EM · Environmental emergencies
Altitude illness
Also known as Acute mountain sickness · High altitude cerebral oedema · High altitude pulmonary oedema · AMS HACE HAPE
Altitude illness after ascent above 2500 m: AMS (headache plus nausea/vomiting, fatigue/lassitude or dizziness; Lake Louise 2018 dropped sleep), HACE (ataxia or altered consciousness) and HAPE (dyspnoea at rest, non-cardiogenic oedema). Descent is definitive; oxygen aiming SpO2 above 90%; dexamethasone 8 mg then 4 mg every 6 hours for HACE; nifedipine ER 30 mg every 12 hours or 20 mg ER every 8 hours as a HAPE adjunct; acetazolamide 125 mg every 12 hours for AMS prophylaxis. ACEM-primary.
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8 MCQs with explanations
Target exams
Red flags
Meet the patient
A 45-year-old trekker two days into the Everest base-camp route arrives at the 5000 m alpine clinic with a bifrontal headache and nausea since dawn. By midday she is drowsy, disoriented, and cannot walk heel-to-toe without falling to the right. Her oxygen saturation is 78 percent on room air. Her companions want to push on to base camp before the weather closes in.[1]
The two questions that decide her next hour are the two that decide every altitude case: is her brain swelling? (the tandem gait answers in ten seconds) and can she descend now? (descent is the only cure). Hold those two and the whole topic slots into place.[1]
You have read the opening of this topic. The complete unit — every section and its primary-source references — is part of the Emergency Medicine fellowship atlas.
References14Show ledgerHide ledger
- [1]Luks AM, Beidleman BA, Freer L, et al. Wilderness Medical Society Clinical Practice Guidelines for the Prevention, Diagnosis, and Treatment of Acute Altitude Illness: 2024 Update Wilderness Environ Med, 2024.PMID 37833187
- [2]Hackett PH, Roach RC. High-altitude illness N Engl J Med, 2001.PMID 11450659
- [3]Imray C, Booth A, Wright A, et al. Acute altitude illnesses BMJ, 2011.PMID 21844157
- [4]Roach RC, Hackett PH, Oelz O, et al. The 2018 Lake Louise Acute Mountain Sickness Score High Alt Med Biol, 2018.PMID 29583031
- [5]Ferrazzini G, Maggiorini M, Kriemler S, et al. Successful treatment of acute mountain sickness with dexamethasone Br Med J (Clin Res Ed), 1987.PMID 3109663
- [6]Basnyat B, Gertsch JH, Johnson EW, et al. Efficacy of low-dose acetazolamide (125 mg BID) for the prophylaxis of acute mountain sickness: a prospective, double-blind, randomized, placebo-controlled trial High Alt Med Biol, 2003.PMID 12713711
- [7]Bärtsch P, Maggiorini M, Ritter M, et al. Prevention of high-altitude pulmonary edema by nifedipine N Engl J Med, 1991.PMID 1922223
- [8]Maggiorini M, Brunner-La Rocca HP, Peth S, et al. Both tadalafil and dexamethasone may reduce the incidence of high-altitude pulmonary edema: a randomized trial Ann Intern Med, 2006.PMID 17015867
- [9]Maggiorini M. Prevention and treatment of high-altitude pulmonary edema Prog Cardiovasc Dis, 2010.PMID 20417343
- [10]Richalet JP, Gratadour P, Robach P, et al. Sildenafil inhibits altitude-induced hypoxemia and pulmonary hypertension Am J Respir Crit Care Med, 2005.PMID 15516532
- [11]Honigman B, Theis MK, Koziol-McLain J, et al. Acute mountain sickness in a general tourist population at moderate altitudes. Ann Intern Med, 1993.PMID 8452324
- [12]Hackett PH, Rennie D, Levine HD. The incidence, importance, and prophylaxis of acute mountain sickness. Lancet, 1976.PMID 62991
- [13]Low EV, Avery AJ, Gupta V, Schedlbauer A, Grocott MP. Identifying the lowest effective dose of acetazolamide for the prophylaxis of acute mountain sickness: systematic review and meta-analysis. BMJ, 2012.PMID 23081689
- [14]Stream JO, Grissom CK. Update on high-altitude pulmonary edema: pathogenesis, prevention, and treatment. Wilderness Environ Med, 2008.PMID 19099331