Background: Local anesthetics are extremely useful drugs for anaesthesiologists. All modern local anesthetics are amides. Esters are unstable in its solution. Lignocaine, Prilocaine, Bupivacaine etc all shares a common basic structure termed aminoacylamide. The current study aims to evaluate the effects of intrathecal supplementation of magnesium sulphate to bupivacaine-fentanyl in patients undergoing lower abdominal surgeries. Methodology: The patients were randomly assigned into two groups of 40 patients each, to receive an intrathecal injection in sitting position of either 15mg of 0.5% hyperbaric bupivacaine + 20mcg i.e 0.4ml of fentanyl + 0.1mg (0.1ml) 50% of magnesium sulphate or 15mg of 0.5% hyperbaric bupivacaine + 20mcg i.e. 0.4ml of fentanyl + 0.1ml normal saline. Duration of motor blockade, time taken for two segments regression are noted. Results: Duration of motor blockade was higher in Group A compared to Group B (279.25+53.33 vs. 249.75+45.11, p<0.001). Regression of sensory block to S₁ was significantly earlier in Group B compared to Group A (240.13±58.99 vs. 271.25±56.78, p<0.001). Conclusion: Longer time for two segment regression, longer duration of motor blockade,decrease incidence of adverse effects.

Keywords: Hyperbaric bupivacaine; Magnesium sulphate; Fentanyl; Lower abdominal surgeries; Spinal anaesthesia.