Acute Mountain Sickness


Acute mountain sickness is caused by inadequate adaptation to low oxygen pressure at high altitude. Each lowlander may soon be confronted with it after a 4-8 hours stay above 2000m, 3-6 hours from 3500 - 4000 m and 2-4 hours from 5000 m. Individuals who travel directly to high altitude areas must certainly take into account the possibility of acute altitude sickness. Sensitivity to acute altitude sickness varies individually and is not dependent on the degree of physical training, nor the number of times one has stayed at high altitude. The individual sensitivity is fairly constant: if you have already suffered, then you will have more chance to suffer again. People with heart and lung decease are at higher risk. 


Symptoms may begin within 3 days after arrival and may take 2-5 days if stayed at the same altitude.

At first the symptoms of acute mountain sickness are mild: the patient complains of headache, fatigue, loss of appetite, nausea, insomnia, dizziness and general malaise. The severity of symptoms depend mainly on the altitude and the number of days that has been acclimatized around 2,000, the efforts that were delivered and whether an overnight stay was done. The symptoms may increase (vomiting, dry cough and shortness of breath at rest, ("one can no longer speak without gasping for breath "), and sometimes it eventually develops into life-threatening conditions (rare <3000 m)as high altitude pulmonary edema (HAPE) (fluid in the alveoli, with a dry cough that gets worse, fever and dyspnea at rest) and / or high altitude cerebral edema (HACE) (swelling of the brains, with headaches that no longer respond to analgesics, unsteady walk, increased vomiting and gradual loss of consciousness).



This important and consists of the following measures:

- First stay a few days at an intermediate altitude (between 1500 and 2500 m), heart rate (Pulse) at rest will remain below 100 per minute. During the day can be climbed higher to improve acclimatization

- Plan a flexible itinerary with additional rest days

- Avoid excessive alcohol and sleeping pills

- Maintain adequate fluid intake (at least 3 liters, but usually much more, the urine should be clear), even if no thirst is present, because the water loss through heavier breathing increases (eg by hyperventilation in an environment with reduced atmospheric pressure). The use of acetazolamide (Diamox ®) creates yet another additional moisture loss.

- Persons who have previously suffered from acute altitude sickness can take preventively acetazolamide (Diamox ®) one 250 mg tablet two times a day (about 7 mg per kg body weight) starting 1 day before reaching up to 3000m to 2 days after reaching final height. The second tablet best at the latest around 16:00 in the afternoon, so the diuretic effect has faded against bedtime. Acetazolamide (Diamox ®) improves acclimatization and does not mask any symptoms. This drug must prescribed by a physician.

- Tingling in the limbs and taste disturbances (eg when ingestion beer or other gaseous drinks) are frequent side effects. Acetazolamide (Diamox ®) is preferably not taken by people with an allergy to sulphonamides and not to pregnant women, rarely to children (5mg/kg per day in two doses).

Acetazolamide (Diamox ®) 250 mg at bedtime works great against insomnia at high altitude (There is a chance that at once a night you need to urinate).

- Persons who trek above 3000m can bring acetazolamide (Diamox ®) with them and take it at the first symptoms of altitude sickness (see below).


Treatment of mild acute mountain sickness:

- Do not ascend further, there is nothing better than an extra day to rest and if possible sleep 500 m lower.

- Start at the first signs of altitude sickness, meaning headaches and possible other complaints, with one tablet of Diamox ® 250mg, 2 times a day for 2-3 days or less if you descend sooner. This speeds up acclimatization.

- If necessary, take 1 gr aspirin or paracetamol or 600 mg of ibuprofen for headache and metoclopramide or domperidone for nausea.

- When the symptoms persist or increase one must at least descend 500 m!

- Once the symptoms have disappeared, one can cautiously continue climbing.


Treatment of severe acute mountain sickness:

- A rapid descent below 2500 m is necessary for the survival of the individual.

- If possible, oxygen, or, failing that, an inflatable portable hyperbaric "Room" (gamov bag with foot pump) can be used. This offer only a temporary solution because its effect subsides after several hours. Hence it always should be combined with the administration of Diamox ®, Adalat ® and / or corticosteroids, and that always a a rapid descent should be made.

For medical group supervisors in the high mountains, it is also useful to have following drugs:

- In case of cerebral edema: corticosteroids (1) dexamethasone (Decadron ®) 8 mg given initially, then 4 mg every 6 hours (or 32 mg once in case of high emergency), dexamethasone (Decadron) is no longer available on the Belgian market, but can be prescribed majestic (2) methylprednisolone (Medrol ®) 48-64 mg as initial dose, then 24-32 mg every 6 hours (for the exact dosing there is no scientific data available).

- In case of pulmonary edema: Adalat ® (nifepidine) 10 mg sublingually together with Adalat ® Retard 20 mg as attack treatment, then Adalat ® Retard 20 mg every 6 hours.

Sildenafil (Viagra) has been shown to be useful for the prevention and treatment of high-altitude pulmonary edema associated with altitude sickness such as that suffered by mountain climbers. While this effect has only recently been discovered, sildenafil is already becoming an accepted treatment for this condition, in particular in situations where the standard treatment of rapid descent has been delayed for some reason


All this should in no way postpone a fast and lifesaving descent!

Oxygen Pressure Model

Y axis shows the oxygen pressure

X axis shows the altitude

The graph shows that oxygen pressure decreases as altitude increases.

The air always holds 21% of oxygen but  when the pressure decreases a volume of air will contain less molecules of oxygen but the percentage oxygen remains constant. The number shown at each altitude is the change in oxyen molecules in a volume of air, from 100% at sea level to 33% at 9000 meters.