Blood Pressure and Altitude: An Observational Cohort Study of Hypertensive and Nonhypertensive Himalayan Trekkers in Nepal.

Keyes, Linda E., Thomas Douglas Sallade, Charles Duke, Jennifer Starling, Alison Sheets, Sushil Pant, David S. Young, David Twillman, Nirajan Regmi, Benoit Phelan, Purshotam Paudel, Matthew McElwee, Luke Mather, Devlin Cole, Theodore McConnell, and Buddha Basnyat. Blood pressure and altitude: an observational cohort study of hypertensive and nonhypertensive Himalayan trekkers in Nepal. High Alt Med Biol. 18:267-277, 2017. OBJECTIVES: To determine how blood pressure (BP) changes with altitude in normotensive versus hypertensive trekkers. Secondary aims were to evaluate the prevalence of severe hypertension (BP ≥180/100 mmHg) and efficacy of different antihypertensive agents at high altitude. METHODS: This was an observational cohort study of resting and 24-hour ambulatory BP in normotensive and hypertensive trekkers at 2860, 3400, and 4300 m in Nepal. RESULTS: We enrolled 672 trekkers age 18 years and older, 60 with a prior diagnosis of hypertension. Mean systolic and diastolic BP did not change between altitudes in normotensive or hypertensive trekkers, but was higher in those with hypertension. However, there was large interindividual variability. At 3400 m, the majority (60%, n = 284) of normotensive participants had a BP within 10 mmHg of their BP at 2860 m, while 21% (n = 102) increased and 19% (n = 91) decreased. The pattern was similar between 3400 and 4300 m (64% [n = 202] no change, 21% [n = 65] increased, 15% [n = 46] decreased). BP decreased in a greater proportion of hypertensive trekkers versus normotensives (36% [n = 15] vs. 21% at 3400 m, p = 0.01 and 30% [n = 7] vs. 15% at 4300 m, p = 0.05). Severe hypertension occurred in both groups, but was asymptomatic. In a small subset of participants, 24-hour ambulatory BP monitoring showed that nocturnal BP decreased in normotensive (n = 4) and increased in hypertensive trekkers (n = 4). CONCLUSIONS: Most travelers, including those with well-controlled hypertension, can be reassured that their BP will remain relatively stable at high altitude. Although extremely elevated BP may be observed at high altitude in normotensive and hypertensive people, it is unlikely to be symptomatic. The ideal antihypertensive regimen at high altitude remains unclear.