Ropivacaine-Dexamethasone vs. Ropivacaine-Magnesium Sulfate in TAP Block: A Randomized Study of Postoperative Analgesia in Lower Abdominal Surgeries

Background: Postoperative pain following lower abdominal surgery is a major contributor to patient morbidity. The transversus abdominis plane (TAP) block provides effective regional analgesia, but its duration is limited by local anesthetic pharmacokinetics. Adjuvants such as dexamethasone and magnesium sulfate have been explored to prolong analgesia, though comparative evidence remains inconsistent. This study evaluated the efficacy of ropivacaine combined with dexamethasone versus ropivacaine with magnesium sulfate in ultrasound-guided TAP block. Methods: A randomized controlled trial was conducted in a tertiary care hospital in eastern India. One hundred twenty ASA I–II patients aged 18–60 years undergoing elective lower abdominal surgery under spinal anesthesia were randomized into two groups. Group RM received 20 mL of 0.2% ropivacaine with 1 mg magnesium sulfate per site, while Group RD received 20 mL of 0.2% ropivacaine with 8 mg dexamethasone per site. Bilateral TAP blocks were performed under ultrasound guidance at the end of surgery. Primary outcome was time to first rescue analgesia within 24 hours. Secondary outcomes included pain scores, total tramadol consumption, and hemodynamic parameters. Results: Baseline demographics were comparable. Group RM demonstrated a significantly longer time to first rescue analgesia (13.83 ± 2.96 h vs. 11.58 ± 2.87 h, p < 0.0001). However, Group RD showed consistently lower pain scores at 6, 12, and 24 hours (p < 0.001) and more stable hemodynamic trends. Conclusion: Both adjuvants enhanced TAP block efficacy but with distinct advantages. Magnesium sulfate prolonged the pain-free interval, whereas dexamethasone provided superior sustained analgesia and hemodynamic stability. Adjuvant selection should be tailored to clinical priorities-maximizing analgesia duration versus ensuring consistent pain control. Keywords: TAP block; Ropivacaine; Dexamethasone; Magnesium Sulfate; Postoperative Analgesia.