Effects of selective and nonselective beta-blockade on 24-h ambulatory blood pressure under hypobaric hypoxia at altitude

Background: Little is known about the effects of cardiovascular drugs at high altitude. Objective: To assess 24-h blood pressure (BP) and heart rate (HR) during short-term altitude exposure in healthy normotensive persons treated with carvedilol or nebivolol. Methods: Participants were randomized in double-blind to placebo, nebivolol 5 mg once daily or carvedilol 25 mg b.i.d. Tests were performed at sea level (baseline and after 2 weeks treatment) and on second to third day at altitude (Monte Rosa, 4559 m), still on treatment. Data collection included conventional BP, 24-h ambulatory BP monitoring (ABPM), oxygen saturation (SpO2), Lake Louise Score and adverse symptoms score. Results: Twenty-four participants had complete data (36.4 ± 12.8 years, 14 men). Both beta-blockers reduced 24-h BP at sea level. At altitude 24-h BP increased in all groups, mainly due to increased night-time BP. Twenty-four-hour SBP at altitude was lower with carvedilol (116.4 ± 2.1 mmHg) than with placebo (125.8 ± 2.2 mmHg; P <0.05) and intermediate with nebivolol (120.7 ± 2.1 mmHg; NS vs. others). Rate of nondipping increased at altitude and was lower with nebivolol than with placebo (33 vs. 71%; P = 0.065). Side effects score was higher with carvedilol than with placebo (P = 0.04), and intermediate with nebivolol. SpO2 at altitude was higher with placebo (86.1 ± 1.2%) than with nebivolol (81.7 ± 1.1%; P = 0.07) or carvedilol (81.1 ± 1.1%; P = 0.04). Conclusions: Both carvedilol and nebivolol partly counteract the increase in BP at altitude in healthy normotensive individuals but are associated with a lower SpO2. Carvedilol seems more potent in this regard, whereas nebivolol more effectively prevents the shift to a nondipping BP profile and is better tolerated.