Smooth Muscle Effects of Lidocaine, Prilocaine, Bupivacaine and Etidocaine on the Human Umbilical Artery

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Abstract
The smooth muscle effects on human umbilical arteries of 4 different local anesthetic agents (lidocaine, etidocaine, prilocaine and bupivacaine) were studied. Lidocaine and etidocaine relaxed the arteries, etidocaine more profoundly than lidocaine. Prilocaine in the concentration range 10-1000 .mu.g/ml caused pronounced contractions. Bupivacaine consistently evoked a contractile response in the concentration range 5-25 .mu.g/ml, but at lower and higher concentrations, the response to this drug was inconsistent. The concentrations of lidocaine were determined in 6 human umbilical arteries following maternal epidural block with this agent and were 0.1-1.7 .mu.g/g tissue. The contractile actions of prilocaine and bupivacaine on the human umbilical arteries are undersirable and might be hazardous if high concentrations are attained, e.g., during paracervical block.