The effect of addition of intrathecal clonidine to hyperbaric bupivacaine on postoperative pain and morphine requirements after Caesarean section: a randomized controlled trial.

Background: Intrathecal clonidine prolongs spinal anaesthesia. We investigated the effect of the addition of clonidine (75 microg) to hyperbaric bupivacaine on postoperative morphine consumption after Caesarean section in a randomized controlled double-blind trial.
Methods: A group of 106 women received spinal anaesthesia using either bupivacaine 0.5% (2.2 ml) heavy with 0.5 ml normal saline 0.9% (B) or bupivacaine 0.5% (2.2 ml) heavy with clonidine (75 microg) in 0.5 ml normal saline 0.9% (BC). The primary outcome was the total morphine consumption in the first 24 h after surgery. Secondary outcomes were the duration of postoperative analgesia, postoperative pain scores, the need for alfentanil during surgery, block regression, clonidine side-effects and morphine side-effects.
Results: Total morphine consumption was similar in both study groups. The mean time to the first analgesic request in the BC group was 129 (SD 13.8) min, compared with 55 (14.2) min in the B group [mean difference (95% CI) -75 (-106 to -44) min]. In the BC group 22 (42%) patients had a complete motor block 1 h after surgery compared with 4 (8%) patients in the B group [RR (95% CI) 0.18 (0.07-0.49)]. Side-effects of intrathecal clonidine were not detected.
Conclusions: The addition of clonidine (75 microg) to hyperbaric bupivacaine prolongs spinal anaesthesia after Caesarean section and improves early analgesia, but does not reduce the postoperative morphine consumption during the first 24 h. No clinically relevant maternal or neonatal side-effects were detected.