A study to observe the effects of addition of magnesium sulphate as an adjuvant to 0.5% bupivacaine for intrathecal anesthesia in surgeries of lower limbs

Intrathecal anesthesia is used commonly for surgical procedures and local anesthetics are associated with relatively short duration of action. A number of adjuvants have been used to prolong the postoperative analgesia.

This study is to investigate the effects of intrathecal Magnesium sulfate 100 mg, added to hyperbaric Bupivacaine 0.5% on the Spread, duration, regression of spinal block, and duration of postoperative analgesia in patients undergoing lower limb surgeries.

Sixty selected patients were randomized to Group B (n=30) patients who received 0.5% heavy Bupivacaine 3ml (15 mg) + Normal saline 0.2 ml and Group M (n=30) patients who received 0.5% heavy Bupivacaine 3ml(15mg)+50%MgSO₄ 0.2 ml(100mg) intrathecally for lower limb surgeries. Block characteristics, hemodynamic changes and adverse effects were compared.

Efficacy of both the drugs when given intrathecally was studied. Mean time needed for sensory blockade at T10 was 3.3±0.7 min in group B and 4.33±0.9 min in group M and p value (<0.001). The mean of total duration of the sensory block in group B was 171.5±18.76 min while it was 218.5±22.52 min in group M (p value <0.001). Time taken for onset of motor block was 4.96±1.2 min in group B and 7.66±1.26 min in group M (p value <0.001). The mean of total duration of motor block in group B was152.5±11.87 mins while it was190.66±21.2 min in group M (p value <0.001). The total duration of effective analgesia in group B was 168.5±16.56 min and in group M was 225.76±24.81 min (p value <0.001). There was no clinical significance in occurrence of side effects in both the groups.

Magnesium sulphate at a dose of 100mg added to 3ml of bupivacaine provided better and extended duration of sensory, motor blockade and total duration of effective analgesia for patients under intrathecal anaesthesia for lower limb surgeries with no sedation.