California Institute of Technology

Altitude Info and Links

Altitude Sickness links

    Altitude sickness is a broad term that includes Acute Mountain Sickness (AMS) as well as the more serious HAPE and HACE. Climbers have tried different drugs to combat altitude sickness, including acetazolamide (aka Diamox), dexamethasome (aka Decadron), Nifedipine, Sildenafil (aka Viagra) and ginkgo biloba extract. Before using these drugs, it is wise to learn more about them and I supply a few links below to get you started. I have personally only used over-the-counter ginko biloba; old studies suggested it alleviates altitude headaches, though I think new studies have shown that this is not for certain. It is cheap and safe, however, and readily available.

    In general, for climbing the Sierras, it is possible, though unlikely to develop more serious forms of Altitude Sickness. Because it is so unlikely, most parties will not have strong drugs like Acetazolamide or Decadron, and hence if a serious condition does develop, the only solution is quick descent to the valley.

  • Dr. J. Evans approached the club in fall 2006 and asked about volunteers for trying his new altitude supplement. Here are his papers that provide a nice summary (though not peer-reviewed) of the mechanisms involved in altitude sickness. You need the username and password to access the documents, per his request (email alpine).
  • LA Times article on using Viagra to prevent pulmonary edema
  • A nice "tutorial" on altitude sickness From the International Society for Mountain Medicine (ISMM).
  • High Altitude Medicine .com
  • A brief overview of AMS from drugs.com
  • Wikipedia entry on Diamox
  • Wikipedia entry on Decadron
  • Wikipedia entry on altitude sickness
  • The archives of the Wilderness and Environmental Journal Published by the Wildnerness Medical Society (wms.org). The current volume is for paid subscribers or members only, but the archives are public. Incidentally, the Caltech Library has a subscription, but the link doesn't seem to work. This is the first stop to go if you are looking for peer-reviewed articles.
  • Information from the Merck manual. Quite nice, and worth quoting part of it (boldface is mine):

      "Altitude sickness is best prevented by slow ascent, but the safe rate of ascent varies among individuals. Most can ascend to 5000 ft (1500 m) in 1 day without symptoms, but many are affected by ascending to 8000 ft (2500 m). Above this level, a rate of 1500 ft (460 m)/day is advisable. Climbers should learn how fast they can ascend without developing symptoms; a climbing party should be paced for its slowest member. Although physical fitness enables greater exertion with less O2 consumption, it does not protect against any form of altitude sickness. Strenuous effort should be avoided for 24 to 36 h after the ascent is completed, but bed rest is less beneficial than mild exercise.

      "Drinking much more water than usual is important, because overbreathing dry air at altitude greatly increases water loss, and dehydration with some degree of hypovolemia aggravates symptoms. Additional salt should be avoided. Alcohol seems to worsen AMS and diminishes nocturnal ventilation, thus accentuating sleep disturbance. Eating frequent small meals that are high in easily digested carbohydrates (eg. fruits, jams, starches) improves altitude tolerance and is recommended for the first few days.

      "Acetazolamide 125 mg at bedtime (for most persons) or 125 mg q 8 h is an effective prophylactic for AMS. Sustained-release capsules (500 mg once daily) are also available. Starting acetazolamide before the ascent has no advantage. Acetazolamide inhibits carbonic anhydrase, increasing ventilation and allowing better O2 transport with less alkalosis; it eliminates periodic breathing (almost universal during sleep at high altitude), thus preventing sharp falls in blood O2. Acetazolamide should not be given to patients allergic to sulfa drugs. Low-flow O2 during sleep has the same effect but is inconvenient. Analogs of acetazolamide offer no advantage. Antacids are useless for prevention. Dexamethasone, which minimizes symptoms of AMS, is not recommended for prevention.

      "Retinal hemorrhages require no treatment, generally resolving while the climber remains at high altitude.
      AMS seldom requires treatment other than fluids, analgesics, a light diet, mild activity, and (rarely) descent. Dexamethasone 4 mg po q 6 h is effective; acetazolamide 250 mg po q 6 h may alleviate symptoms.


  • The high-altitude brain, T.F. Hornbein, J. Exp. Biol. Sep. 2001 (18). This is the abstract from PubMed. Hornbein is also (or was) a noted climber. He and Willi Unsoeld were the first to climb the West Ridge of Everest in the 50s, and survived a high-altitude bivouac. Also, it turns out this issue of the Journal of Experimental Biology is devoted to hypoxia research. If you have access (eg. all Caltech users), you can view the issues's contents. Here is the full-text html form of Thomas Horbein's article.

    • Here are two articles about antioxidants; they may be more useful for their links
  • Oxidative Stress in Humans Training in a Cold, Moderate Altitude Environment, Schmidt et al, Wilderness and Environmental Medicine Vol. 13, no. 2 pp 94. Full text from WMS site or abstract via Pub Med" (with link to full text). About antioxidants (e.g. vitamins C and E, lipoic acid, ginko biloba) for longer term exposure to altitude. Basic conclusion: antioxidants only useful for people who have low antioxidant status (regardless of altitude).
  • Work at high altitude and oxidative stress: antioxidant nutrients, E.W. Askew, Toxicology Vol. 180, Issue 2, p. 107. Nov. 2002. Abstract via science direct, or if you have access (e.g. all JPL users, but not plain Caltech users), they have the full text. If you have a Caltech IP or know the alpine club password, you can access a full text pdf here.

Misc. supplement info

Caffeine
Antioxidants

    Extremely important for high altitude! Exercise and altitude both increase production of Reactive Oxygen Species. See Aug, 2006 New Scientist article about antioxidants in general. Despite the article listing evidence against supplements in the general population, they appear to be somewhat effective at high altitude for prevenging AMS symptoms. The New Scientist artile also gives a list of foods with high levels of antioxidants. In short, eat lots of pecans on your trips above 12,000'.


Cautions: Acetazolamide has unwanted side-effects, and most of the other strong altitude medicines have worse side-effects, so don't pop these pills on Mt. Whitney unless you absolutely need them. And of course, drugs may interact with each other. No website is a substitute for advice from your personal physician.