General treatment for altitude illness

People with altitude illness of any severity should stop, rest, rehydrate and consider:

simple analgesia (eg ibuprofen or paracetamol) at standard doses
antiemetic drugs (eg metoclopramide) at standard dosesHarris, 2003 Irons, 2020
specific drug treatment with acetazolamide or dexamethasone
descent, depending on the severity of illness, geographic location and response to initial measures; descent should not be undertaken alone.

For a summary of specific drug treatments and the urgency of descent for each form of altitude illness, see Summary of specific drug treatment and descent recommendations in altitude illness.

Mild acute mountain sickness (AMS ) is a normal physiological response to altitude; symptoms should improve within 1 to 2 nights with rest, rehydration and simple analgesia and antiemetic drugs. Consider descent for:

people with mild AMS that is not responding after 1 to 2 nights of rest and initial treatment
people with moderate AMS that is not responding after 24 hours of rest and initial treatment.

For more severe forms of altitude illness (severe acute mountain sickness, high-altitude cerebral oedema and high-altitude pulmonary oedema), the requirement to descend is more immediate.

For severe acute mountain sickness, descent as soon as possible is recommended until symptoms resolve. If symptoms deteriorate or any signs of high-altitude cerebral oedema (HACE) or high-altitude pulmonary oedema (HAPE) develop, descent is the highest priority. Symptoms of HACE or HAPE typically start to improve following descent of 300 to 1000 metres, but may persist for a number of days in severe cases. Keep exertion to a minimum in people with HAPE because it can exacerbate pulmonary oedema.

Note: The most effective treatment for any altitude illness is descent.

In people with high-altitude cerebral oedema or high-altitude pulmonary oedema, temporary recovery can be achieved with a portable hyperbaric chamber before descent; these may be carried by larger expedition parties. Portable hyperbaric chambers are only a temporising measure pending descent.

If oxygen is available, it can be given by nasal prongs at 2 to 3 L/minute, or at a rate that maintains oxygen saturation above 90% on pulse oximetry. Higher flow rates risk depleting the expedition oxygen supplies too rapidly.

Re-ascent can be considered for some people with acute mountain sickness once symptoms have resolved or reduced. A careful assessment of fitness to re-ascend should be undertaken by the expedition leader or medic. Fitness to re-ascend usually requires acute mountain sickness to have resolved to at least a mild severity at a lower altitude. Re-ascent is not recommended during the same expedition for people with high-altitude cerebral oedema or high-altitude pulmonary oedema (even if resolved).

Note: Descent is the highest priority in treatment of high-altitude cerebral oedema and high-altitude pulmonary oedema; re-ascent during the same expedition is not recommended.

Table 1. Summary of specific drug treatment and descent recommendations in altitude illness
Condition	Specific drug treatment [NB1]	Descent recommendations
mild AMS	consider acetazolamide or dexamethasone	consider descent if symptoms are not improving after 1 to 2 nights of rest and specific drug treatment
moderate AMS	dexamethasone	consider descent if symptoms are not improving after 24 hours of rest and specific drug treatment
severe AMS or HACE	dexamethasone [NB2]	descent as soon as possible is recommended in severe AMS and is mandatory in HACE
HAPE	nifedipine [NB3]	descent as soon as possible is mandatory
concurrent HACE and HAPE	dexamethasone PLUS nifedipine [NB3] [NB4]	descent as soon as possible is mandatory
Note: AMS = acute mountain sickness; HACE = high-altitude cerebral oedema; HAPE = high-altitude pulmonary oedema. NB1: Descent and oxygen are mainstays of treatment for severe AMS, HACE or HAPE; medications are adjuncts. For all altitude illness, consider general measures. NB2: Consider adding acetazolamide if the traveller can tolerate oral medication; additional benefit is uncertain. NB3: Other pulmonary vasodilators may be used as alternatives to nifedipine on specialist advice only. NB4: If a traveller with HAPE has neurological symptoms that do not resolve with oxygen therapy, assume they have concurrent HACE.