Intertransverse Process Block Versus Erector Spinae Plane Block for Pain Relief in Lumbar Spine Surgery

Postoperative Pain Control, Lumbar Spine Surgery, Degenerative Lumbar Spine Diseases

Erector Spinae Plane Block, Intertransverse Process Block, Ultrasound-Guided Regional Anesthesia, Paraspinal Block, Opioid Consumption, Patient-Controlled Analgesia, Multimodal Analgesia

The goal of this clinical trial is to learn whether two types of ultrasound-guided nerve block, the intertransverse process block and the erector spinae plane block, reduce pain and the need for opioid pain medicines during and after lumbar spine surgery in adults. It also compares the two blocks with each other. The main questions it aims to answer are: Do patients who receive either nerve block need less morphine in the first 24 hours after surgery than patients who receive only local anesthetic injected at the skin incision? Is there a difference between the two nerve blocks in pain scores, the amount of opioid medicine needed during and after surgery, the time until patients first ask for pain medicine, and side effects? Researchers will compare three groups: an erector spinae plane block group, an intertransverse process block group, and a control group that receives local anesthetic infiltration at the incision site. Participants will: Be randomly assigned to one of the three groups before surgery Receive the nerve block on both sides of the spine with ropivacaine before general anesthesia (block groups), or local anesthetic infiltration along the planned incision after induction of anesthesia (control group) Undergo general anesthesia and lumbar spine surgery following the same standard protocol Use a patient-controlled analgesia pump that delivers morphine on demand for 24 hours after surgery Rate their pain at rest and during movement at set times over the first 24 hours, and be monitored for side effects such as nausea and vomiting

Background and rationale Lumbar spine surgery is associated with moderate to severe postoperative pain, and opioid-based analgesia is limited by side effects such as nausea, vomiting, sedation and respiratory depression. The erector spinae plane block (ESPB) is an established component of multimodal analgesia for spine surgery. The intertransverse process block (ITPB) is a more recently described paraspinal technique in which local anesthetic is injected into the tissue between adjacent transverse processes, closer to the paravertebral space. Direct comparisons of the two techniques in lumbar spine surgery are scarce. Block procedures Both blocks are performed bilaterally before induction of general anesthesia, with the patient prone, under ultrasound guidance using a low-frequency curvilinear probe and an in-plane approach with a 10-cm block needle. ESPB: the needle tip is placed between the deep surface of the erector spinae muscle and the posterior surface of the L3 transverse process. ITPB: the needle tip is placed in the intertransverse space between the L2 and L3 transverse processes, anterior to the erector spinae muscle and posterior to the intertransverse ligament-muscle complex, without advancing further anteriorly. Needle position is confirmed by hydrodissection with 2 mL of 0.9% saline after negative aspiration. Ropivacaine 0.375% (prepared from ropivacaine 0.5% and 0.9% saline in a 3:1 ratio) is administered at 2.5 mg/kg (maximum 150 mg), divided equally between the two sides. Sensory block is assessed by pinprick 20 minutes after injection using the Hollmén scale, and the cranial and caudal extent of the block is measured in centimetres from the injection level. A block is considered failed if no sensory change is detected 30 minutes after injection. In the control group, after induction of anesthesia, the surgeon infiltrates 20 mL of 1% lidocaine with epinephrine 1:200,000 into the skin and subcutaneous tissue along both sides of the planned incision before skin incision. Anesthesia protocol (all groups) Anesthesia is induced with fentanyl 2 µg/kg, propofol 2-3 mg/kg and rocuronium 0.6 mg/kg, and maintained with sevoflurane at 1-1.5 MAC. Nociceptive response is assessed using the PRST score (blood pressure, heart rate, sweating, tearing). If PRST is ≥ 4, fentanyl 50 µg is given intravenously and may be repeated after 5 minutes. Paracetamol 1 g IV is given approximately 30 minutes before the end of surgery. Postoperative analgesia Once patients are awake in the recovery room and able to rate pain and use the device, intravenous morphine patient-controlled analgesia (PCA) is started: morphine 1 mg/mL, bolus 1 mg, lockout interval 8 minutes, no background infusion, maximum 15 mg per 4 hours. Patients are instructed to press the PCA button when pain is VAS ≥ 4. H0 is defined as the time the patient is awake in the recovery room and able to self-report pain and use PCA. Sample size Sample size was calculated for comparison of 24-hour morphine consumption between a block group and the control group, assuming a standard deviation of 6.54 mg (from a previous Vietnamese study of ESPB in lumbar spine surgery) and a minimum clinically important difference of 5 mg, with two-sided α = 0.05 and 80% power. This gave 27 patients per group; allowing for about 10% dropout, 30 patients per group (90 in total) were enrolled. Randomization and statistical analysis Eligible patients are randomly allocated in a 1:1:1 ratio to the three groups by drawing lots. Continuous variables are compared using one-way ANOVA or the Kruskal-Wallis test, as appropriate, and categorical variables using the chi-square or Fisher's exact test. Pairwise comparisons are adjusted with the Bonferroni method. Two-sided p \< 0.05 is considered statistically significant. Analyses are performed with SPSS version 20.0.

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