Written by Aaron Lacy
In pre-hospital management of anaphylaxis, co-treatment with both epinephrine and antihistamines may reduce the risk of uncontrolled reactions, while use of prehospital corticosteroids may increase rates of admission.
Why does this matter?
Anaphylaxis is a true emergency, and failure to quickly recognize and appropriately treat can lead to rapid decompensation and death. Evidence and current guidelines strongly support the role of epinephrine as first-line treatment; however, the role of antihistamines and corticosteroids as adjunctive treatment is not as clear.
0.3mg Epinephrine IM! But now what…
Over 6 years, 3,498 patients in the Cross-Canada Anaphylaxis Registry (C-CARE) were recruited prospectively and retrospectively to assess the effect of prehospital epinephrine use compared with antihistamines and corticosteroids on anaphylaxis. 31% of these patients received epinephrine, 46% received antihistamines, and 2% received corticosteroids. When adjusted for asthma, sex, age, and most importantly severity, prehospital treatment with corticosteroids was associated with admission to the hospital (OR 2.84, 95% CI 1.55-6.97). Pre-hospital treatment with epinephrine and antihistamines decreased the likelihood of multiple epinephrine doses (OR 0.58, CI 0.41-0.82). It is important to note that this was prehospital administration of antihistamines and corticosteroids, and no conclusions about the administration of these meds in the ED can be made. This begs the question of what the prehospital algorithm for anaphylaxis should entail. Antihistamines have a relatively low side effect profile and have an onset of action within 1 hour. Long-term side effects of steroids are well documented but not as well in the short term, although there may be increased risk for fractures, VTE, and sepsis. It calls into question the utility of corticosteroids and raises the possibility of potential harm, at least when given prehospital. I likely will continue to give steroids as part of my anaphylaxis treatment in the ED. However, this study shows that the focus in the prehospital arena (and the ED as well) should be early epinephrine. It also seems to indicate that antihistamines are a helpful adjunct.
Evaluation of Prehospital Management in a Canadian Emergency Department Anaphylaxis Cohort. J Allergy Clin Immunol Pract. 2019 Sep – Oct;7(7):2232-2238.e3. doi: 10.1016/j.jaip.2019.04.018. Epub 2019 Apr 26.
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Reviewed by Clay Smith