Abstract
Objective Current guidelines recommend that anaphylactic patients be observed for 4-6 hours following epinephrine administration to monitor for biphasic reactions. There is conflicting data regarding the efficacy of these guidelines and the prevalence of biphasic reactions among the pediatric population. This retrospective study aimed to investigate the appropriateness of these guidelines through evaluation of observation periods and patterns of biphasic reaction development among pediatric anaphylactic patients at a single-institution ED. Methods Patients less than 18 years of age who presented to the ED of a tertiary academic medical center between 2017 and 2022 and were treated with epinephrine for anaphylaxis were included in the study. The frequency and timing of biphasic reactions were observed. Duration of ED observation, time between symptom onset and first dose of epinephrine, number and category of anaphylactic symptoms, and allergen type were compared between patients who did and did not experience a biphasic reaction. Additional variables analyzed included persistence of anaphylactic symptoms, additional doses of epinephrine, and adjuvant medications. Contingency tables and two-sample t-tests were used to compare categorical and continuous variables, respectively, between those who did and did not develop a biphasic reaction. Results A total of 292 patients met the inclusion criteria and were included in the analysis. All patients were observed in the ED for a mean of 233.1 minutes. Ten patients (3.4%) developed a biphasic reaction. Six had a reaction within 150 minutes of initial symptom resolution, and four developed one after discharge, within 10 to 33 hours following symptom resolution. There was no significant difference in the length of time observed in the ED (p=0.98) or from symptom onset to the first epinephrine dose (p=0.90) between groups. Presenting with respiratory symptoms was associated with persistent anaphylactic symptoms despite epinephrine administration (p=0.01). Patients with symptoms involving at least two organ systems were 3.45 times more likely to experience persistent symptoms post-epinephrine than those with involvement of only one organ system (OR=3.45; CI: 1.28-9.30). Allergen type, anaphylactic symptoms, or the number of organ systems involved were not linked to developing a biphasic reaction or the need for additional epinephrine doses. Conclusions The patients who developed a biphasic reaction did so either shortly following initial symptom resolution or many hours past the recommended observation period. Extending the observation period of patients within reasonable parameters would not have reduced the number of patients who experienced a biphasic reaction after discharge. The results of this study support potentially adopting a more individualized approach to anaphylaxis management following epinephrine administration. Shortening the observation period for patients at low risk for biphasic reactions could reduce the patient burden on EDs without negatively impacting patient outcomes. Although no significant risk factors for biphasic reactions were identified in this study, closer monitoring of patients with respiratory symptoms and/or involvement of a greater number of organ systems may help mitigate the number of patients who experience persistence of anaphylaxis despite treatment.