In Response to “Health Screening on Aconcagua”

Abstract

To the Editor: We read with great interest the recent letter to the editor by Windsor et al “Health Screening on Aconcagua.”1.Windsor J.S. Currie R.J. Grocott M. Chioconi R. Hillebrandt D. Health screening on Aconcagua.Wild Envir Med. 2009; 20: 90-104Abstract Full Text Full Text PDF PubMed Google Scholar We spent 3 weeks in January 2009 on Aconcagua at Plaza de Mulas base camp (4365 m) prospectively enrolling subjects in an investigation of acute mountain sickness (AMS). We directly observed the health screening process referred to in Windsor's letter. If a climber had systolic blood pressure (SBP) ≥160 mm Hg, the person was advised to return for a recheck 12 hours later. If the second measurement remained ≥160 mm Hg, the climber was started on a low-dose calcium channel blocker. This practice is evidently based on the British Hypertension Society IV guidelines for the management of hypertension in the general community, which state that antihypertensive therapy is indicated as treatment for sustained SPB ≥160 mm Hg or diastolic blood pressure ≥100 mm Hg.2.Williams B. Poulter N.R. Brown M.J. British Hypertension Society guidelines for hypertension management 2004 (BHS-IV): summary.BMJ. 2004; 328: 634-640Crossref PubMed Scopus (733) Google Scholar Windsor et al brought up 2 concerns with this approach, namely, initiation of treatment based on only 1 or 2 elevated readings and the lack of literature supporting hypertension as a predictor of altitude sickness. We too were unable to identify any studies describing a clear association between hypertension and altitude sickness. Furthermore, British Hypertension Society IV guidelines are geared towards screening for and management of hypertension in the outpatient primary care population. Extrapolation of these guidelines to elevated readings at an altitude of 4365 m may be problematic. In our study, we enrolled 127 subjects at 4365 m while they were acclimating at base camp. Subjects prospectively filled out a questionnaire with demographics, medical history, experience at altitude, and characteristics of their current expedition. We then recorded 1 set of vital signs on the subjects while at base camp and collected outcome data after their summit attempt. We currently have outcome data on 65 subjects. Our primary outcome is the presence of AMS, as measured by the Lake Louise Scoring System AMS self-report questionnaire. Given the high incidence of AMS on Aconcagua, we report those subjects who experienced a severe degree of AMS, as defined by a Lake Louise Questionnaire score of ≥5.3.Basnyat B. Gertsch J.H. Johnson E.W. Castro-Marin F. Inoue Y. Yeh C. Efficacy of low-dose acetazolamide (125 mg BID) for the prophylaxis of acute mountain sickness: a prospective, double-blind, randomized, placebo-controlled trial.High Alt Med Biol. 2003; 4: 45-52Crossref PubMed Scopus (126) Google Scholar,4.Pesce C. Leal C. Pinto H. Determinants of acute mountain sickness and success on Mount Aconcagua (6962 m).High Alt Med Biol. 2005; 6: 158-166Crossref PubMed Scopus (48) Google Scholar Twelve of 65 subjects (19%) had a SBP ≥160 mm Hg on our 1 isolated reading, of whom 6 (50%) had a severe degree of AMS. Meanwhile, of the 53 patients with SBP <160 mm Hg, 27 (49%) had a severe degree of AMS. The difference between the prevalence of AMS in the nonhypertensive group compared with the hypertensive group was 1% (95% CI of the difference −33% to 31%). We recalculated the same analysis using a lower threshold for AMS (Lake Louise Questionnaire score ≥3), and again there was no statistical significance (data not shown). In summary, among 65 climbers in whom both a prospective measurement of blood pressure and Lake Louise Scoring System scores were recorded, we found no correlation between hypertension and development of AMS. Admittedly, our study was not designed or powered to test the relationship between AMS and hypertension. Given the large number of climbers who visit Aconcagua, the high incidence of AMS, and the expense and danger involved with medical evacuation by helicopter, an effective medical screening program on Aconcagua is becomingly essential. Evidence-based medical screenings by trained medical personnel at base camp will help to properly identify and counsel climbers at higher risk of developing AMS. However, our preliminary data and the evidence presented by Windsor et al do not suggest that a single elevated blood pressure measurement is predictive of AMS. Adequately powered prospective studies that investigate the relationship between hypertension at altitude and development of AMS are needed.