[Maternal and neonatal bupivacaine plasma levels in peridural anesthesia for relief of labor pain].

Peripheral venous blood samples were drawn for bupivacaine analyses (gas chromatography) from 24 patients under epidural anaesthesia, used to reduce pain caused by contractions. The specimens were taken 10, 20, 30 and up to 45 minutes following a first injection of 11 to 13 ml bupivacaine 0.25%, before, 15 as well as 30 minutes after each repetitive dose and at childbirth. Immediately after cord clamping, blood sampling in the neonate was performed to evaluate bupivacaine concentrations in the umbilical artery and vein. Additionally, apgar scores and blood gas parameters were checked and compared with those of neonates, born without analgesic treatment of their mothers. Using bupivacaine 0.25% (average 12 ml) for epidural anaesthesia, the peak plasma levels (mean = 0.2 micrograms/ml) were found 10 minutes after application of the analgesic dose. In one patient a maximum bupivacaine plasma concentration (0.47 micrograms/ml) was determined 15 minutes after the second repetitive dose of 5 ml bupivacaine 0.25%. Apgar scores and results of blood gas analyses demonstrated no significant difference between neonates born spontaneously under regional anaesthesia or without any analgesic treatment of their mothers, respectively. Using bupivacaine 0.25% in epidural anaesthesia for pain relief in labour, we found maternal and neonatal plasma concentrations of the local anaesthetic drug far below the accepted threshold level which might produce systemic toxic reactions.