This study aims to evaluate the effect of serratus posterior superior intercostal plane (SPSIP) block on postoperative pain, opioid consumption, and analgesic requirements in patients undergoing mastectomy and axillary lymph node dissection

This study is a prospective, randomized, placebo-controlled, multicenter clinical trial designed to evaluate the analgesic efficacy of the serratus posterior superior intercostal plane (SPSIP) block in patients undergoing mastectomy with axillary lymph node dissection. Postoperative pain following breast surgery is often significant and may increase opioid consumption and related adverse effects, highlighting the need for effective regional anesthesia techniques.

The SPSIP block is a novel ultrasound-guided interfascial plane block with emerging evidence in thoracic and chest wall procedures; however, its role in breast surgery remains unclear, particularly in placebo-controlled settings. This study aims to determine whether the SPSIP block provides additional benefit as part of a standardized multimodal analgesia approach.

Participants will be randomly assigned to receive either SPSIP block with local anesthetic or a placebo intervention under identical conditions, with blinding applied to all relevant parties. All patients will receive the same perioperative anesthesia and analgesia protocol.

The results of this study are expected to clarify the clinical value of SPSIP block in breast surgery and contribute to the development of evidence-based postoperative pain management strategies.

Inclusion Criteria:

• Female patients aged 18-65 years
• ASA physical status I-III
• Scheduled for elective unilateral mastectomy with axillary lymph node dissection under general anesthesia
• Able to understand and use the Numeric Rating Scale (NRS) for pain assessment
• Provided written informed consent

Exclusion Criteria:

• Known allergy or hypersensitivity to local anesthetics (e.g., bupivacaine)
• Coagulopathy, thrombocytopenia (<100,000/mm³), or ongoing anticoagulant/antiplatelet therapy that cannot be discontinued
• Infection or skin lesion at the injection site
• Planned bilateral surgery or additional major surgical procedures
• Chronic pain conditions or regular use of opioids, gabapentinoids, or centrally acting analgesics
• Neurological or psychiatric conditions interfering with pain assessment
• History of previous major thoracic or chest wall surgery on the same side
• Pregnancy or breastfeeding
• Refusal to participate or inability to provide informed consent

De-identified individual participant data that underlie the results reported in this article (text, tables, figures, and appendices) will be shared.

Time Frame: "Starting 6 months and ending 36 months following article publication

Data will be available to researchers who provide a methodologically sound proposal. Proposals should be directed to : acilfatma@gmail.com

Participants, care providers, investigators, and outcome assessors will be blinded to group allocation. Study solutions (local anesthetic or saline) will be prepared by an independent anesthesiologist not involved in patient care or data collection. Syringes will be identical in appearance, volume, and labeling. Randomization assignments will be concealed using sealed opaque envelopes.