Influence of Fluid Intake on Acute Mountain Sickness

Acute mountain sickness (AMS) is a problem seen at high altitude (usually considered to be above 3000 meters), characterized by a constellation of symptoms that include headache, nausea, dizziness, diminished or no appetite, weakness, fatigue, inability to keep up physically, and difficult sleeping. It ruins many adventures, including ski trips and treks at moderate altitudes, so avoidance is at least as important as treatment.

In the most recent issue of the journal Wilderness and Environmental Medicine, Dr. Maria Nerin and her colleagues report upon a study of a group of mountaineers, in which they documented an association between decreased fluid intake (dehydration) and a higher incidence of AMS. Although their study did not demonstrate statistical significance, it was in support of previous observations in which a similar relationship between dehydration and AMS has been noted.

There are many reasons why persons who ascend to high altitude become dehydrated. They drink less because they have diminished thirst and appetite. Water may be difficult to obtain in a mountainous region, particularly if ice must be melted. It may be a nuisance to carry the extra weight of sufficient water to not only avoid dehydration, but stay extremely well hydrated. Water losses may be greater due to rapid breathing in a cold, dry climate, and increased energy expenditure may consume water during the metabolism of fat, protein, and carbohydrates. Diarrheal illness may contribute to water loss.

One measure of fluid balance is urine output. The mountaineers who were more prone to AMS showed reduced urine output, which indicates that insufficient water was consumed or that water ingested was utilized to a greater degree.

The logical conclusion is that hydration at high altitude must be adequate to prevent or diminish the occurrence and severity of AMS, and perhaps other high altitude disorders that might be influenced by dehydration. The standard rule to drink enough to pee often and pee clear continues to be good advice.

Tags: high altitude, fluid, acute mountain sickness, AMS, health, wilderness medicine, outdoor medicine, healthline

photo by Terry Johnson

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