Abstract
Strips from human umbilical arteries and veins were prepared by micro-dissection. The vessel strips were mounted in tissue baths for isometric recording of contractile activity. The local anesthetic drug bupivacaine induced a concentration-dependent increase of tone in both artery and vein, whereas morphine had no effect. Nor did morphine influence the increase in vessel tone induced by bupivacaine. If applicable in vivo, the results suggest that morphine has little influence on umbilical vessel tone, whereas bupivacaine may reduce the umbilical blood flow, at least when the local concentration of bupivacaine exceeds a certain critical level. The addition of morphine to local anesthetics did not increase any adverse effects on the umbilical vessels in this study.