SPIP vs ESP Block in Cardiac Surgery

Inclusion Criteria: * written informed consent * age 18 to 80 years * American Society of Anesthesiologists (ASA) physical status II-IV * Scheduled for first-time on-pump cardiac surgery through a median sternotomy, including coronary artery bypass grafting, valve repair or replacement, or another open cardiac procedure requiring sternotomy * Ability to understand postoperative pain and recovery assessments and to use an intravenous patient-controlled analgesia device. Exclusion Criteria: * Emergency surgery. * Previous median sternotomy. * Minimally invasive cardiac surgery without median sternotomy. * Known allergy or hypersensitivity to bupivacaine, morphine, paracetamol, ondansetron or another protocol medication. * Chronic opioid use, defined as continuous opioid treatment for at least 30 days at a daily oral morphine equivalent dose of 15 mg or more. * Alcohol or substance use disorder that, in the investigator's judgment, may affect adherence or outcome assessment. * Clinically significant hepatic dysfunction, defined as alanine aminotransferase or aspartate aminotransferase greater than twice the upper limit of normal. * Clinically significant renal dysfunction, defined as serum creatinine greater than twice the upper limit of normal. * Coagulation disorder or antithrombotic treatment that precludes safe block performance according to current institutional guidance. * Infection at a planned needle insertion site. * Severe psychiatric illness, cognitive impairment or communication difficulty preventing valid postoperative assessment. * Pregnancy or breastfeeding. * Body mass index greater than 40 kg/m². * Prolonged postoperative mechanical ventilation, defined as failure to achieve extubation within 8 hours after surgery. * Refusal to participate.