Acute mountain sickness can occur when a person who is used to being at a low altitude ascends to a higher altitude.
It is the most common type of high-altitude illness and occurs in more than one-fourth of people traveling to above 3500 m (11 667 ft) and more than one-half of people traveling to above 6000 m (20 000 ft). Symptoms include headache, fatigue, poor appetite, nausea or vomiting, light-headedness, and sleep disturbances. Symptoms usually occur 6 to 12 hours after ascent and can range from mild to severe. Symptoms usually improve after 1 to 2 days if there is no further ascent, but they can sometimes last longer. In less than 1% of cases, symptoms can progress to high-altitude cerebral edema, a life-threatening condition marked by symptoms of wobbly gait, confusion, and decreased consciousness.
Acute mountain sickness is a clinical diagnosis based on typical symptoms in the context of ascending to high altitudes. Physical examination is usually normal. It is usually not difficult to diagnose in otherwise healthy adults; however, in children and people with baseline health problems, it can be more difficult to diagnose. No blood work or imaging tests are necessary, except to rule out other diagnoses. Symptoms usually improve after treatment with supplemental oxygen; sometimes this can be used as a diagnostic “test” for acute mountain sickness.
Several questionnaire-based diagnostic tools can be used to diagnose acute mountain sickness. Examples include the Acute Mountain Sickness–Cerebral (AMS-C) score, the Hackett score, the Lake Louise Questionnaire Score (LLQS), and the Clinical Functional Score (CFS). An article in the November 14, 2017, issue of JAMA discusses the accuracy of these various diagnostic tools.
People with acute mountain sickness should hold off on ascending to higher altitudes until their symptoms have resolved. Mild cases are usually treated with supportive care including rest, pain medications for headache, and hydration. More severe cases can be treated with oxygen given through a nasal cannula as well as with prescription medications such as acetazolamide, dexamethasone, or both. If symptoms are severe or persistent, descent is recommended.
Prevention tactics for acute mountain sickness include regular exposure to altitude (preacclimatization) and a gradual (slow) ascent, especially when it comes to sleeping altitude (aim for less than 400 m [1333 ft] difference between each night). Drink plenty of water and avoid alcohol. People with a history of acute mountain sickness should be especially careful and can take acetazolamide before ascent to prevent or decrease symptoms.
People with heart disease, lung disease, anemia, or obstructive sleep apnea should talk to their doctors before traveling to high altitudes.
Centers for Disease Control and Preventionwwwnc.cdc.gov/travel/page/travel-to-high-altitudes
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Source: Collet TH. Does this patient have acute mountain sickness? the rational clinical examination systematic review. JAMA. doi:10.1001/jama.2017.16192
Topic: Travel Medicine
Jill Jin. Acute Mountain Sickness. JAMA. 2017;318(18):1840. doi:10.1001/jama.2017.16077