may also be used in conjunction with albuterol but should not be used alone. Although both the multidose inhaler and the nasal spray formulations of ipratropium contain an ingredient that may cause an allergic reaction in patients with known peanut allergies (soy lecithin, used to keep the medication in suspension), the nebulized formulation typically used by EMS and emergency departments lacks this ingredient [3]. All of the aforementioned drugs may also be used in children, but, as with any pediatric medication, dosages must be calculated based on the child’s weight (Table 21.1).
Local allergic reactions can progress from one body system to anaphylaxis involving several systems, including skin, respiratory, and circulatory. If untreated, this can progress to anaphylactic shock with circulatory collapse and hypotension. Epinephrine is the first‐line medication for a patient with severe allergic reactions or anaphylaxis and should be given as soon as possible. Delaying administration has been associated with poor outcomes. While generally safe, caution may be advised in patients with known coronary artery disease or in cases with life‐threatening tachydysrhythmias. Infrequently, myocardial ischemia and infarction have been reported, especially if administered IV [15]. Two different concentrations of epinephrine may be used, and the clinician must be attentive to using the proper dosage and formulation when administering it. In adults, 0.3 mL of epinephrine 1:1,000 solution can be given subcutaneously or intramuscularly except when the patient is on the verge of cardiovascular collapse. The intramuscular route at the lateral thigh is preferred. This route produces higher peak plasma concentrations in less time than subcutaneous injection or intramuscular injection in the deltoid [16]. Faster absorption from intramuscular injection in the thigh is thought to be due to the increased vascularity of the vastus lateralis muscle [16].
Table 21.1 Pediatric anaphylaxis medication doses
| Drug | Weight‐based dose |
|---|---|
| Epinephrine | 1:1000 IM (0.3 mL maximum) 1 mL of 1:10,000 mixed with 10 mL NS 0.5 mL of 1:1000 in 2.5 mL NS nebulized |
| Diphenhydramine | 1 mg/kg IM/IV/IO/PO (max. 50 mg) |
| Methylprednisolone | 1‐2 mg/kg |
| Famotidine | 0.5 mg/kg to max. of 20 mg IV/IO |
| Ranitidine | 2‐4 mg/kg to max. of 50 mg IV/IO |
IM, intramuscular; IO, intraosseous; NS, normal saline; PO, by mouth.
If the patient is hemodynamically unstable, 1 mL of epinephrine 1:10,000 mixed with 10 mL of normal saline can be given slowly by IV or intraosseous push over 5‐10 minutes. Caution is advised. On the one hand, epinephrine given intravenously to a patient who is not in cardiac arrest can be risky, resulting in hypertension or myocardial ischemia [15]. On the other hand, it can be lifesaving and should not be delayed in the case of a hemodynamically unstable or “crashing” patient. Epinephrine may also be nebulized by placing 0.5 mL of 1:1000 solution in 2.5 mL of normal saline.
If the patient is hypotensive, rapid fluid resuscitation with 1‐2 L of normal saline (20 mL/kg in children) is indicated in addition to the aforementioned medications. Patients often will become intermittently hypotensive and require multiple fluid boluses and additional medications, so frequent monitoring of vital signs is imperative. At least two large‐bore IV lines are desirable.
Localized angioedema is typically treated as an allergic reaction with antihistamines and steroids, along with epinephrine in severe cases. However, little actual benefit or significant improvement has been shown with these medications. As with medication‐induced angioedema, hereditary angioedema is generally not responsive to antihistamines, steroids, or epinephrine, although they are routinely administered [3]. The mainstay of treatment is supportive, with ongoing monitoring and early consideration of intubation if there is airway compromise.
EMS clinicians should anticipate that any airway intervention for a patient with an allergic reaction or angioedema is likely to be especially difficult. The edema can extend to the glottic and subglottic regions and not be externally visible. The only clue the clinician might have is that the patient’s voice is hoarse or different from normal. Oral‐pharyngeal, glottic, and subglottic edema can obscure anatomical landmarks and decrease airway caliber to alter the effective sizes of airway tools. If bronchospasm is present, ventilation before and between intubation attempts may be difficult, adding pressure for expedient success. Thus, it is imperative that the clinician is prepared for a difficult airway with airway skills, adjuncts, and emergency rescue devices and techniques, such as cricothyrotomy, especially if rapid sequence intubation is also being performed [17].
Special considerations
Several points may be helpful to remember when responding to allergic reactions in the field. In general, stinging insects, especially Hymenoptera, can cause systemic allergic reactions and anaphylaxis, but these reactions are rare with biting insects [18]. There is a greater chance of a systemic reaction with multiple stings. One should remember that the clinical presentation may be quite varied and the history may be vague. Patients may have significant symptoms yet not be able to recall exposure to a specific allergen. In cases such as these, interventions necessary for stabilization should take priority over identification of the culprit allergen. In cases of true anaphylaxis, the axiom “stabilize first, diagnose later” should be followed. After emergency interventions are completed, care should be taken to frequently reassess the patient and document pertinent findings. This may be the first clue that an allergic reaction is present if the patient does not relate an exposure or inciting event. Symptoms can be exacerbated by fear, exercise, alcohol intake, heat exposure, or underlying cardiovascular disease. The clinician should be careful not to become complacent or attribute clinical signs and symptoms solely to these conditions, as allergic reactions can progress insidiously.
Anaphylaxis to stings can occur abruptly years after the first exposure, even without intervening stings. Furthermore, approximately 20% of patients exhibit biphasic anaphylaxis responses where the initial symptoms resolve and there is a symptom‐free period before the onset of the late phase reaction 4‐6 hours after the initial symptoms began. The symptoms of the late reaction can be markedly different from those of the initial reaction, and can be life‐threatening even if those of the initial reaction were not. It is nearly impossible to predict which patients will exhibit this biphasic response. This could result in repeat EMS calls for allergic reactions featuring substantially different symptoms, particularly if a patient refuses transport initially or is seen and discharged from an ED before the late phase reaction occurs [19].
If the patient experiencing a severe allergic reaction or anaphylaxis routinely takes beta‐blocker medications, the action of epinephrine may be blunted. Glucagon may be given in 1 mg increments by any parenteral route to overcome the effects of beta‐blockade. Cutaneous symptoms are the most common clinical response in both adults and children. Hypotension is uncommon in children, but it has been reported in up to 60% of adults with significant allergic reactions. Patients will sometimes complain of a prodrome of chest pain or shortness of breath before development of a more generalized severe allergic reaction.
EMS clinicians should have a high index of suspicion when responding to calls of shortness of breath or chest pain. Attempt to ensure there was no contact with an allergen that could cause the symptoms. For instance, allergy‐producing contrast media are frequently given in free‐standing imaging centers. Consider the possibility of allergic reactions and anaphylaxis when responding to calls of shortness of breath or chest pain at these facilities [20]. Anaphylaxis should be one of the etiologies considered when responding to cardiac arrests in outdoor areas, such as golf courses, as the patient may have been stung or bitten before the cardiac arrest.
Although bites from a Gila monster