Altitude Illness

High-altitude medicine, once the preoccupation of research pulmonologists and physicians practicing at high altitude or caring for climbers, has become essential for many primary care providers because of increasing numbers of recreational athletes engaging in skiing, hiking, trekking, and other high-altitude pursuits.

Acute mountain sickness (AMS) and its two most significant manifestations, high-altitude pulmonary edema and high-altitude cerebral edema, are complications of travel to higher altitude with insufficient acclimatization. Symptoms of AMS include headache, sleep difficulty, and gastrointestinal (GI) upset, including loss of appetite, nausea, and vomiting. Symptoms occur a few hours after rapid ascent in 25% of individuals at as low as 8500 feet (Harris et al., 1998), with a higher percentage being affected at higher altitudes. Individuals vary in their susceptibility to AMS, and a high level of physical fitness is not protective. Gradual ascent, allowing acclimatization, will prevent symptoms. If symptoms occur, delaying any further ascent with relative rest for 1 to 3 days usually results in improvement. More significant symptoms respond to decreasing altitude. Individuals with a history of AMS are likely to have it recur when they return to a higher altitude.

Planning time for acclimatization and avoiding excessive exercise when first arriving at a higher altitude are helpful. Nocturnal periodic breathing probably contributes to worsening hypoxia and subsequent AMS symptoms, so avoiding alcohol or other sedatives is also helpful. Acetazolamide, 125 to 250 mg twice daily, started the day of initial ascent and continuing for 48 hours, has been shown to decrease AMS symptoms and hasten acclimatization, possibly by decreasing nocturnal periodic breathing (Bartsch et al., 2004).

High-altitude cerebral edema (HACE) is defined as a progression of AMS symptoms to include ataxia, mental status changes, lassitude, and eventual coma. HACE is fatal if untreated. Treatment requires immediate descent. Hyper-baric treatment can be lifesaving if immediate descent is not possible; portable hyperbaric chambers are available for mountaineering expeditions. In addition to immediate descent, treatment includes oxygen at 2 to 4 L/min and dexa-methasone, 4 to 8 mg orally, followed by 4 mg every 6 hours.

High-altitude pulmonary edema (HAPE) is the development of pulmonary edema, dyspnea, and hypoxemia in the setting of AMS. Rapid descent to lower altitude is also the primary treatment. The administration of supplemental oxygen, 4 to 6 L/min, and nifedipine, 10 mg once, followed by 30 mg of sustained-release nifedipine every 12 to 24 hours, is helpful if immediate descent is not possible (Rodway et al., 2003).

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