Pectoral Nerve Block Versus Serratus Posterior Superior Intercostal Plane Block for Pain Control After Mastectomy (PECS-SPSIPB)

Participants will receive an ultrasound-guided SPSIP block on the surgical side before induction of general anesthesia. With the participant seated, 30 mL of 0.25% bupivacaine with epinephrine will be injected into the fascial plane between the serratus posterior superior and intercostal muscles at the third rib. Participants will also receive standardized general anesthesia and postoperative multimodal analgesia, including patient-controlled intravenous tramadol and rescue analgesia when required.

A single ultrasound-guided block will be performed on the surgical side before induction of general anesthesia. With the participant seated and the hand on the opposite shoulder, a high-frequency linear ultrasound probe will be positioned along the medial scapular border to identify the third rib and serratus posterior superior muscle. A 50-mm block needle will be advanced in-plane in a caudal-to-cranial direction. After confirming the plane with 5 mL of saline, 30 mL of 0.25% bupivacaine with epinephrine will be injected between the serratus posterior superior and intercostal muscles.

• Bloque SPSIP

Participants will receive an ultrasound-guided PECS II block on the surgical side before induction of general anesthesia. With the participant supine, 10 mL of 0.25% bupivacaine with epinephrine will be injected between the pectoralis major and pectoralis minor muscles, followed by 20 mL between the pectoralis minor and serratus anterior muscles. Participants will also receive standardized general anesthesia and postoperative multimodal analgesia, including patient-controlled intravenous tramadol and rescue analgesia when required.

A single ultrasound-guided PECS II block will be performed on the surgical side before induction of general anesthesia, with the participant supine. A high-frequency linear ultrasound probe will be used to identify the pectoralis major, pectoralis minor, and serratus anterior muscles. A 50-mm block needle will be advanced using an in-plane approach. After confirming each injection plane with 5 mL of saline, 10 mL of 0.25% bupivacaine with epinephrine will be injected between pectoralis major and pectoralis minor, followed by 20 mL of the same solution between pectoralis minor and serratus anterior.

• PECS II Block

Postoperative opioid consumption will be compared between the groups. Tramadol consumption administered through intravenous patient-controlled analgesia will be recorded in milligrams at 0, 2, 4, 8, 16, and 24 hours postoperatively. The total dose of rescue meperidine will be recorded separately.

Pain intensity at rest will be assessed using the Numeric Rating Scale (NRS), ranging from 0 (no pain) to 10 (the worst pain imaginable). Higher scores indicate greater pain intensity.

Pain intensity during movement will be assessed using the Numeric Rating Scale (NRS), ranging from 0 (no pain) to 10 (the worst pain imaginable). Higher scores indicate greater pain intensity.

The total dose of intravenous meperidine administered as rescue analgesia will be recorded in milligrams. Meperidine at 0.5 mg/kg will be administered when the Numeric Rating Scale score is 4 or higher.

The time of the first postoperative administration of rescue analgesia will be recorded. Intravenous meperidine at 0.5 mg/kg will be administered when the Numeric Rating Scale score is 4 or higher.

Quality of postoperative recovery will be assessed using the Quality of Recovery-15 (QoR-15) questionnaire. The questionnaire contains 15 items, with a total score ranging from 0 to 150. Higher scores indicate better quality of recovery.

Postoperative nausea and vomiting will be assessed using a four-category scale: 1 = no nausea or vomiting; 2 = nausea without vomiting; 3 = one episode of vomiting or persistent nausea; and 4 = two or more episodes of vomiting or severe/persistent retching. Higher scores indicate more severe symptoms.

Persistent postoperative pain will be assessed using the McGill Pain Questionnaire during a telephone interview at 3 months after surgery. Participants will provide prior consent for telephone follow-up.