The 2015 study, led by the Children’s Hospital of Eastern Ontario (CHEO) Research Institute, looked at records on 484 anaphylaxis patients at two large pediatric emergency departments in Toronto and Ottawa. The researchers found that almost 15 percent of the children had a biphasic reaction, with most occurring within six hours of the start of the first reaction. At least half of these were serious and required treatment with epinephrine.
“The key message here for patients, parents, caregivers, teachers, and first-responder health professionals is: to prevent an anaphylactic reaction from worsening, administer epinephrine immediately after the onset of the early symptoms of an allergic reaction,” said Dr. Waleed Alqurashi, an emergency medicine physician at CHEO, and assistant professor at the University of Ottawa.
The team identified five predictors of biphasic reactions in children:
– A delay of more than 90 minutes in either: the administration of epinephrine to the child experiencing a severe reaction or delay in presentation to an emergency department. (The time frame is from the onset of the initial allergic reaction.)
– Wide (or high) pulse pressure during evaluation at hospital.
– More than one dose of epinephrine needing to be administered during the initial allergic reaction.
– Breathing distress the requires inhaled albuterol (salbutamol) in the emergency department.
– A higher incidence in children between 6 and 9 years old.
Alqurashi said children with severe initial reactions clearly “would benefit from a prolonged period of observation in the emergency department.” Conversely, he suggests that “children with mild allergic reactions, who do not match any of the identified predictors,” can probably go home sooner.
The study was published online in the Annals of Allergy, Asthma and Immunology in June 2015. While the researchers say it is one of the largest investigations of biphasic anaphylaxis to date, they say further study is needed to validate results. Adults can also have biphasic reactions, but this research only considered children.