- High-altitude illness often affects young and otherwise healthy individuals and there is a broad spectrum of disease. It progresses from the mildest form of acute mountain sickness (AMS) into the potentially life-threatening forms such as high-altitude pulmonary edema (HAPE) and high-altitude cerebral edema (HACE).
- A slow, graded ascent is the key to acclimatization. Acclimatization is generally defined as the body's physiologic adaptation to hypoxia at altitude. In the ideal setting, the first night's sleep occurs at <8000 ft, with the first day spent at rest.
- Pharmacologic agents may also be beneficial adjuncts to acclimatization. Acetazolamide (Diamox) has been shown to be very effective when staging is not possible or with individuals who are at an increased risk of high-altitude illness.
- Although normal acclimatization inhibits antidiuretic hormone (ADH) and aldosterone, resulting in a high-altitude–induced diuresis, the opposite is seen with AMS. Aldosterone, ADH, and renin–angiotensin increase, resulting in fluid retention and a leakage from the vascular space to the extravascular space.
- HACE is the most severe, life-threatening form of high-altitude illness. HACE is uncommon, affecting <1% to 2% of individuals who ascend without acclimatization.
- Definitive treatment of HACE is descent. High-flow oxygen is indicated as soon as symptoms are recognized and dexamethasone, at an initial dose of 1 to 2 mg/kg orally or intramuscularly, can produce dramatic improvement.
- HAPE is a life-threatening manifestation of high-altitude illness and represents a unique form of noncardiogenic pulmonary edema. It is estimated that HAPE affects 0.5% to 15% of those who ascend rapidly to high altitudes and is the leading cause of high-altitude death other than trauma.
Episodes of high-altitude illness have been documented for thousands of years, but these were relatively rare entities until the advent of modern travel. The increasing popularity of various recreational activities has led families and individuals to try to go higher (Fig. 141–1) and faster than ever before and on a more frequent basis. Hiking, mountain climbing, biking, skiing, hot air balloons, and gliders are among the various sports that can put individuals at risk of high-altitude illness. With modern modalities of travel, the incidence of high-altitude illness will continue to rise, putting more children and adults at risk (Fig. 141–2).
Climbing the Lhotse Face, Mt. Everest. Altitude 24,500 ft. (Photo courtesy of Gary Guller.)
Airlift of injured hikers off the Mt. Olympus trail, near Salt Lake City, Utah. Elevation, 8600 ft. (Photo courtesy of Intermountain Life Flight.)
High-altitude illness, resulting from an individual's altered responses to hypoxia and decrease in barometric pressure,1,2 often affects young and otherwise healthy individuals. There is a broad spectrum of disease, progressing from the mildest form of acute mountain sickness (AMS) to the potentially life-threatening forms of high-altitude pulmonary edema (HAPE) and high-altitude cerebral edema (HACE). Symptoms of high-altitude illness may develop within hours or days after ascent. In contrast, hypoxemia ...