Acute Mountain Sickness Health Article

Definition

Acute mountain sickness is an illness that can affect mountain climbers, hikers, skiers, or travelers who climb too fast. It usually occurs when people rapidly reach a high altitude (typically above 8,000 feet or 2,400 meters). 

Alternative Names

High altitude cerebral edema; Altitude anoxia; Altitude sickness; Mountain sickness; High altitude pulmonary edema

Causes, incidence, and risk factors

Acute mountain sickness occurs from the combination of reduced air pressure and a lower concentration of oxygen at high altitude. Symptoms can range from mild to life threatening, and can affects the nervous system, lungs, muscles, and heart.

In most cases the symptoms are mild. In severe cases fluid collects in the lungs (pulmonary edema) causing extreme shortness of breath, which further reduces how much oxygen a person gets. Brain swelling may also occur (cerebral edema). This can cause confusion, coma, and, if untreated, death.

The chance of getting acute mountain sickness increases the faster a person climbs into a high altitude. The severity of the symptoms also depend on this factor, as well as how much the person pushed (exerted) him or herself. Persons who normally live at or near sea level are more prone to acute mountain sickness.

Approximately 20% of people will develop mild symptoms at altitudes between 6,300 to 9,700 feet, but pulmonary and cerebral edema are extremely rare at these heights. However, above 14,000 feet, a majority of people will experience at least mild symptoms. Some people who stay at this height can develop pulmonary or cerebral edema.

Symptoms

Symptoms generally associated with mild to moderate altitude illness include:

• Headache
• Difficulty sleeping
• Loss of appetite
• Nausea or vomiting
• Fatigue
• Dizziness or light-headedness
• Rapid pulse (heart rate)
• Shortness of breath with exertion

Symptoms generally associated with more severe altitude illness include:

• Cough
• Shortness of breath at rest
• Chest tightness or congestion
• Bluish discoloration of the skin
• Coughing up blood
• Inability to walk in a straight line, or to walk at all
• Decreased consciousness or withdrawal from social interaction
• Confusion

• Gray or pale complexion (cerebral edema)

Signs and tests

Listening to the chest with a stethoscope (auscultation) reveals sounds called crackles in the lung, which can mean pulmonary edema.

A chest x-ray may be performed.

Treatment

The main form of treatment for all forms of mountain sickness is to climb down (descend) to lower altitude as rapidly and safely as possible. Supplemental oxygen should also be given, if available.

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

Acetazolamide (Diamox) is a drug used to stimulate breathing and reduce mild symptoms of mountain sickness. This drug can cause increased urination. Make sure you drink plenty of fluids. Do not drink alcohol while taking this drug.

Pulmonary edema, the build up of fluids in the lungs, is treated with oxygen, the high blood pressure medicine nifedipine, and, in severe cases, a breathing machine.

The steroid drug dexamethasone (Decadron) may help reduce swelling in the brain (cerebral edema).

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

Expectations (prognosis)

Most cases are mild, and symptoms improve promptly with a return to lower altitude. Severe cases may result in death due to respiratory distress or brain swelling (cerebral edema).

In remote locations, emergency evacuation may not be possible, or treatment may be delayed. These conditions could adversely affect the outcome.

Complications

• Pulmonary edema
• Coma
• High altitude cerebral edema (brain swelling)

Calling your health care provider

Call your health care provider if symptoms of acute mountain sickness develop, even if symptoms resolved when returning to a lower altitude.

Call the local emergency number (such as 9-1-1) or seek emergency medical assistance if severe difficulty breathing develops, if consciousness is decreased, if coughing up blood, or if other severe symptoms are present. If unable to contact emergency help, descend immediately, as rapidly as is safely possible.