Anesthesiology
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It is well known that the concentration of bupivacaine in umbilical cord blood at birth is low compared with the concentration in maternal blood. It is not clear whether this low fetal/maternal ratio (F/M) is due to decreased placental transfer or increased uptake by fetal tissues. The purposes of this study were to develop an appropriate analytic method and to clarify this issue by studying the disposition of bupivacaine in mother, fetus and neonate following epidural anesthesia. ⋯ Finally, urinary excretion of PPX by the neonate remains relatively constant during the first 48 h of life. In contrast, the mother excretes the highest amount of PPX between 12-24 h postpartum. The persistence of bupivacaine and PPX in neonatal body fluids suggests that the low F/M ratio of bupavacaine at birth is due to considerable uptake of bupivacaine by fetal tissues and is not due to diminished placental transfer.