Synopsis
Prevent and recognise acute mountain sickness, high-altitude cerebral oedema and high-altitude pulmonary oedema, prioritising descent and oxygen over delayed testing.
- Altitude illness usually follows rapid ascent above about 2,500 metres, although susceptible people can become ill lower; sleeping altitude and ascent rate matter more than fitness.
- Acute mountain sickness requires recent altitude gain with headache and symptoms such as nausea, dizziness, fatigue or disturbed sleep after excluding a better explanation.
- Never ascend to sleep higher while symptomatic. Mild AMS should improve with rest at the same altitude; worsening or persistent illness calls for descent.
Key red flags
Incapacitating headache, repeated vomiting, inability to perform normal activity or worsening symptoms despite rest means the traveller should descend and be observed closely for evolving HACE.
Investigation priorities
Establish exposure intensity and pre-test probability.
Management branches
Headache with compatible symptoms after ascent, without ataxia, rest dyspnoea or altered consciousness.
- Do not ascend farther or sleep higher; rest, avoid alcohol and sedatives, maintain sensible oral intake and tell a companion or leader.
- Use simple analgesia and antiemetic support when safe, and consider acetazolamide under the expedition or travel-medicine plan.
Key medicines
AcetazolamidePrevention in an adult at moderate or high risk: 125 mg orally twice daily, started 1 day before ascent and continued for at least 2 days after reaching the highest altitude; stop on descent if asymptomatic. This is unlicensed and supplements, never replaces, gradual ascent.
DexamethasoneFor severe AMS or HACE, give the protocol emergency loading and repeated regimen while descent proceeds; verify current adult and paediatric instructions.