PREVENTION OF ALTITUDE-RELATED DISORDERS

Avoid direct or sudden ascent to a sleeping altitude above 9,020 ft (2,750 m). Acclimatization requires gradual exposure to altitude, with a rate of ascent not to exceed 1,500 ft (457 m) per day at altitudes above 8,000 ft (2,438 m). Rest days at a constant altitude are essential at heights above 10,000 ft (3,048 m). Acclimatization is achieved by adhering to a schedule of ascent:

In addition, the drug acetazolamide (Diamox) has proven to be useful in stimulating breathing, diminishing the sleep disorder associated with acute mountain sickness (AMS; see page 341), facilitating the body’s normal adjustment to high altitude, and thus improving nocturnal oxygenation. It is administered in a dose of 125 to 250 mg twice a day beginning 24 hours before ascent, and continued for a period of 2 days; within this period, the initial physiological acclimatization process should become operative. It may also be given as a 500 mg sustained-action capsule every 24 hours, with perhaps fewer side effects. Acetazolamide should be used if an ascent will be unavoidably rapid.

Children who have previously suffered from acute mountain sickness may benefit from acetazolamide, which should be administered in a dose of 5 mg/kg (2.2 lb) of body weight per day, in two divided doses, up to 125 mg per day. Diamox has a diuretic (increased urination) effect, so that it is extremely important to drink sufficient fluids to prevent dehydration. Fluid losses are generally greater at high altitude, so do not rely on thirst as a gauge of adequate fluid intake. Drink enough to keep the urine clear and light colored. Diamox is no substitute for proper acclimatization!

One study indicated that administration of inhaled salmeterol, a drug that affects transport of sodium and water in cells, may help decrease the risk of HAPE. The application of this finding to current recommendations for prevention and treatment is yet to be fully determined.

When you’re traveling at high altitudes, avoid the use of alcohol, stay warm, keep out of the wind, avoid exhaustion, and eat regularly to avoid weight loss. A diet relatively high in carbohydrates may be preferable to one high in fat and protein. Avoid the use of alcohol or any drugs for sleep during the first few days at altitude. Disturbed (poor quality, interrupted) sleep is common at high altitude. Acetazolamide, 125 mg by mouth at bedtime, diminishes the “periodic breathing” associated with sleep disturbance and therefore improves oxygenation, resulting in improved sleep quality. If insomnia is severe after the acclimatization process has occurred, zolpidem (Ambien) 5 to 10 mg, temazepam (Restoril) 10 to 15 mg, or zaleplon (Sonata) 5 to 10 mg by mouth may be used with caution under the guidance of personnel extremely experienced with high-altitude medical syndromes. A sleeping aid drug may be used in combination with acetazolamide.

It is not known if sleep apnea contributes to AMS or HAPE. However, a person with sleep apnea should be extremely cautious when traveling at high altitude. Findings suggestive of sleep apnea include the following: daytime—excessive sleepiness, feeling tired on awakening, fatigue, irritability, difficulty with simple tasks, and shortness of breath; nighttime—loud snoring, witnessed episodes of diminished or absent breathing, poor sleep, frequent awakening, frequent urination at night, and bedwetting.

Since oxygen is transported in red blood cells, it is advisable to avoid being anemic at high altitude. Iron-deficiency anemia is common in women, related to menstrual bleeding. If this is recognized, it should be corrected under the supervision of a physician with the administration of ferrous sulfate 300 mg per day; note that a side effect is constipation.

A pregnant woman who wishes to travel to high altitude should be certain that she has a normal pregnancy (e.g., normal blood pressure, no abnormal bleeding, placenta in proper position as determined by ultrasound if necessay). There is a possible increased risk for dangerous hypertension associated with pregnancy (preeclampsia) at high altitude. Proper acclimatization is essential. Try to keep the sleeping altitude no higher than 10,000 ft (3,048 m) and never above 12,000 ft (3,658 m).

In addition to the effects of less oxygen available at high altitude, mountaineers are subjected to other environmental hazards. Temperature decreases with altitude by an average of 11.7°F (6.5°C) per 3,280 ft (1,000 m). Ultraviolet light penetration increases approximately 4% to 6% per 984 ft (300 m) gain in altitude, which increases the risk for sunburn, skin cancer, and snowblindness. Sunlight reflecting off glaciers absent a cooling wind can transfer intense radiant heat. The dry air and rapid breathing predispose to dehydration.

Physical fitness, while desirable for mountaineering, does not protect against high-altitude illness. This cannot be overemphasized. It is, of course, good to be in excellent physical condition, but this does not substitute in any way for proper acclimatization.

In terms of preexisting conditions and the risk for high-altitude illness, here are some other general guidelines:

If a person suffers from any chronic condition, he should clear any travel of an extreme nature (high-altitude, cold, hot, exertion) with a physician and become educated on potential problems and solutions.