Single vs Multiple Injection Intertransverse Process Block in Breast Cancer Surgery

Study Objective This study aims to compare the effectiveness of single-level and multilevel intertransverse process (ITP) block techniques for the management of acute postoperative pain in patients undergoing breast cancer surgery.

The primary objective of this study is to compare the effects of single-level and multilevel intertransverse process (ITP) block techniques on postoperative Visual Analog Scale (VAS) pain scores in patients undergoing breast cancer surgery. Secondary outcomes include comparing total opioid consumption within the first 24 hours after surgery and postoperative quality of recovery between the two techniques.

Materials and Methods: This prospective, randomized clinical study will include voluntary female patients aged 18-65 years, classified as American Society of Anesthesiologists (ASA) physical status I-III, with a body mass index (BMI) \<35 kg/m². All participants will be informed about the study protocol in detail, and written informed consent will be obtained prior to inclusion. Patients will receive instruction on the use of the VAS for pain assessment, where 0 denotes no pain and 10 denotes the worst imaginable pain. Patients who meet the exclusion criteria will be withdrawn from the study. Participants will be randomly assigned to one of two groups using a computer- generated simple randomization method (https://www.randomizer.org). Randomization will be performed by a team member uninvolved in patient care, who will also prepare sealed opaque envelopes to conceal group allocation until shortly before block administration. Study Groups and Block Procedures: In the single-level ITP group, the block will be performed unilaterally at the T4-T5 intertransverse level with a single injection. In the multilevel ITP group, the block will be performed unilaterally at four intertransverse levels (T2-T3, T3-T4, T4-T5, and T5-T6).

All patients will be monitored with electrocardiography, peripheral oxygen saturation (SpO#), and non-invasive blood pressure prior to the block. Premedication with intravenous midazolam (0.02 mg/kg) will be administered.

Single-Level ITP Block:

The single-level Intertransverse Process (ITP) block will be performed 30 minutes prior to surgery with the patient in a sitting position. After skin disinfection with chlorhexidine, the skin and subcutaneous tissues will be anesthetized using 2-4 mL of 1% lidocaine (Aritmal®, Osel Pharmaceuticals, Turkey). A linear ultrasound probe (Mindray Diagnostic Ultrasound System, Model DC-T6) will be positioned over the T4 transverse process in a parasagittal orientation on the surgical side and then moved caudally to visualize the T4-T5 transverse processes. The probe will be adjusted slightly laterally and obliquely to optimize visualization of the intertransverse region, superior costotransverse ligament (SCTL), paravertebral space, and underlying pleura.

Using an in-plane approach, a 21G 0.8×100 mm echogenic insulated needle (Echoplex®+, Vygon SA, Écouen, France) will be advanced from lateral to medial, with the needle tip positioned immediately posterior to the SCTL at the T4-T5 intertransverse level. Proper needle placement will be confirmed by injection of 1-2 mL isotonic saline and sonographic visualization of appropriate injectate spread and anterior displacement of the pleura. Upon confirmation and negative aspiration, 20 mL of 0.25% bupivacaine hydrochloride (Buvasin®, Vem Pharmaceuticals, Turkey) will be administered.

The block performance time, defined as the duration from initial ultrasound probe contact with the skin to the final withdrawal of the needle following injection, will be recorded.

Multiple-Level ITP Block:

The multiple-level Intertransverse Process (ITP) block will be performed 30 minutes prior to surgery with the patient in a sitting position. After skin disinfection with chlorhexidine, the skin and subcutaneous tissues will be anesthetized using 2-4 mL of 1% lidocaine (Aritmal®, Osel Pharmaceuticals, Turkey). A linear ultrasound probe (Mindray Diagnostic Ultrasound System, Model DC-T6) will be positioned in a parasagittal orientation on the surgical side to sequentially identify the T2-T3, T3-T4, T4-T5, and T5-T6 intertransverse levels. At each level, the probe will be adjusted slightly laterally and obliquely to optimize visualization of the intertransverse region, SCTL, paravertebral space, and underlying pleura.

Using an in-plane approach, a 21G 0.8×100 mm echogenic insulated needle (Echoplex®+, Vygon SA, Écouen, France) will be advanced from lateral to medial, with the needle tip positioned immediately posterior to the SCTL at each intertransverse level. Proper needle placement will be confirmed by injection of 1-2 mL isotonic saline and sonographic visualization of appropriate injectate spread and anterior displacement of the pleura. Upon confirmation and negative aspiration, 5 mL of 0.25% bupivacaine hydrochloride (Buvasin®, Vem Pharmaceuticals, Turkey) will be administered at each of the T2-T3, T3-T4, T4-T5, and T5-T6 levels, resulting in a total volume of 20 mL.

The block performance time, defined as the duration from initial ultrasound probe contact with the skin to the final withdrawal of the needle following completion of all four injections, will be recorded.

General Anesthesia Upon entry into the operating room, patients will be monitored with electrocardiography, peripheral oxygen saturation (SpO#), and non-invasive blood pressure. Anesthesia will be induced with intravenous propofol (2 mg/kg, Polifarma Pharmaceutical Industry and Trade Inc., Ergene, Turkey), fentanyl citrate (1.5 mcg/kg, Polifarma Pharmaceutical Industry and Trade Inc., Ergene, Turkey), and rocuronium bromide (0.6 mg/kg, Muscuron®, Koçak Farma Pharmaceutical and Chemical Industry Co., Turkey). Anesthesia maintenance will be provided using 6% desflurane in a 40% oxygen-air mixture and a continuous remifentanil infusion at 0.05 mcg/kg/min. Mechanical ventilation settings will be adjusted to deliver a tidal volume of 6-8 mL/kg with end-tidal CO# maintained at 30-35 mmHg. Anesthetic depth will be monitored continuously using a Bispectral Index (BIS™) monitor (Medtronic plc, Dublin, Ireland), targeting a BIS value of 40-60. If heart rate or mean arterial pressure increases >20% from baseline, the remifentanil dose will be titrated accordingly. Thirty minutes before the end of surgery, all patients will receive 15 mg/kg of intravenous paracetamol (e.g., Paracerol®, Polifarma Pharmaceutical Industry and Trade Inc., Ergene, Turkey) and 1 mg/kg of intravenous tramadol. To prevent nausea and vomiting, 0.15 mg/kg of intravenous ondansetron will be administered. Patients with adequate spontaneous ventilation will be extubated and transferred to the post-anesthesia care unit (PACU). Hemodynamic Monitoring Heart rate, systolic blood pressure, diastolic blood pressure, mean arterial pressure, and oxygen saturation will be recorded at the following time points: pre-induction (baseline), 5 minutes after induction, 5 minutes after surgical incision, 15 minutes after incision, and at the end of surgery.

Postoperative Pain and Analgesic Use Pain will be assessed using the VAS at rest (static) and during movement (dynamic) at 0, 1, 4, 8, 12, and 24 hours postoperatively. All patients will use patient-controlled analgesia (PCA) without a basal infusion. The PCA device will be set to deliver 1 mg of morphine (0.2 mg/mL concentration) with a 10-minute lockout interval. Patients will be instructed to press the PCA button when VAS ≥4. Intravenous paracetamol will be administered every 8 hours. Rescue analgesia with intravenous tramadol (1 mg/kg) will be provided if VAS scores remain ≥4. The total amounts of opioids, NSAIDs, and other analgesics will be recorded. Postoperative Recovery Quality Postoperative recovery will be assessed using the 15-item Quality of Recovery-15 (QoR-15) questionnaire, which evaluates five domains: pain, physical comfort, physical independence, psychological support, and emotional state. Patient and Surgeon Satisfaction Satisfaction will be evaluated using a 5-point Likert scale, where 1 = not satisfied and 5 = very satisfied, based on verbal feedback from both the patient and the surgeon. Nausea and Vomiting

Nausea and vomiting will be scored using a 4-point scale:

0 = none

• mild
• moderate
• severe Potential Complications Any complications associated with the block or the surgical procedure (e.g., hematoma, pneumothorax, local anesthetic toxicity, vascular puncture, or infection) will be recorded.