EBM: Anaphylaxis

Definitions

Anaphylaxis is defined when one of the following criteria are met: 

  1. Involvement of the skin/mucosal tissue, or both PLUS at least one of the following:

    1. Respiratory compromise

    2. Reduced BP or associated symptoms of end-organ dysfunction

  2. TWO OR MORE of the following after exposure to a LIKELY allergen:

    1. Involvement of the skin mucosal tissue

    2. Respiratory compromise

    3. Reduced BP or associated symptoms

    4. Persistent gastrointestinal symptoms

  3. Reduced BP after exposure to a KNOWN allergen for that patient1

 

Treatment

The first line treatment for anaphylaxis is epinephrine. This should be drawn up and given while the patient’s ABC’s are being assessed. Since anaphylaxis can progress to cardiac arrest as quickly as 5 minutes [2], early epinephrine administration is crucial to prevent disease progression. Gabrielli et al demonstrated that prehospital epinephrine use may even decrease the likelihood of requiring multiple doses [3]. Dosing is 0.3-0.5mg (0.01 mg/kg pediatrics) of 1/1000 concentration epinephrine and can be re-dosed every 5 minutes. The preferred route is intramuscular. IM injections have been shown to be superior to subcutaneous injections [4], and this concentration of epinephrine should never be given through the IV. Once a second dose is required, it is reasonable to start an epinephrine drip for continued symptoms and titrate until hypotension is improved.

Adjuncts to treating anaphylaxis include antihistamines, steroids, and bronchodilators [5]. H1 and H2 blockers such as diphenhydramine (25-50 mg IV) and famotidine (20 mg IV) used together for symptom control are preferable to H1 blockers alone [6]. Steroids either orally (prednisone 1 mg/kg) or IV (methylprednisolone 1-2 mg/kg) are given to reduce biphasic reactions, though this is only theoretical [7]. Bronchodilators such as albuterol help symptom control secondary to bronchospasm for patients with concurrent asthma, but have no effect on upper airway edema. Glucagon can also be considered for patients who are on beta blockers.

Disposition

Patient disposition is dependent on severity of symptoms and epinephrine doses. For those who only required a single dose of epinephrine, discharge home after several hours of monitoring in the emergency department without recurrence of symptoms is reasonable. Consider admission of extended monitoring for patients needing multiple doses of epinephrine or severe presenting symptoms. All patients will need a prescription for an epipen and instructions on its use at discharge. 

POST BY: DR. DENIZ EREN (R3)

FACULTY REVIEW BY: DR. RILEY GROSSO

References

  1. Sampson HA, Muñoz-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(2):391-397. doi:10.1016/j.jaci.2005.12.1303

  2. Pumphrey. Lessons for management of anaphylaxis from a study of fatal reactions: Lessons for management of anaphylaxis. Clin Exp Allergy. 2000;30(8):1144-1150. doi:10.1046/j.1365-2222.2000.00864.x

  3. Gabrielli S, Clarke A, Morris J, et al. Evaluation of Prehospital Management in a Canadian Emergency Department Anaphylaxis Cohort. J Allergy Clin Immunol Pract. 2019;7(7):2232-2238.e3. doi:10.1016/j.jaip.2019.04.018

  4. Simons FER, Gu X, Simons KJ. Epinephrine absorption in adults: Intramuscular versus subcutaneous injection. J Allergy Clin Immunol. 2001;108(5):871-873. doi:10.1067/mai.2001.119409

  5. Li X, Ma Q, Yin J, et al. A Clinical Practice Guideline for the Emergency Management of Anaphylaxis (2020). Front Pharmacol. 2022;13:845689. doi:10.3389/fphar.2022.845689

  6. Sheikh A, ten Broek VM, Brown SG, Simons FER. H1-antihistamines for the treatment of anaphylaxis with and without shock. Cochrane Emergency and Critical Care Group, ed. Cochrane Database Syst Rev. Published online January 24, 2007. doi:10.1002/14651858.CD006160.pub2

  7. Alqurashi W, Ellis AK. Do Corticosteroids Prevent Biphasic Anaphylaxis? J Allergy Clin Immunol Pract. 2017;5(5):1194-1205. doi:10.1016/j.jaip.2017.05.022

EBMLauren McCafferty