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High-Altitude Illness: Prediction, Prevention, Treatment
Getting Sick at High Altitude: Prevention & Treatment
Rapidly ascending above altitudes of 8,200 feet (2,500 meters) from lower elevations can result in illness ranging from mild nausea and headaches, to life-threatening edema of the lungs or brain. Truth is, there is little data to help physicians prevent or treat high-altitude illnesses, or to counsel patients with confidence as to their risk. A recent New England Journal of Medicine review by Peter Bärtsch and Erik Swenson summarizes what's known and what's not about illnesses resulting from high-altitude ascents.
High-Altitude Illness Pearls:
Being in great physical shape seems to provide no protection.
People who have had high-altitude illness before are at the highest risk.
The best prevention against all severe high altitude illness is to first acclimatize by spending a few days at 6,500 to 10,000 feet while taking day hikes from that altitude. Then, climb higher slowly: no more than 1,000-1,600 feet (300-500 meters) daily after passing 10,000 feet (3,000 m).
The single best treatment for all forms of high-altitude sickness: get down off the mountain.
Taking aspirin (320 mg) or ibuprofen (600 mg) a few times a day starting a few hours before ascent can prevent headache and acute mountain sickness.
Acetazolamide (Diamox, 125 mg) taken twice daily starting 1 day prior to ascent can prevent or reduce acute mountain sickness and high-altitude cerebral edema; 250 mg three times a day is recommended for higher-risk patients, and/or higher altitudes and faster climbs. Diamox's side effects (nausea, fatigue, others) can mimic mountain sickness.
Dexamethasone (4 mg 2-3 times a day) started before ascent can also prevent high-altitude pulmonary edema, as well as cerebral edema and mountain sickness. However, its potential side effect profile (high blood sugar, mood / thought disturbances) are worse than acetazolamide's.
There are three main high altitude illnesses: acute mountain sickness, the most common, which usually precedes more severe forms of high-altitude illness, including high-altitude pulmonary edema and high-altitude cerebral edema.
Acute Mountain Sickness
Usually precedes more severe forms of high altitude illness.
Symptoms: Almost always headache, with or without nausea, ill-feeling, loss of appetite, and/or sleep disturbance.
Onset: Rapid, within 6-12 hours of reaching >8,200 feet.
Incidence/Severity: Mild at lower altitudes, but common and often debilitating at higher altitudes (>15,000 feet).
Treatment for mild AMS: NSAIDs like ibuprofen, water, rest.
Treatment for severe mountain sickness: descent, supplemental oxygen, dexamethasone. If available, a manually pressurized hyperbaric "body bag" may help.
High-Altitude Pulmonary Edema
Onset: >2 days after ascending to >8,200 feet.
Symptoms: Fatigue, breathlessness, dry cough, progressing to frothy pink sputum and turning blue.
Incidence: Related to the height and rate of ascent; occurs in 1 of 7 people climbing to 18,000 feet in 2 days, but only 1 in 50 who take 7 days, and 1 in 500 who climb to only 14,000 feet in 4 days.
Treatment: Descent immediately + supplemental oxygen + nifedipine or phosphodiesterase-5 inhibitors (sildenafil, tadalafil, vardenafil, et al). Don't give diuretics; they won't help.
High-Altitude Cerebral Edema
Symptoms: Loss of balance, unsteady gait (truncal ataxia), headache unresponsive to OTC pain relievers, which can then rapidly progress to unconsciousness and death by brainstem herniation.
Onset/Incidence: occurs in ~1 out of 100 to 200 people >2 days after ascending past 13,100 - 16000 feet.
Treatment: Descent immediately + dexamethasone.
What's the chance you or your patient will get high-altitude illness on a mountain trip? It's virtually impossible to predict accurately, but remember that in unacclimatized people, risk of high-altitude illness generally begins at 2,500 m (8,200 feet) and goes up with total elevation (particularly over 5,000 m) and the rate of ascent. As you're planning your next ski vacation or considering a summit, here are a few numbers to consider:
Mount Everest (Nepal): 8,848 meters (29,029 feet)
Mount McKinley (Denali / Alaska): 6,194 meters (20,320 feet)
Mount Kilimanjaro (Tanzania): 5,892 meters (19,340 feet)
Breckenridge Mountain (Colorado): 3,962 meters (13,000 feet)
Most other Colorado mountains: About 12,000 feet
Taos, NM Ski Resort: 12,481 feet
Park City Mountain, Utah: About 10,000 feet
Peter Bärtsch and Erik Swenson. Acute High-Altitude Illnesses. NEJM 2013; 368:2294-2302. Luks AM et al. Wilderness Medical Society consensus guidelines for the prevention and treatment of acute altitude illness. Wilderness Environ Med. 2010 Dec;21(4):386.