Biphasic Allergic Reactions in ER Patients Interview with:
Brian Grunau MD
Emergency Physician, St. Paul’s Hospital
Clinical Assistant Professor, UBC Department of Emergency Medicine What are the main findings of the study?

Dr. Grunau: Among 2819 consecutive Emergency Department visits of patients with allergic reactions or anaphylaxis, five clinically important biphasic reactions were identified (0.18%; 95% confidence interval [CI] 0.07% to 0.44%), with two occurring during the ED visit and three post-discharge. There were no fatalities.  When examining patients who satisfied the definition for anaphylaxis and those who did not separately, clinically important biphasic reactions occurred in 2 patients (0.40%; 95% CI 0.07% to 1.6%) and 3 patients (0.13%; 95% CI 0.03% to 0.41%), respectively. Were any of the findings unexpected?

Dr. Grunau: We expected to identify biphasic reactions in the anaphylaxis group and that the incidence would be low.  We did not, however, expect to identify biphasic reactions in the patients who did not satisfy the definition for anaphylaxis on the index visit.  We also did not expect to identify biphasic reactions which occurred many days after the index visit (the longest duration was 143 hours). What should clinicians and patients take away from your report?

Dr. Grunau: Biphasic reactions are rare, however do occur and may take place many hours or days after the index visit.  Patients in our cohort who had a biphasic reaction after ED discharge appropriately presented back to the ED for treatment and there were no deaths.  Extended monitoring (for example, over four hours) after ED treatment appears to be unnecessary for the majority of patients whose symptoms have resolved.  A careful discussion on when to return to the ED and the importance of an epinephrine autoinjector, however, is essential before discharge. What recommendations do you have for future research as a result of this study?

Dr. Grunau: A prospective blinded randomized study examining the efficacy of various ED treatments in preventing biphasic reactions would be ideal, however with such a low incidence of reactions an extremely large sample size would be required.


Incidence of Clinically Important Biphasic Reactions in Emergency Department Patients With Allergic Reactions or Anaphylaxis
Brian E. Grunau, Jennifer Li, Tae Won Yi, Robert Stenstrom, Eric Grafstein, Matthew O. Wiens, R. Robert Schellenberg, Frank Xavier Scheuermeyer      

Annals of Emergency Medicine – 18 November 2013 (10.1016/j.annemergmed.2013.10.017)


Last Updated on December 4, 2013 by Marie Benz MD FAAD