This prospective, observational, non-randomized clinical study aims to evaluate the intraoperative and postoperative effects of opioid-free multimodal anesthesia compared with opioid-containing anesthesia methods in adult patients undergoing lumbar spinal surgery. Patients will be managed according to routine clinical practice and assigned to one of three groups based on the analgesic strategy used by the attending anesthesiologist: (1) opioid-free anesthesia using multimodal agents and/or erector spinae plane (ESP) block; (2) ESP block plus intraoperative opioids; or (3) opioid-based anesthesia without regional blocks.

The primary objective is to compare postoperative pain control and opioid requirements within the first 48 hours after surgery. Secondary objectives include evaluating opioid-related side effects such as nausea, vomiting, pruritus, constipation, delayed mobilization, urinary retention, and postoperative complications classified according to the Clavien-Dindo system. Standard postoperative analgesia, including intravenous morphine patient-controlled analgesia (PCA), acetaminophen, and NSAIDs, will be provided for all patients.

The study aims to determine whether an opioid-free multimodal analgesic approach can reduce opioid consumption and related adverse effects while maintaining adequate analgesia in patients undergoing lumbar spinal surgery.

Lumbar spinal surgery, including lumbar canal stenosis and lumbar disc herniation procedures, is frequently associated with significant postoperative pain. Opioids are commonly used for perioperative analgesia; however, they may lead to several adverse effects such as nausea, vomiting, pruritus, constipation, urinary retention, delayed mobilization, and, less commonly, respiratory depression. In recent years, opioid-sparing and opioid-free multimodal analgesia strategies have gained increasing interest in an effort to minimize these side effects while maintaining effective pain control.

This prospective, observational, non-randomized study will evaluate the intraoperative and postoperative outcomes of three different anesthetic approaches routinely used in clinical practice for adult patients undergoing lumbar spinal surgery. Patients will be allocated into groups based on the independent decision of the attending anesthesiologist; the research team will not influence the anesthesia plan.

Group 1 (Opioid-free anesthesia): Patients receive multimodal analgesia (including agents such as acetaminophen, lidocaine, magnesium sulfate, ketamine, esmolol, and dexmedetomidine) and may undergo an erector spinae plane (ESP) block or other trunk blocks. No intraoperative opioids are administered.

Group 2 (ESP + opioid group): Patients receive an ESP block and multimodal analgesia, with the addition of intraoperative opioids such as remifentanil or morphine, as determined by the anesthesiologist.

Group 3 (Opioid-based anesthesia): Patients receive opioid-containing analgesia without the use of ESP or other truncal regional blocks.

All patients will receive standardized postoperative analgesia according to institutional guidelines, including intravenous morphine via patient-controlled analgesia (PCA), acetaminophen, and NSAIDs. Rescue analgesia will be provided as needed with intravenous morphine, acetaminophen, or tramadol.

Data will be collected regarding demographics, intraoperative hemodynamic parameters, anesthesia medications, intraoperative opioid and non-opioid consumption, urine output, depth of anesthesia (BIS), and surgery duration. Postoperative assessments will include pain scores (VAS and NRS at 0, 3, 6, 12, 24, and 48 hours), total opioid consumption, time to first analgesic request, patient satisfaction, postoperative complications, bowel function, mobilization time, urine output, vital signs, and length of stay. Complications will be classified using the Clavien-Dindo system to allow standardized comparison of postoperative morbidity across groups.

The primary objective of the study is to determine whether an opioid-free multimodal analgesia regimen provides effective postoperative pain control and reduces opioid requirements compared with opioid-containing strategies. Secondary objectives include evaluating the incidence of opioid-related adverse effects and the overall quality of recovery. By systematically comparing these three routinely used anesthetic approaches, the study aims to clarify the potential benefits of opioid-free anesthesia in lumbar spine surgery and support evidence-based perioperative analgesia strategies.

Inclusion Criteria:

• Adults aged 18 to 75 years
• Elective surgery only
• Scheduled for elective lumbar spinal surgery (lumbar spinal stenosis and/or lumbar disc herniation)
• ASA physical status I-III
• No previous lumbar spine surgery
• Able to provide written informed consent
• BIS monitoring available and recorded
• Ability to comply with postoperative pain assessment (NRS/VAS)
• Stable hemodynamic status preoperatively

Exclusion Criteria:

• Age younger than 18 or older than 75
• Inability or unwillingness to provide informed consent
• Severe psychiatric disease or cognitive impairment
• Emergency surgery cases
• BMI > 40 kg/m²
• Pregnancy
• Uncontrolled hypertension, arrhythmia, or severe cardiac disease
• Renal failure
• Chronic beta-blocker use
• Coagulation disorders
• Chronic alcohol dependence or substance use
• Neurological deficits affecting perception of pain
• Chronic pain syndrome (fibromyalgia, chronic LBP > 3 months)
• Chronic gabapentinoid use
• Anemia
• Known allergy to any anesthetic or analgesic agents used in the study
• Local infection at the intended ESP block injection site
• Intraoperative change in anesthetic technique that deviates from initial planned management
• Pediatric patients (<18 years)

Adult patients aged 18 to 75 years undergoing elective lumbar spine surgery for conditions such as lumbar spinal stenosis, lumbar disc herniation, degenerative spondylolisthesis, or lumbar disc degeneration at Marmara University Pendik Training and Research Hospital. All participants are surgical patients who meet the clinical indication for lumbar spinal procedures. No healthy volunteers are included. Patients are assigned to one of three observational cohorts based on the anesthesia technique chosen by the attending anesthesiologist in routine clinical practice.

Individual participant data (IPD) will not be shared. The study involves clinical information collected under institutional ethical approval, and no consent was obtained for external sharing of identifiable or de-identified participant-level data.