Effects of magnesium on the dose of rocuronium for deep neuromuscular blockade A randomised controlled trial

BACKGROUND Magnesium is known to enhance the effect of rocuronium, but the extent is not quantified. OBJECTIVES We aimed to quantify the effect of magnesium on the dose of rocuronium for deep neuromuscular blockade. DESIGN A randomised controlled study. SETTING A single tertiary care hospital. PATIENTS Seventy males scheduled to undergo robot-assisted laparoscopic prostatectomy, aged between 20 and 80 years with American Society of Anesthesiologists physical status classification 1 or 2, were enrolled. INTERVENTIONS Patients were randomised to either the magnesium group or control group. The magnesium group were infused with 50 mg kg(-1) of magnesium, followed by a continuous intra-operative infusion at 15 mg kg(-1) h(-1) while the control group were infused with the same volumes of 0.9% saline. Deep neuromuscular blockade was maintained with a continuous infusion of rocuronium and was reversed using sugammadex. MAIN OUTCOME MEASURES The primary outcome was the dose of rocuronium administered to maintain deep neuromuscular blockade. The secondary outcomes were recovery time, defined as the time from the administration of sugammadex to train-of-four ratio 0.9, and the incidence of postoperative nausea and vomiting. RESULTS The dose of rocuronium administered to maintain deep neuromuscular blockade was significantly lower in the magnesium group (7.5 vs. 9.4 mu g kg(-1) min(-1), P = 0.01). There was no difference in recovery time or the incidence of nausea and vomiting. CONCLUSION Magnesium reduced the dose of rocuronium required for deep neuromuscular blockade by approximately 20% without affecting the recovery time after administration of sugammadex.