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Acute Mountain Sickness (AMS) is a group of symptoms usually appearing together, with variations among individuals. It appears in people who have recently arrived at high altitudes or have just gained altitude, and may start anywhere from a few hours to a few days after ascending. High altitude is commonly defined as altitudes greater than 10,000 feet (3,000 meters).

Anyone trekking or climbing to, and in, high altitudes is at risk of developing AMS. Susceptibility varies from individuals and with the same person from time to time. Ascending quickly will increase its likelihood, and those who had it previously have a greater chance of getting it again. Physical conditioning has absolutely no influence on susceptibility. In fact, fit individuals tend to go faster and therefore may have a higher incidence. Overexertion and dehydration contribute to AMS and may be a predisposing factor. The key is to move at a slow, steady, comfortable pace, stay well hydrated and listen to your body.

The big concern here is dehydration, which can lead to rapid weakness and the inability. The following are the most common symptoms of AMS:

HEADACHE is by far the most common single symptom. It can vary from a minor nuisance to a severe throbbing. The severity of the headache is a good guide to its significance. A minor headache can be from a hard day of exertion, sun, cold or dehydration. This will usually disappear with some fluids and rest. The morning upon waking, is a good time to judge symptoms. A headache upon awakening is probably due to altitude and should be taken more seriously. This may be accompanied by nausea or even vomiting. A headache may be noticed on a descent from a pass or summit. This is a delayed altitude effect and probably due to the exertion on ascending. Aspirin can be taken to help relieve the pain. As with all AMS symptoms, timely descent is the best course of action if symptoms persist.

INSOMNIA is the inability to sleep. Altitude insomnia is characterized by difficulty falling asleep and frequent wakening during the course of the night. It is most noticeable during the first week of the trip due to the foreign sleeping accommodations, jet lag, time change and other factors. This usually improves during the second week. Insomnia becomes a problem when lack of sleep interferes with daytime functioning. All sleeping medications, barbiturates and opiates should be used with caution at high altitudes. Dalmane, a mild sleeping medication, can be useful. Diamox, a diuretic, helps with the body's acclimatization process and can also be useful. Check with your physician before acquiring and/or using such medication.

Rarely does a person with AMS have a good appetite at high altitude. The better the appetite at higher altitudes, the better a person is acclimatizing. Nausea is a problem, but will eventually pass as a person acclimatizes. Vomiting is a more serious problem. If not accompanied by other AMS symptoms, it is probably a 'stomach flu'. If it is in combination with diarrhea, fever or chills, it is usually dysentery, not acute mountain sickness. The big concern here is dehydration, which can lead to rapid weakness and the inability for that person to continue. Continue to drink fluids, rehydration powders are helpful, and descend to lower elevations. To control nausea and vomiting in AMS, Compazine or Phenergan suppositories can be taken.

The cold, dry air of the mountains can cause a deep, hacking cough on exertion. Hard candies, throat lozenges and proper hydration usually help relieve this problem. A frequent cough in association with severe breathlessness on exertion or mild breathlessness at rest (compared to companions) could be an indication of high altitude pulmonary edema. Proper diagnosis, medication and descent are the course of action in this case.

Irregular breathing is a common complaint above 10,000 feet (3,000 meters). It is the most noticeable at night, and characterized by four breaths or so, and then no breathing for as long as 10 or 15 seconds. This period of no breathing, apnea, will usually cause a person to waken in a panic. This symptom seems to be quite harmless and no cause for worry. It is caused by a change in the control of breathing within the brain. Diamox has been shown to improve this condition.

LASSITUDE is defined as weariness, indifference and/or fatigue. It differs from exhaustion which usually responds to 24 hours of rest. Lassitude progresses over 24 to 48 hours. A person may not get out of their tent for meals, talk with others or even refuse to drink sufficient fluids. This can lead to unconsciousness over the next 12 to 24 hours. It may occur without a headache, vomiting or shortness of breathe. The person will usually exhibit a loss of coordination. Immediate descent is required!

ATAXIA is a lack of coordination and balance that is very noticeable. Due to the lack of oxygen to the brain, this is a serious sign. Descent is necessary and oxygen if available. This condition can become serious 6 to 12 hours after it is diagnosed. Ataxia may also be seen in hypothermia. Rest and warmth are recommended after proper descent.