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Acute altitude illness

Definition
Acute altitude illness is a group of conditions that can develop when non-acclimatized individuals ascend to high altitudes (> 2,500 meters) too quickly. These conditions include acute mountain sickness, high-altitude cerebral edema, and high-altitude pulmonary edema.
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Pathophysiology
The pathophysiology of acute altitude illness is not completely understood, but it is known to be related to the body's response to hypoxia, or lack of oxygen, at high altitudes. This hypoxic environment can lead to tissue hypoxia, which can then trigger a series of physiological changes that result in the symptoms of acute altitude illness.
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Epidemiology
The prevalence of acute altitude illness in the US is estimated at 65,000 per 100,000 population.
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Disease course
The clinical manifestations of acute altitude illness can vary depending on the specific condition. Symptoms of acute mountain sickness include headache, dizziness, nausea, and vomiting. High-altitude pulmonary edema is characterized by orthopnea, breathlessness at rest, cough, and pink frothy sputum. High-altitude cerebral edema can lead to ataxia, decreased consciousness, and in severe cases, coma and brain herniation.
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Prognosis and risk of recurrence
The prognosis of acute altitude illness is generally good if the individual descends to a lower altitude.
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Key sources
The following summarized guidelines for the management of acute altitude illness are prepared by our editorial team based on guidelines from the Wilderness Medical Society (WMS 2023) and the European Respiratory Society (ERS 2017).
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Guidelines

1.Respiratory support

Supplemental oxygen
Consider administering ongoing supplemental oxygen when available to raise SpO2 to > 90% or relieve symptoms while waiting to initiate descent or when descent is impractical.
B
Administer supplemental oxygen when available to achieve SpO2 of > 90% or relieve symptoms while waiting to initiate descent when descent is not feasible and during descent in severely ill patients.
A
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  • Positive airway pressure

  • Portable hyperbaric chambers

2.Medical management

Acetazolamide: consider administering acetazolamide for the treatment of patients with acute mountain sickness.
B
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  • Corticosteroids

  • Nifedipine

  • PDE5 inhibitors

  • Beta-agonists

  • Analgesics

3.Nonpharmacologic interventions

Descent: advise descent in patients with severe acute mountain sickness, high-altitude cerebral edema, or high-altitude pulmonary edema.
A

4.Specific circumstances

Patients with high altitude-induced central sleep apnea
Recognize that healthy lowlanders travelling to altitudes > 1,600 m may experience central sleep apnea (high-altitude periodic breathing), with severity increasing as altitude increases.
B
Consider offering oxygen-enriched air or acetazolamide to reduce high-altitude periodic breathing and improve nocturnal oxygen saturation in healthy lowlanders staying at altitude. Offer combined treatment with acetazolamide and automatic positive airway pressure to prevents central apneas and improve nocturnal oxygen saturation.
C

5.Preventative measures

Gradual ascent: advise gradual ascent (a slow increase in sleeping elevation) for the prevention of acute mountain sickness and high-altitude pulmonary edema.
B

More topics in this section

  • Preacclimatization

  • Chemoprophylaxis (acetazolamide)

  • Chemoprophylaxis (corticosteroids)

  • Chemoprophylaxis (nifedipine)

  • Chemoprophylaxis (tadalafil)

  • Chemoprophylaxis (salmeterol)

  • Chemoprophylaxis (analgesics)

  • Chemoprophylaxis (ginkgo biloba)