Abstract
To the Editor:
We read with interest the letter “Trekkers' Awareness of Acute Mountain Sickness and Acetazolamide”
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in the Winter 2008 issue of the Journal. The authors found that among trekkers in the Everest region of Nepal, there was a poor understanding of acute mountain sickness (AMS) and acetazolamide. This finding is similar to that of other studies in high altitude regions2,3 where trekkers were asked directly about their knowledge. Another approach to attempt to evaluate what a population knows or believes about a topic may be to examine behaviors related to that topic. This is what we attempted to do in 2003 at Manang in the Nepal Himalaya (3469 m). We surveyed a convenience sample of 307 of the 1316 trekkers who attended the Himalayan Rescue Association lectures (Table 1) to determine whether they took steps to prevent or treat AMS, including using acetazolamide where appropriate. We were interested in looking at the pattern of usage of acetazolamide, particularly in those at increased risk for AMS. The increased risk group included trekkers who had had a previous episode of AMS when at altitudes above 2500 m and those who came up to Manang at an accelerated rate (4 days or fewer from below 1000 m). The following details were queried: Yes or no response to a history of symptoms consistent with AMS on this trek. (Lake Louise Consensus definition was used, that is, headache plus 1 of the following: anorexia, nausea, or vomiting; fatigue or weakness; dizziness or lightheadedness; or difficulty sleeping. Severity of illness was not stratified.) Prior exposure to high altitude (over 2500 m) and whether or not they had suffered from AMS on those occasions. Rate of ascent (from less than 1000 m to Manang at 3469 m). Yes or no response to use of acetazolamide, as well as whether acetazolamide was being used for prevention or for treatment of AMS, and the dosage being used. Other medications being taken.
Characteristics of trekkers surveyed
This questionnaire examined the behavior and experiences of trekkers in relation to altitude illness and use of acetazolamide without attempting to directly assess their knowledge of these issues. We found that 35% of the trekkers we surveyed had a symptom complex consistent with AMS at some point on the way up to or after arrival at Manang (3469 m). The incidence of AMS in a population varies depending on the altitude reached, the speed of ascent, and individual variation. Our finding was consistent with the literature 4 and so we believe it reflected the true incidence within our group.
Thirty trekkers (approximately 10% of those surveyed) used acetazolamide at some point in their journey, 13 for prevention, 10 for treatment, and in 7 cases the reason for use was unclear. None of those who used acetazolamide for prevention of AMS developed altitude illness on the current trip.
In examining the subgroups of interest, we found that of the 8 trekkers who completed the trip in 4 days or less, 5 had suffered a symptom complex consistent with AMS. Of this group of 8, none had taken acetazolamide for treatment. Only 1 had taken it for prevention and was symptom free.
Ten of the 109 people who had been to high elevations (over 2300 m) at least once before admitted to having had altitude illness on previous trips. Of these, only 1 took acetazolamide for secondary prevention. Four of the remaining 9 complained of symptoms suggestive of AMS at some time during the current trip. Of these 4, only 2 were taking acetazolamide for treatment (Table 2).
Acetazolamide use among high-risk trekkers
Actz, acetazolamide; Rx, used for treatment of AMS; Prev, used for prevention of AMS; Sx, symptomatic of AMS.
No consistent dosing of acetazolamide was used by trekkers, with amounts ranging from 125 mg daily to 250 mg twice daily, whether for prevention or treatment.
Although we did not expect all trekkers who might benefit from the use of acetazolamide to take it, we were surprised at the very low number that did. One possible reason for this might be lack of knowledge regarding the use of acetazolamide, but another might be a preference to avoid using medication in general. To see if this latter situation was the case, we also enquired regarding what other medications trekkers were using. One third of the female trekkers were taking oral contraceptives (OCPs), and 56 trekkers were taking other medications, both prescription and over the counter, for a variety of reasons. This suggests that trekkers were not averse to the idea of taking medication, even if alternative management options (such as in the case of contraception) existed.
Our findings upon studying trekker behavior could represent a gap in knowledge regarding AMS, its prevention and management. This is consistent with studies involving more direct inquiries of “knowledge,” including the letter by Subedi et al. Our findings also provide information about the use of acetazolamide among trekkers for AMS prevention, something that Subedi et al found lacking in the literature. 1
We agree with the authors that there is a “wealth of information” available regarding AMS and acetazolamide, but is all this information good? Trekkers may access this information via the Internet, guidebooks, or their physicians when planning travel to high altitude areas. Neither randomly accessed Web sites nor all guidebooks carry consistently reliable and verifiable information. Physicians are often consulted before travel in order to provide prescriptions and immunizations required when visiting many of the countries where trekking occurs. Thus they may compose the ideal group to focus on for knowledge assessment, education, and dissemination of information. There is an ever-increasing population involved in adventure travel 5 and, in turn, an increasing population at risk for AMS. Though we did not attempt to directly measure trekkers' understanding of AMS, our findings suggest that there may be a knowledge deficit in this group on the topic. Given that when such illness does occur, it is frequently in a remote setting, the importance of determining and implementing steps to improve trekkers' knowledge and preparation should not be underestimated.
Footnotes
Acknowledgments
We would like to acknowledge the contributions of Lorraine Woolford, MA, MD, FRCSC, MSc, and Alexandra Bell, BSc, in the analysis of the data and editing of the manuscript. We would also like to acknowledge the support of the Himalayan Rescue Association who, by running nonprofit high altitude clinics in Nepal, have dramatically improved the health and safety of those traveling through the highest mountains in the world.