Background One of the main reasons for hospital admission once a child has been stabilized following anaphylaxis is to monitor for a biphasic reaction. However, only a small percentage of anaphylactic episodes involve biphasic reactions that would benefit from admission. Identification of predictive factors for a biphasic reaction would assist in determining who may benefit from prolonged observation.
Objective To determine predictive factors for biphasic reactions in children presenting with anaphylaxis.
Methods This was a retrospective study of children presenting with anaphylaxis to a major paediatric emergency department over a 5-year period.
Results There were 95 uniphasic (87%), 12 (11%) biphasic and two protracted reactions (2%). One child with a protracted reaction died. For the management of the primary anaphylactic reaction, children developing biphasic reactions were more likely to have received >1 dose of adrenaline (58% vs. 22%, P=0.01) and/or a fluid bolus (42% vs. 8%, P=0.01) than those experiencing uniphasic reactions. The absence of either factor was strongly predictive of the absence of a biphasic reaction (negative predictive value 99%), but the presence of either factor was poorly predictive of a biphasic reaction (positive predictive value of 32%). All biphasic reactors, in which the second phase was anaphylactic, received either >1 dose of adrenaline and/or a fluid bolus.
Conclusions Children who received >1 dose of adrenaline and/or a fluid bolus for treatment of their primary anaphylactic reaction were at increased risk of developing a biphasic reaction.