Figure 710

^-adrenergic antagonists. ^-adrenergic antagonists attenuate sympathetic activity through competitive antagonism of catecholamines at both P1- and ^-adrenergic receptors [6,9]. In the absence of partial agonist activity (PAA), the acute systemic hemodynamic effects are a decrease in heart rate and cardiac output and an increase in peripheral vascular resistance proportional to the degree of cardio-depression; blood pressure is unchanged. Chronically, there is a gradual decrease in blood pressure proportional to the fall in peripheral vascular resistance, which is dependent on the degree of cardiac sympathetic drive. ^-adrenergic antagonists with sufficient partial agonist activity to maintain heart rate and cardiac output may not evoke acute reflex vasoconstriction: Blood pressure falls proportional to the decrease in peripheral resistance (see Fig. 7-11) [10]. BP—blood pressure; CO—cardiac output; E—epinephrine; NE— norepinephrine; TPR—total peripheral resistance.

0 0

Post a comment