The placental transfer and fetal effects of levobupivacaine, racemic bupivacaine, and ropivacaine

Background: The purposes of this study were to assess the effects of levobu pivacaine on uterine blood flow and fetal well-being and to compare its pla cental transfer with that of bupivacaine and ropivacaine. Methods: after a control period pregnant ewes that were fitted with instrum ents for long-term monitoring were randomized to receive a two-step intrave nous infusion of levobupivacaine, bupivacaine, or ropivacaine, in a blinded manner, for 1 h, Maternal and fetal hemodynamics were monitored during the study. Arterial blood samples were drawn at 30 and GO min of infusion from the mother and fetus to determine the acid-base status (GO min only) and s erum drug concentrations. The fetal brain, heart, liver, lungs, adrenal gla nds, and kidneys were obtained to measure tissue drug levels. Results: Maternal blood pressure, central venous and intraamniotic pressure s, acid-base status and uterine blood flow were unaffected by any drug infu sion. In contrast to the other two local anesthetics, the infusion of bupiv acaine was associated with a small but significant decrease in the ene's he art rate. At the end of the study, the heart rate In the bupivacaine-treate d animals was significantly less than in the animals treated with the other two drugs, All fetuses were in good condition at the start of study, and n one of the local anesthetics affected fetal well-being. No significant diff erences were found among the three drugs in the maternal serum, fetal serum , fetal tissue concentrations, and tissue:serum concentration ratios. Conclusions: Levobupivacaine was similar to bupivacaine and ropivacaine in causing no important hemodynamic changes in the pregnant ewe and fetus. The re were no significant differences in the fetal serum and tissue levels of the drugs.