ABSTRACT
BACKGROUND: An adequate uteroplacental and fetal blood flow during labor and cesarean delivery is of prime importance for fetal well-being and neonatal outcome. METHODS: Using the vascular smooth muscle of the human isolated umbilical arteries, this study was performed to see whether commonly used local anesthetics (bupivacaine, lidocaine and 2-chloroprocaine) and opioids (morphine,fentanyl and meperidine) could induce contracion or relaxation of these resting and precontracted vessels. Rings from human umbilical arteries were prepared by microdissection. The vessel rings were mounted in tissue baths for an isometric recording of the contractile activity. For resting muscles, the reactivity to drugs is expressed as a percentage of a maximal KCl-induced contraction, and for precontracted muscle, it is expressed as a percentage of a submaximal KCl-induced contraction. RESULTS: Bupivacaine, lidocaine and 2-chloroprocaine all induced contractions. Bupivacaine showed a maximal contraction (46.7 +/- 10.5%) at concentrations of 43 micrometer, lidocaine 19.7 +/- 4.8% at 0.11 mM. and 2-chloroprocaine showed 14.6 +/- 2.9% at 0.65 mM. Morphine, fentanyl and meperidine all induced contractions. Morphine showed a maximal contraction (19.6 +/- 7.1%) at a concentration of 10 4 M, meperidine at 17.2 +/- 8.4% at 3 x 10 5 M, and fentanyl at 1.7 +/- 2.0% at 3 x 10(-6)M. When umbilical arteries were induced to contract with a submaximal concentration of KCl, bupivacaine and lidocaine showed an ability to increase the magnitude of the sustained contraction, but 2-chloroprocaine showed a relaxation of the sustained contraction. Morphine, fentanyl and meperidine showed no change in the sustained contraction. CONCLUSIONS: This study demonstrates these local anesthetics and opioids as vasoactive on human umbilical arteries. If applicable in vivo, these drugs might have some influence on umbilical vessel tone and thus might reduce umbilical blood flow.