Altitude illness — AMS HACE HAPE and descent viva

Three syndromes. Headache and malaise within six to twelve hours of ascent is acute mountain sickness; insomnia alone is not specific and was removed from the 2018 Lake Louise score.^[9] Ataxia with altered consciousness suggests HACE. Dyspnoea with frothy sputum suggests HAPE.^[3][4]

Definitive treatment. Descent is mandatory for cerebral and pulmonary oedema. HACE treatment emphasises descent and steroids.^[4] HAPE needs immediate descent and/or adequate oxygen to maintain saturation above 90 per cent.^[3][5]

Drugs. In an AMS trial, dexamethasone 8 mg initially then 4 mg every six hours reduced the score; the authors concluded it may facilitate safe descent.^[7] Nifedipine is an adjunct for HAPE when descent and oxygen are unavailable.^[6][5]

Prophylaxis. Slow ascent is most important.^[3] Acetazolamide 125 mg twice daily reduced AMS.^[8] A meta-analysis found 250 mg daily was the lowest effective dose.^[10] For HAPE prophylaxis in susceptible people, nifedipine or tadalafil can be used for long sojourns and dexamethasone for a short stay of less than 5 days.^[11]