Biphasic Anaphylaxis: A Review of the Incidence, Characteristics and Predictors

Abstract

While it has been recognized for over a quarter century that anaphylactic reactions have the potential to follow a biphasic course, reports on the incidence of biphasic anaphylaxis are conflicting, and the search for reliable predictive factors of such responses has been challenging. Further adding to the complexity of this clinical entity are the widely variable durations of the asymptomatic window, and the similarly variable reports on second phase severity. This review aims to provide the health care professional with a better understanding of the true incidence, nature, and risk factors for this type of reactivity by consolidating and summarizing the available literature on the topic of biphasic anaphylaxis. As our body of evidence builds, patterns are emerging to suggest that those patients with an initial presentation requiring more than one dose of epinephrine, those who have life-threatening initial presenting features, and those who otherwise take longer to stabilize, are in this higher risk group, and would be more likely to benefit from prolonged in hospital observation. Conversely, patients who respond rapidly to the immediate administration of epinephrine may be at lower risk, but this finding requires confirmation by others. Further prospective evaluations of biphasic anaphylaxis will greatly aid our understanding of this condition.

Epidemiology and clinical predictors of biphasic reactions in children with anaphylaxis

“…38 The association of a biphasic reaction with the severity of the initial reaction has just recently emerged as a potential risk factor. 39 23,34 Although these studies provide some insight about this association, the reported cases are too small to reliably predict this association. Also, the definition of severity used in these studies is inconsistent and not based on objective scoring.…”

Anafilaxia: dados de um registro de pacientes atendidos em um serviço especializado

“…O tempo entre a exposição ao desencadeante e a reação anafilática variou, e na maioria das vezes foi de no máximo 30 minutos. As evidências disponíveis demonstram que após a resolução do quadro anafilático inicial, 10 a 20% dos pacientes podem ter uma nova onda de manifestações, mesmo na ausência de nova exposição ao desencadeante -reação bifásica 28 , e frequentemente ocorrem na anafilaxia por alimentos 23 . Em nosso estudo apenas um paciente (0,6%) teve anafilaxia bifásica, e a suspeita é que tenha sido desencadeada por droga.…”

Epidemiology of anaphylaxis

“…[72][73][74] It has been noticed that between 10 to 20% of anaphylactic patients may have biphasic reactions, characterized by a second manifestation generally 4 to 6 hours after the first one. 75 However, this second occurrence can happen as late as 78 hours after the first manifestation.…”