To evaluate the efficacy of intrathecal bupivacaine and fentanyl versus bupivacaine, fentanyl and magnesium sulphate in spinal anaesthesia for transabdominal hysterectomy

Context: Intrathecal magnesium sulphate has been found to prolong the duration of analgesia in various surgical procedures like lower limb surgeries and as adjuncts to general anaesthesia for pain management. 
Aims: To evaluate the efficacy and safety of bupivacaine. fentanyl and magnesium sulphate and to compare both the groups in terms of onset time for maximum sensory and motor blockage and duration of effective analgesia.
Settings and Design: Randomized double blind trial.
Methods and Material: Hundred patients were randomly allocated to receive intrathecally either 2.5 mL (12.5 mg) of hyperbaric 0.5% bupivacaine + 0.5 mL (25 mcg) of fentanyl 0.2 mL of normal saline (group A) or 2.5 mL (12.5 mg) of hyperbaric 0.5% bupivacaine + 0.5 mL (25 mcg) of fentanyl + 0.2 mL (100 mg) of 50% magnesium sulfate (group B). 
Statistical analysis used: SPSS version 16.
Results: The mean onset of sensory and motor block was delayed in group B while duration of motor block was comparable in both groups. Duration of effective analgesia increased in group B however number of rescue analgesics required in both the groups remained statistically insignificant. Side effect profile was similar in both the groups except that shivering incidence decreased in group B.
Conclusion: Addition of 100mg magnesium sulfate intrathecally leads to increased duration of effective analgesia with delayed onset of sensory and motor blockade. It also reduces the incidence of shivering.