Further Evaluations of Factors That May Predict Biphasic Reactions in Emergency Department Anaphylaxis Patients

Anne-Marie Irani

doi:10.1542/peds.2018-2420Y

S Lee, A Peterson, CM Lohse, EP Hess, RL Campbell. J Allergy Clin Immunol Pract. 2017;5(5):1295–1301

PURPOSE OF THE STUDY.

To evaluate variables to help in the identification of patients who are at an increased risk for biphasic anaphylactic reactions in the emergency department (ED).

STUDY POPULATION.

The study included 807 patients in the ED with a total of 872 ED visits for anaphylaxis. The median age was 34 years, with 58% female patients and 26% pediatric subjects <18 years of age. Food was the most common inciting trigger in 35% of patients, followed by drugs in 20% of patients and venom in 12% of patients; 22% of patients had an unknown trigger. At least 1 dose of epinephrine was administered in 54% of visits, and 90% of patients received systemic steroids.

METHODS.

This was an observational study of patients presenting to an academic ED from 2008 to 2015. Anaphylaxis cases were identified both retrospectively and prospectively on the basis of diagnostic criteria from the National Institute of Allergy and Infectious Diseases Food Allergy and Anaphylaxis Network. Biphasic reactions were defined as recurrent symptoms and signs of anaphylaxis occurring within 72 hours of the initial reaction without reexposure to the offending trigger.

RESULTS.

There were 36 visits (4.1%) that resulted in biphasic anaphylaxis, with a median time from the initial reaction of 3 hours (range: 0.5–44 hours). Of those, 17 visits (47%) required treatment with epinephrine. The use of steroids was not associated with biphasic anaphylaxis. Statistically significant variables included a history of anaphylaxis (odds ratio [OR]: 2.74; 95% confidence interval [CI]: 1.33–5.63), an unknown trigger (OR: 2.4; 95% CI: 1.14–4.99), and delayed administration of the first epinephrine dose 60 minutes after symptom onset (OR: 2.29; 95% CI: 1.09–4.79). The risk of a biphasic reaction was 1.6% in patients with none of these risk factors and 20% in patients with all 3 risk factors.

CONCLUSIONS.

The authors of this study report a rate of biphasic anaphylactic reactions of 4.1%, with almost half requiring treatment with epinephrine, indicating clinically significant reactions. A prediction model used to assist in identifying the risk of biphasic reactions was developed.

REVIEWER COMMENTS.

The current guidelines on anaphylaxis management from the Joint Task Force on Practice Parameters recommends an observation period of 4 to 8 hours. Further validation of risk factors for biphasic anaphylaxis would assist ED clinicians in customizing the length of optimal observation for individual patients. Of note, in this study, the need for prompt treatment of anaphylaxis with epinephrine is reinforced. The role of steroid treatment in the prevention of biphasic anaphylaxis remains undetermined and will require prospective trials involving a larger sample size.

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