Clinical guidelines for family physicians: high-altitude sickness.
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 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.
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 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 when descent is not possible. Reascent should not be attempted until symptoms resolve and the patient is no longer taking dexamethasone.
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.
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 treatment 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. If both HACE and HAPE are suspected, dexamethasone should be used. Because of concerns of possible cerebral ischemia secondary to hypotension, take care with nifedipine or other pulmonary vasodilators.
High-altitude illness has become a more common concern with increasing global travel. Prevention is paramount, with emphasis on slow ascent. Acetazolamide and dexamethasone may be considered for prevention and treatment of acute mountain sickness and HACE, with nifedipine considered for prevention treatment of HAPE.
* Wilderness Environ. Med. 2010;21:146-55.
* Chest 2008;133:744-55.
DR. VAUGHAN is a first-year resident in the family medicine residency program at Abington (Pa.) Memorial Hospital. DR. SKOLNIK is an associate director of the family medicine residency program at Abington Memorial Hospital.
|Printer friendly Cite/link Email Feedback|
|Title Annotation:||PULMONARY MEDICINE|
|Author:||Skolnik, Neil; Vaughan, William|
|Publication:||Family Practice News|
|Date:||Apr 1, 2012|
|Previous Article:||Limit aspirin for GI cancer prevention to 55-75 age set.|
|Next Article:||Asthma intervention benefits at-risk youth.|