MOUNTAINEERING INFORMATION ARTICLES

Acute Mountain Sickness | High Altitude Sickness Prevention

Altitude - Related Sickness and Illnesses

Altitude Related Sickness is the bane of mountaineers, along with Frost Bite and Dehydration. But it can be prevented by following the measures written down below. Knowing them is the key to have a safe and hassle-free climb.

Acute Mountain Sickness, Altitude Sickness or AMS

Acute Mountain Sickness is also often called Altitude Sickness. The symptoms of AMS can be unpleasant enough to spoil your climb. In some cases, it also can be fatal. However, if you understand the cause of AMS then you can take many steps to avoid it or minimize its effects.

Atmospheric pressure and the oxygen content of the air decrease in an approximately exponential manner as altitude increases. This means that as you climb higher, the breath you take contains less oxygen. For most climbers, this effect becomes apparent at around 3000 metres.

Acclimatization is the resetting of your physiological mechanisms which allows the body to return oxygen levels in the tissues to normal or near-normal. As this process is not instantaneous, and when your rate of ascent is faster than the body's ability to adjust to the gain in altitude, AMS occurs. The symptoms of AMS can be unpleasant, serious, or even fatal. It is therefore essential that your own rate of ascent should allow for this adjustment. Keep in mind that there is a lot of variation between individuals, but each person's response to altitude is fairly constant on different occasions, given similar conditions and speed of ascent.

Symptoms and Treatment
AMS develops usually in the first eight to 24 hours at high altitude. Below 3000 meters, it occurs less often: mild symptoms include headache, poor appetite, dizziness, drowsiness, shortness of breath, nausea, fatigue, and poor sleep quality. At this stage, you should stop your ascent. Rest, have frequent meals, take mild painkillers, and keep on drinking water. Do not take alcoholic drinks. If the symptoms worsen to severe headache and vomiting, stop your ascent and descent to a lower altitude where the symptoms abate after a day or two of rest. After that, you could resume the climb.

In its most severe form, high altitude sickness can progress to either Pulmonary Oedema (fluid on the lungs) or Cerebral Oedema (swelling of the brain).

High Altitude Pulmonary Edema (HAPE)

Pulmonary Oedema is a life-threatening medical emergency. It arises very quickly and has been known to cause death less than 40 hours after a rapid climb to 3000 meters. A warning sign is to observe the person who is the fittest in the group at the start of the climb. If that person's fitness decreases quickly as he or she climbs higher, then he or she might have contracted it. Another sign is extreme weakness going uphill.

Symptoms and Treatment
Symptoms include blue or gray lips or fingernails, a cough with bloody or foamy sputum, shortness of breath, general weakness, and a gurgling sound in the chest. If these symptoms occur, then immediately descend to a lower elevation as soon as possible in order to take no risks. Pulmonary oedema can rapidly progress to coma and death if you keep on climbing. However, if you descend just a few hundreds meters, the symptoms will diminish rapidly.

High Altitude Cerebral Edema (HACE)

Cerebral Oedema is the most serious sickness of the three mentioned above. Symptoms include a severe headache, staggering, and hallucinations, and the condition can lead to coma and death. It rarely occurs below 4200 meters. As with Pulmonary Oedema, immediately carry the victim to a lower elevation.

Altitude Sickness Prevention
The best thing to do is to avoid AMS, HAPE or HACE.

Slow Ascent
The most important thing is to avoid AMS by acclimatizing properly by a gradual ascent. A recommended rate of ascent is to climb no more that 500 meters a day over an altitude of 3000 meters. In addition, you could also take a rest day every third day. If this is not possible, because of the position of the huts or campsites, you could also do staging, where you remain at an intermediate altitude between 3000 and 4000 meters for an extra day before ascending any further.

Also, always sleep at a lower altitude than the highest point reached that day.

Drink, drink, and drink some more!
Although dehydration does not cause Altitude Sickness, it does decrease physical performance and the ability to generate heat. This will contribute to chilling and fatigue, which then could lead to Altitude Sickness, as well as hypothermia and frostbite. Drink at least 4 liters of water a day. Six liters is not too much.

Diamox® or Acetazolamide
Acetazolamide or Diamox® 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.

Acetazolamide is not recommended as a prophylactic medication, except under specific limited conditions outlined below.

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

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.

Common side effects include numbness, tingling, or vibrating sensations in hands, feet, and lips, 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.

Myths about DIAMOX
Among climbers, there are a lot of myths about acetazolamide. Let's clarify these:

Acetazolamide hides symptoms.
Acetazolamide accelerates acclimatization. As acclimatization occurs, symptoms resolve, which directly reflects improving health. Acetazolamide does not cover up anything - if you are still sick, you will still have symptoms. If you feel well, you are well.
Acetazolamide will prevent AMS from worsening during ascent.
Acetazolamide DOES NOT PROTECT AGAINST WORSENING AMS WITH CONTINUED ASCENT.
Acetazolamide will prevent AMS during rapid ascent.
This is actually NOT a myth, but rather a misused partial truth. Acetazolamide does lessen the risk of AMS, that's why we recommend it for people on forced ascents. This protection is not absolute, however, and it is foolish to believe that a rapid ascent on acetazolamide is without serious risk. It is still possible to ascend so rapidly that when illness strikes, it is likely to be sudden and severe, and fatal.
If acetazolamide is stopped, symptoms will worsen.
There is no rebound effect. If acetazolamide is stopped, acclimatization slows down to your own intrinsic rate. If AMS is still present, it will take somewhat longer to resolve; if not - well, you don't need to accelerate acclimatization if you ARE acclimatized. You won't become ill simply by stopping acetazolamide.

What you have read are important information about Altitude Related Illnesses. Knowing the right thing to do during climbs lessens the possibility of such debilitating, even fatal Illnesses. Nothing beats the feeling of being on top of the world so climb slowly but surely and soon enough you will be looking down on the world below you. Don't let Altitude Related Illnesses spoil that experience.