Postoperative analgesia for cesarean section. Does the addiction of clonidine to subarachnoid morphine improve the quality of the analgesia?

Abstract

BACKGROUND AND OBJECTIVES: The mechanism of action of α2- adrenergic analgesia has been explored for more than one hundred years. The increased duration of the sensitive and motor blockades caused by clonidine is dose-dependent and has antinociceptive properties. The objective of this study was to evaluate whether the addition of 15 to 30 μg of clonidine to spinal anesthesia for cesarean sections with 0.5% hyperbaric bupivacaine (12.5 mg) and morphine (100 μg) improves the quality of postoperative analgesia. METHODS: We realized a prospective, randomized study that included 60 patients divided in 3 groups: BM - 0.5% hyperbaric bupivacaine (12.5 mg) and morphine (100 μg), BM15 - 0.5% hyperbaric bupivacaine (12.5 mg), morphine (100 μg), and clonidine (15 μg), and BM30 - 0.5% hyperbaric bupivacaine (12.5 mg), morphine (100 μg), and clonidine (30 μg), administered separately. In the perioperative period the use of ephedrine and the newborn's Apgar score were recorded. In the postoperative period, the pain was evaluated in the 12 th h by the VAS, the length of time it took the patient to ask for analgesics, and the postoperative side effects, such as pruritus, nausea, vomiting, bradycardia, hypotension, and sedation. The values were considered significant when p < 0.05. RESULTS: The groups were homogenous. The use of ephedrine and the evaluation by the Apgar score did not show statistically significant differences among the different groups. The pain scores and the average time to start analgesia showed differences among the groups BM and BM15/BM30, and there were no differences regarding the incidence of postoperative side effects. CONCLUSIONS: The addition of clonidine to spinal anesthesia with 0.5% hyperbaric bupivacaine (12.5 mg) and morphine (100 μg) for cesarean section improved the quality of the postoperative analgesia without increasing the incidence of side effects. We suggest that the dose of 15 μg of clonidine should be used. © Sociedade Brasileira de Anestesiologia, 2006.