Evaluating Practice Patterns of Observation Periods Status Post Epinephrine Administration for Anaphylaxis

Anaphylaxis is a life-threatening emergency requiring use of epinephrine and subsequent observation period. The National Institute of Allergy and Infectious Disease (NIAID) suggests that patients with resolved anaphylaxis should be observed for at least 4-6 h to monitor for biphasic reactions.

The primary objective was to investigate practice patterns in observation time in the emergency department (ED) for anaphylaxis after epinephrine administration. Secondary objectives included the adjunct medical management, allergens, and frequency of biphasic reactions.

A retrospective chart review from January 2017 to September 2022. Patients ≥ 18 years of age who presented with anaphylaxis requiring epinephrine administration and a documented observation period after, qualified. There were 1751 male and female patients identified; only 488 met criteria. There were 1263 patients excluded for no epinephrine administration.

The median number of minutes observed in the ED after epinephrine administration for all patients was 235 min (95% confidence interval [CI] 251.50-285.16, SD = 187.28); 21 patients (4.29%) experienced a biphasic reaction. Patients with biphasic reactions were observed for a median of 451.38 min (95% CI 320.29-582.47, SD = 297.99). Patients without a biphasic reaction were observed for a median of 262.13 min (95% CI 245.43-278.83, SD = 181.47, p < 0.05). No statistically significant relationship was found between the timing of epinephrine administration after symptom onset and frequency of biphasic reaction (p = 0.57).

Observation time after epinephrine administration on the index ED visit was comparable with the NIAID-suggested 4 to 6 h. Patients with biphasic reactions were observed longer than those without a biphasic reaction.