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Acute mesenteric ischemia — USMLE Step 3 MCQ

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

A healthy 74-kg traveler living at sea level must fly tomorrow to a sleeping altitude of 3,650 m and remain there for 3 days. Gradual ascent is impossible and there is no contraindication to medication. Which prophylactic regimen is preferred?

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Correct answer: E — Take acetazolamide 125 mg every 12 hours from today through the first 2 days at altitude

The best answer is “Take acetazolamide 125 mg every 12 hours from today through the first 2 days at altitude”. Abrupt ascent to this sleeping altitude places the traveler at high risk for acute mountain sickness. Acetazolamide accelerates ventilatory acclimatization and is preferred prophylaxis; the lower adult prophylactic dose begins before ascent, whereas treatment after symptoms or routine dexamethasone and nifedipine strategies answer different clinical situations. For an adult at meaningful acute-mountain-sickness risk, acetazolamide prophylaxis is 125 mg every 12 hours beginning the day before ascent and continuing for the first 2 days at altitude, and longer if ascent continues. The alternatives use a different threshold, timing, population, or intervention and therefore do not match the clinical facts presented.

Reference: CDC Yellow Book: High-Altitude Travel and Altitude Illness: https://www.cdc.gov/yellow-book/hcp/environmental-hazards-risks/high-altitude-travel-and-altitude-illness.html