Written by Clay Smith
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Epinephrine is the key drug for anaphylaxis. Give it early in suspected cases. Antihistamines and glucocorticoids are permissible but not very helpful and certainly should not supersede epinephrine.
Why does this matter?
Anaphylaxis is dangerous and common, with lifetime prevalence of 1.6-5.1%. Thankfully, it is rarely fatal, 0.47-0.69 per million. Medication and stinging insects are the most common causes in adults; foods and stinging insects in children. This review answers some important questions regarding anaphylaxis.
Epi is the stuff
Here are the most important takeaways. The quality of evidence for most of these recommendations was low.
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Biphasic anaphylaxis is likely real but rare. Patients with severe anaphylaxis and those requiring more than one epinephrine dose are at higher risk of biphasic reaction and need longer observation.
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Epinephrine is the critical intervention for anaphylaxis.
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Recommended dose is 0.01 mg/kg of a 1:1000 [1 mg/mL] solution to a maximum of 0.5 mg in adults and 0.3 mg in children.
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It is often underutilized and should be the first-line treatment.
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Do not delay administration in suspected cases.
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Antihistamines and glucocorticoids are not helpful in preventing a biphasic reaction, but they have a role in pre-treatment prior to certain chemotherapy regimens and aeroallergen immunotherapies.
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Authors suggest against routine use of antihistamines and glucocorticoids in preventing radiocontrast medium anaphylaxis.
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Patients should be observed until symptoms are fully resolved. At discharge, they should receive, “education about anaphylaxis, risk of recurrence, trigger avoidance, self-injectable epinephrine, and thresholds for further care, and they should be referred to an allergist for follow-up evaluation.”
What’s new and important? First, a higher dose than 0.3mg is recommended in adults, max 0.5mg IM. The importance of early epinephrine is reemphasized. Risk of biphasic reaction is probably greater with more severe cases and those needing >1 dose of epinephrine. Use of antihistamines and steroids is deemphasized; notably, premedication prior to IV contrast is not recommended.
Source
Anaphylaxis-a 2020 Practice Parameter Update, Systematic Review, and Grading of Recommendations, Assessment, Development and Evaluation (GRADE) Analysis. J Allergy Clin Immunol. 2020 Apr;145(4):1082-1123. doi: 10.1016/j.jaci.2020.01.017. Epub 2020 Jan 28.
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