Effect of Liposomal Bupivacaine TAPB Combined With Oxycodone PCIA on Postoperative Gastrointestinal Recovery in Patients Undergoing Major Abdominal Surgery

Rationale and Objective: The purpose of this study is to evaluate the clinical efficacy and safety of a novel multimodal analgesia regimen, combining transversus abdominis plane block (TAPB) with patient-controlled intravenous analgesia (PCIA), in improving postoperative gastrointestinal function recovery in patients undergoing major abdominal surgery. Study Design and Interventions: This is a prospective, single-center, randomized, double-blind, parallel-controlled trial. A total of 132 eligible patients (aged 18-80 years, ASA I-III, scheduled for elective small bowel or colorectal surgery) will be randomly allocated to one of three groups (n = 44 per group) to receive distinct postoperative analgesia regimens: Group R-S: 0.375% Ropivacaine TAPB + Sufentanil PCIA; Group LB-S: 266 mg Liposomal Bupivacaine TAPB + Sufentanil PCIA; Group LB-O: 266 mg Liposomal Bupivacaine TAPB + Oxycodone PCIA. Primary Outcome: The primary outcome is the area under the curve (AUC) of the I-FEED scoring system within the first 7 postoperative days, which comprehensively reflects the overall trajectory of gastrointestinal function recovery. Hypothesis: The investigators hypothesize that the combination of long-acting Liposomal Bupivacaine TAPB (for prolonged somatic pain relief) and Oxycodone PCIA (for precise visceral pain control via dual u and k receptor agonism) will synergistically attenuate the perioperative stress-inflammatory response. Consequently, this regimen is expected to significantly mitigate postoperative ileus (POI) and accelerate the recovery of gastrointestinal motility

Inclusion Criteria: * Patients scheduled to undergo elective major abdominal surgery, specifically small bowel or colorectal resections. * Aged between 18 and 80 years (inclusive). * American Society of Anesthesiologists (ASA) physical status I, II, or III. * Capable of understanding the study procedures, cooperating with postoperative pain/recovery assessments (e.g., VAS, QoR-15, I-FEED), and providing written informed consent prior to surgery. Exclusion Criteria: * History of significant neuropsychiatric disorders, including schizophrenia, epilepsy, Parkinson's disease, or myasthenia gravis, that may interfere with pain perception or cognitive evaluation. * History of alcohol abuse or chronic opioid/analgesic dependence. * Severe, uncontrolled hypertension (defined as systolic blood pressure ≥ 180 mmHg or diastolic blood pressure ≥ 110 mmHg). * Severe cardiac, hepatic, renal, or pulmonary dysfunction that poses a high surgical/anesthetic risk or alters drug metabolism. * Pregnant or lactating women. * Known allergy, hypersensitivity, or contraindications to any of the study medications, including local anesthetics (ropivacaine, bupivacaine) or opioids (sufentanil, oxycodone).