Postoperative pain following modified radical mastectomy remains a significant clinical concern and may adversely affect patient recovery, opioid consumption, and overall patient satisfaction. Ultrasound-guided regional anesthesia techniques have gained increasing importance as part of multimodal analgesia strategies in breast surgery. The serratus anterior plane (SAP) block is a commonly used interfascial plane block for postoperative analgesia in thoracic and breast procedures. Recently, the serratus posterior superior intercostal plane (SPSIP) block has emerged as a novel regional anesthesia technique with potentially wider thoracic dermatomal spread and effective analgesic properties.

This prospective randomized controlled study aims to compare the postoperative analgesic efficacy of the SPSIP block and SAP block in patients undergoing modified radical mastectomy under general anesthesia. Patients will be randomly allocated into two groups to receive either ultrasound-guided SPSIP block or SAP block preoperatively. Primary outcomes will include postoperative pain scores and opioid consumption within the first 24 hours after surgery. Secondary outcomes will include time to first analgesic request, rescue analgesic requirements, intraoperative hemodynamic parameters, postoperative nausea and vomiting, block-related complications, and patient satisfaction.

The study is designed to evaluate whether SPSIP block provides superior postoperative analgesia compared with SAP block in modified radical mastectomy surgery.

This prospective, randomized, controlled clinical study is designed to compare the postoperative analgesic efficacy of the ultrasound-guided Serratus Posterior Superior Intercostal Plane (SPSIP) block and Serratus Anterior Plane (SAP) block in patients undergoing modified radical mastectomy under general anesthesia. Postoperative pain after breast cancer surgery remains an important clinical problem and may negatively affect respiratory function, early mobilization, recovery quality, patient satisfaction, and postoperative opioid consumption. Effective perioperative analgesia is therefore an essential component of enhanced recovery protocols in breast surgery.

Regional anesthesia techniques have increasingly been incorporated into multimodal analgesia strategies to reduce opioid-related adverse effects and improve postoperative pain control. The SAP block is widely used in breast and thoracic surgery due to its ability to provide analgesia to the lateral thoracic wall through blockade of the lateral cutaneous branches of the intercostal nerves. However, recently described fascial plane blocks such as the SPSIP block may provide broader dermatomal spread and more effective thoracic analgesia. Despite growing interest in the SPSIP block, evidence regarding its analgesic efficacy in breast surgery remains limited.

The study will include adult female patients scheduled for elective modified radical mastectomy under general anesthesia. Following enrollment and randomization, patients will be allocated to receive either ultrasound-guided SPSIP block or SAP block preoperatively in addition to standardized general anesthesia and multimodal analgesia protocols. All regional blocks will be performed under sterile conditions using ultrasound guidance by experienced anesthesiologists. Standard intraoperative monitoring will be applied throughout the surgical procedure.

Perioperative anesthetic management will be standardized as much as possible to minimize confounding factors affecting postoperative pain outcomes. Intraoperative opioid administration, hemodynamic parameters, and anesthetic requirements will be recorded. Postoperative analgesia protocols, including rescue analgesic administration criteria, will also be standardized for all participants.

The primary aim of the study is to evaluate and compare postoperative analgesic effectiveness between SPSIP and SAP blocks. Analgesic efficacy will be assessed using postoperative pain scores at predefined time intervals and cumulative opioid consumption during the postoperative period. Additional perioperative parameters related to recovery and analgesic quality will also be evaluated to determine the clinical utility of these interfascial plane blocks in breast surgery.

This study is expected to contribute to the current literature regarding novel regional anesthesia techniques for breast surgery and may help define the role of SPSIP block as an alternative or superior analgesic approach compared with SAP block in modified radical mastectomy patients.

Inclusion Criteria:

• Female patients aged between 18 and 65 years
• American Society of Anesthesiologists (ASA) physical status I-III
• Body Mass Index (BMI) <35 kg/m²
• Normal International Normalized Ratio (INR) value and platelet count
• Normal liver and renal function tests
• Patients scheduled for elective modified radical mastectomy surgery

Exclusion Criteria:

• Bleeding diathesis
• Allergy to local anesthetic agents
• Suspected infection or inflammation at the planned block site
• ASA physical status IV or higher
• Long-term medication use due to chronic pain
• Advanced hepatic or renal failure
• Presence of severe pulmonary disease
• Use of any opioid medication within 24 hours before surgery
• Cognitive impairment
• Patients undergoing revision surgery

Participants who self-identify as female and are scheduled for modified radical mastectomy surgery will be eligible for enrollment in the study.