A STAMARIL Center
Rapid ascent (over 3,000 ft (or 1,000 meters) per day to elevations of 10,000 ft
(or 3,000 m) or greater may result in symptoms much like a hangover, pesky but
not terribly serious. This problem is called Acute Mountain Sickness (AMS).
Symptoms may include headache, nausea, fatigue and/or a vague general ill
feeling. Sometimes there is vomiting. Usually, a person may take acetaminophen
(Tylenol) for the headache, rest a little and will feel better. Sometimes
symptoms may recur. This problem does not demand descent. To prevent AMS, the
traveler is advised to maintain good hydration (drink enough to make at least 1
ounce of urine per hour), especially if trekking or exerting. Being physically
fit and having ascended to the same altitude before without a problem does not
guarantee that a traveler will be free of an altitude problem on subsequent
Symptoms may be partially or completely prevented by taking acetazolamide (Diamox). The usual tablet size is 250 mg. The usual dose for adults is 125 mg (½ of a 250 mg tablet) twice daily, close to every 12 hours. Dosing should start 24-48 hours before starting the major ascent, and when descent is begun from the highest elevation. This medicine may cause tingling in the fingers or around the lips. This is a sign that the medicine is working and does not mean that it should be stopped. While one is taking Diamox, carbonated beverages may taste unpleasant.
Especially for those who ascend to over 12,000 ft (but also in a very small number who ascend to the 8,000 to 12,000 range), there is a risk of two serious forms of altitude sickness, listed below. The higher the altitude, the greater the risk. Generally, those ascending above 14,000 ft are at higher risk and should be aware of and prepare for this possibility. Diamox can help prevent HACE, but probably not HAPE.these two more serious problems.
When traveling with an outfitter, you may expect them to tell the distinguish between the different kinds of altitude sickness and decide when descent is appropriate. Those trekking on their own at altitude need to understand more details about severe altitude sickness, and inform themselves beyond the scope of this handout.
High altitude pulmonary edema (HAPE) is a situation in which low inspired air oxygen concentration (found at altitude) causes low blood oxygen concentration, which in turn causes leakage of fluid into the lungs, causing more shortness of breath than one would expect. Severe HAPE is potentially fatal. Any possibility of any degree of this problem demands immediate descent.
High altitude cerebral edema (HACE) is a situation in which low inspired air oxygen concentration (found at altitude) causes low blood oxygen concentration, which in turn causes leakage of fluid into the brain, causing drowsiness, confusion, difficulty walking or coma. Severe HAPE is potentially fatal. Any possibility of any degree of this problem demands immediate descent.
HAPE and HACE may coexist and make each other worse.