Serratus Posterior Superior Plane Block for Postoperative Pain in Cardiac Surgery

Inclusion Criteria: * Patients aged 18-80 undergoing elective on-pump open-heart surgery via median sternotomy. * American Society of Anesthesiologists (ASA) classification II-III patients. * Patients who can use PCA. * Patients who will sign the informed consent form. Exclusion Criteria: * History of opioid use for more than four weeks * Chronic pain syndromes * Patients with a history of local anesthetic or opioid allergy, hypersensitivity * Alcohol and drug addiction * Conditions where regional anesthesia is contraindicated * Failure in the dermatomal examination performed after the block * Emergency surgeries and redo surgeries. * Individuals with obstructive sleep apnea. * Left ventricular ejection fraction less than 30%. * Patients with severe psychiatric illnesses (such as psychosis, dementia) that limit cooperation with verbal numerical pain scales. * Pregnant and breastfeeding patients. * Hematological disorders. * Significant impairment in the function of a major organ (e.g., severe hepatic or renal disease). • Patients who cannot be extubated within the first 6 hours postoperatively.