Epidemiology and Clinical Predictors of Biphasic Reactions in Children with Anaphylaxis
The Article: Alqurashi W et al. Epidemiology and clinical predictors of biphasic reactions in children with anaphylaxis. Ann Allergy Asthma Immunol 115 (2015): 217-223.
The Idea: Anaphylaxis constitutes a significant percentage of visits to pediatric emergency rooms (2-4/1000 visits), however, there is a dearth of data about the true prevalence and epidemiology of anaphylactic reactions. While patients presenting with anaphylaxis are generally observed in the emergency department for development of a biphasic reaction, there is no common consensus on the appropriate observation period. The authors felt this lack of consensus may be reflecting an inability to predict which subset of patients will go on to have a biphasic reaction and therefore merit prolonged observation or admission. In this study, the authors conducted a retrospective chart review to identify the epidemiology and clinical predictors of biphasic reactions in children presenting with anaphylaxis.
The Study: The study was a retrospective chart review conducted at 2 pediatric tertiary care centers in Canada in 2010. Included: Patients <18 whose visits met the 2006 National Institute of Allergy and Infectious Disease, Food Allergy and Anaphylaxis network diagnostic criteria identified by ICD code “anaphylactic shock due to _____,” adverse food reactions, and “allergy, unspecified” Excluded: Patients who did not meet the diagnostic guidelines, anaphylaxis in the context of suicide attempt or intoxication, anaphylaxis conflated by another diagnosis such as systemic mastocytosis or food poisoning, reactions during a clinic visit or hospitalization Data extracted included triage vitals, history of allergic reactions or atopy, therapeutic interventions required during that visit including epinephrine, steroids, and antihistamines. Biphasic reaction was defined as greater than 1 hr of resolution of symptoms between reactions without re-exposure, no requirement for additional tx during that hour and the second episode of anaphylaxis had to be sufficiently severe to require therapeutic intervention. If patients went on to have a biphasic reaction or revisited the hospital within 72 hours, data collected included time of onset, manifestations and therapeutic interventions required.
Results: 1, 749 patients were identified with anaphylactic reactions. 504 met study inclusion criteria, of those 504, 484 were eligible for the study. 71/484 or 14.7% percent developed biphasic reactions. When compared to patients with uniphasic reactions, those with biphasic episodes had a longer time time from onset of reaction to ED presentation (96 vs 72 minutes) and a shorter time from triage to physician assessment (13 vs 24 minutes) as well as a longer length of ED stay (5.9 vs 4.5 hours). Independent predictors of biphasic episodes included age 6-9, a delay in ED presentation of >90 minutes from onset of initial reaction, wide pulse pressure at triage, treatment with >1 dose of epinephrine and administration of inhaled beta-agonists in the ED. The Takeaway: This paper identifies several independent predictors of development of biphasic reactions in patients presenting with anaphylaxis. Several of these independent predictors appear to correlate with severity of presentation including wide pulse pressure and requirement for multiple rounds of epinephrine. Patients with biphasic reactions were also evaluated more rapidly after triage, suggesting that their initial vital signs or appearance may have merited a greater concern about the severity of their illness. In general, it seems unlikely that those clinical predictors would be practice changing as most providers would tend toward prolonged observation or admission for patients presenting with anaphylaxis with evidence of respiratory involvement or unstable vital signs. However, the association between delay in ED presentation > 90 minutes and biphasic reaction is useful in identifying patients who may benefit from prolonged observation in the ED and may not otherwise merit admission.