Bupivacaine in Paracervical Block—plasma Levels and Changes in Maternal and Foetal Acid-Base Balance

SUMMARY Bupivacaine without adrenaline (20 ml of 0.5 per cent solution) was used for paracervical block in 11 normal parturients in whom there were no signs of foetal asphyxia. Maternal and foetal plasma concentrations of bupivacaine were determined by gas chromatography from serial venous samples. The intrauterine acid-base balance of the child was observed before and after block from blood samples taken by Saling's technique. The maternal plasma concentrations remained below 0.7 μg/ml (median). At the time of birth the bupivacaine concentration in maternal plasma was in all cases higher than that in umbilical vein blood. After block there were no appreciable changes in the foetal acid-base balance.