Comparison of Postoperative Analgesic Efficacy of Superior Posterior Serratus Intercostal Plane Block (SPSIP) and Anterior Serratus Plane Block in Modified Radical Mastectomy Surgery

Breast cancer surgery, particularly modified radical mastectomy, is frequently associated with moderate to severe postoperative pain. Inadequate pain control may impair respiratory function, delay mobilization, prolong hospital stay, increase opioid consumption, and contribute to the development of persistent postsurgical pain. Therefore, effective multimodal analgesia incorporating regional anesthesia techniques has become an important component of perioperative care in breast surgery.

Among ultrasound-guided fascial plane blocks, the serratus anterior plane block (SAPB) has been widely adopted because of its ability to block the lateral cutaneous branches of the intercostal nerves, resulting in reduced postoperative pain scores and opioid requirements. More recently, the serratus posterior superior intercostal plane block (SPSIPB) has been introduced as a novel interfascial block that may provide broader thoracic dermatomal spread through injection between the serratus posterior superior and intercostal muscles. Although early clinical reports have demonstrated promising analgesic efficacy, comparative evidence between SPSIPB and SAPB in breast surgery remains limited.

This study is designed as a prospective, randomized, double-blind, single-center clinical trial to compare the analgesic efficacy of ultrasound-guided SPSIPB and SAPB in patients undergoing modified radical mastectomy under general anesthesia. Seventy female patients aged 18 to 65 years with American Society of Anesthesiologists (ASA) physical status I-III who meet the eligibility criteria will be enrolled after providing written informed consent. Participants will be randomized in a 1:1 ratio using sealed-envelope allocation to receive either ultrasound-guided SPSIPB or SAPB before induction of general anesthesia. Both blocks will be performed using 30 mL of 0.25% bupivacaine under standardized ultrasound guidance by experienced anesthesiologists.

General anesthesia and postoperative analgesic management will be standardized for all participants. Intraoperative anesthetic management will include propofol, fentanyl, rocuronium, sevoflurane, and remifentanil according to institutional practice. Following surgery, all patients will receive standardized multimodal analgesia consisting of intravenous paracetamol, tramadol patient-controlled analgesia (PCA), and rescue analgesics when clinically indicated.

The primary outcome is postoperative pain intensity assessed using the Visual Analog Scale (VAS) at predefined postoperative time points. Secondary outcomes include intraoperative remifentanil consumption, cumulative tramadol consumption during the first 24 postoperative hours, postoperative nausea and vomiting (PONV) scores, rescue analgesic requirements, quality of recovery measured using the QoR-40 questionnaire at 24 hours, block-related complications, and other postoperative adverse events.