Abstract

Objective: In this in vitro study, we investigated the vasoactive effects of levobupivacaine and ropivacaine on vascular smooth muscle derived from human umbilical arteries and veins.

Material and Methods: The strips were mounted in tissue baths at 37°C continuously gassed with 5% CO2 in oxygen for isometric recording of contractile activity on a polygraph. The endothelium of some tissues was mechanically removed to assess the influence of the endothelium on contractility. The strips were precontracted with serotonin (10-6 M 5-HT; n=7). After obtaining the maximal contraction, responses obtained by adding levobupivacaine and ropivacaine (10-9-10-4 M; n=7) cumulatively were recorded. Contractions were expressed as the (% of 5HT maximal response) percentage of 5 HT's maximal response.

Results: Both levobupivacaine and ropivacaine induce a concentrationdependent contraction in the smooth muscle cells of umbilical arteries and veins. Maximum contractile response (Emax) of levobupivacaine (79.2±2.5, 71.1±2.6) was higher than ropivacaine (68.4±2, 36.2±2.8) on both umbilical arteries and veins. There were no statistically significant differences between contraction responses of endothelium-intact and endothelium-denuded tissues.

Conclusion: The results suggest that, in high concentrations, levobupivacaine and ropivacaine may affect umbilical blood flow by contracting the umbilical artery and vein, thus reducing fetal blood flow.