Episode 942: Acute Mountain Sickness and High Altitude Cerebral Edema

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 Donate: https://emergencymedicalminute.org/donate/