Breast surgery is one of the most common surgical procedures worldwide. Pain after surgery is an important issue because it affects recovery and mobility. It can also increase the risk of breathing problems.

Although opioids are effective for pain relief, they can cause side effects like nausea, vomiting, and breathing difficulties. These side effects can negatively impact patients and their recovery. Reducing opioid use is important for ensuring patient safety and improving the recovery process.

To manage pain after breast surgery, two types of nerve blocks can be used: the erector spinae plane block (ESPB) and the serratus posterior superior intercostal plane block (SPSIP). Both methods are effective for providing pain relief after surgery. However, there are not enough studies comparing which method is better.

Purpose of the Study: The main aim of this study is to evaluate the effect of ultrasound-guided ESPB and SPSIP blocks on opioid use after breast surgery. Additionally, we will compare opioid-related side effects (like nausea, vomiting, and breathing problems) and pain levels measured with the NRS (Numeric Rating Scale) between the two groups.

Introduction Breast surgery is one of the most commonly performed surgical procedures worldwide. Postoperative pain is a significant issue as it impacts recovery and mobilization. Additionally, postoperative pain increases the risk of respiratory complications.

Although opioid analgesics are effective in controlling pain, their side effects, such as nausea, vomiting, and respiratory depression, can lead to undesirable outcomes. Reducing opioid use is critical for both patient safety and improving the quality of recovery.

For managing postoperative pain following breast surgery, the erector spinae plane block (ESPB) and the more recently introduced serratus posterior superior intercostal plane block (SPSIP) have been utilized. Both techniques have been effectively used for analgesia in patients undergoing breast surgery.

However, there is insufficient evidence in the literature comparing the efficacy of these two techniques in this context.

Aim of the Study The primary aim of this study is to evaluate the effect of ultrasound-guided ESPB and SPSIP blocks on postoperative opioid consumption following breast surgery. Additionally, the secondary aim is to compare opioid-related side effects (e.g., nausea, vomiting, respiratory depression) and postoperative NRS (Numerical Rating Scale) pain scores between the groups.

Materials and Methods This prospective, randomized controlled trial will be conducted at Medipol Mega University Hospital on patients undergoing breast surgery and axillary lymph node dissection. The study aims to evaluate the effects of ESPB and SPSIP applications on postoperative opioid consumption and pain management. Written and verbal informed consent will be obtained from all participants prior to the study.

Patient Selection Patients aged 18-80 years, classified as ASA (American Society of Anesthesiologists) physical status I-III, and scheduled for breast surgery with axillary lymph node dissection will be included. Patients with a history of allergies, known allergy to local anesthetics, pregnancy, or psychiatric or neurological disorders will be excluded.

Group Allocation

Patients will be randomized into three groups:

Group 1 (Control group): Patients will not receive any nerve block. Group 2 (ESPB group): Patients will receive an erector spinae plane block. Group 3 (SPSIP group): Patients will receive a serratus posterior superior intercostal plane block.

Anesthesia Management All patients will receive routine anesthesia protocols. After entering the operating room, patients will be monitored with electrocardiography, peripheral oxygen saturation (SpO₂), and non-invasive blood pressure. Premedication with 2 mg intravenous midazolam will be administered.

Anesthesia induction will include 2-2.5 mg/kg IV propofol, 1-1.5 µg/kg IV fentanyl, and 0.6 mg/kg IV rocuronium, followed by intubation. Patients will be ventilated with a 50% oxygen-air mixture. Maintenance of anesthesia will be achieved with intermittent doses of midazolam, fentanyl, and rocuronium. Ventilator settings will include a tidal volume of 6-8 mL/kg and an end-tidal CO₂ of 30-35 mmHg.

All patients will receive 1 g intravenous paracetamol and 100 mg intravenous tramadol 30 minutes before the end of surgery. To prevent postoperative nausea and vomiting, 4 mg intravenous ondansetron will be administered.

Erector Spinae Plane Block Procedure In Group 2, ESPB will be performed following the surgical procedure but before the patient is awakened. The block will be performed under sterile conditions using ultrasound guidance.

Patient Positioning and Preparation: The patient will be positioned laterally with the surgical side up. A sterile ultrasound probe cover will be used.

Ultrasound Imaging: A high-frequency (11-12 MHz) linear ultrasound probe will be placed transversely over the T5 thoracic vertebra.

Identification of Anatomy: The erector spinae muscle and transverse processes will be identified.

Needle Insertion: Using an in-plane technique, the block needle will be advanced to the transverse process.

Injection Confirmation: After confirming the needle position with a 1-2 mL saline injection, 30 mL of 0.25% bupivacaine will be injected between the erector spinae muscle and the transverse process. Spread of the local anesthetic will be monitored via ultrasound.

Serratus Posterior Superior Intercostal Plane Block Procedure In Group 3, SPSIPB will also be performed following the surgical procedure but before the patient is awakened. The block will be performed under sterile conditions using ultrasound guidance.

Patient Positioning and Preparation: The patient will be positioned laterally with the surgical side up. A sterile ultrasound probe cover will be used.

Ultrasound Imaging: A high-frequency (11-12 MHz) linear ultrasound probe will be placed sagittally at the upper corner of the scapula. The rhomboid major, trapezius, serratus posterior superior muscles, and the third rib will be visualized.

Identification of Anatomy: The third rib and serratus posterior superior muscle will be identified.

Needle Insertion: Using an in-plane technique, the block needle will be advanced between the serratus posterior superior muscle and the third rib.

Injection Confirmation: After confirming the needle position with a 1-2 mL saline injection, 30 mL of 0.25% bupivacaine will be injected into the space between the serratus posterior superior muscle and the third rib. Spread of the local anesthetic will be monitored via ultrasound.

Postoperative Assessment Pain levels will be assessed during the first 24 hours postoperatively. Patients will routinely receive 1,000 mg paracetamol three times daily. Pain scores will be evaluated using the Numerical Rating Scale (NRS), where 0 indicates "no pain" and 10 indicates "worst pain imaginable."

Pain scores at rest and during mobilization will be recorded at the recovery unit, as well as at 3, 6, 12, 18, and 24 hours postoperatively. If the NRS score is ≥4, 1 mg/kg IV tramadol will be administered as rescue analgesia. The total amount of rescue analgesic used, postoperative opioid consumption, and side effects such as nausea, vomiting, itching, and complications like hematoma will be documented.

Inclusion Criteria:

• aged 18-80 years
• Classified as ASA (American Society of Anesthesiologists) physical status I-III
• Scheduled for breast surgery with axillary lymph node dissection

Exclusion Criteria:

• Patients with a history of allergies
• allergic to local anesthetics
• pregnant women
• psychiatric or neurological disorders

only IPD used in the results publication