Postoperative pain following mastectomy may adversely affect early mobilization, patient comfort, and overall quality of recovery. Serratus anterior plane block is an ultrasound-guided regional anesthesia technique that provides analgesia to the anterolateral thoracic wall and is increasingly used as part of multimodal analgesia for breast surgery. Although the analgesic efficacy of serratus anterior plane block has been investigated in breast surgery, the clinical impact of the timing of block administration remains insufficiently defined.

This prospective, randomized, controlled, patient and assessor blinded clinical trial will compare two different timings of ultrasound-guided serratus anterior plane block in adult female patients undergoing elective unilateral mastectomy under general anesthesia. Participants will be randomized to receive serratus anterior plane block either after induction of general anesthesia and before surgical incision, or after completion of surgery and before extubation. In both groups, the block will be performed under ultrasound guidance using 25 mL of 0.25% bupivacaine.

The primary outcome is postoperative quality of recovery at 24 hours, assessed using the Quality of Recovery-15 questionnaire. Secondary outcomes include postoperative pain scores at predefined time points during the first 24 postoperative hours, intraoperative remifentanil consumption, postoperative opioid and non-opioid analgesic requirements, time to first analgesic requirement, postoperative nausea and vomiting, length of hospital stay, complications, inflammatory response markers including CRP and neutrophil-to-lymphocyte ratio, and intraoperative hemodynamic variables.

The study is planned to enroll 80 participants at a single tertiary training and research hospital. The findings are expected to clarify whether preincisional administration of serratus anterior plane block provides superior postoperative recovery, analgesic efficacy, and modulation of inflammatory response compared with administration at the end of surgery.

Inclusion Criteria:

• Female patients aged 18 years or older
• Scheduled for elective unilateral mastectomy surgery
• Planned to undergo surgery under general anesthesia
• American Society of Anesthesiologists physical status I-III
• Willing and able to participate in the study
• Provision of written informed consent

Exclusion Criteria:

• Refusal to participate in the study
• Known allergy to local anesthetics planned for use in the study
• Chronic opioid use
• Current steroid or immunosuppressive therapy
• Presence of chronic inflammatory disease
• Surgical duration shorter than 30 minutes
• Active infection
• Coagulopathy
• Infection at the planned block site
• Pregnancy or lactation
• Advanced hepatic failure or advanced renal failure
• Reoperation due to recurrent disease
• Inability to communicate adequately or to provide reliable pain scores
• Psychiatric or neurological condition limiting reliable completion of the QoR-15 questionnaire or Numeric Rating Scale assessments