Nepal Pheriche Medical Clinic 2001.11.27

Acute Mountain Sickness (AMS)

Since we're avid trekkers, we hear about, read about, and experience AMS. A web search gives AMS associated terminology and even a detailed chemical explanation of AMS. Still, basic practical knowledge that can save lives is generally missing from the bulk of available information.

We attended an AMS seminar in Pheriche (town on the Everest Base Camp trek) and learned some valuable information that every trekker should know before hiking up a mountain.

AMS = Acute Mountain Sickness. Symptoms are headache, nausea, shortness of breath, tiredness, and tingling in the extremities.
SMS = Severe Mountain Sickness. Symptoms are severe headache, vomiting, and disorientation in addition to AMS symptoms.
HAPE = High Altitude Pulmonary Edema. What happens: fluid buildup in the lungs. Symptoms are gurgling, blueness in the lips from lack of oxygen in the blood, and drowning in the body's own fluids. HAPE symptoms can take up to 4 days to develop.
HACE = High Altitude Cerebral Edema. What happens: the brain swells. Symptoms are severe headache, disorientation, loss of balance, and inability to walk forward heal-to-toe. HACE symptoms can take up to 24 hours to develop.


  1. Ascend slowly, gaining no more than 300~500 meters (1000~1650 feet) per day. Physically fit, inexperienced trekkers are most likely to run up a mountain quickly and get seriously sick.
  2. Sleep at a lower elevation than your highest hiking elevation for the day. Slower breathing at sleep magnifies the effects of elevation gain.
  3. Be physically fit and don't overexert yourself above elevations that your body is acclimatized to.
  4. Drink at least 3 liters of water per day. Drink even more if taking Diamox.
  5. Eat lots of garlic. Though not medically proven in the lab, garlic has a property that helps the body adjust to higher elevations. Garlic soup is available on treks throughout Nepal. Eat a garlic soup a day to keep mountain sickness at bay.

RULE 1: Never continue to ascend if altitude sickness symptoms develop.

RULE 2: The only cure for altitude sickness is descent. If symptoms worsen at a particular elevation, descend until symptoms clear.

RULE 3: Always ensure someone with altitude sickness is accompanied down. Many deaths occur when a sick unaccompanied individual becomes disoriented.

If symptoms are severe, seek immediate medical attention. Many mountain medical clinics are equipped with medication and a Gamow Bag, a pressurized rubber chamber that can simulate a lower atmosphere (up to 1400 meters / 4600 feet lower) to immediately alleviate some mountain sickness problems. Once stabilized, the patient is normally carried to lower elevation by helicopter. (In the Everest region, helicopter rescue costs US$3000 from Gokyo and US$2500 from Pheriche. Make sure your medical insurance covers these rescue costs before coming to the Himalaya for trekking. Record your medical insurance information with your embassy in Kathmandu before starting your trek). The time from developing severe mountain sickness symptoms like HAPE to death can be as little as a few hours if no action is taken.

It's critical to remember that HAPE symptoms can take up to 4 days to surface. If someone starts gurgling in the middle of the night, he/she may need to descend to the elevation he/she was at 3 to 4 days ago before the symptoms improve. This also explains why some people start drowning from HAPE even 1 or 2 days after beginning their descent from the summit.

In the case of HAPE, always seat the patient upright to drain some of the fluid from the lungs and allow the patient to breath somewhat. Lying the patient horizontally is a sure way to drown him/her more quickly.

If you see someone with AMS, ensure the person knows what AMS is and how to respond to it. Surprisingly, most trekkers at high altitude have never heard of mountain sickness and put themselves at extreme risk.

Diamox cannot be taken by anyone allergic to sulfonamides. For everyone else, Diamox helps the body acclimatize to higher elevation faster. One tablet is typically 250mg. The proper dose for AMS is 62.5~125mg per day (quarter to half tablet). Take a whole tablet for severe symptoms and immediately descend. Side effects are frequent urination (Diamox is a diuretic) and possible tingly fingers. The smaller the dose of Diamox, the less often your bladder will wake you up in the middle of the night. Since rest is important at high elevation, the fewer late night interruptions the better. Several doctors who have no trekking experience have published articles prescribing a dose of 500~1000mg of Diamox per day. This dosage is absolutely false and will ensure zero sleep.

Diamox can be started and stopped at any elevation and does not need to be taken continuously. The time from ingestion to improvement is about 30 minutes. The drug should not be relied on, but should be carried in case of emergency.

A natural alternative to drugs is garlic. A daily dose of garlic soup is delicious and helps the body to acclimatize to higher elevation faster.

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