This prospective observational study aims to compare the effects of the Quadro-Iliac Plane Block (QIPB) and wound infiltration (WI) on postoperative acute pain in adult patients undergoing elective single-level lumbar discectomy. QIPB is a newly introduced ultrasound-guided fascial plane block, and it is currently being used in routine clinical practice in our anesthesiology department as part of postoperative analgesia for lumbar spine surgery. Wound infiltration is a conventional method in which local anesthetic is injected into the surgical field at the end of the procedure.

In this study, eligible patients will be monitored prospectively without randomization or alteration of standard care. Postoperative pain scores, opioid consumption, nausea and vomiting, patient satisfaction, and recovery parameters will be evaluated during the first 24 hours after surgery. The study aims to provide real-world clinical evidence comparing these two analgesic techniques in lumbar discectomy patients.

This prospective observational study aims to evaluate and compare the postoperative analgesic outcomes of two routinely used analgesic techniques-Quadro-Iliac Plane Block (QIPB) and wound infiltration (WI)-in adult patients undergoing elective single-level lumbar discectomy. Both QIPB and WI are standard components of postoperative pain management in our hospital, and the type of analgesic technique administered to each patient is determined solely by the attending anesthesiologist based on routine clinical judgment. The research team does not influence clinical decision-making, perform block procedures, or modify any aspect of patient care. All interventions included in this study reflect standard institutional practice.

The primary objective is to compare cumulative opioid consumption during the first 24 hours after surgery between patients receiving QIPB and those receiving WI. Secondary objectives include evaluating postoperative pain scores, early recovery parameters, patient satisfaction, postoperative nausea and vomiting (PONV), rescue analgesic requirements, block-related complications, and hospital length of stay.

Clinical Routine and Analgesic Protocol

All patients will be managed according to the standard multimodal analgesia protocol routinely used in our neurosurgery operating room. Intraoperatively, intravenous tenoxicam 20 mg, tramadol 100 mg and dexamethasone 8 mg will be administered as part of routine analgesic and antiemetic care. Paracetamol 1 g IV will be given at the end of surgery and continued at regular intervals postoperatively. Rescue analgesia will consist of intravenous tramadol 100 mg infused over 30 minutes, with a maximum daily dose of 300 mg; if pain remains uncontrolled (NRS ≥4). All patients will receive intravenous morphine patient-controlled analgesia (Body Guard 575 Pain Manager) with a standard setting of 1 mg bolus dose, a 10-minute lockout interval, and a 4-hour limit set to 80% of the maximum allowable dose.

Block Techniques (Performed as Part of Routine Care)

QIPB Group:

QIPB is a newly introduced interfascial block technique currently used in our clinic for postoperative lumbar spine analgesia. At the end of surgery and before extubation, the patient is placed in the prone position. A low-frequency convex ultrasound probe (2-6 MHz) is positioned at the L3 midline in the transverse plane to identify the spinous process. The probe is then moved laterally and caudally to visualize the attachment of the quadratus lumborum muscle to the iliac crest. Under ultrasound guidance, a 22G, 100-mm block needle is advanced into the fascial plane between the quadratus lumborum and erector spinae muscles. A total of 60 mL of 0.25% bupivacaine (30 mL per side) is injected bilaterally. The procedure is performed by experienced anesthesiologists as part of normal clinical practice.

Wound Infiltration Group (WI):

WI is a routine analgesic method performed in our operating room. At the end of surgery, before skin closure, 20 mL of 0.25% bupivacaine is infiltrated into the surgical field in multiple tissue layers. This procedure is performed entirely according to the attending anesthesiologist's habitual clinical practice.

Postoperative Assessment

Postoperative pain will be assessed using the 11-point Numeric Rating Scale (NRS; 0-10) at rest and during movement (deep breathing or coughing) at 0, 3, 6, 12, and 24 hours after surgery. PONV will be evaluated using a verbal descriptive scale. If PONV score is ≥3, 4 mg IV ondansetron will be administered. Patient satisfaction and quality of recovery will be assessed using the Turkish version of the QoR-15 questionnaire preoperatively, on postoperative day 1, and at discharge.

Block-related complications (hematoma, bleeding at the injection site, LAST), opioid-related side effects (itching, sedation, respiratory depression), time to first PCA demand, time to first mobilization, rescue analgesic requirements, and hospital length of stay will be recorded.

All data will be analyzed using SPSS software. Statistical tests will be selected based on data distribution, and a p-value < 0.05 will be considered statistically significant.

Inclusion Criteria:

• Adults aged 18 to 80 years
• Scheduled for elective single-level lumbar discectomy
• ASA physical status I-III
• Able to use patient-controlled analgesia (PCA)
• Able and willing to provide written informed consent

Exclusion Criteria:

• History of opioid use for longer than 4 weeks
• Presence of chronic pain before surgery (e.g., migraine, fibromyalgia)
• Alcohol or substance dependence
• Known allergy or hypersensitivity to local anesthetics or opioids
• Significant organ dysfunction (e.g., severe hepatic or renal disease)
• Revision or multilevel spine surgery
• Contraindications to regional anesthesia
• Severe psychiatric disorders limiting cooperation (e.g., psychosis, dementia)
• Pregnancy or breastfeeding
• Hematologic disorders

Adult patients scheduled to undergo elective single-level lumbar discectomy at Karabuk Training and Research Hospital. Eligible participants will be evaluated preoperatively and enrolled prospectively according to predefined inclusion and exclusion criteria. No healthy volunteers are included.