Anesthesia for cesarean section IV: placental transfer and neonatal elimination of bupivacaine following epidural analgesia for elective cesarean section.

Epidural analgesia with bupivacaine was used for elective cesarean section, and repeated maternal and neonatal blood samples were collected over 24 h for calculation of drug concentration. A gas-chromatogrphic micro-method was used for the analysis. The aim of this investigation was to evaluate the placental transfer and the elimination rate of the drug. No signs of systemic toxicity were observed in any mother or child, despite relatively high blood concentrations. The fetal-maternal ratio of concentrations at delivery was higher than in previous studies, most probably due to the protein-binding characteristics of bupivacaine and the dosage used. The biological half-life of the rapid phase of elimination (alpha-phase) in the newborn was shorter than in the mother (P less than 0.002), indicating a more rapid distribution process. The half-life of the slow phase of elimination (beta-phase) in the newborn was of the same magnitude as in the mother, indicating that neonatal elimination processes of bupivacaine may be well developed at birth.