Background
Severe and uncontrolled hypertension have been reported in high altitude sojourners but have not been studied systematically. Additionally, few studies have evaluated the efficacy of antihypertensive medications at high altitude. We documented the prevalence of severe hypertension and efficacy of antihypertensive medications in high-altitude trekkers in Nepal.
Methods
Observational cohort study in Nepal's Solukhumbu Valley. We recruited trekkers 18 years of age and older. Subjects reported demographics, medical history, and medications. Resting blood pressure (BP) was recorded at 2860 m, 3400 m, and 4300 m on ascent and descent. Severe hypertension was defined as systolic BP ≥180 and/or diastolic BP ≥100.
Results
We enrolled 60 self-reported hypertensive (HTN) trekkers and 606 normotensive (NTN) trekkers. Out of 2158 BP measurements at all altitudes, 109 (5%) were severe. Of these, 39 occurred in 22 (37%) HTN trekkers and 70 were distributed among 51 (8%) NTN trekkers. Occurrence of severe hypertension was similar across altitudes (P < .05). No subject was symptomatic. Among HTN trekkers, 10 took no antihypertensives and 5 of those had one or more severe BP measurements, accounting for 21% of all severe BPs in HTN trekkers. Seven out of 14 subjects on angiotensin converting enzyme inhibitors (ACEI) accounted for another one-third of all severe BPs. No subject taking a beta-blocker (BB), thiazide, ACEI + calcium channel blocker (CCB), ACEI + BB, or angiotensin receptor blocker (ARB) + alpha-1 antagonist had severe hypertension. Severe hypertension occurred in a smaller proportion of trekkers on combinations of CCB plus either ACEIs (0/3) or ARBs (1/3), and those taking more than 3 antihypertensives (1/3).
Conclusions
Asymptomatic severe hypertension occurred at high altitude in normotensive and hypertensive subjects, but was more common in those with underlying hypertension. The clinical importance of these episodes is unclear. Our preliminary results suggest some antihypertensives may be more effective at high altitude than others.
Funding
WMS Hultgren Grant (2014); Nepal International Clinic