High-Altitude Illness

Also known as Acute mountain sickness · AMS · High-altitude cerebral edema · HACE · High-altitude pulmonary edema · HAPE · Acetazolamide

The high-altitude illness — the hypobaric hypoxia from the ascent. The spectrum: the AMS (the headache + the nausea / the fatigue / the dizziness), the HACE (the ataxia + the altered mental state — the brain oedema), the HAPE (the non-cardiogenic the pulmonary oedema). The DESCENT (the primary), the acetazolamide, the dexamethasone (the HACE), the nifedipine + the oxygen (the HAPE), the Gamow bag.

low47 referencesUpdated 2 Sept 202626 min readSource-verified · Sept 2026

Checked against its sources on 2 Sept 2026

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8 MCQs

The one-line answer

High-altitude illness is one injury — hypobaric hypoxia — wearing three faces and solved by one treatment — descent. The spectrum runs from AMS (headache plus at least one other symptom — nausea or vomiting, fatigue, dizziness; 2018 Lake Louise score at least 3, with sleep no longer a scored item), through HACE (ataxia with progressive alteration in mental status — regarded as the terminal, most severe form of AMS), to HAPE (non-cardiogenic pulmonary oedema after rapid ascent above 2500 m — exertional dyspnoea becoming dyspnoea at rest, cough, crackles, cyanosis). Descent is definitive: it is the single best treatment, and is mandatory, if at all possible, for the potentially fatal syndromes — with oxygen to maintain arterial saturation above 90%. The adjuncts match the syndrome: acetazolamide 125 mg every 12 hours for AMS prophylaxis (WMS 2019; 250 mg daily is the lowest dose in the 2012 Low meta-analysis), dexamethasone 8 mg once then 4 mg every 6 hours for HACE, and nifedipine extended-release 30 mg every 12 hours or 20 mg every 8 hours for HAPE.^[10]^[2]^[43]^[6]^[36]

Meet the patient

A 34-year-old fit trekker is in the lodge at 4500 m on day 3. He flew to 2800 m two days ago and climbed fast. Overnight he became breathless at rest and coughed up pink frothy sputum; his tent-mate, who complained only of a headache yesterday, now cannot walk a straight line to the latrine. One has HAPE, the other has HACE — and the answer for both is the same word: descend.^[1]^[3]

Hold that pairing: the breathless lungs and the stumbling brain are two faces of one process, and everything below unpacks why a single word — descent — decides who lives.^[3]

References47Show

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