Prevention and Treatment of High Altitude Sickness
Altitude illness is a potentially lethal phenomenon that physicians should be aware of, particularly during winter months when many people travel to destinations at higher altitudes that may put them at risk. Altitude illness has also become important with the increase in "adventure" travel.
Many of these travelers, especially seniors, will have preexisting conditions that may put them at an even greater risk when they travel to high altitudes.
Understanding the guidelines from the Wilderness Medical Society on acute altitude illnesses can help physicians identify, treat, and even help prevent these conditions.
High altitude illness refers to acute mountain sickness (AMS), high altitude cerebral edema (HACE), and high altitude pulmonary edema (HAPE). Physiologically, HACE is considered the end stage of AMS. HAPE is physiologically distinct from AMC/HACE and warrants different management considerations. These conditions are typically associated with travel to altitudes above 2,500 meters (8,202 feet).
Prevention of AMS and HACE
Prevention strategies should be based on an individual’s risk profile (for example, prior history of altitude illness, or having experienced a rapid gain in altitude).
For those at low risk, prevention is primarily a gradual ascent without medication. Sleeping altitude is more important than the altitude that is reached during the day. Above an altitude of 3,000 meters (9,843 feet), the maximum gain in sleeping altitude per day should be limited to 500 meters (1,640 feet). A rest day every 3-4 days without any altitude gain should be included in the ascent profile.
Medication may be added for those at moderate to high risk. Acetazolamide is the drug of choice. For those intolerant or allergic to acetazolamide, dexamethasone may be used. In special, emergent circumstances necessitating rapid altitude gain, acetazolamide and dexamethasone may be use concurrently. Acetazolamide should be started the day prior to ascent; dexamethasone should be started on the day of ascent. Once the target altitude is reached, prophylaxis may be discontinued after 2-3 days at maximum altitude.
Treatment of AMS and HACE
Descent is the single best treatment. Typically, symptoms resolve with descent of 300-1,000 meters (984-3,281 feet), but descent should continue until symptoms resolve.
It is important to consider alternative diagnoses, because many conditions have similar symptoms. AMS may be treated with nonopiate analgesics and antiemetics without necessarily descending, but stopping the ascent is crucial. Acetazolamide may be used, but it has greater efficacy for prevention than treatment. Dexamethasone is more effective in treating any degree of AMS, but it is reserved for moderate to severe AMS, in which case descent also is important. Once symptoms resolve, ascent may be resumed, although acetazolamide use should be considered. Ascent should never continue if a patient remains symptomatic.
HACE is considered end-stage AMS and is differentiated from severe AMS by neurologic findings, including ataxia, confusion, and altered mental status. HACE may develop as a progression from AMS, or it may occur independently. In addition, HACE and HAPE may develop concurrently.
If HACE is suspected or if AMS is not responding to treatment, then dexamethasone and supplemental oxygen should be started, and descent should be initiated. Supplemental oxygen and portable hyperbaric chambers should be considered in cases in which descent is not possible. Reascent should not be attempted until symptoms resolve and the patient is no longer taking dexamethasone.
Prevention and Treatment of HAPE
Gradual ascent is the primary method of prevention. Nifedipine is the drug of choice for the prevention of HAPE, but it is indicated only in those with a prior history of HAPE. Treatment should start on the day prior to ascent and continue for 5 days once a patient reaches maximum altitude, or when descent is initiated. Salmeterol may be considered as a supplement to nifedipine in those at high risk for developing HAPE. Data on tadalafil, dexamethasone, and acetazolamide in the prevention of HAPE are lacking, and further studies are needed.
Treatment includes descent, supplemental oxygen, and – if descent is not possible or is delayed – the use of a portable hyperbaric chamber. Nifedipine may be considered as an adjunct to the treatments noted above for HAPE. If nifedipine is not available, a phosphodiesterase inhibitor may be tried. Continuous positive airway pressure may be used as an adjunct to oxygen and nifedipine. Acetazolamide, diuretics, and beta-agonists are not useful for treatment of HAPE.
Concurrent HAPE and HACE
If both HACE and HAPE are suspected, dexamethasone should be used. Due to concerns of possible cerebral ischemia secondary to hypotension, care should be taken with nifedipine or other pulmonary vasodilators.
