Biphasic Anaphylaxis in Urban Emergency Patients: A Prospective Cohort Study
Nawat Heerungeeragon, MD1, Adisak Nithimathachoke, MD1
Affiliation : 1Department of Emergency Medicine, Faculty of Medicine Vajira Hospital, Navamindradhiraj University, Bangkok. Thailand
Background: Despite the rising rates of anaphylaxis globally, the optimal observation period in emergency departments (EDs) remains unclear. A wide range of biphasic reaction prevalence (0.5% to 21%) and onset (0.2 to 72 h) has been reported, leading to unnecessary prolonged stays, emergency room crowding, and anxiety for patients. Thus, risk stratification could offer potential solutions.
Objective: To evaluate the incidence and onset of biphasic anaphylaxis in emergency patients.
Materials and Methods: This prospective study included patients with anaphylaxis aged ≥18 years who were admitted to an urban Thai tertiary ED between July 1, 2022, and December 31, 2023. Patients were discharged after 6 h and received phone follow-ups at 12, 24, 48, and 72 h. The patients with asthma or chronic obstructive pulmonary disease were excluded.
Results: 76 patients were included in the present study. Among them, 2 (2.63%) patients experienced biphasic anaphylaxis at 10 and 14.5 h after the initial resolution without requiring hospitalization or additional resuscitation. No biphasic reactions occurred within the 6 h observation period. Five patients returned to the ED within 24 h for nonanaphylactic urticaria. Food was the most common trigger of anaphylaxis, and urticaria was the dominant manifestation. The median time from symptom onset to ED arrival was 1.25 h (0.5 to 3 h). The mean time to epinephrine was 1.3 h (0.6 to 3.1 h). All participants received one dose of epinephrine, dexamethasone, and antihistamine simultaneously in the ED. Prednisolone and antihistamines were prescribed as home medications in almost all patients.
Conclusion: The present study showed that biphasic anaphylaxis is relatively rare with good outcomes in patients with uncomplicated anaphylaxis, indicating that a shorter observation period in EDs may suffice as a safe measure in this population.
Received 15 May 2024 | Revised 16 October 2024 | Accepted 28 November 2024
Keywords : Anaphylaxis; Biphasic anaphylaxis; Incidence; Onset; observation period; Mortality
