Effects of magnesium sulphate on intraoperative neuromuscular blocking agent requirement: A prospective randomized double blind placebo controlled study

Introduction: Magnesium sulphate has been shown to decrease intraoperative anesthesia, analgesia and muscle relaxant requirements. Aims: To study the effects of intraoperative magnesium sulphate on requirement of neuromuscular blocking agents. Setting and Design: This prospective randomized double blind placebo controlled study was conducted in the department of Anaesthesiology and Critical Care of a tertiary care centre. Materials and Methods: 50 patients of ASA physical status I and II were randomly allocated into two groups, magnesium group (Group M) received magnesium sulphate 50 mg.kg intravenously as a bolus in 100 ml of isotonic saline over 10 minutes before induction of anesthesia and 15 mg.kgh by continuous infusion during the operation and the control group (Group S) received the same amount of isotonic saline over same time. Atracurium was administered 0.6 mg.kg before intubation and 0.1 mg.kg additionally when train-of-four counts were 2 or more intravenously. The consumption of atracurium was compared in both groups. Statistical Analysis: The variables were analysed with independent t-test, Wilcoxon-Mann Whitney Utest and chi-square test. P-value<0.05 was considered significant. Results: The mean consumption of atracurium in group M was 0.35±0.11 mg.kgh and group S was 0.47±0.19 mg.kgh with p-value<0.001 and comparison was statistically significant. The mean additional doses of intravenous fentanyl given in group M were 0.8±0.57 and group S were 1.5±1.29 with a p-value of 0.014 and the comparison was statistically significant. Hemodynamic variables were comparable between two groups. Conclusion: Intravenous magnesium sulphate reduces atracurium requirements in patients undergoing abdominal surgeries under general anesthesia. Introduction Muscle relaxation is an important component in delivering of anesthesia. Non-depolarizing neuromuscular blocking agents are widely used in maintenance of the neuromuscular relaxation. The muscle relaxation is very important when working deep in abdominal compartments and near critical areas. Magnesium sulphate has been proven as a useful adjunct for administration of anesthesia and has been found to reduce intraoperative anesthetic and analgesic requirements. These effects are primarily based on physiological calcium antagonism, that is voltage-dependent regulation of calcium influx into the cell, and noncompetitive antagonism of N-methyl-D-aspartate (NMDA) receptors. Thwaites and colleagues have found magnesium sulphate effective in treatment of tetanic muscle spasm and rigidity. Magnesium sulphate has been suggested as a potential molecule for study in enhancing the effect of non-depolarizing neuromuscular blocking agents. The said effect is due to presynaptic inhibition of neurotransmitter release. This is due to competition of magnesium ion with the calcium ion which inhibits the release of acetylcholine from the presynaptic nerve terminal and enhance the effect of non-depolarizing neuromuscular blocking agents. Our study was a randomized prospective placebo controlled study to evaluate the effect of administration of magnesium sulphate intravenously to find out the change in requirements of atracurium given as a primary muscle relaxant. Materials and Methods This prospective randomized double blind placebo controlled study was conducted on 50 patients of American society of Anesthesiologists physical status I and II, scheduled for elective abdominal surgeries in the age group Article Info Received: 18th April, 2019 Accepted: 19th June, 2019 Published Online: 22nd August, 2019