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
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
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
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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