Role of Magnesium as Analgesic Sparing Adjuvant to Ropivacaine in Thoracic Paravertebral Block for Breast Cancer Surgery: A Prospective, Double-Blinded Randomised Controlled Study

Abstract

Introduction: Thoracic surgeries are often associated with intractable pain leading to postoperative pulmonary complications. To alleviate this pain in intraoperative and postoperative period, Thoracic Paravertebral Block (TPVB) has been proven as an effective mean. Various adjuvants and their mixtures have been tried to prolong the duration of TPVB. Aim: In this randomised controlled study, we have evaluated the analgesic sparing efficacy of magnesium sulfate; a NMDA receptor antagonist, administered along with ropivacaine for TPVB for breast cancer surgery patients. Materials and Methods: Eighty breast cancer surgery patients, undergoing General Anaesthesia (GA), were randomly divided into group RP and group RM (n=40 each) receiving preoperative TPVB at T3-5 level with 0.5% ropivacaine solution admixture with normal saline and magnesium sulphate, respectively. Intraoperative fentanyl and propofol requirement was compared. Visual Analogue Scale (VAS) was used for postoperative pain assessment. Total dose and mean time to administration of first rescue analgesic paracetamol was noted. Side effects and haemodynamic parameters were also noted. Results: Intraoperative fentanyl (153.86 vs. 138.49 μg), propofol requirement (150.34 vs. 134.23 mg) was significantly less in test (magnesium) group. The requirement of paracetamol was also significantly less (1592.09 vs. 1149.23 mg) and later (8.44 vs. 13.34 hour) in group RM than group RP. Haemodynamics and side effects were comparable among two groups. Conclusion: Magnesium provided better intraoperative as well as postoperative analgesia than placebo when administered with ropivacaine in TPVB prior to breast cancer surgery patients. It also renders a lesser analgesic requirement without major haemodynamic alteration and side effects.