Altitude sickness (patient information)

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 * Assistant Editor(s)-in-Chief: Alexandra M. Palmer

Overview
Altitude sickness, also called 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).

What are the symptoms of Altitude sickness?
Symptoms generally associated with mild to moderate altitude 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 altitude sickness include:
 * Bluish discoloration of the skin (cyanosis)
 * Chest tightness or congestion
 * Confusion
 * Cough
 * Coughing up blood
 * Decreased consciousness or withdrawal from social interaction
 * Gray or pale complexion
 * Inability to walk in a straight line, or to walk at all
 * Shortness of breath at rest

What causes Altitude sickness?
Altitude sickness is brought on by the combination of reduced air pressure and lower oxygen concentration that occur at high altitudes. Symptoms can range from mild to life-threatening, and can affect 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. This further reduces how much oxygen enters the bloodstream and reaches vital organs and tissue. Brain swelling may also occur (cerebral edema). This can cause confusion, coma, and, if untreated, death.

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.

Who is at highest risk?
The chance of getting altitude sickness increases the faster a person climbs to a high altitude. How severe the symptoms are also depends on this factor, as well as how hard the person pushes (exerts) himself or herself. People who normally live at or near sea level are more prone to altitude sickness.

When to seek urgent medical care?
Call your health care provider if you have or had symptoms of altitude sickness, even if you felt better when you returned to a lower altitude.

Call 911 or your local emergency number, or seek emergency medical assistance if severe difficulty breathing develops, or if you notice a lower level of consciousness, coughing up of blood, or other severe symptoms. If unable to contact emergency help, descend immediately, as rapidly as is safely possible.

Diagnosis
A doctor will listen to the chest with a stethoscope (auscultation). This reveals sounds called crackles (rales) in the lung, which can mean pulmonary edema.

A chest x-ray may also be performed.

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

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

Acetazolamide (Diamox) is a drug used to stimulate breathing and reduce mild symptoms of altitude sickness. This drug can cause increased urination. When taking this medication, make sure you drink plenty of fluids and do not drink alcohol.

Pulmonary edema, the build-up of fluid in the lungs, is treated with oxygen, the high blood pressure medicine nifedipine or phosphodiesterase inhibitors (sildenafil), and, in severe cases, a breathing machine (respirator).

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.

Where to find medical care for Altitude sickness?
Directions to Hospitals Treating Altitude sickness

What to expect (Outlook/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.

Possible complications

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