Acute Mountain Sickness

Definition

Definition of Acute Mountain Sickness
Acute mountain sickness is an illness that can affect mountain climbers, hikers, skiers, or travelers at high altitude (typically above 8,000 feet or 2,400 meters).

Symptoms

Symptoms of Acute Mountain Sickness
Symptoms range from mild to life-threatening, and can affect the nervous system, lungs, muscles, and heart.

In most cases, the symptoms are mild. Symptoms generally associated with mild to moderate acute mountain sickness include:

1. Difficulty sleeping
2. Dizziness or light-headedness
3. Fatigue
4. Headache
5. Loss of appetite
6. Nausea or vomiting
7. Rapid pulse (heart rate)
8. Shortness of breath with exertion

Causes

Causes of Acute Mountain Sickness
Acute mountain sickness is due to a combination of reduced air pressure and lower oxygen levels at high altitudes.

The faster you climb to a high altitude, the more likely you will get acute mountain sickness. Your symptoms will also depend on the speed of your climb and how hard you push (exert) yourself.

You are at higher risk for acute mountain sickness if:

1. You live at or near sea level
2. You had the illness before

Diagnosis

Diagnosis of Acute Mountain Sickness
Listening to the chest with a stethoscope (auscultation) reveals sounds called crackles (rales) in the lung, which may be a sign of fluid in the lungs.

Treatment

Treatment of Acute Mountain Sickness
Early diagnosis is important. Acute mountain sickness is easier to treat in the early stages.

The main treatment for all forms of mountain sickness is to climb down (descend) to a lower altitude as rapidly and safely as possible. You should not continue climbing if you develop symptoms.

Extra oxygen should be given, if available.

People with severe mountain sickness may need to be admitted to a hospital.

Acetazolamide (Diamox) may be given to help improve breathing and reduce mild symptoms. This drug can cause increased urination. Make sure you drink plenty of fluids and avoid alcohol when taking this drug.

If you have fluid in your lungs (pulmonary edema), treatment may include:

1. Oxygen
2. A high blood pressure medicine called nifedipine
3. A type of drug called a phosphodiesterase inhibitor (such as sildenafil)
4. Lung inhalers beta agonists
5. A breathing machine, in severe cases

Prognosis

Prognosis of Acute Mountain Sickness
Most cases are mild, and symptoms improve promptly when you climb down the mountain to a lower altitude.

Severe cases may result in death due to lung problems or brain swelling.

In remote locations, emergency evacuation may not be possible, or treatment may be delayed. This can have a negative affect on your outcome.

Prevention

Prevention of Acute Mountain Sickness
Altitude sickness is preventable. The body needs time to adjust to high altitude. Physical conditioning has no bearing on this.

A. For people who do not know the rate at which their bodies adjust to high altitude, the following preventive measures are recommended.

• If traveling by air to a ski area above 8,250 feet (2,500 meters), incorporate a layover of 1-2 days at an intermediate altitude.
• Avoid physical exertion for the first 24 hours.
• Drink plenty of fluids, and avoid alcoholic beverages.
• Consume a high-carbohydrate diet.
• If mountain climbing or hiking, ascend gradually once past 8,000 feet (2,400 meters) above sea level
• Increase the sleeping altitude by no more than 1,000 feet (300 meters) per 24 hours. The mountaineer's rule is "climb high, sleep low." This means that on layover days, a climber can ascend to a higher elevation during the day and return to a lower sleeping elevation at night. This helps to hasten acclimatization.

B. The doctor may prescribe acetazolamide (Diamox) to prevent acute altitude sickness. This medication speeds acclimatization.
C. If rapid ascent is unavoidable, as in rescue missions, or if a person is prone to developing HAPE, the doctor may also prescribe nifedipine (Procardia). Nifedipine is normally used to treat high blood pressure.
D. Prevention of high altitude cerebral edema (HACE) is the same as for acute altitude sickness.