Efficacy of magnesium sulfate as an adjuvant to ropivacaine in transversus abdominis plane block for postoperative analgesia after laparoscopic radical gastrectomy: a double-blinded randomized controlled trial

Effective postoperative pain management is critical after laparoscopic radical gastrectomy. Magnesium sulfate, an N-methyl-D-aspartate receptor antagonist, may potentiate local anesthetic effects. This study evaluated whether adding magnesium sulfate to ropivacaine in a transversus abdominis plane block (TAPB) improves analgesia. In this prospective, double-blind, randomized trial, 168 patients (ASA II–III) scheduled for elective laparoscopic radical gastrectomy received bilateral TAPB, with 20 mL solution injected per side; patients were allocated to receive 0.33% ropivacaine alone (Group R) or 0.33% ropivacaine combined with 150 mg (RLM), 250 mg (RMM), or 500 mg (RHM) magnesium sulfate. The primary outcome was resting Visual Analog Scale (VAS) pain score at 6 h postoperatively. Secondary outcomes included coughing VAS at 6 h; resting and coughing VAS at 12–72 h; Quality of Recovery-15 (QoR-15) scores on postoperative days 1–3; cumulative opioid consumption; time to first rescue analgesia, ambulation, and flatus; length of AICU and hospital stay; and adverse events, including magnesium-related complications. Compared with ropivacaine alone, the addition of magnesium sulfate significantly reduced postoperative pain scores, opioid consumption, rescue analgesic requirements, and patient-controlled analgesia activations, while prolonging the duration of analgesia and improving QoR-15 scores. Groups RMM and RHM produced superior analgesic efficacy compared with Group RLM. No severe block-related adverse events were recorded in all cohorts. No clear superiority of Group RHM over Group RMM was demonstrated for the primary outcome or most secondary outcomes. Magnesium sulfate is an effective and well-tolerated adjuvant to ropivacaine for ultrasound-guided TAP block after laparoscopic radical gastrectomy. Both 250 mg and 500 mg improved postoperative analgesia and recovery compared with 150 mg, whereas 250 mg is non-inferior to 500 mg in analgesic efficacy and postoperative recovery indicators. ChiCTR2500096420.