Augmented bupivacaine spinal anaesthesia in postoperative analgesia

The addition of intrathecal magnesium to local anaesthetics for spinal anaesthesia had been shown to prolong the duration of spinal anaesthesia and reduced postoperative requirement for lower limb orthopaedic procedures and caesarean sections. Aim & Objectives: To determine the effect of intrathecal magnesium sulphate to bupivacaine spinal anaesthesia for transurethral resection of the prostate.

This prospective, randomized, double blind study involved fifty ASA I-II patients who underwent transurethral resection of prostate after informed consent was obtained. Patients were randomized to two groups. Group S received 3ml of 0.5% heavy bupivacaine in addition to 1ml saline while Group M received 100mg of MgSO4 in addition to 3ml of bupivacaine. Onset time of sensory and motor block, time maximal block height was reached, duration of spinal anaesthesia, pain scores and the total analgesics used in the postoperative period were all recorded and analyzed.

Time to maximum sensory block height, regression to T12 segment, and duration of motor block were all longer in group M. The duration before the first request for analgesia was significantly prolonged in the magnesium group (242mins vs 197mins). The magnesium group had lower Numerical Rating Score (NRS) in general, lower NRS scores at request for analgesia and total analgesic consumption in 24 hours.

In patients undergoing transurethral resection of the prostate, the addition of intrathecal magnesium sulphate to bupivacaine spinal anaesthesia significantly prolonged the duration of spinal anaesthesia and also reduced the postoperative analgesic requirement without additional side effects.