However, anaphylaxis may present as an acute cardiac or respiratory event, or with hypotension as the only manifestation.⁸ The onset of symptoms varies from a few seconds or minutes after contact with the elicitor to several hours (depending on the route of exposure and degree of sensitization),¹⁶ but the majority of events occur within two hours of exposure.¹⁸

The faster anaphylaxis develops, the more likely the reaction is to be severe and potentially life-threatening.⁸ A pattern of biphasic anaphylaxis has also been described in which symptoms recur after the apparent resolution of the initial episode, which merits treatment similar to the initial episode.^8,19

Anaphylaxis is estimated to be fatal in 0.7% to 2% of cases.^20,21 Death can occur within minutes of the onset of symptoms.⁷ Deaths due to anaphylaxis are usually attributed to respiratory obstruction or cardiovascular collapse, or both.^11,22

Anaphylaxis Triggers

Food is the major cause of anaphylaxis in the United States,² with recent data associating severe reactions, most commonly in children, with allergy to tree nuts, peanuts, shellfish, soy, and fin fish.²³ Medicines are among the leading causes of anaphylaxis, with beta-lactam antibiotics most commonly implicated.^{8,10,15,24,25} Anaphylactic reactions to insect stings have occurred in 1% of children and 3% of adults^8,26,27 and are associated with a high probability of recurrence.²⁸

Other important causes of anaphylaxis include latex allergy^15,29 and perioperative anaphylaxis.^8,10,30

Managing Anaphylaxis

Prompt recognition and management of the signs and symptoms of anaphylaxis are the key to managing anaphylaxis.⁸

Immediate interventions for patients experiencing anaphylaxis include assessment of airway and breathing, circulation, and level of consciousness; administration of intramuscular epinephrine; and placement of the patient in a supine position in order to slow the progression of hemodynamic compromise.⁸

Intramuscular (IM) epinephrine injection is first-line treatment in all cases of anaphylaxis.^4,8,22 Along with the use of oxygen, is considered the most important therapeutic agent administered for anaphylaxis.⁸ The appropriate dose of IM epinephrine should be administered immediately at the onset of symptoms, even if the diagnosis is uncertain.^4,8,22 At a concentration of 1:1000, the recommended dose of epinephrine via auto-injector is 0.15 mg for patients weighing 10-25 kg and 0.3 mg for patients weighing greater than 25 kg.⁴

Epinephrine may be administered every 5 to 15 minutes as necessary, and if symptoms progress or recur (i.e., biphasic reaction), repeat epinephrine dosing is recommended over adjunctive treatments.^4,8 Although up to a third of patients require more than one dose,³¹ additional measures (intravenous epinephrine, volume replacement, vasopressors) may be needed in patients not responding to multiple doses.⁸