Episode 942: Acute Mountain Sickness and High Altitude Cerebral Edema

Emergency Medical Minute

Contributor: Jorge Chalit-Hernandez, OMS3

Educational Pearls:

• Acute mountain sickness (AMS) is the term given to what is otherwise colloquially known as altitude sickness

• High altitude cerebral edema (HACE) is a severe form of AMS marked by encephalopathic changes

• Symptoms begin at elevations as low as 6500 feet above sea level for people who ascend rapidly

• May develop more severe symptoms at higher altitudes

• The pathophysiology involves cerebral vasodilation

• Occurs in everyone ascending to high altitudes but is more pronounces in those that develop symptoms

• The reduced partial pressure of oxygen induces hypoxic vasodilation in the brain, which results in edema and, ultimately, HACE in some patients

• Symptomatic presentation

• Headache, nausea, and sleeping difficulties occur within 2-24 hours of arrival at altitude

• HACE may occur between 12-72 hours after AMS and presents with ataxia, confusion, irritability, and ultimately results in coma if left untreated

• Clinical presentation may be mistaken for simple exhaustion, so clinicians should maintain a high index of suspicion

• Notably, if symptoms occur more than 2 days after arrival at altitude, clinicians should seek an alternative diagnosis but maintain AMS/HACE on the differential

• Treatment and management

• AMS

• Adjunctive oxygen and descent to lower altitude

• Acetazolamide is used as a preventive measure but is not helpful in acute treatment

• +/- dexamethasone

• HACE

• Patients with HACE should receive dexamethasone to help reduce cerebral edema

• Immediate descent to a lower altitude

References

1. Burtscher M, Wille M, Menz V, Faulhaber M, Gatterer H. Symptom progression in acute mountain sickness during a 12-hour exposure to normobaric hypoxia equivalent to 4500 m. High Alt Med Biol. 2014;15(4):446-451. doi:10.1089/ham.2014.1039

2. Levine BD, Yoshimura K, Kobayashi T, Fukushima M, Shibamoto T, Ueda G. Dexamethasone in the treatment of acute mountain sickness. N Engl J Med. 1989;321(25):1707-1713. doi:10.1056/NEJM198912213212504

3. 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;35(1_suppl):2S-19S. doi:10.1016/j.wem.2023.05.013

Summarized & Edited by Jorge Chalit, OMS3

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