Altitude Sickness, often known as Acute Mountain Sickness (AMS), is a particularly important medical consideration while trekking in Nepal. Altitude Sickness means the effect of altitude on those who ascend too rapidly to elevations above 3,000 meters. Anyone may be effected by AMS reguardless of strength or physical fitness. There is two types of Altitude Sickness, high altitude pulmonary edema (HAPE) or high altitude cerebral edema (HACE)
1.High-Altitude Cerebral Edema
When AMS becomes life-threatening, it is called high-altitude cerebral edema (HACE). HACE symptoms include vomiting, lethargy, confusion, drowsiness, loss of coordination and coma. The condition can become fatal after a few hours or a few days. Because the hallmark of HACE is the impairment of cognitive ability, a person with HACE may be too impaired to realize what is wrong with him and to properly evaluate his situation. According to Altitude.org, anyone behaving in an irrational or bizarre way should be suspected of suffering from HACE. The site recommends having the person walk toe-to-heel in a straight line; if he fails the test you can presume he has HACE. To treat the condition, descend immediately.
2.High-Altitude Pulmonary Edema
AMS and HACE are the products of an oxygen-starved body. A different sort of high-altitude sickness is high-altitude pulmonary edema, or HAPE. This illness is the result of low air pressure causing a fluid build-up in the lungs. The condition can be fatal within just a few hours. HAPE is easily confused with AMS or HACE and it is possible for a person to suffer from HAPE and ACE/HACE at the same time. HAPE symptoms include lethargy, shortness of breath while resting or fast, shallow breathing, gurgling breaths, cough with a pink, frothy sputum, tightness or congestion of the chest, drowsiness and blue or gray lips and/or fingernails. Like HACE, HAPE is treated with immediate descent to lower altitude. If necessary, HAPE-sufferers can be placed in a Gamow bag, in which air pressure can be adjusted.
The initial symptoms of AMS are as following:
Loss of appetite
Dizziness, light heaviness, confusion, disorientation, drunken gait
Weakness, fatigue, lassitude, heavy legs
Slight swelling of hands and face
Breathlessness and breathing irregularity
Reduced urine output
These symptoms are to be taken very seriously. In case of appearance of any of the above symptoms any further ascent should be reconsidered. More serious problems can occur which can even cause death sometimes within a few hours. The main cure for the Altitude Sickness is to descend to a lower elevations immediately. Acclimatization by ascending to no more than 300 to 500 meters per day above 3,000 meters and the proper amount of rest are the best methods for prevention of AMS.
Literature and pamphlet published by Himalayan Rescue Association (see Rescue Service below) consists of detailed information on AMS. The Central Immigration Office and all trekking agencies in Kathmandu distribute this pamphlet free of cost. Since these documents also give information on the list of suggested medical supplies for trekkers, it is a compulsory item for every trekkers' medical kit.
Prevention of Acute Mountain Sickness.
If possible, don't fly or drive to high altitude. Start below 3,000 metres (10,000 feet) and walk up.
If you do fly or drive, do not overexert yourself or move higher for the first 24 hours.
If you go above 3,000 metres (10,000 feet), only increase your altitude by 300 metres (1,000 feet) per day, and for every 900 metres (3,000 feet) of elevation gained, take a rest day to acclimatise.
Climb high and sleep low! You can climb more than 300 metres (1,000 feet) in a day as long as you come back down and sleep at a lower altitude.
If you begin to show symptoms of moderate altitude sickness, don't go higher until symptoms decrease.
If symptoms increase, go down, down, down!
Keep in mind that different people will acclimatise at different rates. Make sure everyone in your party is properly acclimatised before going any higher.
Stay properly hydrated. Acclimatisation is often accompanied by fluid loss, so you need to drink lots of fluids to remain properly hydrated (at least four to six litres per day). Urine output should be copious and clear to pale yellow.
Take it easy and don't overexert yourself when you first get up to altitude. But, light activity during the day is better than sleeping because respiration decreases during sleep, exacerbating the symptoms.
Avoid tobacco, alcohol and other depressant drugs including, barbiturates, tranquillisers, sleeping pills and opiates such as dihydrocodeine. These further decrease the respiratory drive during sleep resulting in a worsening of symptoms.
Eat a high calorie diet while at altitude.
Medications used to treat high altitude illness include:
Aspirin or acetaminophen for headache
Diuretics, such as Lasix
Oxygen: especially during sleep
The early use of acetazolamide can help prevent mountain sickness. Taking this medicine a day or two before, and for the first 2-3 days at altitude will prevent high altitude illness in most people. Oxygen promptly relieves headache, dizziness, and most other symptom.