Mitchell Lester
Treatment of Anaphylaxis
The onset and progression of anaphylaxis is rapid. One retrospective study of anaphylactic deaths from medication, food, and venom found that nearly all patients had their first cardiac arrest within 20-45 minutes of exposure (with onset of symptoms even faster). Patients with the earliest onset of symptoms, parenteral exposure, delay in initiating treatment, concurrent ß-blocker use, and underlying cardiovascular or respiratory disease were at greatest risk of anaphylactic death.

Epinephrine is the treatment of choice for anaphylaxis because of its rapid onset of action (within seconds). Intramuscular epinephrine administration is preferred because higher and faster peak serum levels are achieved than after subcutaneous administration,

Many practitioners (and even emergency rooms) start treatment with other classes of medication. Independent of the route of administration (IM, IV, or PO), antihistamines’ onset of action is at least 20-30 minutes. Antihistamine administration should be delayed until after epinephrine. Corticosteroids have never been shown to decrease the incidence of biphasic or protracted anaphylaxis. Their onset of action is 4-6 hours after administration, also independent of route. While they probably don’t help, it is unlikely that a single short course of steroids will have any significant adverse effect. If the practitioner wishes to treat with steroids, it is not necessary that they be given quickly.

Depending on how severe the reaction is, basic life support measures might be required as recommended by the American Red Cross (“Circulation-Airway-Breathing”). In anaphylaxis, epinephrine should be administered as soon as it is available during basic CPR measures. In addition, when there is hypotension intravenous fluids should be given as soon as possible.

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