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Acute Mountain Sickness

Last updated April 4, 2018

Approved by: Maulik P. Purohit MD, MPH

Acute Mountain Sickness (AMS) represents the spectrum of symptoms that develop in individuals who travel to high altitudes and is commonly seen in mountain climbers.


What are the other Names for this Condition? (Also known as/Synonyms)

  • Altitude Anoxia
  • Soroche
  • The Altitude Bends

What is Acute Mountain Sickness? (Definition/Background Information)

  • Acute Mountain Sickness (AMS) represents the spectrum of symptoms that develop in individuals who travel to high altitudes
  • It typically affects those who are not acclimatized to high altitudes. The low oxygen levels and reduced air pressure at high altitude is the primary reason of developing this condition
  • AMS is commonly seen in mountain climbers, hikers, skiers, and travelers, who visit places that are located at elevated locations, above the mean sea level
  • Depending on the severity of symptoms, Acute Mountain Sickness can be classified into 3 types:
    • Mild AMS
    • Moderate AMS
    • Severe AMS
    • Jaw pain
    • Family history of cardiovascular disease
  • Breathing difficulty, fatigue, lightheadedness, nausea, and vomiting are some of the common signs and symptoms of Acute Mountain Sickness. Severe sickness may cause complications such as cerebral (brain) and pulmonary (lung) edema and coma
  • Treatment of Acute Mountain Sickness includes moving the individual to lower altitudes and oxygenation of blood. Early diagnosis and immediate management of the condition can avert adverse long-term effects
  • The most important preventive measure for Acute Mountain Sickness is to ascend slowly and gradually to higher altitudes

Who gets Acute Mountain Sickness? (Age and Sex Distribution)

  • Acute Mountain Sickness affects individuals of all age groups and both sexes
  • Children are at increased risk of developing this condition

What are the Risk Factors for Acute Mountain Sickness? (Predisposing Factors)

Risk factors associated with Acute Mountain Sickness include:

  • Past history of similar illness
  • Individuals living at lower altitudes who visit or travel to higher altitudes are at  risk
  • Lack of proper acclimatization while moving to elevated altitudes
  • Strenuous physical exertion at such high altitudes
  • Individuals with a history of underlying lung disease such as COPD and asthma
  • Obesity
  • Alcohol and narcotic abuse

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases ones chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others.

Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.

What are the Causes of Acute Mountain Sickness? (Etiology)

  • Acute Mountain Sickness primarily develops due to low level of oxygen and lowered air pressure at high altitudes
  • The faster one’s ascent to high altitudes, the higher is the risk of developing AMS. The condition is typically observed over 8,000 feet (about 2,400 m above mean sea level)

What are the Signs and Symptoms of Acute Mountain Sickness?

The symptoms of Mountain Sickness develop due to lack of proper oxygenation of the various tissues of the body. Mild symptoms may be experienced during the acclimatization phase, which typically occurs during the first few days of reaching the high altitude.

Acute Mountain Sickness may cause the following signs and symptoms:

  • Difficulty in breathing, shortness of breath with mild exertion
  • Fatigue
  • Lightheadedness or dizziness
  • Sleeping disturbances
  • Nausea and vomiting

Severe forms of AMS may lead to the following signs and symptoms:

  • Cyanosis: Bluish discoloration of the skin that occurs due to a lack of proper oxygenation of blood
  • Chest pain due to decreased oxygen supply to the heart
  • Headache, confusion, and loss of consciousness due to decreased blood supply to the brain
  • High altitude pulmonary edema: It is a severe condition in which fluid collects in the lungs that leads to severe shortness of breath and may even be life-threatening. Individuals with this condition may also complain of coughing-up of blood

How is Acute Mountain Sickness Diagnosed?

The diagnosis of Acute Mountain Sickness is typically based on the history, physical examination, and laboratory testing.

  • A travel history may typically reveal visits to high altitude places that may be correlated with the above-mentioned signs and symptoms
  • Physical examination may show signs of decreased oxygenation of the body tissues, which may include bluish discoloration of the skin and fluid collection in the lung
  • Lab tests that may be performed include:
    • Pulse oximetry to determine the level of oxygen in blood
    • Chest X-ray to observe the collection of fluid in lungs
    • Other tests may be ordered depending on the complexity of the condition            

Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.

What are the possible Complications of Acute Mountain Sickness?

Complications may develop due to delayed diagnosis and treatment of early sickness. The following complications may develop due to Acute Mountain Sickness:

  • High altitude pulmonary edema (HAPE) - collection of fluids in the lung that may lead to respiratory failure
  • High altitude cerebral edema (HACE) - the swelling of the brain due to accumulation of fluid in the brain
  • Coma, due to long-term oxygen-deprivation to the brain

If AMS is not treated promptly on time, it may ultimately result in death.

How is Acute Mountain Sickness Treated?

It is of prime importance that the affected individuals be brought to lower altitudes, which is the first step towards treatment. The treatment of Acute Mountain Sickness depends on the severity of the condition. It may include:

  • Mild Acute Mountain Sickness is treated by providing oxygen to the patient
  • Moderate Acute Mountain Sickness: Medications, such as acetazolamide, may be given along with oxygen

Severe Acute Mountain Sickness - for patients with pulmonary edema, the following treatment is given:

  • Oxygen
  • Nifedipine: It is a drug to reduce the blood pressure
  • Inhalers, such as albuterol, may be given to improve breathing
  • For very severe forms of the disease, the patient may be put on a breathing machine (mechanical ventilator)
  • Patients with cerebral edema are given steroids such as dexamethasone

How can Acute Mountain Sickness be Prevented?

Preventive measures for Acute Mountain Sickness include:

  • Hikers, skiers, mountain climbers, and adventure seekers should be aware of or be educated on Mountain Sickness
  • Acclimatization: It is the most important factor that can help prevent the condition from occurring. In this process, an individual ascends to high altitudes in a step-wise manner so that he/she may get used to the altitude change and develop appropriate breathing capacity, before climbing or moving to higher altitudes
  • At very high altitudes, one’s physical exertion should be minimized and also, a proper rest is important between exertion spells
  • Pre-medication with drugs, such as acetazolamide, may be helpful in selected group of individuals

What is the Prognosis of Acute Mountain Sickness? (Outcomes/Resolutions)

  • Early diagnosis and immediate management of Acute Mountain Sickness does not pose any adverse long term effects on the patients
  • Overall, the prognosis of AMS is good with early intervention

Additional and Relevant Useful Information for Acute Mountain Sickness:

The following DoveMed website link is a useful resource for additional information:

https://www.dovemed.com/healthy-living/healthy-lungs/

What are some Useful Resources for Additional Information?


References and Information Sources used for the Article:


Helpful Peer-Reviewed Medical Articles:


Reviewed and Approved by a member of the DoveMed Editorial Board
First uploaded: Aug. 4, 2015
Last updated: April 4, 2018