Advice Ignored on Acute Mountain Sickness
Abstract & Commentary
By Brian G. Blackburn, MD, and Michele Barry, MD, FACP. Dr. Blackburn is Clinical Assistant Professor, Division of Infectious Diseases and Geographic Medicine, Stanford University School of Medicine. Dr. Barry is Senior Associate Dean for Global Health, Stanford University School of Medicine. Drs. Blackburn and Barry report no financial relationships relevant to this field of study.
This article originally appeared in the February issue of Travel Medicine Advisor. At that time it was peer reviewed by Lin Chen, MD, Assistant Clinical Professor, Harvard Medical School; Director, Travel Medicine Center, Mt. Auburn Hospital, Cambridge, Mass. Dr. Chen reports no financial relationships relevant to this field of study.
Synopsis: A retrospective survey of 744 Dutch and Belgian travelers who had ventured to 2500 m (8200 feet) or higher revealed that 25% developed acute mountain sickness. Only half of this group had followed pre-travel advice regarding altitude sickness, and few took preventive acetazolamide.
Source: Croughs M, et al. Acute mountain sickness in travelers who consulted a pre-travel clinic. J Travel Med 2011;18:337-343.
Acute mountain sickness (AMS) is a syndrome that can affect travelers who are not acclimatized and gain altitude too quickly, usually occurring above 2500 m (8200 feet) elevation. Typical symptoms include headache, nausea, dizziness, sleeplessness, anorexia, and fatigue. Although usually benign, life-threatening high altitude cerebral or pulmonary edema (HACE or HAPE) can result if the syndrome is allowed to progress. Pharmacologic treatment and prophylaxis (e.g., acetazolamide) are efficacious,1-3 but perhaps the most important preventative measure is halting ascent at the onset of any AMS symptoms. In addition, if symptoms worsen while travelers rest at the same altitude, they must descend. Predeparture counseling regarding the symptoms and risks of AMS is critical for decreasing the risks of this potentially serious illness.
Consensus guidelines have been published regarding the prevention and treatment of altitude sickness.4,5 These suggest limiting daily ascent to a maximum of 500 m (1600 feet) for activities above 2750 m (9000 feet), adding one acclimatization day for every 1000 m (3300 feet) elevation gained above this altitude, and initiating acetazolamide prophylaxis in certain specific situations.4,5 The authors undertook a retrospective survey of adult travelers to high altitude that were seen at one of four travel clinics in the Netherlands and Belgium before their trip. These patients were given specific written and oral instructions about AMS during the visit, and written surveys regarding AMS were then mailed to all patients after their return.
Overall, 744 persons that slept > 1 night above 2500 m (8200 feet) were included in the study. The age range was 17-76 years (mean, 36); most traveled to South America (74%) or Asia (18%). The maximum sleeping altitude averaged 3950 m (13,000 feet). Above an altitude of 2500 m (8200 feet), 43% of people climbed more than 500 m (1600 feet) per day.
While 658 respondents (88%) read the information they received about AMS from the travel clinic, 160 (22%) did not understand instructions regarding the use of acetazolamide. Although 541 (72%) brought acetazolamide with them, only 116 (16%) took it for AMS prevention; the median dose among such users was 125 mg twice daily (median course, 4 days). Sixty-six (9%) had suffered from AMS previously, and these individuals took acetazolamide prophylaxis twice as frequently as those who had never suffered from AMS (29% vs 14%).
Overall, 184 respondents (25%) had symptoms during their trip that met the definition of AMS; 76% of these resolved within three days. Eighty-seven (47%) continued climbing despite their AMS symptoms, and one-quarter of these individuals experienced some exacerbation of their symptoms. One-hundred two (55%) symptomatic patients took acetazolamide for treatment of AMS (median 375 mg total daily dose for 3 days). Several travelers reported that they did not think their symptoms were severe enough to warrant acetazolamide, or that they were uncertain regarding when they should begin taking it.
Commentary
This retrospective survey of high-altitude travelers who had received advice about AMS from travel clinics before their journey yielded interesting descriptive results. The overall rate of AMS for travelers to this altitude was generally similar to past studies, despite the advice given by the travel clinics.6,7 As has been demonstrated in other settings, predictors of AMS included a past history of AMS, a higher maximum altitude, and spending fewer nights acclimatizing. Younger age and female sex were demographic factors associated with a higher risk of AMS; past studies have been mixed on the relationship of these factors to the development of AMS.6,7
The troubling finding in this study was the strikingly low compliance rate of travelers with the advice they received about AMS. Despite care at travel clinics specifically geared towards addressing the risks of AMS, 43% of travelers climbed more than 500 m (1600 feet) per day when above 2500 m (8200 feet), and only 16% took acetazolamide for prophylaxis of AMS. Of even greater concern, almost half of patients with symptoms of AMS continued to climb. Although the ambitious, fixed itineraries trekkers and climbers frequently embark upon may mean that compliance with advice regarding AMS will always be problematic, improvement of counseling protocols might help alleviate this.
For example, advice might focus on the risks of developing HACE or HAPE if patients continue to ascend with symptoms of AMS, guidelines for the use of acetazolamide might be made clearer, and patients could be advised to build more flexibility into itineraries, so that travelers with AMS might be more likely to rest and acclimatize rather than continuing to ascend. Although the best means to achieve these goals remains uncertain, advice should probably be communicated both orally and in writing, in a standardized manner for all patients. If it seems that unsafe ascent remains likely in a particular patient despite such advice, recommendations regarding inclusion of at least one companion who is trained in the management of altitude sickness, and who would carry pharmacologic (e.g., dexamethasone) and non-pharmacologic (e.g., a Gamow bag for HACE or HAPE) therapy for AMS and its complications might also be considered.
A surprising finding of this study was the apparent ineffectiveness of acetazolamide prophylaxis. The median dose used (125 mg twice daily) was less than the previously recommended prophylaxis dose (250 mg twice daily), and earlier studies did suggest that higher doses were necessary to effectively prevent AMS.8 However, more recent randomized studies in multiple settings have demonstrated the efficacy of 125 mg twice daily for preventing AMS,1-3 and this is now the recommended dose in several consensus guidelines.4,5 While acetazolamide also appeared ineffective at alleviating symptoms of AMS in this study, the dose used (375 mg total daily dose) was lower than the currently recommended dose (250 mg twice daily) for AMS treatment. Use of acetazolamide for treatment of AMS was also erratic in this cohort, again resulting in selection bias.
While intriguing, the results of this study are insufficient to conclude that a change in the recommendations regarding acetazolamide use for AMS are necessary. The key contribution of this study is to increase awareness among travel medicine practitioners that their advice regarding AMS will not be followed by many high-altitude travelers, and that clinic practices may need to be adapted to this unfortunate reality of caring for such patients.
References
1. Basnyat B, et al. High Alt Med Biol 2006;7:17-27.
2. Basnyat B, et al. High Alt Med Biol 2003;4:45-52.
3. van Patot MC, et al. High Alt Med Biol 2008;9:289-293.
4. Hackett PH, et al. Altitude Illness. In: Brunette GW, Kozarsky PE, Magill AJ, Shlim DR (eds). CDC Health Information for International Travel 2012. New York: Oxford University Press; 2012:60-65.
5. Luks AM, et al. Wilderness Environ Med 2010;21:146-155.
6. Hackett PH, et al. N Engl J Med 2001;345:107-114.
7. Basnyat B, et al. Lancet 2003;361:1967-1974.
8. Dumont L, et al. BMJ 2000;321:267-272.
A retrospective survey of 744 Dutch and Belgian travelers who had ventured to 2500 m (8200 feet) or higher revealed that 25% developed acute mountain sickness. Only half of this group had followed pre-travel advice regarding altitude sickness, and few took preventive acetazolamide.You have reached your article limit for the month. Subscribe now to access this article plus other member-only content.
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