Application of magnesium sulphate as a " multimodal general anesthesia" protocol in patients undergoing hysteroscopy: a randomized controlled study

Abstract

Background: The purpose of the study was to applicate magnesium sulphate as a " multimodal general anesthesia" protocol to reduce perioperative opioids requirements in patients undergoing hysteroscopy.Methods: 70 patients scheduled for hysteroscopy were randomly divided into 2 groups. Patients in Group M received intravenous magnesium sulfate 50 mg/kg in 100 ml of isotonic saline over 15 min before fentanyl injection and then 15 mg/kg per hour by continuous intravenous infusion. Patients in the control group received an equal volume of normal saline as placebo. All patients were anesthetized under a BIS guided monitored anesthesia care with propofol and fentanyl. Intraoperative hemodynamic variables were recorded and postoperative pain scores were assessed with verbal numerical rating scale (VNRS) 1 min, 15 min, 30 min, 1 hour, and 4 hours after recovery of consciousness. The primary outcome of our study was total amount of intraoperative and postoperative analgesics administered.Results: Postoperative serum magnesium concentrations in Group C were significantly decreased than preoperative levels (0.86 ± 0.06 to 0.80 ± 0.08 mmol/L, P=0.001) while there was no statistical change in Group M (0.86 ± 0.07 to 0.89 ± 0.07 mmol/L, P=0.129). Bradycardia did not occur in either group and the incidence of hypotension was comparable between the two groups. Total dose of fentanyl given to patients in Group M was less than the one administered to Group C [100 (75-150) vs 145 (75-175) μg, median (range); P < 0.001]. Fewer patients in Group M required additional analgesics postoperatively. In addition, patients receiving magnesium displayed lower VNRS scores at 15 min, 30 min, 1 hour, and 4 hours postoperatively. Conclusions: Intravenous infusion of magnesium sulphate significantly reduces postoperative pain and perioperative opioid requirements without increasing the risk of cardiovascular side effects. Meanwhile, it was beneficial to maintain a stable serum magnesium concentration after the procedure.Trial registration: www.chictr.org.cn ChiCTR1900024596 date of registration: July 18th 2019.