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.
- High-altitude cerebral oedema presents with ataxia, confusion, behavioural change, drowsiness or coma and is an immediate descent and oxygen emergency.
- High-altitude pulmonary oedema causes disproportionate exercise intolerance progressing to breathlessness at rest, cough, chest tightness, tachycardia, hypoxaemia and crackles; fever may be mild and does not prove pneumonia.
- Descent is the definitive treatment for HACE and HAPE. Medication must never create permission to continue upward or delay evacuation.
- Acetazolamide accelerates acclimatisation and is used for selected prevention or AMS treatment; it is not an instant oxygen substitute and can cause paraesthesia, diuresis and taste disturbance.
- Dexamethasone can improve severe AMS or HACE while descent proceeds but does not acclimatise the traveller, so rebound is possible after stopping at altitude.
- Nifedipine is a specialist rescue adjunct for HAPE when oxygen and descent are delayed or insufficient; hypotension can make a sick casualty worse.
- Pre-travel assessment is important for previous severe altitude illness, pregnancy, pulmonary hypertension, unstable cardiac disease, significant anaemia, chronic lung disease or an itinerary with unavoidable rapid ascent.
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.
Truncal or gait ataxia, confusion, unusual behaviour, hallucination, marked drowsiness or reduced consciousness at altitude is HACE until proved otherwise. Headache may not be emphasised by an obtunded casualty.
An unexpected drop in pace, breathlessness disproportionate to companions, dry cough, chest tightness and tachycardia may precede resting symptoms. Relative exercise intolerance is often the first practical clue.
Dyspnoea at rest, hypoxaemia out of proportion to peers, crackles, cyanosis and wet or blood-stained cough indicate advanced pulmonary oedema. Descent must not wait for chest imaging.
Hypoglycaemia, hyponatraemia, dehydration, sepsis, carbon monoxide from a stove, pulmonary embolism, asthma, pneumothorax and exhaustion can mimic or coexist. Treat immediate threats without delaying descent from severe altitude illness.
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.
- Reassess symptoms, gait, breathing and function repeatedly; descend if symptoms worsen, fail to improve over the agreed interval or evacuation access may close.
- Resume ascent only after complete recovery, more slowly and with a revised itinerary; medication must not conceal symptoms to preserve a schedule.