Personalized Blood Transfusion Protocol for Cardiac Patients

Inclusion Criteria: * Adults 18 years or older scheduled for cardiac surgery using the heart-lung machine (cardiopulmonary bypass), such as bypass, valve, or combined procedures * Moderate-to-high surgical risk (e.g., EuroSCORE II ≥ 3% or equivalent) * Allogeneic red blood cell transfusion is considered likely * Able to provide informed consent and understand randomization to different transfusion thresholds * Willing to receive blood products and follow study transfusion thresholds from anesthesia induction until hospital discharge or day 28, whichever comes first Exclusion Criteria: * Refusal of or contraindication to allogeneic blood (e.g., Jehovah's Witness or formal directive against transfusion), or enrollment in a preoperative autologous donation program * Emergency or salvage procedures where protocol triggers are impractical (e.g., active arrest, aortic dissection with collapse) * Heart transplantation, durable ventricular assist device implantation, or surgery solely for VAD insertion * Off-pump bypass or other procedures not using cardiopulmonary bypass * Severe preoperative anemia (e.g., hemoglobin \< 8 g/dL) or chronic transfusion-dependent anemia * Conditions preventing protocol adherence (e.g., anticipated massive hemorrhage, known bleeding disorder, very low platelets, uninterruptible dual antiplatelet/anticoagulant therapy) * Chronic dialysis dependence or established end-stage renal disease (eGFR \< 15 mL/min/1.73m² or on maintenance renal replacement the…