SELECTED ARTICLES FROM THE RECENT LITERATURE 2005

10/12/05

Biphasic anaphylactic reactions

Summary
Background - Anaphylaxis (Ana) has been typically considered a very rapid onset reaction with the major manifestations within the first hour. However, it is now recognized that in some Ana reactions there is a biphasic pattern with recurrence of manifestations several hours later.

Findings - The literature dealing with biphasic Ana was reviewed by Lieberman of the Univ of Tennessee in Memphis. The percentage of Ana episodes with a biphasic pattern has varied considerably (1-20%) in different reports. There has been no clear consensus about the features in the initial Ana response that are predictive of a later biphasic response. However, features such as the severity of the initial response, including laryngeal edema and hypotension, have been postulated as risk factors for biphasic patterns.

Most of the late phases in reported biphasic Ana reactions are of mild-moderate severity but occasionally severe, even fatal reactions have been described. Some authors have described delayed or inadequate dosing of epinephrine for the primary response as a risk factor for biphasic Ana. It is unclear whether corticosteroids treatment for the primary Ana response will prevent or ameliorate the recurrent reaction.

Reference
Ann Allergy Asthma Immunol 2005;95:217-26

Editor's Comments
This discussion by a very experienced clinical investigator makes some important points. Because up to 20% of Ana reactions may have a biphasic pattern, he makes a valid recommendation that patients who manifest an acute Ana reaction should be observed for at least 8 hours, even if the patient appears to recover completely from the initial episode. This may be particularly important if the in initial manifestations of the Ana reaction were severe.

 

<-- BACK