Altitude Illness - Cerebral Syndromes Treatment & Management

Updated: Feb 22, 2019
  • Author: N Stuart Harris, MD, MFA, FACEP; Chief Editor: Joe Alcock, MD, MS  more...
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Prehospital Care

Management of AMS follows 3 axioms: (1) no further ascent until symptoms resolve, (2) descend to a lower altitude if no improvement occurs with medical therapy, and (3) at the first sign of HACE, descend immediately. Predicting the eventual severity from the initial clinical presentation is not possible, and patients must be watched closely for progression of illness. [5, 6] A small percentage (< 10%) of persons with AMS will go on to develop HACE, especially with continued ascent in the presence of AMS symptoms.

Descent to an altitude below that where symptoms started is always effective treatment but may not be practical or possible given the topography, weather, the patient's ultimate trekking or climbing goals, or group resources. Accordingly, a descent of 500-1,000 m is usually sufficient. See the image below.

Horse evacuation of nonambulatory altitude illness Horse evacuation of nonambulatory altitude illness. Patient in Khumbu, Nepal. Image courtesy of Dr Peter Fagenholz.

Acetazolamide accelerates acclimatization and thus quickens resolution of the illness, but this may still require 12-24 hours; it is of limited value in HACE because of its relatively slow action. Acetazolamide can be taken episodically without fear of rebound symptoms when it is discontinued. Dexamethasone swiftly reverses symptoms (2-4 h) but does not improve acclimatization. It is the drug of choice for treating HACE and should be given early. Both agents may be used to treat AMS if the victim does not descend. Oxygen is extremely effective, but availability is often limited.

Portable hyperbaric chambers made of coated fabric (eg, Gamow bag, CERTEC, PAC) are now widely available among adventure travel groups on expeditions and in high-altitude clinics. These are all lightweight, coated fabric bags about 2 m long and 0.7 m in diameter. The patient is placed completely within the bag, which is sealed shut and inflated with a manually operated pump, pressurizing the inside to 105-220 mmHg above ambient atmospheric pressure. Depending on the elevation of use, a physiologic (simulated) descent of up to 2,000 m may be achieved within minutes. Continuous pumping is necessary to flush CO2 out of the system, unless a chemical scrubber system is used. Patients are typically treated in 1-hour increments and then are reevaluated. See the images below.

A very ataxic man with high-altitude cerebral edem A very ataxic man with high-altitude cerebral edema (HACE) at 4250 m being assisted toward the Gamow bag.
A fully inflated Gamow Bag in use. A fully inflated Gamow Bag in use.

Importantly, in HACE cases, these chambers should only be used as a means of acute/temporizing care (eg, to improve a patient's ability to more safely participate in their evacuation in technical terrain). They should never be considered as a replacement for actual descent.

Coca leaf tea is widely recommended in South America, on the Internet, and in the popular press as a cure for altitude illness; however, no studies support this claim. Coca leaf tea may act as a mild stimulant and improve well-being at altitude, which may be its primary effect. Garlic, likewise, has been advocated for prophylaxis and treatment of altitude illness. Animal studies show efficacy in preventing hypoxic pulmonary hypertension, but studies in humans are lacking and its use cannot be recommended at this time. Additional medications not shown to have any benefit include calcium channel blockers, naproxen, phenytoin, and antacids. Alcohol and other respiratory depressants, such as benzodiazepines, should be avoided in someone with AMS due to the risk of exaggerated hypoxemia.


Emergency Department Care

All of the symptoms of AMS improve dramatically with descent, and, by the time a patient reaches the emergency department, further treatment is rarely indicated.

Oxygen 4 L/min or to keep SaO2 above 90% should be used in patients who continue to be acutely ill with either severe AMS or HACE after descent.

Dexamethasone should be continued in symptomatic patients with HACE.

Inpatient care

Hospitalization is not indicated for AMS. Hospitalization is usually indicated for patients with HACE, depending on severity. Patients with focal neurologic deficits or persistent mental status changes should be admitted. After descent, care is supportive.

Residual headache or nausea in patients with AMS should be treated symptomatically. Continue dexamethasone for 1-2 days after descent in patients with uncomplicated HACE or until the mental status clears in patients with severe HACE who require hospitalization.



Ataxia due to HACE commonly persists for days to weeks after descent, but persistent mental status changes or the presence of focal neurologic deficits should prompt a complete neurologic evaluation. Brain tumors that suddenly become symptomatic at altitude, Guillain-Barré syndrome, herpes encephalitis, and cortical blindness have all been misdiagnosed as HACE.



Recommendations on staged ascents, by and large, are adequate for the average person, but some persons still become ill despite a slow, staged ascent. Persons traveling to high altitude should allow adequate time for acclimatization and pay careful attention to symptoms. Helpful guidelines to avoid altitude illness include the following:

  • Avoid abrupt ascent to sleeping elevations over 3,000 m (10,000 ft).

  • Spend 1-2 nights at an intermediate elevation (2,500-3,000 m) before further ascent.

  • Above 3,000 m, sleeping elevations should not increase by more than 300-400 m per night.

  • When topography or village locations dictate more rapid ascent, or after every 1,000 m gained, spend a second night at the same elevation.

  • Day hikes to higher elevations, with return to lower sleeping elevations help to improve acclimatization.

  • Drink plenty of water or electrolyte solution. Both sensible and insensible fluid losses are exaggerated at altitude. The average consumption of fluid should be increased to approximately 3-4 liters per day.

  • Avoid overexertion.

  • Avoid alcohol consumption in the first 2 days at a new, higher elevation; in addition to concerns about respiratory depression and exaggerated sleep hypoxemia, an AMS headache the next morning is all too easily dismissed as a hangover.

Many travelers wonder how long acclimatization lasts after a sojourn to high altitude. Some value in preventing AMS may persist for a week or more.

Acetazolamide effectively prevents AMS; it accelerates acclimatization by inducing a bicarbonate diuresis, stimulating ventilation, and improving sleep-breathing patterns. It does not mask symptoms of AMS. Acetazolamide prophylaxis is indicated for persons with an unavoidable rapid ascent, such as flying in to a high city (eg, Lhasa, Tibet; La Paz, Bolivia), or with a history of recurrent AMS. Since it is also useful for treatment, acetazolamide should be in the high altitude traveler's medical kit, along with written instructions. A survey concluded that most trekkers carrying acetazolamide did not know how to use it properly.

Dexamethasone also effectively prevents AMS but does not improve acclimatization. Because of the concern of rebound symptoms and the adverse effect profile, this medication cannot be routinely recommended for prophylaxis.

Ibuprofen may be taken prophylactically to reduce the likelihood of AMS. Taking 600 mg 3 times per day has been shown to decrease AMS symptoms. [7]

In the past, ginkgo biloba had been suggested for AMS prophylaxis. Importantly, a number of recent well-designed studies have found it to be ineffective at preventing AMS. The studies that also included acetazolamide found that acetazolamide alone was effective and that combining ginkgo and acetazolamide did not provide any increased effectiveness. Ginkgo cannot be recommended for AMS. [8, 9]


Long-Term Monitoring

After descent, further outpatient care is not usually indicated for patients with AMS. Patients with mild HACE should have follow-up appointments in 24 hours to check for clearance of symptoms. Patients with concurrent HAPE should be immediately reported to the International HAPE Registry.