Spread of subarachnoid block, intraoperative local anaesthetic requirements and postoperative analgesic requirements in Caesarean section and total abdominal hysterectomy.

BACKGROUND: Pregnancy is associated with a higher spread of subarachnoid anaesthesia and increased pain threshold. The study was designed to assess the spread of subarachnoid block and the intra- and postoperative analgesic requirements in pregnant vs non-pregnant women.

METHODS: We assessed the level of subarachnoid anaesthesia after 1.8 ml of hyperbaric lidocaine 5% and the postoperative analgesic requirements in women undergoing Caesarean section and undergoing abdominal hysterectomy (30 each group). Intraoperatively epidural ropivacaine was given as required. All patients received 10 ml of ropivacaine 0.2% epidurally 2, 10, and 24 h after operation and the VAS pain score was assessed. They also had access to patient controlled analgesia i.v. morphine.

RESULTS: Duration of surgery was 64 (13.7) vs 127 (33.8) min (P<0.0001) in the pregnant and non-pregnant groups. Ten minutes after subarachnoid injection, sensory block was higher by three dermatomes in the pregnant group (P<0.0001). Time to first ropivacaine dose was 37 (19.7) vs 19 (12.2) min (P<0.001) and the ropivacaine normalized for the duration of anaesthesia was 0.8 (0.6) vs 1.3 (0.5) mg(-1) (P=0.001) in the pregnant and non-pregnant groups, respectively. The time between the first and second ropivacaine dose was similar in the two groups (P=0.070). Fewer pregnant women (81 vs 100%) required ropivacaine intraoperatively (P=0.017). The VAS scores were similar but parturients consumed more i.v. morphine (33 (14) vs 24 (12) mg, P=0.016) during the first 24 h after operation.

CONCLUSIONS: Pregnant patients exhibited a higher level of subarachnoid sensory block and required more i.v. morphine after operation.