Additional effect of magnesium sulfate and vitamin C in laparoscopic gynecologic surgery for postoperative pain management: a double-blind randomized controlled trial

BACKGROUND: This clinical trial was conducted to determine whether combined use of magnesium sulfate and vitamin C more significantly reduced postoperative fentanyl consumption and pain than magnesium sulfate or vitamin C alone. METHODS: The prospective, double-blinded, randomized controlled study enrolled 132 patients scheduled for laparoscopic gynecologic surgery. The patients were randomly allocated to one of the four groups (n = 33 for each group; Group M [magnesium sulfate 40 mg/kg], Group V [vitamin C 50 mg/kg], Group MV [magnesium sulfate 40 mg/kg and vitamin C 50 mg/kg] and Group C [isotonic saline 40 ml]). Cumulative postoperative fentanyl consumption (primary endpoint measure), postoperative pain score by numeric rating scale, and postoperative nausea and vomiting were recorded at 1, 6, 24, and 48 h after discharge from the postanesthesia care unit. RESULTS: Cumulative postoperative fentanyl consumption was significantly less in Groups M, V, and MV than in Group C at all time points. Group MV showed significantly less cumulative postoperative fentanyl consumption than Group M at postoperative 24 h (mean ± standard deviation, 156.6 ± 67.5 vs. 235.6 ± 94.6 µg, P = 0.001), as well as significantly less consumption than Groups M and V at postoperative 48 h (190.8 ± 74.6 vs. 301.0 ± 114.8 or 284.1 ± 128.6 µg, P < 0.001, P = 0.003, respectively). CONCLUSIONS: Combined use of magnesium sulfate and vitamin C provides an additional benefit in postoperative pain management after laparoscopic gynecologic surgery in comparison to single administration of magnesium sulfate or vitamin C.