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Acute cholecystitis — USMLE Step 3 MCQ

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HardSurgery (post-operative, follow-up)Acute cholecystitisUSMLE Step 3

A 42-kg adolescent develops hypotension, wheeze, and generalized urticaria immediately after vaccination. Epinephrine 1 mg/mL is available. Which initial order has the correct dose, route, and repeat interval?

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Correct answer: B — Give epinephrine 0.42 mg IM in the lateral thigh now; repeat in 5–15 minutes if needed

The best answer is “Give epinephrine 0.42 mg IM in the lateral thigh now; repeat in 5–15 minutes if needed”. Weight-based anaphylaxis treatment is 0.01 mg/kg of the 1 mg/mL formulation, producing 0.42 mg for this patient. The preferred route and site are intramuscular injection into the lateral thigh, and persistent symptoms permit another dose after 5–15 minutes. Anaphylaxis requires immediate IM epinephrine 1 mg/mL at 0.01 mg/kg, with repeat dosing every 5–15 minutes if needed. The alternatives use a different threshold, timing, population, or intervention and therefore do not match the clinical facts presented.

Reference: CDC: Management of Anaphylaxis: https://www.cdc.gov/vaccines/covid-19/clinical-considerations/managing-anaphylaxis.html