Long-term Outcomes Sub-Study of Preoperative Combined Iron Therapy

The goal of this clinical trial is to learn if a combined iron supplementation regimen can reduce the need for blood transfusions in adults with iron-deficiency anemia undergoing major elective cardiac surgery. The trial will also look at whether this regimen is safe and well tolerated. The main questions it aims to answer are: Does the combined regimen lower the amount of allogeneic red blood cell transfusion needed during and after surgery? Are there any side effects or safety concerns associated with the regimen? Researchers will compare the combined iron supplementation (sucrose iron, erythropoietin, and vitamin C) to standard care to see if it helps reduce blood transfusions. Participants will: Receive either the combined regimen or standard care before surgery Undergo major elective cardiac surgery under general anesthesia Be monitored for blood transfusion needs and recovery up to 90 days after surgery