Ultrasound-Guided SPSIP Versus ESPB for Postoperative Pain After Modified Radical Mastectomy

Breast cancer represents a major global health burden and remains one of the leading causes of cancer-related mortality among women. Modified radical mastectomy (MRM) is frequently performed as part of surgical management. Despite advances in perioperative care, postoperative pain following MRM remains significant due to extensive tissue dissection involving skin, muscles, and intercostal nerves. Inadequate postoperative analgesia may result in delayed mobilization, increased opioid consumption, higher incidence of opioid-related adverse effects, prolonged hospital stay, and potential development of chronic post-mastectomy pain syndrome. Ultrasound-guided fascial plane blocks have gained popularity as part of multimodal analgesia strategies in breast surgery. The erector spinae plane block (ESPB) involves injection of local anesthetic deep to the erector spinae muscle at the thoracic level, allowing spread to dorsal and ventral rami of spinal nerves. ESPB has demonstrated effectiveness in reducing postoperative pain scores and opioid consumption after breast surgery. The serratus posterior superior intercostal plane (SPSIP) block is a recently described regional anesthesia technique. It involves ultrasound-guided injection of local anesthetic into the fascial plane between the serratus posterior superior muscle and the intercostal muscles, targeting the intercostal nerves. Preliminary reports suggest that SPSIP may provide effective thoracic analgesia with a favorable safety profile. This prospective randomized clinical trial will include 50 female breast cancer patients undergoing modified radical mastectomy at the National Cancer Institute, Cairo University. Patients will be randomly assigned into two equal groups: Group SPSIP: Ultrasound-guided serratus posterior superior intercostal plane block. Group ESPB: Ultrasound-guided erector spinae plane block. Both blocks will be performed preoperatively under ultrasound guidance using 20 mL of 0.25% bupivacaine. All patients will receive standardized general anesthesia and multimodal analgesia. The primary outcome measure is total morphine consumption during the first 24 hours postoperatively. Secondary outcomes include: Visual Analog Scale (VAS) pain scores at rest and during movement at predefined time intervals (1, 3, 6, 12, 18, and 24 hours) Time to first request for rescue analgesia Hemodynamic parameters intraoperatively and postoperatively Recovery time Patient satisfaction Incidence of adverse effects such as nausea and vomiting The study hypothesis is that SPSIP block provides postoperative analgesia comparable or superior to ESPB in patients undergoing modified radical mastectomy. The results of this study may contribute to optimizing regional anesthesia strategies for breast cancer surgery and support evidence-based, opioid-sparing perioperative pain management.