Anesthesiology
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Ropivacaine is believed to have a lower incidence of clinical cardiac side effects than bupivacaine. The aim of this study was to compare the direct cardiac effects of the optically pure S(-)-ropivacaine isomer and its nonclinically used R(+)-isomer with both optically pure bupivacaine isomers in isolated hearts. The hypothesis was that differences in direct cardiac effects are distinguished not only by stereoselective actions of local anesthetic molecules to specific receptors, but also by physicochemical differences triggered by replacing the butyl- by a propyl-residual on pipecoloxylide. ⋯ The results confirm that stereoselectivity can be demonstrated by a lengthening of atrioventricular conduction time for the more fat-soluble bupivacaine. However, for the less fat-soluble ropivacaine, the S(-)-isomer has no advantage over the R(+)-isomer for preventing slowing of atrioventricular conduction in clinical concentrations. Neither anesthetic showed stereoselective inotropic effects, but ropicavaine isomers had lesser cardiodepressant effects than bupivacaine isomers because of the replacement of the butyl- by a propyl-terminal group.