Coronary Artery Bypass Grafting (CABG) is a common surgical procedure for ischemic heart disease, but it often leads to severe acute and chronic postoperative pain, which can delay recovery and reduce patient comfort. Effective pain management is crucial to prevent pulmonary complications and long hospital stays. Peripheral nerve blocks are increasingly used to reduce opioid consumption and improve patient satisfaction after major surgery. This prospective, observational study aims to compare the effectiveness and safety of two different regional anesthesia techniques, the Erector Spinae Plane Block (ESPB) and the Serratus Posterior Superior Intercostal Plane Block (SPSIPB), in managing postoperative pain in patients undergoing CABG via median sternotomy. Patients aged 18-80 years, classified as ASA II-III, who are scheduled for elective CABG will be included. The choice of block technique (ESPB or SPSIPB) will be determined by the operating anesthesiologist based on the visibility of anatomical structures (transverse processes) under ultrasound guidance. All patients will receive the same general anesthesia and be managed postoperatively with Intravenous Patient-Controlled Analgesia (PCA). The main goal is to determine which block provides optimal pain control, measured by the time to first rescue analgesia and pain scores (NRS) at various time points after extubation. Secondary outcomes include intraoperative opioid consumption, total PCA usage, extubation time, and the incidence of opioid-related side effects. The findings will help optimize pain protocols for cardiac surgery patients.