THE MATERNAL PLASMA LEVELS AND PLACENTAL TRANSFER OF BUPIVACAINE FOLLOWING EPIDURAL ANALGESIA

The maternal plasma levels of bupivacaine following epiduraladministration of 0.5 per cent solution with 1/200,000 adrenalinewere determined in twelve patients in labour. After 10 ml (50mg) peak concentrations occurred 15–30 min later and rangedfrom 0.22 µg/ml to 0.60 µg/ml. Plasma levels fellgradually with time after the peak until by 3 hours after injectionthey were all well below 0.2 µg/ml. Maternal and umbilicalplasma levels of bupivacaine were determined at delivery. Theratio of the foetal to maternal levels varied from 0.14 to 0.86.The highest foetal plasma level obtained in the series was 0.25µg/ml and the highest maternal level was 0.68 µg/ml.This value was reached after three 10-ml injections of 0.5 percent bupivacaine with 1/200,000 adrenaline. The 1-min Apgarscores ranged from 7 to 10.