Altitude illness: risk factors, prevention, presentation, and treatment.

Altitude illness affects 25 to 85 percent of travelers to high altitudes, depending on their rate of ascent, home altitude, individual susceptibility, and other risk factors. Acute mountain sickness is the most common presentation of altitude illness and typically causes headache and malaise within six to 12 hours of gaining altitude. It may progress to high-altitude cerebral edema in some persons. Onset is heralded by worsening symptoms of acute mountain sickness, progressing to ataxia and eventually to coma and death if not treated. High-altitude pulmonary edema is uncommon, but is the leading cause of altitude illness-related death. It may appear in otherwise healthy persons and may progress rapidly with cough, dyspnea, and frothy sputum. Slow ascent is the most important measure to prevent the onset of altitude illness. If this is not possible, or if symptoms occur despite slow ascent, acetazolamide or dexamethasone may be used for prophylaxis or treatment of acute mountain sickness. Descent is mandatory for all persons with high-altitude cerebral or pulmonary edema. Patients with stable coronary and pulmonary disease may travel to high altitudes but are at risk of exacerbation of these illnesses. Medical management is prudent in these patients.