Prevention of Altitude Illness:
Current official pronouncements from the
Wilderness EMS Institute
, October 1996
Keith Conover, M.D., Medical Director
A web page on Accute Mountain Sickness? What the hey! I thought PATC was located on the East Coast of the U.S. Why a page on AMS?
Actually, AMS is of greater concern to Easterners, than Westerners who are used to dealing with this problem. AMS information is helpful to Eastern "Lowlanders" who make only occasional trips to the mountains of the West, or other high-altitude locals.
In the vast majority of cases, Easterners will not feel the affects of AMS until they pass elevations nearing 10,000 feet (though some start feeling the affects of altitude as low as 7,000 feet in elevation). The "early" symptoms are:
- Loss of appetite
- Shortness of breath
- Difficulty sleeping
As conditions worsen, symptoms can become more accute, leading to fluid in the lungs and brain, internal bleeding, and in the most severe cases, unconsiousness and potential death. Authorities on AMS recommend that you allow your body time to acclimate. One generally accepted rule of thumb is to ascend no more than 1,000 feet per day to allow your body to make the necessary physiological changes to adjust to a reduced oxygen level. Another option is to use specialized medication, which Dr. Conover discusses below.
Dr. Conover has assembled this information both to inform you of some medical options, and provide source material to allow your own Doctor to investigate further. The medications discussed by Dr. Conover are not commonly known to M.D.s on the East Coast of the U.S., but are more commonly used in areas of the U.S. where hikers and backpackers are known to "go to altitude". Dr. Conover hopes you and your doctor find the information helpful.
Andy - PATC Webmaster
Altitude illness is clearly related to the rate at which you ascend. Slower ascents, or ascents with planned rest stops, markedly decrease the incidence of altitude illness. Sometimes, high altitude climbers can descend each night, because sleeping altitude is so important in the development of altitude illness.
Acetazolamide (e.g., Diamox): Acetazolamide is effective both in preventing [2,3] and in treating altitude illness. Use the same dosage for either. The usual adult dose is 250 mg twice a day, either PO or IV. Some have suggested doses of just 125 mg twice or even once a day. Some have recommended giving the dose three times a day, but Dr. Hackett recommends using the same twice a day dose for both prevention and for treatment. To be most effective, start acetazolamide at least twenty-four hours before ascent. Acetazolamide is a sulfa drug, and those with a sulfa allergy must not take it. For such people, dexamethasone is a reasonable alternative for prevention. Acetazolamide works by increasing ventilation and increasing oxygenation, not just by masking symptoms.
Dexamethasone (e.g., Decadron): Dexamethasone works well for treating acute mountain sickness and HACE, but not HAPE.[5,6] Symptoms may return if the drug is withdrawn, so it is important to continue therapy if unable to descend. Some have recommended that it be used to help prevent AMS, and one study showed it worked better than acetazolamide. Another study, however, showed that lower than recommended doses may be ineffective for prevention. As with any potent steroid, dexamethasone may have significant side effects. At present, we recommend that you use dexamethasone to treat any patient with AMS, but for prevention only in those with a history of AMS, and only if allergic to sulfa (and thus allergic to acetazolamide).[9,10]
Nifedipine (e.g., Procardia, Adalat) will help prevent high altitude pulmonary edema in those who have had it before. However, nifedipine may have side effects including orthostatic hypotension (lightheadedness from low blood pressure on standing up). Therefore it is not suitable for routine prevention, except possibly for those with a prior history of high altitude pulmonary edema..
There is good evidence that high-carbohydrate meals improves exercise performance at altitude, and decreases the symptoms of AMS.[12,13] A diet high in carbohydrates was shown in one study to reduce the incidence of altitude illness by 30%.[14,15]
Since most people develop anorexia (decreased appetite) at altitude, sweet drinks make an ideal form of carbohydrate supplement.
Appropriate Exercise Levels
Some climbers report that heavy exercise makes one more likely to develop altitude illness, though no controlled studies are available.
High altitude climbers report that alcohol ingestion is well-known to increase the incidence of altitude illness.
Don't let anyone ascend with symptoms of altitude illness!
1. Evans W, Robinson SM, Horstman DH, Jackson RE, Weiskopf RB. Amelioration of the symptoms of acute mountain sickness by staging and acetazolamide. Aviat Space Environ Med 1976;47:512-6.
2. Forwand SA, Landowne M, Follansbee JM, Hansen JE. Effect of acetazolamide on acute mountain sickness. N Engl J Med 1975;279:839-45.
3. Larson EB, Roach RC, Schoene RB, Hornbein TF. Acute mountain sickeness and acetazolamide: Clinical efficacy and effect on ventilation. JAMA 1982;248(3):328-32.
4. Grissom C, Roach R, Sarnquist F, Hackett P. Acetazolamide in the treatment of acute mountain sickness: Clinical efficacy and effect on gas exchange. Ann Intern Med 1992;116(6):461-5.
5. Hackett PH, Roach RC, Wood RA, et al. Dexamethasone for prevention and treatment of acute mountain sickness. Aviat Space Environ Med 1988;59:950-4.
6. Montgomery AB, Luce JM, Michael P, Mills J. Effects of dexamethasone on the incidence of acute mountain sickness at two intermediate altitudes. JAMA 1989;261(5):734-6.
7. Zell SC, Goodman PH. Acetazolamide and dexamethasone in the prevention of acute mountain sickness. West J Med 1988;148:541-5.
8. Ellsworth AJ, Meyer EF, Larson ER. Acetazolamide or dexamethasone use versus placebo to prevent acute mountain sickness on Mount Rainier. West J Med 1991;154(3):289-93.
9. Levine BD, Yoshimura K, Kobayashi T, Fukushima M, Shibamoto T, Ueda G. Dexamethasone in the treatment of acute mountain sickness. N Eng J Med 1989;321(25):1707-13.
10. Rabold MB. Dexamethasone for prophylaxis and treatment of acute mountain sickness. J Wild Med 1992;3(1):54-60.
11. Bärtsch P, Maggiorini M, Ritter M, Noti C, Vock P, Oelz O. Prevention of high-altitude pulmonary edema by nifedipine. N Engl J Med 1991;325(18):1284-9.
12. Consolazio CF, Johnson HL, Krzywicki HJ. Body fluids, body composition, and metabolic aspects of high-altitude adaptation. Physiological adaptations: Deserts and mountains. Ed. Consolazio CF, Johnson HL, Krzywicki HJ. NY: Academic, 1972:227-41.
13. Askew EW. Nutrition and performance under adverse environmental conditions. Nutrition in exercise and sport. Ed. Hickson JF Wolinsky I. Boca Raton, FL: CRC Press, Inc., 1989:367-84.
14. Consolazio CF, Matoush LO, Johnson HL, Krzywicki HJ, Daws TA, Isaac GJ. Effects of high-carbohydrate diets on performance and clinical symptomatology after rapid ascent to high altitude. Federation Proceedings 1969;28:937-43.
15. Krzywicki HJ, Consolazio CF, Johnson HL, Nielsen WC Jr, Barnhart RA. Water metabolism in humans during acute high-altitude exposure (4,300 m). J Appl Physiol 1971;30(6):806-9.
16. Askew EW, Hoyt RW, Jones TE, Baker-Fulco CJ, Edwards JSA. Carbohydrate supplementation for work at high altitude: Liquid versus solid food supplements. Abstract. First World Congress on Wilderness Medicine, Whistler, BC, Canada. Point Reyes Station, CA: Wilderness Medical Society, 1991.
Keith Conover, M.D.