Managing Anaphylaxis: Epinephrine, Antihistamines, and Corticosteroids: More Than 10 Years of Cross-Canada Anaphylaxis Registry Data

To evaluate the impact of prehospital treatment with epinephrine (Epi), antihistamines (AH), and/or corticosteroids (CS) on anaphylaxis management.Patients presenting with anaphylaxis to 10 Canadian and 1 Israeli emergency departments (EDs) between April 2011 and August 2022.This is a multicenter, ambispective observational study of children and adults presenting with anaphylaxis to the ED. A standardized survey documenting symptoms, triggers, and anaphylaxis management was completed. Anaphylaxis was defined as the involvement of 2 or more organ systems after exposure to a possible allergen, or hypotension after exposure to a known allergen. Additionally, uncontrolled reactions were defined as reactions needing 2 or more doses of Epi in the ED. The primary outcomes were uncontrolled reactions, no Epi use before arrival at the ED, the use of IV fluids in the ED, and hospital admission. Further, they assessed demographic factors, clinical characteristics of the reaction, comorbidities, daily medication use, and the administration of Epi, CS, and/or AH both in ED and in prehospital setting and anaphylaxis severity.There were 5364 cases of anaphylaxis identified; median age was 8.8 years, and 52.5% of patients reported a history of physician-diagnosed food allergy. The most common prehospital treatment was AH followed by Epi and short-acting β-agonists, representing 44.3%, 37.9%, and 6.8%, respectively. In the ED, reactions were treated with AH (51.8%), Epi (46.3%), and CS (40.1%). When combining prehospital and ED treatment, 76.7% of patients were treated with Epi. Only 4.66% of patients required 2 or more doses of Epi in the ED, and 5.34% of patients were admitted for their reaction. No fatalities occurred. Adjusted odds ratio (aOR) reveals that reactions were less likely to require intravenous fluid administration if prehospital Epi was administered (aOR, 0.9761 [0.9599–0.9925]). Reactions were more likely to cause hospital admission if prehospital CS were administered (aOR, 1.2328 [1.1814–1.2864]), however they were less likely in patients who received prehospital AH (aOR, 0.9634 [0.9493–0.9777]) and Epi (aOR, 0.9645 [0.9492–0.9800]).This study supports the prehospital use of Epi and displays a beneficial effect of AH. Further, the prehospital use of CS may have negative effects in anaphylaxis including higher risk of hospital admission and need for intravenous fluids.Prompt use of Epi is the first-line treatment of anaphylaxis. However, it is frequently replaced with AH or CS, despite little evidence to do so. Additionally, delayed Epi administration is a significant risk factor for biphasic and fatal anaphylaxis. The findings support that Epi should be used promptly in the treatment of anaphylaxis and further studies should be conducted to evaluate the potentially harmful effect of prehospital CS use on anaphylaxis.