Addition of Intrathecal Magnesium Sulfate to Bupivacaine for Spinal Anesthesia in Cesarean Section

BACKGROUND: Spinal anesthesia is widely used for caesarean section. Addition of intrathecal magnesium sulfate to local anesthetics seems to improve the quality of block and prolong the duration of analgesia. OBJECTIVES: The present study was designed to examine whether addition of intrathecal magnesium sulfate enhances the analgesic efficacy of intrathecal bupivacaine in patients undergoing cesarean section. PATIENTS AND METHODS: We conducted a randomized, prospective, double-blind, case-control, clinical trial. Eighty patients were scheduled for cesarean section under spinal anesthesia. The patients were randomly allocated to receive either 10 mg of hyperbaric bupivacaine 0.5% (control group) or 10 mg of hyperbaric bupivacaine 0.5% plus 50 mg magnesium sulfate (case group) intrathecally. Hemodynamic variability, onset and duration of block and duration of analgesia were evaluated. RESULTS: The onset of sensory blockade was delayed in case group compared with control group, and this was statistically significant. The onset of motor blockade had no difference in both groups. The duration of motor blockade was similar. Post-operative analgesia was longer in magnesium sulfate group but the difference was not meaningful. The intraoperative hemodynamic variability showed no significant differences between groups. CONCLUSIONS: This study showed that the addition of intrathecal magnesium sulfate to bupivacaine is not desirable in patients undergoing cesarean section due to the delay in the onset of sensory blockade and the lack of significant effects of magnesium on post-operative pain.