The Effects of Epidural Ropivacaine and Bupivacaine for Cesarean Section on Uteroplacental and Fetal Circulation

Abstract

Comment Ropivacaine is a new amide local anesthetic. Although similar in structure to bupivacaine, it is prepared solely as the s-isomer compared with the other local anesthetics, which are prepared as racemic mixtures. The advantage of ropivacaine to bupivacaine is its lesser degree of cardiac toxicity. Ropivacaine, as with other local anesthetics, has a biphasic action on the smooth muscles of peripheral blood vessels. In low concentrations there is vasoconstriction, whereas in higher concentrations there is vasodilation. Ropivacaine crosses the placenta. Therefore, it is important to determine the effects of epidural ropivacaine on placental blood flow. The basis for measuring blood volume flow is the Doppler shift principle. Echoes returning from structures moving toward the transducer are higher in frequency than originally transmitted by the transducer.