Altitude illness — AMS/HACE/HAPE recognition, descent and drugs

(a) Diagnoses and shared intervention. The first patient has acute mountain sickness that has progressed to HACE: disturbed consciousness and ataxia after AMS. The companion has HAPE: dyspnoea with frothy sputum after ascent. Descent is mandatory for both cerebral and pulmonary oedema.^[7][8]

(b) Drugs and oxygen. HACE management emphasises descent and steroids; in a double-blind AMS trial at 4559 m, dexamethasone 8 mg initially followed by 4 mg every six hours reduced the AMS score; the authors concluded it may facilitate safe descent.^[8][9] HAPE requires immediate descent and/or adequate supplemental oxygen to maintain arterial saturation above 90 per cent. Nifedipine is an adjunct when descent and oxygen are not immediately available.^[10][11]

(c) Prevention. Slow ascent is the most important prevention; for susceptible people, average gain should not exceed 300 m/day above 2500 m.^[11] Acetazolamide 125 mg twice daily reduced AMS in a trekking trial, and 250 mg daily was the lowest effective dose in the meta-analysis. In small studies of HAPE-susceptible people, nifedipine, tadalafil and dexamethasone reduced HAPE.^{[7][5][6][4][12]}