Blood pressure responses to whole-body cold exposure: effect of carvedilol.

Abstract

The aim of this study was to test the effects of carvedilol on blood pressure (BP) and heart rate (HR) during whole-body cold exposure in hypertensive and normotensive subjects. Ten hypertensive and twelve normotensive subjects were exposed to cold (-15 degrees C, wind 3.5 m/s) three times for 15 min with a 1-week interval between the exposures. The study design was made according to a randomised double-blind, crossover method. Before the cold exposures the subjects ingested carvedilol or placebo once a day (carvedilol 12.5 mg/day for 2 days and then 25 mg/day for 5 days) for 1 week. The systolic (SBP) and diastolic (DBP) blood pressure and HR were measured every 3 min during the test procedures using an indirect ambulatory blood pressure monitor device (ABPM-02, Meditech Co.). In the hypertensive group, the cold exposure increased SBP/DBP from 119/75 mmHg to 143/96 mmHg during carvedilol treatment (P<0.001) and from 132/85 mmHg to 159/106 mmHg during placebo (P<0.001). In the normotensive group the cold exposure increased SBP/DBP from 112/72 mmHg to 142/93 mmHg during carvedilol treatment (P<0.001) and from 121/75 mmHg to 147/98 mmHg during placebo (P<0.001). In the hypertensive group, the levels of SBP, DBP and MAP (mean arterial pressure) were significantly lower with carvedilol than with placebo during the cold exposure although carvedilol did not affect the cold-induced rise of the BP. The BPs were lower also with carvedilol in the normotensive group than the placebo during the cold exposure, but the differences were smaller than in the hypertensive group. Carvedilol decreased the BP more the higher the initial mean SBP/DBP was with placebo during the cold exposure. Carvedilol reduced the BP during the cold exposure, especially in the hypertensive subjects but also in normotensive ones, without effect on the cold-induced rise of the BP.