AMS Precaution

About High Altitude Illness

What is Acute Mountain Sickness (AMS) And How to Avoid It
The high altitude and people's reaction to it is one of the difficulties to travel to Tibet. But it is not so serious as you imagined if you know it and get prepared for it.

What is High Altitude?

• High Altitude: 1500 - 3500 m (5000 - 11500 ft)

• Very High Altitude: 3500 - 5500 m (11500 - 18000 ft)

• Extreme Altitude: above 5500 m

When acclimatization lags significantly behind ascent, various symptoms occur. Acute Mountain Sickness (AMS) represents the body's intolerance of the hypoxic (low oxygen) environment at one's current elevation

What kinds of physiologic reactions will occur?

• Hyperventilation (breathing fast)

• Shortness of breath during exertion

• Increased urination

• Changed breathing pattern at night

• Awakening frequently at night

• Weird dreams

The altitudes of different places in Tibet
 

Tips to avoid AMS

• Do exercises to keep you fit before coming to Tibet.

• Avoid catching a cold.

• Make sure you have a good sleep the night before you flying to Lhasa.

• You'd better not to take any activities for the first day in Tibet.

• After getting off your airplane in the airport, walk slowly, take some deep breath. Do not do anything severely.

• Ascend to higher altitude gradually. DO NOT ASCEND ANY HIGHER if you feel bad.

• Prepare some AMS pills according to your doctor's suggestion.

Recognize AMS

In the context of a recent ascent, a headache, with any one or more of the following symptoms above 2500 meters (8000 feet) qualifies you for the diagnosis of AMS:

• Loss of appetite, nausea, or vomiting

• Fatigue or weakness

• Dizziness or light-headedness

• Difficulty sleeping

• Confusion

• Staggering gait

It is remarkable how many people mistakenly believe that a headache at altitude is "normal" when it is actually AMS. Be willing to admit that you have altitude illness.
 

High Altitude Cerebral Edema (HACE)

AMS is a spectrum of illness, from mild to life-threatening. At the "severely ill" end of this spectrum is High Altitude Cerebral Edema(HACE); this is when the brain swells and ceases to function properly. Obviously, this is a Bad Thing to have happen to you.
HACE, once present, can progress rapidly, and can be fatal in a matter of a few hours. Persons with this illness are often confused, and may not recognize that they are ill.

Cerebral edema is the consequence of increased cerebral blood flow due to hypoxia, There is even risk of coma & death.

Signs and symptoms of HAPE include any of the following:

• Headache is common

• Drowsiness

• Ataxia

High Altitude Pulmonary Edema (HAPE)

Another form of severe altitude illness is High Altitude Pulmonary Edema, or fluid in the lungs. Though it often occurs with AMS, it is not felt to be related and the signs of AMS may be absent. Signs and symptoms of HAPE include any of the following:

• Extreme fatigue

• Breathlessness at rest

• Cough, possibly productive of frothy or pink sputum

• Gurgling or rattling breaths

• Chest tightness, fullness, or congestion

• Blue or gray lips or fingernails

Things to Avoid

Respiratory depression (the slowing down of breathing) can be caused by various medications, and may be a problem at altitude. The following medications can do this, and should never be used by someone who has symptoms of altitude illness (these may be safe in non-ill persons, although this remains controversial):

• Alcohol

• Sleeping pills (acetazolamide is the sleeping tablet of choice at altitude)

• Narcotic pain medications in more than modest doses

The mainstay of treatment of AMS is rest, fluids, and mild analgesics: acetaminophen (paracetamol), aspirin, or ibuprofen. These medications will not cover up worsening symptoms. Descent is always an option, and recovery will be quite rapid.

Trekkers always wonder about how to tell if a headache is due to altitude. Altitude headaches are usually nasty, persistent, and frequently there are other symptoms of AMS; they tend to be frontal (but may be anywhere), and may worsen with bending over. However, there are other causes of headaches, and you can try a simple diagnostic/therapeutic test. Dehydration is a common cause of headache at altitude. Drink one liter of fluid, and take some acetaminophen or one of the other analgesics listed above. If the headache TOTALLY resolves (and you have no other symptoms of AMS) it is very unlikely to have been due to AMS.

Let me say a few words about acetazolamide (Diamox®). This is a medication that forces the kidneys to excrete bicarbonate, the base form of carbon dioxide; this re-acidifies the blood, balancing the effects of the hyperventilation that occurs at altitude in an attempt to get oxygen. This re-acidification acts as a respiratory stimulant, particularly at night, reducing or eliminating the periodic breathing pattern common at altitude. Its net effect is to accelerate acclimatization. Acetazolamide isn't a magic bullet, cure of AMS is not immediate. It makes a process that would normally take about 24-48 hours speed up to about 12-24 hours.

I do not recommend acetazolamide as a prophylactic medication, except under specific limited conditions outlined below. Most people who have a reasonable ascent schedule will not need it, and in addition to some common minor but unpleasant side effects it carries the risk of any of the severe side effects that may occur with sulfonamides. I feel that acetazolamide is indicated under the following conditions:

• Treatment of persons with AMS

• Treatment of persons bothered by periodic breathing at night

• Prophylactically for persons on rapid forced ascents (such as flying into Lhasa, Tibet)

• Prophylactically for those persons who have repeatedly had AMS in the past

Acetazolamide is a sulfonamide medication, and persons allergic to sulfa medicines should not take it.

Common side effects include numbness, tingling, or vibrating sensations in hands, feet, and lips. Also, taste alterations, and ringing in the ears. These go away when the medicine is stopped. Since acetazolamide works by forcing a bicarbonate diuresis, you will urinate more on this medication.

Uncommon side effects include nausea and headache. I have seen a few trekkers whose vision became very blurry after taking only one or two doses of acetazolamide; fortunately they recovered their normal vision in several days once the medicine was discontinued.

Acetazolamide Dosage: