Microsoft word - high_altitude_health.docx

More often than not, attempts to predict performance at altitude are no better than guessing. However,over the age of 50, only very fit people who exercise regularly and have some experience with highaltitude should try to go to 15,000 feet. Narrowing of the arteries (atherosclerosis), which occurs ineveryone to varying degrees, further limits the delivery of oxygen to the brain and heart. This can lead toangina, congestive heart failure, altered mental function, or even heart attack or stroke.
What is Acute Mountain Sickness?
Acute mountain sickness (AMS) refers to a spectrum of medical problems that may occur on ascent to
altitude, ranging from mild symptoms to fatal illness. Mountain sickness may occur as low as 8,000 feet,
but most serious illness is seen above 12,000 feet. With increasing altitude, there is a progressive decrease
in barometric pressure and a corresponding decrease of oxygen in the air. This is the cause of AMS,
however, the exact process that triggers illness is not known. Nor is it known why some persons become
ill while others successfully acclimatize—a process of physiologic changes allowing the body to adapt to
less oxygen in the air. In travelers to altitude, some of these acclimatization changes occur in days, others
in weeks.
The incidence and severity of AMS depends not only on the altitude attained, but also on the rate ofascent. There is individual susceptibility, but no one is immune. Physical conditioning and prior successat altitude do not preclude illness. In fact, young, conditioned climbers have a higher incidence, probablybecause they push themselves harder. This does not imply that physical conditioning is unnecessary orundesirable. It means that even those in top physical condition must respect the limits on travel imposedby altitude.
Symptoms of AMS
Most people have experienced (but may not have recognized) mild symptoms of AMS, which include
headache, lack of energy and appetite, nausea, dizziness, weakness, and insomnia. The symptoms begin
4-12 hours after arrival at altitude and are usually transient, lasting one to two days. In some people,
symptoms progress to severe headache, irritability, nausea with vomiting, marked fatigue and shortness of
breath with exercise. These symptoms indicate the development of pulmonary or cerebral edema, the
most serious forms of AMS. No further ascent should be attempted with any of these serious symptoms,
and descent should be strongly considered.
Pulmonary edema can be described as water on the lung. It first appears as excessive shortness of breathon exertion compared to other members in a party, and then progresses to shortness of breath at rest witha dry cough and/or wheezing. The heart rate and respiratory rate are increased. Marked periodic breathing(an irregular breathing pattern with periods of shallow or no breaths) is present during sleep. The victimmay need to sit up due to severe shortness of breath when lying down. At this stage, oxygen is helpful anddescent is mandatory. Deterioration can occur rapidly, usually at night, with the onset of severerespiratory distress, gurgling breathing, a frothy cough, and wet crackling sounds in the lungs. Confusion,coma, and death can then occur within hours.
Cerebral edema indicates swelling of the brain. The principal symptom is progressive headache that isunrelieved by mild pain relievers. Other symptoms of moderate AMS, such as dizziness, vomiting, andirritability, are usually present. The best simple test for early cerebral edema is to check the person’scoordination by having him walk heel-to-toe (the drunk test). Presence of uncoordination, withprogressive headache and lethargy (drowsiness, decreased responsiveness) mandates immediate descent.
Victims with this severe form of AMS can deteriorate overnight to a state of confusion and deliriumfollowed by unconsciousness and death.
Treatment in the Field
First and foremost in the treatment of progressive AMS symptoms is evacuation to lower altitudes. Often
a descent of 2,000-3,000 feet is enough. If oxygen is available, it is helpful and should be given, but never
as a substitute for descent. Don’t wait for the helicopter that may come too late or never at all.
Mild to moderate AMS can be watched carefully at the same altitude for one day to see if there isimprovement. Lack of improvement in 12-24 hours or any signs of deterioration require immediatedescent. Aspirin is most useful for the headache of AMS. Stronger medication, such as codeine, should beused with caution and only when a knowledgeable person is monitoring the victim. Sleeping pills shouldnot be used for insomnia related to AMS; they depress breathing and may worsen symptoms.
Acetazolamide (Diamox) is the best medication to treat symptoms of mild to moderate AMS and to aidsleep, but should be used only with knowledge of its effects and the proper dosing regimen.
It is very important for partners, and friends to monitor each other. Sometimes serious AMS goes
unrecognized because the victim becomes unsociable and others assume that reclusive or bizarre behavior
is their usual personality. Other cases are incorrectly diagnosed as a “flu” or traveler’s infection. Anyone
who is doing poorly or feels ill at altitude should be assumed to have altitude illness!
Do not try to
conceal symptoms and tough it out by pushing higher. Please keep the group leader or guide informed of
any significant symptoms you, your partner or friend may have. Delay can result in deterioration from
someone who could have walked down with assistance to a litter patient who is extremely difficult to
carry down, or worse yet, to a corpse.
The best prevention of AMS is slow ascent. Symptoms are common when flying or driving to 9,000 feet
or above. While transportation to these altitudes is sometimes unavoidable given the time constraints, the
hiking itinerary is planned to minimize risk of altitude sickness. Acclimatization is a progressive process.
Successful acclimatization at one altitude results in only partial acclimatization to higher altitudes.
Overexertion disposes to AMS. Don’t push beyond your ability; MLP’s trek is designed to allow you togo at a comfortable individual pace. While physical conditioning does not prevent AMS, it makes anyhike or climb less exerting.
Dehydration increases the risk for AMS and worsens the symptoms. Initially, fluid is retained at altitude.
Women may note puffiness of fingers, ankles, and face. However, this does not mean that fluids shouldbe restricted. On the contrary, intake of copious liquids will often initiate a diuresis that resolves the fluidretention as well as the symptoms of AMS.
Substantial protection from the symptoms of AMS can be obtained from acetazolamide (Diamox), amedication that promotes increased respirations and acts as a mild water pill. It is begun 12 hours prior toascent and continued only 1-2 days after ascent. The dose is 125-250 mg in the morning and evening.
Some people require only 1dose taken at bedtime for 1-2 nights. There are side effects and potentialreactions to this medication, including a diuretic effect, tingling of the fingers and lips, and altered taste ofbeer and other carbonated beverages. Do not use Diamox if you are allergic to sulfa antibiotics, due tocross-reactions. Dexamethasone can also be used for prevention. Discuss these and other medications, aswell as issues of high altitude, with a doctor who is knowledgeable in travel and altitude medicine beforeleaving.


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