Strategy to calculate magnesium sulfate dose in obese patients: A randomized blind trial

BACKGROUNDMagnesium sulfate has analgesic properties in the postoperative period. Among obese patients, there is a gap in the knowledge of its pharmacology related to the use of real, ideal, or corrected ideal body weight in calculating its dose. This trial compared postoperative analgesia using actual and corrected ideal body weight.METHODSSeventy-five obese patients scheduled to undergo laparoscopic cholecystectomy under general anesthesia were randomly assigned to three groups. Patients in the control group received no magnesium sulfate; patients in the other two groups received magnesium sulfate 40 mg·kg − 1 of actual body weight or corrected ideal body weight. A ten nonobese patients group helped us as a model of the expected blood magnesium concentration after magnesium sulfate administration in general population.RESULTSPatients from the groups receiving magnesium sulfate showed significant reduction in morphine consumption ( p  ≤ 0.001) and pain scores ( p  = 0.006) in the postoperative period compared to the control group. There was no significant difference in the consumption of morphine ( p  = 0.323) or pain scores ( p  = 0.082) between these groups. There was no difference in the total duration of neuromuscular block induced by cisatracurium among the three groups ( p  = 0.181) or in the blood magnesium concentrations throughout the study.CONCLUSIONSMagnesium sulfate decreased postoperative pain and morphine consumption without affecting cisatracurium recovery time in obese patients undergoing laparoscopic cholecystectomy. Analgesic profile was similar in groups receiving magnesium sulfate calculated through real or corrected ideal body weight.TRIAL REGISTRATIONclinicaltrials.gov NCT04003688. (Date of registration: June 24, 2019)