This study aims to evaluate the effect of continuous erector spinae plane block (CESPB) using ropivacaine on postoperative pain in patients undergoing elective mastectomy. In addition to pain control, this study investigates the impact of CESPB on systemic inflammatory response as measured by nuclear factor kappa B (NF-κB) levels, opioid consumption, and quality of recovery. Patients will be randomly assigned to receive CESPB or standard analgesia without block. Outcomes will be assessed within the first 24 hours after surgery. The findings are expected to provide evidence on the clinical and biological benefits of CESPB as part of multimodal analgesia in breast surgery.

Breast cancer is one of the most common malignancies worldwide and frequently requires surgical management in the form of mastectomy. Postoperative pain following mastectomy remains a significant clinical problem, with a substantial proportion of patients experiencing moderate to severe pain. Inadequate pain control is associated with increased opioid consumption, delayed recovery, and a higher risk of developing chronic pain.

The inflammatory response plays an important role in postoperative pain, particularly through the activation of nuclear factor kappa B (NF-κB), a key transcription factor that regulates pro-inflammatory mediators. Increased NF-κB activity has been associated with enhanced nociception and poorer recovery outcomes. Therefore, perioperative strategies that can reduce both pain and inflammatory response are of clinical importance.

Continuous erector spinae plane block (CESPB) is a regional anesthesia technique that provides multidermatomal analgesia by delivering local anesthetic into the fascial plane adjacent to the erector spinae muscle. Compared to single-shot techniques, CESPB using a catheter allows prolonged and stable analgesia. Ropivacaine is commonly used due to its favorable safety profile and potential anti-inflammatory effects.

This study is designed as a randomized controlled trial to compare CESPB using ropivacaine with standard analgesia without block in patients undergoing elective mastectomy. The primary outcome is postoperative pain intensity within 24 hours after surgery. Secondary outcomes include NF-κB levels, opioid consumption, incidence of postoperative nausea and vomiting, and quality of recovery measured using the QoR-15 questionnaire.

By integrating clinical and biomolecular outcomes, this study aims to provide comprehensive evidence regarding the effectiveness of CESPB not only in pain control but also in modulating the inflammatory response and improving postoperative recovery.

Inclusion Criteria:

• Female patients aged 18 to 65 years
• Diagnosed with breast cancer
• Scheduled for elective mastectomy under general anesthesia
• American Society of Anesthesiologists (ASA) physical status I-III
• Able to understand and provide written informed consent
• Body mass index (BMI) 18-29 kg/m²

Exclusion Criteria:

• Contraindications to regional anesthesia
• Contraindications or allergy to ropivacaine or local anesthetics
• Inability to use a visual analog scale (VAS) for pain assessment
• Inability to understand or operate patient-controlled analgesia (PCA)
• History of chronic pain or ongoing infection requiring treatment
• History of chronic analgesic use
• History of autoimmune disease
• Uncontrolled systemic disease

Individual participant data (IPD) will not be shared due to the presence of sensitive patient information and to ensure the confidentiality and privacy of research subjects in accordance with ethical guidelines.

Outcome assessors will be blinded to group allocation. Due to the nature of the intervention, participants and care providers will not be blinded.