ACUTE MOUNTAIN SICKNESS

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

Causes

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 yourself.

You are at higher risk for acute mountain sickness if:

You live at or near sea level;

You had the illness before.

Symptoms

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:

Difficulty sleeping

Dizziness or light-headedness

Fatigue

Headache

Loss of appetite

Nausea or vomiting

Rapid pulse (heart rate)

Shortness of breath with exertion

Symptoms generally associated with more severe acute mountain sickness include:

Bluish discoloration of the skin (cyanosis)

Chest tightness or congestion

Confusion

Cough

Coughing up blood

Decreased consciousness or withdrawal from social interaction

Grey or pale complexion

Inability to walk in a straight line, or to walk at all

Shortness of breath at rest

Exams and Tests

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

A chest x-ray may be performed.

Treatment

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 oedema), treatment may include:

Oxygen

A high blood pressure medicine called nifedipine

A type of drug called a phosphodiesterase inhibitor (such as sildenafil)

Lung inhalers beta agonists

A breathing machine, in severe cases

Dexamethasone (Decadron) may help reduce swelling in the brain (cerebral oedema).

Portable hyperbaric chambers allow hikers to simulate conditions at lower altitudes without actually moving from their location on the mountain. These devices are very helpful if bad weather or other factors make climbing down the mountain impossible.

Prognosis

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 effect on your outcome.

Possible Complications

Coma

Fluid in the lungs (pulmonary oedema)

Swelling of the brain

When to Contact a Medical Professional

Call your health care provider if you have or had symptoms of acute mountain sickness, even if you felt better when you returned to a lower altitude.

Call 911 or your local emergency number if you or another climber has any of the following symptoms:

Severe breathing problems

Altered level of alertness

Coughing up blood

Climb down the mountain immediately and as safely as possible.

Prevention

Tips to preventing acute mountain sickness include:

Climb the mountain gradually

Stop for a day or two of rest for every 2,000 feet (600 meters) above 8,000 feet (2,400 meters)

Sleep at a lower altitude when possible

Learn how to recognize early symptoms of mountain sickness

If you are traveling above 9,840 feet (3,000 meters), you should carry enough oxygen for several days.

If you plan on quickly climbing to a high altitude, ask your doctor about a medication called acetazolamide (Diamox). This drug helps your body get used to higher altitudes more quickly, and reduces minor symptoms. It should be taken the day before you climb, and then for the next 1 to 2 days.

If you are at risk for anemia, ask your doctor if an iron supplement is right for you. Anemia lowers the amount of oxygen in your blood.

While climbing:

Drink plenty of fluids

Avoid alcohol

Eat regular meals, high in carbohydrates

You should avoid high altitudes if you have heart or lung disease.