A comparative evaluation of magnesium sulphate and nitroglycerine as potential adjuncts to lidocaine in intravenous regional anaesthesia

INTRODUCTION: This randomized control trial was carried out to evaluate and compare the efficacy of magnesium sulphate and nitroglycerine (NTG) as adjuncts to lidocaine in intravenous regional anesthesia (IVRA). MATERIALS AND METHODS: Seventy-five, ASA grade I and II patients, aged between 20–50 years, scheduled for hand and forearm surgery were selected and entered randomly into three study groups. Patients in group C received 3 mg/kg of preservative free lidocaine 2% diluted with saline to a total volume of 40 ml. Patients in group M received 3 mg/kg of preservative free lidocaine 2% mixed with 6 ml of 25% magnesium sulphate (1.5 g) diluted with saline to a total volume of 40 ml. Patients in group N received 3 mg/kg of preservative free lidocaine 2% mixed with 200 μg of nitroglycerine diluted with saline to a total volume of 40 ml. Sensory and motor block onset and recovery time, tourniquet pain onset time, intraoperative fentanyl requirement, the total number of patients requiring rescue analgesia and the time to first analgesia requirement, intra-operative and postoperative degree of analgesia were evaluated. RESULTS: The sensory and motor block onset times were shorter in group M and N as compared to group C (P- = 0.004, 0.0036 for sensory block, 0.021, 0.038 for motor block. The mean time of onset of sensory block was earliest in group M and the mean time of onset of motor block was earliest in group N. Mean time of onset of tourniquet pain in the three groups was similar in groups M and N. The sensory and motor block recovery time were significantly prolonged in M and N group as compared to group C (P < 0.001). Intraoperative fentanyl requirement (P value– = 0.041), the total number of patients requiring rescue analgesia (P value = 0.009) and the time to first analgesia requirement (P value = 0.038) were lower in group M. CONCLUSION: The addition of both magnesium suphate and nitroglycerin (NTG) to lidocaine for intravenous regional anesthesia (IVRA) leads to early onset of sensory block and prolonged postoperative analgesia, with no side effects.