Epidemiology and clinical predictors of biphasic reactions in children with anaphylaxis

Abstract
Background
Epidemiologic data regarding biphasic reactions in children with anaphylaxis are sparse.

Objective
To investigate the incidence and clinical predictors of biphasic reactions in children presenting to the emergency department (ED) with anaphylaxis.

Methods
A health records review of ED visits at 2 large Canadian academic pediatric EDs was conducted. All visits that satisfied anaphylaxis diagnostic criteria of the National Institute of Allergy and Infectious Diseases and the Food Allergy and Anaphylaxis Network were included. Predictors of biphasic reaction were analyzed using univariate and multiple logistic regression analyses.

Results
Of 1,749 ED records reviewed, 484 visits met the study inclusion criteria. Seventy-one patients (14.7%) developed biphasic reactions. The median age was 6 years (interquartile range 2.7–10.1) and 51 (71.8%) were boys. Forty-nine of the 71 (69%) delayed reactions involved respiratory and/or cardiovascular manifestations and 35 (49%) were treated with epinephrine. Five independent predictors for biphasic reactions were found: age 6 to 9 years (odds ratio [OR] 3.60, 95% confidence interval [CI] 1.5–8.58), delay in presentation to the ED longer than 90 minutes after the onset of the initial reaction (OR 2.58, 95% CI 1.47–4.53), wide pulse pressure at triage (OR 2.92, 95% CI 1.69–5.04), treatment of the initial reaction with more than 1 dose of epinephrine (OR 2.7, 95% CI 1.12–6.55), and administration of inhaled β-agonists in the ED (OR 2.39, 95% CI 1.24–4.62).

Conclusion
Biphasic reactions seem to be associated with the severity of the initial anaphylactic reactions. We identified clinical predictors that could ultimately be used to identify patients who would benefit from prolonged ED monitoring and enable better utilization of ED resources.