Systemic magnesium to improve quality of post-surgical recovery in outpatient segmental mastectomy: A randomized, double-blind, placebo-controlled trial

Background: It remains to be determined if perioperative systemic magnesium can improve postoperative quality of recovery of patients undergoing ambulatory procedures. The main objective of the current investigation was to evaluate the effect of systemic magnesium on postoperative quality of recovery in patients undergoing outpatient segmental mastectomies. Methods: The study was a prospective randomized, double-blind, placebo-controlled, clinical trial. Female subjects were randomized to receive intravenous magnesium (MgSO4 50mg/kg in 100 mL of normal saline over 15 min before anesthesia induction, followed by an infusion of 15 mg/kg/hour) or the same volume of saline. The primary outcome was the Quality of Recovery 40 (QOR-40) questionnaire at 24 hours after surgery. Results: 50 subjects were recruited and 46 completed the study. Patients in the magnesium group had better global Quality of Recovery scores compared with the saline group, with a median difference of 24 (99% CI, 3 to 33), P<0.001. After discharge from hospital, subjects in the magnesium group required less oral opioids, median (IQR) of 10 (0 to 20) (oral milligrams of morphine equivalents) than the saline group, 30 (20 to 40) (P<0.001). The postoperative systemic magnesium concentrations were substantially higher in the magnesium group, 1.25 ± 0.28 mmol/L compared to control, 0.71 ± 0.11 mmol/L, P<0.0001. Simple linear regression demonstrated a direct linear relationship between the postoperative systemic magnesium concentrations and 24 hour postoperative quality of recovery scores (P = 0.004), and also an inverse relationship with pain burden in the postoperative care unit (P = 0.01). Conclusions: Systemic magnesium improves postoperative quality of recovery in patients undergoing outpatient segmental mastectomy. Systemic magnesium is a safe, inexpensive, efficacious strategy to improve quality of recovery after ambulatory surgery.