The effects of 2 beta-receptor blocking agents on the microcirculation of healthy subjects and of hypertensive patients.

The effects on parameters of the capillary system of the beta 1-blocker bisoprolol and of the alpha 1/beta-blocker carvedilol were investigated in 12 healthy female and 12 male non-smokers and smokers and in 20 hypertensive patients (state WHO I-II). Besides the antihypertensive and heart rate-reducing effect, carvedilol but not bisoprolol provoked a short-term increase in the capillary red blood cell velocity by 20% and an increase in the oxygen tension (tcpO2) in healthy smokers by 27% (p < 0.05). In hypertensive patients the single intake of carvedilol enhanced the capillary velocity by 16% after the first dose, the effect decreased by 5.4% after the intake for 4 weeks. The simultaneously observed increase in tcpO2 lasted only 30 min post dose, while bisoprolol was without significant effects. Carvedilol did not change the venous capacity after the first dose but increased it by 35% after intake for 4 weeks, while bisoprolol with its slight peripheral resistance-enhancing effect decreased the venous capacity after intake for 2 and 4 weeks. The venous outflow increased 1.5 and 2 h after carvedilol administration, but this was not seen 2 and 4 weeks later. The deformability of red blood cells was not changed by both beta-blockers. The data in volunteers and hypertensives indicate a weak vasodilating effect of carvedilol in contrast to bisoprolol in the arterial and venous capillary bed. These effects must be confirmed by additional studies.