Acute mountain sickness AMS involves a complex of symptoms that occur most often in unacclimatized sea-level residents who ascend rapidly to high altitude. The clinical symptoms of AMS tablecan be very debilitating. They usually develop -after ascent, reach peak in intensity in – h, and resolve in – days as
Clicking sounds heard through a stethoscope placed on the chest; this is evidense of excess mucus in the lungs acclimatization takes place. A few individuals experience symptoms at elevations as low as, but AMS is more common over. Virtually everyone will experience some symptoms if they proceed over mft rapidly. Acclimatization at an intermediate altitude decreases the incidence of AMS, but even well-acclimatized persons usually develop a headache after reaching mft.
Although the basic cause of AMS is probably related to brain swelling subsequent to hypobaric hypoxia, the symptoms are not reversed by supplemental inhalation. In moderate to severe cases of AMS, fluid retention and redistribution lead to increased intracranial pressure and lung swelling, which impairs and CO exchange. One cause of this fluid retention is that renal handling of water switches from net loss or no change to a net gain of water. Concurrently, fluid is moved selectively into the intracellular space.
Severe AMS gives a climber a sense of overwhelming oppression in which trifling work is fatiguing. The common symptom of headache can progress to cruel intensity. Apathy may be interrupted by outbursts of irritability. Eventually, one can become completely ineffective.
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Treatment of AMS consists of descent, supplemental O, and the prescription drug acetazolamide Diamox. Descent should continue until symptoms improve. Often a descent as small as will be sufficient.
Physicians, experienced climbers, and physiologists recommend several techniques to prevent AMS. These include instructions regarding graded ascent, diet, exercise, and medication. Graded ascent refers to climbing in stages. Two to three nights should be spent at – – ft before going higher, and an extra night should be added for each additional – – ft attempted. Abrupt increases of more than in sleeping altitude should be avoided when at or higher. Acclimatization may be aided by taking day trips to higher altitude, if sleep is taken at a lower elevation. This advice is summarized by the widely used phrase, climb high, sleep low. A diet rich in carbohydrates of total calories has been shown to reduce AMS symptoms byand increase the level of arterial blood, in a group of soldiers taken quickly to mft. Overexertion is believed to contribute to the illness, perhaps by adding to the total stress on the body. Mild exercise, though, seems to aid acclimatization.
Acetazolamide also is effective as a preventive measure for AMS. This medication aids respiratory acclimatization, prevents periods of extreme hypoxia, and maintains higher blood levels during sleep when periodic breathing is a problem; see the section titled Sleep, pageImportantly, acetazolamide also counteracts fluid retention because it is a diuretic. Numerous studies indicate that acetazolamide is about effective in preventing AMS in visitors to altitudes of- ,-, ft. As a member of the sulfa drug family, acetazolamide carries precautions about hypersensitivity for individuals who are allergic to sulfa drugs. The drug dexamethasone offers alternative preventive properties, but it is less effective than acetazolamide and has several unwanted side effects. In combination, however, acetazolamide plus a low dose of dexamethasone appears to be more effective than acetazolamide alone to ameliorate the symptoms of AMS.