Approach

In the vast majority of cases, acute mountain sickness (AMS), high-altitude pulmonary edema (HAPE), and high-altitude cerebral edema (HACE) can be prevented by ascending slowly once above altitudes of >2500 m.[29]​ In those patients who are prone to AMS or have to ascend quickly, acetazolamide or dexamethasone may be given prophylactically.[37][38][39]​ Although both have been shown to be effective in preventing AMS, acetazolamide is preferred because the side effects of dexamethasone are considerable.[12][17][40][73][74][75]​​ Regular doses of acetazolamide have been shown to be effective;​​ however, higher doses are associated with side effects such as paraesthesias, commonly experienced in the hands and feet.[41][76][77][78]​​

Prophylactic agents such as nifedipine and dexamethasone reduce the incidence of HAPE in individuals with a previous history of radiographically documented disease.[45][79]​​​ Nifedipine is preferred because its effectiveness and safety profile are well understood.[29]​ The use of these agents in combination has not been studied. There is no evidence to support the use of prophylactic agents in the prevention of HACE.

In patients who develop high-altitude illness the STOP, REST, TREAT, and DESCEND approach should be followed. This involves stopping and resting once symptoms arise, instigating treatment once a diagnosis has been made, and descending whenever necessary. Patients with AMS can resume their ascent once symptoms resolve, and it is advisable to use pharmacological prophylaxis before continuing. Further ascent or re-ascent to a previously attained altitude must not be attempted in the presence of continuing symptoms.[29]

In cases where the diagnosis is uncertain, the STOP, REST, TREAT, and DESCEND approach should still be followed. In these cases either rest or descent depending upon the nature of the symptoms is advised.

In HAPE and HACE the effectiveness of medical treatment is very limited and can only slow down the onset of the condition. Rapid descent is the only reliable treatment option. It can often be life-saving.

Wherever possible, those with HAPE and HACE should be treated in a hospital environment if they reach such facilities prior to making a full recovery.

Acute mountain sickness (AMS)

Headaches are treated with fluids and simple analgesics such as paracetamol. Non-steroidal anti-inflammatory drugs (NSAIDs) such as aspirin or ibuprofen should be used with caution because there is anecdotal evidence that there is a significant risk of gastrointestinal bleeding at high altitude.[80][81]​ Anti-emetics may be used if the patient complains of nausea and vomiting.

One Cochrane review found that acetazolamide or dexamethasone may reduce symptom severity compared with placebo (low quality evidence).[82] In patients refractory to rest and symptomatic therapy, acetazolamide, dexamethasone, and oxygen may be used under medical supervision. However, these may take several hours to work and can initially worsen symptoms.[79][83][84]​ If symptoms persist descent is the treatment of choice.[6]

Sleep disturbance can be treated with either acetazolamide or a hypnotic.

High-altitude pulmonary edema (HAPE)

The mainstay of treatment is descent to a lower altitude. When descent is delayed a simulated descent using supplemental oxygen or a portable hyperbaric chamber may be used. Patients should be kept warm and, if clinically dehydrated, should be given replacement fluids of a type, route, and volume appropriate to their overall clinical condition and that avoids fluid overload.

The calcium-channel blocker nifedipine inhibits hypoxic pulmonary vasoconstriction and reduces pulmonary artery pressure;​​ therefore, it can be used in both prophylaxis and treatment of HAPE.[3]​​[38][57]​​ Other agents such as dexamethasone have only been shown to be effective in prophylaxis.

It should be noted that in confirmed cases of HAPE where drugs, oxygen, or a hyperbaric bag have been used, their role is purely to buy time for the vital descent. Further ascent should not be considered.

High-altitude cerebral edema (HACE)

The mainstay of treatment is descent or simulated descent using supplemental oxygen or a portable hyperbaric chamber. In HACE, dexamethasone often improves the clinical situation and makes evacuation easier. Although the duration of the treatment is not clear, once a course of dexamethasone has been started this should be continued until the person has reached low altitude.[3][14]

As with HAPE, if drugs, oxygen or a hyperbaric bag are used, their role is purely to buy time to arrange the vital descent. Further ascent should not be considered.

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