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 β 1 -blocker bisoprolol and of the α 1 /β-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 (tcpO 2 ) 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 tcpO 2 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 β-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.