Spinal anaesthesia for caesarean section: 0.125% plain bupivacaine 12 ml compared with 0.5% plain bupivacaine 3 ml

Forty women had elective Caesarean section under spinal anaesthesia with either 0.5% bupivacaine 3 ml or 0.125% bupivacaine 12 ml, injected at a rate of 1 ml/5 s. For 30 min after the spinal injection, each patient lay on her right side. Compared with the patients given 3 ml, in those given bupivacaine 12 ml there was a significantly greater spread of block (P less than 0.02 for analgesia; P less than 0.002 for touch) and significantly less variation in levels of block (P less than 0.02 for analgesia; P less than 0.04 for touch). However, within 5 min of placing the women in a supine, tilted (right hip up) position, there were no clinically or statistically significant differences in the levels of block between the two groups.