RESUMEN
Abstract Background Opioids are the cornerstone in managing postoperative pain; however, they have many side effects. Ketamine and Magnesium (Mg) are NMDA receptor antagonists used as adjuvant analgesics to decrease postoperative opioid consumption. Objective We assumed that adding Mg to ketamine infusion can improve the intraoperative and postoperative analgesic efficacy of ketamine infusion alone in cancer breast surgeries. Methods Ninety patients aged between 18 and 65 years and undergoing elective cancer breast surgery were included in this prospective randomized, double-blind study. Group K received ketamine 0.5 mg.kg-1 bolus then 0.12 mg.kg-1.h-1 infusion for the first 24 hours postoperatively. Group KM: received ketamine 0.5 mg.kg-1 and Mg sulfate 50 mg.kg-1, then ketamine 0.12 mg.kg-1.h-1 and Mg sulfate 8 mg.kg-1.h-1 infusions for the first 24 hours postoperative. The primary outcome was the morphine consumption in the first 24 hours postoperative, while the secondary outcomes were: intraoperative fentanyl consumption, NRS, side effects, and chronic postoperative pain. Results Group KM had less postoperative opioid consumption (14.12 ± 5.11 mg) than Group K (19.43 ± 6.8 mg). Also, Group KM had less intraoperative fentanyl consumption. Both groups were similar in postoperative NRS scores, the incidence of side effects related to opioids, and chronic neuropathic pain. Conclusion Adding Mg to ketamine infusion can safely improve intraoperative and postoperative analgesia with opioid-sparing effect in cancer breast surgery.