Medical Minute: Anaphylaxis & Biphasic Reactions

Leave a comment

July 21, 2014 by dailybolusoflr

 By Amanda Crichlow, MD

36 yo F presents to the emergency department with abdominal pain, nausea/vomiting and pruritus and sensation of her throat closing after taking Bactrim. Vitals signs are normal. Patient receives IM epinephrine. 


How long should she be observed in ED?

What is the concern?

Biphasic reactions = return of anaphylactic or allergic symptoms sometimes more severe after symptom resolution

The 2nd National Institute of Allergy and Infectious Disease/Food Allergy and Anaphylaxis Network symposium convened in July 2005 and provided recommendations for the management of anaphylaxis:
A reasonable length of time to consider observing the post-anaphylactic patient is 4-6 hours in most patients.

Question of the day – do most patients need to be observed for 4-6 hours?


The study below attempts to answer that question:


Grunau BE, Li J, Yi TW, et al. Incidence of Clinically Important Biphasic Reactions in Emergency Department Patients With Allergic Reactions or Anaphylaxis. Ann Emerg Med. 2014;63:736-744.

Objective: 
To determine the incidence of CLINICALLY IMPORTANT biphasic reactions

Method:
Retrospective chart review
Location: 2 urban academic centers in Canada (1st was 70000 visits/year, 2nd was 25000 visits/year)

Identified charts with ED discharge diagnoses of “allergic reaction” from April 2007 – March 2012

Exclusion criteria:
1) age < 17
2) primary diagnosis of asthma with allergic reaction coded as a secondary diagnosis
3) patient left without being seen
4) patient had preexisting condition that was known to cause nonallergic angioedema

Patients divided into 2 groups:
1) anaphylaxis (based on strict definition) or 
2) allergic reaction (if criteria not met for anaphylaxis)

Definitions:
Anaphylaxis

Any of the following 3 numbered criteria must be satisfied:

1) Both of the following

a) skin or mucosal involvement

b) one of the following:
  1. respiratory compromise
  2. Systolic blood pressure < 90 mmHg or syncope


2) Two of the following after exposure to likely allergen
  1. Skin or mucosal involvement
  2. Respiratory compromise
  3. Systolic blood pressure < 90 mmHg or syncope
  4. Gastrointestinal symptoms


3) Systolic blood pressure < 90 mmHg after exposure to a known allergen

Allergic reaction

A clinical patient presentation in which criteria for anaphylaxis was not met however attending physician deemed etiology of signs and/or symptoms secondary to allergic process

Clinically important biphasic reaction
Recurrent or new signs or symptoms occurring after an initial allergy-related presentation without any obvious further exposure to an offending allergen

Primary outcome : proportion of patients who had a clinically important biphasic reaction within 7 days of the index ED visit

Follow-up: 7 day regional ED visit database review

Results
In 2819 patients, only 5 clinically important biphasic reactions in both the index ED visits and 7 day follow-up period (0.18%)


Conclusions
Clinically important biphasic reactions are rare
Routine prolonged observation of patients of patients with symptom resolution likely unnecessary
More important interventions: patient education and epi-pen prescription at discharge
References:

Sampson HA, Munoz-Furlong A, Campbell RL, et al. Second symposium on the definition and management of anaphylaxis: Summary report – Second National Institute of Allergy and Infectious Disease/Food Allergy and Anaphylaxis Network symposium. J Allergy Clin Immunol. 2006;117:391-397.

Grunau BE, Li J, Yi TW, et al. Incidence of Clinically Important Biphasic Reactions in Emergency Department Patients With Allergic Reactions or Anaphylaxis. Ann Emerg Med. 2014;63:736-744.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: