- bacteriocidal effects. The professional Paramedic will ing to gain practice experience. monitor the literature in order to promote evidence- With the direct approach, the IV needle is placed imme- diately atop the vein. |
With the bevel of the IV needle facing based practice for his/her agency. up, the IV needle is inserted at an approximately 45-degree angle. When the IV needle is in contact with the vein, the Paramedic may feel a slight resistance to forward motion. Using a new alcohol prep pad for this fi nal step, the Para- When this resistance is overcome, some Paramedics refer to medic sets the alcohol prep pad on the insertion site and swipes this as the “pop.” This indicates the needle is in the lumen of distally, removing some of the dried povidone-iodine solution the vein and a blood fl ash should be observed distal to the from the skin; if an alternative germicidal solution was used needle hub. Absence of blood in the needle and catheter (the then this step is unnecessary. The vein should now be visible fl ash) implies that the IV is not in the vein. underneath the skin. The entire process of site selection and With the IV needle assumed to be in the lumen of the vein, preparation should take approximately one minute. the Paramedic should decrease the angle of approach to par- Venipuncture allel the vein and then advance the IV needle approximately ¼ to ½ inch to ensure that the IV needle and catheter are After careful consideration, the Paramedic would select the clearly inside the vein. By failing to perform this maneuver, preferred IV device, remove it from the packaging, and uncap the Paramedic risks losing the IV access. The purpose of this 568 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. maneuver is not just to ensure that the IV needle is inside the then place the thumb and forefi nger of the nondominant hand vein, but also that the IV catheter (which is approximately 1/4 on the EJV. The thumb should tamponade the blood fl ow, inch behind the tip of the needle) is also inside the vein. causing the vein to distend, and the forefi nger should stabilize the EJV in the supraclavicular space. From this stance, the Paramedic would place the IV needle directly over the pre- Street Smart pared EJV site. The angle of insertion for an EJV cannulation is more parallel to the skin, approximately 30 degrees, than Even the short length of the bevel of an IV needle can the angle of insertion for other peripheral IVs. The IV needle is then advanced until a fl ash is witnessed. be too long for a small vein. To reduce the chance The insertion of an IV needle into the external jugular vein of puncturing the posterior wall of the vein, some creates a neck wound. The concern with neck wounds is that Paramedics advocate rotating the IV needle so that room air can be drawn into the wound, creating an air embo- lism. To minimize this risk, the Paramedic should wait until the the bevel is down, decreasing the area of exposure patient exhales before attaching the IV administration set adap- and the chance for error. This technique may be tor.35, 36 Once the EJV IV is in place, precautions should be taken helpful, particularly in venous access in the elderly. to protect the site. The patient’s head should remain in a neutral in-line position. Some Paramedics apply a cervical collar or use a cervical immobilization device to help protect the site. Once the IV needle and catheter are within the lumen, the catheter is threaded off the needle and into the vein. It is impor- Blood Samples tant to realize that the needle is not withdrawn from the vein, Obtaining, or drawing, blood samples from an IV site is easy and but rather the catheter is threaded into the vein. The needle could potentially prevent an additional needlestick, saving the remains in place to help maintain the patency of the incision. patient from avoidable pain and other healthcare providers from If the nondominant hand is available and not holding sta- a potential needle exposure. The most commonly used blood bilization, it can be used to advance the catheter into the vein. drawing system is the vacuum-tube system. To use this system, Otherwise, the fi rst two fi ngers can grasp the hub of the cath- the Paramedic preassembles the vacuum tube collection device eter, in a pincer-like maneuver, and advance the catheter. With and sets it aside for use after the IV access is obtained. the complete length of the IV catheter in place, the needle can With the catheter in place, the Paramedic would with- be withdrawn slightly. Leaving the IV needle inside the IV draw the needle and attach the needleless adaptor to the hub hub blocks the catheter’s lumen and prevents bleeding through of the IV catheter. With the adaptor in place, the Paramedic the catheter until the Paramedic can tamponade the vein. inserts a blood tube into the barrel. Grasping the fl ange of the In anticipation of either attaching the IV administration device stabilizes the assembly. The blood tube is now pushed set adaptor or a blood sampling device, the Paramedic should down, by the thumb, over the covered needle inside the bar- manually tamponade the vein. To tamponade a vein, the Para- rel. The needle pierces the rubber stopper and the vacuum medic applies pressure above the end of the catheter in the draws blood into the tube. vein, which should be just above the sterile fi eld. Some Para- This process is repeated until all of the blood tubes are medics also elect to place a small gauze pad under the hub to fi lled. Then the device is removed and replaced with the adap- catch any bleeding at this time. tor of the administration set. More information regarding types When the needle is completely withdrawn, it must and uses of blood sampling tubes is found later in this chapter. be immediately rendered safe. Some IV needles are self- sheaving whereas others are not. Regardless of the presence of any engineered safety devices, all IV needles should be Street Smart immediately placed in a sharps container. The entire time for insertion should be approximately two minutes, from the time the tourniquet was applied to the time Pediatric veins tend to collapse under the vacuum the tourniquet was released. Proper preparation of supplies, pre- produced by adult vacuum tube systems. For pediatric assembled as necessary, helps to improve overall effi ciency. patients, the blood should be drawn using either a Cannulation of the External Jugular Vein pediatric vacuum tube system or a small syringe. The insertion of an IV into an external jugular vein (EJV) The syringe offers the advantage of low pressure, requires a few modifi cations in technique, but the procedure permitting the Paramedic to gently aspirate a blood is largely the same as for inserting any peripheral IV. To dis- sample. Once the syringe is full, then the rubber tend the vein, the patient should be placed supine, preferably stopper is removed from the tube and the blood with legs slightly elevated about 6 to 12 inches off the fl oor in modifi ed Trendelenburg position. Standing or sitting at the ejected into the tube. patient’s head and facing the patient, the Paramedic would Intravenous Access 569 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Continuous or Intermittent Infusion Once IV access has been obtained, the Paramedic has the choice between instituting a continuous infusion or an intermittent infusion. To establish a continuous infusion, the Paramedic would take the adaptor from the intravenous administration set, remove the protective cap, withdraw the needle completely from the catheter while maintaining tam- ponade, and attach the adaptor to the hub. Once the intrave- nous administration set is attached, the Paramedic would then release the roller clamp and allow the fl uid to fl ow freely for a moment. If the fl uid does not run, it may be a sign of a misplaced or dislodged IV catheter. To troubleshoot the problem, the Para- medic should check to see if the tourniquet has been removed. One of the more common reasons that the fl uid is not running Figure 27-19 Saline lock. freely is that the tourniquet may have inadvertently been left in place (e.g., covered by a falling sleeve) and out of the Para- medic’s sight. Next, the Paramedic would start at the solution and methodically examine down the length of the administra- Securing the Intravenous Catheter tion set for possible mechanical obstructions to fl ow. A gentle With either the administration set attached or the saline lock squeeze of the drip chamber should indicate if there is a pas- in place, the entire apparatus needs to be protected from acci- sage between the solution and the spike. Continuing down the dental displacement. Many Paramedics elect to secure the IV length of the tubing, the Paramedic would check all clamps hub in place with tape, even if a commercial IV dressing is and control devices to ensure that they are open. Inspection of to be used later. There are various kinds of tape available and the tubing may reveal that a tiny obstruction, such as a plug each has its advantages. from the IV solution bag, has lodged in the fi lter, or that the Standard 1/2-inch “silk” tape, adhesive applied to a tubing is kinked. Barring any obstructions in the administra- woven nylon backing, is ideal in most circumstances. If 1/2- tion set, which should have run freely before it was attached, inch tape is not available, then larger sizes, such as 1 inch, can the Paramedic would next observe the insertion site. be divided into two 1/2-inch strips. The diffi culty may lie with the catheter itself. Sometimes The adhesive of standard tape may be too strong for frag- a catheter will become lodged against the posterior wall of a ile skin (e.g., on the elderly patient or the neonate). Remov- vein or against a valve. To unblock the catheter, it merely has ing standard tape from their skin can cause a skin tear. For to be withdrawn slightly and the fl ow reattempted. If all these those patient populations, a paper-backed tape may be more measures fail, then it can be assumed that the IV catheter is appropriate. While paper tape is gentler on the skin, it does not in the vein and the IV catheter should be withdrawn. not adhere as well. The IV dressing should be constantly If the fl uid is running freely, then the Paramedic would monitored. observe the insertion site for any swelling, a sign of infi l- With two approximately 6-inch lengths of tape pre- tration. If swelling is observed, then it can be assumed that pared, the Paramedic may elect to use one of two methods to either the catheter slipped out of the insertion site or that the secure the hub. The fi rst method, called the chevron method, needle, when inserted, was driven through the posterior wall involves slipping the inverted tape, sticky side up, under the of the vein, creating a hole in the vein. Regardless, the IV site hub until it adheres to the hub, then crossing it over the hub. is no longer usable, the IV is “blown,” and the catheter must When completed and in place, the tails of the tape extend at be removed. A description of how to remove an IV catheter an approximately 90-degree angle from the site, forming a V follows shortly. shape. When the tape chevron is in place, the tape should not Alternatively, |
if intermittent infusion is indicated then be directly in contact with the catheter or cover the insertion the IV catheter can be “capped” with a plug-like device that site (Figure 27-20). In some cases, it is advantageous to place appears and functions like the medication port on the admin- two chevrons, each opposite the other. Once the chevron is istration set. In the past, an intermittent infusion device was secured, another length of tape can be placed directly over fi lled with heparin, and described as a heparin well. Research the hub. has indicated that the use of heparin to prevent thrombus for- An alternative to the chevron method is called a “squared mation at the distal catheter tip was unnecessary. Simply fi ll- out” method. Like the chevron method, a length of tape is ing the intermittent infusion device with saline would seal, slid under the hub of the needle. But instead of immediately or lock, the device and prevent thrombus formation. Sub- turning the ends, an approximately 1-inch span of tape is left sequently, saline locks have been used almost exclusively exposed under the hub and the ends turned out at a 90-degree (Figure 27-19). angle. With the fi rst tape in place, another strip of tape is 570 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Figure 27-20 Tape chevron. Figure 27-21 Transparent membrane dressing. placed directly across the fi rst piece and the hub of the cath- eter. The hub of the catheter, now encircled by tape, is secure as long as the tape adheres to the skin. To protect the insertion site, which is a puncture wound, either a dry sterile dressing (DSD), such as a gauze pad, or a self-adhesive bandage may be applied. Many Paramedics apply a small quantity of antibiotic ointment to the insertion site before applying the dressing. Commercially available anti- biotic creams (e.g., Neosporin®) applied at the insertion site create a physical barrier to bacteria and prevent capillary action from wicking contaminated oils from the skin into the wound. Street Smart If a povidone-iodine-based solution was not used Figure 27-22 Omega loop. to wash the site prior to IV insertion, then the application of a dab of antibiotic cream to the site The fi nal step in securing an intravenous infusion is to can help decrease the incidence of infection. Only a tape the intravenous administration set tubing to the patient. small amount is necessary. Too much antibiotic cream Initially, a strip of tape is laid across the adaptor and against can undermine the dressing, causing it to fall off. the skin. Then a loop of tubing is taped across the fi rst strip of tape. This creates a stress loop, called an omega loop, which will absorb any tension on the tubing and potentially prevent Many Paramedics choose to use commercially available the IV catheter from being displaced (Figure 27-22). transparent membrane dressings (Figure 27-21). These trans- parent membrane dressings have several advantages which Adjusting the Infusion Rate make them attractive for fi eld use. Since they are prepack- Before starting any infusion, it is important that the Para- aged in individual sterile packets, transparent membrane medic review the indications for the infusion as well as the dressings are convenient to use. Once a transparent dressing contraindications. A reassessment of the patient’s vital signs, is applied, the moisture under the dressing can pass through jugular venous distention, and lung sounds should be made. the semipermeable membrane while microorganisms, such as Then the Paramedic should check for signs of pulmonary bacteria, cannot pass under the dressing and into the wound. edema to establish a baseline. Furthermore, transparent membrane dressings allow the Para- The selection of an intravenous administration, in part, medic the opportunity to continuously monitor the insertion determines the rate of infusion. For example, a micro-drop site for signs of infl ammation and infi ltration without break- administration set cannot produce the same volume of fl ow ing down the dressing. This is an advantage when injecting in mL per hour, even when the fl uid is running as a straight medications. stream, that a macro-drip administration set can. Intravenous Access 571 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Conversely, it is more diffi cult to dispense a precise volume case with any overdose, a runaway infusion must be reported for infusion using a macro-drop intravenous administration to medical control so that appropriate measures can be taken to set. For this reason, Paramedics use micro-drop intravenous mitigate the medication’s adverse effects and negative impact. administration sets as a standard practice for medication infu- The value of prehospital intravenous infusions for trauma sions to help ensure that the exact dose is administered. When patients is being debated. Early consensus seems to indicate a precise volume of infusion is needed, the Paramedic would that a minimal infusion, one that maintains end-organ perfu- suspend the solution (“hanging the bag”) from a hook-like sion (i.e., a minimal systolic pressure of approximately 80 device called a hanger. The Paramedic gradually releases the to 90 mmHg), should be established.37,38 A runaway infusion roller clamp, counting the drops in one minute to equal the during trauma resuscitation can adversely affect the patient desired fl ow rate. EMS drug infusion rates are infl uenced by in multiple ways, including increasing intracranial pressure, a number of physical factors which are part of the reality of diluting coagulation factors, and increasing hemorrhagic practice in the fi eld and can alter the drip rate. losses.39 A runaway infusion can be just as devastating for the To control the drip rate, the roller clamp or screw clamp medical patient as well. A runaway infusion can quickly vol- applies pressure against the tubing to offset the pressure within ume overload the patient with kidney or heart failure. Subse- the tubing, thus increasing or decreasing fl ow accordingly. quently, the patient can experience hypertension, pulmonary The pressure within the tubing is a function of the height of edema, or cerebral swelling. the column of fl uid and the diameter of the tubing. Many factors can infl uence the rate of fl ow, such as the Mechanical Flow Control Device friction loss within the tubing, the diameter of the tubing, Paramedics use mechanical fl ow control devices to more the viscosity of the fl uid within the tubing, and the length of the accurately control intravenous fl ow of any drug infusions tubing. Assuming that all these variables remain constant, which are caustic, viscous, or have vasoactive medications. the lone act of raising or lowering an intravenous bag—for Several types of fl ow control devices are available on the example, to go through a door or enter an ambulance—will market. Some work by a venturi effect, controlling the fl ow alter the height of the column of fl uid. Therefore, the pressure by adjusting an aperture, described as dial-a-fl ow devices. within the tubing is affected, and that will in turn change the Others work by placing pressure on the tubing, either through drip rate. This all happens without adjusting the roller clamp. a rotary piston or a linear compression (such as massaging Once a drip rate has been established, it is important to try to fi ngers), and “milking” the tubing at a precise rate. Smaller constantly maintain the intravenous bag at the same height. syringe pumps apply pressure to the plunger in precise pulsa- Even with the best efforts of the Paramedics involved in tions to inject the drug into the fl uid stream. a patient’s care, other factors that cannot be as easily con- The advantage of all of these devices is that they can trolled will infl uence a drip rate. For example, cold fl uids run more accurately control fl ow (Figure 27-23). Many are also through an IV access tend to cause vasospasm in the affected equipped with air-in-line alarms, indicating a break in the vessel. Efforts to warm fl uids can help prevent this occur- rence. However, warming an intravenous fl uid to room tem- perature still means that chilled (less than body temperature) fl uid is being infused. Temperature changes, which are not common in the hos- pital setting, are a fact of life for the Paramedic. Intravenous tubing exposed to cold temperatures, such as occurs when trans- ferring a patient to the ambulance in sub-zero degree weather, will stiffen the IV tubing and alter the tension applied by the roller clamp, as well as change the viscosity of the fl uid within the tubing. Even when the patient is safely secured within the ambulance’s temperature-controlled patient compartment, other factors (such as turbulence at the end of a catheter or slack in an armboard) can cause the IV catheter to migrate up against a valve or the wall of the vein, occluding the fl ow. With all of these variables in mind, it is important that a Paramedic regularly confi rm, and then re-confi rm, the drip rate, particularly if a medicated solution is being infused. Mini- mally, a drip rate should be rechecked after the patient is placed in the ambulance and then upon arrival at the hospital. Prefer- ably, the drip should be checked with every set of vital signs. Out-of-control drip infusions, called runaway infusions, can have serious implications. A runaway infusion of a medicated solution results in the patient being overmedicated. As is the Figure 27-23 Flow control device. 572 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. closed intravenous system, and fl uid empty alarms as well set. The secondary intravenous set would be connected to the as obstruction alarms. The greatest advantage of these fl ow continuous intravenous set, now called the primary infu- control devices may be the margin of safety that they bring sion, via a medication port. If a needle is used to attach the to the less-controlled environment of out-of-hospital emer- two sets, it will be necessary to fi rst cleanse the port with an gency medicine. While not impossible, the risk of a run- alcohol prep pad. away infusion is virtually eliminated by these devices. On With the two administration sets now attached, the pri- the downside, the costs of fl ow control devices, including mary set is placed lower than the secondary set. This is the costs of training Paramedics in their proper use, may be usually accomplished by using a plastic or metal hanger prohibitive. that comes with the secondary administration set. The sec- ondary administration set will now take dominance over Secondary Intravenous Infusions the primary administration as its fl uid column is higher If a continuous infusion is running and an intermittent and thus there is more pressure. When the column of fl uid infusion of a medicated solution is needed, the Paramedic in the secondary administration set equals the level of the can establish a secondary infusion, or piggyback infu- fl uid in the primary administration set’s drip chamber, sion, to the primary infusion. This practice has several then the primary drip will resume fl ow at its previous advantages, including the ability to immediately terminate adjusted rate. the intermittent infusion (e.g., if the patient had |
an aller- gic reaction) and permit a bolus and/or drug to counteract Intravenous Injection any ill effects, such as anaphylaxis-induced hypotension. Use of a secondary intravenous infusion also eliminates Paramedics frequently use IV access as a means for the rapid the need for a second IV access and the accompanying dif- injection of IV medications during an emergency. Early inser- fi culty, and time, of preparing and establishing an intermit- tion of an intravenous access device during patient care pro- tent infusion device (saline lock) which would normally be vides Paramedics a nearly instant ability to administer drugs necessary. directly into the circulation and to target organs. After assessing to ensure that the primary infusion is run- If the IV access site has an intermittent infusion ning and that the IV access is patent, the Paramedic would device attached, then the Paramedic would attach a syringe prepare the secondary IV. Special secondary administration and withdraw about 10 mL of fl uid from the device and sets which have a shorter length are available (Figure 27-24). discard the waste into an approved sharps container. The The secondary set would be run out as per the procedure Paramedic would then attach another syringe, either fi lled described previously for a continuous infusion administration or prefi lled with the medication, to the infusion device and inject the medication. This process is called IV push. Note that if a needle is used then the self-sealing membrane of the injection port must be cleansed. Immediately after injecting the medication, the device is fl ushed with 10 to 20 mL of NSS to clear the medication from the device and assure that all of the medication goes into the circulation (Figure 27-25). Figure 27-24 Secondary intravenous administration set. Figure 27-25 Saline fl ush with prefi lled syringe. Intravenous Access 573 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. If the IV access site has a continuous infusion in place, then the Paramedic would fi rst clamp the tubing, using the roller clamp or slide clamp, and then attach the syringe or prefi lled ampoule, as just described. Once the IV push is completed, the Paramedic may elect to fl ush the tubing with 20 mL of NSS and then unclamp the line. He may also choose to unclamp the line and allow a free fl ow of fl uid to fl ush the IV line for approximately one minute, then re-adjust the fl ow rate. If the patient is in cardiovascular collapse, then the patient’s arm should be raised to help the medication drain out of the limb. Similarly, if the patient is in cardiac arrest, then the limb should be raised and a minimum of one minute of external chest compressions performed to ensure that the drug is circulated. In every case it is important that the Paramedic observe the IV access site for swelling, pain, and other signs of infi l- tration while injecting the medication. Some Paramedics purposefully place the medication port proximal to the IV access site so that the IV insertion site can be observed. If an infi ltration is suspected, then the IV push is stopped and measures taken to counteract the effects of any medication that has leaked into the subcutaneous tissue. It is important Figure 27-26 Flashback of blood verifi es venous to report any intravenous infi ltration. If unchecked, some competency. medications (for example, 50% dextrose) can cause severe local tissue necrosis with the potential for subsequent tendon, constrictive. The distal circulation, sensation, and movement muscle, and nerve damage. should be checked periodically thereafter. An obstructed IV catheter should never be forcibly Obstruction of Intravenous Flow injected with solution (IV fl ush) to remove any obstruc- tions. The risk of forcing a thrombus into the circulation is The fl ow of an IV may slow, or even stop, for a number of rea- not equal to the benefi t of having an intravenous access. The sons. Before removing the IV catheter, the Paramedic should Paramedic should consider removing the suspect IV catheter assess the situation for correctable errors. Starting at the solu- and re-establishing a new IV access. tion bag, the Paramedic would methodically inspect the entire intravenous apparatus. For example, fl ow will stop if the solu- Complications of Intravenous tion bag is empty, a clamp has slipped, or the tubing is kinked. After assessing the administration set and determining that Infusions it is clear of mechanical obstructions, the Paramedic would Despite the best efforts of Paramedics, local or systemic then turn his attention to the IV access site. complications can occur as a direct result of an IV access An infi ltrated IV access site will eventually slow or stop or infusion. An attentive Paramedic can usually detect these an infusion. If the IV access site is infi ltrated, then the IV complications and mitigate the circumstances in order to catheter must be removed immediately (this process is dis- reduce the harm to the patient. cussed later in the chapter). Finding no visible obstructions Arteries and nerves tend to be bundled with veins, par- or infi ltration, the Paramedic may elect to see if there is a ticularly deep veins. Therefore, they are at risk for accidental return of blood, called a fl ashback, when the solution bag needle puncture. An unintentional arterial puncture would be is lowered below the level of the patient’s heart. A fl ashback recognized if the Paramedic noticed a pulsating column of (Figure 27-26) indicates that the IV access remains patent. blood within the fl uid column. However, recognition of an Some IV catheters are positional, meaning that the cath- arterial puncture is more diffi cult in zero fl ow states, such eter lodged up against the wall of a vein or a valve and the IV as cardiac arrest. Careful attention to anatomy, noting the fl ow has been obstructed. To correct a positional IV catheter, location of proximal arteries by their pulse points, can help the Paramedic may elect to withdraw the needle slightly. This decrease the incidence of accidental arterial puncture. process includes breaking the dressing down or raising the A nerve can also be accidentally punctured during an IV hub of the IV catheter off the skin with a gauze pad. If the insertion attempt. Patients usually alert the Paramedic imme- IV access is in a joint, it is advisable to place the joint onto a diately following an accidental nerve puncture. The patient padded splint. If a padded splint is used, then distal circula- will complain loudly of shooting pain, numbness, and tingling tion, sensation, and movement should be assessed before and in the affected limb. Immediate withdrawal of the offending after the splint’s application to ensure that the splint is not needle should provide the patient with immediate relief. 574 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Immediately following successful cannulation of a vein Signs of thrombophlebitis include warmth in the area, by an IV catheter, and frequently thereafter, the Paramedic pain upon palpation, and reddened and swollen tissues. As should assess the IV access for signs of infi ltration or infec- the infection progresses, the infection can advance up the tion. Infi ltration can occur by several mechanisms puncture of vein, creating a visible red trail along the course of the vein the posterior wall, enlargement of the initial incision site, or and pain along the vein’s length. displacement of the catheter. Regardless of the mechanism, While a Paramedic may rarely see a thrombophle- the IV solution seeps into the interstitial fl uid compartment bitis related to a fresh IV, Paramedics may be witness to a (ICF) (i.e., the third space). The resultant swelling can create pyrogenic reaction, a devastating systemic complication increased pressure within a compartment, which can lead to of intravenous therapy. A pyrogenic reaction occurs when impingement of nerves, muscle damage, and compression of a contaminated fl uid, or fl uid run through a contaminated blood vessels (compartment syndrome). administration set, is infused and leads to nearly immedi- One of the earliest signs of infi ltration can be a slow infusion. ate sepsis. Symptoms of a pyrogenic reaction usually occur Other signs of infi ltration include local edema, complaints of within 30 minutes of the initiation of the infusion and include pain at the site, and localized cooling of the skin (Figure 27-27). complaints of headache, chills, and backache. Signs that will An infi ltration of an unmedicated solution should be treated by accompany a pyrogenic reaction include fever, tachycardia, immediate removal of the catheter and application of a warm and, in severe cases, cardiovascular collapse. Examination of compress to the site. Any infi ltration of medicated solutions the solution for contaminants as well as verifi cation of the should be reported and treated immediately. expiration date can help reduce the incidence of pyrogenic Occasionally IV sites become infected. While a Para- reaction (Figure 27-28). medic would not see an infection of an IV site from a recently If a pyrogenic reaction is suspected, the Paramedic should placed IV, patients receiving at-home intermittent intravenous immediately discontinue the infusion. The administration set infusions with temporary indwelling intravenous catheters and intravenous solution should be retained for microbiological and those who are discharged home after a short hospital examination and the lot numbers of the solution recorded on the stay may have signs of an infection at the insertion site. An patient care report. Fortunately, with the advent of disposable infection at the insertion site is called a thrombophlebitis. single-use administration sets and tightly controlled manufactur- An IV access site is essentially a puncture wound, and the ing processes, the number of pyrogenic reactions is very low. body responds to an IV cannulation as it would any wound. Another potentially devastating complication of intra- A thrombus is formed at the wound and the injury healing venous infusions is volume overload. A volume overload process begins. However, the catheter keeps the wound open. occurs when a positional IV access is inadvertently adjusted Bacteria tends to track into the wound, by capillary action, and the infusion fl ow is unrestricted. It can also occur when and the area becomes infl amed.40–42 a clamp is released (e.g., to administer a fl uid bolus) and the infusion rate is not re-adjusted. The symptoms of a volume overload include a nonpro- ductive cough, wheezing, and complaints of shortness of breath or headache. Accompanying signs of volume overload include hypertension, marked jugular venous distention, and crackles in the lung fi elds that are indicative of pulmonary Figure 27-28 Grossly contaminated solution Figure 27-27 Infi ltration of medication at (on the right), as compared with clean solution intravenous site. (on the left). Intravenous Access 575 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. edema. Initially, the Paramedic should reduce the infusion to gloved nondominant hand. With the gloved dominant hand, KVO/TKO or consider using an intermittent infusion device the Paramedic would gently apply traction to the catheter’s (a saline well). Prehospital care of the patient with a sus- hub in the opposite direction of the insertion. With the entire pected volume overload centers on symptomatic relief and length of the |
catheter out of the vein, the Paramedic would supportive care. continue to apply direct pressure to the wound and elevate the Another serious complication of intravenous infusions is limb. If the IV access was in the antecubital fossa, the patient an air embolism. An air embolism can occur when the Para- should be encouraged to keep the limb straight and elevate it. medic fails to run fl uid through an intravenous administration Bending the elbow will widen the opening created by the IV set to fl ush the line prior to use. Symptoms of air embolism catheter and thus increase bleeding. The catheter and admin- include chest pain and lightheadedness. Signs of air embo- istration set should be discarded safely in a biohazard bag and lism include cyanosis, as well as hypotension which can, in a notation made of the removal of the IV access, including the severe cases, lead to cardiovascular collapse. If an air embo- exact location of the access site. lism is suspected, the infusion should be stopped. The patient should then be placed in the left lateral recumbent position, with the right lung superior and the feet elevated above the Intraosseous Access level of the heart. The Paramedic should provide supportive Before the invention of the plastic IV catheter, venous access care and contact medical control for further instructions. was obtained using large metal needles, needles that would be resharpened, sterilized, and reused again and again. These Infusion-Induced Hypothermia large gauge needles often made venous access in the elderly or the vasculopathic patient diffi cult to obtain and alterna- An all too common complication of intravenous infusions tives were sought to peripheral venous access. is hypothermia. The infusion of large quantities of room- In 1922, Dr. C.K. Drinker, of Harvard University, dem- temperature solutions will rapidly cool the body and lead to hypothermia.43,44 onstrated that the use of metal needles inserted into the bone If it is necessary to infuse large quantities marrow of the sternum (intraosseous (IO)) could provide of solutions, then consideration should be given to provid- venous access to the circulation. Dr. Drinker confi rmed that ing a warming blanket (hypothermia blanket) or other similar these intraosseous infusions rapidly infused into the bone device. Some Paramedics use commercially available blood marrow and then later into the central venous circulation. warmers, special heated compartments or thermal sleeves to Later, Dr. Tocantins and Dr. O’Neill expanded on ster- warm the intravenous fl uids prior to administration. Abbott nal intraosseous access sites and included the long bones Corporation, a major supplier of intravenous solutions, rec- (tibia and femur). With multiple sites readily available, and ommends the use of a “conventional warm air oven” which the invention of the bone needle for intraosseous access, IO warms the fl uids before administration. Once the fl uids are access became practical and convenient. During the 1940s removed from the oven, they should be used within 24 hours and 1950s, IO infusion in critically ill patients became some- and not re-warmed again. what commonplace and was used by military medics in World The use of microwave ovens to warm intravenous solutions War II in over 4,000 documented cases. is commonly practiced in emergency departments and operat- However, with the advent of plastic catheters and ing rooms. Caution should be used when microwave ovens are improved venous catheter technology, IO use saw a decline used to warm intravenous solutions because microwave ovens after World War II and remained an historic relic of past med- can create “hotspots” of fl uid within the solution that, during ical practice until 1984. In 1984, Dr. Orlowski, after witness- infusion, could scald the epithelial (inner) lining of the vein. ing IO use in children affl icted with cholera in India, wrote an The use of warm water baths is also not recommended. article in the American Journal of Diseases in Children citing Water from the warm water bath may cross the plastic fl exible the advantages of IO in pediatrics. IO infusion was reborn for container wall and contaminate the solution. Such contami- pediatrics and is now commonplace. Pediatric IO is discussed nation could lead to a potential pyrogenic reaction. in detail at the end of the chapter. Removing Intravenous Access More recently, due to a growing population of aged patients, vasculopathic patients, and emerging new medical Paramedics may be called upon to remove, or discontinue technologies that hold promise for use in the fi eld, the need (DC), an intravenous infusion. A careful step-by-step proce- for venous access has grown more acute. Therefore, the inter- dure will minimize pain for the patient and the potential of est in IO infusion for adults has been revisited. contamination to the Paramedic. The fi rst step is to clamp the administration set and stop the infusion. With the infu- Anatomy and Physiology sion stopped, the Paramedic should gently loosen any tape that is securing the IV catheter. An alcohol prep pad can be of the Long Bones used to undermine the tape’s adhesive. With the tape loose, A long bone has two ends (the epiphyses) and a shaft (the dia- the Paramedic would then place a small gauze pad over the physis). Within the shaft of the bone or the medullary cavity is insertion site and apply gentle downward pressure with the the bone marrow. At the ends of the bones, within the epiphysis, 576 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. is the soft, sponge-like cancellous bone. Together the medullary on the device and the manufacturer’s recommendations, an space and the cancellous bone make up the intraosseous space. IO needle can be placed in the sternum, the tibia, the femur, The IO space contains a complex network of blood ves- or the humerus. Next, the exact point of placement must be sels that connect to the major veins of the central circulation identifi ed, often using adjunct landmarks, and properly pre- via a series of longitudinal Haversian canals that exit the bone pared with povidone-iodine or similar antiseptic (Skill 27-3). and connect directly into the major veins. Infusing fl uids into For a step-by-step demonstration of Intraosseous the intraosseous space ultimately infuses fl uids into the cen- Access, please refer to Skill 27-3 on pages 589–590. tral veins via these Haversian canals. After inserting the needle, following the manufacturer’s Intraosseous Devices recommendations, the needle should be fl ushed with 5 to 10 cc of sterile saline to ensure patency. If the patient is con- A number of IO devices are presently on the market. These scious, an additional bolus of lidocaine (approximately 10 cc) devices range from manually inserted IO needles, the type can help to reduce the pain of infusion. used primarily in children, to medical drills that create a pre- cise opening for insertion of an IO needle. Because of the large number of IO devices on the market, Paramedics are advised to read the accompanying medical literature that Street Smart comes with each device and to familiarize themselves with the device by practicing on a manikin or model before trying to utilize the IO in the fi eld. Improper placement of an IO needle in an obese patient can be avoided if the Paramedic monitors the Indications and Contraindications insertion. If bone resistance cannot be felt once the There are several indications for adult IO placement. One needle has been placed to a depth of approximately indication is cardiac arrest.45, 46 During cardiac arrest, the 5 cm, indicated by a black band on some IO needles, cardiovascular system is in collapse and venous access can then the needle should be withdrawn and an be a challenge. Intravenous access can be diffi cult to obtain or is obtained at a cost of prolonged scene times. The rigid alternative site prepared. container of the IO, the bone, provides a ready access even during zero blood fl ow states. Other indications include any time there is a need for an immediate access for medication Medication Administration administration for the patient in extremis. The majority of prehospital medications can be administered Advantages of IO access are also several-fold. IO access via the IO route (Table 27-1). The exceptions to IO admin- is rapid, quicker than IV access in many cases, and generally istration include 9% saline, also known as super saline, and requires less skill and training to master. In one study, IO adenosine. access was able to be obtained in the fi eld within 20 seconds This list includes medications typically used during or less with a 97% success rate.47–50 a cardiac arrest. Considering the speed of attaining thera- However, IO insertion is not without its risks. IO insertion peutic levels of these drugs via the IO route, IO is consid- can be painful in conscious patients, although that is not always ered by most authorities to be preferable over endotracheal the case. Some patients have compared the pain of an IO inser- administration. tion to the discomfort of a large bore IV. IO infusions can also be painful, but with a bolus of lidocaine can further reduce the pain Phlebotomy of infusion. Finally, the IO has a potentially higher risk of osteo- myelitis. However, the incidence of osteomyelitis is uncommon. A sample of the patient’s blood, for laboratory analysis, may It has been reported that the osteomyelitis rate for IO infusions be drawn at the time that the IV access is obtained. However, is about one in 200 cases. Other attendant risks include fat embolism, fracture, extravasation, and compartment syndrome. Table 27-1 List of IO Medications It should be noted that these complications are rare and can usu- ally be prevented by careful insertion and monitoring. • Amiodarone • Furosemide The single largest drawback to IO may be the inability to • Atropine • Lidocaine infuse large bolus of fl uids. The IO infusion is generally similar • Dextrose 50% • Naxolone to that of a 20 gauge IV catheter.51 The addition of a pressure • Diazepam • Rocuronium infusion bag enhances fl ow rates to more acceptable levels. • Dopamine • Succinylcholine • Epinephrine • Vasopressin Intraosseous Placement • Etomidate • Vecoronium Preparation of the IO site is similar to preparation for an IV • Fentanyl • Versed insertion. First the Paramedic needs to select a site. Depending Intravenous Access 577 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. there are times when a blood sample is required but IV access then advanced, bevel up, into the skin and then the vein, at is not necessary. In this case, a Paramedic would perform a about a 15 to 20 degree angle. Once the Paramedic is con- phlebotomy, drawing blood through a straight needle, to fi dent that the needle is in the vein, then the blood tube is obtain the sample. joined with the sheaved needle inside the barrel and blood is Prior to performing the venipuncture, the Paramedic automatically drawn up. needs to assemble the necessary equipment, including blood After the fi rst fl ash of blood occurs, confi rming place- sample tubes. There are a number of blood sample tubes and ment, the tourniquet is released and the blood tube allowed each has a specifi c purpose. The color of the stopper indicates to fi ll completely. Red-topped tubes should be placed aside a blood tube’s use. The patient’s condition usually dictates while other colored-topped tubes are generally gently inverted which blood tubes will be used and is based upon the expec- approximately 10 times, but not shaken, before being set tation that |
a certain battery of diagnostic laboratory tests will aside. Multiple blood tubes can be fi lled in this manner. be performed to help discern the pathology and guide the Once the phlebotomy is completed, a cotton gauze pad is treatment. placed over the needle insertion site and the needle quickly The red top tubes are sometimes called clot tubes withdrawn in the direction opposite of insertion. Cotton balls because the tube contains no additives or preservatives to should not be used as they tend to adhere to and pull out plate- prevent blood clotting. Without additives, such as an antico- let plugs at the insertion site. With the bleeding controlled, agulant, the blood clots and the serum rise to the top. The the Paramedic can proceed with marking the blood tubes with percentage difference between the amount of space fi lled by the name of the patient, the date and time of the phlebotomy, the clot (formed elements such as red blood cells) and the and the Paramedic’s initials. total volume is the hematocrit. The patient’s hematocrit is an After placing the blood tubes in a clear plastic bag, the important indicator, particularly for trauma patients. Paramedic should ensure the blood tube’s safe transportation Samples of the serum are used to test the blood chemis- to the receiving hospital. Some Paramedics tape the blood try (i.e., the electrolytes, etc.) in the blood. The clot is used tubes to the outside of the intravenous solution bag. This prac- to identify the variety of blood (blood-typing) and to cross- tice is acceptable provided the contents are clearly visible. match it to blood that is available in the blood bank. It is The use of a nonsterile glove is discouraged, as the contents important that the serum separates from the formed elements inside the glove are not visible. All potentially infectious in the blood; therefore, it is counterproductive to invert or materials (PIM) must be clearly marked with the biohazard shake the blood tube. symbol or some other warning that indicates the presence of The light blue and lavender-topped tubes have anticoagu- PIM. A cut sustained from the broken glass of a blood tube lants (3.2% sodium citrate and sodium EDTA, respectively) is an exposure to blood-contaminated sharps and may be a added to them to prevent the blood from clotting. These anti- reportable incident. coagulant tubes are used for special clotting studies, such as the partial prothrombin time (PPT), as well as red blood Pediatric Phlebotomy cell studies, including hematocrit and hemoglobin (H&H). The laboratory results from these studies are important if Drawing blood from a child can be a challenge. By applying the patient is destined for the operating room or may receive the principles of pediatric venous access (discussed later in fi brinolytics. the chapter), along with the principles of phlebotomy (just A number of other blood tubes are available—gray, discussed), the Paramedic can expect to have success. green, royal blue, and yellow—and each has a specifi c indi- A heel stick is performed to obtain a blood sample from cation. For example, tan-topped tubes have sodium heparin, an infant. A heel stick—puncturing the infant’s heel with a another anticoagulant, and are used for tests of lead. lancet then drawing the blood off with a capillary tube—is When in doubt, or when no orders exist, a standard blood performed on newborns. Practice while under the careful sample usually includes drawing a red-topped tube, a blue- supervision of a practiced provider is the best means for Para- topped tube, and a lavender-topped tube. The order of the medics to master this technique. blood draw is also important. To prevent potential contamina- For older children, phlebotomy is performed as it is on tion from additives, the tubes without additives (red-topped adults, with a few exceptions. Children have smaller veins; tubes) are drawn fi rst and the “wet” tubes (those with addi- therefore, smaller needles (25 g to 27 g) are used to draw tives) are drawn last. blood. Children’s veins also tend to collapse under the pres- To perform a phlebotomy, the Paramedic could prepare sure that a vacuum tube system produces. Venous collapse the site as if an IV access was going to be attempted. Fre- can be averted by either using a pediatric vacuum tube sys- quently, the preferred site for a phlebotomy is the antecubital tem or using a 5 mL or 10 mL syringe attached to a butterfl y fossa, although any peripheral vein is acceptable. needle. Gentle intermittent traction on the syringe’s plunger Commonly, a straight hollow-bore needle attached to a will gradually draw the sample from the vein. With a little vacuum tube apparatus is used for phlebotomy. With the vein patience, the application of age-specifi c therapeutic interven- prepared, the needle shield is removed from the needle and tions, and the right equipment, the Paramedic can expect to the gloved dominant hand stabilizes the vein. The needle is be successful with a phlebotomy on a child. 578 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Blood Cultures Age-Appropriate Approaches to Pediatric When a patient has a fever or the Paramedic suspects that the Patients with IV Access patient may have septicemia (an infection in the blood), then Regardless of a child’s age, each child views intravenous a blood culture could be drawn. The blood culture is a special therapy as a painful procedure that he would rather avoid. laboratory analysis used to test the blood for the presence of Gaining a child’s trust and cooperation will tend to improve sources of infection called pathogens. Common blood cul- success with pediatric IV access. Trust and cooperation is ture specimen collection units are either aerobic and anaero- earned when the Paramedic carries out the child’s IV therapy bic (Figure 27-29). Blood cultures usually involve obtaining with an age-appropriate therapeutic approach. enough blood to fi ll two broth-containing blood tubes or As a general rule, the Paramedic should not separate the bottles, the broth being a medium for bacterial growth. One child and parent during the IV attempt. However, practice, of the blood cultures is used to test for aerobic microorgan- experience, and personal interaction with the parent is a better isms and the other blood culture is used to test for anaerobic basis for that decision. Involving the child in the preparations microorganisms. and decision making may help the child feel more in control, It is important that medical asepsis be practiced whenever a provided the child is not given the opportunity to say no, and blood culture is drawn. The venous access site must be cleansed helps foster trust between the Paramedic and the child. with a povidone-iodine-based solution, such as Betadine®, or The child should never be told, by either the Paramedic similar antigermicidal solution and the solution allowed to or the parent, that the insertion of an IV will not hurt. dry. While the solution is drying on the skin, the Paramedic Rather, the focus should be on the benefi t of the IV and how should take a new swab and cleanse the top of the blood culture quickly the IV will be over. Needless to say, this places a tube/bottle. The remainder of the phlebotomy would proceed burden on the Paramedic to ensure that all of the necessary as usual. Although practices vary from hospital to hospital, in supplies are immediately available and prepared. Similarly, every case medical asepsis is practiced the prevention of acci- the child should not be told that only one IV attempt will dental contamination of the specimen is important. be necessary. The number of IV attempts is a function of the child’s condition and the importance of the IV. Finally, Pediatric Intravenous Access regardless of a child’s age, he should be encouraged to cry, Pediatric intravenous access can be challenging to even the privately, without fear of ridicule, and to express his anger most experienced Paramedic. The key to success in pediatric or frustration without fear of judgment. The Paramedic IV access is to match the IV access site chosen to the urgency understands that these outbursts are not meant personally. of the situation and then take a therapeutic approach to the Such expressions are healthy and an indication that the child that is matched to the child’s developmental level. child is coping appropriately with the situation. The choice for a peripheral pediatric venous access can Developmentally speaking, infants are learning trust and be very age-dependent, owed to the child’s changing body have a strong child–parent bond. The infant may not trust the habitus. For example, an umbilical venous access may be Paramedic but does trust the parent to protect him. A parent appropriate in a newborn whereas a venous access in the dor- should be encouraged to comfort the infant before and after sal venous arch of the hand may be more appropriate for a the venipuncture. Often a pacifi er can help to sooth the infant toddler. while the procedure is going on; however, the infant should not be given a bottle-feeding, as the risk of vomiting and aspi- ration offsets any advantage. If the infant is fussy, and there is a risk of accidental catheter displacement, then a swaddling board (e.g., an infant blanket over a short padded board) may be used to immobilize the infant. Toddlers exhibit their growing autonomy by attempt- ing to assert their control. The toddler should be dealt with matter-of-factly and told (in simple, age-appropriate terms) what is about to happen. Age-appropriate distractions are often very useful at this age as the child attempts to dem- onstrate her self-control. However, it is not uncommon for a child at this age to regress. A parent should be available to comfort the child. Preschoolers are capable of assisting with preparation and setup (e.g., tearing pieces of tape) and want to appear confi dent. However, preschoolers have a fear of the unknown, particularly about pain. Therefore, they should be told, in a Figure 27-29 Blood culture specimen straightforward manner, what is going to occur. This approach collection units. helps to eliminate some of the fear-producing fantasy the Intravenous Access 579 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. child might imagine. When the IV access has been obtained, the preschooler should be commended for her cooperation and permitted to express her emotions. Paramedics may be taken back by the articulate manner which the preschooler may express herself. School-aged children, up to adolescence, are thoughtful and generally understand the implications behind the state- ments that the Paramedic makes. The Paramedic should encour- age the school-aged child to ask questions and then provide answers at an age-appropriate level. Limited decision making, such as determining the arm that the IV is to be started, can help the child feel more in control and less fearful. Adolescents can be treated like an adult, more or less. Time spent with fuller explanations and a question and answer period helps to gain both their trust and their coopera- Figure 27-30 Umbilical catheter attached to a tion. Adolescents are concerned about body image and peer three-way stopcock. approval. The Paramedic should be forthcoming with praise regarding positive aspects of the relationship and avoid any criticism of the adolescent’s conduct. In some instances, an adolescent may be content to listen to music from a head- the catheter. Opening the stopcock, the Paramedic should set while the IV is being started. This is not a demonstration gently aspirate, by pulling back on the syringe’s plunger, until of contempt or aloofness, but rather an |
effective distraction a free fl ow of blood is observed. technique. With the catheter now in place, fl uids and/or medica- tions (such as 0.1 mg of epinephrine 1:10,000) can be rapidly Umbilical Venous Access (UVC) administered. The Paramedic should tighten the umbilical tie For a newly born, with a medical emergency, it may be pos- to secure the umbilical catheter in place and prevent exces- sible to gain venous access via the umbilical cord to adminis- sive bleeding from the umbilical stump. ter fl uids and drugs, such as epinephrine. The umbilical cord, that rope-like appendage between mother and child, has two Scalp Vein Access arteries and one vein, surrounded by Wharton’s jelly, and has The thought of inserting a needle into an infant’s scalp may no nerves. The two umbilical arteries carry deoxygenated sound bizarre to many Paramedics. However, pediatricians blood from the fetus to the placenta, and the umbilical vein and pediatric nurses have used scalp veins for venous access carries oxygenated blood from the mother to the fetus. Some for decades. Scalp veins can provide a reliable venous access umbilical cords, however, have only two vessels: an artery that is easy to obtain and even easier to maintain. and a vein. Newborns with only two vessels often have asso- The scalp veins are generally very prominent, have no ciated congenital anomalies. valves to interfere with cannulation, and are only thinly To begin, the Paramedic would loosely tie off the umbili- obscured by the fi ne hair of the infant. The most commonly cal cord, around the base, with cloth umbilical tape. Tying used scalp veins are the metopic vein, located at the mid- the umbilical tape too tight can prevent the passage of the forehead region, and the superfi cial temporal veins located venous catheter. If the tie is too loose, as evidenced by bleed- bilaterally on the forehead (Figure 27-31).52 A broad rubber ing, it can be re-tied tighter later. The umbilical stump is now band placed around the head at approximately ear level will cleansed with a povidone-iodine solution. While waiting for help distend the scalp veins. the povidone-iodine solution to dry, the Paramedic would The infant should be restrained, as needed, and the area prefi ll a 5 French umbilical catheter with NSS via a syringe prepared. Using scissors, any negligible amount of hair attached to a three-way stopcock (Figure 27-30). should be clipped and the area cleansed with povidone-iodine After donning sterile gloves, the Paramedic would take or similar antiseptic solution, using care to not have the solu- the sterile scalpel and perform a perpendicular transection tion run into the eyes. of the umbilical cord proximal to the clamp. Examination of After fl ushing the intravenous catheter (either a butter- the cord should reveal three orifi ces—two arteries and one fl y needle or an over-the-needle device) with sterile saline, vein—with the vein typically at the 12 o’clock position. The the Paramedic would pull gentle traction on the vein with thicker-walled arteries are usually inferior, at 4 and 8 o’clock, the nondominant hand and proceed with inserting the nee- unless the cord is twisted, which is a common presentation. dle. When a fl ash of blood is visible, the tourniquet can be The umbilical catheter would be advanced through the removed and a small amount of saline solution injected to test umbilical vein, the larger orifi ce, and toward the heart for a the catheter’s patency and position. distance of approximately 2 to 4 cm. Once the umbilical cath- If the saline solution fl ushes easily, without evidence of eter is past the orifi ce, there should be a fl ash of blood inside infi ltration, then the IV catheter should be secured in place. 580 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Next, the vein needs to be distended. Adult venous tour- niquets apply too much pressure and pinch the child’s ten- der skin. It is easier and more effective if another Paramedic encircles the limb, with a fi rm grasp, effectively distending the veins while stabilizing the limb. Next, the venous access sites are chosen. The venous access sites for a child are generally the same as an adult’s access sites. The Paramedic may have diffi culty fi nd- ing an IV access site on a pudgy infant’s forearms, so the use of warm compresses can increase venous distention and improve visualization; observing caution to prevent burns. With the IV site selected, the Paramedic should choose the appropriate IV device. Generally, Paramedics choose to use the butterfl y IV needle. Butterfl y needles should not be placed in freely movable joints but rather in areas, such as the scalp or dorsum of the hand, which can be immobilized. To insert a standard IV catheter into the dorsum of the hand, the Paramedic should grasp the child’s fi ngers with the thumb, pulling traction on the vein while immobilizing the hand. Once the hand is stabilized, the Paramedic would approach the vein with the needle almost parallel to the skin Figure 27-31 Anatomy of infant scalp veins. and advance the needle until a fl ash of blood is visible in the catheter’s hub. It is good practice to immobilize the limb with the IV Many Paramedics place a clear plastic cup-like shield over catheter to a padded short board. Caution should be observed the site to protect it from incidental trauma. to ensure that the securing straps/tape is not acting as a venous tourniquet, creating backpressure, compromising the IV site, and possibly causing an infi ltration. Street Smart Next, the IV site should be dressed. After the transparent dressing is in place and the tubing is secured, with an omega Infants and children cannot tolerate a fl uid overload loop, a length of protective netting can also be applied length- wise along the limb. The netting permits observation of the as well as an adult. Immature kidneys have more site while protecting the tubing, catheter, and so on. Alterna- diffi culty adjusting to the changing electrolytes tively, a small paper cup can be cut in half and placed over the and fl uid osmolarity that occur with a massive fl uid site to act as a protective shield. infusion. For these reasons, pediatric intravenous infusions are run cautiously and through a burette or Street Smart an infusion pump in most cases. If time permits, the use of EMLA or ethyl chloride solution, two topical anesthetics described earlier, Peripheral Pediatric Venous Access can markedly reduce the child’s discomfort.53 The techniques for peripheral venous access are the same for children as they are for adults with just a few minor variations. However, attention to these differences will help to ensure the Pediatric Intraosseous Access Paramedic is successful in obtaining venous access in a child. In high-priority situations, such as pediatric cardiac arrest, Unlike adults, children cannot be expected to remain immediate venous access is imperative. In those cases, estab- motionless while an IV needle is being inserted. Two Para- lishing an IV catheter is too time-consuming and has the medics may be needed: one to start the IV and the other to deal attendant risk of failure. In times of high peril, an intraosseous with the child, including restraining the child as needed. The infusion is indicated.46, 54–57 When time is of the essence, the child should be placed supine. In an ambulance, it is common intraosseous route offers many advantages over traditional to have the parent sit at the head of the stretcher, to comfort peripheral venous access. To begin, the intraosseous route the child, while two providers sit on each side. Use of a small remains available even during cardiac arrest, unlike periph- blanket, used as a swaddling cloth, can help immobilize a eral venous access that collapses. Next, the intraosseous child. With one limb exposed, the child is ready for an IV. infusion can generally be established within a minute and a Intravenous Access 581 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. half. Then, once the needle is in place it is essentially fi xed to marrow may all be injected back into the bone and the intra- the bone and is fast and secure. Finally, the amount of distal venous administration line connected. blood fl ow inside the bone’s marrow quickly clears medica- The needle should be standing upright, without support. tion and circulates it directly to the central circulation and The IO needle’s fl anges, if available, can be secured to the onto the heart. limb with tape to provide protection from accidental displace- Common complications of intraosseous needle (IO) ment. A sterile dressing is then usually placed around the IO placement include misplacement of the needle, inadvertent needle fi rst. A split gauze pad can be used, although precut puncture of the posterior wall of the bone, and extravasation surgical sponges are available commercially. of fl uids into the tissues. Other complications, such as inter- After the intravenous solution is connected, the clamp is ruption of the growth plate and osteomyelitis, are rare if the released. The solution should run freely, and then slowed to Paramedic closely follows needle insertion guidelines. the desired rate of infusion. The posterior portion of the limb While technically there are numerous locations for an should be palpated for evidence of infi ltration. Intravenous intraosseous needle placement, Paramedics concentrate on solution infusing into the soft tissues will swell the tissues, four primary sites. The fi rst site, and the site of choice, is making them fi rmer in the process to the touch. the proximal tibia.58 The insertion site on the tibia is located As is the case with all peripheral venous access, attempts approximately 2 centimeters, or two fi nger widths, distal and should begin distal and move proximal. Once a bone has had medial to the tibial tuberosity on the tibial plateau. Alterna- one attempt made for IO access, it should not be used again. tively, another insertion site is available on the distal femur, 2 centimeters above the distal epicondyle and in the midline of the femur. While the distal tibia, proximate to the medial Central Venous Access malleolus, and the anterior iliac spine are also acceptable Ideally, the best route of medication administration would sites, they are rarely used by Paramedics. be by injection directly into the central circulation where it Intraosseous needles, like all other peripheral venous can be quickly carried to the target organs almost instantly. access, cannot be placed into an extremity with a fractured Central venous access, long intravenous catheters placed into bone. If the limb has a painful, swollen area, secondary to the great vessels, provides a route for central venous medi- trauma, then a fracture should be suspected and the area cation administration. An access to the central venous sys- avoided for IO needle placement. tem would also permit the measurement of central venous Once the desired insertion site has been identifi ed, the pressure (CVP), a measurement used to assess a patient’s Paramedic should prepare the site with a povidone-iodine swab hemodynamic status. Finally, central venous access permits or similar antiseptic solution. While surgical asepsis is not nec- frequent blood sampling without the annoyance of repeated essary, it is important that Paramedics practice strict medical needlesticks. asepsis, taking all precautions to prevent bone infection. It is estimated that fi ve million central venous access If the child is conscious, then it may be necessary to infi l- devices (CVAD) are placed annually in the United States trate the area with an |
anesthetic such as 2% lidocaine. How- alone. A small fraction of those are put in place by Paramed- ever, in the fi eld, the placement of an intraosseous needle is ics in the fi eld. However, every Paramedic should know how generally performed under emergency conditions. The patient to access a CVAD during an emergency. is either unconscious or semiconscious and can feel the pain. With the intended site properly prepped, the Paramedic Types of Central Venous grasps the limb from above with the nondominant hand to stabilize the limb. The limb should not be held in the palm of Access Devices the hand. The risk of slipping with the IO needle and piercing A large number of central venous access devices are available the palm is too great. The IO needle is now placed against the on the market. Some CVADs are put in place during a special skin at a 90-degree angle perpendicular to the skin or slightly surgical procedure whereas others can be placed in the fi eld caudal, away from the epiphyseal plate (growth plate) and during an emergency by specially trained Paramedics. The inserted with a twisting action. As the IO advances, it will common feature of all of the central venous access devices advance quickly until it meets the resistance of the bone’s is that they place the distal tip of a catheter proximal to the cortex. At this point, the Paramedic must make a forceful, but junction of the vena cava with the right atrium. Because of controlled, insertion into the bone with a twisting action. the high fl ow at the catheter’s distal tip, it is possible to infuse After removing the IO needle’s stylet, the Paramedic irritating or hypertonic solutions as well as inject normally should attach a sterile 10 mL syringe and attempt to aspi- incompatible drugs consecutively. rate bone marrow. The absence of bone marrow, a common The original central venous catheters, the Broviac® and occurrence, does not indicate that the IO needle is out of the the Hickman®, were developed during the 1970s and used bone. If the aspirate is unsuccessful, then a 10 mL bolus of extensively in the critical care areas. These skin-tunneled physiologic saline should be attempted. Use of a saline-fi lled devices exit the body in the vicinity of the right, or left, syringe during aspiration makes it easier to visualize the clavicle and have a medication access port for medication fl ash of bone marrow and blood. The saline, blood, and bone infusions. A central venous access device could remain 582 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. in place for fi ve to seven days, and potentially up to two weeks in special cases, thus avoiding the trauma of repeated needlesticks. The next generation of central venous access devices, the percutaneous central venous catheters (PCVC), were inserted into the deep veins via the subclavian vein (in the chest), the internal jugular vein (in the neck), and the femoral vein (in the groin). These central venous catheters have been developed with single-, double-, and triple-lumen catheters (Figure 27-32). Later CVAD models included an implanted port that was accessed from the outside by a special needle (described later) that could remain in place for even longer periods of time, an advantage during chemotherapy. The most recent addition to the line of central venous access devices is the peripherally inserted central catheter (PICC). The PICC is a very long catheter placed within a vein in the antecubital fossa and threaded into the vena cava Figure 27-33 PICC line used to administer while under fl uoroscopy. Subsequent radiographs of the chest antibiotics, at home, to a 12-year-old trauma are taken to confi rm placement of the PICC. Newer PICC patient who subsequently had developed devices are fi ber-optic. The progress of these newer fi ber- osteomyelitis. optic PICCs allows the provider to observe the progress of the catheter under the skin and into the vena cava. The ease Field-Placed Central Venous of placement, without fl uoroscopy, permits the insertion of a PICC in the physician’s offi ce, or in the fi eld. Access Device The PICC is rapidly becoming the CVAD of choice for The value of obtaining central venous access in the fi eld must patients who are at risk for hemorrhage, secondary to antico- be weighed against the dangers of CVAD placement. While agulants or low platelet counts (thrombocytopenia), or who the advantages of central venous access (e.g., during cardio- are immunocompromised. The site is easily accessible and vascular collapse) are impressive, the disadvantages, includ- visible (for infection surveillance) and compressible (in cases ing accidental arterial puncture with subsequent hemorrhage of hemorrhage). The PICC line, properly maintained, can and permanent nerve damage, can outweigh those advan- remain in place for over a year, and many patients are sent tages. For those reasons, CVAD placement in the fi eld is gen- home with a PICC in place (Figure 27-33). erally reserved for cases where a critical or cardiac arrested patient could clearly benefi t and the risks are outweighed by the benefi ts. The choice of the device is a function of the method of insertion. While the long catheter-over-the-needle CVAD may seem more familiar to the Paramedic, as it is similar to the regularly used peripheral intravenous access device, overinsertion of the long needle has serious implications for the patient, such as creation of a pneumothorax or accidental arterial puncture. An alternative CVAD is the catheter-through-the-needle device, described earlier in the chapter. This CVAD is less popular among Paramedics because the opening it creates in the vein is larger than the catheter that will pass through it. Subsequently, there can be hemorrhage at the site. This CVAD is reserved almost exclusively for use in compressible sites, such as the veins within the antecubital fossa. The preferred method of central venous access in the fi eld is the catheter-over-the-guidewire CVAD. This device starts with a smaller intravenous needle, which is familiar to Paramedics, and progresses to a larger catheter. The technique for inserting a catheter-over-the-guidewire will be described shortly. Although a variety of external central venous access Figure 27-32 Triple-lumen catheter, a central devices are available, each with a different number and/or venous access device. gauge of catheter, these catheters are generally either 20 cm Intravenous Access 583 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. long, for use in the subclavian or internal jugular vein, or 60 thigh rotated slightly. When the insertion site for the CVAD cm long, for femoral or basilac veins. has been identifi ed, it must be adequately prepared before proceeding with the needle insertion. While not a sterile pro- Placement of the Central Venous cedure, the insertion of devices into the central circulation Access Device (bypassing many of the body’s immune defenses in the pro- A number of sites are available for the placement of a central cess) requires strict medical asepsis. venous access device, and each has its drawbacks. The inter- The immediate area surrounding the area should be nal jugular vein (JV), while readily accessible, is in the same swabbed with a povidone-iodine or similar antiseptic solu- vicinity as other resuscitative efforts, such as intubation. This tion, starting at the intended point of insertion and moving makes it inconvenient. Furthermore, the proximity of the outward in ever-expanding, overlapping circles until an ade- carotid arteries to the internal jugular vein makes insertion of quate fi eld has been created (usually a 6- to 8-inch circle). If a needle into the internal jugular vein more problematic and the area is covered with hair, obscuring the insertion site, it an “overshoot” could cause arterial puncture. However, in the may be necessary to either clip the hair with scissors (pre- hands of an experienced operator, the IJV has the highest rate ferred) or shave the area. Excessive time should not be spent of success with the lowest incidence of complications.59 clearing the area of unwanted hair. The Paramedic would then An alternative location for a CVAD could be the sub- palpate for the femoral pulse with a gloved hand. The femoral clavian vein. Located inferior to the clavicle, the subclavian pulse should be located approximately 2 cm below the ingui- vein is proximal to the apex of the lung. An all-too-common nal ligament at the midpoint of the mental triangle. complication of a subclavian CVAD insertion is the creation Using the Seldinger technique, a catheter-over-the-wire of a pneumothorax. technique, the Paramedic will cannulate the femoral vein. Another complication of insertion, seen with the catheter- With a fi nger on the pulse, the Paramedic inserts the long over-the-wire approach, is the positioning of the wire inside 18g intravenous needle and catheter at a 30-degree angle, the heart. As the wire is literally whipped against the walls of approximately 1 cm medial to the femoral pulse, with the tip the heart with each contraction, it can create an ectopic beat aimed toward the head into the femoral vein. When the Para- and dysrhythmia. This site, like the IJV, is in proximity to medic observes a blood fl ash, the needle is stabilized with other resuscitative efforts. the nondominant hand and the needle withdrawn, leaving the The femoral vein is perhaps the safest site for the place- catheter in place. A special wire (a J-wire) is then inserted ment of a CVAD by an inexperienced operator. The topo- into the hub of the needle. The J-wire, a tightly wound spring graphic anatomy needed to identify the location of the femoral wire, has an open hook at the end, preventing it from punctur- artery is easy to locate. Therefore, the femoral vein can be ing soft tissues. cannulated without any serious interruption to either efforts Once the wire is in place, the needle is withdrawn. Dur- to intubate the patient or external cardiac compressions. How- ing the entire process, the Paramedic has a hold of either the ever, because the femoral CVAD lies below the diaphragm, needle or the J-wire. With the J-wire in place, a longer cath- it is not possible to measure accurate central venous pressure eter is placed over the wire and slid into position. After con- (CVP). This is generally not a priority in the out-of-hospital fi rmation of placement, the CVAD is secured in place and setting, whereas immediate venous access is a priority. fl uid fl ow rates adjusted accordingly (Skill 27-4). The femoral vein, like most deep veins, lies in a neuro- On occasion, a Paramedic may inadvertently misdirect vascular bundle, alongside the femoral artery and nerve. To the needle and puncture the adjacent femoral artery. If this locate the femoral vein, the Paramedic can trace its course occurs, and after the needle is withdrawn, a large dressing from the saphenous opening in the thigh to its terminus at the and direct pressure (with the palm of the hand, if necessary) inguinal ligament. The Paramedic should imagine a triangle, is applied to the area until the bleeding stops. a mental triangle, in the inguinal fold, with the femoral vein For a step-by-step demonstration of Obtaining a lying in the middle, within the femoral sheath. The femoral Femoral Line, please refer to Skill 27-4 on pages artery should be found, by palpation, just lateral to the vein, 591–592. and the femoral nerve lies lateral to the femoral artery (i.e., from inside to out, vein, artery, and nerve). Needle entry into the femoral vein is complicated by the presence of the super- Street Smart fi cial and deep fascia, a strong |
membranous sheath that pro- tects these important structures. If intra-abdominal or pelvic injuries are suspected, Preparation and Insertion then the risk of distorted anatomy and subsequent of a Femoral CVAD accidental arterial puncture, as well as increased To perform a femoral insertion of a catheter-over-the-wire bleeding in the area, make the femoral site CVAD, the Paramedic must fi rst position the patient supine, undesirable for central venous access. with the legs abducted approximately 30 degrees and the 584 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Access of a Central Venous c onsists of a reservoir, a hollow metal disk with a self-sealing Access Device membrane, and a silicone catheter. This population of patients frequently has a medical Peripherally inserted central catheters (PICC), percutaneous emergency and requires EMS assistance, including medica- central venous catheters, and tunneled central venous catheters tions and/or fl uids. If traditional peripheral venous access all have external ports that provide easy access for Paramedics cannot be obtained during an emergency, and it is impera- in the event of an emergency. To access these devices, the Para- tive to gain such access, the Paramedic may elect to access medic disconnects the catheter cap, connects a syringe, draws the IVAD. Some Paramedics have been specially trained by off approximately 3 mL to 5 mL of solution (either physiologic oncology nurses or oncology specialists to access the IVAD saline or heparin), maintains the patency of the catheter, and during an emergency. discards the drawn off waster. Then the Paramedic connects the To access an IVAD, the Paramedic must fi rst locate the device intravenous administration set and adjusts the fl ow. in either the upper chest or upper arm. Once located, the skin If the catheter cap is a self-sealing membrane, similar to a overlying the IVAD is prepared in the same manner as a periph- medication port, then it will be necessary to cleanse the cath- eral IV site. Once the site is prepared, the Paramedic opens all eter cap with povidone-iodine solution and then introduce a necessary equipment, prefi lls a saline-fi lled syringe, and attaches needle-tipped syringe (usually a 19g needle) to withdraw the it to a special non-coring needle called a Huber needle. discard. Subsequently, a needle will need to be attached to Donning sterile gloves, the Paramedic carefully picks the end of the intravenous administration set securely and the up the Huber needle, avoiding contamination, and holds the two mated. Many Paramedics reinforce the connection of the Huber needle with the dominant hand. Taking the gloved needle to the catheter cap with tape. nondominant hand, the Paramedic holds the subcutaneous The greatest concern with accessing these devices is port fi rmly, like holding a quarter on its side, and places the accidental disconnection that can result in massive hemor- needle over the skin (Figure 27-34). rhage and/or air embolism. To prevent this potentially fatal If the patient were a child, many Paramedics would pre- complication, most CVAD have luer lock fi ttings that con- pare the site with EMLA cream before the procedure. In the nect together tightly and/or self-sealing membranes (similar case of adults, after repeated access, a callous commonly to those on a medication port) that seal the catheter. forms over the site, and the needle inserted is relatively pain- The insertion of a CVAD is a costly and time-consuming less. With the needle poised over the port and perpendicular process and it is important to maintain the patency, and thus to the skin, the needle is advanced, with authority, until the the viability, of a CVAD for these reasons. The patency of a needle strikes the back plate of the port and stops. With the CVAD can be maintained by either continuous infusion or needle in place, the Paramedic fi rst checks for a blood return, intermittent infusions (e.g., with heparin solution). Most Para- then fl ushes the IVAD. medics prefer that, once access has been made into a CVAD, Similar to a CVAD, once the IVAD is accessed the Para- the patency of CVAD is maintained by a continuous infusion, medic has a choice between continuous infusion and intermit- running at KVO, until the patient arrives at the hospital. tent infusion. Most Paramedics elect to maintain a continuous Implanted Vascular Access Devices infusion and attach the intravenous administration set adaptor to the hub of the Huber needle. The entire assembly can then be For long-term venous access, a special implanted vascular secured with a transparent occlusive dressing, with or without access device (IVAD) is used. An IVAD is a central venous gauze, under the arm of the Huber needle to help stabilize it. catheter that has the port buried in a subcutaneous pocket under the skin’s surface. Implanting the entire device affords the IVAD the skin’s protection, which decreases the rate of infection, as well as protect the port from physical trauma. IVADs are generally reserved for patients who are going to receive intermittent infusions of irritating solutions for a prolonged period of time (e.g., chemotherapy). Infusion of these irritating solutions via traditional peripheral venous access would cause the veins to become infl amed (sclerosis) and hardened. Venous access to these hardened veins becomes increasingly diffi cult over time and the patient is often sub- jected to repeated attempts. IVADs eliminate the need to attempt, and to re-attempt, IV access on those patients who have a poverty of veins. Instead, the IVAD is accessed. The infusion is run through a plastic catheter and into the central circulation, where it can be diluted. Figure 27-34 IVAD access with a Huber needle. The subcutaneous port of an IVAD may be implanted (Courtesy of Emergency Preparedness Systems, LLC and EMS in either the upper chest wall or the upper arm. The port Magazine) Intravenous Access 585 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Skill 27-1 Preparation of an Intravenous Administration Set 1 Select solution, checking for solution type, clarity, and expiration. 2 Select intravenous administration set, choosing between micro- drop and macro-drop. 3 Place the roller clamp just proximal to drip chamber and stopped. 4 Squeeze drip chamber, fi lling drip chamber one-half full. 5 Run solution out while maintaining sterility of end. 586 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Skill 27-2 Venous Cannulation Using a Catheter-Over-the-Needle Device 1 Apply the venous tourniquet and select the optimal site for 2 Cleanse the immediate area using appropriate antiseptic solution. cannulation. 3 Select appropriate venous catheter. 4 Visualize the insertion site (approach the site with authority). 5 Confi rm venous cannulation by looking for fl ashback in the 6 Slide the catheter over the needle into the vein. catheter. Intravenous Access 587 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Skill 27-2 ( continued) 7 Draw blood as appropriate and remove tourniquet. 8 Secure the IV catheter using a semipermeable membrane dressing. 588 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Skill 27-3 I ntraosseous Access 1 Identify the preferred site. 2 Prepare the site with antiseptic solution. 3 Approach the site with intraosseous needle, perpendicular 4 Aspirate to establish placement. to the bone. Intravenous Access 589 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Skill 27-3 ( continued) 5 Flush with saline, observing for infi ltration. 6 Attach administration set. 7 Secure IO access. 590 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Skill 27-4 O btaining a Femoral Line 1 Identify the femoral triangle. 2 Prepare the area with antiseptic solution. 3 Insert the needle and observe fl ash. 4 Thread the J-wire into the catheter. 5 Remove the catheter over the wire and hold the wire. 6 Introduce the dilator, then remove. Intravenous Access 591 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Skill 27-4 ( continued) 7 Thread the line over the wire, holding the line in one hand while 8 Attach the infusion set. threading with the other. 9 Dress the insertion site. 592 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Venous access for both fl uid replacement and medication administration during an emergency is critical. The Paramedic’s skill in obtaining venous access is often regarded as an indicator of the Paramedic’s capability. Without venous access, very little can be done to alleviate the patient’s suffering and lessen the pain. Key Points: • Body fl uids are distributed across three • After the correct solution has been chosen, the compartments: the intravascular space, intracellular Paramedic must verify that the solution is in date, compartment (ICF), and as extracellular fl uid (ECF) clear, and intact. in the interstitial space. • The intravenous administration set provides a sterile • Indications for intravenous access include pathway for the intravenous fl uid to get from the medication administration and the replacement of container into the patient. intravascular volume. • A macro-drop administration set is often used when • Fluid loss may be insensible (such as perspiration volume replacement is |
needed. and vapor on the breath) or sensible (such as urine, GI fl uid loss, and wound drainage). • A micro-drop administration set is used for fi ne control of the infusion stream. • Pre-existing medical conditions that can contribute to increased fl uid loss include diabetes insipidus, • An administration set consists of a spike that pierces emphysema, hyperglycemia, and the alcoholic the fl uid container and a drip chamber where a patient. Decreased levels of responsiveness, hanging drop is formed. tachypnea, tachycardia, hypotension, or postural • A specifi c rate of fl ow may be established by hypotension may indicate a signifi cant loss of adjusting the fl ow to the required drops per minute. intravascular volume secondary to dehydration. • • The drip rate control device, slide clamp, and Crystalloid fl uids contain electrolytes commonly medication administration ports are located along found in the blood, while fl uids containing proteins the length of tubing, which is then connected to a are called colloids. catheter via an adaptor. • A balanced or isotonic solution has a percentage of • Trauma tubing has a larger internal diameter, solute similar to what is found in blood. allowing the rapid administration of large volumes • A solution that draws water out of the cell by of solution. Other infusion sets include large-bore osmotic force, due to a greater percentage of solute tubing found in blood transfusion sets and in-line than blood, is a hypertonic solution. burettes that are used to carefully control fl uid infusion, often used with pediatric patients. • A solution that has fewer solutes than blood, causing water to be drawn into the cells, is a • A pressure bag will increase the fl ow rate by hypotonic solution. exerting direct pressure onto the solution bag. • Intravenous access bypasses many of the body’s • Connecting and priming the administration set, or defenses against infection, so the Paramedic has the running the line out, begins by clamping off the line responsibility to take all reasonable precautions to and inserting the spike into the port of the solution. prevent blood infection. Fluid is then drawn into the drip chamber and the fl uid Intravenous Access 593 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. is run through the length of tubing. Venous access is • Venous cannulation can be performed by the direct divided into peripheral access and central access. approach by placing the IV needle atop the vein. • The indirect approach involves inserting the IV The smaller the gauge of an intravenous needle, the needle under the skin and next to the vein, and then larger the needle. directing the needle into the vein. The catheter must • A larger gauge needle is preferred for trauma be advanced into the vein to ensure placement. patients while a smaller gauge needle reduces the • When the needle is completely withdrawn, it must risk of thrombophlebitis and can be maintained for be immediately rendered safe. Some IV needles are a longer period of time. self-sheaving whereas others are not. Regardless of • The most common IV access device used is the the presence of any engineered safety devices, all needle-through-the-catheter variety. IV needles should be immediately placed in a sharps container. • Two other IV access devices include butterfl y IV catheters and needle-over-the-catheter devices, • The entire time for insertion should be approximately which are used almost exclusively for central venous two minutes, from the time the tourniquet was access in the hospital setting. applied to the time the tourniquet was released. Proper preparation of supplies, preassembled as • Whenever an intravenous access is attempted, a necessary, helps to improve overall effi ciency. sharps container should be immediately available (i.e., within arm’s reach of the Paramedic). • The IV administration set can be attached to the IV catheter and run continuously or intermittently. • A venous tourniquet should not remain in place for more than a few minutes and the distal • A saline lock can be used to cap off the IV catheter arterial pulse should remain palpable at all times. for later use. Tamponade of a vein, or manual compression of a • The IV catheter can be secured with tape and/or a vein, can achieve a similar effect. transported membrane dressing. • Venous access points of the upper extremity include • Several types of mechanical fl ow control devices the dorsal arch of the hand, cephalic and basilic may be used to accurately control intravenous fl ow. veins along the forearm, the cubital arch in the antecubital space, and the axillary vein in the upper • Complications of IV infusions include infi ltration, arm. Access points in the lower extremity include infusion-induced hypothermia, infection that may the saphenous veins. The external jugular vein may cause thrombophlebitis and/or pyrogenic reactions, also be accessed in an emergency. fl uid volume overload, or embolisms. • Venous site selection includes knowledge of hand • Infusing fl uids into the intraosseous space ultimately dominance, potential future procedures, past infuses fl uids into the central veins. surgical interventions, or current medical or trauma history. • Indications for IO access include cardiac arrest or the need for immediate access for medication • The Paramedic must assess and select a primary and administration. secondary IV site. • Complications of IO insertion include the risk • The Paramedic should clean the selected site by of fat embolism, fracture, extravasation, and placing the alcohol or povidone-iodine swabs on compartment syndrome. the intended insertion site and sweep outward in expanding and ever-widening circles, creating a • The majority of prehospital medications can be sterile fi eld twice the length of the IV needle. administered via the IO route except for 9% saline and adenosine. • The Paramedic should not re-palpate the intended IV access site once the preparation has begun. • Phlebotomy is performed when a blood sample is required but IV access is not necessary. Phlebotomy 594 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. is carried out using a straight needle and a vacuum • Pediatric intraosseous access provides vascular tube apparatus. access directly into the central circulation, can be • established quickly, and remains available even To prevent potential contamination from additives, during cardiac arrest. the tubes without additives (red-topped tubes) are drawn fi rst and the “wet” tubes (those with • Common complications include misplacement of the additives) are drawn last. needle, inadvertent puncture of the posterior wall • of the bone, and extravasation of fl uids into the When transporting samples, all potentially tissues. infectious materials (PIM) must be clearly marked with the biohazard symbol or some other warning • The IO site of choice is the proximal tibia. Like that indicates the presence of PIM. peripheral venous access, the IO needle cannot be • placed into an extremity with a fractured bone. Drawing blood cultures is a specialized technique that requires medical asepsis to prevent • Central venous access provides a route for contamination of the sample. medication administration as well as the • measurement of central venous pressure (CVP). Specialized phlebotomy techniques are used with pediatric patients. A heel stick may be used to draw • Central venous access devices include percutaneous blood from infants. A smaller needle, 25g to 27g central venous catheters (PCVC) that are inserted butterfl y, is used along with a syringe to gradually into deep veins and the peripherally inserted draw the sample from the vein. central catheter (PICC). • The umbilical catheter is advanced throughout the • For long-term central access, a patient may have an umbilical vein, the larger orifi ce. implanted vascular access device (IVAD). To access • this device, the Paramedic needs a special non- Scalp veins may also be used for IV access on infant coring needle called a Huber needle. patients. Review Questions: 1. Name the indications for venous access. 9. Starting proximal and moving distal, identify 2. What is a crystalloid solution? and describe the veins that may be used to 3. What role does the amount of solute play in the establish intravenous access. movement of water? 10. State the similarities and differences between 4. Describe insensible loss of fl uid and its intravenous access and phlebotomy. relationship to the disease process. 11. What precautions should be taken when 5. What clinical signs indicate dehydration? selecting an intravenous access site? 6. What type of intravenous administration 12. Describe the procedure for performing a set would you select for a trauma venipuncture. patient? Why? 13. Describe methods of securing the IV catheter. 7. Name the components of an administration set. 14. How is a secondary intravenous infusion 8. What are the steps to prepare a solution and prepared and set up? intravenous administration set? 15. What signs and symptoms would indicate a pyrogenic reaction? Intravenous Access 595 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. 16. Name the three basic vacuum blood tubes and 18. What are the indications for placement of an for which tests each is indicated. implanted central access device? 17. Describe age-appropriate methods of 19. What sites exist for an implanted central access establishing an IV for infants, toddlers, school- device? aged children, and adolescents. Case Study Questions: Please refer to the Case Study at the beginning of the 2. If you were unable to initiate an IV in her upper chapter and answer the questions below: extremities, what other sites exist that you can try? 1. Where would you look fi rst for access on 3. What other methods may be appropriate for Mrs. Gorino? Explain your answer. access? References: 1. Reithner L. Insensible water loss from the respiratory tract in 14. Zamos DT, Emch TM, Patton HA, D’Amico FJ, Bansal SK. patients with fever. Acta Chir Scand. 1981;147(3):163–167. Injection rate threshold of triple-lumen central venous catheters: 2. Lamke LO, Nilsson G, Reithner L. The infl uence of elevated an in vitro study. Acad Radiol. 2007;14(5):574–578. body temperature on skin perspiration. Acta Chir Scand. 15. Dutky PA, Stevens SL, Maull KI. Factors affecting rapid fl uid 1980;146(2):81–84. resuscitation with large-bore introducer catheters. J Trauma, 3. David K. IV fl uids: do you know what’s hanging and why? Rn. 1989;29(6):856–860. 2007;70(10):35–40; quiz 41. 16. Krivchenia A, Knauf MA, Iserson KV. Flow characteristics of 4. Soreide E, Deakin CD. Pre-hospital fl uid therapy in the critically admixed erythrocytes through medex tubing with a pall fi lter. injured patient—a clinical update. Injury. 2005;36(9):1001–1010. J Emerg Med. 1988;6(4):269–271. 5. Roberts I, Alderson P, Bunn F, Chinnock P, Ker K, Schierhout G. 17. Merrer J, De Jonghe B, Golliot F, Lefrant JY, Raffy B, Barre Colloids versus crystalloids for fl uid resuscitation in critically ill E, et al. Complications of femoral and subclavian venous patients. Cochrane Database Syst Rev. 2004;4:CD000567. catheterization in critically ill patients: a randomized controlled 6. Fan E, Stewart TE. Albumin in critical care: SAFE, but worth its trial. Jama. 2001;286(6):700–707. salt? Crit Care. 2004;8(5):297–299. 18. Hagley MT, Martin B, Gast P, Traeger SM. Infectious and 7. Perel P, Roberts I. Colloids versus crystalloids for fl uid mechanical complications of central venous catheters placed by resuscitation in critically ill patients. Cochrane Database Syst percutaneous venipuncture |
and over guidewires. Crit Care Med. Rev. 2007;4:CD000567. 1992;20(10):1426–1430. 8. Fodor L, Fodor A, Ramon Y, Shoshani O, Rissin Y, Ullmann 19. Karapinar B, Cura A. Complications of central venous Y. Controversies in fl uid resuscitation for burn management: catheterization in critically ill children. Pediatr Int. literature review and our experience. Injury. 2006;37(5):374–379. 2007;49(5):593–599. 9. Hemington-Gorse SJ. Colloid or crystalloid for resuscitation of 20. Rivera AM, Strauss KW, van Zundert AA, Mortier EP. Matching major burns. J Wound Care. 2005;14(6):256–258. the peripheral intravenous catheter to the individual patient. Acta 10. Kreimeier U, Messmer K. Small-volume resuscitation: from Anaesthesiol Belg. 2007;58(1):19–25. experimental evidence to clinical routine. Advantages and 21. Frelich R, Ellis MH. The effect of external pressure, catheter disadvantages of hypertonic solutions. Acta Anaesthesiol Scand. gauge, and storage time on hemolysis in RBC transfusion. 2002;46(6):625–638. Transfusion. 2001;41(6):799–802. 11. Guisto JA, Iserson KV. The feasibility of 12-gauge intravenous 22. Gerberding JL. Management of occupational exposures to blood- catheter use in the prehospital setting. J Emerg Med. borne viruses. N Engl J Med. 1998;332(7):444–451. 1990;8(2):173–176. 23. Kistner RL, Kamida CB. 1994 update on phlebography and 12. Stoneham MD. Factors affecting fl ow through blood varicography. Dermatol Surg. 1995;21(1):71–76. administration sets. Eur J Anaesthesiol. 1997;14(3):333–339. 24. Stone MB, Price DD, Anderson BS. Ultrasonographic investigation 13. Elad D, Zaretsky U, Heller O. Hydrodynamic evaluation of of the effect of reverse Trendelenburg on the cross-sectional area of intravenous infusion systems. Ann Emerg Med. 1994;23(3):457–463. the femoral vein. J Emerg Med. 2006;30(2): 211–213. 596 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. 25. Parry G. Trendelenburg position, head elevation and a midline 42. Tagalakis V, Kahn SR, Libman M, Blostein M. The epidemiology position optimize right internal jugular vein diameter. Can J of peripheral vein infusion thrombophlebitis: a critical review. Am Anaesth. 2004;51(4):379–381. J Med. 2002;113(2):146–151. 26. Goldstein AM, Weber JM, Sheridan RL. Femoral venous access 43. Moore TM, Callaway CW, Hostler D. Core temperature cooling is safe in burned children: an analysis of 224 catheters. J Pediatr. in healthy volunteers after rapid intravenous infusion of 1997;130(3):442–446. cold and room temperature saline solution. Ann Emerg Med. 27. Murr MM, Rosenquist MD, Lewis RW, 2nd, Heinle JA, Kealey 2008;51(2):153–159. GP. A prospective safety study of femoral vein versus nonfemoral 44. Soreide E, Grande C. Prehospital Trauma Care. New York; vein catheterization in patients with burns. J Burn Care Rehabil. Informa Health Care; 2001:357–367. 1991;12(6):576–578. 45. Iserson KV. Intraosseous infusions in adults. J Emerg Med. 28. Stitik TP, Foye PM, Nadler SF, Brachman GO. Phlebotomy- 1989;7(6):587–591. related lateral antebrachial cutaneous nerve injury. Am J Phys 46. Buck ML, Wiggins BS, Sesler JM. Intraosseous drug Med Rehabil. 2001;80(3):230–234. administration in children and adults during cardiopulmonary 29. Orme RM, McSwiney MM, Chamberlain-Webber RF. Fatal resuscitation. Ann Pharmacother. 2007;41(10):1679–1686. cardiac tamponade as a result of a peripherally inserted central 47. Findlay J, Johnson DL, Macnab AJ, MacDonald D, Shellborn venous catheter: a case report and review of the literature. Br J R, Susak L. Paramedic evaluation of adult intraosseous infusion Anaesth. 2007;99(3):384–388. system. Prehosp Disaster Med. 2006;21(5):329–334. 30. Greenfi eld RH, Bessen HA, Henneman PL. Effect of crystalloid 48. Miller DD, Guimond G, Hostler DP, Platt T, Wang HE. Feasibility infusion on hematocrit and intravascular volume in healthy, of sternal intraosseous access by emergency medical technician nonbleeding subjects. Ann Emerg Med. 1989;18(1):51–55. students. Prehosp Emerg Care. 2005;9(1):73–78. 31. Lobo DN, Stanga Z, Simpson JA, Anderson JA, Rowlands BJ, Allison 49. Suyama J. Knutsen CC, Northington WE, Hahn M, Hostler D. IO SP. Dilution and redistribution effects of rapid 2-litre infusions versus IV access while wearing personal protective equipment in of 0.9% (w/v) saline and 5% (w/v) dextrose on haematological a HazMat scenario. Prehosp Emerg Care. 2007;11(4):467–472. parameters and serum biochemistry in normal subjects: a double- 50. Fowler R, Gallagher JV, Isaacs SM, Ossman E, Pepe P, Wayne blind crossover study. Clin Sci (Lond). 2001;101(2):173–179. M. The role of intraosseous vascular access in the out-of- 32. Schulze T, Mucke J, Markwardt J, Schlag PM, Bembenek A. hospital environment (resource document to NAEMSP position Long-term morbidity of patients with early breast cancer after statement). Prehosp Emerg Care. 2007;11(1):63–66. sentinel lymph node biopsy compared to axillary lymph node 51. LaSpada J, Kissoon N, Melker R, Murphy S, Miller G, Peterson dissection. J Surg Oncol. 2006;93(2):109–119. R. Extravasation rates and complications of intraosseous 33. Rietman JS. Geertzen JH, Hoekstra HJ, Baas P, Dolsma WV, de needles during gravity and pressure infusion. Crit Care Med. Vries J, et al. Long term treatment related upper limb morbidity 1995;23(12):2023–2028. and quality of life after sentinel lymph node biopsy for stage I or 52. Soong WJ, Jeng MJ, Hwang B. The evaluation of percutaneous II breast cancer. Eur J Surg Oncol. 2006;32(2):148–152. central venous catheters—A convenient technique in pediatric 34. Ververs JM, Roumen RM, Vingerhoets AJ, Vreugdenhil G, patients. Intensive Care Med. 1995;21(9):759–765. Coebergh JW, Crommelin MA, et al. Risk, severity and predictors 53. Zempsky WT, Cravero JP. Relief of pain and anxiety in of physical and psychological morbidity after axillary lymph node pediatric patients in emergency medical systems. Pediatrics. dissection for breast cancer. Eur J Cancer. 2001;37(8):991–999. 2004;114(5):1348–1356. 35. Lambert MJ, 3rd. Air embolism in central venous catheterization: 54. Hurren JS, Dunn KW. Intraosseous infusion for burns diagnosis, treatment, and prevention. South Med J. resuscitation. Burns. 1995;21(4):285–287. 1982;75(10):1189–1191. 55. Curran A, Sen A. Best evidence topic report. Bone injection gun 36. Kashuk JL, Penn I. Air embolism after central venous placement of intraosseous needles. Emerg Med J. 2005;22(5):366. catheterization. Surg Gynecol Obstet. 1984;159(3):249–252. 56. Skippen P, Kissoon N. Ultrasound guidance for central vascular 37. Deitch EA, Dayal SD. Intensive care unit management of the access in the pediatric emergency department. Pediatr Emerg trauma patient. Crit Care Med. 2006;34(9):2294–2301. Care. 2007;23(3):203–207. 38. Mackinnon MA. Permissive hypotension: a change in thinking. 57. DeBoer S, Seaver M, Morissette C. Intraosseous infusion: not just Air Med J. 2005;24(2):70–72. for kids anymore. Emerg Med Serv. 2005;34(3):54, 56–63; quiz 119. 39. Dubick MA, Atkins JL. Small-volume fl uid resuscitation for the 58. Driggers DA, Johnson R, Steiner JF, Jewell GS, Swedberg far-forward combat environment: current concepts. J Trauma. JA, Goller V. Emergency resuscitation in children. The role of 2003;54(5 Suppl):S43–S45. intraosseous infusion. Postgrad Med. 1991;89(4):129–132. 40. Idvall E, Gunningberg L. Evidence for elective replacement of 59. Sneff M. Central venous catheters. In: Rippe JM, Irwin RS, peripheral intravenous catheter to prevent thrombophlebitis: a eds. Intensive Care Medicine (2nd ed.). Boston: Little Brown; systematic review. J Adv Nurs. 2006;55(6):715–722. 1991:17–37. 41. Katz SC, Pachter HL, Cushman JG, Roccaforte JD, Aggarwal S, Yee HT, et al. Superfi cial septic thrombophlebitis. J Trauma. 2005;59(3):750–753. Intravenous Access 597 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. KEY CONCEPTS: Upon completion of this chapter, it is expected that the reader will understand these following concepts: • Components and production of blood • Blood groups, compatibility, and cross-matching • Identifi cation and treatment of transfusion reactions • Specifi c transfusion procedures before, during, and after transfer Case Study: The Paramedics were called to the local community hospital for a trauma patient who needed to be transferred to the trauma center. The patient had a serious motorcycle crash and his friends dropped him off at the hospital rather than calling for an ambulance. Now it was storming and the helicopter was grounded due to bad weather. The local hospital had placed a chest tube to drain blood from the patient’s thoracic cavity and he was receiving multiple blood transfusions. He would need more during the transport. 598 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Blood Products and Transfusion 599 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. OVERVIEW Blood product transfusion can be a life-saving therapy for patients who are critically ill or injured. In certain situations, the Paramedic may be asked to transfer patients who are undergoing a transfusion during an interfacility transfer. The Paramedic may also be asked to transfuse additional blood products during the transfer. These types of situations are often heavily regulated by each state’s oversight body and regulations differ from state to state. It is important for the Paramedic to follow the regulations and protocols for her state and agency. This chapter will discuss the different blood products and the indications for transfusing those blood products. History of Transfusions In the 1940s and 1950s, scientists developed meth- ods to separate whole blood into components that could be The fi rst recorded transfusion took place in 1665, when English transfused separately, thus improving storage capability and physician Richard Lower started transfusing blood between longevity as well as allowing more directed treatment of a dogs in his experiments. In 1667, French physician Jean-Baptist patient’s defi ciencies. Plastic bags were developed that were Denis transfused approximately 9 ounces or 260 mL of blood safe to use in storing blood. These replaced the cumbersome from a sheep to a young male patient. This patient survived and breakable glass bottles that were used at the time. but was described as having urine “as black as soot” after the transfusion. Dr. Denis continued animal to human transfusions over the following six months. Late in the same year, animal Professional Paramedic to human transfusion was outlawed in France and several other countries after several deaths were attributed to reactions to the animal blood. Around this same time, early microscopists were Carl Walter and W. P. Murphy, Jr., introduced the examining blood under the early microscopes and describ- plastic bag for blood collection in 1950. ing the different components of blood. While Anthony van Leeuwenhoek (1632–1723) is often credited with discovering During the 1960s and 1970s, important advancements red blood cells, scientist Jan Swammerdam actually discovered were made in the development and identifi cation of specifi c blood cells in the late 1650s. components that could be used to prevent antibody formation, The fi rst human-to-human transfusion was performed treat hemophilia, and detect infections that could be transmitted in 1795 by Dr. Philip Physick, a surgeon in Philadelphia, by blood product transfusion. The issue of transfusion safety Pennsylvania. The case was not publicized and little infor- moved to the forefront during the mid to late 1980s after dis- mation is available about it. A little more than 20 years covering the HIV virus was transmitted through blood transfu- later, British obstetrician James Blundell performed the fi rst sion. This led to widespread testing. Currently, donated blood is known blood transfusion to treat severe postpartum hemor- tested for several infectious diseases (Table 28-1). Due to wide- rhage by transfusing the blood from a husband to his wife spread testing and donation procedures designed to minimize after delivery. risk of disease transmission, the risk of contracting HIV from a In 1901, Austrian physician Karl Landsteiner discovered blood donation ranges from 1 in 493,000 to 1 in two million.1 the existence of |
different proteins on red blood cells and was the fi rst to describe blood groups. The safety of blood transfu- sion improved as physicians began to match the patient’s blood Table 28-1 Infectious Diseases Tested group with the donor’s blood group. In addition, around the for in Donated Blood time of World War I methods were discovered to prevent blood • HIV-1 from clotting during storage. Researchers also discovered that blood could be stored at cooler temperatures, allowing its use • HIV-2 for a longer period of time after it had been collected from • Human T-lymphotropic virus (HTLV-1 and HTLV-2) a donor. The fi rst blood bank was created in anticipation of • Hepatitis B virus heavy casualties by U.S. Army physician Oswald Robertson • Hepatitis C virus when he collected and stored blood before the Battle of • West Nile virus Cambrai in World War I. Within 20 years, civilian blood banks • Treponema pallidum (causative agent of syphilis) began to develop in the United States and Europe. 600 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Blood Components Hematopoiesis is the manufacturing process the body uses to create the three main solid components of blood: red As the early microscopists discovered, whole blood is made blood cells (erythrocytes), white blood cells (leukocytes up of several components bathed in plasma (the liquid por- and lymphocytes), and platelets (thrombocytes). All three tion of blood). Scientists and physicians have studied blood of these major types of blood cells develop from the same over the last 400 years and have discovered the origin, struc- hemocytoblast (Figure 28-1), which is the generic stem cell ture, and function of these components. Each component has for blood cells. Blood cells are manufactured within the bone a unique function to carry out within the body. marrow of the long bones, pelvis, cranium, sternum, and Hemopoietic stem cell Rubriblast Myeloblast Monoblast Lymphoblast Megakaryoblast Prorubricyte Promyelocyte Promonocyte Prolymphocyte Promegakaryocyte Eosinophilic Neutrophilic Basophilic Rubricyte myelocyte myelocyte myelocyte Megakaryocyte Eosinophilic Neutrophilic Basophilic Large Metarubricyte metamyelocyte metamyelocyte metamyelocyte lymphocyte Metamegakaryocyte Eosinophilic Neutrophilic Basophilic Reticulocyte band cell band cell band cell Erythrocytes Eosinophils Neutrophils Basophils Lymphocytes Monocytes Thrombocytes Small T Small B Peripheral blood Granular leukocytes Agranular leukocytes Figure 28-1 Hematopoiesis is the production of the major blood cell types from the hemopoietic stem cell. Blood Products and Transfusion 601 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. vertebrae. The spleen, thymus, and lymph nodes are respon- blood cell if transfused into another person with a different sible for maturing certain white blood cells after production blood type. Blood compatibility is discussed more fully later in the bone marrow. in this chapter. Red blood cells, also known as erythrocytes, are small White blood cells, or leukocytes (Figure 28-3), func- doughnut-shaped cells which act to transport oxygen from tion as part of the immune system to react to foreign chal- the lungs to the cells (Figure 28-2). Hemoglobin, the com- lenges. There are three different subtypes of leukocytes— ponent of the red blood cell that binds to oxygen, is manu- basophils, neutrophils, and eosinophils—which react factured from iron. Each molecule of hemoglobin can bind against, and attach themselves to, certain types of infec- up to four molecules of oxygen. The physiology of oxygen tious organisms, whether bacterial, viral, or fungal. After delivery was discussed in Chapter 25. The surface of a red attaching to the foreign cells, these white blood cells blood cell contains proteins that produce antibodies to the red release toxic chemicals in an attempt to neutralize the invading organism. Macrophages are larger cells that attack and destroy the foreign invaders after the leukocytes iden- Red blood cells tify the foreign material. Another group of immune cells, called lymphocytes, are responsible for identifying foreign materials and developing antibodies against those foreign materials to allow enhanced immune system response dur- ing future infections. Platelets, or thrombocytes (Figure 28-4), are responsible for blood clotting. Platelets are attracted to a damaged blood vessel’s endothelium, the innermost layer of the blood ves- sel. Coagulation factors and other proteins attract other cir- culating platelets to the damaged area to build a plug that achieves hemostasis and stops bleeding from the damaged blood vessel. Coagulation factors are proteins which act to attract Figure 28-2 The erythrocyte. platelets to each other to build platelet plugs. Additionally, Granular leukocytes Basophil Neutrophil Eosinophil Nongranular leukocytes Lymphocyte Monocyte Figure 28-3 Leukocytes. 602 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Platelets Table 28-2 Normal Serum Blood Values Found in a Complete Blood Count (CBC) Component Normal Range Red blood cells 4.5–5.5 million per mL White blood cells 4,000–10,000 cells/mL Hemoglobin 13–16 g/dL (male) Figure 28-4 Platelets. 12–15 g/dL (female) Hematocrit 41%–50% (male) 36%–44% (female) coagulation factors are key to the production of fi brin and Platelets 100,000–450,000 platelets/mL fi brinogen, two materials that serve to solidify and stabilize the platelet plug, making it impermeable to liquid. The coag- Many of the blood components discussed are measured as ulation cascade (Figure 28-5) outlines the process the body part of a complete blood count (CBC) that is often performed uses to manufacture fi brin and fi brinogen. Most of the coagu- in the ED or physician’s offi ce (Table 28-2). The amount of lation factors are made in the liver, some of which depend on hemoglobin differs between males and females largely due vitamin K during the manufacturing process. Both congeni- to the females’ blood loss during normal menstrual cycles. tal and acquired defi ciencies of coagulation factors can cause The hematocrit measures the ratio between the volume of the diffi culty in clotting or spontaneous bleeding. solid components of blood compared against both its solid and Blood also has many other proteins that circulate liquid components, listed as a percentage (solid/total). throughout the system which serve multiple different func- tions. Some of these circulating proteins are the antibodies that help protect against infection, albumen that helps regu- Blood Products late blood volume, and hormones that act in a variety of ways Since the technique of fractionating blood into its individual on the body’s organs. The blood also transports nutrients and components was perfected in the 1950s and 1960s, transfu- other building block materials to the cells. sion of whole blood in civilian medicine has become uncom- mon. However, transfusion of whole blood is more frequent in the combat environment when large quantities of blood are Contact Activation Pathway required.2 The advantage of fractionating blood into its com- Activating ponents is more directed transfusion based on the patient’s factors specifi c needs as well as longer storage life for the compo- nents as opposed to whole blood. The four blood compo- 12 Tissue Factor Pathway nents most frequently transfused include packed red blood Activating cells (PRBC), fresh frozen plasma, cryoprecipitate, and 11 factors platelets. Packed Red Blood Cells 9 7 PRBCs are formed by removing nearly all of the plasma from a unit of blood and adding a small volume of preservative to the unit. PRBCs are often stored at near freezing temperatures 8 but can be frozen for longer-term storage. Each unit of blood 10 is approximately 250 mL in volume, which includes both the solid and liquid component of the unit. Assuming bleeding is 5 Common Pathway controlled and does not continue during the transfusion, each unit of blood is expected to raise the patient’s hemoglobin by 2 1 gm/dL.3 PRBCs are transfused primarily in the situation of acute Fibrinogen Fibrin blood loss (e.g., in bleeding from trauma or from gastroin- testinal bleeding). PRBCs are also transfused to patients who are anemic, those with a signifi cantly decreased hemoglobin Vitamin K dependent level, and those who have signs and symptoms of impaired factors oxygen delivery (e.g., dyspnea, lightheadedness, or chest Cofactors pain). Anemic patients with known cardiac disease may also be transfused to ensure suffi cient oxygen delivery and pre- Figure 28-5 The coagulation cascade. vent cardiac events due to each patient’s anemia. Each unit Blood Products and Transfusion 603 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. of PRBCs can be transfused in as little as several minutes Platelets in critically ill, hypotensive patients with acute blood loss, Platelets are separated from plasma in the blood bank by one and up to two to four hours for patients who have poor car- of two methods. In order to raise the patient’s platelet count diac function. Most often, PRBCs are transfused at a rate of by 50,000 platelets, the patient needs to receive approximately approximately one unit per hour to two hours. However, in six units of platelets, which can be a signifi cant amount of severely hypotensive patients, a unit of PRBCs can be trans- volume. Each unit of platelets should be transfused over a 30 fused in a matter of minutes. to 60 minute time period. The indications for platelet transfu- At times, the patient requires so much blood that addi- sion vary based upon the patient’s platelet count, presence tional blood components are required. The term “mas- of bleeding, or risk of bleeding with a planned procedure. sive transfusion” is used to describe a situation in which Platelets are often transfused in patients undergoing massive a patient has signifi cant ongoing blood loss to the point transfusions as they are usually defi cient in platelets. Platelet where one to two body volumes of blood are required. transfusions may not be effective in conditions where platelet For the average weight person, this translates to a transfu- function is decreased (e.g., in renal disease).4 sion of 10–20 units of PRBCs. In situations in which the total blood volume needs replacement, other components which are absent in PRBCs—including platelets and coag- Blood Groups and Compatibility ulation factors—will also need to be replaced in order to Early transfusions caused reactions in an inconsistent man- prevent continued bleeding due to loss of the blood’s clot- ner. Some transfusions occurred without problems. In others, forming ability. the recipient had severe and sometimes fatal reactions. It was not until the early 1900s that a physician researcher, Dr. Karl Fresh Frozen Plasma Landsteiner, discovered that red blood cells have proteins Fresh frozen plasma (FFP) is formed by removing the red on the cell’s surface that are responsible for producing some blood cells and platelets from whole blood. The remaining transfusion reactions. This section will discuss the concept of liquid component of the blood is still rich in several of the blood grouping and matching donor blood to the recipient. clotting factors needed as part of the coagulation system. Two of these key coagulation factors are factors V and VIII. One Blood Grouping unit of FFP has a volume of approximately 200 mL and is The proteins that exist on the surface of the red blood cells transfused in 30 to 60 |
minutes. help the body identify which cells are its own cells as opposed FFP is most often used to treat clotting disorders which to foreign invaders. If a donor has different proteins on the accompany several diseases that include decreased clotting surface of donated blood products, the recipient’s immune factor production (e.g., liver disease). FFP is also used to system will identify those components as foreign material, treat patients who have taken an overdose of the anticoagu- and set off an immunological chain reaction that will lead to lant warfarin because of its action in inhibiting the production the clumping together of red blood cells, called agglutina- of clotting factors. FFP is also used to treat a condition called tion. The clumping causes the red blood cells to break apart, disseminated intravascular coagulation, in which the clotting a process called hemolysis (Figure 28-6). factors are rapidly used up and the patient develops bleeding Dr. Landsteiner identifi ed the existence of two proteins—an because of the clotting factor defi ciency. A protein and a B protein—on the surface of red blood cells. Red blood cells that have the A protein on the surface are called Cryoprecipitate Type A blood. If the B protein is present on the surface of the red Cryoprecipitate is the protein portion of plasma made up of blood cell, the blood is Type B blood. He also noticed that some concentrated clotting factors in a much smaller volume than red blood cells do not have either an A or a B protein on the FFP. One unit of cryoprecipitate has a volume of between 25 surface. Cells without these proteins were called Type O blood. and 50 mL, much less than one unit of FFP. Cryoprecipitate is The A-B-O designations formed the fi rst system of determining transfused between 15 and 30 minutes per unit. Cryoprecipitate blood type. At a later time, it was observed that some red blood contains factors V, VIII, and XIII. Additionally, cryoprecipi- cells have both an A and a B protein on their surface, and thus tate contains fi brinogen and fi bronectin, proteins that help the blood type is called Type AB blood, the fourth major blood solidify a clot, and von Willebrand factor, which helps to ini- group in the A-B-O typing scheme (Figure 28-7). tiate clot formation. These surface proteins are also antigens, meaning that Cryoprecipitate is indicated in overanticoagulation or they can produce an immune system response. Patients with disseminated intravascular coagulation. It is also indicated in Type A blood have antibodies against Type B blood in their patients who have hemophilia A or von Willebrand’s disease plasma. Conversely, patients with Type B blood have antibod- who are bleeding, as it quickly replaces the defi cient factor. ies to Type A blood in their plasma. Patients who have Type Cryoprecipitate is also used when patients are receiving a O blood have antibodies to both Type A and B blood in their massive transfusion to replace coagulation factors that are system and patients with Type AB blood do not have any of lost and not present in PRBC units. these antibodies in their system. As previously described, 604 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. + Figure 28-6 Agglutination and hemolysis occur when cells of incompatible blood types are mixed together. A B Table 28-3 The Frequency of Blood Type A antigen B antigen in the United States Based on the A-B-O and Rh Systems5 A-B-O and Rh Frequency O 37.4% B antibody A antibody O 6.6% A 35.7% AB O B antigen A 6.3% B 8.5% B 1.5% A antigen A antibody AB 3.4% B antibody AB 0.6% Figure 28-7 The major red blood cell types. Table 28-4 Examples of the 29 Different Blood Grouping Systems Recognized by the ISBT these antibodies are responsible for the agglutination and • A-B-O hemolysis of foreign blood cells. • Rh Dr. Landsteiner also discovered a second protein that • MNS existed along with the A and B proteins. This protein, the Rh factor, was named after the Rhesus monkey, whose blood • Lewis was used for the experiments that led to the discovery of the • Duffy Rh factor. The Rh factor is either present or absent, which • Kidd is denoted by adding a plus () or minus () to the A-B-O • Diego type. Patients with Rh blood do not have antibodies against • Cartwright the Rh protein; however, some patients with Rh blood have developed antibodies against the Rh protein and can develop a transfusion reaction. Between these two typing systems, the recipient’s and donor’s blood, the more compatible they there are eight major blood types that exist (Table 28-3). are and the less likelihood of severe transfusion reaction. As In addition to the major A-B-O and Rh blood types, previously discussed, blood of a certain type will often have the International Society of Blood Transfusion (http://www antibodies present that attack other types of blood. A recipi- .isbt-web.org/) recognizes a total of 29 different groups used ent may be able to safely receive other types of blood if the for blood typing. The 27 other typing schemas were classifi ed recipient’s type of blood is not available (Table 28-5). Notice by identifying other minor proteins that occur on the surface that Type O blood can be given to any of the A-B-O blood of blood cells which also cause immunological reactions when types because Type O blood does not have surface proteins different types of blood are mixed together (Table 28-4). that incite the immune response which ends in hemolysis. Compatability Type O blood is sometimes termed the universal donor due to this property. In contrast, patients with Type AB blood can As blood grouping was discovered and testing became avail- receive blood from any donor because the patient does not able, every effort was made to decrease the likelihood of a have antibodies against A or B proteins present in the plasma. severe transfusion reaction by matching the recipient’s blood Due to this property, individuals with Type AB blood are with potential donor’s blood. The greater the match between called universal recipients. Blood Products and Transfusion 605 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Table 28-5 Who Can Receive What Blood Types? same A-B-O and Rh types as the recipient’s blood, even If the Recipient Has Type: The Recipient Can Receive: though it has not been completely cross-matched. This often occurs when blood is required emergently while the A blood Type A and O blood blood bank is in the middle of the cross-matching process. B blood Type B and O blood All efforts to use cross-matched blood for subsequent units O blood Type O blood only of blood products are made once the uncross-matched or AB blood Type A, B, AB, and O blood only type-specifi c blood is used on a patient. Patients receiving Rh blood Type Rh or Rh blood uncross-matched or type-specifi c blood must be monitored Rh blood Type Rh blood only closely for transfusion reactions. Identifi cation and Management Cultural / Regional differences of Transfusion Reactions Transfusion reactions vary from minor to life-threatening. Some religious groups refuse blood transfusions due The Paramedic must be able to confi dently identify and treat to their belief that it is specifi cally forbidden. Courts the wide range of potential transfusion reactions that may have been asked to order blood transfusions in cases occur during transfer. of vulnerable populations such as children. Overruling a patient’s or family’s religious beliefs is not done Street Smart lightly. Some transfusion reactions can occur with as little Transfusion Terms as 10 mL of blood transfused. However, most tend to occur by the time the fi rst unit has fully transfused. Several terms are used to refer to the different blood products regarding their types and compatibilities. It is important for the Paramedic to understand these terms as it may impact the Transfusion-Associated transfusion process. Circulatory Overload During this process, which typically takes a half hour to accomplish, the blood bank uses a sample of the recipient’s Transfusion-associated circulatory overload (TACO) occurs blood and identifi es antibodies present in the sample. Using when the patient receives more volume of blood products than this information, the blood bank can fi nd a blood match that can be handled by the circulatory system. This overload essen- does not have antigens which will react with the antibodies in tially produces pulmonary edema and is more likely to occur in the recipient’s blood. In some cases, the recipient has numerous patients with impaired cardiac function, including the elderly, antibodies present in the blood and a prolonged time is required those with underlying CHF or coronary artery disease, or pedi- in order to identify blood for transfusion. In more complicated atric patients. It is important to note that a signifi cant amount cases, suffi ciently matched blood may need to come from of volume is infused into any patient, including those who are another center or blood bank in order to be safe for transfusion. healthy with normal heart and kidney function, and that TACO Donor blood that is successfully matched to recipient blood is can develop. As previously discussed, each unit of PRBCs is called type and crossed or type and cross-matched blood. a volume of 250 mL. Blood products are always run together In some cases, there is insuffi cient time to complete a with a second saline infusion running at a to-keep-open rate cross-match of recipient and donor blood. In cases of severe so the intravenous line does not clot off at the end of the trans- shock from acute blood loss (e.g., trauma, gastrointesti- fused unit. In addition to the 250 mL in the unit of blood, up to nal bleeding), a patient may require an immediate blood another 100 mL of normal saline is infused per unit of blood transfusion in order to sustain life. In these cases, uncross- product. As most critically ill patients requiring transfusion are matched blood is transfused using either O or O donor given several units of blood or blood products, it is easy to pro- blood that does not undergo the usual cross-matching pro- vide a signifi cant amount of volume in a short period of time. cedure. In general, O blood is preferred for women of To address this issue, patients at risk of circulatory overload childbearing age to avoid the development of antibodies to should be transfused at a slower rate than normal. Rh blood that may be transfused into the recipient with an unknown blood type. This is important because during Allergic Reaction a subsequent pregnancy, the maternal antibodies can attack Allergic reactions can occur due to MAST cell activation in the fetal blood cells, potentially resulting in fetal death. the recipient’s blood once exposed to the donor’s blood, and In some cases, the patient’s blood type is known and it are seen in up to 1% of transfusions.6 The allergic reactions is possible to administer type-specifi c blood that has the can range in severity from a mild reaction that includes itching 606 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time |
if subsequent rights restrictions require it. or some hives to anaphylaxis and airway edema. Most allergic every 500,000 units of PRBCs.7 The higher incidence of bac- reactions of this type will resolve spontaneously. Some reac- terial contamination of platelets is due to the higher tempera- tions will require administration of medications or slowing of ture at which platelets are stored. Contamination is rarely due the transfusion. Severe allergic reactions will defi nitely require to an illness in the donor. More often, it is due to contamina- medication treatment and may require airway management. tion which occurred during the collection or storage process. The patient may become septic due to the contamination, Febrile Non-Hemolytic Reaction though most often the patient exhibits signs of an infection, Febrile transfusion reactions are defi ned as an elevation of the including fever, chills, and rigors. Patients may also develop patient’s temperature of 1°C from baseline within two hours of dyspnea, hypotension, nausea, vomiting, or diarrhea. the start of the transfusion.6 A febrile non-hemolytic reaction more often begins shortly after the initiation of the transfusion or Transfusion-Related a new unit and is often secondary to minor antibodies present in Acute Lung Injury the recipient’s blood that cause a mild reaction when exposed to Transfusion-related acute lung injury (TRALI) is defi ned the donor’s blood. In addition to fever, the patient may develop as a new acute lung injury that occurs within six hours of chills, rigors, headache, nausea, or vomiting. The fever may a transfusion and is directly related to the transfusion.8 The resolve spontaneously, but often an antipyretic (e.g., acetamino- patient develops hypoxemia, dyspnea, and bilateral infi l- phen) is administered to treat the symptoms. If the fever persists trates that can be best seen on a chest x-ray in the ED but or elevates, the transfusion may need to be stopped. may produce bilateral rales (crackles) on auscultation by the Paramedic. TRALI occurs as a result of pulmonary capillary Acute Hemolytic Reaction leakage of plasma into the tissues surrounding the alveoli in An acute hemolytic reaction is one of the most serious the lung. It is believed that TRALI is set off by antibodies transfusion reactions and most often occurs as a result of against white blood cells present in the donor’s blood that an A-B-O incompatibility (Table 28-6). In other words, an react with the recipient’s white blood cells. Less frequently, incorrect blood type was administered to the patient; for the recipient’s blood contains the antibodies that attack white example, Type A blood was administered to a patient who blood cells that may be present in the donor unit of blood. has Type B blood. This produces agglutination and hemolysis The antibodies set off an infl ammatory reaction that produces of the transfused blood. The hemolysis may involve native compounds with the end result of leakage of plasma from red blood cells. Around 10% of patients who are exposed to the pulmonary capillaries. Alternatively, other infl ammatory A-B-O incompatible blood die of the hemolytic reaction. proteins may be present in the donor’s blood that causes the The administration of the wrong type of blood to a patient infl ammatory reaction in the recipient’s lungs (Table 28-7). can occur for several reasons, and an entire system of checks While TACO and TRALI may be diffi cult to differentiate in and balances has been developed in order to minimize these the fi eld, TACO tends to produce a more frank pulmonary errors. It is of the utmost importance that the Paramedic take edema, whereas TRALI produces fi ner rales (crackles) with- on a personal responsibility to ensure that any units of blood out a signifi cant fl uid overload. products that are transported with the patient are correctly labeled. The procedure will be discussed further in a later Treatment of Transfusion Reactions section of this chapter. Ultimately, if the transfusion contin- Regardless of the transfusion reaction identifi ed by the ues, the patient can develop shock, renal failure, disseminated Paramedic, the fi rst key step is to stop the transfusion, change intravascular coagulation, and death. the tubing, and fl ush the line with normal saline. These actions will prevent a continued reaction to the blood product. The Bacterial Contamination unit of blood product and the line must be saved and given to Bacterial contamination of blood products is estimated to the blood bank at the receiving hospital for testing. Draw a occur at a rate of 1 in every 15,000 units of platelets and 1 in red or pink top tube from the patient for testing by the blood bank at the receiving hospital. The blood bank at the receiv- ing hospital will retest both the donor unit and the sample Table 28-6 Signs and Symptoms of an Acute Hemolytic Transfusion Reaction • Fever > 2°C above the patient’s baseline temperature Table 28-7 Signs and Symptoms of TRALI • Hypotension • Dyspnea • Dyspnea • Tachypnea • Pain at the site of the transfusion, back, and chest • Cyanosis • Hemorrhage and/or hemoglobinuria (dark-colored urine) • Fever • Nausea and vomiting • Tachycardia • Jaundice and icterus • Froth in the endotracheal tube Blood Products and Transfusion 607 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. from the recipient to ensure there is a match and identify any Table 28-8 Items to Confi rm Prior to Transport cross-matching errors. Contact on-line medical control to discuss the specifi c patient and develop a treatment plan as • Verify patient identity well as to decide whether to continue the transfusion. • Verify consent for transfusion or indication of reason for implied Administer supplemental high-fl ow oxygen if the patient consent is not already on supplemental oxygen. For the patient who • Verify the patient’s blood type (A-B-O and Rh) develops an allergic reaction, administer diphenhydramine • Verify transfusion orders: and methylprednisolone intravenously to treat the aller- Type of blood product gic reaction. For anaphylactic reactions with hypotension, Rate of administration severe dyspnea, or throat edema, administer epinephrine Order of administration (if multiple products) intramuscularly to treat the anaphylaxis. TACO is treated • For each unit hanging or carrying during transport, verify with by administering furosemide intravenously and applying another Paramedic, RN, physician, or mid-level provider: CPAP to support ventilation and off-loading of fl uid from Blood type of unit the lungs. Patients who develop TRALI will often require CPAP or intubation. Care is supportive and does not require Rh factor of unit medications. Patient ID label Unit expiration date Transfusion Procedure Donor unit number and patient information match and Documentation Having reviewed the different types of blood products and the indications for transfusion and transfusion reactions, the next section discusses the procedure for blood product trans- Street Smart fusion. These steps must be followed with every unit trans- fused. Remember, there is a mortality rate of 10% for patients The Paramedic should document what items were who receive mismatched blood products regardless of treat- verifi ed and with whom on the regular patient care ment. This is a very serious complication of blood product transfusion. record in addition to completing the blood bank record. Street Smart During the Transfer Blood is transfused through one of two types of administra- Hyperkalemia may occur due to infusions with tion sets. The blood transfusion set is preferred over the pig- gyback set (both described in Chapter 27) because the blood irradiated red blood cells. Hypocalcemia may administration set has a larger lumen, providing less resis- result from multiple transfusions due to the citrate tance to fl ow than a piggyback setup. The second advantage preservative binding serum calcium and is indicated of blood tubing is that both ports of the “Y” shaped tubing fl ow into the same drip chamber, allowing less resistance to by circumoral tingling and tremors. fl ow for the normal saline that is administered with the blood. Normal saline should be set to run at “to-keep-open rate” so Prior to Transfer it fl ushes the line with saline after the unit of blood product is fi nished. During the patient report received from the RN in the send- During transport, blood products must be stored in an ing facility, the Paramedic needs to confi rm several items appropriate transport cooler that is certifi ed by the blood bank before receiving the patient and blood products (Table 28-8). (Figure 28-8). This is essential as most blood products should These steps are important to ensure that the blood products be stored at a temperature between 1°C and 6°C. The shelf match the patient’s A-B-O and Rh factor and that only blood life of a unit of blood at room temperature is approximately products intended for that specifi c patient are transfused. 30 minutes. Warmer temperatures increase the risk of bacte- Ideally, the transfusion will have been initiated in the send- rial contamination as well as developing proteins in the donor ing emergency department and the patient monitored for 15 blood that can initiate transfusion reactions. to 30 minutes in order to identify major transfusion reactions The Paramedic should record vital signs, including tem- before transport. Review the pre-transfusion set of vitals, perature, at 15-minute intervals during transfer. Vital signs including a temperature, as some of the transfusion reactions should also be recorded after completing each unit. The rely on a change from baseline temperature in identifying Paramedic should auscultate the patient’s lungs between the reaction. units to identify signs of fl uid overload. This is especially 608 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Street Smart The Paramedic should evaluate the patient’s skin each time vital signs are obtained for indications of an allergic reaction. After the Transfer The Paramedic must document at a minimum vitals, times, reactions, and information about the blood products admin- istered to that patient during transfer. This information may be documented on a usual patient care report or a specifi c special form may be required. The Paramedic should use the specifi c form required by her agency. One copy of the transfusion record should be left at the receiving hospital and Figure 28-8 A transport cooler certifi ed by the another copy kept with the prehospital documentation. blood bank. (Courtesy of Thermosafe Brands, a Strategic Any unused blood products should be given to the blood Business Unit of Tegrant Corporation) bank at the receiving hospital. The blood is then retested and either used for the transferred patient or made available for others who match that donor’s blood. In the event of a transfu- important in intubated or sedated patients as they may not be sion reaction, the unit of blood that was hanging at the time of able to complain of dyspnea. A fi nal set of vital signs should the reaction, the blood tubing, and the patient’s blood sample be recorded on arrival to the receiving facility. should be brought to the blood bank for testing. Blood Products and Transfusion 609 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. The transfusion of blood products during critical care transport by the Paramedic can provide a life-saving therapy to the critically ill patient who requires |
blood products. It is important for the Paramedic to approach blood transfusions methodically and systematically in order to ensure patient safety during the transfusion. It is also critical to continuously monitor the patient during transfer so as to identify and treat transfusion reactions early. Key Points: • Refi nements in the process of giving blood from one • When no further blood loss occurs, a unit of packed red animal to another, and ultimately from one human cells will increase the hemoglobin levels by 1 gm/dL. to another, has been ongoing for over 400 years. • Fresh frozen plasma (FFP) is formed by removing cells • Blood groups are identifi ed by specifi c antigens from whole blood and is rich in several of the clotting located on the red blood cell. factors needed as part of the coagulation system. • Other proteins also affect blood compatibility. • Cryoprecipitate is the protein portion of plasma made up of concentrated clotting factors. • Donated blood is tested for multiple infectious diseases. • Platelets may be transfused in patients undergoing massive transfusions. • Whole blood consists of solid components (red and white blood cells plus platelets) and plasma. • There are eight major blood types: ■ Type O positive or negative • Hematopoiesis is the process that the body uses for ■ Type A positive or negative the development of solid blood components. ■ Type B positive or negative • ■ Type AB positive or negative All blood cells develop from a hemocytoblast. • Blood cells are manufactured within the bone • Type O blood is called the universal donor as it does not have surface proteins that trigger an marrow of the long bones, pelvis, cranium, immune response. sternum, and vertebrae. • • Type AB is called the universal recipient as there Red cells transport oxygen. are no circulating antibodies capable of attacking • White cells are part of the immune system. A or B red cells. • Platelets are a part of the blood clotting process. • The process of determining blood compatibility between the recipient and donor blood is called • The coagulation cascade, using multiple factors, cross-matching. leads to the development of fi brin, a blood clot. • Transfusion reactions vary from minor to life- • Normal hemoglobin amounts vary from males to threatening. females. • Treatment depends on the type of reaction. • Hematocrit compares the ratio of solid components • Prior to transfer, verify pertinent details regarding of blood to the volume of blood. the patient and the blood products. • The four blood components most frequently • Blood may be transfused via a “Y” shaped blood transfused include packed red blood cells (PRBC), administration set or a piggy back system. The fresh frozen plasma, cryoprecipitate, and platelets. blood administration is the preferred method. 610 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. • Blood must be kept cool to reduce the risk of • The transfusion record must be completed after reactions. each unit of blood product. • The patient should have vital signs taken every 15 • Any blood product and tubing involved in a minutes during transfusion. transfusion reaction should be brought to the blood bank at the receiving hospital. Review Questions: 1. What determines a blood group? 7. What four blood products are routinely 2. Name the blood groups. transfused (not necessarily to the same 3. What is a universal donor? Universal recipient? patient)? How do they differ from each other? How are antigens and antibodies involved in 8. Defi ne hemoglobin. Defi ne hematocrit. these designations? 9. Name each transfusion reaction and list its 4. What are the solid components of prehospital treatment. the blood? 10. What items should be verifi ed before transport? 5. What is the process by which the solid 11. How often should the patient be assessed components of blood are formed? Where are (minimally)? they formed? 12. Describe the process of completing a blood 6. What is the liquid portion of blood called? transfusion including its documentation. Case Study Questions: Please refer to the Case Study at the beginning of 3. What blood components is this patient likely the chapter and answer the questions below: receiving? Explain your answer. 1. How are blood transfusions managed? 2. What complications can occur during transfusion? References 1. Schreiber GB, Busch MP, Kleinman SH, Korelitz JJ. Risk of 5. Stanford School of Medicine Blood Center. Blood types in the transfusion-transmitted viral infections. N Engl J Med. June 27, U.S. Available at: http://bloodcenter.stanford.edu/about_blood/ 1996;334(26):1685–1690. blood_types.html. Accessed October 31, 2008. 2. Kauvar DS, Holcomb JB, Norris GC, Hess JR. Fresh whole blood 6. Santen SA. Transfusion therapy. In: Tintinalli JE, Kelen GD, transfusion: a controversial military practice. Journal of Trauma. Stapczynski JS, eds. Emergency Medicine: A Complete Study 2006;61(1):181–184. Guide (6th ed.). New York: McGraw Hill; 2004:1348–1353. 3. Department of Medicine, Washington University School 7. Nester T, Lopez-Plaza I. Bacterial contamination of cellular blood of Medicine. Chapter 19: Anemia and transfusion therapy. products. Transfusion Medicine Update. Epub February 2001. Washington Manual of Medical Therapeutics. 2007. Available at: http://www.itxm.org/TMU2001/tmu3-2001.htm. 4. Wittler MA, Hemphill RR. Acquired bleeding disorders. In: Accessed October 28, 2008. Tintinalli JE, Kelen GD, Stapczynski JS, eds. Emergency 8. Toy P, Popovsky MA, Abraham E, et al. Transfusion-related acute Medicine: A Complete Study Guide (6th ed.). New York: McGraw lung injury: defi nition and review. Critical Care Medicine. Hill; 2004:1324–1329. 2005;33(4):721–726. Blood Products and Transfusion 611 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. KEY CONCEPTS: Upon completion of this chapter, it is expected that the reader will understand these following concepts: • Pharmacology as a study of drug treatments • Regulation, classifi cation, and referencing of drugs • New drug development and public safety • Mechanisms of action • Special considerations of the pregnant, pediatric, and geriatric patients Case Study: Katie O’Rielly had fallen from her bike while trying some tricks on her brother’s homemade skateboard ramp. While the junior Paramedic partner completed the assessment and obtained vital signs, his senior partner called for medication orders. After reporting that Katie was 7 years old, had signifi cant deformity to her left wrist and forearm, and had no allergies (according to her dad), the Paramedics relayed Katie’s vital signs, weight, and pain scale. After completing Katie’s care, which included some IV pain medication and medication to prevent nausea, the Paramedics transferred her to the hospital and began completing their paperwork. “Have you administered narcotics with this agency as yet?” asked the senior Paramedic. “There are very specifi c procedures and paperwork to complete.” 612 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Introduction to Pharmacology 613 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. OVERVIEW Pharmacology has its origins in medicinal treatments used to restore humoral balance to the body. As experience and experimentation pushed forward, the paradigm shifted from humoral imbalance to the idea that illness is caused by disease. This chapter will outline how drugs are classifi ed, regulated, and developed as well as how the Paramedic may reference an unfamiliar medication. Becoming familiar with pharmacology also requires the Paramedic to understand basic pharmacokinetics and how drugs are absorbed, distributed, detoxifi ed, and eliminated from the body. Just as important as understanding how a drug moves through the body is how a drug specifi cally works upon a cell. Pharmacodynamics helps to explain how drugs create their therapeutic effect and helps the Paramedic to understand a drug’s mechanism of action. Presented throughout the chapter are the special considerations that apply to administering drugs to pregnant, pediatric, and geriatric patients. Paramedic Pharmacology term “pharmacy” comes from the Greek word “pharmakos,” which can be translated to mean either “to remedy” or “to Drugs have had, and continue to have, a dramatic impact on life. poison.” It is imperative that all Paramedics understand the In 1901, the average American could expect to live to be about actions of these medications and their potential for harm 49 years old. One hundred years later, the average American before administering them. can expect to live to be at least 78 years of age.1 A number of factors, such as safer working conditions, improved nutrition, cleaner water, better sanitation, and the advent of potent medi- Historical Development cations, have led to this dramatic increase in life expectancy. of Pharmacology In addition, great medical breakthroughs have dramatically improved the quality and duration of life (Table 29-1). In 1889, Sir Petri discovered an Egyptian papyrus written in Advances in safety and ease of administration of pharma- 1900 B.C. that described the treatment of a “falling womb” cological agents, as well as the advantage of early intervention with a gruel made of cool milk and grain. Believed to be the in acute medical emergencies, has prompted emergency physi- oldest written prescription, it represented the timeless effort cians to promote the use of these medications by Paramedics. of people to rid themselves of disease. Throughout world his- Today, Paramedics carry some of the most powerful drugs tory, continuous discoveries and advancements in the use and available in medicine. These medicines are capable of sav- creation of medications have taken place. Many medications ing a life when used appropriately. However, these drugs are have revolutionized the practice of medicine. equally capable of causing death if given without due regard Some of the earliest accounts of medication use came to their mechanism of action and possible side effects. The from the work of priests in the temple of Asclepius (the Greek God of healing). Here priests would instruct patients on a variety of treatments, ranging from the application of poultices made of herbs to the use of charms to frighten evil Table 29-1 Major Medical Breakthroughs spirits. Each attempt to use medications was met with vary- 1796 Vaccines ing degrees of success, with the outcome more likely to be 1865 Antiseptic poor than good. Most people felt that illness was created by 1895 X-ray the gods or was the result of evil spirits. Therefore, it was 1897 Aspirin 1905 Vitamins believed that illness was inevitable and, more importantly, 1922 Insulin immutable to physician interventions. 1929 Antibiotics 1933 CPR 1953 Polio Street Smart 1960 Pacemaker 1967 Heart transplant 1972 Medical fi lming Asclepius, the Greek God of healing, was thought to 1980 Smallpox hold the serpent as sacred. His symbol, a staff with a 1982 Artifi cial heart 1990 Human genome coiled snake around the shaft (known as a caduceus), 1997 Cloning is now used as a symbol of medicine. 1998 Stem cell research 614 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that |
any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Hippocrates (460–560 B.C.), a member of the healing theory, publicly burned copies of Galen’s writings and guild Asclepiadae named after the god Asclepius, is consid- Avicenna’s “materia medica,” and suggested instead that ill- ered the “father” of western medicine. Hippocrates advanced ness was caused by disease. He believed that disease could be the idea that disease was not caused by evil spirits but rather treated with mineral baths of mercury, arsenic, lead, or cop- by natural causes, i.e., an imbalance in the body. Imbalances per and alcoholic extracts, formulas of which he added to the in the “humours” contained within the body was a revolution- pharmacopeia.4 This idea, that illness was caused by disease, ary idea in its time.2,3 was a radical departure from the theory of humoral imbal- These humours were red blood, white phlegm, yellow ances. It suggested that, with experience and experimenta- bile, and black bile, each representing the fundamental ele- tion, medications could lead to the cure of disease. Paracelsus ments of air, water, fi re, and earth. Hippocrates also believed was credited with establishing the scientifi c method in his in the recuperative powers of the human body and felt that study of medicine, a practice that continues even today. medicine could help to support the body’s efforts at bringing In the centuries that followed, medicine made great strides itself into balance from “humoral pathology.” toward relieving suffering and curing disease through the use Some of the most important advances in medical prac- of drugs and herbal remedies. Widespread experimentation tice during that time are credited to Galen, a physician to the with these new formulas in order to create new remedies her- gladiators and later court physician to Commodus, the son alded the dawn of pharmacology, the study of drugs. of Marcus Aurelius. Galen wrote volumes about medicine In the early 1600s, the fi rst London pharmacopeia was and established a system of medicinal practice that remained compiled. This was followed in 1618 by creation of the fi rst intact until after the Dark Ages. He wrote of the nature of national pharmacopeia, the French Codex. Thereafter, many pulses and described certain “ores” and potions of medicinal national pharmacopeias were compiled. Drugs, as a commod- value, including the “balm of Gilead,” a juice-balsam. ity, were then traded from city to city and country to coun- After the time of Hippocrates and Galen, the science of try since these national pharmacopeias allowed free trade of medicine developed along several different paths. Although similar drugs. With the widespread availability of the drug the contributions early Chinese and Indian practitioners information contained within these national pharmacopeias, made to the science of medicine were signifi cant, the focus of pharmacies began to appear in marketplaces all over Europe. medicine in the western world lay along the paths created by Exact formularies also allowed industries to be developed for Hippocrates and followed by Galen. However, the Arab world the mass production of medicine. Thus, medications began was to have a great infl uence on western medicine as well. to become more widely available to the public. Examples of Arabic medicine, practiced from the fertile crescent of Persia these early medications include tincture of opium, used to to the south of Spain, made signifi cant advances, particularly treat diarrhea (a common malady in a time when dysentery in pharmacy. This was due in part to the introduction of arith- was rampant), and syrup of ipecac, used in presumed poison- metic, which allowed addition and subtraction in measure- ings to prevent illness.5 ments of raw materials and substances. Early Arabic infl uence in medicine was seen in the writ- Sources of Drugs ings of Ibn Sina (Avicenna), physician-in-chief in Baghdad. He wrote volumes about medicine, 290 manuscripts in total, When pharmacy was in its infancy, most medications came including his treatise on medicine entitled Kitah al-Qanun from plants. Advances in pharmacy and chemistry resulted in (translated The Medical Code). He was second only to Galen the development of new sources for drugs, including drugs in his infl uence on western medical thought. Ibn Sina’s fi ve- from animal by-products, minerals, synthetic medicines, and, volume Kitah al-Qanun arranged medical knowledge by sub- most recently, genetic engineering. ject, described some 760 drugs alphabetically, and described diseases and their treatment.4 Plants Later, in the sixteenth century, pharmacy was to be further Early pharmacists would take the roots, fl owers, and seeds of advanced by a German botanist named Valerius Cordus who a plant; crush them; mix them together in different amounts, wrote the fi rst authoritative collection of formulas of drugs or formulas; and create crude drugs. While many of these called a “pharmacopeia.”5 A pharmacopeia, also called a herbal concoctions were impure and impotent, some had compendium, is a comprehensive list of drugs which not only active ingredients which had an intended or therapeutic includes formulas but usual strengths, standards of purity, effect. The bark of the willow tree, for example, was used and ranges of doses that are available in a certain country or as a cure for a number of ailments including headaches. It region. By creating “drug standards”—specifi cations for the contains the active ingredient salicylate, which is still used mixture of minerals, chemicals, and biological materials—a in aspirin today. large number of deaths secondary to accidental overdose While most medications are chemically manufactured were avoided and the effects of specifi c ingredients upon the today, plants are still an important source of many medicines. body were better understood. Many of the essential plant elements of crude drugs are more At about the same time, a physician named Paracelsus highly refi ned, making them more potent, and they are manu- (1493–1541) denounced Hippocrates’ “humoral pathology” factured in mass quantities. Plant derivatives used to make Introduction to Pharmacology 615 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. drugs can be grouped together according to common physi- cal or chemical properties. These organic-based groups are Street Smart alkaloids (glycosides), oils, and gums. The Alkaloids The antibacterial action of common household bleach The alkaloids, as the name suggests, are nitrogenous chemi- solution (Sodium hypochlorite 5%), used in EMS to cals which are alkaline in nature and often chemically com- clean surfaces contaminated with blood, is due to bined with acids to create water-soluble salts, such as morphine the off-gassing of hypochlorous acid from chlorine sulfate or atropine sulfate. When these alkaloids are absorbed in water. The resulting chlorine gas is toxic to most into the body they dissolve easily. The acid and alkaline com- ponents dissociate and the alkaloid drug can be transported in bacteria. the bloodstream and eventually deposited at the target organ, where it can produce its intended therapeutic effect. One of the earliest drugs obtained from a plant was digi- Animal talis. Digitalis, a cardiac stimulant found in the nightshade Many drugs have their origins, in whole or in part, from plant, was used to treat a cardiac condition referred to then as animal tissues. The discovery of insulin is a case in point. dropsy, which is now known to be congestive heart failure.6 Diabetes mellitus is a disease that causes the patient to excrete The active ingredient in plant-based drugs like digitalis is massive amounts of thick syrup-like urine. The resulting side-linked to a simple sugar, a glucose molecule, in the plant. diabetes-induced dehydration can lead to severe shock. In Thus, it is called a glycoside. Glycosides are easily absorbed the summer of 1921, Fred Banting noted that an injection of into the bloodstream and the active ingredient is taken up by extract from the pancreas of animals, specifi cally the islets the target organ when the sugar is absorbed. of Langerhans, reversed the ill effects of the diabetes and allowed the patient to return to a near-normal life. That extract The Oils was fi rst called isletin and then later insulin. Sir Frederick G. Oils are substances that have been extracted from plants for Banting, MD, won the Nobel Prize for his discovery of insu- centuries for their use as food additives as well as medica- lin. Shortly thereafter, the Eli Lilly Drug Company began to tions. An example is olive oil. Some plant-based oils have mass-produce insulin, which it extracted from the pancreas of medicinal properties. For example, caster oil is used as a lax- cows (beef insulin) and pigs (pork insulin). This resulted in ative. Oils that give off an odor are called aromatic oils. The improved lives for many diabetic patients. Many other drugs, aroma is caused by volatile chemicals that evaporate, or off- such as epinephrine (adrenaline), were discovered in similar gas, into the atmosphere. These aromatic oils are often used fashion and the study of “organotherapy” fl ourished in the as fl avoring essences for medicine (e.g., oil of peppermint) or late 1800s.5 as soothing topical astringents, such as oil of spearmint. Synthetic The Gums One of the diffi culties of manufacturing animal-based drugs The gum of a plant, sometimes called its resin, is actually was the pure volume of animal tissue that was sometimes a complex sugar, a polysaccharide, that when moistened needed to create them. For example, only one-half ounce of becomes a gelatinous material. Complex sugars are also corticoid steroid could be distilled out of one ton of cows’ called colloids because they are too large to pass through adrenal glands.7 Drug manufacturers had a tremendous hur- a semipermeable membrane. When a gum is swallowed, it dle to overcome to produce these drugs profi tably. swells because of osmosis, forming a gelatinous bulk. This In the 1940s, a basic building block of human hormones property is useful when a laxative effect is desired. Applied was discovered as naturally occurring in wild Mexican yams. externally, certain gums help to soothe irritated skin. These yams could be transformed, with chemical process- ing, into the female hormone progesterone. That discovery Minerals, Chemicals, and Salts (using select plant stuffs and chemically processing them to Natural salts and minerals have also been used for centuries produce drugs) led to an explosion of research into plant- for their medicinal qualities. For example, magnesium cit- based synthetic drugs. Today, this research continues as roots rate, contained within a lemon-fl avored carbonated beverage, and tubers from newly discovered species of plants from the Amazon basin are being tested for possible medicinal use.5 is used as a laxative to relieve constipation and cleanse the bowel before certain medical procedures. The chemical mercury and a large number of mercury- Genetic Engineering based compounds were used to halt the epidemic spread of The future of drug manufacturing may be in genetic engi- the blood-borne disease syphilis. Syphilis is the only disease neering. Genes are the architects of cell construction and thought to have been transmitted from the New World to the contain the blueprint for protein production—the proteins Old World.5 that regulate cell function. Some diseases (e.g., hemophilia 616 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. and cystic fi brosis) are thought to be caused by a failure of chemists are able to group drugs into classifi cations accord- a gene to produce a certain protein. Genetically engineered ing to their common chemical makeups and thus understand medicine involves inserting a therapeutic gene into the mal- the specifi c chemical nature of a drug. functioning cell via a benign viral vector and allowing |
the After further development, manufacturers will assign a cell to produce the correct protein again. This process could simpler to pronounce generic name to the drug. The generic eradicate the disease. name is often the drug name listed by the manufacturer in the This approach to treating disease is still experimental United States Pharmacopeia (USP). The U.S. Pharmacopeia but holds a great deal of promise. Pharmacogenomics, a is a listing of all of the drugs legally manufactured or for sale combination of pharmaceutical research with the study of in the United States. The letters USP follow the generic name the human genome, promises to fi nd other new ways to treat after it is listed in the U.S. Pharmacopeia. disease. With the human genome map completed in February After suffi cient research has been done and a drug is 2001, scientists have started to look at individual gene varia- approved for distribution by a company, that company often tions, called “single nucleotide polymorphisms” or snipes, will patent the drug to prevent other manufacturers from pro- that cause or lead to disease or adverse drug reactions. ducing the same drug. To distinguish a patented drug, manu- For example, a liver enzyme called CYP2C6 eliminates facturers will assign a unique third name, called the trade at least 30 different drugs from the body including beta- name. blockers, tricyclic antidepressants, antidysrhythmics, and opiate derivatives. By affecting this liver enzyme, it is pos- Drug Classifi cation sible to give smaller but still effective doses of medicine. The effi ciency of drugs in the future may be vastly improved if Drugs are divided into two classifi cations: prescription and scientists can make cells produce enzymes which assist the nonprescription. Drugs that cannot be dispensed by a phar- transportation of drugs into the cell.7 macist without the written or verbal order of a physician or a Currently, some drugs are genetically engineered pro- mid-level healthcare provider, such as a physician’s assistant, teins that replace missing proteins in the body. For example, are called prescription drugs. The amount, or dose, of drug Humulin™ is a genetically engineered form of human insulin. in a prescription drug can have serious side effects. Therefore, their administration requires careful patient monitoring by a Drug Terminology healthcare provider. By defi nition, a drug is any material which, when injected, ingested, inhaled, or absorbed into the body, is used for the diagnosis, treatment, or cure of a disease or condition. Some Street Smart drugs may have more than one purpose. For example, the drug naloxone is often given to patients who are unconscious All prescription medications are federally mandated for an unknown reason but who are suspected of having over- dosed on opiates. Naloxone reverses the physiologic effects of to display the legend “Caution: Federal law prohibits the opiate. If the unconscious patient does not respond to the dispensing without prescription” and therefore are naloxone, then an opiate overdose is less likely to be the cause called legend drugs. of unconsciousness. In this situation, naloxone is used as both a diagnostic drug and a treatment for opiate overdose. Every drug is assigned three names, each with a specifi c Although Paramedics are seldom asked to read a pre- meaning to a different group of people (Figure 29-1). As scription from a physician, the pharmacist often directly chemists and pharmacists develop new drugs they normally transcribes the physician’s written prescription onto the assign each a chemical name. A chemical name is a descrip- prescription label. Paramedics frequently read, review, and tion of the drug according to its elemental chemical makeup document what is on a patient’s prescription label. Therefore, and molecular structure. By utilizing a chemical name, Paramedics should understand abbreviations that are rou- tinely found on prescription labels (Table 29-2). There is an increasing practice of using plain English in a prescription, especially because of electronic prescriptions. As the name implies, nonprescription medications can be purchased by the public without a prescription. Nonprescription drugs are generally sold by pharmacists over-the-counter (OTC) so patients can self-treat minor i llnesses. The Health Care Financing Administration (HCFA) estimates that 6 out of 10 medications purchased in the United States are OTC. Presently, there are over 300,000 OTC Figure 29-1 An example of a drug’s names. medications on the market.5,8 Introduction to Pharmacology 617 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Table 29-2 Common Prescription Notations a before kg, Kilo kilogram PRN, prn whenever necessary ac before meals KVO keep vein open pt pint, patient ad lib as desired L liter qh every hour AM, am morning LA long acting q2h every 2 hours amp ampule Ib pound q3h every 3 hours b_id twice a day mcg microgram q4h every 4 hours C with mEq milliequivalent QNS quantity not suffi cient cap capsule mg milligram qs quantity suffi cient Cl chloride ml, mL milliliter (equivalent to cc) qt quart cm centimeter mm millimeter R rectal DC discontinue Na sodium _RL, R/L Ringer’s lactate DS double strength NaCl sodium chloride S without DW distilled water NEB nebulizer SubQ, subq subcutaneous D5W dextrose, 5% in water NG nasogastric SL sublingual EC enteric coated noc night sol solution elix elixir NPO, npo nothing by mouth SR sustained release ER extended release NS, N/S normal saline (sodium stat immediately and once only Fe iron chloride, 0.9%) supp suppository fl fl uid Ø none tab tablet Gm,g gram OTC over the counter tbsp, T, tbs tablespoon gr grain oz ounce tid three times a day gtt drop p after TO telephone order h, hr hour pc after meals tsp, t teaspoon IM intramuscular PCA patient controlled vag vaginal IV intravenous analgesia Vit vitamin IVPB intravenous piggyback PM, pm afternoon VO verbal order K potassium po, PO by mouth, orally KCL potassium chloride Note: Abbreviations should be written without periods. remain undiagnosed until the illness reaches crisis propor- Street Smart tions. Furthermore, citizens who are attracted to an OTC drug’s purported action, as advertised by means of the popu- lar press or the Internet, may not read the FDA mandated Seasoned Paramedics know that the patient’s warnings on the drug’s label. Complicating matters, it is prescriptions can often lend a great deal of insight into estimated that 20% of the American public are functionally the patient’s past medical history. Patients frequently illiterate and cannot read the label’s warnings.9 As an overall store prescription medications in medicine cabinets in result, OTC drugs can be unsafe or, when improperly used, can cause unexpected side effects. the bathroom, in the bedside stand, or in the kitchen For these reasons, Paramedics should recognize that next to the water glasses. In some cases, patients may OTC medications are potentially dangerous, can have unde- have already listed the prescriptions for emergency sirable interactions with other drugs, and that OTC drugs are a part of the patient’s medical history. The Paramedic should responders and placed the list in a “vial of life.” These consider including a list of the OTC drugs that the patient is vials are often stored in the refrigerator and a “vial taking in the patient care report. of life” sticker placed on the outside of the The difference between prescription and OTC drugs can refrigerator door. sometimes be just the strength of the preparation (i.e., its potency). In smaller doses, the drug may be relatively safe for patient self-administration, whereas at higher doses there is a The public, in an effort to lower healthcare costs, have greater potential for harm to the patient if the OTC drug is mis- increasingly been self-diagnosing, self-prescribing, and self- used. For this reason, the higher dose medication requires a pre- administering OTC medicine. This practice is not without its scription. Ibuprofen is an example. Ibuprofen comes in 200 mg, dangers. Serious symptoms can be masked by OTC medi- 400 mg, and 800 mg strengths. The public can buy the 200 mg cations. Subsequent errors in medical judgment can occur, dose of Ibuprofen over-the-counter, whereas the higher strength resulting in a life-threatening medical condition that may tablets require a physician’s prescription and a pharmacist to 618 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. dispense it. This prescription guarantees a licensed healthcare The United States Pharmacopeia (USP) drug reference is provider has determined the medication is safe for the patient created by an independent nongovernmental science-based pub- to use at that strength and that a licensed healthcare provider is lic health organization called the United States Pharmacopeia. monitoring the patient’s health while taking the drug. The United States Pharmacopeia is made up of over 1,000 sci- entists, practitioners, and representatives from various colleges Herbal Remedies of medicine and pharmacy who set the standards for medica- tion manufacturing in the United States. This group of physi- The medicinal use of herbs, also called botanicals, is also cians, pharmacists, and scientists meets every fi ve years, at increasing across the United States. This increased use of the United States Pharmacopeial Convention, to discuss and herbal remedies may possibly be as a result of disenchant- adopt recommendations presented from the internal Council ment with traditional western medicine on the part of some. of Experts (COE) regarding new drugs to be added to the However, the use of botanicals can create new problems for United States Pharmacopeia listing. The National Formulary the patient and the Paramedic. Many patients who are taking (NF), another drug reference, is a manual that lists medica- herbal remedies are confounding their medical treatment with tions which are approved for prescription. It contains specifi c the addition of untested herbal preparations which can cause chemical information that is more helpful to the pharmacist and unpredictable consequences. Therefore, Paramedics should manufacturer than the physician. Today, the U.S. Pharmacopeia know the effects of some of the more common botanicals and (USP)—as well as the National Formulary (NF), which is part their potential interaction with the drugs that the Paramedic of the USP—is recognized by the Federal Drug Administration would be administering (Table 29-3). It is important that the and contains the standards of purity, dose, formula, and other Paramedic list all herbal products along with over-the-counter information for drugs. The USP is, per the Federal Food, Drug, and prescription medicines on the patient care report. and Cosmetic Act (2 U.S.C.321), the authority for drug manu- Observant Paramedics may note the presence of teapots, facturing in the United States. The USP is a two-volume text. pots and pans, and the like and ask the patient questions about The fi rst volume includes all prescription medications and the herbal remedies. Methods of botanical administration include second volume includes all over-the-counter medications. potable infusions (boiling water over the top of the herbs and Another reputable source of information about prescrip- immediately drawing off the solution), decoction (bringing tion and over-the-counter medications is the Physician’s water to a boil then steeping the herbs like one would a tea- Desk Reference (PDR). The PDR is a compendium of manu- bag and drinking the resulting solution) and cold maceration facturer drug-prescribing information which is usually found (letting herbs steep in cold water). in a package insert required by law to accompany all medica- tions. These Food and Drug Administration (FDA)-mandated Sources of Drug Information inserts contain information, including common side effects, obtained during drug testing trials. A pharmacopeia is a list of the drugs commonly used in a It is sometimes diffi cult for a Paramedic to obtain infor- country. The fi rst U.S. Pharmacopeia was published in 1820 mation quickly and in useful form from the USP, the NF, |
or as a guide to apothecaries who collected plants and fl owers the PDR. Quick reference books, such as Delmar’s Drug and for physicians who compounded their own remedies.10 Reference for the EMS Provider by Richard Beck, are fast and Typically, a group of physicians, pharmacists, and other pro- convenient ways to obtain that information in a user-friendly fessionals, create a pharmacopeia. manner. These references typically group medications Table 29-3 Partial List of Common Botanicals Name Use Side Effect/Precaution Aloe vera Heal wounds; Laxative Potassium loss Cascara sagrada bark Laxative Intestinal obstruction; Potassium loss Chamomile Anti-infl ammatory Anaphylaxis; Cross allergy—Ragweed Cranberry Urinary deodorizer Diarrhea Echinacea Infections Cross allergy—Sunfl ower seeds Garlic Lower blood pressure Reduces platelet aggregation; Interacts with blood thinners Reduces platelet aggregation; Affects calcium channel blockers Ginger Morning sickness (pregnancy-induced hypertension) Ginkgo biloba Depression; Alzheimer ’s disease Reduces platelet aggregation; Cross allergy—Poison ivy Ginseng root Improve concentration Interferes with digoxin; Hypoglycemia Kava kava Sedative Worsens Parkinson symptoms Licorice Upper respiratory infection Use with thiazides—increased potassium loss St. John’s wort Herpes simplex; Depression Hypertensive crisis—if taken with tyramine-containing foods Introduction to Pharmacology 619 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. together in classifi cation by body system or by clinical indi- Historical Legal Developments cation. These reference manuals provide further information on a drug’s action, dose, use, risk during pregnancy, common in Pharmacology side effects, and treatment of overdose. Every Paramedic The image of a medicine man in a top hat leaning over the should have a drug reference available to identify unfamil- side of a painted wagon, extolling the virtues of a snake oil iar patient medications. Knowledge of a patient’s medication remedy, is all part of the lore of the American West. It is also history can lend insight into the patient’s condition. Many the genesis of many modern drug laws. These medicine men, Paramedics also create their own drug cards, handy pocket as well as catalog mail order houses and self-anointed doc- references that contain a partial listing of pertinent informa- tors, sold a variety of concoctions which promised to cure tion (Figure 29-2). everything from arthritis to the common cold. Many of these cures did not work and, worse yet, many of them contained dangerous drugs such as opium and chloral hydrate.11 MANNITOL In an effort to protect the public from false advertising Osmitrol and adulterated medicine, Congress enacted the Pure Food and Drug Act of 1906. The law prohibited the use of false CLASSIFICATIONS or misleading claims. The law further stipulated that if a Pharmacologic: Osmotic diuretic medicine contained any of the 11 “dangerous” drugs, then Therapeutic: Diuretic the drug(s) had to be listed on the label. Additionally, the Pure Food and Drug Act of 1906 recognized the National MECHANISM OF ACTION: Mannitol increases osmotic pressure in Formulary and the United States Pharmacopeia (USP) as the the glomerular fi ltrate. This inhibits the reabsorption of water offi cial drug standards for the United States. and electrolytes, which causes their excretion in the urine. Unfortunately, there were many loopholes in the law. For THERAPEUTIC BENEFIT: The diuretic action of mannitol causes a example, the federal law did not apply to drugs produced in a dehydrating effect on the brain. state and then sold only within that state. The addition of the INDICATION FOR PREHOSPITAL USE: Mannitol is used to relieve Durham-Humphrey amendment in 1952, which included new excessive intracranial pressure. regulations regarding labeling and the refi ll of prescription CONTRAINDICATIONS: ■ Do not administer mannitol to patients medications, closed some of these loopholes. The amend- with: ■ Hypersensitivity to the drug. ■ Preexisting dehydration. ment also required the addition of a written warning, called ■ Active intracranial bleeding. a legend, for drugs that are injected, that are investigational, PRECAUTIONS: Use caution in administering mannitol to patients or that are potentially habit-forming (Figure 29-3). Perhaps who show a tendency to congestive heart failure, because mannitol more importantly, the amendment described a new class of may cause a sudden expansion of extracellular fl uid, which could bring on congestive heart failure. drugs for which a prescription was not required, the over-the- counter (OTC) drugs. ROUTE AND DOSAGE Adult: 1.5–2 g/kg of a 20% solution by IV infusion, using an in-line IV Controlled Substances Legislation fi lter. Mannitol comes in a 5, 10, 15, or 20% 500-mL solution. Pediatric: Not recommended for prehospital use. The use of opium, with its long and undistinguished history as a drug of abuse, ultimately led to many of the modern narcotic ADVERSE REACTIONS AND SIDE EFFECTS drug laws. Opium, a product obtained from the poppy plant • CNS: Headache, confusion. (Papaver somniferum), was freely available over the counter • Cardiovascular: Tachycardia, chest pain, congestive heart failure, pulmonary edema. • Eyes: Blurred vision. • Fluids and electrolytes: Dehydration. • Gastrointestinal: Nausea, vomiting, thirst. PARAMEDIC IMPLICATIONS: ■ Monitor the patients closely for any signs of dehydration, which include: ■ Fever. ■ Thirst. ■ Decreased skin turgor. ■ Dry skin and mucous membranes. ■ Mannitol has a tendency to crystalize at temperatures below 45°F. Use an in-line fi ler when administering mannitol to fi lter any crystals out of the solution. DRUG INTERACTIONS: ■ Additive CNS depression can result if mannitol is administered with other CNS depressants. ■ Mannitol can also cause additive adrenergic effects and anticholinergic effects when used with CNS depressants. Figure 29-2 An example of a drug card. Figure 29-3 An example of a prescription legend. 620 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. in the 1700s. Mothers used tincture of opium to control diar- made up of mainly out-of-work prohibition offi cers, was rhea, brought on by cholera or dysentery, because opium has formed to enforce the Harrison Act. Newly deputized federal a powerful constipating effect. Unfortunately, these early narcotic agents immediately arrested some 3,000 doctors for opium preparations, including laudanum and paregoric, were illegally prescribing opiates to addicts. The Federal Bureau very crude and the effects often unpredictable. Occasionally, of Narcotics was later reorganized and became the Drug these drugs would harm the patient as a result. Enforcement Administration (DEA) in 1973.5 In 1820, a German pharmacist, Friedrich Serturner, In furtherance of the intent of the Harrison Act, and attempted to refi ne opium into its active ingredient, ridding as a part of his “war on drugs” campaign, President Nixon it of its impurities. He named the resulting drug “morphia,” signed the Comprehensive Drug Abuse Prevention and after the Greek god Morpheus, the god of dreams.12 The com- Control Act of 1970 (Controlled Substance Act) into law. bination of the increased availability of morphine and the This expanded the authority of the DEA. Contained within invention of the hypodermic needle in 1850 led to the wide- the Controlled Substance Act were schedules of potentially spread use of morphine as an pain reliever (analgesic). dangerous and addictive drugs which had special restrictions In a continuing effort to improve on opium, other deriv- (Table 29-4). atives of opium were also produced. In 1898, the German pharmaceutical company Bayer produced the semi-synthetic opium derivative diacetylmorphine and branded it “hero-in,” Street Smart the hero drug which had the same ability to relieve pain as morphine but was safer. Unfortunately, heroin did not live up It is important to remember that the federal schedule to its promise and the medical community largely abandoned its use in favor of morphine. of narcotics includes non-opiate substances, such as Opium and morphine use in the United States reached its marijuana and cocaine. The term “narcotic” should not pinnacle in the late 1800s and opium was readily available to be used interchangeably with opiates. The Paramedic the public. As opium dens and pharmacies started to dispense should specifi cally refer to opiates by name. larger and larger amounts of opiates, correspondingly larger numbers of people were becoming addicted to opium. In response to the growing drug problem, the United States Congress passed the Harrison Act of 1914.13 The Drug Misuse versus Drug Abuse Harrison Act made it illegal to obtain “narcotics” (e.g., mor- The difference between drug misuse and drug abuse is an phine) without a prescription. The list of narcotics included important distinction. Drug misuse implies that the drug is drugs such as cocaine, which is a stimulant. (Marijuana would not being used as prescribed and can lead to problems of later be added to the list.) toxicity. Drug abuse implies concerns about dependency and However, the problem of opiate addiction was largely intentional improper use of a drug. Drug misuse is a complex unaffected by the Harrison Act because physicians continued issue which includes unintended drug interactions as a result to prescribe the opiates. In a challenge to the Harrison Act, the of polypharmacology (multiple drug actions). Supreme Court ruled that the act of supplying addicts, even Drug abuse involves the intentional misuse of drugs, pre- when the narcotics were obtained under physician’s prescrip- scription as well as illicit, for a purpose other than the diagno- tion, was illegal. In 1930, the Federal Bureau of Narcotics, sis, treatment, or cure of a disease or condition. Drug abuse Table 29-4 Schedule of Drugs and Examples of Controlled Substances Class Defi nition Examples Restrictions I High abuse, No medical use Opium, Marijuana, LSD Special protocol II High abuse, Limited use, Severe Fentanyl, Codeine Triple prescription, No refi ll, See Note dependence III Lower abuse, Medical use, Small amounts of codeine Limit six months, No more than fi ve refi lls, See Note Moderate dependence combined with aspirin or acetaminophen paregoric IV Minor abuse, Medical use, Minor Barbiturates, Benzodiazepines Limit six months, No more than fi ve refi lls, See Note dependence V Low abuse Medical use Limited Cold remedy May require prescription physical or psychological dependence Note: Federal law prohibits the transfer of this drug to any person other than the patient to whom it was prescribed. Source: DEA pharmacist’s manual—an informational outline of the Controlled Substance Act of 1970. U.S. Department of Justice, Washington D.C. Red Book, 1996. Introduction to Pharmacology 621 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. often leads to dependency, a craving for the drug that can lead FDA immediately established a drug approval process that to socially unacceptable behaviors and/or the person’s inabil- refl ected these regulations. ity to perform activities of daily living (ADL). Now, when a pharmaceutical company manufactures a Dependence on a drug occurs when a person has a com- new drug, or has an old drug that is being used for a new pur- pulsive desire to have a drug, and the drug becomes the sole pose or at a new strength, it has to apply to the FDA to make source of satisfaction for that person. Dependence also can be the drug an “investigational new drug” (IND). Before a drug physical, a biochemical change in the body as a result of taking can be IND certifi ed, the manufacturer is required to submit the drug, or it can be psychological, the compulsive desire to animal studies to the FDA that identify the drug’s therapeutic have the drug. Habituation is the mildest form of psychologi- dosage, its lethal toxicity, its therapeutic range, and its thera- cal dependence. Cigarette |
smokers, dependent upon the stim- peutic index. ulant effects of the nicotine in the cigarette, have a “smoking The therapeutic range of a drug starts at the minimally habit.” In some cases, the habit can be stopped without any effective dose (the dose that elicits the desired therapeutic harm to the individual. Psychological dependence becomes response) and concludes with a maximum dose (the dose pathological when the person insists that the drug is needed after which any more drug does not produce any more of the in order to survive, despite scientifi c evidence to the contrary, desired therapeutic effect). Somewhere between the maxi- and takes antisocial action in order to obtain it.14 mum and minimum dosage, within the therapeutic range, is the therapeutic dose (the amount of drug that effectively Physical Dependence creates the therapeutic effect in a majority of patients). The therapeutic dose can also be thought of as the median effec- Physical dependence is more than severe psychological tive dose, the ED50. dependence. Physical dependence occurs when the body At the other extreme is the lethal dose of the drug, or LD50. adapts, biochemically speaking, to the constant presence The LD50 is shorthand for lethal dose 50%, where 50% of the of the drug and integrates the drug into the body’s metabo- test animals given a certain dose of medicine died. LD50 is the lism. In short, the body needs the drug in order to maintain median lethal dose. It should be recognized that patients can homeostasis. The following example is illustrative of physi- still succumb to doses far less than the LD50 and caution should cal dependence. always be practiced whenever giving a drug. Manufacturers Coffee drinkers enjoy coffee because it contains the also have to describe the modes of absorption, distribution, stimulant caffeine. Caffeine interferes with adenosine recep- metabolism, and excretion of the drug (i.e., its pharmacokinet- tors by means of a competitive blockade. Adenosine, a neu- ics) before the FDA can approve the drug as an IND. romodulator in the peripheral and central nervous systems, A drug’s therapeutic index is the ratio of the differ- normally attaches to adenosine receptors and reduces cyclic ence between the median effective dose (the ED50) and the AMP levels. Cyclic AMP is important to neurotransmission. median lethal dose (the LD50) of a drug. Drugs with less After a time, the body adapts to the high caffeine levels and than a two-fold difference between the ED50 and the LD50 greater amounts of caffeine are needed to produce the same are defi ned as having a narrow therapeutic index, as defi ned effect. Subsequently, when a coffee drinker suddenly stops in the FDA regulations (320.33(c)CFR 21). A drug with a drinking coffee he can experience irritability, headache, and narrow therapeutic index has a greater chance of causing tox- weakness as a result of the unbalancing of the nervous sys- icity in a patient (Table 29-5). Therapeutic index represents a tem. These withdrawal symptoms indicate a physical depen- calculated safety margin used when prescribing a drug. The dence upon the drug. prescribing healthcare provider has to carefully monitor the patient for toxicity. New Drug Development After the death of over 100 people in 1937, following an Table 29-5 Drugs with a Narrow ingestion of a new drug called “elixir of sulfanilamide,” Therapeutic Index Congress enacted the Food, Drug, and Cosmetic Act, which • Aminophylline prohibited the sale of new drugs before thorough safety test- • Digoxin ing. While the federal government had previously required • Isoproterenol that a drug be properly labeled and safe to use, there was no guarantee that the drug was even effective against the condi- • Lithium tion for which it was prescribed. • Phenytoin The passage of the Kefauver-Harris Act in 1962 went • Procainamide beyond the Food, Drug, and Cosmetic Act of 1937 by adding • Quinidine a new condition to the sale of drugs within the United States. • Valproate The law required that all drugs undergo an extensive review • Valproic acid that not only ensured the public’s safety, but also reassured • Warfarin the public that a drug would do what it claimed to do.15,16 The 622 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. FDA IND Status Drug companies willingly undertake this expense, in part because it lowers their product liability. A manufacturer can Once designated as an IND, further studies of the drug are be held responsible (liable) if the product is defective (not required. In Phase I, an initial pharmacologic evaluation has to fi t for its suggested use or results in harm to the consumer). be performed on the drug to determine modes of absorption, dis- The FDA process helps to ensure that risks are revealed, that tribution, metabolism, and excretion in normal healthy human the manufacturer knows the effect of the product, and that a volunteers. These trials are intended to prove the safety of the reasonable amount of research was performed to protect the IND in human use, not necessarily the effectiveness of the IND. public. The remaining jeopardy for the manufacturer exists In Phase II, a limited controlled evaluation of the drug during the drug’s processing. Major drug manufacturers have is performed upon target populations who have the disease vigorous quality assurance programs to ensure that the drug is for which the drug was developed. Modes of absorption, dis- pure throughout the manufacturing process, from production tribution, metabolism, and excretion then are established for to packaging. this special population of patients. Assuming no diffi culties, the IND would next undergo the Patented Drugs fi nal phase, or phase III, an extended clinical evaluation among the target population under selected conditions. Study “proto- New drugs are typically patented, ensuring the manufacturer cols” would be published and then a determination of clinical exclusive dominion over the drug for a specifi ed period of effectiveness would be established. Issues such as drug dosage time. This allows for a profi t to be made as the manufacturer range and patient drug tolerance are clarifi ed. During phase markets the new drug against older drugs. However, patents III, common side effects are usually described and ranked are time-limited. In many cases, another drug manufacturer according to prevalence in the study’s participants. After the is waiting to produce the same (or a similar) drug, with- thalidomide tragedy of the late 1950s, special attention has out the expense of research and development, in hopes of been given to the effects and potential risks to an unborn fetus. making a profi t. To extend the patent, some pharmaceutical The FDA establishes a drug’s safety for a pregnant woman and companies will expand the drug’s use to include children, a places the drug into one of fi ve categories (Table 29-6). new use of an existing drug. Eventually, however, the patent After completion of the IND process, the FDA either permits expires on all drugs and the drug profi tability declines. This the drug to be marketed and places it in a “new drug” category or fact of business is factored into the decision to develop a returns the drug for further testing (a “one, two, three, and out” new drug. approach). If a drug is designated a new drug, then the pharma- ceutical companies monitor for post-marketing drug interactions Off-Label Use and adverse reactions as part of ongoing surveillance. In some cases, a physician may elect to use a drug for It can take over 12 to 15 years for each new drug to other than its FDA-approved use. While there is some complete the FDA process and may cost as much as $500 risk involved for the physician in prescribing a drug to be million in research.17 Only one in 5,000 potential drug com- used for other than its FDA-approved use, such an action pounds makes it through the process. Seven out of ten new is permitted and is considered to be part of the practice of drugs do not make enough profi t to cover the costs of initial medicine. research and subsequent development costs. These factors Off-label use often occurs when a generic drug, which is have led to increased drug costs for the consumer but have no longer protected by patent, is used for a new indication. In also ensured that safer and more effective drugs are being some instances, it is not cost effective for the pharmaceuti- manufactured. cal companies to research the new indication of these older drugs. Fortunately, this does not preclude the physician from prescribing that drug if, in the physician’s professional opin- Table 29-6 Pregnancy Safety Categories ion, the benefi ts outweigh the risks. A Adequate, well-controlled No risk to human fetus studies in pregnant women Orphan Drugs B Animal studies No risk but no studies to Drug therapies for rare or uncommon diseases are generally substantiate human risk nonprofi table. Development and research for drugs designed C Animal studies Adverse risk but no studies to for these special conditions, called orphan drugs, are often substantiate human risk; question underfunded at best. To provide this population of patients of risk/benefi t analysis with viable treatment alternatives, Congress passed the D Adequate, well-controlled Positive human fetal risk; question Orphan Drug Act of 1983. studies or observational of maternal versus fetal life The Orphan Drug Act provides grants to manufacturers studies in pregnant women and research centers to investigate drug therapies for rare dis- X Adequate, well-controlled Known fetal anomalies; risks eases such as Von Willebrand’s disease or Raynaud’s disease studies or observational studies outweigh benefi ts and create these orphan drugs.17 The FDA classifi es these in animals or pregnant women orphan drugs as “V.” Introduction to Pharmacology 623 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Medicine Errors bronchospasm, but a frequent side effect was tachycardia, a problem for patients with a cardiac condition. Continuing Despite all of the precautions that are taken during the pharmaceutical research aimed at reducing or eliminating research, manufacture, distribution, and preparation of drugs, these bothersome side effects resulted in a more refi ned drug. mistakes can occur. In 1993, the FDA launched its drug The next generation of asthma drugs caused less nervous- watchdog program called MedWatch.18,19 MedWatch is a vol- ness, palpitations, and tachycardia. untary program utilized by healthcare professionals to report adverse or unusual drug reactions and errors. MedWatch identifi es those drugs and medical devices that have, or could Pharmacokinetics have, resulted in death or risk of death, hospitalization, dis- ability, or birth defects. The problems are then reported to the A drug’s therapeutic value is infl uenced by several factors drug manufacturers for corrective action. including the speed of onset of the drug’s effect, the inten- Despite this effort, in 1999 the Institute of Medicine—in sity of the drug’s effect, and the duration of the drug’s effect. its report, “To Err Is Human”—reported that there were These factors are largely the result of the drug’s time and ease 44,000 to 98,000 preventable deaths and 500,000 preventable of absorption, its distribution from the plasma into the tissue injuries due to medical errors.20,21 A subset of those medi- of the target organ, and its eventual retention or elimination cal errors is medication error. The Institute of Medicine esti- from the body. Pharmacokinetics is the study of how these mated that over 7,000 deaths occur annually as a result of factors—drug absorption, distribution, detoxifi cation, and medication administration errors. elimination—affect a drug’s therapeutic value. Alarmed by these statistics, and the attendant implications, professional pharmacists began their own program of |
medica- Absorption tion administration error reporting through the United States In a sequential fashion, the fi rst phase of a drug’s “life” is Pharmacopeia (USP) called MedMARx.22 While pharmacists absorption. For a systemic drug to be effective, it must get had a program for medication error reporting (MER) since 1991, into the bloodstream and be transported to the target organ. the new program sought to understand medication administra- The drug’s movement from its site of administration into the tion errors, not just medication labeling and packaging errors. plasma in the blood is a function of the route of administra- The MedMARx program of the USP is a self-reporting tion. In the case of drugs given intravenously (IV), the drug is Internet program. The focus of these anonymous and volun- instantly available in the blood plasma. However, most medi- tary reports is problems with the process by which medications cations are not given IV; most are given PO (“per os” or Latin are given rather than medication side effects and reactions. for “by mouth”). In that case, the absorption goes through a During 2000 alone, over 184 medical facilities reported over complicated process which will be discussed shortly. Specifi cs 41,296 medication errors.23 Medication errors were classifi ed of the methods of drug administration are discussed in Chapter as causing harm, no harm, or having a potential for harm. 26. However, it is important to understand the impact of medi- Fortunately, 97% of the errors caused no harm. However, 5% cation administration of the various drug administration tech- of reported medication administration errors did cause harm niques as they relate to drug absorption and distribution. For and affected about 1,200 patients. purposes of this discussion, medication administration can be grossly categorized as either enteral (via the gastrointestinal system) or parenteral (other than the gastrointestinal system). Principles of Pharmacology Well over a half million medications—both prescription and Enteral Drug Administration OTC—are available on the market, each asserting that it is the Enteral administration of medication, via the GI tract, is the most effective medication for a specifi c condition or disease. most common form of medication administration. While The basis of these claims lies in the drug’s intended biological easy to administer, multiple intervening factors make enteral effect. The intended biological effect of a drug, also called its medication absorption less predictable and therefore less therapeutic effect, is to modify a tissue or an organ’s function. desirable during an emergency. Drugs can enhance a bodily function by increasing or replac- To begin, once a PO medication is swallowed, the fi rst ing a chemical in the organ. They can also preclude or prevent impediment to drug absorption is the stomach. While the a chemical from having an effect on the organ by blocking or stomach has a rich network of blood vessels for ready absorp- competing with the body’s own chemicals. However, a drug does tion, stomach acid, with a pH as high as 1.4, can destroy the not add a new function; rather, it affects the organ’s functions. drug before it can be absorbed. The stomach acid will break While a drug may have a desired therapeutic effect, it down most substances, whether food or drugs, into their ele- often has additional unintended effects as well. These unin- mental components and therefore neutralize many medica- tended effects, called side effects, may be so noxious that tions in the process. the person stops taking the medicine. Frequently the goal If the drug is either unaffected by the stomach acid, or is of drug research is to eliminate these unwanted side effects. protected from stomach acid, it passes through the stomach For example, early asthma treatments effectively reversed into the intestines. In some cases, the drug is transferred from 624 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. the lining of the intestine and moves into the plasma by a drugs are immediately affected by the C450 system and the simple process of passive diffusion. The mechanics of pas- majority of the drug is inactivated.24–27 To overcome this loss, sive diffusion assume that there is more of the drug, often healthcare providers must administer 10 to 100 times the in the form of a salt, on the inside of the gut’s membranous dose that would be given intravenously (IV). For example, lining than in the blood stream, establishing a concentration propranolol, a popular antihypertensive, is usually given 1 to gradient across that membrane. Whenever a concentration 3 mg IV, whereas the oral dose is 80 to 100 mg. Lidocaine gradient exists, the higher concentration will diffuse across cannot be given orally because it is completely deactivated by the intestinal wall to an area of lower concentration until a the cytochrome P-450 system. To eliminate the effects of fi rst balance of concentrations (equilibrium) is met (Figure 29-4). pass metabolism, many drugs (such as lidocaine) are admin- In some cases, a drug molecule is too large to pass across istered directly into the systemic circulation. the intestinal wall into the blood via passive diffusion. In those cases, a protein carrier will convey the drug across the Parenteral Drug Administration intestinal wall and into the plasma, a process called active When a drug is injected directly into the bloodstream, with- transport. This form of transport requires energy, in the form out going through the gastrointestinal tract (the enteral of adenosine triphosphate (ATP). route), then that drug has been given via a parenteral route. However, many physical factors—including shock states, Examples of parenteral routes include intramuscular injec- which slow absorption, and decreased surface contact time tion and intravenous injection. There are 10 parenteral routes secondary to diarrhea—can affect the absorption of drugs for drug administration. The need for numerous parenteral from the gut into the blood, making the absorption unpredict- routes underscores the signifi cance of fi rst pass metabolism able (Figure 29-5). upon drugs. Once the drug has crossed over the intestinal wall, it is in the hepatic portal system. The hepatic portal system is a subsystem of the systemic circulation. The blood volume in the entire gut is in the hepatic portal system and drains through the liver before rejoining the systemic circulation. This passage through the portal vein permits the liver to detoxify any foreign substance including drugs. The liver’s actions upon the drugs, called fi rst pass metabolism, can markedly reduce the amount of active drug available for the Medication form target organ when it reaches the systemic circulation. These (liquid vs. solid, coated vs. not-coated) Passive diffusion of Passive diffusion of a water-soluble drug a lipid-soluble drug through an aqueous dissolved in channel or pore. a membrane. Acid environment D Food D D D D D D D D ATP Shock ADP D D D Carrier-mediated Diarrhea Drug active transport of drug Figure 29-5 Factors that infl uence drug Figure 29-4 Drugs diffusing into the cell. absorption in the gut. Introduction to Pharmacology 625 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Of the 10 parenteral routes, intravenous (IV) drug infu- are given until a steady state of drug is reached in the blood. sions are generally preferred during an emergency. This is While the drug level is constantly climbing and then falling, due to the fact that drug levels in the blood are obtained more if the repeat bolus is given before the drug’s half-life (t½), rapidly and drug levels can be maintained at more of a steady then the sum of the levels will always be at or above the thera- state. The steady-state level of drug results from a combina- peutic level (Figure 29-7). tion of two factors. On the one hand is the amount of drug An example may help clarify this concept. Lidocaine being infused and on the other, the speed or rate of the infu- has been used to treat ventricular ectopy, irregular beats of sion. If a Paramedic starts at the zero state (with no drug in the heart. A constant infusion of lidocaine would take the bet- the blood) and constantly runs an infusion in, without being ter part of an hour to attain a therapeutic level. To speed the affected by other infl uences, then the amount of drug in the process, the Paramedic would start with a bolus of lidocaine blood will increase at an arithmetic rate until it reaches a to boost the level of lidocaine to the therapeutic range and steady state (Figure 29-6). then start an infusion, an IV lidocaine drip, to maintain that However, attaining a drug’s steady state is not that easy. level. Because of the relatively short half-life of lidocaine, Once a drug is in the bloodstream a number of factors begin the drug level drops below the therapeutic level before the to act upon it. First, and perhaps most importantly, the liver infusion has assumed dominance. This lapse in drug level is starts to detoxify the drug (a process called biotransforma- called the chemical hiatus. Logically, if the chemical hiatus is tion) as the blood passes through the liver. Thus, while a drug is being infused it is also being continuously eliminated. The drug decline is largely a function of the liver’s health Bolus and capabilities. Even with a healthy liver, there is a limited capacity to neutralize a drug. Eventually the drug infusion can overwhelm the liver’s capabilities to neutralize the drug Theraputic and the level of drug in the bloodstream will climb. These window two factors—infusion rate and drug decline—slow the climb of the drug concentration toward a steady state. Instead of a straight linear rise in drug levels, a curved exponential rise is observed. When the drug levels attain the targeted value, as manifested by observation of the therapeutic effect, then Time Bolus the drug is at the therapeutic level (t). When the decline of given drug in the bloodstream reaches 50%, this is equivalent to the drug’s half-life (t½). Steady Infusion On occasion, it is inconvenient to wait for a therapeutic level to be attained by a slow and constant infusion of drug. In those cases a single fi xed dose, called a bolus, is given to rapidly boost the drug to the therapeutic level. Thereafter, an Theraputic infusion is started to maintain the drug at that t-level. window In some other cases, it is impractical to continuously infuse a drug intravenously. Instead, repeated boluses of drug Time Infusion Linear started Exponential Repeat Boluses Theraputic window Time Time Arrows indicate bolus doses Figure 29-6 Linear and exponential drug Figure 29-7 Effects of bolus, steady infusion, infusion rate. and repeat bolus on serum drug levels. 626 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Blood concentration of drug Blood concentration Alternatively, the capillaries of the brain have tight slit junctions, preventing toxins and chemicals, including drugs, Theraputic from easily passing into the brain. This obstacle is referred to window as the blood-brain barrier. For drugs to enter the brain, the drug must be lipid-soluble (i.e., able to be dissolved in lipids [fat]). Since the capillary wall membranes are partially made of lipids, the drug literally dissolves into the capillary wall, passes through to the opposite wall, and moves |
into inter- stitial fl uid in the brain. These drugs are also referred to as lipophilic, meaning attracted to lipids. Time Hiatus The placenta also provides a partial barrier to toxins, such Bolus Bolus as chemicals and drugs, present in the mother’s bloodstream. While certain enzymes within the placental tissue can ren- Figure 29-8 Chemical hiatus and lidocaine der some chemicals inert (e.g., catecholamines such as epi- administration. nephrine), many other drugs are not acted upon or blocked by the placenta and pass easily through the placenta and into the fetus (e.g., narcotics and anesthetics). Paramedics should always keep in mind that drugs which may be at the thera- left untreated, a potentially life-threatening return ventricular peutic blood level (ED50) for the mother may be at the toxic ectopy could occur. To prevent this occurrence, a repeat bolus (LD50) level for the fetus. Also, the placenta offers a less- of one-half the initial dose is given to boost the drug back up to than-perfect barrier for the fetus from these drugs. The rela- a therapeutic level. This practice illustrates all three injection tively nonselective transfer of drugs across the placenta, and techniques: bolus, infusion, and repeat bolus (Figure 29-8). paucity of research regarding placental drug transfer, requires Distribution the Paramedic to be extra vigilant whenever drugs are being given to a pregnant patient. Once the drug is in the bloodstream it is carried to all the body’s tissues and organs. This distribution is affected by sev- eral factors including blood volume, blood fl ow within the Drug Reservoirs tissues, and permeability of the capillary walls. Drugs bind to certain substances in the body and, in doing so, Blood volume can have a dramatic impact on drug distri- form drug reservoirs. A drug reservoir acts as a drug depot, bution. If a patient is hemorrhaging, then the physical amount storing the drug until it is needed. The effect of a drug reser- of blood which can carry the drug is diminished. The body, as voir is to prolong the drug’s action within the body. There are a part of its compensatory mechanisms, redistributes blood to two types of drug reservoirs: plasma protein reservoirs and core organs. However, key organs may not get the medication tissue reservoirs. needed. Even under normal conditions, certain tissues get The plasma proteins of the blood serve as the fi rst drug higher blood fl ow rates than others; for example, the heart, reservoir. The blood contains plasma proteins (e.g., albumin). lungs, liver, and kidneys get more blood than does adipose As a drug enters the bloodstream, it is attracted to the plasma (fat) tissue. The fact that muscle and fat receive less perfusion protein within the blood and forms a union, binding the drug than other organs during a resting state can be used to advan- to the plasma protein. The protein-bound drug is not free to tage. Injection of medication into deep muscles is more likely interact with target organs, and the measurable level of free- to be slowly absorbed into the bloodstream than medications drug in the bloodstream is lower. In effect, the drug is held injected into a vein. in reserve on the plasma protein, in a circulating depository, until needed. Capillary Diffusion There is a limit to the amount of drug that can be bound to Once the drug gets into an organ’s capillary beds, it must pass plasma proteins. Once all available blood proteins are bound through the interstitial fl uid and into the cells directly in order with the drug, then free-drug in the bloodstream becomes for the drug to have its therapeutic effect. Capillary walls have available for tissues. Therefore, not all of the active drug selective permeability to drugs. Slit junctions, physical breaks becomes protein-bound. The difference between protein- in the integrity of the capillary wall, allow the drug to pass b ound and free-unbound drug which is pharmaceutically into the interstitial space. Capillary beds in specifi c organs, active is expressed in terms of a percentage. such as the liver, have large slit junctions. These larger-than- For example, warfarin (a commonly prescribed antico- normal slit junctions facilitate large molecules, including agulant) is 99% protein bound; that means it is 99% bound drugs, to pass easily from the bloodstream into the interstitial to plasma proteins and 1% active drug in the system. For fl uid and then into the hepatic cells. The drug can then be this reason, warfarin stays in the patient’s bloodstream for chemically altered by special enzymes within the hepatic cell long periods of time and the patient need only take the drug into an inert or non-active chemical called a metabolite. occasionally. Introduction to Pharmacology 627 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. The amount of free-drug available from the plasma pro- IV medications, almost all of the drug is usually bioavailable tein reservoir is therefore a function of the amount of blood immediately. proteins in the blood. Albumin and other blood proteins are primarily formed in the liver. The patient who has liver fail- Volume of Distribution ure, secondary to alcoholism, or diseases such as hepatitis After a drug is in the bloodstream (intravascular space), it is unable to produce these blood proteins. Understandably, will enter into the extracellular space, via diffusion and the doses of highly protein-bound drugs, such as propranolol, active transport, where it will come in contact with the target must be adjusted and smaller doses administered. organ’s tissues. Subsequently it will enter the organ’s cells, An impact of aging is the decline in liver function. As where it will have a therapeutic effect upon the cell. While a result, Paramedics tend to administer one half the normal normally the drug should be equally distributed across all dose of highly bound medications, such as lidocaine, to avoid three compartments—the intravascular, the extracellular, and toxicity in this patient population. the intracellular—in drug equilibrium, often this is not the case. Factors that prevent equal distribution of drug across Drug Competition all three compartments include the size of the molecule, There is a limited amount of blood protein available in the protein-binding, and the constitution of the fl uid within the blood plasma at any one time. When two protein-binding compartments. drugs are present, each will compete for the available protein. The last factor, the constitution of the fl uids in the tis- In effect, this increases the level of free-unbound drug for sue, has a major impact on the distribution of drugs (Figure both drugs. For example, both aspirin and warfarin have high 29-9). Some drugs have an affi nity for water. These hydro- protein-binding capabilities. Giving an aspirin, an anticoagu- philic drugs are attracted to the large volume of water that lant, to a patient on warfarin, another anticoagulant, may lead is contained within the extracellular space. Once a drug is to an increased chance of internal bleeding as a result of the in the extracellular space, outside of the central circulation, release of plasma-bound wafarin.28–30 Drug interaction, and it tends to persist longer. It has a longer half-life, because it subsequent increases in blood serum levels of certain drugs is not acted upon by the liver (biotransformation) or kidneys secondary to competition, is a common source of drug toxic- (elimination). ity. A careful medication history from the patient and cross- reference to drug tables will reveal protein-binding capacity Detoxifi cation and potential competition. The body has an incredible capacity to detoxify drugs using the cytochrome P-450 enzyme system. The cytochrome P-450 Tissue Binding system simply transforms a drug—by oxidation, hydrolysis, Some drugs have an attraction to, and will bind with, cer- or reduction—into a water-soluble compound which can be tain tissues. For example, lipid-soluble drugs, the kind that excreted in the urine. This process, called biotransformation, can pass through the blood-brain barrier, are attracted to adi- pose tissue (fat). Diazepam is both highly protein-bound and Total Body Water lipid- soluble. After an initial dose of diazepam is bound to the plasma protein, a percentage of the drug will further accu- Plasma mulate in the adipose tissue. The result is a depot-like effect, with a quantity of drug being stored in the fat for a prolonged period of time. If the patient is given too large a dose, or Interstitial Extracellular Fluid 1/3 repeated doses, then the result may be a persistent drug effect Fluid beyond the desired timeframe. For example, if diazepam is given for sedation, and the patient is obese, then it may take larger doses of the drug to attain a therapeutic level, the clini- cal goal of sedation. However, once the patient is sedated he will tend to remain sedated for a prolonged period of time. Bioavailability Intracellular Once the drug is free within the blood’s plasma it is said to be Fluid Intracellular Fluid 2/3 bioavailable (i.e., capable of creating its therapeutic effect). Bioavailability is the difference between the amount admin- istered and the amount that is bound and unavailable for use. For example, if an aspirin pill with 325 mg of active ingredi- ent is swallowed, and after various factors come into play, only 150 mg is free and unbound in the blood plasma. Thus, less than 50% of the medication is bioavailable. In the case of Figure 29-9 Percentages of volume distribution. 628 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. primarily occurs in the liver, though biotransformation also to arrive at a fi eld diagnosis and then establishing a plan of occurs in the lungs, intestinal lining, and the kidneys. In some treatment are important. instances, pharmacists have taken advantage of this process and administer inert prodrugs that are converted, by the liver, Elimination into their metabolically active form. For example, heroin is a The primary organ for drug excretion is the kidney. The liver’s prodrug that, when acted upon by the liver, metabolizes into cytochrome P-450 system neutralizes toxins, including drugs, morphine. into water-soluble by-products that pass through the kidneys easily. Some drugs, particularly those with a lower molecu- lar weight, pass through the kidney in their active form. This results in a reduced therapeutic level and the need for repeat Street Smart doses of the drug. The majority of drugs and their inactive metabolites are excreted from the kidneys by a process of passive fi ltration. Certain drugs inhibit the cytochrome P-450 enzyme Therefore, free-drugs, those not bound by proteins, and water- system and indirectly increase the levels of circulating soluble drugs are excreted easily, whereas protein-bound and drug. For example, cimetidine hampers the lipid-soluble drugs are not excreted. Filtration, reabsorption, and eventual secretion are also cytochrome P-450 system’s biotransformation of drugs greatly affected by the urine’s acidity. Drugs that are weak like warfarin and phenytoin, to name just two drugs. acids, such as aspirin, are more easily excreted in a slightly alkaline urine. While the kidneys are the primary organ of excretion, sec- ondary organs of excretion do exist. For example, water-soluble drugs (e.g., salts) can be excreted by any exocrine gland, Rates of hepatic metabolism are affected by the health including sweat glands, mammary glands, and saliva glands. of the individual’s liver. Liver cirrhosis (an obstructive dis- Certain drugs, after biotransformation in the liver, are excreted ease), decreased blood fl ow (shock liver), and even old age along with the bile into the intestine. These drug residuals are all conspire to reduce the liver’s ability to metabolize drugs. then passed out along with the feces. Drugs such as anesthet- Outside infl uences can also have an impact on the liver’s |
abil- ics and alcohol are highly volatile and literally “off-gas” into ity to biotransform toxins. Dyes, pesticides, CNS depressants, the lungs, where they are exhaled with every breath. and xanthine derivatives, such as those found in coffee, can The sum of all drug excretion—from the kidneys, enhance the cytochrome P-450 system’s effectiveness, and skin, lungs, and liver—is called the total body clearance. the result is reduced drug serum levels. Hypoperfusion (shock) or diseases of the kidneys, liver, and/ Prolonged exposure to certain drugs causes the liver to or lungs can markedly lower total body clearance, resulting in produce new enzymes to deactivate the drugs, resulting in a a potential toxic accumulation of a drug in the body. decreased blood serum level and a condition called tolerance to be created. It takes increasing doses of drug to overcome the liver’s tolerance of a drug and attain a therapeutic level. Pharmacodynamics Understanding how each drug specifi cally works upon a cell, Toxicity its mechanism of action, helps to explain how the cell will Every drug, in the wrong dose, has the potential to be a poi- respond, how the organ is affected, and the total systemic son. Toxicology, the study of poisons, is therefore a subdisci- response. The study of how drugs come to create their thera- pline of pharmacology. While some think of poisons as those peutic effect is called pharmacodynamics. drugs which, when given in a small amount, can cause death, Drugs can have many effects upon a cell. A drug can this narrow-minded thinking precludes the possibility that cause a cell to increase or decrease its production of proteins, an untold number of other factors could potentiate the drug’s enzymes, and hormones or to inhibit a metabolic function. If effect. This more enlightened perspective is helpful for the the drug inhibits the production of a lipoprotein that is essen- Paramedic who has to treat a patient for whom there is very tial to cell wall production, for example, then the cell wall little background information. will be incomplete and the cell will malfunction. This tactic, It is not the intention of this section to discuss toxicology called chemotherapy, is useful for fi ghting infections. If a in depth, but rather to bring to the Paramedic’s attention that drug cannot differentiate between foreign bacteria and nor- unintentional drug overdoses can be treated with the same mal host cells during chemotherapy, then both cells die in approach as a classic overdose. Unintentional drug over- the process. At fi rst this may appear to be a limitation for a doses, and the resultant toxicity, are a common occurrence drug, but even that situation can been used to a therapeutic whose potential can be mitigated by the Paramedic obtaining advantage. The use of these drugs for cancer patients helps a good history, particularly a good drug history. Also, paying to eliminate the more rapidly dividing cancer cells while pre- careful attention to details like age, weight, sex, and so on, serving a suffi cient mass of host cells for survival. Introduction to Pharmacology 629 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. While there are many different mechanisms of action, of drug that it takes to be potent is called the dose. Dosages the mechanism of action for most drugs can be classifi ed as can vary from person to person, each according to his indi- either drug-receptor interaction, drug-enzyme interaction, or vidual metabolism and genetic makeup. non-specifi c drug interaction. Some individuals develop a resistance to a drug. If this happens, increasing doses of the drug are required to obtain Drug-Receptor Interaction the same therapeutic effect, a development called tolerance. Receptor drugs have an affi nity to a receptor, the portion of Drug tolerance may be the result of the patient’s genetic a cell which attracts a certain molecule. If activation of the makeup, which produces a body chemistry that is less affected receptor causes the cell to react in a specifi c manner, it is or unaffected by the drug. Tolerance may also occur because called a cell receptor stimulator or agonist. If a drug occupies of the development of additional cell receptors. the receptor but does not activate the cell or prevents other The interaction between drugs can occasionally lead to natural receptor molecules from attaching to the receptor, and unexpected or extra effects. For example, two drugs given at the cell is therefore unable to biologically respond normally, the same time may create a new and unexpected third effect. then the drug inhibits the cell and is called an antagonist. That third effect is called synergism. Synergism can be desir- The more a drug is like a naturally occurring chemical able. For example, when promethazine is given with meperi- compound within the body, the more likely that the drug will dine, the effi cacy of the combination is better than each drug have an attraction, an affi nity, to the receptor. In some cases when given on its own. Synergism can also be undesirable, (e.g., epinephrine), the affi nity is extremely strong and the such as when phenobarbital and diazepam are given together. drug is said to be extremely potent. The combined sedative effects can result in central nervous Another infl uence on the drug’s potency is its effi cacy. system depression and respiratory arrest. Once a drug has interacted with a receptor, it may or may not When one drug increases the effectiveness of another cause the cell to react completely; in other words, it may or drug, this is called potentiation. If the drug’s effectiveness is may not have realized its full intended therapeutic effect. The improved, then this may be desirable. Unfortunately, the more better a drug’s ability to stimulate the cell to act, the better its common effect is that one drug is more potent than expected, effi cacy is said to be. Often one of the goals of pharmaceuti- which leads to toxicity problems. cal companies is to increase a drug’s effi cacy. Adverse Drug Reaction Drug-Enzyme Interaction Sometimes a drug creates an unwanted or harmful biological Enzymes act as stimulators within the body, forcing certain response. The subsequent negative impact upon the patient’s chemical reactions to occur within the cell. Enzymes work by health is an adverse drug reaction. When patients experi- combining with a molecule, called a substrate, and acting upon ence an adverse drug reaction, then drug administration is the substrate. Enzyme drugs work by simulating the substrate, stopped immediately and efforts are undertaken to mitigate thereby attracting and engaging the enzyme and preventing the the negative effects of the drug. natural enzyme/substrate combination from working on the cell. Factors that affect if a patient will have an adverse drug These drugs are called antimetabolites because they prevent reaction include extremes of age, extremes of weight, patient the enzymes from stimulating the cell’s metabolism. Certain sex, the time of administration, the patient’s physical condi- cancer drugs, such as methotrexate, are antimetabolites. tion, and genetic factors. Careful attention to these factors and Enzyme drugs can also work by inhibiting the action prompt intervention can create a situation in which, instead of an enzyme directly, thereby preventing the enzyme from of an intolerable adverse drug reaction, a milder side effect is working. The result is that the cell continues to either produce experienced and the patient continues to take the medicine. or break down a chemical. Side effects are other unwanted biological responses to a Nonspecifi c Drug Interaction drug, which are not harmful, adverse drug effects. Whether a patient takes a medication is often a function of the patient’s Some drugs act less specifi cally. For example, mineral oil tolerance to these side effects. Common side effects of many physically coats the intestinal walls and blocks absorption drugs include nausea, dizziness, dry mouth, or diarrhea. Some of nutrients as well as drugs. Other nonspecifi c drug inter- side effects are short-lived. Simple interventions, such as divid- actions include antacids, such as sodium bicarbonate, which ing the dose or slowing the infusion, can make the side effect mix with and neutralize stomach acids. Many of these crude tolerable. For example, a common side effect of nitroglycerin, drug preparations are effective because they often work at a a drug given for chest pain, is dizziness and temporary pos- physical level. tural hypotension. Therefore, to prevent this side effect, the patient should always be forewarned about dizziness and cau- Biological Response tioned about standing quickly after using nitroglycerin. Regardless of the mechanism of action, any drug that is capa- Other side effects, usually long-term side effects, ble of producing the desired therapeutic effect, to affect the can sometimes be mitigated by use of other medications. cell’s function, is considered effective or potent. The amount For example, diarrhea is common with antibiotic therapy. 630 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Therefore, the patient might be instructed to take an antidiar- Type I allergic reactions are often the most severe and rheal medication. can occur within minutes of exposure.34, 35 Also called an ana- phylactic reaction, a type I reaction is mediated by the IgE antibody found attached to mast cells and basophils. Drugs Cultural / Regional differences most accountable for type I reactions are the penicillins and other antibiotics that have a similar structure, including the cephalosporins. The relationship of the patient’s weight to drug dose Type II allergic reactions involve the IgG and IgM anti- is becoming more important in North America as the bodies and lead to an autoimmune response. An autoimmune population tends toward obesity. Several factors response is an unfortunate condition where the body literally attacks itself. Methyldopa, a drug used to treat hypertension, come into play when calculating an appropriate dose has been implicated for drug-induced hemolytic anemia, for of medicine for the obese patient, such as a greater example. volume of blood for drug distribution, altered blood Type III allergic reactions are delayed drug reactions that fl ow (hemodynamics), increased adipose tissue for are caused by the IgG antibodies in the blood. Formerly called serum sickness, the patient experiences symptoms between lipid-binding drugs, and alterations in metabolism in one and three weeks after taking the medicine. Certain anti- general. This subpopulation of patients is at great risk biotics, such as sulfonamides and the anticonvulsant phe- for receiving subtherapeutic doses of medication.31−33 nytoin, have been identifi ed as higher risk for type III drug reactions. A type IV allergic reaction is an infl ammatory reaction secondary to T-lymphocytes and macrophages, such as a con- Allergic Reaction tact dermatitis from poison ivy, that may result from cross- Allergic reactions can be the most problematic of the adverse contamination of topical ointments or crèmes.36 drug reactions, with complications ranging from a contact dermatitis to anaphylactic shock and death. Formerly, terms such as “hypersensitivity,” “drug allergy,” and “anaphylaxis” Idiosyncratic Reaction were used to describe this adverse drug reaction. These three When a drug produces an unpredictable reaction that is not different syndromes (hypersensitivity, drug allergy, and ana- allergic in nature or due to overdose and resultant toxicity, it phylaxis) have a similar mechanism. Whenever a foreign is called an idiosyncratic reaction. An idiosyncratic r eaction substance, such as a drug, enters the body, it can potentially can be described as a highly unusual or abnormal reaction, stimulate the immune response and cause the creation of anti- within a small subpopulation of patients, to a drug that the bodies. These antibody generators (antigens) react with anti- rest of the population can normally tolerate. The basis |
for bodies within the body to form an antigen/antibody complex. these rare idiosyncratic reactions is most likely based in the The antigen/antibody complex, in turn, causes the release of individual’s genetic makeup. Malignant hyperthermia (e.g., certain substances, such as histamine, which then produce the an increased core body temperature caused by exposure classic symptom pattern of an allergic reaction. Currently, to certain anesthetics) is thought to be a genetically linked allergic reactions are designated as types I, II, III, and IV. idiosyncratic reaction. Introduction to Pharmacology 631 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. An understanding of the basic principles of pharmacology, pharmacokinetics, and pharmacodynamics provides a foundation for the Paramedic when learning new drugs. Key Points: • Paramedics must understand the actions of any • Healthcare providers use the Physician’s Desk medications that are to be administered. Reference (PDR) as a source of drug information in • the clinical setting. Drugs originally came from plant, animal, and mineral sources. Many are now synthetically • The Pure Food and Drug Act of 1906 and later produced or genetically engineered. amendments worked to regulate medicine sold • to the public by establishing drug standards and A drug is any material which, when injected, classifi cations. ingested, inhaled, or absorbed into the body, is used for the diagnosis, treatment, or cure of a • The Harrison Act of 1914 made it illegal to obtain disease or condition. “narcotics” without a prescription. • Every drug is assigned three names: • The Controlled Substance Act expanded drug ■ The chemical name is a description of a drug enforcement and placed special restrictions on according to its elemental chemical makeup potentially dangerous and addictive drugs. and molecular structure. ■ The generic name is the drug name listed by • Misuse is defi ned as a drug not being used as the manufacturer; if offi cially listed in the U.S. prescribed. Pharmacopeia, it is followed by the initials USP. • Drug abuse involves the intentional misuse of drugs, ■ The trade name is a unique one given to a drug whether prescription or illicit. by its manufacturer. • • The ratio of effective dose for 50% of the Prescription drugs require a pharmacist to have a population to lethal dose for 50% of the population written or verbal order from a physician or mid- is defi ned as the therapeutic index. level provider to dispense the medication. • • Physicians may choose to use a drug for something Over-the-counter (OTC) medications are available other than its intended use, called off-label use. to self-treat minor illness. This type of medication does not require a prescription. • A drug can enhance a bodily function by either • increasing or replacing a chemical in an organ or by Herbal preparations are a form of OTC medications. blocking the body’s own chemicals. • The Paramedic should inquire about prescription • Pharmacokinetics is the study of how drug medications as well as any herbal products and OTC absorption, distribution, detoxifi cation, and medications the patient may have taken. elimination impact a drug’s therapeutic value. • Information about drugs that are recognized by the • Enteral drug administration involves the absorption Federal Drug Administration can be found using the of a drug via the GI tract by either passive or active United States Pharmacopeia (USP) and National transport. Formulary (NF) drug references. 632 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. • Parenteral drug administration does not use the GI • Synergism occurs when two drugs, given at the tract. Examples include IM or SQ injections and IV same time, create an unexpected third effect. administration. • The unwanted or harmful biological response to a • Distribution of medication is affected by blood drug that has a negative impact upon the patient’s volume, blood fl ow within the tissues, and health is an adverse drug reaction. permeability of the capillary walls. • An allergic reaction is an adverse drug reaction. • Only lipid-soluble drugs pass the blood-brain barrier. It is caused by the body’s response to a foreign • substance which produces the classic symptom The placenta provides a barrier to some pattern of an allergic reaction. Hypersensitivity, medications. drug allergy, and anaphylaxis are syndromes that • Drugs bind to substances, forming plasma protein each have this common response mechanism and reservoirs and tissue reservoirs. can be designated as types I, II, III, and IV. • Pharmacodynamics examines a drug’s mechanism of • An unpredictable reaction that is not allergic in action. nature and that is not due to overdose and resultant toxicity is called an idiosyncratic reaction. • Receptor drugs have an affi nity for a receptor on a cell. A drug is called an agonist if the receptor is • Biotransformation, which primarily occurs in the activated by the drug, which in turn causes the cell liver, detoxifi es drugs by using enzymes to transform to react in a specifi c manner. An antagonist drug the drug into a water-soluble compound that can be occupies the receptor side but does not activate excreted in the urine. the cell. • Toxicology is considered a subdiscipline of • Medication dosages are based on the amount of drug pharmacology. necessary for potency. • Elimination of drugs is primarily carried out by the • Tolerance is the physical need for additional kidneys. The total body clearance is the sum of all amounts of a drug to accomplish the same effect. drug excretion carried out by the kidneys, skin, lungs, and liver. Review Questions: 1. Name fi ve sources of drugs. 8. What factors impact a drug’s therapeutic value? 2. Differentiate between prescription medications 9. What is fi rst pass metabolism? How does it affect and over-the-counter medications. drug development? 3. Differentiate a drug’s chemical, generic, and 10. How does impaired liver function lead to high trade names and give an example of each. or toxic levels of protein-bound drugs? 4. Name at least three drug references. 11. Differentiate between an agonist and antagonist 5. Explain how drug misuse is different than drug drug-receptor interaction. abuse. 12. What is an adverse drug reaction? 6. Describe the steps in the development of a new 13. Differentiate between the three syndromes of drug. an allergic reaction. 7. What is the intended biological effect of any drug? Introduction to Pharmacology 633 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Case Study Questions: Please refer to the Case Study at the beginning of the • When only a partial volume of a prefi lled chapter and answer the questions below: amount of narcotic is given? 1. Which drug laws affect the Paramedic’s • During documentation? administration of a narcotic analgesic? 3. Which drug effect is illustrated by giving Katie 2. What does the Controlled Substance Act of 1970 a pain medication along with a drug to control require of a Paramedic: nausea? • At shift change? References: 1. Centers for Disease Control and Prevention. Life expectancy 16. Barron BA, Bukantz SC. The evaluation of new drugs. Current data: United States. Available at: http://www.cdc.gov/nchs/ Food and Drug Administration regulations and statistical aspects fastats/lifexpec.htm. Accessed at May 27, 2009. of clinical trials. Arch Intern Med. 1967;119(6):547–556. 2. Goldberg H. Hippocrates: Father of Medicine. New York: 17. Welling, P, ed. Drug Development Process: Increasing Authors Choice Press; 2006. Effi ciency & Cost Effectiveness (Drugs and the Pharmaceutical 3. Hippocrates, Francis Adams, Translator. The Genuine Works of Sciences). Stockholm: Informa Healthcare; 1996. Hippocrates. New York: Kessinger Publishing, LLC; 2007. 18. White GG, Love L. The MedWatch program. J Toxicol Clin 4. Logan, Clendening C. Source Book of Medical History. New Toxicol. 1998;36(6):645–648. York: Hoeber; 1942. 19. Meadows M. MedWatch: managing risks at the FDA. FDA 5. Porter R. Greatest Benefi t to Mankind: A Medical History of Consum. 2003;37(5):10–11. Humanity. London: HarperCollins; 1997. 20. Kaldjian LC, Jones EW, Wu BJ, Forman-Hoffman VL, Levi BH, 6. Berndt L.William Withering. Journal of Interventional Rosenthal GE. Disclosing medical errors to patients: attitudes Cardiology. Netherlands: Springer; 2005. and practices of physicians and trainees. J Gen Intern Med. 7. Asimov I. Human Brain: Its Capacities and Functions. New 2007;22(7):988–996. York: Mentor Book; 1965. 21. Kaldjian LC, Jones EW, Wu BJ, Forman-Hoffman VL, Levi BH, 8. Phillips KA, et al. Potential role of pharmacogenomics Rosenthal GE. Reporting medical errors to improve patient in reducing drug reactions: a systematic review. JAMA. safety: a survey of physicians in teaching hospitals. Arch Intern 2001;286(18):270–279. Med. 2008;168(1):40–46. 9. Rodman M, Smith D. Pharmacology and Drug Therapy in 22. Hicks RW, Becker SC. An overview of intravenous-related Nursing (2nd ed.). Philadelphia: Lippincott; 1979:17. medication administration errors as reported to MEDMARX, 10. United States Pharmacopeial. United States Pharmacopeia: a national medication error-reporting program. J Infus Nurs. National Formulary 2005 (United States Pharmacopeia/National 2006;29(1):20–27. Formulary). Washington, DC. United States Pharmacopeial; 2004. 23. Savage SW, Schneider PJ, Pedersen CA. Utility of an online 11. Salerno E. Pharmacology for Health Professionals. St. Louis, medication-error-reporting system. Am J Health Syst Pharm. MO: Mosby; 1999. 2005;62(21):2265–2270. 12. Somogyi AA, Barratt DT, Coller JK. Pharmacogenetics of 24. Jacquot C. Bioavailability and “fi rst pass” effect of a drug. opioids. Clin Pharmacol Ther. 2007;81(3):429–444. Therapie. 1978;33(6):683–697. 13. Inciardi J, ed. Handbook of Drug Control in the United States. 25. Pond SM, Tozer TN. First-pass elimination. Basic concepts and New York: Greenwood Press; 1990. clinical consequences. Clin Pharmacokinet. 1984;9(1):1–25. 14. Forrest G. Chemical Dependency and Antisocial Personality 26. Lalka D, Griffi th RK, Cronenberger CL. The hepatic fi rst- Disorder: Psychotherapy and Assessment Strategies. New York: pass metabolism of problematic drugs. J Clin Pharmacol. Haworth Press; 1994. 1993;33(7):657–669. 15. Krantz JC, Jr. New drugs and the Kefauver-Harris amendment. 27. Kwan KC. Oral bioavailability and fi rst-pass effects. Drug Metab J New Drugs. 1966;6(2):77–79. Dispos. 1997;25(12):1329–1336. 634 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. 28. Andreotti F, Testa L, Biondi-Zoccai GG, Crea F. Aspirin 32. Lee JB, Winstead PS, Cook AM. Pharmacokinetic alterations in plus warfarin compared to aspirin alone after acute coronary obesity. Orthopedics. 2006;29(11):984–988. syndromes: an updated and comprehensive meta-analysis of 33. Erstad BL. Dosing of medications in morbidly obese patients 25,307 patients. Eur Heart J. 2006;27(5):519–526. in the intensive care unit setting. Intensive Care Med. 29. Larson RJ, Fisher ES. Should aspirin be continued in patients 2004;30(1):18–32. started on warfarin? J Gen Intern Med. 2004;19(8):879–886. 34. Untersmayr E, Jensen-Jarolim E. Mechanisms of type I food 30. Jeddy AS, Gleason BL. Aspirin and warfarin versus aspirin allergy. Pharmacol Ther. 2006;112(3):787–798. monotherapy after myocardial infarction. Ann Pharmacother. 35. Romano A, Demoly P. Recent advances in the diagnosis of drug 2003;37(10):1502–1505. allergy. Curr Opin Allergy Clin Immunol. 2007;7(4):299–303. 31. Nieman CT, Manacci CF, Super DM, Mancuso C, Fallon WF, Jr. 36. Brunton L, Lazo J, Parker K. Goodman & Gilman’s the Use of the Broselow tape may result |
in the underresuscitation of Pharmacological Basis of Therapeutics. New York: McGraw-Hill children. Acad Emerg Med. 2006;13(10):1011–1019. Professional; 2005. Introduction to Pharmacology 635 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. KEY CONCEPTS: Upon completion of this chapter, it is expected that the reader will understand these following concepts: • Maintenance of cardiac rate, rhythm, and pumping ability as support for the brain • Autonomic nervous system control • Mechanisms of action of drugs affecting the heart, lungs, and kidneys Case Study: Mrs. Fein called 9-1-1 because she felt faint and very fatigued. One Paramedic interviewed Mrs. Fein while her partner scanned the medication bottles. “Do you take all of these medications?” one Paramedic asked. Mrs. Fein answered, “Oh yes. I always do what my doctors tell me to do. I am so glad that I have so many fi ne doctors to take care of me.” There were multiple antihypertensives, antidysrhythmics, and diuretics. At least four different pharmacies had fi lled the prescriptions. “I see that you go to several pharmacies to have your prescriptions fi lled,” said the Paramedic. Mrs. Fein replied, “Well, each of my daughters likes a different pharmacy and they often pick up my prescriptions for me.” 636 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Pharmacological Interventions for Cardiopulmonary Emergencies 637 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. OVERVIEW The brain, as the source of one’s being and the seat of one’s consciousness, is the most important organ in the body. Perhaps the two most important support systems for the brain in the body are the heart and lungs. These two organs, through constant adjustment and readjustment, ensure that the brain gets suffi cient oxygen and perfusion of glucose-rich blood in order to function. Any disequilibrium between the heart and lungs results in cerebral hypoxia, hypoglycemia, or hypoperfusion. Persistent hypoxia, hypoglycemia, or hypoperfusion can lead to an alteration in mental status, loss of consciousness, and eventually death. Paramedics are frequently called to treat a patient with loss of consciousness, shortness of breath, or cardiac-related problems. The importance of these two interconnected organ systems to the patient’s health cannot be understated. Paramedics must have an intimate understanding of the heart and lung systems and the treatments which they can provide to support them. The Nervous System two-lane highway, information fl ows to and from the brain along the peripheral nervous system. The afferent division is The brain controls these two vital organ systems through the portion of the peripheral nervous system that is stimu- the autonomic nervous system. Therefore, cardiopulmonary lated by the environment (e.g., by heat or by touch) and sends pharmacology is focused on affecting the autonomic nervous a signal to the central nervous system. The central nervous system. To understand the effects of cardiopulmonary phar- system, in turn, interprets the data and sends a signal via macology, the Paramedic must have an expansive knowledge efferent nerve fi bers to the body to react. In some cases, the of the autonomic nervous system. act is voluntary (e.g., to pat a dog’s head). In other cases, the In about 200 A.D., Galen, the father of medicine, identi- act is involuntary (e.g., a quicker heartbeat when faced with fi ed something “non-tendon” in the muscle. He had identi- the threat of a menacing bear). This involuntary control is a fi ed a nerve.1 Later, anatomists would note that stimulation function of the autonomic nervous system. of these nerves caused muscle movement and they sought to discover what other functions nerves provided. Autonomic Nervous System In the mid-1900s, Dr. William Cullen advanced the idea The autonomic nervous system can be thought of as the that the nervous system was responsible for maintaining the body’s autopilot.3 Essential, life-preserving functions, such physiological balance of all organs within the body. He was as digestion, are maintained by the autonomic nervous sys- correct. The nervous system is responsible for the regulation tem. The autonomic nervous system is further divided into of body functions. Through an intricate system of wire-like two divisions: the sympathetic division and the parasympa- fi bers, called neurons, which are present throughout the body, thetic division. These two divisions of the autonomic nervous messages are sent which stimulate the cells within the organs system compete, to some degree, with one another in order to to respond. maintain equilibrium while adjusting to external and internal The Central Nervous System stress. The sympathetic division of the autonomic nervous sys- The central nervous system, which consists of the brain and tem, whose nerve fi bers originate in the thoracic or lumbar the spinal cord, is analogous to the command and control area of the spinal cord, serves to accelerate the body’s organs. center of an army. Information, or intelligence, from the out- Referred to as the “fi ght or fl ight” response, the sympathetic side world fl ows through the spinal cord to the brain to be nervous system increases heart rate, dilates the bronchioles processed. In many instances, the brain sends a command (a to allow more air movement, and constricts blood vessels, signal) to the organs to respond in a certain manner, via the causing the shunting of blood to the vital core organs.4–7 peripheral nervous system. Because of its “crisis” orientation, the sympathetic nervous system tends to create an “all or nothing” response, meaning The Peripheral Nervous System it simultaneously stimulates all of its target organs. The peripheral nervous system consists of the 12 cranial The parasympathetic division of the autonomic nervous nerves and the 31 spinal nerves that extend from the brain system, whose nerve fi bers originate and extend from the cer- and spinal cord to the organs of the body.2 Similar to a vical or sacral area of the spinal cord, is responsible for the 638 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. more vegetative functions. Referred to as the “feed or breed” perception, and mood. Its impact on mood is an important portion of the nervous system, the parasympathetic nervous feature which many anti-depressant medications depend on system increases gastric motility as well as stimulates erec- for their effectiveness (see MAO inhibitors and selective sero- tions in men. tonin re-uptake inhibitors). The vagus nerve (from the Latin word meaning “wan- dering”) is the major parasympathetic nerve. The vagus Neurotransmission nerve originates in the medulla, exits the skull at the base of the brain, travels down the neck (proximal to the larynx), The process of neurotransmission is a cycle (Figure 30-1). branches into the heart and lungs, innervates the stomach, Understanding this is the key to understanding the drugs which passes through the digestive tract, and ends in the anus. can affect the autonomic nervous system. The phases in the Most organs have dual innervations, both sympathetic cycle are preparation for action, feedback, and preparation for and parasympathetic. However, the parasympathetic nervous another action. The speed or strength of a cycle can be increased system usually dominates. For example, the upper portion of or decreased by a drug’s infl uence during that cycle. the heart, the atrium, has both sympathetic and parasympa- To review, the nerve ending makes and stores neurotrans- thetic nerve fi bers. Yet the parasympathetic nerve, the vagus mitter in pockets called “vesicles” in the terminal end of the nerve, dominates, creating a “vagal tone.” neuron. With stimulation, the neurotransmitter is released Certain select organs only have sympathetic innervation. into the space between the nerve and the target cell, called the For example, the adrenal medulla (which excretes the hormone synapse. In the synapse, the neurotransmitter fl oats over to adrenaline), the kidney, and the lower portion of the heart (ven- the cell and attaches to a receptor. Once the cell is stimulated tricles) are innervated by sympathetic nerve fi bers only. to act, the neurotransmitter is released. It is either reabsorbed by the nerve, called re-uptake, after which it is stored in a Neurotransmitters vesicle; or it is broken down by enzymes and excreted. If the The autonomic nervous system transmits its signal to the process of enzymatic degradation or re-uptake and absorp- target organ (the effector organ), causing the organ to act in tion did not occur, the cell receptors would be continuously response to the signal. The transmission of the signal from stimulated (hyperexcited) or exhausted (desensitized). the nerve to the organ is by means of a messenger called a The effects of drugs on the autonomic nervous system neurotransmitter. There are many neurotransmitters in the can be one of two impacts. The drug either increases the central nervous system. neurotransmitter’s ability to stimulate the cell’s receptors The chief neurotransmitter for the sympathetic nervous (agonist effect) or it blocks the cell’s ability to be stimulated system is norepinephrine, which is chemically similar to (antagonist effect). the hormone adrenaline. Because of its utilization of an adrenaline-like chemical, these nerves are also called adren- ergic nerves. Tyrosine The chief neurotransmitter for the parasympathetic ner- 1. Synthesis of vous system is acetylcholine. Because of its use of acetylcho- norepi- DOPA 6. Re-uptake nephrine line, these nerves are also called cholinergic nerves. These terms—“adrenergic” and “cholinergic”—are important to understanding some descriptions of drug effects. Dopamine For each neurotransmitter, there is a corresponding neu- 2. Uptake into storage roreceptor that receives the neurotransmitter, chemically Dopamine– vesicles connecting with it in a key and lock-like fashion. The linkage of neurotransmitter to cell receptor can cause a cell to change the conductivity of an ion channel in the cell wall, thus mak- Synaptic 3. Release of ing it more or less responsive to a stimulus. vesicle + neurotrans- For example, norepinephrine can cause the cell to open mitter Presynaptic its potassium channels, which in turn causes a cascade of receptor events, called depolarization.8–10 This collectively causes the heart to contract quicker and stronger. 5. Removal of Alternatively, the neurotransmitter can stimulate a pro- 4. Binding to norepinephrine tein to perform a certain intracellular function. Serotonin, a receptor Norepinephrine Synaptic space neurotransmitter found primarily in the gastrointestinal tract, is also present in platelets and within the brain. Serotonin, released by damaged platelets, causes arterial and venous con- striction; this is thought to be one of the causes of migraine headaches.11–14 Intracellular response Serotonin within the brain is primarily located in the hypothalamus, where it affects sleep, temperature, pain Figure 30-1 The cycle of neurotransmission. Pharmacological Interventions for Cardiopulmonary Emergencies 639 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Agonist drugs |
work by either increasing the amount of antidepressants; albeit rarely. Physostigmine is an example neurotransmitter (a direct effect) or decreasing the amount of a parasympat homimetic, a drug that mimics the action of of re-uptake or enzymatic degradation, thereby indirectly the parasympathetic neurotransmitter acetylcholine. increasing the amount of neurotransmitter. In both cases, Another anticholinesterase drug with parasympathomi- these drugs would be considered an agonist. metic properties is neostigmine bromide. Neostigmine is used Alternatively, a drug can act to block the neurotransmitter, to help reverse the effects of certain neuromuscular blocking and thus act as an antagonist. Drugs in this class work by either agents, called paralytics, which are used during emergencies decreasing the amount of neurotransmitter, increasing enzymatic to facilitate intubation.19 destruction of the neurotransmitter, or by competing with the neurotransmitter for the receptor, called competitive inhibition. Anticholinergic Agents Cholinergic Receptors Cholinergic blockers, those drugs that block acetylcholine Acetylcholine attaches to cholinergic receptors within the para- from binding to either muscarinic or nicotinic receptors, are sympathetic nervous system. These cholinergic receptors can called anticholinergics. Drugs in this classifi cation would be further divided into muscarinic and nicotinic receptors. stop parasympathetic activity. Originally, the muscarinic receptors were identifi ed for Antimuscarinic drugs inhibit parasympathetic activity their affi nity for muscarine, a poison found in mushrooms. at the muscarinic receptors. Their greatest impact is on the Five different muscarinic receptors (M1-M2-M3-M4-M5) core organs, such as the eyes, the gut, and the heart, because have been subsequently identifi ed.15,16 For example, M2 recep- peripheral skeletal muscle primarily has nicotinic receptors. tors have been found in the cell wall of cardiac muscles. An example of a muscarinic blocker is atropine sulfate. Nicotinic receptors, the other cholinergic receptor, are Atropine sulfate is a plant alkaloid derived from the deadly located in the adrenal medulla, the central nervous system, nightshade plant (latin—atropa belladonna).19 Its fruit, a and at many neuromuscular junctions, such as the muscles small black cherry, is poisonous. It was used, in small quan- within the bronchioles. Similar to muscarinic receptors, nico- tities, by Ladies of the Court in medieval Italy to add “bril- tinic receptors were identifi ed for their affi nity to nicotine. liance” (pupil dilation) to their eyes; hence the name “bella Blockage of the nicotinic receptors, an antagonist effect of donna” or beautiful lady. The name “atropine” comes from drugs like pancuronium, results in smooth muscle paralysis, the Greek atropos, one of the Fates who held the shears to cut diaphragmatic paralysis, and respiratory arrest. the thread of life. This reference is interesting in light of the The main neurotransmitter that connects with either fact that atropine is used to treat life-threatening bradycardia. a muscarinic or nicotinic receptor is acetylcholine. Any Atropine’s effect is to block the vagus nerve (parasympathetic chemical that mimics the action of acetylcholine (e.g., nic- nerve) in the heart and reduce the vagal tone that slows the heart, causing the heart rate to rise.20 otine) is said to be a parasympathomimetic agent. Poison mushrooms often contain muscarinic-like chemicals that are Because it is a parasympathetic blocker, atropine also cholinomimetic.17,18 decreases saliva production in the mouth, leaving the mouth dry (xerostomia). This effect is desirable prior to intubation. Atropine is also used as a pretreatment to prevent bradycardia Cholinergic Agents induced by vagal stimulation of the hypopharynx, which is The action of acetylcholine on the heart is to slow its rate occasionally seen during pediatric intubation. through direct stimulation of the vagus nerve. Any drug Atropine has received more interest lately as an antidote which has a similar action, that mimics the effects of acetyl- for certain nerve agents used as weapons of mass destruction. choline, would be called a cholinergic drug. Drugs of this sort These nerve agents are structurally similar to the organophos- usually have a subcomponent of acetylcholine, such as an phate fertilizers. This treatment works by blocking parasym- ester or alkaloid-like molecule of acetylcholine, which binds pathetic receptors. Atropine is now available in auto-injectors directly to the cholinergic receptor. Pilocarpine is a drug in for deep IM injection during an exposure to these deadly this classifi cation. nerve gasses.21–24 Using an alternative mechanism to increase the amount The alternate anticholinergic is the nicotinic blocker. of naturally occurring acetylcholine available, some drugs Nicotinic blockers have been used for decades in the operat- bind with the enzyme that breaks down the acetylcholine ing room as a muscle relaxer. The earliest nicotinic blocker, (acetylcholinesterase), thus rendering the enzyme inert. As curare, owes its origin to tribesmen in the equatorial Amazon. a result, less acetylcholine is broken down and there is more These tribesmen would easily bring down large animals, acetylcholine available in the synaptic junction. An exam- without killing them, by arrows that were dipped in curare. ple of a drug that uses this mechanism is physostigmine, The animal was seemingly paralyzed and died from suffoca- a drug used to treat open-angle glaucoma. Papillary con- tion while still awake. In the 1850s, Claude Bernard showed striction (miosis) is controlled by the parasympathetic ner- that the South American Indian drug curare worked primar- vous system. Physostigmine is also used to treat overdoses ily at the neuromuscular junction and that a substance, later of atropine (whose action is discussed later) and tricyclic identifi ed as acetylcholine, was blocked from receptors on 640 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. the muscle cell. The idea that cells had receptors which could Adrenergic Neurotransmitters be affected by drugs had wide ranging implications for phar- Adrenergic neurotransmitters function in a manner similar to maceutical research.20 cholinergic neurotransmitters except that they act on the sympa- Curare was a crude cholinergic blocker that was spe- thetic nervous system. In the sympathetic nervous system nor- cifi c to the nicotinic receptors found in skeletal muscle. By epinephrine, not acetylcholine, is the primary neurotransmitter. blocking acetylcholine from attaching to nicotinic receptors Similar to the process in the parasympathetic nervous on skeletal muscle, the muscles were, in effect, paralyzed. system, the sympathetic (adrenergic) nerve produces norepi- The advantages of a drug which could paralyze are numer- nephrine. To produce norepinephrine, the neuron takes the ous. For example, a paralyzed patient is easier to intubate amino acid tyrosine and synthesizes it into dopamine, which and mechanically ventilate.25–27 Used together with sedatives is in turn converted into norepinephrine in the vesicles. and analgesics, these drugs have created an ideal intubation Norepinephrine is released from the vesicle, by an infl ux condition. Paralytics, as a class, do not cross the blood-brain of calcium that occurs with neuronal stimulation, and fl oods barrier easily. Therefore, while the patient is paralyzed, he the synapse between the nerve and the target cell. Attracted remains completely awake and sentient (sensing surround- to adrenergic receptors on the cell wall membrane, the nor- ings) and can experience feelings of pain. It is standard epinephrine binds with the cell receptor and activates the practice to co-administer a sedative and/or pain medication enzyme adenyl cyclase, in a second messenger system, to (analgesic) along with the paralytic agent to decrease the convert adenosine triphosphate (ATP) into cyclic adenosine patient’s anxiety and relieve discomfort while paralyzed. monophosphate (cAMP), releasing two phosphate molecules Some paralytics, particularly the early nondepolarizing in the process. The two liberated phosphates are an energy- agents, release histamine, a vasodilator, from the mast cells in rich substrate which is used by many proteins within the cell the blood. Therefore, the patient’s blood pressure would fall. to power metabolic processes (Figure 30-2). The next generation of paralytics (e.g., pancuronium) does not After having caused the intended effect, the norepineph- release histamine and therefore is more useful when treating rine is released from the receptor and may either diffuse into patients at risk for hypotension, such as the trauma patient. the general circulation or be taken up again by the adrenergic neuron. Depolarizing and Non-Depolarizing The norepinephrine, assisted by an ATPase (enzyme), re- Neuromuscular Blockers enters the neuron where it can either be stored in a vesicle or broken down by monoamine oxidase (enzyme) into inactive Neuromuscular blockers can be classifi ed as either depo- by-products (metabolites). larizing or non-depolarizing. Depolarizing agents attach to the nicotinic receptor at the neuromuscular junction. In the Adrenergic Drugs resting state, the cell has charged sodium ions on the outside and potassium ions on the inside of the cell. This results in a It is important for the Paramedic to understand the sympa- difference in the electrical potential between the outside of thetic response because many drugs owe their therapeutic the cell and the inside. This difference is called the resting effect to the impact of these adrenergic drugs in the process of membrane potential. With the nicotinic receptor stimulated neurotransmission. For example, cocaine prevents the uptake by the drug, the cell opens the sodium channels in the cell of norepinephrine, thereby causing a buildup of norepineph- wall and a rapid infl ux of sodium occurs. This results in depo- rine in the synapse, and hyperstimulation of the cell.28,29 larization and subsequently causes a cascade of events which Norepinephrine is an important neurotransmitter in the then cause muscular contraction. These transient fi ne muscle central nervous system (CNS). Inhibition of uptake of norepi- contractions, seen after administration of a depolarizing neu- nephrine by tricyclic antidepressants, or the blockade of mono- romuscular blocker, are called fasciculations. amine oxidase (MAO) breakdown of norepinephrine by MAO The depolarizing paralytic agent, however, remains bound inhibitors, can improve clinical depression, for example.30 to the receptor, unable to be broken down easily by the nor- There are two adrenergic receptors in the sympathetic mal enzymes. This persistent action of depolarizing agents nervous system: the alpha-receptors and the beta-receptors. prevents the repolarization of the cell and a return of the cell These adrenergic receptors are further divided into alpha or 1 to its normal resting state. Instead, the cell and the muscle alpha according to the organs on which they predominate 2 remain fl accid (unable to be stimulated) and paralyzed. (Figure 30-3). For example, beta receptors are found on car- 1 As an alternative, non-depolarizing paralytic agents also diac muscle cells whereas beta receptors are found on arte- 2 bind with the nicotinic receptor but do not have the same rial smooth muscle and bronchial smooth muscle.31–33 effect on the cell. These agents simply bind to a receptor with- out causing depolarization. With the receptor site occupied, Adrenergic Agents the cell remains in a ready resting state. However, the cell is Several drugs have been created which mimic the effects unable to be stimulated because the receptor is blocked. This of the sympathetic neurotransmitter norepinephrine. These prevents the unwanted muscular fasciculations seen with drugs are called sympathomimetics. Sympathomimetics depolarizing agents. (often either prodrugs or analogs of norepinephrine) share a Pharmacological Interventions for Cardiopulmonary Emergencies 641 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Presynaptic neuron isoproterenol—all have similar effects on the cardiovascular Direction of conduction system.34 These drugs elevate blood pressure and thus are of nerve impulse also called vasopressors. However, each drug has an action Vesicles containing that is slightly different from the others, thus making one neurotransmitters more desirable than another for different circumstances. The indirect adrenergic agonists are stimulants that cause Mitochondrion the release of norepinephrine. An example of an indirect adren- Synaptic ergic agonist is the class of drugs called amphetamines. cleft Systemic Pharmacologic Effect Owing to the widespread distribution of adrenergic receptors in the major core organs, and the often dramatic effect these sympathomimetic drugs can have upon the sympathetic ner- vous system, a |
review of systems will be discussed. The heart may be the organ system most affected by adrenergic agonists. These powerful medicines can markedly increase the heart’s strength of contraction (positive inotro- pic effect) as well as rate (positive chronotropic effect) as a result of increased calcium infl ux in the myocardium. The calcium infl ux causes a higher action potential and quicker depolarizations. Left alone, stronger, faster contractions lead to more complete ventricular emptying and an increased car- Postsynaptic Receptors on postsynaptic neuron membrane bound to neurotransmitter diac output. Catecholamines, such as epinephrine, can be potent car- Figure 30-2 Neurotransmission. diac stimulators. This is the anticipated action of epinephrine during a cardiac arrest. Epinephrine should either (1) increase common base molecule, a catechol ring. Thus, they share a the fi brillatory action of the arrested heart, coarsening the drug classifi cation, and are called catecholamines. ventricular fi brillation, so that subsequent defi brillations are All catecholamines are very potent adrenergic agonists more likely to be successful, or (2) induce spontaneous pace- because they can cause a direct response from the adrener- maker activity in the heart in cardiac standstill (asystole). gic receptor. In fact, most catecholamines, such as dopamine Conversely, catecholamines like epinephrine, when inap- and epinephrine, have naturally occurring counterparts in the propriately administered, can induce spontaneous depolar- body. Because of this, the body also has a means of breaking izations and extra-systoles by the same mechanisms. These down the drug more rapidly; in this case, with the enzymes actions can disrupt a normal cardiac sequence and send the monoamine oxidase (MAO) and another enzyme called heart into chaos and ventricular fi brillation. catechol-O-methyltransferase (COMT). In order to maintain The peripheral capillary beds are largely controlled a therapeutic effect, these drugs are continuously infused by alpha receptors of the sympathetic nervous system as 1 intravenously. The infusion is then slowed, a process called well.35,36 During times of stress, when blood is needed in the weaning, to the point where the body is able to sustain itself core organs, these capillary beds can be preferentially shut and is no longer dependent on the infusion to maintain vital down. Blood will then be directed toward the body core in a functions such as blood pressure. process called shunting. This shutdown of capillary beds also Realizing the limitations of catecholamines, newer non- causes a higher total peripheral vascular resistance (PVR) to catecholamine compounds have been created (i.e., those forward blood fl ow. without catechol ring). Without the ring, the enzymes COMT In certain abnormal perfusion states, such as anaphylactic and MAO have more diffi culty neutralizing the drug into shock or septic shock, peripheral vascular resistance is reduced. an inactive metabolite. Therefore, these drugs enjoy a lon- Then catecholamines, such as dopamine or norepinephrine, ger duration of action. Ephedrine, a common ingredient in can help to restore a higher PVR. decongestants, is an example. Administration of catecholamines, such as dopamine, Adrenergic agonists may work by direct action or by can result in a higher PVR through alpha receptor stimula- 1 indirect action. Direct acting adrenergic agonists couple with tion. While dopamine is a very useful drug when used appro- and excite the adrenergic receptors. The indirect agonists priately, a high PVR presents an obstacle to forward blood cause the release of norepinephrine from the terminal neu- fl ow from the heart (i.e., cardiac output). This effect can cre- ron, which in turn causes the norepinephrine to attach to the ate such a large demand on the heart’s muscle that it cannot adrenergic receptors and the receptors to react. keep up with demand and the patient may manifest symptoms The five direct-acting adrenergic agonists— such as chest pain (angina) and possibly sustain a myocardial norepinephrine, epinephrine, dopamine, dobutamine, and infarction. 642 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Pupils dilate Mobilization of glucose Increased heart rate Relaxation of bronchial tree Release of epinephrine by adrenal gland Slowdown of digestive process 8910010110760 20 114300Increased 0 0 blood pressure Figure 30-3 The effects of adrenergic receptor stimulation. The differences between the effects produced by each of the catecholamines, and even the differences between the Street Smart effects of a single catecholamine at different doses, requires careful monitoring of the patient for untoward effects. The smooth muscles of the bronchi and the bronchioles Topically applied, epinephrine and epinephrine are also richly supplied with beta receptors and are easily derivatives such as phenylephrine can create a 2 affected by catecholamines. When activated, these receptors localized vasoconstriction in exposed capillary beds in cause dilation of medium-sized airways. This positive effect the mucosa. A solution sprayed into the nasal mucosa is so pronounced that these agents have become a mainstay in the treatment of bronchoconstriction and are discussed in of the nostril prior to intubation can reduce the more detail in the section on drugs that affect the respiratory likelihood of bleeding during a nasal intubation.37,38 system. The key to successful use of these agents is to apply One of the notable effects of catecholamines on the them before other lubricating substances and in time endocrine system is the increase in the amount of blood glu- cose available to be used as energy. This is achieved through for the medication to take the desired effect. Upon a combination of decreased insulin secretion from the pan- quick visualization, the mucosa should appear pale creas and increased breakdown of glucagon in the liver and after vasoconstriction has occurred. muscles. The intended effect of the elevated blood glucose Pharmacological Interventions for Cardiopulmonary Emergencies 643 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. levels is to have more fuel for an active metabolism during (beta selective agents). Cardioselective drugs, such as 2 an emergency. atenolol, only affect the heart, which predominantly has beta receptors, and prevent catecholamine-stimulated tachy- 1 Alpha-Adrenergic Blockers cardia. This effect can have a signifi cant impact on mortality Most alpha-adrenergic blockers are competitive b lockers, and infarction size during acute coronary syndrome. occupying the adrenergic receptor and preventing the Beta-blockers, particularly nonselective beta-blockers, catecholamine drug from attaching to the adrenergic receptor. are used to treat hypertension. These beta-blockers, such as Alpha-adrenergic blockers can be divided into either long- propranolol, prevent peripheral vasoconstriction and subse- acting and short-acting or competitive and noncompetitive. quent increased peripheral vascular resistance with the over- Noncompetitive antagonists are longer acting and generally all result of a lower blood pressure. used for special conditions. For example, a pheochromocytoma, Caution should be advised any time a beta-blocker is a tumor of the medulla of the adrenal gland, can induce life- given to a diabetic patient. Beta-blockers can mask many of threatening hypertensive crisis through secretion of high doses the classic signs of hypoglycemia. Concerns about hypogly- of epinephrine. The use of longer-acting alpha a ntagonists, cemia, secondary to history or physical, should be followed such as phenoxybenzamine, can reduce dangerously high up with a blood glucose measurement. blood pressures. Longer-acting alpha antagonists are also used to relieve the symptoms of benign prostate hypertrophy (BPH). BPH is a common consequence of aging for men. Alpha-adrenergic Street Smart blockers relax the bladder muscles, allowing for a greater passage of urine. A patient who is under treatment for BPH Sudden withdrawal of a beta-blocker may result with a long-acting alpha antagonist, who subsequently needs hemodynamic support from a catecholamine infusion, such in symptoms of an acute coronary syndrome, as dopamine, will not respond as briskly secondary to com- including chest pain (angina), rebound hypertension, petition from the alpha-adrenergic blocker. tachycardia, and bronchospasm. Patients on beta- Competitive short-acting alpha antagonists, such as blockers should be weaned off the medicine slowly to phentolamine, are more commonly used to treat acute hyper- tensive crisis, especially hypertension secondary to a pheo- prevent these symptoms. Prehospital treatment may chromocytoma. Its emergency application can also prevent include re-instituting the beta-blocker intravenously acute hypertension and stroke secondary to an overinfusion until the patient stabilizes. Only a complete drug of a catecholamine, such as a “runaway” dopamine infusion. Cerebral vasoconstriction is thought to be one of the history would reveal that the patient’s symptoms are causes of migraine headaches. Logically, an alpha blocker the result of suddenly not taking his beta-blocker. would prevent or reverse any vasoconstriction created by the sympathetic nervous system. Ergot is an alpha-adrenergic blocker used to treat both dementia and migraine headaches. A plant alkaloid, ergot is extracted from a fungus which grows Pharmacological Interventions on rye. Another extract of note from this extraction is lysergic acid diethylamide (LSD). during a Respiratory Emergency Ergot compounds are thought to depress the central ner- The pulmonary system, starting at the pharynx and end- vous system’s vasomotor centers and thus inhibit the pulsa- ing in the capillary beds surrounding the alveoli, through tions, described as pounding by the patient, characteristic of mechanical ventilation and pulmonary respiration, is a migraine.39,40 Ergot compounds do not treat migraines, they responsible for oxygenation, removal of wastes (including only prevent them from occurring and thus must be taken early carbon dioxide), and the regulation of acid–base balance. during the aura phase in the attack in order to be effective. When any one of these functions is disrupted, illness and even death can ensue. Airfl ow into the lungs is partially con- Beta-Adrenergic Blockers trolled by the diameter of the airway passages, the absence Beta-adrenergic blockers, more commonly called beta- of obstructions, and proper air pressure gradients. Of these, blockers, can be divided into two classes: selective and non- the diameter of the airway may be most important. The air- selective. Nonselective beta-blockers inhibit both beta and ways within the tracheobronchial tree are surrounded by 1 beta receptors by direct competition with norepinephrine smooth muscle arranged in a double helix, like a Chinese 2 for available receptors. This mixed effect can be problematic fi nger-trap, which expands and contracts. This increases or depending on the desired therapeutic outcome. decreases the airway’s lumen. Beta-selective drugs specifi cally target either the heart, All muscles within the body are controlled by the ner- and are referred to as cardioselective, or target the lungs vous system, and the muscles in the airway are no exception. 644 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Parasympathetic nerves (from the vagus nerve) narrow the airway’s lumen, called bronchoconstriction, while the sym- Street Smart pathetic nerves widen the airway, called bronchodilation. Some OTC medications used to self-medicate asthma Overview of Pulmonary have epinephrine as their main ingredient (e.g., Pathophysiology Primatene Mist™). In an effort to obtain relief from The majority of pulmonary diseases can be linked to what the asthma symptoms, patients may not follow is referred to as the “three S’s”: spasm, swelling, and secre- tions. Bronchospasm, as manifested in the wheezing of an medication instructions on the package insert. asthmatic patient, is a narrowing of the airway or broncho- As a result, undesirable cardiotoxic effects can constriction.41 This bronchoconstriction is the result of stim- arise, including chest pain (angina) and myocardial ulation of the muscarinic receptors of the parasympathetic nervous system. infarction from the resulting beta-adrenergic Any irritant, such as pollen and aerosolized medications, overstimulation. can stimulate this protective airway refl ex. The muscarinic |
receptors, in turn, stimulate the production of cyclic GMP, which causes the muscle contraction and subsequent broncho- to be administered by inhalation, injection (sublingual), or constriction. Cyclic GMP can also cause the release of chemical intravenous infusion, isoproterenol does not have the alpha mediators from mast cells, such as histamine and leukotrienes. effects of epinephrine. However, it still causes the same car- One common bronchospastic respiratory illness treated diotoxic effects. by Paramedics is asthma. Asthma is a potentially reversible airway spasm that is triggered by a stimulus. The stimulus Beta-Selective Drugs can either be an internal or intrinsic trigger, such as stress or Improvements and refi nements have led to a group of exercise, or it can be an external or extrinsic trigger, such as drugs that is more highly selective for beta receptors and 2 pollen, dust, and mold. has little or no impact on beta receptors. These drugs are 1 The severity of a patient’s disease can be classifi ed called beta-selective adrenergics. The fi rst beta-selective according to the frequency of exacerbations experienced. adrenergic drug (isoetharine) was still a direct-acting cat- An occasional exacerbation or asthma attack (less than once echolamine derivative (i.e., sympathomimetic), but had or twice a week) is considered mild intermittent asthma and weak beta properties. 1 is treated with episodic medications intended to treat bron- The next generation of beta-selective drugs was non- chospasm and infl ammation. More frequent attacks, and catecholamines. Non-catecholamine drugs had signifi cant particularly those which occur while asleep, are treated with advantages over earlier catecholamine-based drugs. The routine medications on a daily basis in an attempt to prevent body has enzymes, such as MAO and COMT, to break cat- bronchospasm and infl ammation. Persistent bronchospasm echolamines down at the neuromuscular junction. The non- that is resistant to routine treatments, called status asthmati- catecholamine drugs were not as strongly affected by these cus, can lead to suffocation and death and must be treated enzymes and thus their effects tended to last longer. The non- aggressively.42–45 catecholamine drugs were also more discriminating, having An asthma exacerbation can be treated with an aerosolized primarily beta effects and almost no beta effects. 2 1 beta-agonist, often called a “rescue drug,” such as albuterol. The importance of immediately administering rescue drugs to an asthmatic patient in distress cannot be understated. Street Smart The earliest treatment for asthma, sympathomimetic epinephrine, is still used today. Whether given subcutane- ously or inhaled, epinephrine proved effective in reversing Terbutaline causes the relaxation of the smooth bronchospasms, and every other rescue drug since has been muscles in the bronchial tree, the blood vessels of some derivative of epinephrine.46 Epinephrine is not without skeletal muscle, and the uterus. Uterine its side effects. A nonselective adrenergic stimulant, epineph- contractions during labor can be slowed, a process rine causes tachycardia and palpitations (the feeling of one’s own heart racing), peripheral vasoconstriction (which raises called tocolysis, by administration of terbutaline. the PVR and the work of the heart), as well as restlessness, This effect may be useful in cases of high-risk anxiety, and insomnia. pregnancy or delays in transportation to a The next generation of asthma medications is intended to reduce these undesirable side effects. They still affect the tertiary care center (e.g., during a snowstorm beta receptors. The prototypical medication in this class, or fl ood). 2 a nonselective beta-adrenergic drug, is isoproterenol. Able Pharmacological Interventions for Cardiopulmonary Emergencies 645 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. The model non-catecholamine beta-selective drug is albuterol. Albuterol stimulates the beta receptor to produce 2 Street Smart the cAMP, which results in smooth relaxation without stimu- lating the heart to race (beta effect) or the blood pressure to 1 rise (alpha effect). The metered dose inhaler form of ipratropium was 1 made with components similar to peanuts and was Xanthine Derivatives not recommended for use in the peanut-allergic patient in the past. Presently the metered dose The active ingredient in coffee and teas is caffeine, another plant a lkaloid, which is perhaps the most widely used stimu- inhaler form of ipratropium has been reformulated lant in the world. Caffeine, a xanthine derivative, relaxes with a non-peanut based propellant and is safe for smooth muscle in the bronchial tree, stimulates the heart, and use. The premixed nebulized solution of ipratropium stimulates the CNS. More discussion about caffeine can be found on the section on drugs which affect the CNS. does not contain these components and is safe and The liver converts xanthines, as a prodrug, to theophyl- benefi cial to the patient experiencing an acute line, which causes bronchodilation. For a variety of reasons, bronchospastic airway reaction. most notably cigarette smoking, the conversion to theophyl- line can be unpredictable and toxicity is not unusual. As a class, xanthines work by inhibiting an enzyme (phosphodiesterase), which results in an increase in cAMP Prophylactic Medications and GMP, which in turn alters calcium levels in the muscle for Pulmonary Disease as well as blocking adenosine receptors. The end result is The actions of prophylactic asthma medications generally bronchial dilation. Methods of administration of theophyl- revolve around decreasing infl ammation (specifi cally, prevent- line compounds include orally in a liquid, intravenously as ing the degranulation of mast cells) and subsequent releasing of an infusion, and rectally as either a suppository or a reten- histamine, prostaglandins, and leukotrienes (leukotrienes were tion enema. known as slow reaction smooth muscle-stimulating substance Unfortunately, xanthine derivatives interact with several (SRS)—the name is descriptive of the action of leukotrienes). other commonly prescribed drugs. For example, phenytoin, Histamine and leukotrienes cause swelling, bronchospasm, a commonly prescribed anticonvulsant, causes an increase and subsequent narrowing of the lumen of the airways. in xanthine metabolism, leading to subtherapeutic levels of Cromolyn, a mast cell stabilizer, inhibits the release of xanthine as well as lower levels of phenytoin. Subtherapeutic histamine, prostaglandins, and leukotrienes from mast cells, levels of phenytoin for patients with a seizure disorder can in part, by stabilizing the cell wall via blockage of calcium result in a breakthrough seizure. ion channels in the cell wall. Cromolyn is therapeutically Cigarette smoking, mentioned earlier, also interferes equal with a maintenance dose of theophylline and has fewer with theophylline metabolism. The dose of theophylline for side effects than theophylline. For this reason, cromolyn has smokers has to be increased between 50% and 100% because largely replaced theophylline as a prophylactic agent for the of increased metabolism. Due to the unpredictable therapeu- treatment of asthma. tic level, the narrow therapeutic index, and undesirable side A new class of anti-infl ammatory drugs, called leuko- effects, theophylline use has markedly decreased as newer triene antagonists, are becoming available. Drugs in this class medications with more tolerable side effects have been proven block leukotriene receptors. Leukotriene is the slow-acting equally effective. substance of anaphylaxis that causes mucous plugs and constricts bronchial airways. Leukotriene antagonists, such as zileuton, have the distinction of affecting all three of the Cholinergic Antagonists “S’s” of pulmonary disease (swelling, secretions, and spasm). As a class, cholinergic antagonists are not as effective as Leukotriene antagonists are indicated for the treatment of bronchodilators but rather prevent further bronchoconstric- long-term or chronic asthma. tion by occupying the muscarinic receptors on the bronchial Commonly prescribed inhaled corticosteroids reduce smooth muscle that cause bronchoconstriction. Treatment infl ammation as well, but by a slightly different action. of bronchospasm with anticholinergic medications is most Corticosteroids stabilize lysosomal membranes, preventing effective either immediately preceding the bronchospasm or the release of hydrolytic enzymes which produce the infl am- immediately after treatment with a bronchodilator, to prevent matory response in the tissues, as well as decrease the pro- a return of bronchospasm. Therefore, during the treatment duction of leukotrienes. of reactive airway diseases such as asthma, beta-selective Inhaled corticosteroids have many systemic side effects, adrenergic drugs are preferred. However, concurrent admin- including cough, dizziness, and headache. Newer generations istration of cholinergic antagonists, such as ipratropium, is a of corticosteroids have been developed which reduce some of common practice.47 these unwanted side effects. 646 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Caution regarding corticosteroids is advised. Cortico- nurses out-of-hospital demonstrated the effi cacy of prehospital steroids suppress secretion of hormones from the hypothala- care and ranging to today’s 12-lead ECG technology, EMS has mus, pituitary, and adrenal glands. Sudden withdrawal from always had a focus on cardiac care. corticosteroids can precipitate a potential acute adrenal insuf- The Paramedic’s fi rst mission was and still is to reduce fi ciency, or Addisonian Crisis. Patients taking steroids must dysrhythmic death. The use of cardiac medications, as an be gradually weaned off corticosteroids, by tapered doses, adjunct to rapid defi brillation and cardiopulmonary resus- while the body readjusts. citation, is thought to have had a signifi cant impact on the morbidity and mortality from cardiovascular disease and continues to be the mainstay of advanced cardiac life sup- Mucolytics port. Therefore Paramedics must have an understanding of Thickened secretions in the airway obstruct the airway and the indications and mechanism of action of many cardioac- serve as a breeding ground for infection. These secretions tive drugs in order to effectively and effi ciently treat their are diffi cult to expel (expectorate), leading to partial airway patients and prevent sudden cardiac death. obstructions via mucous plugs, as well as acting as a foci for Today, the mission of EMS is even more complex, infl ammation and infection. For these reasons, it is important and advances in cardiology have added new demands on to clear these secretions from the airway. Paramedics. Paramedics must not only understand the drugs Mucus is made up of a combination of protein-like mate- which prevent or treat cardiac arrest, but also drugs that are rials, and complex sugars called polysaccharides. Sputum, used in the treatment of acute myocardial infarction. mucus with cellular debris such as white blood cells (leuko- In the past the diagnosis of a “heart attack” (acute myo- cytes) and bacteria, is largely made up of water. By adding cardial infarction) was viewed as an inevitable death sentence. physiologic saline (0.9% sodium chloride in sterile water) to Today, new drugs, such as fi brinolytics, and new technologies, the airway, via aerosol or bolus fl ush, the thinned sputum is such as angioplasty, can literally halt the myocardial damage, easier to remove by suction. but only if the patient can obtain these treatments in time.48 Ridding the airway of thickened secretions, called pulmo- This changing focus from dysrhythmic death (mortal- nary toilet, can also be achieved through sterile endotracheal ity) to myocardial salvage (morbidity) has even changed the suctioning, hydration (oral or intravenous), and administra- nomenclature. Acute myocardial infarction, an event once tion of drugs which thin the secretions, called mucolytics. seen as occurring in isolation, is now looked upon as a part of Mucolytics physically break down the viscosity of mucus the acute coronary syndrome (ACS). ACS is a complex of by breaking apart the mucoprotein structure. An example of a symptoms associated with the continuum of cardiovascular commonly used mucolytic is acetylcysteine which is absorbed disease, emphasizing its morbidity (and more importantly, its directly into the airway and exerts a local effect. Acetylcysteine mutability) and not simply its mortality.49–51 begins to work within one minute and peaks in as little as 5 to 10 minutes, destroying the mucoprotein structure of mucus and allowing for easier expectoration. Coronary Artery Disease Coronary artery disease is primarily due to atherosclerosis. Unchecked, atherosclerosis blocks coronary arteries, which Pharmacological Interventions leads to hypoperfusion distal to the occlusion and death of the during a Cardiac |
Emergency cardiac muscle tissue, acute myocardial infarction (AMI). The series of events that leads up to and includes the myo- Over 60 million Americans have cardiovascular disease and cardial infarction is referred to as coronary artery disease over 12 million Americans have coronary artery disease. (CAD). Over 7 1/2 million of those Americans will have an acute Atherosclerosis, the underlying pathology of coronary myocardial infarction (AMI) and over one million will not artery disease, starts as a streak of fat (cholesterol) on the survive the event. Additionally, nearly fi ve million will have walls of an artery, any artery. This includes the cerebral arter- congestive heart failure.20 ies as well as the coronary arteries. The fat infi ltrates into These fi gures serve to illustrate the prevalence of car- the wall of the artery, below the tunica intima, and forms diovascular disease and its impact upon Americans. In fact, a fatty lesion referred to as plaque. The plaque has a thin cardiovascular disease has been the number one killer in the fi brous covering, created by the tunica intima, called the cap. United States since 1918, with the exception of the year of This bulges into the lumen of the artery, partially obstructing the great infl uenza outbreak. blood fl ow. As the major health issue in the United States for the The presence of nitric oxide (NO), created in endothe- past nine decades, great efforts have been made to reduce the lium of the walls of the blood vessel, which prevents vaso- number of deaths, many of them out-of-hospital, from car- constriction; and heparin sulfate, an anticoagulant released diovascular disease. In fact, the genesis of EMS is owed, in from the endothelium of the walls of the arteries, temporar- part, to cardiovascular disease. Beginning with Dr. Pantridge ily prevents blood clot formation in the narrowed coronary in Belfast, Ireland, whose experiment with using coronary care arteries. Pharmacological Interventions for Cardiopulmonary Emergencies 647 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. As time progresses, macrophages and T-lymphocytes, if the blood vessel had been ruptured, or cut, and attempt to defender cells in the circulation, enter the plaque and begin plug the breach. the process of phagocytosis, literally enveloping the choles- The response to the rupture begins with the attach- terols and fats (lipids) in an effort to destroy the invaders. The ment of von Willebrand’s factor and ADP released from now engorged macrophages swell and become foam cells. inside the plaque to glycoprotien (Gp)IIB/IIIA receptors Foam cells are fi lled with dead and dying muscle cells and found on passing platelets. The now “activated” platelets lipids. Proteins entrapped within the toothpaste-like liquid change from a disc shape to a sphere shape and attach to lipid core also begin to form collagens and von Willebrand’s the exposed collagen and to each other. The eventual mass factor, two elements in clotting. of platelets forms a platelet plug. Platelet plugs are the Plaques, especially newer, less mature plaques, are softer, short-term solution to the problem. have a thinner cap, and are prone to rupture. Any hemody- For a more stable blockade, the platelet plug needs to be namic stress (e.g., a sudden increase in blood pressure) can reinforced. The entire process, from platelet plug production cause a plaque to rupture (Figure 30-4).52–55 to the reinforcement of the thrombus, is called coagulation. When a plaque ruptures and the thin cap is torn, the Coagulation starts when coagulation factors—adenosine uplifted plaque now exposes the collagen in the basement diphosphate (ADP), serotonin, and thromboxane (TxA2)— layer underneath the endothelial lining. Blood clotting fac- are released from the damaged endothelial wall, which trig- tors in the plasma, attracted to the exposed collagen, react as gers a series of events, called the coagulation cascade. Cross sections through a coronary artery undergoing progressive atherosclerosis and arteriosclerosis Small atheroma Normal artery with open Elevated cholesterol Enlarging atheroma lumen and blood fats (plaque deposit) Moderate atherosclerotic Moderate narrowing of lumen myocardial ischemia Angina pectoris Occlusion of left coronary artery A myocardial infarction (“heart attack”) on left side of the heart Complete/almost complete Severe acute occlusion, with hardening myocardial ischemia caused by calcium deposition and infarction Figure 30-4 The development of plaque. Plaque rupture occludes the narrowed lumen causing a myocardial infarction. 648 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. First, a fi brous soluble protein called fi brinogen, which to bile; therefore, increasing bile elimination indirectly helps is found fl oating in the blood, becomes activated. Normally to rid the body of cholesterol. An example of a bile sequester- fi brinogen is coated with amino acids that have an outward ing agent is cholestyramine. facing negative charge. As like-charges repel, these negatively Niacin, a water-soluble vitamin, is also occasionally pre- charged amino acids keep the fi brinogen molecules separated. scribed as a lipid-lowering agent. Niacin inhibits the lipolysis When clotting factors are released, a protein-cutting (division of fats) in adipose tissue, which would liberate free enzyme (protease) called thrombin literally clips off the fatty acids.59–61 These free fatty acids would normally be used negatively charged amino acids. Without the negative charge by the liver to create new triglycerides and then cholesterol. repelling the fi brinogen molecules, the fi brinogen clumps In the case of the patient with hyperlipidemia, the added cho- together, becomes strand-like, and forms fi brin. lesterol would also boost the process of atherosclerosis. What follows are two processes, one intrinsic and the Niacin in high dosages, or in persons sensitive to niacin other extrinsic, which result in a mature clot made of plate- (e.g., diabetic patients and those with liver disease), may also lets cross-linked with fi brin and other blood cells in a fi rm cause an anaphylactoid (anaphylactic-like) reaction, including meshwork called a thrombus. With the thrombus in place, pruritus, diffuse skin fl ushing, as well as dysrhythmias. the lumen of the blood vessel is blocked. The reductase inhibitors, a group of drugs referred to as Decreasing the incidence of cardiovascular disease, and “statins” because of the common ending, have grown increas- subsequent acute coronary syndrome, revolves around inter- ingly popular as a treatment for hyperlipidemia. This class of fering with one or more of the processes previously described. drugs inhibits an enzyme, 3-hydroxy-3-methylglutaryl coen- Starting with chemotherapeutic agents which eliminate the zyme A reductase (HMG-CoA), which is essential for the fatty streak on the inner lumen of the artery that signals the liver to make cholesterol. Without the enzyme HMG-CoA, start of atherosclerosis, cardioprotective agents will be dis- the liver cannot make cholesterol and the process of athero- cussed individually. sclerosis is slowed. Patients with liver disease, particularly alcoholics, are at risk for severe side effects from the statin class of lipid-lowering Antihyperlipidemic Drugs drugs, including rhabdomyolysis (a necrosis of skeletal mus- The easiest means to prevent thrombus-induced coronary cle) which may lead to kidney failure. Examples of reductase artery disease is to reduce unwanted lipids which form inhibitors are fl uvastatin, lovastatin, and atorvastatin. plaques at the onset. Despite dietary control, some individuals continue to have elevated lipid levels in the blood (hyperlipi- Anticoagulants demia), possibly due to genetic infl uences. Hyperlipidemia Unchecked, the process of atherosclerosis will eventually is an abnormally high level of triglycerides and cholesterol culminate in plaque formation, plaque rupture, and thrombus which, when uncontrolled, can lead to atherosclerosis. formation via the coagulation cascade. Anticoagulants are Normally, lipids are bound to protein, forming lipo- intended to prevent the formation of a thrombus, which is the proteins (a protein shell around a lipid core), and are found culmination of the coagulation cascade. fl oating in the blood. There are three varieties of lipopro- Anticoagulants include those agents that prevent plate- teins: very-low density lipoproteins (VLDL), low-density let adhesion, fi brin collection, thrombus formation, and other lipoproteins (LDL), and high-density lipoproteins (HDL). Of thromboembolic events. While anticoagulants are discussed the three types of lipoproteins, LDL is considered the most under the acute coronary syndrome, these drugs are used dangerous because of its high cholesterol content, about 50% under the larger umbrella of conditions caused by thrombus cholesterol by weight.56–58 formation including pulmonary embolism, deep vein throm- Some lipid-lowering agents lower cholesterol, thus elim- bus, and thromboembolic ischemic stroke. inating it for conversion to LDL, by sequestering the choles- One of the earliest anticoagulants was salicylate. Extract terol in the bile. The bile is then excreted into the gallbladder of willow bark, salicylate, had long been known for its anal- and, in turn, into the small intestine. Cholesterol is a precursor gesic qualities as “Oil of Wintergreen” (methyl salicylate). However, until Felix Hoffmann eliminated the painful side effect of stomach irritation by reformulating salicylate, it Street Smart was not widely used. Following the reformulation to acetyl- salicylic acid (ASA), the German pharmaceutical company Bayer™ took out a patent and renamed the drug aspirin. Over On the downside, bile-sequestering agents may 80 billion tablets of aspirin are used annually in the United interfere with the absorption of certain medications, States as a pain reliever and fever reducer.62 Thanks in part such as phenobarbital, digoxin, warfarin, and to Bayer™ Company aspirin television commercials, aspirin tetracycline, resulting in reduced subtherapeutic is also widely known for its ability to prevent heart attacks. A study of 90,000 patients showed that aspirin alone pre- levels of these important drugs. vented the reocclusion of coronary arteries in 23% of patients who had a prior AMI, especially if given within four hours.63 Pharmacological Interventions for Cardiopulmonary Emergencies 649 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. As a class, platelet inhibitors prevent platelet aggregation by preventing a critical enzyme, cyclooxygenase, from creat- Street Smart ing thromboxane A2 (TxA2). TxA2 promotes platelet aggre- gation and vasoconstriction. Without TxA2, platelets remain “slippery” and cannot form the initial platelet plug needed for Some EMS systems routinely draw blood samples for thrombus formation. clotting studies, prothrombin times (PT), and partial Prior to administration of aspirin or an aspirin-like prod- prothrombin times (PTT) for analysis in all patients uct, the provider should inquire if the patient has a history who are on an anticoagulant such as warfarin. of asthma. Aspirin-induced asthma (AIA) is present in about 10% to 15% of the patient population with asthma. AIA is an idiosyncratic type of reaction which presents with allergy- like symptoms and is akin to the reaction seen to CT con- Fibrinolytics trast dyes. Treatment with ASA is acceptable for patients with Fibrinolytics dissolve blood clots, which can cause heart asthma, although the patient must be carefully monitored. attacks (acute myocardial infarction/AMI), brain attacks Symptomatic relief should be immediately available if symp- (stroke/CVA), and pulmonary emboli (PE). If successful, the toms should occur. There are several other platelet inhibitors, artery is re-opened (a process called recanalization) and the such as dipyridamole, for those who absolutely cannot toler- blood fl ow is restored to distal ischemic tissue in the affected ate aspirin side effects. organ. The body also naturally produces anticoagulants, such as The fi rst generation of fi brinolytics included uroki- heparin, in the liver, lungs, and lining of the intestine which nase and streptokinase. Initially used to dissolve blood prevent clotting. Circulating heparin helps prevent spurious clots from |
long-term, indwelling central venous catheters, blood clots from forming in the body by preventing the for- they were eventually used for the treatment of heart attacks mation of fi brinogen from fi brin. and other thromboembolic events. An unfortunate conse- The addition of intravenous heparin to the body is com- quence of the use of these early fi brinolytics was systemic monly used to help prevent new thrombus formation. It is bleeding. Intracerebral hemorrhage, for example, occurred used as a prophylactic measure post-surgery, to prevent deep with enough frequency that criteria for use of these drugs vein thrombus-induced pulmonary embolism, to prevent was tightened in an attempt to limit this sometimes fatal clot formation during blood transfusion, and to prevent clots complication. from forming on the wall of the heart during atrial fi brillation The second generation of “clot-busters” were more spe- (mural thrombi). cifi c to a newly forming thrombus. These new fi brinolytics It is important to note that heparin does not dissolve used the naturally occurring tissue plasminogen activator pre-existing clots and therefore cannot be used as the sole (tPA) to convert plasminogen into plasmin. Plasmin, a fi brin- therapeutic agent during a thromboembolic emergency. olytic enzyme, dissolves fi brin within the platelet plug. The Other fi brinolytic agents, discussed shortly, are used during a net effect is that tPA disassembles the platelet plug. thromboembolic emergency to actually dissolve a blood clot. Administered intravenously, tPA was an effective and Heparin is often used in conjunction with these fi brinolytic rapid treatment for AMI. It was also relatively inexpensive agents to prevent fresh clots from occurring or to prevent the when compared to the costs of interventional cardiology, current clot from enlarging. such as angioplasty or open heart surgery. Most of the heparin used in-hospital is low-molecular weight (LMWH) heparin. LMW heparin has a longer half-life (t1/2) than standard heparin, permitting daily or twice daily administration, by subcutaneous injection, as compared to stan- Cultural / Regional differences dard heparin, which must be continuously infused intravenously. This quality makes it desirable for outpatient use. The term “thrombolytic” was used for almost a An intravenous infusion of unfractionated (standard) heparin is indicated for use in patients with ST-elevated AMI, decade. However, the more medically correct term is in conjunction with aspirin. LMWH shows promise in the “fi brinolytic.” Both are still used interchangeably in treatment of the patient with a ST-elevated AMI, but its use some medical circles and by the lay public. has not been defi nitively supported in the large scale studies. That said, LMWH is well supported by research for unstable AMI, non-ST elevated AMI and angina.64 Administration of fi brinolytics is not without its dangers. Heparin and its oral counterpart, warfarin, can lead to Caution must be observed before administering fi brinolytics bleeding complications. Once anticoagulants have been to patients with a history of cerebrovascular disease, such as administered, the patient must be monitored for signs of active ulcer disease and recent trauma. Some use a checklist occult hemorrhage, such as tachycardia and hypotension. when administering fi brinolytics (Figure 30-5). 650 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. FIBRINOLYTIC CHECKLIST Rev. 5/07 Central Shenandoah EMS Council, 2312 W. Beverley St., Staunton, VA 24401 • 540-886-3676 • www.csems.vaems.org INCIDENT DATA Date Agency Unit # Patient Name Age DOB INDICATIONS FOR USE OF CHECKLIST Patient experiencing chest discomfort for greater than 15 minutes and less than 12 hours, AND… 12-lead ECG shows STEMI or presumably new LBBB. Are there any contraindications to fibrinolysis? Systolic BP greater than 180 mm Hg YES NO Diastolic BP greater than 110 mm Hg YES NO Right vs. left arm systolic BP difference greater than 15 mm Hg YES NO History of structural central nervous system disease YES NO Significant closed head/facial trauma within the previous 3 months YES NO Recent (within 6 weeks) major trauma, surgery (including laser eye surgery), GI/GU bleed YES NO Bleeding or clotting problem or on blood thinners YES NO CPR greater than 10 minutes YES NO Pregnant female YES NO Serious systemic disease (eg, advanced/terminal cancer, severe liver or kidney disease) YES NO Is patient at high risk? Heart rate greater than or equal to 100 bpm AND systolic BP less than 100 mm Hg YES NO Pulmonary edema (rales) YES NO Signs of shock (cool, clammy) YES NO Contraindications to fibrinolytic therapy YES NO Comments Figure 30-5 Fibrinolytic checklist. Pharmacological Interventions for Cardiopulmonary Emergencies 651 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Prehospital fi brinolytics have been shown to improve coronary syndrome is a process which has many stages, from survival in a few studies and should be considered when intermittent angina to cardiac ischemia to acute myocardial transport times exceed 30 to 60 minutes. Studies continue to infarction. investigate which groups of patients would benefi t the most In most cases, the Paramedic’s job is the early recognition of from fi eld fi brinolytics.65 acute coronary syndrome; stabilization of the patient’s hemody- A growing body of evidence indicates that certain subsets namics and any other complications, such as dysrhythmia; and of patients benefi t more from mechanical revascularization the provision of expeditious transfer of the patient to a cardiac (angioplasty) than standard fi brinolytics. Rapid transportation, care center for further treatment. In some cases, Paramedics with appropriate stabilization, to a cardiac care center may are starting the process of treatment of the coronary artery syn- become the standard of care. Consideration should be given to drome in the fi eld through use of fi brinolytics. In every case, incorporate criterion-based triage into EMS protocols for the whether it is the use of prehospital fi brinolytics or expeditious treatment of the suspected AMI.66 transportation following initial stabilization to a cardiac care center, re-establishing blood fl ow to ischemic myocardial tissue Glycoprotein IIB-IIIA Receptor Blockers is a top priority. Use of nitrates can improve myocardial blood Activation of glycoprotein receptors on platelets and the fl ow, reduce pain, and potentially avert sudden cardiac death. formation of fi brin represent the fi nal common pathway in platelet plug formation. Blocking these receptors prevents Nitrates the binding of fi brinogen and thereby prevents platelet aggre- One of the oldest treatments for cardiac-related angina has been gation and plug formation. nitroglycerin. For centuries, amyl nitrate (a volatile organic The intravenous administration of medications called nitrate when in alcohol) had been used to relieve angina. In glycoprotein IIB-IIIA receptor blockers, like tirofi ban and 1867, the Scotsman Lauder Brunton thought the positive effects eptifi batide, is useful in preventing the re-formation of plate- of amyl nitrate were from hypotension. In 1933, Sir Thomas let plugs and arterial re-occlusion immediately following Lewis more correctly postulated that the effect of amyl nitrate fi brinolysis or angioplasty. was due to dilation of the blood vessels.20 The combination of aspirin (ASA), heparin, and a glyco- However, nitrate’s exact mechanism of action was protein IIB-IIIA receptor blocker can reduce the risk of sud- den cardiac death substantially.67 still unknown until recently. Previously, it was known that some substance, labeled endothelial-derived relaxing factor (EDRF), relaxed the smooth muscle in the walls of blood ves- Acute Coronary Syndrome sels, which in turn led to vasodilation. The involvement of Atherosclerotic coronary plaque growth narrows the blood ves- nitrates in this process was largely unsuspected. sel’s lumen. The narrowing, called a stenosis, causes a reduc- In 1998, Furchgott, Ignarro, and Murad were awarded tion in blood fl ow to the portion of the myocardium distal to the the Nobel Prize in medicine for their discovery of the role of stenosis. Decreased distal coronary artery blood fl ow can lead nitric oxide in human physiology. Nitric oxide (NO), a short- to chest pain, or angina pectoris. Unchecked, these plaques lived gas, is released from endothelial cells within the inner rupture and can lead to complete coronary artery occlusion and lining of the blood vessel where it acts as an intercellular an infarction of myocardium distal to the occlusion. chemical messenger, signaling an increase in cGMP within The entire process leading up to and including angina muscle cells. This increase in cGMP, in turn, relaxes the and AMI is called the acute coronary syndrome (ACS). This smooth muscle in the blood vessel, leading to vasodilation. change in perspective, from treating a heart attack as an iso- It is now known that acetylcholine, the chief neurotrans- lated event to one of treating atherosclerosis as a part of the mitter in the parasympathetic nervous system, acts by stimu- continuum in a common process, refl ects a more considered lating the production of nitric oxide and thereby results in approach to coronary care and refl ects the growing knowl- vasodilation through this mechanism. edge about atherosclerosis and coronary artery disease as a In many cases, coronary artery vasodilation can offer result of practice experience (Table 30-1). symptomatic relief from the cardiac patient’s angina by Syndromes are, according to Taber’s Medical Dictionary, increasing the diameter of a chronically narrowed, stenotic “the sum of signs associated with any pathological process.” vessel. Ironically, Alfred Nobel, inventor of nitroglycerin- In this case, the pathological process is atherosclerosis. Acute based dynamite and originator of the Nobel Prizes, suffered from angina and was prescribed nitroglycerin for his pain. So as to not alarm the pharmacist, the physician labeled the Table 30-1 Inclusion Criteria for Acute nitroglycerin “trinitrin” (TNT). Coronary Syndromes Nitrates administered to a patient provide an exogenous • Unstable angina (external) source of NO. Nitrates have their greatest impact • Non ST-segment myocardial infarction on the venous circulation and reduce venous return, or pre- • ST-segment elevation myocardial infarction (STEMI) load, to the heart. Reduced preload into the heart means less work for the heart’s muscles. 652 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. 5 to 15 minutes. Other side effects include transient hypoten- Street Smart sion, bradycardia or tachycardia, or dizziness.72,73 Nitrate pastes provide a more sustained release of the medication over four to six hours. In contrast, newer time- Fresh nitroglycerin has a slightly vinegary smell and a released patches are formulated with nitrates to create a res- very short shelf life, especially when exposed to light ervoir of medication which can last 1 1/2 to 24 hours. or moisture. Conversely, aspirin has a very long shelf Nitroglycerin is also available in an intravenous form life. In a United States Air Force study, it remained that allows precise titration of the level of drug needed in order to obtain relief from chest pain without the risk of potent for four years. When it breaks down into common side effects, such as hypotension. Intravenous acetic acid, it gives off a slight vinegar smell. Using nitroglycerin is administered in micrograms of drug using an the vinegar smell as a test, the potency of drugs intravenous pump, a biomechanical device that carefully con- trols the rate of administration. Intravenous nitroglycerin (even those within the expiration date) can be is r eadily absorbed into plastic; therefore, special polyvinyl verifi ed. Expired or questionable drugs may not be chloride (PVC) administration sets are used with nitroglyc- potent and should not be used. erin infusion. Nitrate Tolerance Nitrates’ |
secondary vasoactive effect, particularly at Nitrates, an essential ingredient in smokeless gunpowder, higher doses, is arterial dilation. Arterial vasodilation creates have long been used in munitions production. Workers at the reduced peripheral vascular resistance (PVR), or afterload. munitions factory in places like Springfi eld, Massachusetts, Afterload can be thought of as the resistance which the heart often experienced a headache when returning to work after pump must overcome in order to achieve forward blood fl ow. the weekend. Workers learned that if they took a bag of It is grossly measured as the diastolic blood pressure. nitrate-laced gunpowder home and rubbed it on their hands There is some debate whether nitrates create a coronary they would not experience a headache when returning to work artery-specifi c vasodilation. Coronary vasodilation would after the weekend. increase blood fl ow to oxygen-starved myocardium and What these workers had developed was a classic example lessen the angina.68,69 What is not disputed is nitrates’ ability of tolerance to a drug, in this case nitrate. After continuous to reduce preload and lessen afterload, which culminates in a exposure they developed a resistance to its effects and/or its total reduced workload for the heart. This effect may have the side effects, such as a headache. Whenever these workers greatest impact on relieving the angina.70,71 went home for the weekend, they essentially went on a “drug holiday,” a period without the drug. They then lost their toler- ance to the drug. By continuing their exposure to the nitrate- Street Smart laced gunpowder during the weekend, they ensured that their tolerance for nitrates continued. Patients who are prescribed All patients receiving cardiac medications, nitrates regularly can also develop a tolerance to nitrates and will not respond as well to routine doses of nitrates in the fi eld. particularly vasoactive drugs such as nitrates, need In some cases, it may be advisable to consider an alternative to have constant hemodynamic monitoring, blood therapeutic approach, such as the use of morphine sulfate. pressure, and pulse before and after medication Indications for Nitrate Use administration. The chief use of nitrates is for the relief of cardiac-related chest pain called angina pectoris, or simply angina. Angina is brought Regardless of the primary mechanism, decreased work- about by a mismatch between the work required of the heart load, or coronary artery vasodilation, nitrates have become (workload) and the heart’s ability to do that work. This limita- standard therapy for the patient with angina. In either tablet tion is a function of the coronary blood fl ow to the heart. or spray form, sublingual nitrates have an onset of action of Nitrates are also used to treat pre-infarction angina, for- less than one minute and peak in the bloodstream within two merly known as unstable angina, in an effort to prevent some minutes. With a half-life of only fi ve to seven minutes, any of the damage of coronary artery occlusion. By increasing hypotensive effects created by the venous dilation will sub- collateral blood fl ow to the affected area, distal to the obstruc- side quickly and usually are treated conservatively, at least tion, as well as decreasing the heart’s overall work, the dam- initially, by placing the patient supine for a few minutes. age can potentially be lessened. Nitroglycerin loses its potency when exposed to light, Frequently, physicians and Paramedics assumed that if heat, and moisture. Therefore, it is usually carried in a sealed nitroglycerin relieved the chest pain, then the chest pain must glass bottle with cotton wadding. A commonly noted side be suspected of being cardiac in origin and the likely diagno- effect of nitroglycerin is a transient headache for between sis was coronary artery disease (CAD). Pharmacological Interventions for Cardiopulmonary Emergencies 653 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. A study at Johns Hopkins showed that of 459 patients levels. Life-threatening hypotension then ensues (cardiogenic treated with nitroglycerin for chest pain, all of whom had relief, shock or forward failure). only 30% had coronary artery disease (CAD). The results of this study should cause Paramedics to pause and consider Precautions other potential etiologies of chest pain whenever nitroglycerin Hypotension-induced syncope, or near-syncope, is a com- is effective in relieving chest pain. This is particularly impor- mon complication of nitrate administration.75,76 The impact tant in light of the fact that one in fi ve patients coming to the of the abrupt loss of preload secondary to venous dilation is emergency department complains of chest pain.74 transmitted downstream, the fallout being loss of blood pres- Nitrates have also proven themselves to be markedly sure and possible loss of consciousness (syncope). effective in the treatment of acute pulmonary edema associ- Fortunately, nitrates have a short half-life. Therefore, the ated with congestive heart failure (CHF). CHF is the result hypotensive effects are short-lived. Laying the patient supine of the heart’s inability to pump strongly enough to completely with feet elevated, and exhibiting some patience, are usually overcome peripheral vascular resistance (PVR) and meet the only treatments needed. If the patient’s blood pressure the body’s needs for oxygen and nutrients. Subsequently, does not return within fi ve minutes, then a volume-sensitive backpressure from the left ventricle, or backward failure, is pathology (e.g., internal bleeding or right ventricular myocar- transmitted through the pulmonary circulation, creating pul- dial infarction) should be considered. monary edema in the process, and eventually extending into the right ventricle. The right ventricle, being a weaker pump Dysrhythmia than the left, is overwhelmed by the combination of venous preload and left ventricular backpressure and fails as well. Despite remarkable advances in medicine’s understanding Nitrates are starting to gain increased favor for the emer- of cardiac pathophysiology, and particularly coronary artery gency treatment of pulmonary edema. While loop diuretics disease, over 500,000 Americans will die from heart disease are immediately effective in reducing pulmonary edema, they each year.77 Over 60% of these deaths will be secondary to a can create a hormonal rebound when the kidneys sense the fatal dysrhythmia called ventricular fi brillation. volume depletion and respond naturally to create further fl uid Ventricular fi brillation is one of many dysrhythmias, an retention. The patient with cardiogenic pulmonary edema abnormality of the electrical activity in the heart. Ventricular may not be volume overloaded, but more correctly, volume fi brillation is a life-threatening problem because there is no unbalanced. Nitrates provide the heart with a respite while it cardiac output. regains control of hemodynamics. Street Smart Contraindications In general, any volume-sensitive condition can be worsened Not all dysrhythmias are dangerous. A study of 1,302 by the use of nitrates. Nitrates temporarily remove a volume professional NFL football players completed by of blood from the central circulation by sequestering it in the venous pool. Volume-sensitive conditions can be divided Dr. Choo and Dr. Hutter, Jr., of Massachusetts into cardiac and extra-cardiac pathologies. An example of an General Hospital demonstrated that 55% had an extra-cardiac pathology that is volume sensitive is cardiac abnormality of the electrical activity in the heart. tamponade. However, after extensive testing, it was decided that The heart is dependent on adequate fi lling pressures (pre- the hearts of these athletes were healthy.78 load) obtained from the venous circulation in order to over- come the compressive consequence of pericardial tamponade. Nitrates decrease preload, via venous dilation, and the cardiac output can drop precipitously. Nitrate administration to a patient The most common persistent dysrhythmia may be with a tension pneumothorax can have the same consequence as atrial fi brillation, which affects over two million Americans. a result of a similar mechanism. Atrial fi brillation, a dysrhythmia more often seen in the The right ventricle is acutely sensitive to changes in fi lling elderly, is associated with an increased risk of brain attack volumes (preload). An acute inferior wall myocardial infarction (stroke) and associated quality of life issues. The incidence which extends into the right ventricle can cause the right ven- of atrial fi brillation is expected to rise as the mean age of tricle to lose its ability to pump a given volume of blood. That Americans continues to climb (referred to as the “graying” volume of blood serves as the “prime” for the left ventricle; any of America). pump that loses its prime loses output and fails. The adminis- tration of nitrates decreases the left ventricular fi lling pressures Therapeutic Goal (prime) by reducing preload into the right ventricle from the The therapeutic goal of antidysrhythmics, drugs which venous circulation. Without adequate fi lling pressures, the car- prevent or abolish dysrhythmias, is to alleviate the symp- diac output from the left ventricle can fall to dangerously low toms associated with an irregular heartbeat and, in some 654 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. resting membrane potential of a cardiac cell, measurable at Cultural / Regional differences approximately /()90 millivolts, is created by the rela- tively negative charge inside the cell as opposed to the posi- tive charges outside the cell. In this resting state, the cell wall Technically, an arrhythmia would be defi ned as the is impenetrable to charged ions such as sodium, potassium, absence of a rhythm (a without rhythm pattern) such and calcium. as occurs in asystole. A dysrhythmia would be an A stimulus called an action potential, such as one pro- abnormal pattern of electrical discharges. However, duced by the normal pacemaker activity of the sinoatrial (SA) node, can change the resting membrane potential. it is common practice to use the terms It raises the resting membrane potential above a specifi c interchangeably. threshold. A cascade of ionic changes at the cell wall, called depolarization, occurs as electrolytes transfer across the cell in an attempt to balance (neutralize) the charge. cases, to help ensure the patient’s survival. However, the The cascade of events in depolarization can be divided mechanisms of action of many of the drugs in this class are into fi ve distinct segments, each segment characterized by a also dysrhythmia producing or pro-dysrhythmic. different ionic event and numbered 0 to 4. These different The results of the Cardiac Arrhythmia Suppression Trial segments represent the changes in the electrical charges from (CAST) appear to indicate that there may be a signifi cant within and outside of the cell (Figure 30-6). For simplicity, increase in mortality associated with use of certain antidys- the depolarization of ventricular myocardial cells is being rhythmic drugs. Therefore, the decision to administer an described, although all cardiac tissues—nervous as well as antidysrhythmic must be carefully considered in terms of muscle—respond in a similar fashion. However, nerve cells risk versus benefi t (CAST).The notable side effects of some are more “excitable” (i.e., able to sustain a larger membrane of the dysrhythmia drugs, in addition to the creation of new resting potential). dysrhythmia, have encouraged the development of alternative After the action potential overcomes the resistance cre- therapeutic approaches. ated by the resting potential of the cell membrane (thresh- Some of the devices and techniques in use are radio- old), the sodium channels in the cell wall membrane open frequency ablation to disrupt alternative conductive wide, allowing an infl ux of sodium into the cell. This infl ux pathways, particularly those of supraventricular origin; of sodium, via the fast sodium channels, corresponds with automated implantable cardioverter defi brillators (AICD) phase zero (0) of the action potential and completely depo- with an ability to terminate ventricular tachycardia and ven- larizes the membrane; an event which can be recorded on a tricular fi brillation; and a new generation of dual-chamber surface electrocardiogram or ECG. sensing electronic pacemakers. Use |
of these devices and With the now abundant sodium (Na) inside the cell, as techniques have brought about a decrease in the prophy- well as native intracellular potassium (K), the cell becomes lactic use of antidysrhythmic medications.79 positively charged. These ionic shifts within the cell will sur- Nevertheless, antidysrhythmic drugs are still used, par- pass neutrality and the cell wall will become slightly posi- ticularly in the setting of sudden cardiac death (SCD), and tive. This ionic overshoot, about ()20 millivolts, represents will probably continue to be used in the foreseeable future phase 1. to prevent dysrhythmic death and abate symptoms associated To this point, at the end of phase 1, myocardial cells have with dysrhythmia. acted in the same manner as skeletal muscle cells. The difference between skeletal muscle and cardiac muscle occurs in phases 2 Review of Action Potential and 3. In phases 2 and 3, the depolarization of myocardial cells Pivotal to an understanding of the actions of most antidysrhyth- is sustained for about 200 to 300 milliseconds during a “pla- mic drugs is an understanding of the action potential of the teau” phase, unlike the more rapid “spike” of skeletal muscle heart’s muscle cells (the myocardial cells, known collectively as myocardium), which these drugs affect. Myocardial cells are essentially “charged” in a fashion + K+ K+ K K+ K+ Na+ Na+ similar to any conventional car battery. Ionic differences, + K+ K+ K+ K+ K Na+ K+ K+ K+ Na+ Na+ Na+ Na+ K+ Na+ two opposing polarities, between the inside of the cell, repre- Higher Na+ Na+ Na+ K+ + + K+ K+ K+ Na+ K+ senting one pole, and the outside of the cell, representing the K+ K Na Na+ K+ K+ K+ K+ K+ K+ K+ Na+ Na+ Na+ Na+ K+ other pole, are the result of a difference in electron numbers. Na+ Na+ K+ Na+ K+ K+ Na+ K+ Na+ K+ Na+ Na+ K+ Typically this difference would be negated as the additional Na+ electrons are exchanged (neutralized). The cells’ ability to K+ Na+ Na+ Na+ K+ Na+ K+ Na+ K+ K+ Na+ prevent this exchange across the cell membrane is called the Na+ Na+ K+ Na+ K+ higher Na+ Na+ Na+ K+ K+ Na+ Na+ Na+ Na+ Na+ K+ K+ K+ resting membrane potential (RMP). Na+ Na+ Na+ K+ K+ K+ Na+ The greater the electrical difference between poles, or across the membrane in this case, the greater the charge. The Figure 30-6 Action potential of cells. Pharmacological Interventions for Cardiopulmonary Emergencies 655 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. depolarization. This permits a longer sustained contraction. The or ectopic pacemaker. This mechanism, the creation of an key to this sustained contraction is calcium. ectopic pacemaker, is thought to be responsible for sudden In an effort to attain neutrality, calcium fl ows into the cardiac death secondary to ventricular fi brillation. cell, via slow calcium channels, and potassium fl ows out. This is the start of the mechanical activation of the myocardium. Ideal Antidysrhythmic Drug Calcium now binds to the troponin complex, which is found As ectopic pacemakers have been implicated in ventricular within the myocardial fi ber. This normally inhibits the bind- fi brillation, the ideal antidysrhythmic drug would preferen- ing of intertwined actin and myosin strands within the mus- tially select ectopic pacemakers (rapidly depolarizing cells) cle fi ber, and thus permits the sliding (contraction) of muscle over normally functioning myocardial cells and suppress fi bers. The amount of calcium present partly determines the their activity. duration, and therefore the strength, of contraction. The dura- Many of the antidysrhythmic drugs display this ectopic- tion of contraction is represented by the length of the plateau specifi c quality. To explain this phenomenon, Hodgkin and in phase 2. Huxley offered the Modulated Receptor Theory (MRT). MRT The myosin f ilaments, now coupled with the actin suggests that ionic channels are in one of three states: resting, f ilaments, contain quantities of an enzyme called active, or inactive. In the polarized state (phase zero), the ionic ATPase. ATPase, in the presence of magnesium, divides channels (particularly the sodium channels) are resting and the intercellular ATP, by hydrolysis, and releases the nonconducting. When the action potential depolarizes the cell, energy-rich substrate phosphate needed to sustain the then (in sequence) fi rst the sodium (Na), then the potassium contraction. Potassium within the myocardial cell now (K), and then the calcium (Ca) channels open and there- starts a rapid exodus from the cell in an attempt to fore are active.80-82 Once opened, these ionic channels become regain the original resting potential but is unable to do inactive until repolarization occurs and the channel is returned so. Phase 3 thus ends. to a resting state. The recovery of the myocardial cell (repolarization) Antidysrhythmic drugs have their effect during the transi- occurs in phase 4. During phase 4, the sodium-potassium tions between these states of resting: open/active and inactive. pump returns sodium and potassium ions to their original The drugs which act upon the ionic channels during the open/ position, juxtaposed across the cell membrane from each active state will preferentially be attracted to rapidly depolar- other. The cell is again in a state of charged readiness, with a izing ectopic pacemakers. These antidysrhythmic drugs can resting action potential of () 90 millivolts. The cell is now be said to be use- (rate) dependent drugs. Examples of use- ready for another cycle of depolarization–repolarization and dependent drugs include quinidine and procainamide. subsequent myocardial contraction. Drugs that affect the ionic channels in myocardial cells Origins of Dysrhythmia in the inactive state would have an affi nity to slower depo- larizing tissues and would demonstrate a reverse use- (rate) Normally, a clump of tissue in a small region near the open- dependent quality. Reverse use-dependent drugs prolong the ing where the vena cava enters the right atrium, called the repolarization of normal myocardial tissues, as electrographi- sinus-atrial (SA) node, spontaneously depolarizes and thus cally demonstrated by a prolonged QT interval. This slow- initiates the wave of depolarization across the heart. As the ing of repolarization can lead to repolarization disturbances, SA node typically depolarizes earlier than any other tissues, such as Torsades de Pointes (twisting of the points), a form it assumes dominance over the process of depolarization of of polymorphic ventricular tachycardia that can deteriorate the entire myocardium. rapidly into ventricular fi brillation. Spontaneous electrical activity in the SA node results from a loss of resting potential (ionic decay) in the cell wall membrane during diastole. When the ionic decay reaches a threshold, then the cell will spontaneously depolarize. This Street Smart quality, which is exclusive to cardiac cells, is called automa- ticity. However, this automaticity is not solely restricted to the tissues in the SA node. In the past, antidysrhythmic drugs, such as lidocaine, If other myocardial tissues reach the same point of were chosen based upon the provider’s past decay more quickly, and become excitable earlier, then they experience or empiric evidence. Recent research will spontaneously discharge (i.e., self-d epolarization) before the SA node. Typically, pacemaker cells such has cast doubt on the effi cacy of some of these as the ones found in the SA node decay quicker than drugs. Providers are now more likely to choose an other cardiac cells and thus take dominance over the antidysrhythmic drug based on research (an cycle. However, abnormal events at the cellular level (e.g., hypoxia, ischemia, or potassium imbalances) may evidence-based approach) rather than simply upon cause a spontaneous depolarization from an isolated portion past experience. of myocardium, called a focus, which becomes an atypical 656 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Vaughn-Williams Antidysrhythmic Class I Drugs Drug Classifi cations All Vaughn-Williams Class I drugs block the sodium chan- nels in the cell wall membrane, which normally open in All antidysrhythmic drugs affect the action potential of the phase zero. By blocking the sodium channels, Class I drugs myocardial cell by altering ionic infl ux of sodium (Na), decrease the speed of the depolarization (i.e., the conduction potassium (K), and calcium (Ca) into the cell during velocity through the myocardium). In this manner, Class I the depolarization/repolarization cycle (Figure 30-7). drugs decrease chronotropy during the upstroke portion of Using the schema of electrolyte changes along the myo- the action potential of phase zero. cardial cell wall as a foundation for understanding cardiac This therapeutic approach is effective for treating tachy- tissue function, all antidysrhythmic drugs can be divided arrhythmias, particularly those that occur because of reentry according to their effect on a specifi c ion channel in the myo- phenomena. Reentry phenomenon, an error of conduction, is cardial cell membrane. Drugs so grouped can be recognized a common cause of arrhythmia and is the result of impaired for their similar therapeutic effect, even if they have slightly conduction in a portion of the cardiac conduction pathway. different actions. The Vaughn-Williams classifi cation uses Specifi c supraventricular rhythms and ventricular tachycar- this approach, categorizing drugs according to similar elec- dias utilize a reentry pathway mechanism, which creates a trophysiologic actions. circus movement of rapid depolarization and repolarization While the Vaughn-Williams classifi cation system is use- around a block. The result is a tachyarrhythmia. ful in helping to predict a drug’s action, it is not perfect.83 Class I drugs bind to sodium channels which open more Many drugs have effects which cross over to other classes. frequently. This property of Class I drugs, called use- (rate) For example, amiodarone is predominantly a potassium chan- dependence, means that Class I drugs will create a total nel blocker, and thus is grouped with class III drugs. However, blockade at the site of the conduction defect and effectively it also has some other actions which are found in all four terminate the circus movement. Vaughn-Williams classes (Table 30-2). On the downside, the slowed conduction caused by Class I The common characteristic of all antidysrhythmic drugs drugs negatively affects the myocardium’s contractility or is their ability to suppress the excitability (automaticity) of V . (V is a measure of the myocardium’s contractility.) max max the myocardial cell. Suppression of aberrant automaticity, the A loss of contractility directly translates to a loss of force principal source of ectopic pacemakers, results in the elimi- of contraction, or inotropy. Negative inotropy can cause loss nation of the dysrhythmia. Elimination of dysrhythmia may of cardiac output and create hypotension or aggravate heart prevent sudden cardiac death as well as some of the symp- failure. toms associated with dysrhythmia. As a result of slowed conduction velocity, the QRS of the ECG, which is representative of ventricular depolarization, is widened and the QT interval, which represents the total time Street Smart of depolarization to repolarization, is prolonged. Patients with a prolonged QT interval, either as an inborn error of conduction or as a drug-induced complication, who Vaughn-Williams classifi cations (I, II, III, IV) should are given Class I drugs are prone to life-threatening mono- not be confused with the American Heart morphic ventricular tachycardia.84 This is particularly true if Association’s classifi cations (I, IIa, IIb, III) of the the patient also has poor left ventricular function (ejection fraction < 40%) secondary to previous AMI. drug’s effectiveness. Class I drugs are even further divided into Class A, Class B, and Class C according to their similar electrophysiologic effects on the duration of the action potential. Class IA drugs Sodium Sodium Potassium slow phase zero depolarization. Class IB drugs have a lesser channels open channels close channels open effect on |
phase zero depolarization, but shorten the repolar- ization time in phase 3. Class IC drugs slowly bind to the Potassium sodium channels, and thus greatly depress the rate of rise in channels close +30 mV the action potential in phase zero. 0 mV Class IA One of the earliest antidysrhythmic drugs was quinidine, a Class -70 mV IA antidysrhythmic. Quinidine attaches to sodium channels as soon as they open during phase zero. Quinidine also creates a Time (ms) 1 ms potassium channel blockade, which increases the duration of the action potential, and in effect, leaves sodium channels open Figure 30-7 Cell depolarization. longer so that more drug can bind with the sodium channels. Pharmacological Interventions for Cardiopulmonary Emergencies 657 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Table 30-2 Actions of Antidysrhythmic Drugs per Vaughn-Williams Classifi cation Effect Effect on V-W Mechanism on Ionic Action Use- Pro- Inotropic Class of Action Channels Potential Examples Dependence Dysrhythmia* dysrhythmia Effect IA Sodium Prolongs Slows Quinidine Reverse use- Atrial fi brillation Torsades Negative channel open/active phase zero Procainamide dependence Ventricular de pointes inotropic effect blocker state depolarization– dysrhythmia Infranodal prolonging block depolarization IB Sodium Prolongs Slows Lidocaine Use- Ventricular Infranodal Negative channel open/active phase zero Phenytoin dependence dysrhythmia block inotropic effect blocker state depolarization Shortens Shortens inactive state phase 3 repolarization – effectively shortening repolarization IC Sodium Prolongs Greatly slows Encainide Use- AV nodal Torsades de channel open/active phase zero dependence re-entry pointes blocker state depolarization WPW-related – little effect on repolarization II Beta-receptor Prolongs Supresses Propanolol Reverse use- Atrial fi brillation AV block Depress left blocker open/active phase 4 Metoprolol dependence WPW ventricular ventricle Calcium state depolarization dysrhythmia function channel blocker III Potassium Prolongs Prolongs Amiodarone Reverse use- Atrial fi brillation Torsades channel inactive state phase 3 Breytlium dependence Ventricular de pointes blocker repolarization dysrhythmia IV Calcium Shortens Shortens Diltiazem Use- AV nodal AV block Negative channel open/active entire action Verapamil dependence re-entry intropic effect blocker and inactive potential Atrial fi brillation states Quinidine may be most noted for its ability to create pro- found hypotension. Dubbed the “Quinidine effect,” Class IA Street Smart drugs all tend to lower blood pressure through massive vasodi- latation created by an alpha-sympathetic blockade. Other Class The effects of Class I drugs on nervous tissues makes IA drugs include procainamide and disopyramide, which both have similar drug effects to a lesser or greater degree. them useful as local anesthetics. Lidocaine and Procainamide saw a great deal of use in the out-of-hospital procaine (the source of procainamide) alter nerve setting for the treatment of ventricular dysrhythmias in the conduction and thus change the patient’s pain 1970s and 1980s. However, it has fallen out of favor as more effective drugs, with fewer side effects, have since become perception. available. Class IB Lidocaine has been extensively used for the treatment Lidocaine is the prototypical drug for Class IB agents. Lidocaine of ischemia-induced ectopy. During periods of ischemia, inhibits fast sodium channels, like Class IA drugs, but does not the speed of ionic exchange in the myocardial tissues is block the potassium channels. The result is a shorter repolariza- impaired. The result is a longer action potential and occa- tion time. Without a prolonged depolarization–repolarization sional spontaneous depolarizations, called after-potentials, cycle, represented by a prolonged QT interval, there is less which can create ventricular ectopy and induce ventricular opportunity for torsades de pointes to occur. fi brillation. 658 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Class IB drugs, such as lidocaine, preferentially block the nervous system in the heart, which could have triggered ear- sodium channels of ischemic tissues, preventing spontaneous lier ectopic beats. depolarizations. Lidocaine has seen a great deal of use in the Administration of Class II agents, such as propra- treatment of ventricular fi brillation during cardiac arrest. nolol, blocks the beta receptors in a lock-and-key fash- 1 Lidocaine is almost immediately metabolized by the liver, ion, decreasing intracellular cAMP, and thereby prevents via fi rst pass biotransformation, and therefore must be continu- unwanted tachycardia. The prevention of tachycardia and ously infused intravenously. Understandably, patients with liver unwanted ectopic beats can be life-saving. dysfunction, such as the elderly, are at greater risk for toxicity. Class II agents can be used to treat hypertension, to prevent angina, as a cardioprotective agent, and to decrease Class IC mortality associated with acute coronary syndrome. Thus, Class IC agents block sodium channels, as do the other Class beta-blockers are a useful drug for the treatment of patients I agents. Class IC drugs also have the added effect of slowing with risk factors for sudden cardiac death. conduction in all cardiac tissues, including the Purkinje fi bers. Use of Class IC drugs, particularly fl ecainide, presents Pharmaceutical Properties a therapeutic quandary. On the one side, Class IC drugs are The fi rst generation of beta-blockers were relatively nonselec- very effective in the treatment of refractory ventricular dys- tive (i.e., blocking both the beta receptors, which dominate 1 rhythmia. On the other side are the results of the Cardiac the heart, as well as the beta receptors, which dominate the 2 Arrhythmia Suppression Trial, which showed a two-fold lungs). Blocking beta receptors can result in bronchoconstric- 2 increase in mortality for patients on the drug.85 Class IC tion. Therefore, use of these drugs required extreme caution in agents are now prescribed for very limited circumstances to patients with asthma or similar reactive airway diseases. patients without a history of myocardial infarction where the The next generation of beta-blockers are more cardiose- benefi ts are thought to outweigh the risk. lective, meaning they primarily affect the heart and have a lesser impact on the lungs. Thus, they are safer to use. The Class II Drugs newest, third generation of beta-blockers have additional vasodilatory properties which can be helpful in reducing the Class II agents block the sympathetic nervous system’s stim- work of the heart. ulation of beta receptors in the heart. At fi rst glance, inclu- sion of beta-blockers in the Vaughn-Williams schema would Antihypertensive Properties appear inconsistent with the other classes of antidysrhythmic drugs. Other antidysrhythmic drugs in the Vaughn-Williams Beta-blockers exert a powerful antihypertensive effect by classifi cation depend on blocking electrolyte channels in the blocking the alpha-adrenergic receptors in the peripheral cell wall membrane. Beta-blockers also block electrolyte blood vessels, leading to vasodilation and a reduction in channels. Beta-blockers work indirectly on electrolyte chan- peripheral vascular resistance. This is measured crudely by nels in the cell wall membrane by inhibiting the chemical the diastolic blood pressure. messenger, which opens calcium channels. The heart has abundant beta receptors; about 85% of the 1 sympathetic receptors within the heart are of the beta type. Street Smart 1 The direct effect of stimulating a beta adrenergic receptor is 1 to cause a series of messenger proteins, such as cyclic AMP, Sudden withdrawal from beta-blocker medication, to stimulate calcium channel opening. Increased calcium in a consequence of unpleasant side effects in many the myocardium increases the strength of contraction (a posi- tive inotropic effect) and thereby improves cardiac output. cases, can lead to rebound hypertension. Unchecked, Open calcium channels also have a number of other asso- the hypertension can increase to the level of a ciated electrophysiologic effects. These include increased hypertensive crisis during which damage to the eyes, automaticity of the SA node with accelerated conduction brain, heart, and kidneys can occur. through the AV node, resulting in the customary tachycardia which accompanies administration of adrenergic agonists. An increase in spontaneous depolarization of ischemic tissue can be seen as well. Antidysrhythmic Properties A blockade of the beta-adrenergic receptors in the myo- Beta-blockers are effective antidysrhythmic agents. These cardium prevents calcium channels from opening by decreas- medications are most effective for dysrhythmias caused ing the level of cellular cAMP available to open the calcium by errors of automaticity (i.e., abnormal automaticity) or channels.86–88 With fewer calcium channels open, the result errors of conduction (e.g., Wolff-Parkinson-White syndrome is an inhibition of spontaneous depolarization during phase (WPW) or Lown-Ganong-Levine (LGL)). Untreated, these 4. In short, beta-blockers prevent fi ring of ectopic myocar- errors in rhythm can lead to hypotension, syncope, and sud- dial cells by blocking the beta receptors of the sympathetic 1 den cardiac death. Pharmacological Interventions for Cardiopulmonary Emergencies 659 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Beta-blockers indirectly preclude the myocardium from Normal creating errors of impulse generation by preventing sympa- thetically induced tachycardia. These tachycardias can create a mismatch between the work of the heart and the coronary arteries’ ability to supply oxygen-rich blood to the myocar- dium so the heart can do its work. This mismatch can result in myocardial cell hypoxia, which in turn leads to abnormal depolarization and the formation of ectopic pacemakers. Extra-cardiac causes of excessive tachycardia include pheochromocytoma, an epinephrine-excreting adrenal tumor, and a thyroid storm (thyrotoxicosis), to name just a few. Regardless of the etiology, beta-blockers prevent tachycardia, which can lead to ventricular irritability. Beta-blockers can also effectively treat errors of impulse conduction. Errors of impulse conduction are created by either a unidirectional block in the conduction pathway or the presence of an additional accessory pathway (seen in WPW). These errors in conduction create an abnormal conduction mechanism called reentry phenomenon. Under normal conditions, the impulse from the SA node Accessory pathway creates an action potential that fl ows down the conduction system to the base of the bundle branches where the conduc- tion bifurcates into two branches. It is then transmitted across the ventricular myocardium in a wave. If a segment of the pathway experiences hypoxia and ischemia, or has already been depolarized by an accessory pathway which electrically connects the atrium and the ven- tricle, then the cells will be unresponsive to stimulation, in effect creating a block. However, when the depolarization wave comes back around to the block from the opposite direction, it can pass this time, in effect making the block unidirectional. Both normal conduction and abnormal con- duction are created by ischemia and an accessory pathway (Figure 30-8). The myocardial cells beyond the block now have had time to recover and can be depolarized, albeit in retrograde fashion. Since the conduction path is now altered, the action potential will continue to depolarize tissue by following a Figure 30-8 Normal conduction and abnormal reverse pathway. The consequence can be either localized conduction created an accessory pathway. depolarization and the creation of an ectopic pacemaker, or creation of a circular conduction depolarization (called a cir- cus movement) that can lead to ventricular tachycardia and This impressive list of cardioprotective effects is owed in supraventricular tachycardia. large part to the negative chronotropic effect of beta-blockers. The impact of beta-blockers on this type of dysrhythmia By decreasing heart rate (negative chronotropy), beta- is to slow conduction so that the SA node can retake domi- blockers create increased diastolic time. The diastolic time nance. Beta-blockers do not affect either oxygenation of the is that period in the cardiac cycle when the coronary arter- heart or block accessory pathways such as the one seen in ies fi ll. Increased coronary artery fi lling directly translates to WPW. improved myocardial perfusion. As an added bonus, beta-blockers also dilate |
the periph- eral blood vessels, creating a reduction in the resistance Acute Myocardial Infarction against which the heart must pump (afterload) and the total Early administration of beta-blockers during an acute myo- work of the heart. cardial infarction can reduce the size of infarction, decrease Early administration of beta-blockers, within the fi rst the risk of re-infarction, prevent cardiac rupture, preclude four hours of onset of the suspected myocardial infarction, episodes of ventricular tachycardia and supraventricular holds the greatest promise for decreasing mortality (accord- tachycardia, and prevent sudden cardiac death.89–93 ing to one study, a decrease by 15% in the fi rst week).63 660 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. When administered within the fi rst four hours, infarc- Table 30-3 American Heart Association and tion size can be reduced by as much as 30% and the risk of American College of Cardiology Guidelines for the re-infarction of reperfused myocardium strikingly reduced. Management of Patients with Acute Myocardial Those patients who received beta-blockers within the fi rst Infarction—Use of Beta-Blockers two hours of symptom onset had a 61% reduction in six- week mortality in another study.94 Class 1 These fi ndings lend support to the concept that beta- 1. Acute myocardial infarction blockers should be administered as early as possible. a. Within 12 hours of onset of infarction Some Paramedics routinely administer beta-blockers when b. Without contraindication to beta-blocker therapy for example confronted with a patient who is suspected of having an i. Active heart failure acute myocardial infarction as evidenced by history and ii. Asthma/COPD 12-lead ECG. iii. bradycardia c. Non ST-segment elevation (Confi rmed by enzyme tests) Electrical Storm 2. Recurrent chest pain Patients with a recent myocardial infarction can be prone a. Unstable angina to multiple recurrent episodes of ventricular fi brillation 3. Tachyarrhythmia (V. Fib.) called an electrical storm. Treating patients with a. Atrial fi brillation with a rapid ventricular response electrical storm conventionally (with standard Advanced Cardiac Life Support [ACLS]) has produced uniformly poor outcomes. A trial of patients with electrical storm, for whom beta- Contraindications blockers were used after successful conversion of ventricu- Beta-blockers should be administered cautiously in patients lar fi brillation, has shown promise. A remarkable increase in who are diabetics prone to hypoglycemia, have unstable survival in the study group was shown (5% with traditional asthma, or have chronic obstructive pulmonary disease, for ACLS versus 67% with a beta-blocker).95 the reasons that were previously described. Beta-blockers have to be administered cautiously, if at Heart Failure all, in cases of cocaine-induced tachycardia, with or without Traditionally, healthcare providers avoided the use of beta- chest pain.97–99 Cocaine prevents the re-uptake of the neu- blockers in the treatment of heart failure patients, fearing that rotransmitter epinephrine, creating an overload of epineph- the hypotension sometimes created by beta-blockers would rine in the synaptic junction. By blocking the beta-adrenergic aggravate the already failing heart. receptors only, cocaine’s effect on alpha-adrenergic receptors In a recent international study which enrolled over is unimpeded and profound hypertension from peripheral 4,000 patients, beta-blockers have shown new promise in vasoconstriction can occur. treating chronic heart failure. Patients with heart failure sub- Toxicity sequent to acute myocardial infarction who are treated with carefully titrated beta-blockers evidence a slower progression Beta-blocker toxicity can be absolute, as in the case of an in heart failure and an overall 35% decrease in mortality.96 overdose, or relative, as in the case of a patient with a pre- However, beta-blockers are still considered potentially existing heart block that results in a worsening of the heart harmful (Class III) in acute pulmonary edema and should not block. The immediate impact of beta-blocker toxicity is a be used in the fi eld unless under direct orders of a medical profound bradycardia with all of its attendant complications. control physician.77 In many cases, the administration of atropine, a parasympa- thetic blocker, is effective in restoring a tolerable heart rate. In cases where atropine is ineffective, such as in a ven- Therapeutic Keystone tricular bradycardia secondary to complete heart block, then The benefi ts of decreased heart rate and blood pressure transcutaneous external pacing may be used. To mitigate the (which in turn decreases myocardial oxygen demand) and the discomfort created by external pacing, many providers pre- advantage of enhanced coronary artery blood fl ow produced medicate the patient with an analgesic. by a beta-blockade combine to improve myocardial perfusion Frequently, hypotension is a complication of bradycar- and decrease associated mortality and morbidity. dia. Added hypotension created by analgesics would only For these reasons, the American Heart Association and compound the situation. In those cases, glucagon may be the American College of Cardiology have made administra- administered. Glucagon bypasses the beta-adrenergic recep- tion of beta-blockers in acute myocardial infarction a Class I tors and stimulates the formation of cyclic AMP (cAMP) intervention, which is defi ned as conditions for which there is directly. This in turn increases the intercellular calcium, evidence and/or general agreement that a given procedure or creates stronger contractions, and improves conduction, treatment is benefi cial, useful, and effective (Table 30-3). particularly within the calcium-sensitive AV node. Pharmacological Interventions for Cardiopulmonary Emergencies 661 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. In extreme cases, when none of the aforementioned treat- QT produced by Class III drugs can precipitate torsades ments are effective or they are contraindicated, then high- de pointes.100,101 This complication of treatment is more dose dobutamine can be used to overcome the competitive common in patients with low blood potassium, possibly blockade. secondary to use of a potassium-wasting diuretic like furosemide. Torsades, as it is more commonly referred to, appears similar to ventricular tachycardia on the ECG. This similarity can lead to disastrous consequences as Street Smart ventricular tachycardia erroneously treated with Class III drugs can further worsen the patient’s condition. Beta-blockers prevent the refl exive tachycardia Indications that follows a loss in blood pressure. Paramedics Class III drugs can be thought of as “wide-spectrum” anti- often depend on monitoring a mounting tachycardia dysrhythmics, effective in treating both atrial and ventricular to evaluate for hemodynamic decompensation. dysrhythmia. Amiodarone, for example, prolongs the refrac- Beta-blockers prevent the tachycardia and thus tory period of all cardiac conductive tissues and therefore is mask the impending hypotension associated effective in treating atrial fi brillation, atrial fl utter, and WPW, as well as ventricular tachydysrhythmia.102 with decompensated shock. With the loss of this Amiodarone does not exhibit the reverse use-dependence compensatory mechanism, patients on beta-blockers that is common with other drugs in this class. Amiodarone are also more prone to orthostatic hypotension. also exhibits some Class I and II qualities as well, making its exact mechanism of action more diffi cult to establish. However, its predominant effect is on the duration of the Class III Drugs action potential. Amiodarone has received a great deal of attention for When the sodium channels are all open, at the end of phase its reported effectiveness during ventricular fi brillation or zero, the cell is incapable of being further stimulated and is ventricular tachycardia. The ARREST study (Amiodarone said to be refractory to stimulation. This period of time cor- in the Out-of-Hospital Resuscitation of Refractory responds with the fi rst one-half of the T wave of an ECG. Sustained Ventricular Tachyarrhythmias), published in the The exodus of potassium from the cell marks the start New England Journal of Medicine, seemed to demonstrate of the repolarization, or phase 1 of the action potential. The that patients receiving amiodarone during cardiac arrest are speed of repolarization is a function of local conditions at the more likely to survive until arrival at the hospital. However, cellular level (acidity, hypoxia, etc.) as well as the order of the study did not have the statistical power to detect differ- depolarization. Therefore, each cell repolarizes at a slightly ences in survival to discharge from the hospital.103 different rate. Based on the power of this study, the American Heart Some repolarized myocardial cells are vulnerable to Association (AHA) has given amiodarone a Class IIb rec- reactivation. Thus, the myocardial tissue is said to be rela- ommendation (possibly helpful) in its Advanced Cardiac Life tively refractory (the second one-half of the T wave). A strong Support (ACLS) guidelines. stimulus (e.g., from a late depolarizing ectopic focus) can The ALIVE trial (Amiodarone vs Lidocaine in Prehospital initiate a premature second action potential during this vul- Refractory Ventricular Fibrillation Evaluation) seems to nerable period. The result can be a chaotic depolarization of indicate the superiority of amiodarone over lidocaine in the myocardial cells (recorded as ventricular fi brillation on the treatment of out-of-hospital cardiac arrest due to ventricular ECG) or creation of a unidirectional block, setting the stage fi brillation or ventricular tachycardia.104 for a circus movement. Class III drugs prolong the absolute refractory time of myocardial tissues by blocking the potassium channels and Class IV Drugs decrease the incidence of early depolarizations. Class III Free calcium, released from within the cells via calcium drugs are also taken up more quickly by normal cells than by channels during depolarization, binds with troponin and ini- ischemic cells, demonstrating a reverse use-dependence. As a tiates muscular contraction (excitation-contraction coupling). result of a prolonged refractory period of normal myocardial There are two types of calcium channels in myocardial and cells secondary to reverse use-dependence, slower ischemic smooth muscle: L-type (long-lasting) and T-type (transient). myocardial cells can depolarize without danger of initiating a L-type calcium channels are more abundant in the heart and second ectopic action potential. calcium channel blockers predominantly affect L-type cal- The effect of Class III drugs upon the action poten- cium channels. tial can be observed by the lengthened QT interval on the The different effects of calcium channel blockers upon the ECG, the visible demonstration of the depolarization– heart are owed to the various types of tissues within the heart repolarization time. In a small population, the prolonged and give rise to the therapeutic benefi ts of calcium channel 662 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. blockers during coronary artery syndrome. Calcium chan- nel blockers are also effective antihypertensive agents. These Street Smart drugs inhibit the contraction of the smooth muscle found within the middle layer, the tunica media, of blood vessels. The result is widespread vasodilation in the peripheral cir- Digitalis toxicity can lead to bizarre derangements culation. Peripheral vasodilation reduces peripheral vascular of conduction, including the creation of atrial resistance, crudely measured as diastolic pressure, and lowers tachycardias along with intermittent AV blocks. The the blood pressure. This reduction in afterload decreases the unsuspecting provider who administers a calcium work of the heart as well. As a group, calcium channel block- ers are well-tolerated and have fewer side effects than other channel blocker to a digitalis toxic patient may see antihypertensive agents, such as beta-blockers. the creation of a lethal AV block. Calcium channel blockers are also effective anti-anginal agents. The pain of the ischemic heart (i.e., angina) is the result of a mismatch between blood supply (usually from Precautions compromised coronary arteries) and demand (from an over- taxed heart). The combination of peripheral vasodilation The fi rst generation of calcium channel blockers, starting (reduced |
afterload, which in turn reduces the work of the with verapamil (which was developed in Europe in 1963), heart) and local coronary artery vasodilation re-establishes frequently created profound hypotension, secondary to the balance between myocardial supply and demand and widespread vasodilation. Second generation calcium chan- eliminates angina. nel blockers, including diltiazem (which was developed in Perhaps the most important use of calcium channel Japan), are less likely to create hypotension and are therefore blockers is as an antidysrhythmic drug which decreases auto- preferred for prehospital use during an emergency. maticity. The effect of calcium on the cardiac conduction is If life-threatening hypotension does occur, co- dissimilar to the effect of calcium upon muscle. In the muscle, administration of calcium gluconate can provide free calcium calcium combines with troponin to create a contraction. In for improved muscle contraction and a return toward a nor- the cardiac conduction, calcium is part of the depolarization– mal blood pressure. Similarly, profound bradycardia can be repolarization cycle. Specifi cally, depolarization is generated treated with the parasympathetic blocker atropine to restore by the inward fl ow of calcium during phase zero. a normal heart rate. Portions of the cardiac conduction system that are espe- cially sensitive to increased calcium are the SA node (result- Unclassifi ed Antidysrhythmic Agents ing in increased automaticity) and the AV node (resulting in There are a certain number of antidysrhythmic agents which increased conduction). do not fall cleanly into one of the Vaughn-Williams classifi - Calcium channel blockers decrease the automaticity of cations and are therefore presented separately. For example, the SA node, resulting in a slower heart rate (negative chro- adenosine, a naturally occurring purine nucleoside, does not notropic effect). Calcium channel blockers also decrease the fi t into the Vaughn-Williams classifi cation system, yet is used conductivity across the AV node, resulting in slower con- to treat certain tachydysrhythmias. duction in the AV node (negative dromotropic effect). The Adenosine affects the nervous system of the heart, yet combination of a slower heart rate and slowed conduction to it is not a neurotransmitter nor is it a hormone. Adenosine the ventricles creates an overall reduction in the number of is a neuromodulator. A neuromodulator is a substance contractions. These effects make class IV agents, the calcium that adjusts, or modulates, the rate of a neuron’s discharge. channel blockers, the preferred antidysrhythmic agents for Adenosine’s effect is to either increase or decrease cyclic specifi c dysrhythmias such as supraventricular tachycardia. AMP levels, which in turn adjusts calcium levels and infl u- ences the strength of contraction. Adenosine may serve a special protective function Contraindications in ischemic heart tissue. In normal heart tissue, adenosine Calcium channel blockers are particularly effective in the stimulates purine receptors (which in turn reduce the inward calcium-sensitive AV node. However, any calcium chan- fl ow of calcium) and increases the outward fl ow of potas- nel blocker can worsen a pre-existing AV heart block and sium during phase 4 (repolarization) of nervous tissue. It thus therefore should be given with extreme caution to patients increases the strength of contraction of heart muscle. with pre-existing AV nodal disease or sick sinus syndrome. During periods of tissue hypoxia, ischemic cells release Calcium channel blockers can also interact with beta- cyclic AMP (cAMP) into the interstitial space in the form blockers to create extreme bradycardias. of adenosine. Free serum adenosine then enters the coro- Digitalis, a medication prescribed for heart failure, nary blood vessels and blocks adrenergic receptors as well has a similar inhibitory effect upon the AV node. The combi- as stimulating the release of nitric oxide (NO), the vasodi- nation of a calcium channel blocker and digitalis can create lator thought to be at work in nitroglycerin. This combina- profound bradycardia and subsequent syncope. tion of effects creates vasodilatation and increased coronary Pharmacological Interventions for Cardiopulmonary Emergencies 663 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. circulation. However, this vasodilatation is not limited to the uptake also has implications for intravenous administration. heart. When adenosine is given intravenously, it produces a In order for therapeutic levels to be achieved in the heart (the generalized fl ush and produces hypotension in about 20% of target organ in most cases), adenosine must be given as a the patient population. rapid bolus via the shortest route to the heart. Adenosine also acts to inhibit the effects of epinephrine Xanthine, a prodrug of respiratory medication aminophyl- on the SA node (negative chronotropic effect) and gener- line, causes bronchodilation by blocking adenosine receptors. ally slows the conduction (negative dromotropic effect). It is Foods that commonly contain xanthine compounds include this action which makes adenosine useful as an antidysrhyth- teas and coffee. Higher than normal doses of adenosine may mic agent. be needed to overcome the competitive blockade produced by Adenosine’s inhibition of norepinephrine release is so the xanthine compounds. overwhelming that often, following rapid intravenous admin- Conversely, adenosine should be administered cautiously istration, the heart is rendered momentarily asystolic. The to patients with reactive airway diseases, such as asthma, for therapeutic goal of adenosine administration in those cases is fear of precipitating a life-threatening bronchospasm. to stun the entire myocardium so as to permit the SA node to recommence its role as the dominant pacemaker. Vasopressin Adenosine is particularly effective in treating aberrant Vasopressin, or antidiuretic hormone (ADH), is a naturally conduction over accessory conductive pathways (e.g., the occurring peptide created in the posterior lobe of the pituitary bypass tracts in WPW and LGL) or in preventing a unidirec- gland. Vasopressin was known to have potent vasoconstrict- tional block. Unidirectional blocks can, under the right cir- ing properties at higher doses and has been used to treat dia- cumstances, create a circus movement within the conduction betes insipidus and bleeding esophageal varices, with varying tract and cause an extreme rate supraventricular tachycardia. degrees of success, in the past. However, vasopressin was pri- marily regarded as a hormone for maintaining water balance Indications in the kidney. Researchers were surprised to fi nd elevated Adenosine is used to treat supraventricular tachycardias asso- levels of vasopressin in survivors of cardiac arrest.105 Upon ciated with WPW or LGL syndromes as well as a number closer examination, medical researchers felt that vasopressin of other narrow-complex tachycardias. Adenosine is ineffec- might have some theoretical advantages over epinephrine in tive in treating the rapid ventricular response associated with cardiac arrest. atrial fi brillation or atrial fl utter; errors of automaticity. These Epinephrine is traditionally considered the drug of conditions involve ectopic pacemakers outside of the normal choice in cardiac arrest because it increases the strength of conductive system and thus are less affected by adenosine. contraction, or in the case of ventricular fi brillation, it coars- ens the fi brillation and thereby improves the chance of suc- cess with defi brillation. Epinephrine also raises peripheral vascular resistance, thereby increasing backfl ow into the Street Smart coronary arteries and improving cerebral circulation. On the other hand epinephrine, particularly high-dose epinephrine, A wide-complex tachycardia of unknown origin can increases the oxygen demand—as well as the demand for present a diagnostic dilemma. The dysrhythmia could ATP—at a time when the heart is depleted.106 Epinephrine also appears to adversely affect pulmonary function during be a potentially lethal ventricular tachycardia or it cardiac arrest, by shunting blood away from the lungs to the could be an atrial fi brillation in a patient with WPW. heart and brain.105 Inappropriate treatment can produce less than desired In fact, currently no research exists which suggests effects. As adenosine is not an effective treatment that epinephrine administration increases survival. Several uncontrolled studies indicate that epinephrine administration for ventricular tachycardia, its administration can during cardiac arrest negatively correlates with survival to serve as a diagnostic tool for differentiating the discharge.107 However, until better studies are available, epi- two rhythms and help guide subsequent therapeutic nephrine remains in the standard guidelines for management interventions. of cardiac arrest.108 Vasopressin increases vascular tone and perfusion pres- sures, like epinephrine, but does not have the associated neg- ative catecholamine-induced effects of increased heart rate Precautions and oxygen consumption which are seen with epinephrine. Adenosine, as a naturally occurring nucleoside, is rapidly Vasopressin has a relatively long half-life and therefore taken up by red blood cells and vascular endothelial cells, need only be administered once in order to achieve thera- where it is metabolized into inosine and then uric acid. This peutic levels. Early research fi ndings seem to indicate metabolism occurs so rapidly (the half-life of adenosine is 5 better patient survival when vasopressin is administered to 10 seconds) that toxicity is nearly impossible. This rapid along with epinephrine every three to fi ve minutes.109 664 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. A large out-of-hospital clinical trial is needed before it can or an obstruction in the outfl ow from the heart due to valve be defi nitively stated that vasopressin is of greater benefi t disease. than epinephrine in cardiac arrest. Diastolic heart failure is that condition in which the heart has diffi culty fi lling properly and there is subsequent loss Cholinergic Blocking Agents of cardiac output. Causes of diastolic heart failure include Cholinergic blocking agents, as a class, were discussed ear- remodeling of the ventricular chamber secondary to chronic lier. However, atropine, a specifi c parasympathetic blocking hypertension, obesity, and systolic heart failure. agent commonly used to treat symptomatic bradycardia, is The pathophysiology of heart failure begins with a loss now revisited. of cardiac output, from whatever cause, which stimulates the Atropine blocks the parasympathetic neurotransmitter baroreceptors. The baroreceptors in turn increase sympathetic acetylcholine at the muscarinic receptors. This effectively discharge (epinephrine) to adjust for the volume difference diminishes the infl uence of the primary parasympathetic and maintain perfusion of vital organs. nerve, the vagus nerve (vagal tone), and permits the sym- Sympathetic stimulation has a two-fold impact. First, pathetic nervous system to re-establish dominance over the stimulation of alpha-adrenergic receptors preferentially heart’s rate. Excessive vagal tone is often seen in cases of AV vasoconstricts peripheral vascular beds, effectively shunt- node ischemia secondary to occlusion of the right coronary ing blood to core organs, as well as increasing the amount of artery, as occurs during an inferior wall myocardial infarc- blood returned to the heart (preload). With the ventricles now tion. The ensuing bradycardia can be treated effectively with “overfi lled,” Starling’s law dictates that the ventricle will con- atropine. However, increasing tissue demands within the AV tract more forcefully and the stroke volume will increase.112 node at a time when the tissues are ischemic may accelerate Sympathetic stimulation also increases the heart rate damage and lead to an infarction of the AV node, resulting in (positive chronotropic effect) as well as strength of contrac- complete heart block. The decision to use atropine in the set- tion (positive inotropic effect). ting of an AMI must be made with caution. The combination of increased stroke volume and increased heart rate should result in improved cardiac out- put (SV x HR CO). This is the body’s normal response to hypovolemia. The diffi culty lies not in the blood’s volume but Street Smart in the heart’s inability to pump that volume. Alpha-adrenergic stimulation from epinephrine excreted Profound hypoxia produces pupillary dilation. secondary to hypotension increases the systemic vascular During a cardiac arrest, providers often check resistance (the afterload) against which the heart must pump. This “afterload mismatch” causes blood to back up into the pupillary response to assess the effectiveness of pulmonary circuit, resulting in pulmonary congestion and cardiopulmonary resuscitation. Atropine dilates edema. |
Elevated pressure is transmitted across the pulmonary pupils, thus rendering this sign inaccurate. circuit and through the right ventricle back into the systemic circulation, creating peripheral edema. The kidneys, now underperfused, activate the renin- Heart Failure angiotensin-aldosterone mechanism, a tri-axis of hormones which combine to preserve blood volume. This results in Heart failure is the heart’s inability to pump enough blood to more fl uid retention, further increasing the work of the over- meet the body’s demands. The result is hypoperfusion of vital taxed heart. organs and potentially the onset of a shock syndrome. Heart In an effort to compensate, the heart dilates to accept failure affects over 4 million people in the United States and more blood and the muscle fi bers thicken, a process called is the most common hospital discharge diagnosis in patients hypertrophy, in order to pump more forcefully. Along with over the age of 65.110,111 a sustained tachycardia secondary to persistent sympathetic Heart failure can be divided into two categories: systolic stimulation, the heart is able to compensate, sometimes for heart failure and diastolic heart failure. Systolic heart fail- years. ure is the condition in which the heart cannot pump adequate The dual effect of dilation and hypertrophy upon the left amounts of blood into the circulation. The result can either ventricle slowly changes the shape of the interior chamber, be forward failure (a loss of cardiac output and systolic called remodeling, into a less effective confi guration. The blood pressure) or backward failure (a retrograde buildup of remodeled chamber can no longer fi ll properly and diastolic pressure that is transmitted to the low pressure lung fi elds heart failure ensues. and creates pulmonary congestion and pulmonary edema). When the heart reaches the point where it can no lon- Frequently, this left-sided heart failure progresses through the ger compensate and overcome the increasing demands put right ventricle and into the systemic venous circulation. upon it, the heart enters the descending limb of the Frank- Causes of systolic heart failure include loss of con- Starling curve and cardiac output falls. In 1918, Frank tractile strength secondary to acute myocardial infarction and Starling advanced the idea that the force of the heart’s Pharmacological Interventions for Cardiopulmonary Emergencies 665 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. contraction is proportional to the length of the muscle fi bers, mechanism (Figure 30-9). This is an effective treatment for which are increased with increased ventricular fi lling. When hypertension in many patients. the myocardial fi bers can no longer stretch, then the muscle ACE inhibitors are seeing greater use in heart loses contractile strength (the backside of the curve). The failure patients as they appear to not only interrupt the pharmaceutical goals in heart failure are essentially two- renin- angiotensin-aldosterone mechanism, thereby prevent- fold: reduce the preload and provide inotropic support to the ing fl uid retention, but they also control hypertension and failing heart. thus reduce the work of the heart. They are also effective in reversing left ventricular systolic dysfunction. Long-term use Angiotensin-Converting Enzyme of ACE inhibitors have been shown to improve survival of (ACE) Inhibitors even severe heart failure patients by returning the heart to Baroreceptors in the kidneys, sensing a low fl ow state due to its original condition.113 reduced arterial pressure caused by heart failure, release the Therapeutic Approaches enzyme renin. Renin is converted into angiotensin through a number of steps. to Heart Failure Angiotensin has a number of physiologic effects. Hippocrates advanced the idea that the four humors, including Angiotensin stimulates the production of aldosterone in the blood, had to be in balance in order to maintain good health. adrenal cortex. Aldosterone, a mineralocorticoid, promotes When the body was swollen (e.g., from heart failure), then it the excretion of potassium by the kidney in exchange for was thought that blood had to be released from the body to retaining sodium and thus water. Angiotensin also stimulates restore balance. For centuries, fi rst monks, and then barber- the secretion of vasopressin, which in turn causes peripheral surgeons, continued the practice of bloodletting to relieve vasoconstriction and increased peripheral vascular resis- “dropsy,” the term used for heart failure. Leeches replaced the tance. Perhaps most importantly, angiotensin is a potent lancet in the 1800s, but the practice continued. In fact, the word v asoconstrictor in itself. It is 40 times more potent than “leech” comes from the Old English “laece” which means phy- norepinephrine in causing peripheral vasoconstriction. sician.114 Even George Washington was bled by Dr. Benjamin The conversion of renin into angiotensin depends on an Rush. Washington’s leeching is thought to have been a contrib- enzyme called angiotensin-converting enzyme (ACE). ACE uting cause to his death. While this treatment may appear to be inhibitors, such as captopril, oppose the conversion of renin to barbaric by today’s standards, it nevertheless was effective for angiotensin and thus upset the renin-angiotensin-aldosterone treating heart failure in some instances. Response mediated by the sympathetic nervous system Activation of β1 adrenoceptors Cardiac on heart output Sympathetic activity Activation of α1 adrenoceptors Peripheral on smooth muscle resistance Decrease in Increase in blood pressure blood pressure Renal blood Renin Angiotensin II flow Aldosterone Glomerular Sodium, water filtration rate Blood volume retention Response mediated by the renin-angiotensin-aldosterone system Figure 30-9 Afterload mismatch. 666 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. As primitive as these early interventions may have The reabsorption of water and salts occurs in various por- seemed, subsequent pharmaceutical approaches to heart fail- tions of the nephron. Approximately 65% of the water—as ure have used the same tactic—reduce the volume of blood in well as bicarbonate, glucose, and two-thirds of the sodium—is order to decrease the work of the heart and allow the heart to reabsorbed in the proximal tubule (Figure 30-10). function more effi ciently. The proximal tubule is also the site of absorption of The reduction of blood can occur in two ways: either organic acids, such as uric acid, and metabolites of medica- removal of fl uid from the circulation via the kidney (diuresis) tions. The remaining fi ltrate passes into the loop of Henle. The or relocation of fl uid into other compartments (vasodilation). cells lining the narrow ascending loop of Henle are extraordi- nary because they are watertight (i.e., impermeable to water). This section of the nephron actively reabsorbs chloride and Diuresis sodium. To this point the exchange has been unregulated. Approximately 20% of the blood entering the kidney’s The remaining 15% of fi ltrate which remains now enters glomerular process diffuses its water and solutes (salts the distal convoluted tubule. The regulation of potassium and in solution) into the Bowman’s capsule of the kidney’s sodium reabsorption in this portion of the nephron is con- nephron. Only the formed elements, such as red blood cells trolled by aldosterone. and plasma proteins, are held back. The water and plasma The remaining fi ltrate, now called urine, is passed into solutes, now called fi ltrate, pass through the different por- the collecting duct. Vasopressin, or antidiuretic hormone tions of the nephron and are reabsorbed to go back into the (ADH), regulates the fi nal reabsorption of water in this por- circulation. In an average day the kidney will fi lter 180 liters tion of the nephron. The process of renal fi ltration is complete of blood but only produce one to two liters of urine. with 99.2% of the fi ltrate returned to the central circulation Blood vessel Part of a nephron Tubular filtration — Afferent water, glucose, amino acids, salts, High arteriole and urea pass through the glomerulus. blood pressure Urinary Kidney tubule force Filtration filtrate A glomerulus Lining cells (set of capillary of kidney tubules loops) Efferent arteriole Tubular reabsorption includes water, glucose, amino acids, vitamins, bicarbonates, CA+, Mg+, N2+, and Cl- Tubular secretion includes ammonia, creatinin, hydrogen, potassium, and some drugs Urinary meatus Excreted urine Urination (micturition) Figure 30-10 Cross-section of nephron. Pharmacological Interventions for Cardiopulmonary Emergencies 667 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. and the remainder, the urine, being sent to the bladder via the Bumetanide, another loop diuretic, also blocks the reab- ureters to be excreted. sorption of chloride in the proximal tubule. This dual effect makes bumetanide more potent than furosemide. This second Diuretic Agents site of action makes bumetanide effective for patients who are resistant to furosemide. The creation of urine is controlled by the pressure of the blood entering the kidney, which in turn is controlled (in part) by the sympathetic nervous system, and the concentration of the salts Precautions in the blood, as well as the ADH level. Patients without prior experience with diuretics may unpre- Each class of diuretics affects a different portion of the dictably experience a diuresis of large quantities of urine. The kidney’s nephron and therefore has a slightly different effect result can be severe hypovolemia, hypoperfusion, and frank on diuresis. Carbonic anhydrase inhibitors affect water reab- shock. In those cases, gentle rehydration with intravenous sorption in the proximal convoluted tubule, whereas the loop solutions, such as Ringer’s lactate, can re-establish lost vol- diuretics and the thiazides affect the loop of Henle. Finally, ume and restore the blood pressure. the potassium-sparing diuretics affect the distal convoluted Overly aggressive treatment of congestive heart failure, tubule. usually manifested by pulmonary edema, can also lead to Regardless of the affected portion of the nephron, all even greater problems in the care of the patient over the long medications which cause the increased loss of fl uid and salts term. When confronted with a patient with pulmonary edema, from the body are called diuretics. This loss of fl uid volume Paramedics may be inclined to think that the patient is fl uid decreases the amount of circulating blood volume and ulti- overloaded. More accurately, these patients are fl uid mis- mately decreases the work of the heart. Therefore, the uni- placed. That is, the blood is being sequestered in the venous versal goal of diuretic therapy is to reduce the work of the circulation (venous pool) and is putting pressure on the fail- heart and permit the heart to function more effi ciently. ing heart to pump it forward. There are two treatment path- Proximal Tubule Diuretics ways to relieve this condition. First, the Paramedic can cause a diuresis which will in turn reduce the blood volume return- The enzyme carbonic anhydrase mediates the acid and bicar- ing to the heart. Alternatively, the Paramedic can increase the bonate reaction that creates water and carbon dioxide (H venous pool’s capacitance, temporarily relieving the heart’s HCO H O CO ) in the blood. In the sodium bicar- 3 2 2 burden and allowing it to recover. bonate and acid reaction, carbonic anhydrase inhibitors hold The classic diuretic for the treatment of acute pulmo- onto a hydrogen ion in exchange for a sodium ion that is sub- nary edema has been furosemide. Prompt treatment with sequently secreted by the kidneys. As a matter of principle, furosemide will provide the patient with immediate relief of water follows salt, and water is also excreted. symptoms.117,118 This relief is due to the two-fold action of Carbonic anhydrase inhibitors include acetazolamide furosemide. Furosemide’s |
immediate effect is as a vasodila- (a sulfonamide without antibacterial properties). In com- tor. Within fi ve minutes of administration, furosemide reduces parison to loop diuretics, carbonic anhydrase inhibitors the heart’s work by reducing the preload through vasodila- are a weak class of diuretics which are used in very lim- tion, increasing the venous pool capacitance. Following the ited cases. For example, mountain climbers who hike above vasodilatation, within 20 minutes of the onset of action furo- 10,000 feet are prone to high-altitude pulmonary edema semide causes diuresis. This diuresis removes fl uid from the (HAPE) and high-altitude cerebral edema (HACE).115,116 central circulation and reduces the heart’s work. Acetazolamide is sometimes prescribed to climbers to Patients in acute heart failure are not suffering from prevent HACE and HAPE. The exact mechanism of being fl uid-overloaded. More correctly, the blood volume action is unknown but is thought to be associated with is improperly distributed, leading to an input–output mis- the mild metabolic acidosis created by the drug and the match. Vasodilator therapy may be more benefi cial to the resulting deeper respirations which occur during the moun- patient in the long run. More discussion about vasodilator taineer’s sleep. therapy follows. Potassium, an important cardiac electrolyte, is closely Loop Diuretics associated with sodium. As loop diuretics cause the excre- Loop diuretics, as a class, inhibit the reabsorption of the elec- tion of sodium, they also cause a loss of potassium, earning trolytes: sodium, potassium, calcium, and magnesium, as well them the label “potassium wasters.” Serious potentially life- as water in the ascending loop of Henle. This portion of the threatening cardiac dysrhythmias can follow the development nephron is largely responsible for the concentration of urine of low serum potassium or hypokalemia. For this reason, electrolytes and subsequent volume of urine. Loop diuretics potassium supplements are often co-prescribed to patients on are very effective and have a rapid onset of action. For these loop diuretics. True toxicity from loop diuretics is rare. For reasons, loop diuretics are often preferred in an emergency. example, patients have been given 2,000 mg of furosemide Furosemide is an example of a commonly used medication without toxic effect. This “high ceiling” makes these diuret- in this class. ics relatively safe to administer. 668 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Osmotic Diuretics who cannot tolerate potassium supplements. Unfortunately, Any substance with a large molecular weight which can- potassium-sparing diuretics, as a class, are weak diuretics. To not pass through a semipermeable membrane will create an improve their effi ciency, as well as maintain the advantage of osmotic effect. The presence of formed elements and blood preserving potassium, they are often given in combination proteins, such as albumin, in the bloodstream creates an with the thiazides. osmotic effect. This effect, called colloidal osmotic pressure Several agents (e.g., amiloride and triamterene) work (COP), occurs because these large molecules cannot pass indirectly in the distal tubule, while spironolactone works by through the blood vessel walls. blocking the effects of aldosterone in the distal tubule. As a Similarly, when chemicals with a large molecular weight result of these two actions, sodium and water are excreted and (i.e., heavy molecules) pass into the fi ltrate via the fenestrated potassium is retained. membranes within the kidney (a very forgiving membrane Spironolactone, as an aldosterone-antagonist, also has that is 100 to 400 times more permeable than ordinary capil- a secondary use in the treatment of hyperaldosteronism, an laries) and travel to the loop of Henle to encounter a semiper- adrenal disease. meable membrane, they are entrapped. However, these heavy molecules continue to create an osmotic effect and thus draw Vasodilator Therapy fl uids into the fi ltrate. Certain vasodilators work on the same mechanism as nitrates, Examples of heavy molecules that are effective osmotic thereby creating a direct vasodilation in the blood vessels. diuretics include mannitol (a complex sugar) and urea. Osmotic Since a larger portion of blood and blood vessels is on the diuretics are used to reduce edema in special cases; for exam- venous side of the central circulation, the venous side is more ple, mannitol is used to treat increased intracranial pressure affected. This causes a drop in the venous pressure and there- secondary to cerebral edema. Osmotic diuretics are also used fore the amount of preload the heart receives. to prevent kidney failure by forcing a continuous diuresis. Alternatively, other vasodilators create relaxation of the Caution must be exercised whenever osmotic diuretics are muscle within the vessel walls, resulting in dilation. Since administered. Overly aggressive treatment can result in hypo- arteries and arterioles have more muscle than veins and volemia (leading to hypoperfusion and shock), hypokalemia venules, these medications have a more pronounced effect on (leading to ventricular dysrhythmias), and hyponatremia the arterial side of the central circulation. Arterial vasodila- (leading to seizures). tion directly translates to lowered diastolic pressure, reduced peripheral vascular resistance, and a reduction in cardiac Distal Tubule Diuretics afterload.119 The thiazides were one of the fi rst diuretics used in medical therapeutics for the treatment of heart failure. As sulfonamide Afterload Reduction derivatives, the thiazides also work like carbonic anhydrase The arteriole beds are largely controlled by the alpha receptors inhibitors. However, they work in the distal tubule instead of of the sympathetic nervous system. Alpha-receptor antago- the proximal tubule. nists prevent vasoconstriction and the resulting increases Thiazides inhibit the reabsorption of sodium and there- in peripheral vascular resistance (afterload) that occur as a fore increase the excretion of sodium in the urine. The urine, result of vasoconstriction. An example of an alpha-blocker is now hyperosmolar, collects more water as it passes through hydralazine, a current and commonly used alpha-blocker. the tubules. Thiazides also increase the excretion of potas- The diffi culty with using alpha-blockers lies in the sym- sium along with the sodium. pathetic nervous system’s response to the decrease in diastolic Indications for thiazides, such as hydrochlorothiazide, pressure. The baroreceptors refl exively stimulate the sympa- include relief from mild to moderate heart failure as well as thetic nervous system to increase the blood pressure. This is the treatment of mild to moderate hypertension. Thiazides are achieved via peripheral vasoconstriction, now inhibited by often preferred as a treatment for hypertension because they the alpha-blockers, and tachycardia. This tachycardia can tax are inexpensive (a benefi t for patients on a fi xed income), the already overtaxed heart and induce ischemia. To prevent easy to administer, and have fewer side effects than other this refl exive tachycardia, a beta-blocker is often given in diuretics. combination with the alpha-blocker in an effort to balance the Thiazides are also potassium wasters and have the same effects of each. precautions as other potassium wasters. Potassium deple- Other arterioles affecting antihypertensives work directly tion can, for example, predispose a patient to a number of upon the smooth muscles in the arteriole walls. These agents, dysrhythmias. usually administered intravenously, are very effective in reducing peripheral vascular resistance (the diastolic blood Potassium-Sparing Diuretics pressure) and reduce the heart’s work. Potassium-sparing diuretics are particularly attractive for use Unfortunately, the same issue exists for these agents (e.g., in patients who are sensitive to hypokalemia (e.g., patients diazoxide) as did for the alpha-blockers. Again, beta-blockers on digitalis) or patients who require a diuretic therapy but are occasionally co-prescribed to balance the effects of each. Pharmacological Interventions for Cardiopulmonary Emergencies 669 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Preload Reduction When the level of cyanide exceeds the liver’s capacity to In the not too distant past, Paramedics used a device called detoxify it, then cyanide poisoning can occur. Fortunately, the a “rotating tourniquet” to mechanically sequester blood in half-life of nitroprusside is 2.7 days. Cyanide levels can be the periphery. That technique, though fraught with complica- tested daily to ensure that the patient remains symptom-free. tions, was effective in reducing preload. Today, medications Nitroprusside infusions are easily identifi ed because the are used to obtain a similar effect. solution container must be protected from light. Therefore, Nitrates are potent vasodilators, and their main impact the IV bag is always covered with aluminum foil or another is on the venous circulation. Dilating the venous circulation, similarly opaque material. nitrates increase the “pooling” of blood in the venous circula- Nitroprusside infusions must be very carefully titrated, tion and reduce the preload returning to the heart. In essence, typically to the patient’s blood pressure, starting at 0.3 micro- nitrates create an “internal phlebotomy” by withholding blood grams per kilogram of patient’s weight per minute (mcg/kg/ from the central circulation. min). Therefore, nitroprusside infusions are typically placed A number of long-acting nitrates have been developed on an infusion pump. for this purpose. Perhaps the earliest long-acting nitrates were oral preparations, such as isosorbide. Isosorbide now Cardiac Glycosides comes in extended release capsules, chewable tablets, and Digitalis is the quintessential cardiac glycoside. One of the sublingual tablets. few plants that make a steroid similar to animal steroids, digi- To further extend the vasodilator effects, nitrates are also talis is processed from the foxglove plant. Used for hundreds available in transdermal systems. These “patch” systems con- of years as the “housewife’s recipe” for swelling and edema, tain nitrate in a gel-like “reservoir.” After the gel melts, the drug digitalis did not enter into modern pharmacy until 1876.120 The passes through the skin and then is absorbed, by passive diffu- story is told of a patient who went to Dr. William Withering, sion, into the bloodstream. There are a number of patch systems a Scottish physician, with “dropsy” (congestive heart failure) on the market and each works in a slightly different manner. and was diagnosed as incurable. The patient then went to a Paramedics often use nitroglycerin paste for the same gypsy who treated him with a secret herbal remedy and he effect. A ribbon of paste, measured in one-half inch incre- recovered. Intrigued, Dr. Withering sought out the gypsy and ments, is placed on an impervious paper and placed against bartered for the remedy. The key ingredient in the concoction the patient’s skin. The selection of a site for the paste’s place- was the purple foxglove, digitalis purpurea (L). ment is important. The paste should be applied to a hairless Digitalis had long been known for its toxicity, having area, usually on the upper anterior chest, where it is clearly been used by the Romans as rat poison and in medieval “trials visible. Avoid placing the patch below the knees or elbows. by ordeal.” However, it was not thought to have many medici- Circulation is frequently poor in these areas and absorption nal uses. Dr. Withering made his fortune on the “discovery” less predictable. of the medicinal uses of digitalis after he recounted its ben- Alternative placement sites include the shoulder or the efi ts in a treatise entitled, “An Account of Foxglove.” In that inside of the upper arm. Some Paramedics will loosely encir- treatise, he strongly advised that the effects of digitalis on cle the limb with a plastic wrap to prevent liquefi ed nitroglyc- the patient be closely monitored and that it was imperative to erin paste from dripping. individualize the dose and schedule. No wiser words could In every case, it is important to report where the paste have been offered as digitalis toxicity is a common impedi- was applied when patient care is transferred. Nitroglycerin ment to the drug’s use.20 can induce signifi cant hypotension, in which case the fi rst action should be to remove the paste. Failure to notify other providers of the presence of nitroglycerin paste |
can lead to Mechanism of Action inappropriate treatment of the hypotension. Digitalis has two unique therapeutic benefi ts: a slowing of the Nitroprusside is an effective intravenous vasodilator cardiac conduction, resulting in increased ventricular fi lling, that has a greater impact on the venous circulation (preload) and increased strength of contraction without the use of addi- than on the arterial circulation (afterload), making it attrac- tional oxygen. Together, these effects culminate in an overall tive for the treatment of acute heart failure, especially heart decrease in the heart’s work. This is a desirable situation for failure secondary to valvular regurgitation. Nitroprusside is the compromised myocardium, as it allows for more effi cient also used to treat acute hypertensive crisis, an abnormal and functioning. potentially life-threatening elevation of blood pressure. Digitalis acts by binding to and disabling (blocking) Na/ Chemically, nitroprusside contains fi ve cyanide groups K ATPase, the enzyme that breaks down ATP to release its bound to nitric acid, the active ingredient in nitroglycerin, energy. Without ATP breakdown there is no energy to power within its structure. When the nitric acid breaks off and the Na/K pump during repolarization. The accumula- causes vasodilation, the cyanide remains. The free cyanide tion of intracellular sodium, which results from the failure is then metabolized into thiosulfate by the liver and excreted of the sodium-potassium pump, leads to an ionic imbalance. harmlessly. Calcium is then exchanged to help maintain that balance. 670 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. The slowed depolarization prolongs the cardiac cycle (a negative chronotropic and negative dromotropic effect), lead- ing to reduced heart rate. This maximizes the diastolic poten- tial of Starling’s Law, as the slowed heart has more time for ventricular and coronary artery fi lling. The heart is further slowed when digitalis inhibits the calcium- sensitive AV node from passing the action potential down the ST bundle branches to the ventricles. This slowing of AV node con- duction can be observed by a lengthening of the PR interval. QT The increased calcium also produces more excitation- Abnormal QTc is > 0.44 sec in males coupling of actin and myosin in the ventricle’s myocardial and > 0.45 sec in females fi bers and a stronger contraction of the now overfi lled ventri- cle. This improvement in the strength of contraction, a posi- tive inotropic effect, is done without consuming additional oxygen. Electrocardiographically, the digitalis effect can be seen Shortened QT interval by the prolonged PR interval, the shortened QT interval, and Characteristic down-sloping ST depression an inverted T wave, the impact of altered repolarization oppo- Classic scooped-out ST segment site of the major QRS forces (Figure 30-11). Figure 30-11 The digitalis effect demonstrated Indications on ECG. In the past, a common cause of congestive heart failure was the loss of atrial kick, which contributes approximately 25% Digitalis also has a relative contraindication during heart of the cardiac output. It also accompanied new onset atrial block. The impact of digitalis upon the calcium-sensitive AV fi brillation.121 In this situation, digitalis slows the racing node can further slow conduction through the AV node and heart, which was trying to compensate for the ventricular aggravate a pre-existing heart block, causing profound brady- fi lling pressure lost to atrial fi brillation. Slowing the heart cardia and hypotension. rate allowed for more ventricular fi lling and thus led to an augmented cardiac output. The positive inotropic effect of Digitalis Toxicity digitalis can further improve cardiac output to levels that are Digitalis has a narrow therapeutic range. As a result, the tolerable for the patient. It should be noted that digitalis does incidence of toxicity is fairly high, so much so that between not convert atrial fi brillation back into normal sinus rhythm, 10% and 20% of nursing home patients receiving digitalis but instead merely slows the ventricular response. will develop digitalis toxicity during the course of treatment. Currently, digitalis has been replaced with better Class II The early identifi cation and treatment of digitalis toxicity will and III agents, which slow the heart without the serious side help to decrease the estimated 34% moderate to severe mor- effects and dangers of digitalis toxicity, some of which will bidity associated with digitalis toxicity. be explained shortly. In many cases of atrial fi brillation, the Several conditions contribute to the problem of digitalis etiology is identifi ed and eliminated (if possible), sometimes toxicity. For one, digitalis is primarily excreted via the kid- by radio ablation therapy in the electrophysiology lab of a neys. Therefore, any change in kidney function, such as can cardiac care center. occur with heart failure, can cause an increase in digitalis to Digitalis may still have a therapeutic advantage in treat- toxic levels.122 ing congestive heart failure from other causes. No other single Digitalis also affects the sodium-potassium pump. chemotherapeutic agent has the same dual actions—negative Ordinary doses of digitalis administered to a patient with chronotropy and positive inotropy—as digitalis. hypokalemia can result in toxicity. This toxicity is not a true toxicity, but rather a pseudo-toxicity (the relative imbalance Precautions between the regular dose and the desired therapeutic effect, A new-onset atrial fi brillation may mask the tell-tale ECG which is exaggerated by the hypokalemia). This pseudo- signs of Wolff-Parkinson-White (WPW) syndrome. Digitalis toxicity is sometimes occasioned by the concurrent use of the mistakenly administered in those cases allows uninhibited potassium-wasting diuretic furosemide. conduction over the bypass tract, as the AV node conduction The mechanism of cardiotoxicity relates to the intra- is slowed by the digitalis. The resulting antegrade conduc- cellular calcium overload, which results from high levels of tion over the bypass tract, in concert with normal conduc- digitalis. This increased calcium load has a two-fold effect. tion down the intra-atrial pathways, can contribute to circus First, it increases spontaneous afterdepolarizations in the movement and high rate tachycardia, which may eventually myocardium. These afterdepolarizations create ectopic beats, deteriorate into ventricular tachycardia/fi brillation. including junctional and ventricular extrasystoles. Unabated, Pharmacological Interventions for Cardiopulmonary Emergencies 671 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. the heightened reactivity of the myocardium can lead to junc- also lead to rebound edema later in the course of the patient’s tional tachycardia and ventricular tachycardia/fl utter. care. This rebound edema is the result of activation of the Concurrent calcium buildup within the AV node depresses renin-angiotensin-aldosterone mechanism by the diuresis. the AV node, causing bradycardia, as low as “35 beats in a In many cases, these patients are already on diuretics and minute.”120 It can even create a complete AV block. This ECG are not “fl uid-overloaded.” More correctly, these patients are manifestation, AV blocks of varying degrees, is seen in 30% fl uid “maldistributed” and only need temporary relief from to 40% of patients with digitalis toxicity. excessive preload. Patients at particular risk are those with Extreme digitalis-induced AV dissociation sets the stage restrictive cardiomyopathy, early phase acute myocardial for a rare but potentially lethal phenomenon called “bidirec- infarction, and mild chronic heart failure. tional tachycardia.” Bidirectional tachycardia is the result of Repeated doses of nitrates may be more effective in these concurrent atrial and junctional/ventricular tachycardia with cases. Nitrates will cause immediate venodilation, increasing a complete heart block at the AV node. the volume within the venous pool, and effectively create an internal phlebotomy. That is to say, a portion of blood vol- Signs of Digitalis Toxicity ume will be temporarily warehoused in the venous circula- Initial signs of digitalis toxicity include bradycardia, as well tion (which has a large capacitance) and taken out of the core as nausea and diarrhea. The latter symptoms of abdominal circulation until the heart can recover. distress, visual changes, and general malaise may be misin- terpreted by the patient as fl u-like symptoms and ignored by Forward Failure the patient. The combination of the losses of potassium from Acute forward failure, or cardiogenic shock, is a failure of the both diarrhea and vomiting only serve to worsen the situation heart as a pump. Regardless of the underlying cause of the and lead to more nausea, vomiting, and diarrhea. pump’s failure, it is imperative to increase the heart’s cardiac As the intoxication continues, the patient may experi- output (blood pressure). ence confusion, which may be misinterpreted as dementia The body’s own compensatory mechanisms depend or depression in the elderly. The patient may also complain on the hormone epinephrine (a catecholamine) to increase of seeing yellow-green halos around lights. At this point, the heart rate (positive chronotropy), speed of conduc- signifi cant cardiac manifestations typically occur, including tion (dromotropy), and most importantly, the strength of tachycardia-induced syncope. contraction (inotropy). Supporting the body’s own com- Overt digitalis overdose, either accidental or otherwise, pensatory mechanisms, Paramedics can infuse additional may be treated emergently with digitalis-specifi c antibody sympathomimetics classifi ed as catecholamines: three natu- fragments (digoxin immune fab). Otherwise, treatments focus rally occurring catecholamines—dopamine, epinephrine, on the cause of the toxicity: reversing hypoperfusion leading and norepinephrine—plus two synthetic catecholamines— to kidney failure, withdrawal of the numerous drugs which dobutamine and isoproterenol. interact negatively with digitalis, or correcting hypokalemia. These vasopressors, drugs which affect blood vessels If the patient is hypokalemic, then potassium replacement directly, increase blood fl ow to vital organs. However, some is provided. Phenytoin has been found useful in treating are associated with signifi cant side effects and should be used digitalis-induced dysrhythmia because of its anticholinergic carefully in the patient with acute heart failure. effects.123 Administration of magnesium as a competitive ion may be helpful in reducing ventricular ectopy, including ven- tricular tachycardia/fl utter. Street Smart Acute Heart Failure Before starting any catecholamine infusion, it is Acute heart failure is a medical emergency that, if untreated, can quickly culminate in death. Acute heart failure can pre- important to rule out hypovolemia as a cause of sent in several ways. The fi rst syndrome is forward failure, a hypotension. Failure to do so may compromise already loss of cardiac output that results in hypotension and rapidly ischemic tissue. “Squeezing dry pipes” with vasopressors progresses to end-organ failure. The other syndrome is back- ward failure, a backup of pressures into the low-pressure lung will not improve blood pressure signifi cantly. fi elds which produces acute pulmonary edema. Acute pulmo- nary edema literally suffocates the lungs, leading to hypoxia and respiratory acidosis. Catecholamines All catecholamines interact directly with sympathetic Backward Failure receptors throughout the body. Alpha-receptor stimulation The goal of treating backward failure, manifested by acute will increase vasoconstriction of peripheral capillary beds, pulmonary edema, is to quickly reduce the preload. Treatment increasing blood in the core circulation while also increasing with diuretics can provide rapid symptomatic relief but can the peripheral vascular resistance the heart must overcome. 672 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Beta-receptors in the heart will both increase the speed of Occasionally, after a subcutaneous injection or intravenous the heart (positive chronotropy) as well as the strength of con- bolus, it is necessary to continuously infuse epinephrine to traction (positive inotropy) and dilate the bronchial smooth maintain blood pressure, particularly in cases of distributive muscle, thereby improving oxygen delivery. However, this shock, such as septic shock and anaphylactic shock. comes at |
a cost of increased work of the heart. Precautions Dopamine Catecholamines are potent medications, so potent that the Dopamine, a naturally occurring catecholamine, is the pre- dose is measured in micrograms (mcg) instead of milli- cursor to epinephrine and has effects similar to epinephrine. grams (mg). Typically infused intravenously, catecholamines At lower doses, one-half to two micrograms per kilogram are carefully titrated to a dose of micrograms per kilogram per minute infusion (0.5 to 2 mcg/kg/min), dopamine dilates of patient weight per minute of infusion (mcg/kg/min) and renal arteries, increasing blood fl ow and subsequent produc- often infused via an intravenous pump which can ensure pre- tion of urine. cise delivery. At higher doses, up to 10 micrograms per kilogram per The patient receiving a catecholamine infusion, in order minute infusion (10 mcg/kg/min), dopamine stimulates the to sustain an adequate perfusing blood pressure, may be drug- beta-receptors of the heart, increasing heart rate and force of dependent. A sudden interruption in the infusion, for any contraction. At the highest doses, 10 to 20 micrograms per reason, can result in a precipitous fall in blood pressure. For kilogram per minute infusion, alpha-adrenergic receptors are this reason, most providers ensure the presence of a second increasingly stimulated. intravenous access site for use if the fi rst intravenous access Alpha-adrenergic receptor stimulation leads to peripheral is lost. vasoconstriction, an increase in peripheral vascular resistance Inadvertent infi ltration of a catecholamine into subcuta- (afterload), and more work for the heart, while elevating the neous tissue, secondary to a dislodged or misplaced catheter, blood pressure via increased venous return (preload). The can result in localized ischemia and necrosis of the tissue. trade-off, a perfusing blood pressure for increased work of Phentolamine, an alpha-adrenergic blocking agent, injected the heart, may induce an acute myocardial infarction and subcutaneously around the catecholamine infi ltration may renal ischemia.124 For those reasons, high dose dopamine is help prevent tissue necrosis, but special care should be taken reserved for severe hemodynamic imbalance. to assure IV patency prior to and during administration of catecholamines. Street Smart Street Smart While dopamine at 4 to 20 mcg/kg/min can increase blood pressure, dopamine 3 mcg/kg/minute or less Commercially prepared catecholamines contain a can actually lower the blood pressure. These lower, preservative (sulfi te) which helps maintain potency. or renal, doses of dopamine also cause a vasodilation Some patients are sensitive to sulfi tes and may have of the mesenteric vessels resulting in venous an allergic reaction to the drug, compounding the pooling. Therefore, dopamine infusions should severity of the situation instead of improving it. always be started at more than 5 mcg/kg/min in the fi eld. Epinephrine Epinephrine, the original catecholamine, is available for injection, inhalation, and infusion. Epinephrine is a power- Dobutamine ful direct-acting synthetic catecholamine. In small doses, Dobutamine is the synthetic analog of dopamine but is more epinephrine is used to treat severe asthma exacerbation and beta-selective than dopamine. This quality makes it less serves as an adjunct to local anesthetics to control bleeding desirable in cases of distributive shock (e.g., septic shock), during wound repair (sutures). In larger doses, epinephrine but very desirable for cardiogenic shock. can reverse cardiovascular collapse secondary to anaphy- Dobutamine is a potent inotropic agent and a weak chro- laxis or coarsen ventricular fi brillation for more effective notropic agent. Therefore, dobutamine does not signifi cantly defi brillation. increase the oxygen demands of the heart but can improve Epinephrine’s rapid onset of action (three to fi ve minutes cardiac output. This makes it attractive for use in cardiogenic by subcutaneous injection) makes it useful in an emergency. shock secondary to pump failure. Pharmacological Interventions for Cardiopulmonary Emergencies 673 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Dobutamine is very effective for patients in cardiogenic resistance (afterload) translates to increased work for the shock who have an elevated left ventricular fi lling pressure, heart and offsets any advantage obtained by increasing the often manifested by elevated jugular venous distention (JVD), blood pressure. In fact, imprudent administration of norepi- but who are not remarkably hypotensive (systolic B/P greater nephrine can lead to acute myocardial infarction in patients than 90 mmHg). These patients, on the border of severe car- with pre-existing coronary artery disease. diogenic shock, often benefi t from a combination of dobu- tamine (to maintain blood pressure) and dopamine at renal doses (for diuresis). As an added bonus, dopamine and dobutamine are com- Street Smart patible and may be infused together via the same intravenous access. This approach is often preferable, especially in patients Monoamine oxidase oxidizes catecholamines, with potential for hypokalemia, because of a decreased risk like dopamine and norepinephrine, into inactive of tachydysrhythmia. metabolites. Monoamine oxidase inhibitors (MAO Norepinephrine inhibitors), a class of antidepressant medications, Norepinephrine, in contrast to dobutamine, has a high affi nity prevents the breakdown of these catecholamines. for alpha-adrenergic receptors. Norepinephrine is a power- Routine doses of dopamine administered to a patient ful peripheral vasoconstrictor which is effective in treating who has prescribed MAO inhibitors can result in serum cardiovascular collapse secondary to distributive shock (e.g., advanced septic shock). dopamine levels that are increased ten-fold and lead The use of norepinephrine in patients in cardiogenic to acute hypertensive crisis. shock is questionable, as the increased peripheral vascular 674 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Two of the most common chief complaints of patients are chest pain and shortness of breath. By understanding the underlying cardiopulmonary physiology and pathophysiology, Paramedics can establish effective therapeutic interventions earlier in the course of the patient’s illness. Early intervention can translate directly into decreased morbidity and mortality. Key Points: • The central nervous system consists of the brain • Blocking nicotinic receptors causes paralysis. and spinal cord. Depolarizing agents cause fasciculations before • paralysis while non-depolarizing agents lead The peripheral nervous system consists of the directly to paralysis. cranial, nervous, and spinal nerves. • • Adrenergic agents directly or indirectly stimulate a The autonomic nervous system is that portion of sympathetic response. the peripheral system that controls involuntary functions. • Adrenergic blockers would prevent a sympathetic • response. The autonomic nervous system consists of two branches: the sympathetic division, which serves • Alpha-adrenergic agents or blockers primarily to accelerate organs, and the parasympathetic affect the vessels. division, which controls vegetative functions. • Beta-adrenergic agents or blockers affect the heart • The vagus nerve is the primary parasympathetic or lungs. nerve. • Drugs used to treat pulmonary diseases usually • Messengers which relay signals from nerve to organ target one of the three S’s: spasms, swelling, or are called neurotransmitters. secretions. • Neurotransmitters attach to a receptor. • Beta-adrenergic agonists, xanthine derivatives, and • cholinergic antagonists prevent or reduce spasms. Agonist drugs increase the neurotransmitters’ ability to stimulate the receptor. • Corticosteroids, leukotriene antagonists, and mast • cell inhibitors reduce swelling. Antagonist drugs block stimulation of the receptor. • • Mucolytics liquefy mucus. Parasympathetic receptors are classifi ed as cholinergic (responding to acetylcholine), • Drugs used to treat coronary artery disease usually i.e., muscarinic, or nicotinic receptors. target vessels, platelets, coagulation cascade, or • lipids. Muscarinic receptors are found in organs, whereas nicotinic receptors are located in the adrenal • Antilipidemic drugs either prevent absorption of medulla, CNS, and skeletal muscles. cholesterol, sequester in the bile for elimination, • or prevent the liver from making cholesterol. Cholinergic agents are agonists which stimulate a parasympathetic response. • Anticoagulant drugs interfere in the clotting • cascade, preventing the formation of a fi brin clot. Anticholinergic agents would slow or stop parasympathetic responses. Pharmacological Interventions for Cardiopulmonary Emergencies 675 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. • Antiplatelet drugs alter platelet membranes, • Class V drugs have miscellaneous effects and include preventing aggregation, adherence, and the cardiac glycoside digitalis and the antiarrythmic vasoconstriction. adenosine. • Fibrinolytics disassemble the fi brin clot. • An indirectly acting drug which allows the heart • rate to increase is the cholinergic blocker called Nitrates dilate the venous system (reducing blood atropine. return to the heart), dilate the arterial system (reducing workload of the heart), and may dilate • When underperfused, the kidneys release a coronary vessels (increasing blood fl ow to the substance called renin. Through several steps, renin myocardium). is converted to angiotensin, which affects vessel • dilation and the movement of water and sodium Dysrhythmias are an alteration in the heart’s rate or from the kidney. rhythm. Not all dysrhythmias require treatment. • • The conversion of renin to angiotensin requires an The goal of dysrhythmic treatment is to alleviate enzyme. Inhibiting the enzyme (with an angiotensin- symptoms. Antidysrhythmic drugs can cause other converting enzyme inhibitor or ACE inhibitor) dysrhythmias and are proarrythmic. prevents an increase in blood pressure through • Drugs used to treat dysrhythmias affect the constriction and increased volume. transition of the ionic channels from resting to • Diuretics affect the release of water and other ions open/active or inactive. from the kidney. Depending upon the exact location • The cations of the heart’s action potential are of action, more or less water is released and sodium, potassium, and calcium. The Vaughn- potassium may be excreted or retained. Williams classifi cation system divides drugs • Vasodilators usually cause dilation of the venous according to the ion affected. side and reduction of blood return to the heart. • Class I drugs affect sodium infl ux. Class I drugs are Those that cause arterial dilation decrease diastolic subcategorized as IA, IB, or IC, depending upon pressure, peripheral vascular resistance, and where in the sodium infl ux stage they act. afterload. • Class II drugs are beta-blockers. They affect the • Digitalis, a cardiac glycoside, slows electrical chemical which opens the calcium channels. They conduction and increases the strength of also reduce myocardial infarct size by decreasing contraction. It is both an antidysrhythmic and a heart rate and thus allow a longer diastole and treatment for heart failure. increased coronary blood fl ow. By also dilating • Digitalis has a narrow therapeutic range and can peripheral vessels, they decrease myocardial oxygen rapidly lead to toxicity. demand. • • Catecholamines act with sympathetic receptors. Class III drugs block potassium movement from the They are indicated for vascular support. cell, lengthening the period of time in which the cell cannot respond to another stimulus. • Class IV drugs block the movement of calcium into heart cells, reducing the rate of depolarization or the mechanical initiation of contraction. 676 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Review Questions: 1. Differentiate the central nervous system, 8. Defi ne agonists and antagonists as they relate to peripheral nervous system, and autonomic receptors. nervous system from each other based on location, 9. Which classes of drugs reduce spasms associated components, and general action in the body. with pulmonary disease? 2. How |
are the actions of the sympathetic division 10. Which classes of drugs reduce swelling different from those of the parasympathetic associated with pulmonary disease? division? 11. From which class of drugs do “rescue drugs” for 3. Defi ne a neurotransmitter and describe how pulmonary disease come? it works. 12. List the fi ve main classifi cations of the Vaughn- 4. Which division of the autonomic nervous Williams system. system has cholinergic receptors? 13. What condition(s) are treated by drugs of the 5. Name the types of adrenergic receptors. Vaughn-Williams system? 6. Which adrenergic receptors primarily affect 14. How do ACE inhibitors work? vessels? 15. Describe the concern regarding the 7. Which cholinergic receptors primarily affect administration of digitalis preparations. skeletal muscles? Case Study Questions: Please refer to the Case Study at the beginning of 2. In what ways do pharmacies try to prevent the chapter and answer the questions below: patients from taking similar medications 1. Using the information in this chapter, describe prescribed by different physicians? at least fi ve ways in which medications prescribed 3. How do Paramedics assist in educating their for Mrs. Fein’s blood pressure control and patients about medication use? dysrhythmias can cause her complaints of fatigue and nearly fainting. References: 1. Greenblatt S. A History of Neurosurgery. New York: American 5. Arun CP. Fight or fl ight, forbearance and fortitude: the spectrum Association of Neurological Surgery; 1997. of actions of the catecholamines and their cousins. Ann N Y Acad 2. Shields RW, Jr. Functional anatomy of the autonomic nervous Sci, 2004;1018:137–140. system. J Clin Neurophysiol. 1993;10(1):2–13. 6. Wortsman J. Role of epinephrine in acute stress. Endocrinol 3. Hilz MJ, Dutsch M. Quantitative studies of autonomic function. 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KEY CONCEPTS: Upon completion of this chapter, it is expected that the reader will understand these following concepts: • Mechanism of action for common medications • Prehospital drug interventions • Recognition of expected actions and other actions of patient and prehospital medications Case Study: The ambulance squad received a call for a 35-year-old man complaining of severe back pain. En route to the call, one Paramedic said to his partner that this guy was probably just a drug seeker. His partner replied, “Maybe, but we need a lot more information. Many medical conditions cause severe pain and I’d want someone to care for me and reduce my pain if possible.” 682 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Pharmacological Therapeutics for Medical Emergencies 683 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. OVERVIEW Paramedics are expected to treat an enormous variety of diseases in the fi eld. Considering the lack of information normally known about a patient in the fi eld, the enormity of the EMS task becomes even more daunting. Nevertheless, using a limited pharmacy, Paramedics persist in trying to accomplish their missions of care and support to the sick and injured. The following drug review supplies the Paramedic with information about drugs that are commonly prescribed to patients, as well as those drugs that a Paramedic might use to care for that patient. The development and distribution of new drugs, and the use of old drugs/ technologies for new applications, makes it impractical to discuss each drug individually. Instead, the general action of each classifi cation of drug (i.e., its pharmacotherapeutics), including its pharmacodynamics and pharmacokinetics, is discussed. The Paramedic is well advised to consult the most recent and up-to-date drug reference regarding a specifi c drug before administering any medicine. Drugs That Affect The entire brain, as well as the spinal cord, is surrounded by the fl uid-producing meninges. the Central Nervous System The central nervous system consists of the brain and the Blood-Brain Barrier spinal cord. Although the brain is considered the seat of Capillaries in the body have small gaps, called slit junctions consciousness (that uniquely human condition), it has not that permit hormones, enzymes, and drugs to move into the always been thought of that way. Aristotle viewed the brain interstitial space. Capillaries in the brain are distinctive in that as just an elaborate cooling apparatus for the blood. It took they have nearly impenetrable tight slit junctions.2 Reinforc- centuries to dispel that myth. Today, the importance of ing these tight junctions are cells called astrocytes. These two the brain is undisputed. The brain is so important that the factors combine to make the brain nearly impassable to most prime directive for EMS could be “to keep the brain alive drugs, permitting only lipid-soluble drugs (like diazepam) to at all costs!” enter the brain and preventing ionized (polar) drugs that are The brain that controls the central nervous system is dissolved in solution from entering into the brain. actually not one brain but three brains working together. The fi rst brain, the so-called primitive brain, is the brainstem, which is made up of the midbrain, pons, and the medulla Central Nervous System Sedatives oblongata. Vital life functions, such as breathing and heart A state of reduced central nervous system activity (i.e., seda- rate, are controlled in the brainstem.1 The brainstem also tion) is desirable for a number of medical reasons. Exhausted contains the reticular activating system (RAS), a complex patients (e.g., insomniacs) need sleep and literally dozens network of interconnected refl exes that maintain wakeful- of drugs can induce sleep. In another case, a fear-induced ness. The next brain is the cerebellum. The cerebellum is anxiety attack can lead to acute myocardial infarction (AMI) responsible for balance (equilibrium) and muscular coordi- in some patients. Perhaps the earliest CNS depressant used nation, hence its title “the athletic brain.” The last brain, the medicinally was alcohol. While alcohol is effective as a CNS cerebrum, is perhaps the most important to a person’s sense depressant, it has many undesirable qualities that limit its of being. The cerebrum is responsible for a person’s emo- medical use. For this reason, and for a wide variety of clinical tions, memories, and speech, as well as reasoning, judgment, situations, other central nervous system depressants have and creativity. The cerebrum is actually a hollow sphere. The been created. outside, called the cerebral cortex (“cortex” is a Latin word These CNS depressants have some common effects. At meaning “bark”), contains the gray matter. The inside of the low doses, many of these drugs are sedatives. They cause cerebrum contains white matter, myelinated fi bers that con- relaxation, lessened irritability, and decreased excitability. nect with different sections of the brain and the spinal cord. At higher doses, many of these CNS depressants induce a 684 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time |
if subsequent rights restrictions require it. hypnotic state, a sleep-producing effect. Many of these CNS Benzodiazepines depressants also are anxiolytics, reducing apprehension, fear, Benzodiazepines were introduced in the 1960s and largely and anxiety. While anxiety is normal, and is in fact a healthy seen as a replacement for barbiturates. Compared to barbi- response to stress because it encourages action, excessive turates, benzodiazepines are relatively safe, the lethal dose anxiety is unhealthy. Excessive anxiety can mentally paralyze being one-thousand times greater than the therapeutic dose a person and interfere with his ability to perform the activities (i.e., it has a large therapeutic index). Benzodiazepines were of daily living (ADL). also reported to have fewer side effects and less of an abuse Barbiturates potential than barbiturates. Like barbiturates, benzodiazepines can be divided into Barbiturates, such as phenobarbital, have been used extensively three groups according to the duration of their action. Long- in the recent past as a CNS depressant. While barbiturates have acting benzodiazepines include diazepam, the classic anti- been largely replaced by safer benzodiazepines, barbiturates convulsive medication. Intermediate-acting benzodiazepines are still useful in certain clinical situations. As a class, barbitu- (e.g., lorazepam) are useful in treating acute alcohol with- rates can be divided into three groups according to the duration drawal (delirium tremens). Short-acting benzodiazepines of action: long-acting, short-acting, and ultra-short-acting.3 (e.g., midazolam) are useful in treating neurological medical Long-acting barbiturates, such as phenobarbital, are fre- emergencies such as status epilepticus, a condition of con- quently used for seizure prophylaxis, the prevention of recur- tinuous convulsions. At present, there are over 20 different rent seizures. The intended pharmaceutical effect of long-acting benzodiazepine formulations available on the market. barbiturates can last for as long as 10 to 12 hours, making them ideal for twice daily (BID) administration. Mechanism of Action Short-acting barbiturates, such as pentobarbital or seco- barbital, produce an onset of action within 10 to 15 minutes Benzodiazepines work indirectly by occupying a receptor and can last up to four hours. This rapid onset of action makes next to a receptor. GABA receptors on cell membranes con- them ideal as presurgical anxiolytics in preparation for the trol the fl ow of the chloride (Cl-) ion in and out of the cell via induction of anesthesia. a chloride channel. The amount inside a cell, in milliequiva- Ultra-short-acting barbiturates, such as thiopental, create lents (mEq) of chloride, affects its resting membrane poten- a sedative/hypnotic effect, depending on the dose, within sec- tial. Benzodiazepine occupies a receptor next to the GABA onds. This rapid speed of onset of action makes these drugs receptor (now called the benzodiazepine receptor). The ben- excellent for use in emergency situations where time is of the zodiazepine receptor, when occupied by a benzodiazepine, essence and rapid induction of anesthesia is mandatory. stimulates the GABA receptor to hold onto GABA longer when it is stimulated. The result is prolonged GABA stimula- Mechanism of Action tion, which in turn increases the amount of chloride (Cl-) in The mechanism of action of all barbiturates is the same: Bar- the cell.2The cell, now loaded with chloride, is hyperpolar- biturates interfere with the transfer of sodium and potassium ized and therefore much more diffi cult to depolarize. across the cell membrane. Inhibition of the sodium-potassium Indications ionic transfer blunts the action potential of muscle cells gen- erally and of nerve cells particularly. This nonselective mech- When benzodiazepines hyperpolarize cells, they are in effect anism of action means barbiturates impact the entire central raising the action potential of those cells. Within the cen- nervous system. At higher doses, barbiturates induce anesthe- tral nervous system, raising the action potential also raises sia by this action, in effect paralyzing the brain at the cellular the seizure threshold. Seizures are the result of spontaneous level. At toxic levels, barbiturates suppress chemoreceptors depolarization of the neurons in the brain. Seizures are analo- that are sensing carbon dioxide and oxygen levels, inducing gous to ventricular fi brillation in the heart, a chaotic fi ring respiratory depression. If unresolved, toxic levels of barbitu- of cells without purpose. Raising the action potential of the rates can lead to complete coma and respiratory arrest. heart raises the ventricular fi brillatory threshold. The heart is thus less likely to go into ventricular fi brillation. Raising the action potential within the brain raises the seizure thresh- old; thus, the brain is less likely to seize. This mechanism of action makes benzodiazepines very desirable as anticonvul- Street Smart sive medication, especially in cases of life-threatening con- tinuous seizures termed “status epilepticus.” While barbiturates are powerful anesthetic agents, Benzodiazepines also inhibit the neurons within the they do not produce pain relief. Concomitant limbic system, the seat of human emotions. Benzodiazepine receptors are more concentrated in the limbic system than administration of pain medications is required during anywhere else in the brain. The inhibition of the limbic sys- special procedures. tem also makes benzodiazepines effective as a tranquilizer.4 The combination of tranquilizer effect and anxiolytic effect Pharmacological Therapeutics for Medical Emergencies 685 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. makes benzodiazepines desirable as a premedication before Withdrawal from Central Nervous painful procedures such as elective cardioversion. However, System Depressants benzodiazepines are not pain relievers. Analgesic, concomi- tant administration of pain medication may be indicated. Withdrawal of all CNS depressants can result in a dramatic Benzodiazepines are also useful in treating muscle spasms rebound within the central nervous system. The common (secondary to neuromuscular disease) and spasticity of mus- symptoms of depressant withdrawal include anxiety, agita- cles from traumatic paraplegia or cerebral palsy. By inhibiting tion, restlessness, and symptoms of overstimulation of the neural control of muscles at the level of the spinal cord, spasms sympathetic nervous system, such as tachycardia and hyper- can be prevented and patient management made easier. tension. Onset of symptoms is usually patient and drug spe- cifi c. For example, symptoms of alcohol withdrawal, called the delirium tremens, can occur in as little as 12 hours after the patient has taken his or her last drink. Street Smart Untreated depressant withdrawal can be life-threatening. Delirium tremens, for example, only occurs in about 5% of All CNS depressants, including alcohol, barbiturates, the patients in ethyl alcohol withdrawal. Yet, if left untreated, it can have up to a 35% mortality rate. Alcohol withdrawal and benzodiazepines, cause a loss of motor dexterity. frequently presents as a seizure, a frequent comorbid condi- Operation of complex machines, such as automobiles tion of alcoholism.7 Treatment usually includes reintroduc- and ambulances, should be avoided while under the tion of a CNS depressant, such as Librium, from which the infl uence of these medications. patient is then carefully weaned off. Anesthesia While Paramedics rarely, if ever, perform general anesthesia Benzodiazepine Toxicity while in the fi eld, they are occasionally witness to anesthesia At high levels, benzodiazepines can produce drowsiness and in the emergency department, critical care units, or operating respiratory depression. Fortunately, the therapeutic index for room. An understanding of the fundamentals of anesthesia benzodiazepines is so high that true overdose is relatively can potentially improve the Paramedics’ experience as well rare. However, that is not the case when benzodiazepines as improve interdisciplinary communication between anes- are mixed with other CNS depressants, such as alcohol. thetists and EMS. These substances intensify, or potentiate, the effects of the Anesthesia, by defi nition, is the lack of sensation, pain- benzodiazepines. In those cases, the incidence of respiratory ful or otherwise. Anesthetic drugs primarily induce anesthe- depression/arrest becomes much higher. This fact is not lost sia by interfering with or blocking nerve conduction. Local on the public, some of whom use the combination of benzo- anesthesia, as the name implies, means that local nerves are diazepines and alcohol to cause a peaceful suicide. incapacitated (i.e., left to feel numb). General anesthesia is The metabolism of benzodiazepines occurs in the liver, much more complex. With the brain incapacitated, the patient where even the metabolic by-products are often still pharma- becomes unconscious and general relaxation of muscles and cologically active. The elderly, and others who have decreased loss of protective refl exes occurs. liver function, may react more profoundly to the administra- Incremental doses of anesthetic medications can result tion of benzodiazepines. For example, diazepam, which nor- in several levels or degrees of anesthesia, with the patient mally has a half-life of 24 hours, can remain active in the becoming deeper under the infl uence of the anesthetic bloodstream of an elderly patient for 72 hours. with each successive dose or medication. The fi rst state The antidote for benzodiazepine overdose is fl umazenil. of anesthesia is called analgesia. Analgesia is a condition Flumazenil is a benzodiazepine receptor blocker. It is effec- where the patient does not feel pain, yet remains conscious. tive in blocking the effects of all benzodiazepines but is not More importantly, the patient retains his or her protec- effective against narcotics. Flumazenil has a half-life that tive refl exes. This level of anesthesia is also referred to as is shorter than most intermediate-acting benzodiazepines. conscious sedation. The second state of anesthesia is called Therefore, Paramedics must be alert to the chance of rebound excitement. At this level of anesthesia, the patient may be respiratory depression and be prepared to administer a repeat combative, delirious, and evidence irregular breathing. dose of fl umazenil every hour.5 Paramedics must also be cau- Vomiting and/or incontinence is also common in this stage. tious using fl umazenil as it may induce acute benzodiazepine The third state of anesthesia is surgical anesthesia. The withdrawal (discussed shortly) and eliminate the protection third state is further divided into four planes. These planes from seizures created by the prophylactic administration of are varying levels of unconsciousness. Anesthesiologists benzodiazepines.6 The resultant “breakthrough” seizures can are masters at the individualization of anesthetic doses to develop into life-threatening status epilepticus. For this rea- produce the exact plane of surgical anesthesia desired for son, fl umazenil is not recommended for use in altered mental the specifi c procedure being performed. By monitoring status from unknown ingestions. respirations, which return to normal after excitement, and 686 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. refl exes, such as pupil size, the anesthesiologist can lead the To administer nitrous oxide. the patient is usually asked patient to near-coma. to hold a mask that is fl owing with a mixture of oxygen (mini- As the patient becomes more deeply anesthetized, he mum 20%) and nitrous oxide. When the patient can no longer will lose protective refl exes in a head-to-toe (cephalocau- hold the mask alone, the administration is completed. dal) direction. The fi rst refl ex lost is the blink refl ex. When the eyelashes are brushed gently, the eyelid closes (blinks); Intravenous Anesthesia hence, the blink refl ex. Level one of surgical anesthesia Agents used in intravenous anesthesia include the ultra- starts with the loss of consciousness and loss of the blink short-acting barbiturates. Thiopental is particularly useful in refl ex. Conversely, when a patient is brought out of anes- cases where there is increased intracranial pressure (ICP) because thesia, the last refl ex to return before consciousness is the it produces an actual decrease in ICP pressure (a neuroprotective blink refl ex. benefi t). The onset of action of these agents is usually between The fourth and last state of anesthesia is medullary 60 and 90 seconds and the duration of the action is short. paralysis. With the vital life centers in the medulla oblongata Another class of agents used in intravenous anesthesia are paralyzed, the medication is |
now, by defi nition, toxic. Car- the short-acting benzodiazepines. Benzodiazepines like lora- diopulmonary arrest ensues unless the medication is reduced zepam are lipid-soluble and readily cross the blood-brain bar- or withdrawn. rier. While, as a class, benzodiazepines tend to have a slower onset of action than the barbiturates, they have an amnesic effect. This makes them the drug of choice for painful pro- cedures, like elective cardioversion. Certain narcotic agents Street Smart (e.g., fentanyl) are also used during intravenous anesthesia. A discussion of fentanyl follows in the section on narcotics. While the patient may appear unconscious, the last sense to be lost is the sense of hearing. Patients have Balanced Anesthesia reported, verbatim, statements made about them No single anesthetic agent is completely effective or even while they were assumed to be unconscious.8−11 desirable for anesthesia. Individually, many anesthetic agents produce such signifi cant side effects as hypotension, cardiac irritability, and nausea with vomiting. Therefore, a combina- tion of anesthetic agents—some inhaled and some injected Inhaled Anesthetics intravenously—are often used to minimize these side effects General anesthetics may be either inhaled or injected intrave- in an approach called balanced anesthesia. nously. Anesthetists prefer inhaled anesthetic agents because In many cases, premedication with a CNS depressant, these drugs can be precisely titrated to the exact level of anes- like barbiturates or benzodiazepines, is performed fi rst. Use thesia desired. of these CNS depressants as a premedication before the intro- Most anesthetics are not gasses, with the exception of duction of anesthesia (pre-induction agents) can decrease nitrous oxide. Inhaled anesthetics, like halothane or iso- the incidence of fear or panic (anxiolysis) or combativeness fl urane, are volatile liquids that off-gas vapors, which are (sedation) in the patient. inhaled by the patient. The use of these volatile liquids Atropine is another frequently used pre-induction agent. requires complex apparatus and monitoring equipment that Atropine, a parasympathetic blocker, dries the airways and would make this procedure all but impossible to routinely prevents secretions, thus making intubation easier and aspi- perform in the fi eld. ration less likely.16,17 Another frequently used pre-induction The only inhaled anesthetic used in the prehospital agent is lidocaine. Lidocaine blunts sudden raises in intracra- environment is nitrous oxide. Nitrous oxide (N O) received nial pressure (ICP) that often accompany manipulation of the 2 airway and intubation.18–20 notoriety in the 1900s as a form of entertainment in the par- lor and was dubbed laughing gas for its most notable side The most common—and the most problematic— effect. Properly administered N O is a potent analgesic as complication of anesthesia is nausea with vomiting. Major 2 well as an anesthetic that can be safely given in the fi eld.12–15 tranquilizers (neuroleptics) have a noteworthy side effect— While ALS providers are concerned about the progression they prevent nausea. Drugs like promethazine and chlorpro- of anesthetics from analgesia to surgical anesthesia, with mazine are used as both a sedative and as an antiemetic. the concomitant problems that can occur, nitrous oxide can- not produce surgical anesthesia. This quality makes nitrous Procedural Sedation oxide even more desirable for the fi eld. Add to that attribute Procedural sedation is a technique used by Paramedics to the fact that nitrous oxide does not depress respirations nor facilitate performance of technically diffi cult procedures increase cerebral blood fl ow in patients with potential head (such as trauma intubation) or painful procedures (such as injuries, and nitrous oxide could be very useful in the out-of- elective cardioversion). The goal of procedural sedation is hospital setting. to minimally depress the patient’s consciousness, without Pharmacological Therapeutics for Medical Emergencies 687 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. loss of protective refl exes. Procedural sedation must also be Giving even more support to the argument that Para- performed with a minimum of alteration of vital signs. The medics can and should administer pain medications is the use of procedural sedation can improve patient cooperation Paramedics’ ability to administer an antagonist medication. with painful or diffi cult procedures while ensuring safety and Paramedics who can administer narcotics can also adminis- patient well-being. For these reasons, Paramedics are seeing ter naloxone (the antagonist to narcotics) and thereby reverse a greater use of procedural sedation in the fi eld. any untoward effects. Thus, the availability of an antidote, Procedural sedation is the fi rst state of anesthesia. As plus the reality of pain management in these selected popula- such, Paramedics must keep in mind that the patient can eas- tions, and the ability to manage the consequences, combine ily slip into the next state of anesthesia and lose their ability to provide Paramedics an unparalleled safety margin. to protect their airway or become apneic. Therefore, all pro- viders utilizing procedural sedation techniques must be pre- The Experience of Pain pared to protect the airway as well as treat any hemodynamic Perhaps the more central issue is the Paramedic’s understand- instability that might occur as a result of conscious sedation. ing of the concept of pain. A person’s interpretation of pain It goes without saying that the patient undergoing procedural is based, in part, upon cultural determinants and, in part, by a sedation must be continuously monitored. A more thorough personal pain history. The interpretation of pain may be gen- discussion of procedural sedation is contained in Chapter 24. der biased; for example, some feel men should be tough and not complain. The interpretation of pain may be age-biased, Pain Management for example; the misconception that the elderly can tolerate pain better. The interpretation of pain is based in large part Pain is the most common reason people call EMS. Yet, Para- upon the patient’s own experiences with pain. Each patient medics are reluctant to administer pain medications. This is has a pain history which colors his interpretation of pain and an unreasonable response, considering the large number of how he perceives others’ pain. safe pain medications available.21–23 Paramedics’ unwilling- Therefore, when assessing someone else’s pain, all ness to use medications to ameliorate pain is, in part, due to healthcare professionals tend to look at that person’s pain lack of knowledge regarding the actions of these drugs. from their own perspective. This approach, while understand- The bombardment that the public, healthcare profession- able, is fl awed. Pain is a personal experience. Therefore, the als, and Paramedics have received about the dangers of drug effectiveness of pain management can only be interpreted addiction has placed a needless fear in the minds of many. by the person affected. Paramedics must develop tools to Yet, this fear continues, even though multiple studies have assess pain and trust the patient to be honest. That honesty demonstrated that drug addiction to properly prescribed med- will be rewarded as the patient–provider relationship is ications is rare.24 The risks of addiction to single doses of pain strengthened. medication administered in the fi eld for obvious and neces- sary reasons is remote at best. Other Paramedics are reluctant to administer pain medi- Concepts in Pain cation for fear of inducing respiratory depression. This fear Pain is both the cognitive awareness of the stimulus as well is unfounded for two reasons. First, with proper assessment, as the body’s physiological response to the stimulus. Under- including dose adjustments based on condition, careful titra- standing the physiological response will allow Paramedics to tion of the analgesic, and vigilant monitoring of the respi- lessen the pain by interfering with the process. ratory system, the incidence of respiratory depression is Pain can be divided into acute and chronic pain. Chronic low. More importantly, if respiratory depression does occur, pain is a persistent or reoccurring discomfort seen in long- Paramedics are highly trained to properly respond. This fear term conditions (e.g., arthritis). Chronic pain, while impor- represents a fundamental fl aw in the Paramedics’ understand- tant, is not germane to the topic of EMS. Acute pain, on the ing of pain management. While a dose of 4 milligrams of other hand, is a constant in the day-to-day provision of EMS. morphine, for example, administered intravenously might Acute pain occurs suddenly and is preceded by some identifi - induce respiratory depression in 5 to 10 minutes, the same able event. Pain is a warning to the patient, the body’s way dose in a person with moderate burns, a fractured long bone, of telling the patient that something has changed. The pain or advanced cancer would not. In fact, those patients may usually persists until the situation is corrected. require 5 to 10 times or more than that amount of morphine Acute pain can arise from the internal organs, such as the to obtain relief from pain and still not be at risk for respira- heart, and is usually described as a pressure-like, dull, or aching. tory depression. In short, a patient who is truly in pain should This organ pain is termed visceral pain. Visceral pain is poorly and can receive pain medication for pain control. Paramedics localized and often is transmitted to other parts of the body, via should not be overly concerned about the risk of respiratory common nerve pathways. This is called referred pain. depression. However, this understanding does not relieve the Acute pain often arises from the skin, ligaments, mus- Paramedic from needing to be prepared in case respiratory cle, fascia, bones, or joints. This type of pain (somatic depression should occur. pain) is often described as sharp or burning. One important 688 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. difference between visceral pain and somatic pain is that somatic pain can be localized to a specifi c area. Street Smart Every person has a tolerance to pain. At its lowest level, one person might perceive pain while another might not. This is the pain threshold, that amount of stimulus required to The perception of pain is partly psychogenic. Use of elicit a pain response. the term “pain” by a Paramedic tends to establish a If the person has multiple injuries, and therefore multiple fi xed expectation in the patient’s mind. Alternatively, painful experiences, she may not perceive the dull visceral referring to pain as a discomfort tends to induce pain of a heart attack, for example, over the intense pain of a fractured femur. When a pain (often dull visceral pain) is thoughtfulness on the part of the patient and is overshadowed by another more intense pain from another generally less infl ammatory. injury, it is called a distracting injury. The fractured femur in this case may be a distracting injury and takes perceptual dominance over the chest pain. The concept of perceptual Regardless of the mechanism of action, every analgesic can dominance makes it more diffi cult to accurately assess a mask the cause of the symptom. Simply ignoring the pain patient’s condition. does not stop the damage that will occur. Before, during, and Physiology of Pain after pain management, Paramedics must assess and deter- mine the underlying cause of the problem. An injury to the skin will stimulate pain receptors in the der- mis. These pain receptors, called nociceptors, respond to Opiates chemical, mechanical, or thermal stimulus and are not evenly Opium, isolated from the Poppy plant, may have been the fi rst distributed across the body. Once stimulated, the nociceptors’ pain medication used by man. Over the span of time, physi- signal is transmitted either quickly over myelinated A fi bers cians and laypersons alike have sought better, stronger, more (sharp) to the spinal cord or more slowly over unmyelinated effective opium. This untiring pursuit has resulted in over a C fi bers (dull |
or burning) to the thalamus. Refl ex arcs occur dozen opiate and opiate-like medications (Table 31-1). over A fi bers, the speed of which permits an automatic with- drawal from the stimulus before the brain even has a chance Mechanism of Action to interpret the painful stimuli and respond. The pain sen- All opiates work by a similar mechanism, coupling with opioid sation is now transmitted to the brain via either the neospi- receptors in the central nervous system and the gastrointestinal nothalamic tract (acute pain) or the paleospinothalamic tract system to become an opiate agonist. The stimulation of these (dull pain) in the spinal cord. opioid receptors decreases the cell membrane’s permeability After arriving at the post-central gyrus in the midbrain, to sodium.25 The resultant increase in intracellular sodium the signal is transferred to the cortex (acute pain) or the limbic hyperpolarizes the cell, decreases the action potential, and system (dull pain) for interpretation and response. The body’s slows conduction by decreasing nerve cell depolarization. response to pain is two-fold: regulation of infl ammation and neuromodulation of the pain. Infl ammation is the body’s Indications response to an injury. Activated by the pain, prostaglandins act as infl ammatory regulators, affecting blood vessel tone, Five different opioid receptors have been identifi ed and platelet aggregation, and muscle spasm in the injured area. labeled with the Greek letters Mu, Kappa, Sigma, Delta, and Neuromodulators are substances that inhibit the trans- Epsilon. Stimulating these opioid receptors causes a variety mission of painful sensations to the brain and spinal cord. of effects. Stimulation of the opioid receptors in the gastroin- Examples of neuromodulators are endorphins. Endorphins testinal system decreases gastric motility (slowed peristalsis) attach to opiate receptors on the neuron which in turn inhibit as well as intestinal secretions. Disease-induced diarrhea, a neural activity. Naturally, opiates also occupy these opiate common malady, can be treated very effectively with small receptors, enhancing the activity of the endorphins. High lev- amounts of opioids. A few drops of tincture of opium can els of circulating neurotransmitters—such as norepinephrine stop diarrhea and produce constipation.26,,27 Paregoric, a cam- and serotonin in the brain caused by stress, acupuncture, and phorated tincture of opium, is an old remedy used for centu- excessive physical exertion—interfere with the effectiveness ries to treat diarrhea. It is still used to treat life-threatening of endorphins and opiates alike. diarrhea in infants and neonates. Stimulating the Mu, Kappa, and Sigma opioid receptors Analgesics along the cortex–brainstem–spinal cord axis produces other desirable, as well as undesirable, effects. Some opiates, in The class of drugs that relieve pain are called analgesics. small quantities, function as a cough suppressant (e.g., an Analgesics work by inhibiting the synthesis or release of pros- antitussive). Prescription antitussive cold medications occa- taglandins or stimulating opiate receptors (opiate agonists). sionally include the opiate codeine. Pharmacological Therapeutics for Medical Emergencies 689 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Table 31-1 Opiates Drug Method Onset of Action Peak Effect Duration Codeine PO 10 to 31 min 31 to 60 min 4 hours Hydrocodone PO 10 to 31 min 31 to 60 min 4 hours Hydromorphone IM 15 min 31 to 60 min 4 hours IV 10 to 15 min 15 to 31 min 2 hours Meperidine IM 10 to 15 min 31 to 50 min 3 hours IV 1 min 5 to 7 min 3 hours Methadone IM 10 to 20 min 60 to 120 min 4 hours Morphine IM 10 to 31 min 31 to 60 min 4 hours IV 1 min 20 min 4 hours Oxymorphone IM 10 to 15 min 31 to 90 min 4 hours IV 5 to 10 min 15 to 31 min 4 hours Propoxyphene PO 15 to 60 min 120 min 4 hours Opiates in larger doses impact the brainstem and pro- Opiates, particularly morphine, are also widely used to duce constricted pinpoint pupils (miosis) and respiratory treat the chest pain (angina pectoris) of an acute myocardial depression. Even moderate doses of opiates can induce infarction (AMI). The administration of morphine not only some degree of respiratory depression. In some cases, this alleviates pain—relaxing the patient and reducing circulating slower and deeper respiration is desirable, improving the epinephrine levels and subsequent arterial constriction—but clearance of carbon dioxide from the lungs and increasing it also decreases the heart’s work (MvO2) by creating periph- oxygenation of the blood. In slightly higher doses, slowed eral vasodilatation. This, in turn, reduces preload. Both of respirations paradoxically result in increased carbon these effects of morphine are accomplished without impact- dioxide retention and hypoxia. The result of unattended ing heart rate signifi cantly, making it an acceptable analgesic opiate overdose can be profound respiratory depression for acute myocardial infarction pain, though there is some leading to acute respiratory acidosis and cardiac arrest. controversary about the use of morphine for patients with Therefore, patients must be carefully monitored while suspected acute myocardial infarction. receiving opiates. The less desirable hallucinogenic effects of opiates, the Administration narcotic effect, is thought to be the result of stimulation of Morphine is the archetypical opiate. The pain-relieving abili- the sigma receptors located in the limbic system. This dream- ties of all subsequent medications are measured against it. producing quality of opiates is so well known that when When a dose of a new medication formulation has the same G erman pharmacist Friedrich Serturner extracted a plant ability to produce analgesia as 10 milligrams of morphine, it alkaloid from the opium of the Poppy plant, he named it Mor- is equianalgesic (i.e., equal to morphine). Morphine serves phium, after Morpheus, the Greek god of dreams.28 as the standard for comparison. Perhaps the most widely known benefi t of opiates is their The one of the fi rst morphine derivatives, produced by impact on pain. A potent analgesic agent, opiates affect the the German pharmaceutical company Bayer, was three times Mu, Kappa, and Delta receptors in the cerebral cortex, the more potent than morphine. It was called a heroic drug, or medial thalamus, and the spinal cord, altering the brain’s per- heroin, because of its powerful pain-relieving effects. ception of pain. Opiates, in effect, replace or augment the Fentanyl, another morphine derivative, is a remarkably body’s own neuromodulators (endophins) and lessen the sen- potent opiate agonist. It has a rapid onset of action as well as sation of pain. It should be noted that, even though the patient a short duration of action, and is 80 times more potent than still perceives the pain, opiates alter the patient’s perception morphine. The combination of these three qualities makes of the pain from being an unpleasant feeling to one that is fentanyl very useful in the out-of-hospital setting. less noxious. Knowing if a drug produces an equianalgesic effect simi- Such notables as Florence Nightingale used opiates for lar to morphine allows Paramedics to understand the impact of their therapeutic benefi t. During one of her own illnesses she an alternative analgesic compared to morphine (Table 31-2). stated that the “curious little new fangled operation of putting Weaker derivatives of opiates (such as propoxyphene, a opium under the skin” gave her relief from her discomfort. spinoff of methadone) are often combined with aspirin or acet- With the advent of the hypodermic needle in the 1950s, the aminophen for an enhanced effect. When combined, two anal- future of opiates was ensured. Opiates have become a main- gesics tend to potentiate one another, allowing for smaller doses stay analgesic.28 of each with the effect of giving a greater dose of one of them. 690 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Table 31-2 Dose Equivalency of Common retention, which in turn promotes cerebral vasodilatation and Opiates* subsequent increased intracranial pressure (ICP). Drug Dose Opiates also complicate the neurological examination of the patient with head injuries by producing miosis (pinpoint Morphine 10 mg pupils). As a general rule, opiate use is avoided in patients Methadone 10 mg with potential head injuries. Meperidine 75 mg Occasionally, opiates (particularly morphine) will cause the Codeine 60 mg release of histamine from mast cells. The result is anaphylactoid Hydromorphone 1.5 mg reaction complete with urticaria (hives), pruritus (itching), and Fentanyl 25 mcg facial edema but is not a true anaphylactic reaction. Treatment usually involves symptomatic care using Benadryl. *All medications are given IM. Transdermal Street Smart A number of transdermal administration methods have been created to administer opioids long-term. These transdermal Small amounts of codeine are found, along with systems often use a gelled alcohol as a vehicle; the body’s opium, in the common Poppy. They are both plant heat will melt the gel so that absorption will occur. Properly applied, the patch should be placed on smooth (hairless) and alkaloids that are chemically related. Therefore, it intact skin that is clear of soaps, oils, and lotions that might is not uncommon for a patient who has an allergy to impede absorption. Fevers (greater than 102°F) as well as codeine to have a cross-allergy to morphine. application of heating pads and electric blankets can increase the absorption of the opiate, leading to toxicity. Transdermal patches should also be removed and disposed of properly. Application of new patches without removal of used patches Synthetic Opiates may result in toxicity. Pharmacists continue to try to create synthetic opiates that do not have morphine’s undesirable effects. Methadone, a syn- Continuous Infusion thetic opiate, is equianalgesic to morphine and is useful in Unremitting pain from cancer, for example, requires a the treatment of narcotic addiction. It has many of the same constant administration of opiates in order to obtain, then effects as morphine. However, methadone’s single greatest sustain, the analgesia. Special patient-controlled analge- advantage may be that it can be taken orally, with the same sia (PCA) infusion pumps provide the patient with the effect, avoiding the dangers inherent in the use of needles. ability to control the amount of analgesia administered For this reason, and because methadone has a long half-life, without interruption. methadone is used in heroin detoxifi cation programs. Meperidine, another synthetic opiate, is an effective anal- Precautions gesic but requires large oral doses to become dose-equivalent While morphine has poor lipid solubility, making passage to morphine; 310 mg PO equals 75 mg IM, which is equian- across the blood-brain barrier less likely, other opiates (such algesic to 10 mg morphine. At these higher doses, meperi- as fentanyl) rapidly pass across both the blood-brain barrier dine has too many complications, including potentially toxic as well as the placental barrier. For this reason, caution must buildup of metabolites, to make it useful. Meperidine is used be advised when giving any opiate to ensure that it does not in smaller doses to treat moderate to mild pain. pass directly into an unborn infant, depressing the infant’s On the positive side, Meperidine is unlikely to cause mast respiratory drive. cells to release histamine and produce the pseudo- allergic Concerns related to adverse effects of opiate adminis- reaction seen with morphine. Meperidine also has an atropine- tration are directly related to the predictable effects of the like quality that causes pupil dilation, not constriction, which opiates in the body. The most notorious side effect of opi- is unlike the other opiates. ates is respiratory depression. Patients who have pre-existing pulmonary disease, such as emphysema or cor pulmonale, Opiate Antagonists are at risk for atypical respiratory depression and even risk Opiate antagonists can also induce acute opiate withdrawal. respiratory arrest with standard therapeutic doses. Cases of Opiate antagonists, like naloxone, dislodge opiates from the death have been attributed to |
opiates given in routine doses in opiate receptors. Undesired effects of opiate administration, these patient populations. such as respiratory depression, are immediately reversed, as Respiratory depression induced by opiates can also have well as the euphoric feeling that some addicts crave. Unsus- deleterious effects upon the patient with a traumatic brain pecting Paramedics have been assaulted by heroin addicts injury. Slowed respirations directly translate to carbon dioxide because the provider “ruined the high.” Pharmacological Therapeutics for Medical Emergencies 691 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Non-Opioid Analgesics Street Smart Federal and state restrictions on opiate use, including manda- tory triple prescriptions, have made acquiring opiates for pain The hallmark of opiate intoxication is the pinpoint relief diffi cult. Patients with minor to moderate pain often do pupils (miosis). The presence of miosis is suggestive not seek out medical assistance but rather self-treat and avoid the expense of medical care that does not include opiates. of high enough opiate levels to induce respiratory This way of thinking has led to a boom in nonprescription depression. Patients taking meperidine may not non-opioid analgesics sales. demonstrate miosis and the unsuspecting Paramedic This group of analgesics is also referred to as “non- might not be prepared for the respiratory depression narcotic,” leading to the assumption that these drugs are not addictive. While strictly correct (non-opioid analgesics gen- that ensues.29 erally do not lead to physiological addiction), many of these analgesics are habit-forming. Unsupervised chronic use of these drugs can lead to long-term complications, including organ-specifi c toxicity. Street Smart Salicylates Aspirin (ASA) is the prototypical non-opioid analgesic. Opiates, such as meperidine and morphine, can Brought to the market in 1897 by the Bayer pharmaceuti- have unpredictable interactions with MAO inhibitors. cal company,32 it remains the world’s most popular medica- Symptoms can include excitation, fever, seizures, tion. However, the central ingredient (salicylate) is found in many other over-the-counter drugs (e.g., Oil of Winter- and profound hypertension leading to hypertensive green). Salicylates (from the Latin salix, meaning willow) crisis.30 Opiates should be avoided in patients who are have three major pharmaceutical actions: analgesia, anti- receiving—or whom have received—MAO inhibitors in pyretic, and antiplatelet. the past three weeks. In small doses (less than 1,000 mg), salicylate com- pounds are effective for the relief of mild to moderate pain from muscular strains, joint discomfort, headache, and the like. The pain-relieving action of salicylates is primarily at the peripheral site of infl ammation, not centrally in the brain Naloxone is typically administered parenterally, either as is the case with narcotics. intravenously or intramuscularly. Recently, a nasal form of naloxone has been marketed, which would avoid the use of intravenous needles in this HIV-prone population. Infl ammatory Process The onset of naloxone is one to two minutes when admin- Whether caused by a break in the skin (infection), oxygen istered intravenously and can last for up to one and one-half deprivation (hypoxia), chemical irritation (inhalation of gas), hours. Predictable side effects of opiate antagonists (such as or trauma (mechanical injury), the body initiates an infl am- naloxone) include tachycardia, hypertension, and vomiting. matory response at the site of the injury. The infl ammatory The half-life of most opiates is at least twice as long (four to response is an exact process that begins immediately and fi ve hours in most cases), requiring repeat doses of naloxone includes nonspecifi c defenses, phagocytes, mast cells that in order to obliterate the effects of the opiate. release histamine (causing vasodilatation), macrophages that release lysosomal enzymes, and specifi c responses such as antibodies. The activities of these various body defenses culminate Street Smart in the signs of local infl ammation typically manifested by redness and swelling, histamine-induced vasodilation, the accumulation of dead leukocytes and bacteria as pus, and Hurried administration of naloxone, a narcotic the release of pyrogens (fever-producing chemicals) from antagonist, to a depressed newborn of a heroin the leukocytes. addicted mother, or a mother on methadone Prostaglandins, unsaturated fatty acids, are pivotal in this response. Prostaglandins increase postcapillary venule per- maintenance, can precipitate a seizure in the meability as well as smooth muscle contraction. More impor- newborn.31 tantly, prostaglandins produce the pain, either visceral or somatic, that is characteristic of an infl ammatory response. 692 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Inhibition of prostaglandin production therefore reduces or While not a toxicity per se, aspirin is not given to children eliminates the pain. Salicylates work by bonding to an enzyme because of the association between aspirin given to children called cyclooxygenase, which would normally bind with the with a fever of unknown origin (FUO) and Reye’s syndrome, fatty acids to produce prostaglandins.33 Salicylates thus inter- an acute encephalopathy. Reye’s syndrome is an abnormal rupt the production of pain-producing prostaglandins. degeneration of fat, especially in the viscera, that can also Without prostaglandins, prostaglandin derivatives— lead to acute encephalopathy. including thromboxane A2 (TxA2)—cannot be produced. TxA2 causes local vasoconstriction and encourages the degranulation of platelets, the fi rst step in the coagulation cascade (sometimes called production of the platelet plug). Street Smart Thus, salicylates are also anti-platelet drugs. As such, sali- cylates (specifi cally aspirin) have seen a great deal of use in Aspirin in routine doses reduces fever. Aspirin in preventing the formation of thrombus that can lead to acute myocardial infarction or cerebral vascular accident. large doses can actually induce a paradoxical rise in The third infl ammatory response, fever, is also affected temperature. Well-meaning parents can overdose a by salicylates. A febrile response is caused when pyrogens child on aspirin, see the child’s temperature rise, and are released from the site of the infl ammation and circulate then mistakenly administer more aspirin, thinking to the hypothalamus. These pyrogens then affect the hypo- thalamus and the body’s temperature is changed. Salicylates they are treating the fever. are thought to reset the body’s temperature set-point back to normal by interfering with circulating pyrogens. Salicylate Toxicity Nonsteroidal Anti-Infl ammatory Drugs An allergy to aspirin is a relatively common drug allergy, The nonsteroidal anti-infl ammatory drugs (NSAIDs), com- one whose presence is complicated by the large number monly referred to as aspirin substitutes, have found increas- of salicylate-containing compounds in drugs and over-the- ing popularity for several reasons: aspirin allergies, pediatric counter medications. Caution is advised whenever giving restrictions regarding aspirin use, and unwanted salicylate any drug to determine if an allergy exists, particularly an side effects (Table 31-3). The earliest non-salicylate analge- aspirin allergy. Salicylates have also been known to induce sics were the para-aminophenols (short-name anilines) which an asthma attack in prone patients, as shown in the previous included acetaminophen (APAP). Despite the difference in discussion of aspirin-induced asthma. Paramedics should formulation, the mechanism of action for these NSAIDs is also be particularly aware of the potential for hypoglyce- the same as for salicyclates (interference with the enzyme mia (particularly for children) that exists during a salicylate cyclooxygenase), which in turn inhibits prostaglandin pro- overdose. duction and thromboxane. Intentional or non-intentional overdose of salicylates A notable difference between the two products (NSAIDs creates a mixed respiratory alkalosis secondary to increased and aspirin) is that aspirin irreversibly interferes with platelet carbon dioxide production and metabolic acidosis due to the function for the life of the platelet, whereas most NSAIDs do increased metabolism and increased metabolic acid produc- not interfere with platelet function at all. tion.34 Treatment focuses on routine gut decontamination as well as reversal of the acid–base disorder.35 If the patient expe- Acetaminophen Toxicity riences spasms of the muscles (titanic spasm) secondary to The increasing popularity of any drug often results in cases of the acidosis, calcium gluconate is effective for offering symp- toxicity. An overdose of aspirin is usually quite evident, as the tomatic relief while the underlying acidosis is corrected. patient goes into a metabolic acidosis. His or her respirations Table 31-3 NSAIDs Class Drug Onset Half-Life Dose Acetic acids Diclofenac 31 min 2 hours 50 mg PO Indomethacin 31 min 4 hours 25/50 mg PO Ketorolac 10 min 4 hours 30 mg IV Oxicams Piroxicam 2 to 4 hrs 24 hours 20 to 40 mg Propionic acids Ibuprofen 31 min 2 hours 310 to 800 mg Naproxen 60 min 12 hours 250 to 500 mg Pharmacological Therapeutics for Medical Emergencies 693 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. these cases would only serve to mask the underlying pathol- Street Smart ogy and put the patient at risk for more serious and poten- tially life-threatening complications. For example, convulsions secondary to eclampsia (tox- Originally, many NSAIDs were FDA approved emia of pregnancy) can be effectively treated with either prescription medicines. Manufacturers of these FDA diazepam or phenytoin. However, current evidence suggests prescription medicines requested (and have received) that magnesium sulfate is the drug of choice in these cases permission to sell some of these NSAIDs as over- because it treats the underlying pathophysiology.37 That said, a distinction must be made between the woman with eclamp- the-counter (OTC) medications. The only difference sia who is seizing and the woman with a seizure history who between prescription NSAIDs and OTC NSAIDs is the also has pre-eclampsia. In the fi rst case, magnesium sulfate dose of the drug. The assumption is that the patient would be preferred, whereas in the latter case diazepam would be preferred. using an OTC will follow the package instructions to While the possible teratogenic effects of seizure medica- avoid the side effects and complications associated tion must be considered before prophylactic use is advised, a with larger doses. reoccurrence of a seizure can also produce fetal anoxia. For the patient with a previous diagnosis of epilepsy (recurrent seizures without known cause), the most likely cause of another seizure is subtherapeutic levels of anticon- would become rapid (tachypnea) and the patient would vulsant medication. For whatever reason (e.g., sudden with- become outwardly symptomatic. drawal or poor compliance), the drug level in the plasma In the case of many NSAIDs, there are no immedi- drops below the therapeutic level and the patient experiences ate outward manifestations of toxicity. Acetaminophen, for a breakthrough seizure. Regardless of this fact, other etiolo- example, is highly hepatoxic.36 Undiscovered acetaminophen gies for seizure cannot be ignored and must be ruled out. toxicity can cause permanent liver damage within three days While anticonvulsant medications can help a patient of the overdose. return to the activities of a normal life (e.g., driving a car), these drugs do not cure epilepsy. They only control the num- Convulsions ber and severity of each seizure. However, four out of fi ve patients with epilepsy can have their seizures controlled A generalized convulsion, the outward manifestation of a with medications. seizure, is a series of whole body contractions (tonic), then repetitive contractions (clonic), that are immediately pre- Anticonvulsant Medication ceded by a loss of consciousness. The underlying seizure is Over the centuries, seizures have been variously described the result of random and disorganized neuronal discharge as the work of evil spirits, the patient’s soul wrestling with within the brain, particularly across the motor strip of the the devil, and as a rabid infection, after witnessing the same cerebral cortex, anterior thalamus, and basal ganglia. frothing of the mouth |
as seen with patients who were infected The origin of the convulsion can be from an abnormal with rabies. Not until the works of Jean-Martin Charcot, in focus in the brain that is triggered by hypoxia, hypoglycemia, the mid-1900s, was the grands paroxysmes considered a pos- hyperthermia, and other stimuli. It can also be triggered by sible symptom of a greater pathology—the result of poten- extra-cranial sources (such as toxic inhalations, electrolyte tially curable organic lesions.28 imbalances, or drugs) or iatrogenic sources, secondary to In the past, treatment for epilepsy often started with a subtherapeutic anticonvulsant levels. barbiturate. Phenobarbital was frequently chosen because of The chaotic brain activity during a seizure is somewhat its margin of safety (discussed earlier). Subsequently, newer, analogous of the chaotic myocardial activity during ventricu- more effective medications have largely replaced phenobar- lar fi brillation—purposeless and potentially life-threatening. bital for the treatment of epilepsy. However, phenobarbital Regardless of the cause, the patient lapses out of con- still sees use in the emergency setting, primarily where respi- sciousness and is at risk for injury secondary to falls or status ratory depression can be managed expertly and for the few epilepticus, a condition of unremitting convulsions. cases of uncertain eclampsia and status epilepticus. The therapeutic goal of anticonvulsant medications is to raise the seizure threshold (by depressing the epileptic focus Mechanism of Action within the brain) without altering the patient’s mental status and CNS functioning. Most anticonvulsants, including phenobarbital, negatively In every case, regardless of prior history, Paramedics infl uence the action potential of the neuron and thus inhibit should attempt to identify and treat potentially reversible spurious discharges. The majority of anticonvulsants act as causes of convulsions, such as hypoxia, hypoglycemia, or sodium channel-blockers, a mechanism that is similar to the hyperthermia. Anticonvulsant medications administered in mechanism of a Class IB antidysrhythmic medication. 694 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Barbiturates Hydantoins and Pregnancy Barbiturates, including phenobarbital, are a class of CNS Women with a history of epilepsy who become pregnant are depressants that have seen second service as anticonvul- often taken off of hydantoins to eliminate the risk of fetal sants. One advantage of barbiturates is the wide variety hydantoin syndrome (FHS). Hydantoin use during preg- of delivery methods (PO, IV, IM) as well as the various nancy can generate birth defects such as cleft lip, cleft palate, duration of actions. and congenital heart anomalies.40,41 Primidone, whose active metabolite is phenobarbital, is If left untreated, approximately 50% of pregnant women seeing greater use for control of seizures and is often used with a prior seizure history will experience at least one sei- in combination with carbamazepine and phenytoin. By being zure during their pregnancy.42 Seizure during a pregnancy used together, these drugs permit lower doses of each. can induce fetal anoxia, which can result in congenital birth defects including mental retardation. Hydantoins The quandary lies in whether to prophylactically treat the seizure disorder, and potentially risk FHS, or risk a seizure One of the oldest and most widely used anticonvulsants, and fetal anoxia. In most instances, alternative medications phenytoin, belongs to the class of hydantoins. As a class, are explored. If these are ineffective, then the lowest possible these drugs are chemically related to barbiturates and act to dose of hydantoin is prescribed. decrease the infl ux of sodium (i.e., sodium channel-blockers), thereby decreasing neuronal excitability. Carbamazepine Fosphenytoin, another hydantoin, is the prodrug to phe- Carbamazepine has a mechanism of action that is similar to nytoin. Fosphenytoin has a rapid onset of action (peaking in hydantoins but is chemically similar to the tricyclic antide- less than six minutes), can be administered intravenously at a pressants. Carbamazepine is used, with good effect, to control rate three times faster than phenytoin (without cardiac com- a large variety of seizures including partial seizures with com- plications), and causes less burning at the IV site.38 Cumula- plex symptoms, as well as generalized tonic-clonic seizures. tively, these advantages make fosphenytoin desirable as an Carbamazepine is slow to absorb. It is not unusual for the emergency medication. drug to take a month or more to obtain therapeutic levels in the blood. Despite this obstacle, carbamazepine is the drug Hydantoin Toxicity of choice for many pediatric patients because of its low inci- Maintaining a serum plasma level of hydantoins that is dence of side effects. Concurrent administration of erythro- t herapeutic—and not toxic—is complicated by the distribu- mycin, an antibiotic occasionally prescribed to children, can tion and biotransformation of the drug. Hydantoins quickly lower circulating plasma levels of carbamazepine in the child become protein-bound (primarily to blood albumin) while with epilepsy and result in breakthrough seizures. in circulation. Thus, a large percentage of the drug is phar- Carbamazepine Toxicity macologically unavailable. Only when all available albumin becomes saturated are suffi cient plasma levels of free drug Simultaneous administration of isoniazid (another antibiotic available for its intended therapeutic effect. used to treat tuberculosis) and propoxyphene (an analgesic) Compounding this diffi culty is the drug’s biotransfor- can cause an increase in blood serum levels of carbamazepine mation. The liver’s enzymatic system, the cytochrome P-450 to the point of near-lethal toxicity. system, is very effective in reducing hydantoins to inactive Co-administration of carbamazepine with an MAO metabolites. However, hepatic metabolism has limits. Once inhibitor (an antidepressant) can also cause elevated tem- these limits are reached, then more free drug is available. perature (hyperpyrexia), elevated blood pressure (to hyper- Therefore, to reach desired therapeutic levels of hydantoin, tensive crisis levels), and, paradoxically, seizures leading to dosing must take into account both the volume of blood pro- status epilepticus. teins as well as hepatic biotransformation. Overcoming these Succinimides two impediments, even with small incremental increases in hydantoin dose, can result in marked, or near-toxic, eleva- Succinimides, as a class of anticonvulsant medication, raise tions in serum drug levels. the seizure threshold and suppress nerve conduction in the The patient who is toxic on hydantoin will present with motor cortex, resulting in good seizure control. Ethosuxim- an ataxia (a disequilibrium in walk that resembles a drunk- ide, an example of a succinimide, is used to treat pediatric ard’s stagger) and a nystagamus (a fi ne tremble of the eye absence seizures. when holding a lateral gaze).39 Unsuspecting Paramedics may incorrectly deduce that the patient is intoxicated on alcohol. Valproic Acid Hydantoins, in toxic doses, have signifi cant cardiac effects, Valproic acid and divalproex have similar actions (increasing similar to Class IB antidysrhythmic drugs. Left untreated, levels of the inhibitory neurotransmitter GABA within the these cardiotoxic effects can lead to cardiovascular collapse brain) and are used alone or in combination with other anti- and death. convulsants to treat absence seizures. Pharmacological Therapeutics for Medical Emergencies 695 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Valproic acid is also useful in the emergent treatment of common neurological disorder.43 The onset of Parkinson’s status epilepticus that is unresponsive to standard treatments. disease can start as early as 40 years of age and is slightly more prevalent in males. While Parkinson’s disease itself Benzodiazepines is not a medical emergency, the effects of the disease (like Benzodiazepines, discussed earlier, are also useful as anti- falls, which often result from dyskinesia) create emergency convulsants. Paramedics, when confronted with a patient in situations. status epilepticus, can administer a benzodiazepine (such as diazepam or the short-acting midazolam) for control of the Pathophysiology seizure. In those cases, Paramedics must be prepared to man- As a person develops Parkinson’s disease, the number of age respiratory depression secondary to the benzodiazepine. do paminergic receptors in the brain is reduced (Figure 31-1). The gradual loss of these receptors results in a progressive Parkinson’s Disease deterioration of brain function. Dopaminergic receptors are Parkinson’s disease has an insidious onset, starting with barely abundant in the substantia nigra, a portion of the central ner- perceptible rhythmic tremors and progressing to gross motor vous system’s extrapyramidal motor system responsible for dysfunction. In an advanced stage, the patient with Parkin- muscle coordination and movement. son’s disease exhibits extremely slow (bradykinesia) or dif- Normally, the dopaminergic receptors produce an inhibi- fi cult (dyskinesia) movement. For example, if a patient with tory effect upon the extrapyramidal motor system. In the Parkinson’s disease is gently pushed, the patient’s muscles absence of dopaminergic receptors, the cholinergic receptors may not be able to respond quickly enough to stop a fall. take dominance by stimulating the extrapyramidal motor. The The combination of loss of airway control, manifested clinical manifestations of Parkinson’s disease are the result of by drooling and slurred speech, as well as a blank mask-like this imbalance between dopaminergic stimulation and cho- stare, makes the patient with Parkinson’s disease appear dull linergic stimulation. Classic symptoms of Parkinson’s disease and dimwitted. Yet, Parkinson’s disease affects the intellec- include muscle rigidity, resting tremors, a forward leaning tual capacity of only 40% of the patient population affl icted posture, and a shuffl ing gait. with Parkinson’s disease. However, the combination of Drugs That Are Used to Treat events just described can often produce severe depression in this patient population, leaving an appearance of dwindling Parkinson’s Disease intellectual capacity. Treatment of Parkinson’s disease focuses on either blocking Approximately 150 in 100,000 people over age 65 the cholinergic receptors (suppressing the effects of acetylcho- will develop Parkinson’s disease, making it the fourth most line) or increasing the level of dopamine receptor stimulation. Cholinergic neuron Acetylcholine Caudate nucleus To muscles Akinesia Normal function Hyperkinesia Feedback neuron Putamen Caudate nucleus GABA Dopaminergic Globus Thalamus neuron pallidus Red Substantia nucleus nigra Substantia nigra Figure 31-1 Parkinson’s disease. 696 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. The quintessential cholinergic blocker is atropine, the bella maintains those mundane vegetative functions of life, while donna alkaloid extracted from the nightshade plant. Atropine the sympathetic nervous system stands by, ready to react at was used for years to treat Parkinson’s disease. a moment’s notice to any threat to that life. Similarly, the More recently, newer synthetic cholinergic blockers, endocrine system, via its arrangement of chemical messen- such as benztropine, have been used with better effect. These gers, helps to maintain an optimal internal environment for cholinergic antagonists decrease dyskinesia in nearly 50% of metabolism while the nervous system is ready to respond to patients suffering from Parkinson’s disease. the ever changing external conditions. The goal in both cases Currently, treatment of Parkinson’s disease is focusing is identical—to maintain a balance (i.e., homeostasis) within more on how to increase dopaminergic receptor stimulation the body and life. than on blocking cholinergic receptors. Means to achieve The chemical messengers that stimulate the body’s this goal include administering drugs that increase dopamine organs and help to maintain the body’s internal environment levels (such as levodopa) or stimulating release of dopamine (its milieu) are called hormones (from the Greek meaning from neuronal storage vesicles (e.g., amantadine). “to arouse”). Hormones are produced and excreted from Alternatively, levels of dopaminergic receptor activity can endocrine glands located in various locations within the body. be increased, not by inducing the body to produce or release The amount of hormone in the bloodstream is a function of a more dopamine, but by using dopamine agonists. Examples |
feedback mechanism, a mechanism that monitors and alters of dopamine agonists include bromocriptine, a plant alkaloid, the amount of hormone released. and pramipexole. The most common feedback mechanism is the negative Finally, dopamine levels in the neurosynapse can be feedback loop. A negative feedback loop occurs when increas- increased by decreasing dopamine destruction by mono amine ing levels of a hormone stop the secretion of more hormone. oxidase during uptake. A monoamine oxidase inhibitor, such An exception to hormonal control by feedback mechanism as selegiline, is often given together with levodopa. The is seen when the sympathetic nervous system stimulates the combination of drugs permits lower doses of each, thereby release of epinephrine from the adrenal medulla (an endo- decreasing undesirable side effects while still achieving the crine gland) during stress. This action would be classifi ed as same therapeutic goal. neuronal control. Once a hormone is released into the blood, it circulates Precautions until it is attracted to a target cell with the correct receptor (a Two types of monoamine oxidase exist in the body: type A “key in lock” concept). When linked together, the hormone and type B. MAO inhibitors used to treat Parkinson’s disease can either enhance the cell’s function (a direct effect) or it can primarily affect monoamine oxidase B. Inappropriate admin- facilitate an aspect of the cell’s function. For example, insulin istration of other MAO inhibitors, along with levodopa, can (a hormone) attaches to insulin receptors, which then permit precipitate profound hypertension or hypertensive crisis. the passage of glucose into the cell. Hormones and Pharmacy The hormone’s impact, at the cellular level, is a function of the amount of hormone in the bloodstream and/or the number Street Smart of receptors on a cell. In the fi rst case, if there is a hormone defi cit, as is the case in diabetes mellitus, then supplemental Administration of meperidine to patients on MAO hormone (e.g., insulin) can be administered. inhibitors can cause severe reactions, including When a larger than physiological dose of hormone is administered, there can also be a new or different effect, a profound hypertension, respiratory depression, pharmacological effect. An example of this pharmacologi- hyperpyrexia, and seizures. Alternatively, cal effect is when antidiuretic hormone (ADH), also called administration of morphine is less likely to produce vasopressin, is given in larger than physiologic doses. When these unwanted side effects. that happens, it induces a potent vasoconstrictor effect upon the blood vessels.44 Alternatively, there can be an increase in the number of receptors on the cell, as a result of low hormone lev- els, making the cell more sensitive to the available hor- Drugs That Affect mone. The converse is also true (i.e., there can be fewer the Endocrine System receptors). The change in the number of cell receptors can either increase (called upregulation) or decrease (called The association of the endocrine system and the nervous downregulation) according to hormone levels. In certain system is somewhat analogous to the relationship between pathological conditions it may be necessary to block these the parasympathetic and the sympathetic nervous system. hormone receptors to moderate the hormone’s effect upon The parasympathetic nervous system, via its vagus nerve, the cell. Pharmacological Therapeutics for Medical Emergencies 697 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Diabetes Insulin Type 1 diabetes is characterized by a total loss of insu- Insulin combines with receptors in the cell wall to permit the lin production, making necessary life-long subcutaneous passage of glucose into the cell. This in effect lowers the blood injections of insulin. However, the vast majority of patients sugar in the bloodstream. Insulin also stimulates the storage with diabetes, more than 80%, continue to produce some of excess glucose in the liver in the form of glycogen. insulin. These patients produce insuffi cient quantities of Simultaneously, insulin inhibits the release of free fatty insulin or have an increased resistance to the insulin, and acids. These fatty acids would normally be excreted when- thus are termed type 2 diabetics. The most common cause of ever glucagon is present. (Glucagon stimulates the use of fat type 2 diabetes is obesity; the hallmark of obesity- induced for energy in a process called lipolysis.) diabetes is insulin resistance (a case of either downgrading Since insulin is a protein, it cannot be taken orally as insulin receptors or having an ineffective insulin/receptor stomach acids would immediately break it down into inert effect). materials. Thus, insulin must be given parenterally, usually The fi rst level treatment for many of these patients with via subcutaneous injection, into the peripheral capillary bed type 2, or non-insulin dependent diabetes mellitus (NIDDM) where it can be absorbed into the central circulation. It can is weight control through diet and exercise. Failing this, the also be given intravenously. patient must then resort to an alternative therapeutic strategy— Early insulin was obtained from animals, such as pigs either insulin injections or the use of hypoglycemic agents. and cows. In some cases, patients developed an allergy to the pork or beef insulin. Currently, insulin is bio-engineered and Drugs That Are Used is identical to human insulin, thereby preventing any allergy to Treat Diabetes to insulin. Insulin’s onset and duration of action can be altered Diabetes mellitus is not a single disease. More correctly, dia- by mixing the insulin with other materials such as zinc. betes is a group of syndromes of varying etiologies that have Paramedics should be aware of these other insulin prepara- a similar presentation: increased blood glucose. Even seem- tions, especially the time of onset and peak effect, to be ingly minor alterations in blood glucose can have a dramatic able to anticipate periods of hypoglycemia following an impact on some patients. These changes in blood glucose lev- insulin overdose. els are the source of many EMS calls for assistance. The most rapid-acting insulin is synthetically pre- Blood glucose levels are maintained within a physi- pared insulin that is part of a zinc salt. Rapid-acting regu- ologic range by two hormones produced in the pancreas. lar insulin lowers blood sugar within minutes when given The first hormone, insulin, is produced in the beta cells intravenously. within the islets of Langerhans of the pancreas. It low- The intermediate-acting insulin preparations use ers blood glucose by facilitating passage of blood glucose protamine to prolong their duration of action. Protamine, a into the surrounding cells and tissues. When the level peptide, makes insulin a less soluble complex, slowing absorp- of blood glucose rises, then the pancreas produces more tion and increasing its duration of action. Intermediate-acting insulin. When the level of blood glucose drops, then the insulin, or neutral protamine Hagedorn (NPH), is never given alpha cells within the islets of Langerhans release glu- intravenously. cagon (a hormone that increases blood glucose levels). Long-acting insulin preparations are the result of vari- Together, these two hormones help to maintain a blood ous processing techniques and result in insulin that has a glucose level within a physiological range sufficient for delayed onset of action as well as a prolonged duration of the body’s metabolic needs. action (Figure 31-2). For most patients, a relatively stable blood glucose level Drugs That Are Used to Treat would be desirable and the option of mixing various insulins Diabetic Emergencies (rapid, intermediate, and long-acting) to attain a near constant Diabetic emergencies can be neatly divided into problems of blood glucose level would be reasonable. With this thought low blood sugar (hypoglycemia) and high blood sugar (hyper- in mind, Lente insulin, a mixture of 30% semilente insulin (a glycemia). Hypoglycemia often has a more dramatic presen- rapid-acting form of regular insulin) and 70% ultralente insu- tation, such as sudden unconsciousness or convulsions. For lin (an extended-insulin zinc suspension that is poorly soluble) this reason, it is a common source of calls for EMS. was created. Lente insulin helps to avoid some of the tendency Diabetic hypoglycemia can be the result of either toward hypoglycemia experienced by some diabetic patients. increased insulin levels, via self-administration or pancre- As noted earlier, Paramedics should be aware of the atic production, or insuffi cient food intake in relation to peak effect of the various insulins. In cases where the patient insulin levels. To understand the etiology of these hypogly- has mixed insulin and subsequently has a period of hypo- cemic periods, it is necessary to understand the action of the glycemia, the patient can expect to have another episode of hormone insulin. hypoglycemia. 698 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Profiles of Human Insulins and Analogues when accompanied by fever; and trauma—can lead the dia- betic patient to have an unexpected episode of hypoglycemia. Alternatively, changes in eating habits or activity patterns—or new medications such as MAO inhibitors, sulfonamides, sali- cylates, beta-blockers, and ethanol (EtOH)—can cause inad- vertent hypoglycemia.48 The clear majority of hypoglycemia cases in patients with type 1 diabetes are related to changes in insulin regime. When the patient becomes hypoglycemic, another 0 2 4 6 8 10 12 14 16 18 20 22 24 hormone (epinephrine) is released. Epinephrine normally Hours inhibits insulin secretion, thereby increasing blood glucose levels in an emergency. Released by sympathetic stimula- Aspart, lispra (4 to 6 hours) tion of the adrenal medulla, epinephrine is responsible for Regular (8 to 10 hours) the majority of the symptoms present during a hypogly- NPH (12 to 20 hours) cemic episode, such as tachycardia, tremors, diaphoresis, Glargine (20 to 26 hours) headache, and hypertension. Ultralente (18 to 24 hours) Treatment of Hypoglycemia Figure 31-2 Onset of action of insulin preparations. Treatment of hypoglycemia is simple: Replace the glucose until adequate levels of blood glucose are available to resume Insulin and Hyperkalemia normal metabolism. Methods of glucose administration include oral paste as well as intravenous administration. Typ- Insulin is a negatively charged amino acid. As such, insulin ically, 25 grams of dextrose is administered intravenously, binds to positively charged electrolytes, such as potassium. either as 500 cc of 5% dextrose in sterile water (D5W) or Elevated potassium levels (hyperkalemia) lead to signifi cant 50 cc of 50% dextrose solution. dysrhythmias and can be life-threatening. Intravenous admin- The effects of intravenous administration of 50% dex- istration of insulin can be used to treat hyperkalemia because it trose upon hypoglycemia is immediate but not without its binds the potassium to the insulin. When the insulin attaches to complications. Concentrated dextrose is hypertonic. There- the cell, it drives the potassium into the cell with it and out of fore, administration through a misplaced intravenous line the circulation.45-47 This technique is very effective for lowering and subsequent subcutaneous infi ltration can lead to severe serum potassium levels, but caution must be exercised to pre- tissue necrosis. vent inadvertent hypoglycemia. Typically a glucose-containing solution is concomitantly administered along with the insulin. Street Smart Street Smart A hypoglycemic patient can present in the fi eld Diabetes is a leading cause of blindness, which with facial droop, confusion, and slurring of words. occurs because of diabetic retinopathy. Patients with This presentation may be mistaken for a stroke diabetes, who are unable to see or unable to see and grave complications may occur subsequent clearly, may unintentionally overdose themselves to this misdiagnosis.49 Similarly, a patient with with insulin. Aids for the blind (e.g., guide dogs) stroke symptoms should not be assumed to have should raise the Paramedic’s index of suspicion that hypoglycemia. Inappropriate administration of the cause of the medical emergency may be visual concentrated dextrose to a stroke patient with impairment that may be diabetes related. a normal blood sugar level can induce changes |
Hypoglycemia secondary to the osmotic effect of the concentrated dextrose. Dextrose should only be administered Untreated hypoglycemia, sometimes referred to as insu- lin shock, can lead to coma and even death. A number of to those patients with evidence of hypoglycemia factors—such as the stress of surgery; infections, especially (e.g., a low glucose meter reading). Pharmacological Therapeutics for Medical Emergencies 699 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Plasma insulin levels An alternative treatment for hypoglycemia, when intra- (zona fasciculata) produces the glucocorticoids, including the venous administration of glucose is not possible, is intra- principal glucocorticoid cortisone. The innermost zone (zona muscular injection of glucagon. Glucagon, which is naturally reticularis) produces the adrenal androgens and estrogen. secreted by the alpha cells in the pancreas, raises the blood The glucocorticoids help to regulate metabolism of car- glucose level by liberating glucose from glycogen stores in bohydrates, increase blood glucose by helping to convert the liver. By defi nition, for glucagon to work there must be glycogen to glucose, antagonize insulin, and help create glu- adequate stores of glycogen in the liver. Patients with liver cose from amino acids by a process of protein catabolism disease or those who are chronically malnourished may not (gluconeogenesis). have glycogen stores, thereby rendering glucagon useless. The glucocorticoids also inhibit both the immune system Glucagon’s onset of action is dependent upon its route and the infl ammatory response by suppressing the chemical of administration (15 minutes via IM injection and 31 min- mediators such as prostaglandins, leukotrienes, bradykinin, utes by subcutaneous injection). The delay in onset of action serotonin, and histamine. makes intravenous dextrose administration more desirable. Levels of glucocorticoids rise during periods of stress, providing needed glucose. However, they also lower resis- Oral Hypoglycemia Agents tance to infection during those times. Chief among these naturally occurring glucocorticoids is cortisol. Cortisol secre- The three therapeutic strategies that could potentially increase tion, regulated by the hypothalamus and the anterior pituitary insulin levels include (1) stimulation of the beta cells in the gland via adrenocorticotropic hormone (ACTH) stimulated pancreas to produce more insulin or to reduce glucagon l evels, by low levels of cortisol, travels throughout the body bound (2) suppression of the alpha cells in the pancreas, or (3) an to blood proteins such as albumin. increase in the binding of insulin to receptors on the cells. The sulfonylureas were the fi rst class of drugs that could Synthetic Glucocorticoids produce all three of these desirable mechanisms of action. Paramedics may be called upon to administer steroids in The introduction of sulfonylureas eliminated the need for order to treat severe infl ammatory responses that occur in some patients to inject insulin. Each successive generation severe asthma, including status asthmaticus, acute allergic of sulfonylureas, while not more effective than the previous, reactions, and anaphylactic reactions that are unresponsive have as positive features a longer duration of action as well as to standard treatment. fewer side effects. Treatment with steroids may also be indicated for Other oral hypoglycemia agents include (1) the alpha- gram-negative septic shock.50 Endotoxins released from the glucosidase inhibitors, which delay the digestion and absorp- gram-negative bacteria injure cells and alter the patient’s tion of carbohydrates, permitting subphysiological levels of coagulation. Glucocorticoids suppress many of the chemi- insulin production to suffi ce; and (2) other non-sulfonylurea cal mediators in the coagulation cascade, in addition to pro- agents, such as metformin, which have a similar mechanism tecting cellular membranes. Glucocorticoids also potentiate of action. catecholamines, such as dopamine, increasing their vasocon- The newest class of antihyperglycemia agents lowers strictive activity. insulin resistance, permitting more effective use of the Glucocorticoids are also administered as replacement patient’s own endogenous insulin. These medications stimu- therapy for adrenocortical insuffi ciency (Addison’s disease). late the release of helper proteins from the muscles and fat. Typically, a dose of hydrocortisone, the synthetic equivalent These proteins enhance the cells’ response to insulin by a to naturally occurring cortisol, is given: two thirds in the mechanism entirely different than the sulfonylureas’ mecha- morning and one third in the afternoon, to match the patient’s nism of action. Currently research is on–going for medica- circadian rhythm. tions that can lower insulin resistance, a major cause of type Glucocorticoids can be broken down into three subclas- II diabetes, particularly in the obese patient population. sifi cations according to their duration of action. The short- acting glucocorticoids include hydrocortisone and cortisone (which is converted into hydrocortisone in the body). These Drugs That Are Used to Treat short-acting agents generally have a half-life of about 8 to Adrenal Disorders 12 hours in the tissues. The intermediate-acting glucocorticoids include predni- The paired pyramid-shaped adrenal glands, located just sone and methylprednisolone. They have an average half-life above the kidneys, produce a rich supply of hormones that of 18 to 36 hours in the tissues. are essential to the body’s health. All of these hormones are Dexamethasone, an example of a long-acting steroid, produced from cholesterol and have a common steroid core is occasionally used to treat the edema seen following head (hence the term “steroids”). injury or secondary to a brain tumor.51 Beclomethasone dipro- Dividing the adrenal cortex into three zones, the outer pionate, another example of a long-acting steroid, is available zone (zona glomerulosa) produces the mineralocorticoids, in an aerosol form for long-term use in patients with severe chief among those being aldosterone. The larger middle zone asthma. This aerosol form permits lower doses than would be 700 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. given orally and minimizes some of the undesirable systemic epinephrine can cause paroxysms of hypertension, cause sus- effects of steroids. tained hypertension, induce a hypertensive crisis, and create a “runaway” tachycardia. Occasionally, an episode of hyperten- Precautions sion follows a meal of tyrosine-rich food, red wine, beer, or Administration of glucocorticoids may cause fl uctuating glu- aged cheese. Tyrosine is the precursor of epinephrine. cose levels, as glucocorticoids promote metabolism. Use of Rupture of a pheochromocytoma can literally lead to these steroids may cause hypoglycemia in diabetics and those a systemic fl ood of epinephrine accompanied by profound prone to hypoglycemia. hypertension, severe abdominal pain, and a potentially fatal Glucocorticoids also have some related mineralocorti- hemorrhage. Treatment for a hypertensive emergency includes coid activity. The result is retention of salts and water with intravenous administration of an alpha-blocking agent (e.g., subsequent edema and hypertension that can progress to con- phentolamine) and a beta-blocker (e.g., metoprolol) to con- gestive heart failure in susceptible patients. Long-term use of trol the runaway tachycardia. these steroids can result in iatrogenic Cushing’s syndrome. The patient’s presentation will include a puffy face (Moon Drugs That Are Used to Treat face), acne (early sign), hypertension, weight gain, and an increase in body hair. Ovarian Disorders Patients on steroids become dependent on those steroids, Estrogen and progesterone are the principal sex hormones as levels of naturally produced steroids drop off. Abrupt produced by the ovaries. Created from cholesterol (like the withdrawal of these steroids can lead to acute adrenal insuffi - steroids of the adrenal glands), estrogen and progesterone ebb ciency.52 Tapering doses of the steroid are required for patients and fl ow rhythmically, creating a woman’s menstrual cycle. who are prescribed steroids for longer than two weeks to gen- This continues until pregnancy interrupts the sequence. tly re-establish a natural response from the adrenal gland. Estrogen is primarily responsible for a woman’s sexual development as well as regulation of her menstrual cycle. Mineralocorticoids Besides effects upon the ovaries, estrogen also has metabolic The primary mineralocorticoid, aldosterone, is largely effects. For example, estrogen helps to maintain bone density. responsible for electrolyte and fl uid balance and acts upon the When a woman stops producing estrogen (i.e., menopause), she distal tubules of the kidneys. This steroid primarily conserves is at greater risk of losing bone density (i.e., osteoporosis). sodium, while promoting potassium and hydrogen ion (acid) Estrogen also has a cardioprotective effect. This alters excretion. The production of aldosterone is controlled by the the metabolism of cholesterols, decreases serum levels of renin-angiotensin mechanism, which is activated by sodium low-density lipoproteins and high-density lipoproteins, and and/or blood volume depletion. prevents atherosclerosis. High levels of aldosterone can induce hypokalemia, which can create cardiac irritability manifested as ventricular Estrogen Therapy ectopic beats, as well as a metabolic alkalosis. Estrogen can be used to prevent pregnancy (a contracep- Antiadrenal Medications tive effect) or during menopause at a one fi fth dose. Estro- gen is used during menopause to prevent atrophic vaginitis, Antiadrenal medications suppress adrenal cortical function, vasomotor symptoms (i.e., hot fl ashes), and abnormal uter- resulting in decreased production of these steroids. Used to treat ine bleeding. Post-menopausal women are at greater risk of Cushing’s syndrome as well as adrenal tumors, these medica- osteoporosis. If unchecked, osteoporosis can lead to brittle tions inhibit the enzyme that converts cholesterol into steroids. bones that fracture. (Hip fractures are more common among As these medications also suppress estrogen production these women.) Estrogen replacement therapy can decrease in the adrenals (a hormone thought to be related to breast the risk of osteoporosis. cancer), investigational cancer studies are in progress. Estrogen is also an effective treatment for some estrogen- Adrenal Medulla sensitive metastatic breast cancers. Paradoxically, estrogen slows tumor growth when it normally increases breast devel- At the core of the adrenal glands is the medulla. The adre- opment in those cases. Conversely, some breast cancers are nal medulla produces the catecholamines norepinephrine and estrogen-dependent. These breast cancers are treated with an epinephrine. Secretion of epinephrine from the medulla is anti-estrogen agent, such as tamoxifen, which blocks estro- largely under sympathetic nervous control (i.e., a neurohu- gen receptors in the tumor. moral regulation). Stimulation of the adrenal medulla can High-dose estrogen, or the morning after pill, a.k.a. plan result from hypoglycemia, hypoxia, hypercapnia, nicotine, B, is sometimes used as an emergency contraceptive (e.g., fol- and angiotensin II. lowing rape or contraceptive failure). If administered within While tumors of the adrenal medulla, called a pheochro- 72 hours, high-dose estrogens (such as diethylstilbestrol) can mocytoma, are rare (less than eight cases per million popula- induce menses, eliminating products of conception. Diethyl- tion), they can produce large amounts of epinephrine.53 Excess stilbestrol, therefore, has a pregnancy class of X. Pharmacological Therapeutics for Medical Emergencies 701 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Drugs That Are Used to Treat Street Smart Thyroid Disorders Estrogen in oral contraceptives can induce The thyroid gland (from the Greek word, meaning “shield- thrombophlebitis and thrombosis formation, leading like”) straddles the thyroid cartilage, commonly known as the Adam’s apple, with a thin isthmus in the middle. The fol- to strokes and pulmonary embolism.54 This risk is licles within the two lobes of the gland secrete the hormones increased in women over age 35 and in women who responsible for metabolism. smoke. Pathology of the thyroid gland involves either hyper- or hyposecretion of thyroxine (T4) or triiodothyronine (T3). Hyperthyroidism can be caused by Graves’ disease, thyroid cancer, or a goiter. Hyperthyroidism results in tachycardia, weight loss, nervousness, and exophthalmos (a bulging of Drugs That Are Used to Treat the eyes). If left unchecked, hypersecretion of thyroid hormones Pituitary Disorders can lead |
to thyrotoxic crisis (thyroid storm), a condition The pituitary gland is located just inferior to the hypothala- that can lead to death. Thyrotoxic storm’s symptomology mus nestled in the base of the skull. These are connected to includes atrial tachydysrhythmia, cardiogenic shock, and one another by a thin stalk of tissue called the infundibulum. hyperpyrexia secondary to a metabolism that is increased by This pituitary-hypothalamus axis produces a number of hor- as much as 60%. mones that control other glands. Thus, the pituitary is called Strong iodine solutions, such as Lugol’s solution, may the master gland. be administered during a thyrotoxic crisis. The iodine in The pituitary gland can be divided into two portions: the solution inhibits the formation of tyrosine, a precursor anterior and posterior. The posterior portion produces to epinephrine. Alternatively, thioamide derivatives, such as two hormones: antidiuretic hormone (vasopressin) and propylthiouracil, may be used. These agents inhibit thyroid oxytocin. The primary effect of antidiuretic hormone is hormone synthesis, preventing tyrosine production. to control plasma osmolality and maintain intravascular Hyperthyroidism is typically treated with either surgical volume. ADH achieves that goal by affecting the per- removal of the thyroid gland or administration of radioactive meability of the distal tubules of the kidney’s nephron. iodine, which results in the destruction of the thyroid gland. Oxytocin is discussed later in the section on drugs used The patient, like the patient with hypothyroidism, needs life- during pregnancy. long thyroid hormone replacement therapy. Levothyroxine, a synthetic thyroxine, is one of the more common thyroid preparations prescribed for hypothyroid- Vasopressin ism. Poor patient compliance with the prescribed replace- Vasopressin has received widespread attention for its poten- ment therapy can result in hypothyroidism and myxedema. tial role in cardiac arrest. The hormone’s pharmacological Myxedema is characterized by ataxia (drunken staggers), effect (vasoconstriction) may be useful as a fi rst-line therapy lethargy and confusion, headaches, and a non-pitting edema in cardiac arrest, following defi brillation.55–58 of the eyes, hands, and feet. Myxedema also results in edema Vasopressin is also useful in treating diabetes insipidus. of the tongue and laryngeal mucous membranes, making Diabetes insipidus is characterized by a lack of ADH and may speech slurred. The combination of symptoms might lead be caused by basal skull fractures injuring the infundibulum, less informed Paramedics to suspect intoxication. subsequently causing increased intracranial pressure. It could Amiodarone contains large amounts of iodine, approx- also be caused by a brain tumor or subdural hemorrhage that imately 37% by weight, and can induce hyperthyroidism compresses the infundibulum. There are a number of reasons in a small population of susceptible individuals.59,60 The why the pituitary gland would fail, all culminating in a scar- onset of a new atrial tachydysrhythmia is often seen in city of ADH. these patients. Without ADH, immense volumes of dilute urine are excreted (polyuria), upwards of 3 to 18 L a day, and the Drugs That Are Used patient wants to drink large volumes of water (polydipsia). If unchecked, diabetes insipidus can lead to dehydration, hypo- to Treat Anaphalaxis volemia, and shock. Inappropriate responses to allergens (i.e., allergy, autoim- Natural vasopressin, or synthetic derivatives such as munity, and alloimmunity) can be classifi ed jointly as hyper- lypressin, is prescribed to patients suffering from diabe- sensitivities. Hypersensitivities can further be classifi ed as tes insipidus. immediate or delayed. 702 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Paramedics are most concerned about immediate hyper- Ulcer Medicines sensitivity reactions, the most severe being anaphylaxis. Heartburn and the pain of peptic ulcer was formerly believed Untreated anaphylaxis can progress within minutes to a life- to be the result of excessive stomach acid, so medical attention threatening medical emergency. was turned toward reducing or neutralizing that acid. More A classic anaphylaxis is an IgE-mediated reaction. After recently, the pathogen Helicobacter pylori has been impli- exposure to a foreign protein—one that is inhaled, ingested, cated as the causative agent for peptic ulcers and a course or injected—the body’s immune system produces an antigen of antibiotics as its cure. However, there are other causes of specifi c antibody (IgE). The IgE binds to special crystalliz- stomach infl ammation. These include irritants like alcohol or able fragment (Fc) receptors on mast cells. aspirin, which can produce epigastric discomfort. A number When the patient is re-exposed to the allergen, it of medications, many of them over-the-counter medications, causes the Fc receptors on the mast cell surface to cross-link, one are available to help with these disorders. to the other, destroying the mast cell in the process and releas- ing the cell’s contents. This process is called degranulation. The majority of the symptoms of anaphylaxis are related Antacids to the degranulation of mast cells. Chemical mediators Antacids chemically neutralize stomach acid and bring relief released during degranulation include histamine. Histamine to those suffering from heartburn (i.e., gastroesophageal is responsible for the majority of symptoms associated with refl ux disease (GERD)), hiatal hernia, and gastritis. The com- an anaphylactic reaction: bronchoconstriction, increased vas- pounds calcium carbonate, sodium bicarbonate, magnesium cular permeability leading to angioedema, and vasodilation- salt, and aluminum salt are used for this purpose. induced hypotension.61 A concern with many of these medications involves some of their systemic effects. Patients with renal failure, who are Antihistamines on antacids, may develop toxicities and adverse reactions. Antihistamines are antagonists to histamine, their mecha- Other patients may, for example, develop a metabolic alka- nism of action being a competitive inhibition of naturally losis from prolonged or generous administration of sodium occurring histamines at the H1 receptors. Once H1 receptors bicarbonate. Aluminum-containing antacids should be are occupied by antihistamines, such as diphenhydramine, avoided in patients with Alzheimer’s disease. Antacids will the development of further histamine-induced angio- generally reduce the absorption of digoxin, possibly leading to dysrhythmia.63 edema, pruritis (itching), and bronchospasm is impeded. Antihistamines do not reverse pre-existing pathology Of greater concern is the altered absorption of many med- (e.g., vasodilation-induced hypotension). Furthermore, the ications as a result of changed stomach acidity. For example, pharmacokinetics in antihistamines are gradual, with an the pharmacokinetics of drugs that are weak bases, such as onset of action between 15 and 30 minutes (with a peak in antihistamines and tricyclic antidepressants, and drugs that one hour). are weak acids, such as sulfonamides and salicylates, will During anaphylaxis, time is of the essence and the drug be altered. Since the list of drug interactions with antacids of choice remains epinephrine.62 Epinephrine, administered is long, Paramedics should consider drug interaction when subcutaneously, has an immediate effect and reverses the assessing a patient who is also taking antacids. symptoms present in anaphylaxis. Epinephrine’s mechanism of action was previously discussed. Histamine Antagonists Histamine antagonists (discussed earlier), particularly the Drugs That Are Used to Treat H2 receptor blockers, are effective in inhibiting all phases of stomach acid secretion. Many examples of histamine Gastrointestinal Disorders From ancient Greece, when Hippocrates spoke of the runny “faeces” of dysentery, to contemporary discussions Street Smart of infantile diarrhea in developing countries, gastrointes- tinal complaints have historically plagued humanity. Many concoctions have been created to combat this malady. Patients will dismiss epigastric discomfort as being Oil of earthworm, listed in the Leiden pharmacopoeia in heartburn, denying the possibility that they are having 1741, was replaced by paregoric (liquid opium) in 1788. a heart attack, and will self-medicate with antacids Opium’s popularity is owed, in part, to its ability to con- (without relief). Paramedics should always have a high stipate, to “bind the bowel,” and halt diarrhea. Subsequent mineral preparations had some degree of success and an index of suspicion that heartburn has a cardiac origin entire pharmaceutical industry was created to treat this (an inferior wall AMI) and treat accordingly. common disorder.28 Pharmacological Therapeutics for Medical Emergencies 703 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. antagonists, such as cimetidine and ranitidine, are now avail- For example, drugs in the class of phenothiazines (such as able over-the-counter. chlorpromazine) and promethazine or metoclopramide stop nausea before the process of vomiting can be started. Emetics Anticholinergics can block acetylcholine receptors The quintessential emetic agent is syrup of ipecac. Used for located within the emetic center, thereby preventing vomiting. centuries as a purgative, it stimulates vomiting by both irri- This is the mechanism of action for scopolamine. Similarly, tating the stomach and rousing the vomiting centers in the histamine receptors in the emetic center can be blocked by brain. Syrup of ipecac is highly effective (greater than 80% antihistamines such as diphenhydramine or dimenhydrinate. of patients will vomit) and has a quick onset of action (within Another anti-emetic is odansetron, (Zofran®). Odansetron, 20 minutes).64 selective serotonin receptor antagonist, is especially effective as a pretreatment for nausea and vomiting, Some providers have Toxicity reported transient ECG changes, particularly QT prolongation, Syrup of ipecac itself can be both neurotoxic and cardiotoxic with intravenous odansetron administration. As ondansetron and caution is advised anytime it is used. Emetine, the active treats the symptom, not the cause of nausea, assessment and ingredient in syrup of ipecac, is part of a mixture of alkaloids treatment of the underlying cause is imperative. obtained from the plant Rubiaceae (Cephalus ipecacuanha). Cannabinoids (synthetically produced THC, such as the Emetine is derived from tyrosine, the intermediary of do pamine, type found in marijuana) have two therapeutic advantages. which explains its effects upon the heart and brain. First, cannabinoids are antiemetic. Second, cannabinoids The delay between the onset of symptoms from a poison stimulate appetite and reduce anorexia. This advantage can and the onset of action of the syrup of ipecac is a concern for be critical when treating patients who are cachetic secondary most Paramedics. If there is any possibility that the toxin can to acquired immunodefi ciency syndrome or chemotherapy.66 induce drowsiness or unconsciousness before the ipecac can take effect, then the ipecac should be withheld. For this rea- Antidiarrheal son, the routine use of syrup of ipecac is not recommended by To be medically accurate, diarrhea is not loose watery stool, the American Academy of Clinical Toxicology.65 but rather a frequent passage of loose watery stool. Certain populations, such as the very old and very young, are at risk for dehydration from diarrhea. Chronic diarrhea (diarrhea that lasts for more than one week) can be indicative of intes- Street Smart tinal infections such as amebic dysentery. Acute diarrhea can be indicative of toxin ingestion and bacterial infection, such The American Academy of Pediatrics no longer as salmonella or escherichia coli. advocates the civilian use of syrup of ipecac and In many cases, resolution of the underlying cause will alleviate the symptom. In cases where more immediate relief encourages that all syrup of ipecac be discarded. is sought or where the patient expects a short course of ill- Syrup of ipecac should only be used, in the hospital ness, then antidiarrhea agents are available. setting, under the direct orders of a physician. Absorbents Absorbents essentially coat the bowel wall, preventing inter- action of the intestine and bacteria or toxin, thereby stopping Antiemetics intestinal irritation and subsequent diarrhea. An example of Unremitting vomiting (e.g., from chemotherapy) can be debil- an absorbent antidiarrheal agent is bismuth subsalicylate. itating and lead to potentially life-threatening dehydration This bismuth preparation also contains salicylate, the active and hypovolemia. The majority of antiemetics work centrally, ingredient in aspirin, and can increase bleeding times. in the brain, to control the nausea that leads to vomiting. This Another example of an absorbent agent commonly used area, called the chemoreceptor trigger zone (CZT), contains by Paramedics is activated charcoal. Activated charcoal, a sensory nerves that detect poisons and |
the like in the blood. fi nely pulverized form of charcoal, absorbs the toxins until The CTZ then triggers the emetic center in the brainstem passage out of the intestine. To aid excretion, an indigestible to induce vomiting. This primitive protective mechanism is osmotic agent such as sorbitol is added. most effective with ingested toxins. Opioids Mechanism of Action Paregoric and tinctures of opium have been used as antidi- The mechanism of action of an antiemetic generally involves arrhea agents for centuries. However, recent concern about blocking a receptor (an antagonist) along the neuromuscu- the addictive quality of these medicines has brought about lar chain that leads to vomiting. Dopamine receptors, located a decrease in their use. Nevertheless, these opioids remain within the CTZ, can be blocked by dopamine antagonists. highly effective in the control of diarrhea. 704 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Loperamide, a synthetic opioid, decreases the peristalsis Precautions associated with diarrhea and permits reabsorption of water. Laxatives should not be routinely used to treat abdominal This prescription medication has a duration of action of over pain thought to be due to constipation. Undiagnosed abdomi- 24 hours, making it effective when traveling in remote or nal pain can be the presenting symptom for appendicitis, frontier areas. enteritis, and mesenteric infarction. Laxatives Older patients are frequently plagued by constipation as their Drugs That Are Used to Treat gastrointestinal tracts slow. In some cases, constipation can Bleeding Disorders lead to life-threatening small bowel obstruction. There are numerous causes of obstruction, but the effect is the same: The origins of bleeding disorders can be genetic (e.g., hemo- blockage of the intestinal tract. philia), disease-induced (e.g., disseminated intravascular coag- There are as many treatments for constipation as there ulation), or iatrogenic (e.g., heparin infusion). Regardless of are causes of constipation. Treatments for constipation can be the etiology the result is the same: a coagulopathy (defect in organized into broad classifi cations based upon the mecha- blood clotting). Consequently, the patient either clots too much nism of action. or bleeds too much. Drugs that affect blood clots (antithrombolytics and Saline Laxatives antifi brinolytics) were discussed in Chapter 30. Treatment of bleeding disorders revolves around either use of antagonists As soluble salts, these laxatives dry the water in the intestinal that interfere with anticoagulant medication or replacement tract via osmosis. The result is an increased fecal mass and of missing coagulation factors. stimulation for evacuation. Many of these saline laxatives Anticoagulants (such as warfarin) antagonize the fat- contain other minerals that may have added side effects. An soluble vitamin K, an essential cofactor in the coagulation example of a commonly used saline laxative is magnesium cascade. In some instances, the administration of vitamin K hydroxide, otherwise known as milk of magnesia. It can have overcomes the warfarin dose and re-establishes normal clot- a toxic effect on the kidneys. Others high in sodium compli- ting. Unfortunately, vitamin K is slow acting and can take cate the management of a patient’s heart failure or hyperten- up to 24 hours to be effective.67 This single quality makes sive control. vitamin K less useful in an emergency. Other anticoagulant antagonists work in direct opposi- Stool Softeners tion to the action of the fi brinolytics. Fibrinolytics act by Stool softeners act as a wetting agent, softening the fecal mass encouraging plasminogen activators to degrade fi brin. These until it can be passed. An example of a commonly prescribed anticoagulant antagonists (such as aminocaproic acid) inhibit stool softener is docusate. Docusate is often given to post-MI plasminogen activators. patients to prevent straining during bowel movements and the Heparin, a commonly prescribed anticoagulant, is subsequent vasovagal stimulation that occurs. formed in the liver, lungs, and intestinal lining. It produces its anticoagulant effect by binding with naturally occurring Bulking Agents antithrombin III and inactivating several factors in the coagu- lation cascade. Bulking agents, such as psyllium, absorb water from the The heparin antidote, protamine sulfate, is a protein fecal fl ow, increasing the volume of the feces and distend- obtained from the sperm of salmon that has an ability to inter- ing the bowel. The distended bowel is now encouraged to fere with the heparin-antithrombin III complex and thereby empty refl exively. prevents anticoagulation. Stimulants Antihemophilic Drugs Stimulants act directly upon the nervous control of the bowel, Uncontrollable bleeding secondary to a minor injury can be increasing peristalsis and bowel emptying. Stimulants, such life-threatening to a patient with hemophilia. Born with an as senna, can also produce abdominal cramping and pain. inability to produce one of the protein-clotting factors in the Senna tea, an old world remedy, is made from an infusion of blood, these patients may have excessive bleeding into the leaves of the Cassia plant into a tea. joints, bladder, and brain.68 The most common hemophilia (hemophilia A) is a defi - Lubricants ciency of factor VIII or the antihemophiliac factor (AHF). Lubricants aid the naturally occurring mucus to coat the feces Administration of cryoprecipitated AHF, prepared by rapid for an easier bowel movement. Many of these oil-based lubri- freezing and thawing of fresh plasma, is useful during an cants can also block absorption of fat-soluble vitamins, such emergency. As a glycoprotein, AHF is needed to transform as vitamins A, D, E, and K. prothrombin into thrombin. Pharmacological Therapeutics for Medical Emergencies 705 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Following AHF administration, it is common to admin- poorly absorbable ferrous carbonate. Other nutrient supple- ister anti-inhibitor coagulant complex. Anti-inhibitor coagu- ments used to treat various types of anemia include folic acid lant complex is also obtained from plasma and is often used and cyanocobalamin (vitamin B12). Vitamin defi ciencies can preoperatively for those with factor VIII defi ciency. occur as a result of poor diet and are often seen in patients Similarly, factor IX complex is administered to patients with alcoholism. with hemophilia B (Christmas disease) to prevent or con- trol bleeding. Drugs That Are Used to Treat Psychiatric Disorders In the past, the diagnosis of a psychiatric illness would bring Street Smart out images of raving mad lunatics locked in an insane asylum forced to undergo bizarre medical treatments, such as frontal Absorbable gelatin sponges, fi lm, powder, and lobotomy and straitjackets. Historically, mentally ill patients oxidized cellulose gauze are moving out of the were warehoused in public mental hospitals with deplorable health and sanitation conditions. Documentaries, such as the operating room and into the street. These topical one on Millbrook, brought these appalling conditions to light hemostatic agents are capable of absorbing blood in and efforts were made to change conditions and the therapeu- large quantities and encouraging clot formation at the tic approach. Psychiatrists, encouraged by the effectiveness bleeding site. of antibiotics, turned their attention to medications. They were not disappointed. The impact of the fi rst tranquilizer (chlorpromazine) in the 1950s cannot be overstated.71 Patients, who were previ- Anemia ously labeled dangerous and uncontrollable, could be tran- Anemia is not a disease. More accurately, anemia is a symp- quilized, treated, and, in some cases, allowed to lead a normal tom of other diseases that involves the body’s inability to public life. form adequate red blood cells. In most instances, anemia is The development and widespread use of these psychi- the result of either a dietary defi ciency of needed nutrients or atric medications led to the widespread deinstitutionaliza- poor absorption of those needed nutrients. tion of hundreds of psychiatric patients, It also prompted a In some instances, the anemia is a quasi-anemia (i.e., complete change in the focus of mental health medicine away one induced by a temporary state such as pregnancy). In from institutionalization and toward community-based treat- other instances, chronic blood loss, infection, cancer, or ment centers. drug-induced bone marrow depression can produce anemia. Psychosis Regardless of the cause, the patient has a less than normal hemoglobin (Hb) concentration from either fewer circulat- A large number of mental illnesses can be grossly catego- ing red blood cells or a low hemoglobin content in those red rized under the label of schizophrenia, anxiety disorders, and blood cells. depression. Medications to treat patients who suffer from Treatment of anemia is usually geared toward providing each of these mental illnesses are described further. supplementary nutrition while eliminating or treating the root The patient with a diagnosis of schizophrenia has dem- cause of the anemia. A common anemia, iron-defi ciency ane- onstrated disturbances in thought. Hallucinations, particu- mia, can occur from chronic blood loss, including menses. larly audible hallucinations and delusions, plague the patient. Iron, which is essential for the red blood cell to carry oxygen, The outcome of this deranged thinking, and what usually is prescribed to those patients suffering from a defi ciency. brings the patient to the Paramedics’ attention, is an inability Iron stored in the intestinal mucosa can also be lost in gastro- to perform the routine activities of daily living (ADL) such as intestinal disease. bathing and clothing oneself. If children accidentally ingest iron supplements, it can turn into a medical emergency.69 As the iron is absorbed, Drugs That Are Used to Treat Psychosis the child can become toxic and will have diffuse abdominal Antipsychotic medications help provide the patient with signs, such as cramps.70 Unfortunately, the symptoms sub- symptomatic relief from the frightening hallucinations and side within 24 hours and the patient appears fi ne, which may deranged thoughts caused by schizophrenia. While these prompt them not to seek further treatment. Subsequently, medications induce a tranquil state in the patient, allowing about 48 to 72 hours later, an acidosis occurs that can lead to the patient to cope with the illness, they are not a cure for pulmonary edema, convulsions, and hyperthermia. schizophrenia. Therefore, in order to maintain control of the If ferritin intoxication is suspected, the Paramedic may disease patients must remain on the drug for long periods of induce vomiting using syrup of ipecac and/or lavage with time. Setbacks for these patients are frequently the result of sodium bicarbonate solution, which converts the ferritin into poor compliance with prescribed medications and subsequent 706 Foundations of Paramedic Care Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. breakthrough psychosis that is often manifested in aggressive Fortunately, most of these symptoms are self-limited and or combative behaviors. diminish with the termination of the medication. The phenothiazines, the major class of antipsychotic medications, are thought to block dopamine receptors within Anxiety the limbic portion of the brain. (The limbic system is the seat of emotions.) This blockade results in a reduction in halluci- As a class, sedatives affect the limbic system and thus emo- nations and subsequent agitation. However, it should be noted tions. Sedatives effectively reduce anxiety (i.e., anxiolytic) that the phenothiazines do not depress the patient’s intellec- as well as induce sleep (i.e., hypnotic). Some of the most tual function or native intelligence. commonly known sedatives are the barbiturates and the ben- Phenothiazines can be further broken down, according zodiazepines. When used early, the barbiturates can create to chemical makeup, into three subcategories. The fi rst phe- an anxiolysis, even in small doses (doses too low to induce nothiazines were all aliphatic phenothiazine derivatives (e.g., respiratory depression). The |
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