Randomized study of postcesarean analgesia with intrathecal morphine alone or combined with clonidine.

STUDY OBJECTIVE: To investigate the efficacy of the combination of intrathecal morphine with clonidine in comparison with 2 doses of intrathecal morphine alone for postcesarean analgesia.

DESIGN: Prospective, double-blinded, randomized clinical trial.

SETTING: Maternity ward of Hospital Santa Cruz, Curitiba, Paraná, Brazil (operating room and ward).

PATIENTS: The study included 195 American Society of Anesthesiologist I to III singleton parturients undergoing elective cesarean section.

INTERVENTIONS: The patients were randomized into 3 groups (M50, M100, and M/C). Patients were anesthetized intrathecally with 12 mg of 0.5% hyperbaric bupivacaine and 50 μg or 100 μg morphine (groups M50 and M100, respectively) or 50 μg morphine and 75 μg clonidine (group M/C).

MEASUREMENTS: The patients were subsequently assessed for pain levels and side effects at 9 to 11 hours and 22 to 24 hours after the injection.

MAIN RESULTS: There was no difference in the quality of pain relief among the groups. In all 3 groups, pain was more intense during the first assessment. Pruritus and nausea were more frequent in group M100, and dizziness was more frequent in group M/C; however, these results were statistically insignificant. The group receiving clonidine showed a significantly lower incidence of shivering compared with the other groups.

CONCLUSIONS: At these doses, there was no benefit of associating clonidine with morphine to improve postcesarean analgesia. Considering that higher doses of morphine were associated with more side effects, 50 μg of intrathecal morphine alone seems to be a better option for analgesia. The use of clonidine to reduce postoperative shivering must be balanced against the potential risks of hypotension, bradycardia, dizziness, and sedation.