Effects of maternal position on epidural anesthesia for cesarean section, acid-base status, and bupivacaine concentrations at delivery.

In 25 patients excellent clinical anesthesia for elective cesarean section was obtained with lumbar epidural block using an average dose of bupivacaine of 130 mg (18 ml of 0.75 per cent solution). Supplemental drugs were not needed. All infants had normal Apgar scores at delivery. Ten patients were kept in a 35--40 degree semi-sitting supine position during induction, while 15 patients were similarly semi-sitting but turned into the left lateral position. Maternal position did not affect the adequacy of the anesthesia or the clinical condition of the infants, but did alter acid-base state and bupivacaine concentrations in the infants. At delivery, the infants whose mothers had been supine had significantly lower pH values in umbilical cord blood than those whose mothers had been in the lateral position. Also, high concentrations of bupivacaine were found in the umbilical vein blood of infants whose mothers were supine.