Effect of Postoperative Analgesia of Oliceridine Fumarate for Gastrointestinal Function Recovery in Patients Undergoing Lumbar Spine Surgery

Inclusion Criteria: * Age between 18 and 75 years old; * Patients undergoing lumbar surgery under general anesthesia (within 3 segments) and expected to receive postoperative patient-controlled analgesia; * ASA classification I-III; * BMI between 18 and 30 kg/m²; * Informed consent obtained from the patient. Exclusion Criteria: * Use of any painkillers within 3 days before surgery; or long-term treatment with non-steroidal anti-inflammatory drugs (NSAIDs), defined as: within 3 months before surgery, use of NSAIDs daily for more than 2 consecutive weeks; * Presence of intestinal obstruction or suspicious symptoms: nausea and vomiting, abdominal bloating and pain, cessation of gas or bowel movements within the past two weeks, imaging suggesting intestinal dilation, or large amounts of air-fluid levels; * Patients with severe liver dysfunction (based on Child-Pugh classification, grade C); * History of or planned gastrointestinal surgery; * Patients allergic to the study drug; * Pregnant or breastfeeding patients; * QTcF abnormalities, males \>450 ms, females \>470 ms; * Participation in other drug trials within the past 30 days; * Long-term use of opioids (defined as: within 12 months before surgery, use for more than 1 month, more than 3 days per week, with daily doses exceeding 15 mg morphine equivalent); * Pre-existing neurological or psychiatric disorders: such as epilepsy, depression, schizophrenia, etc.; * Patients deemed unsuitable for this study by the investigator.