Personalized Blood Transfusion Protocol for Cardiac Patients

This study compares two accepted ways of deciding when adults recovering from open-heart surgery should receive a blood transfusion in the intensive care unit. One approach gives a transfusion when the blood count (hemoglobin) falls below a fixed level that is the same for everyone. The other approach adds each patient's own physiology - such as oxygen levels and lactate - to help decide whether a transfusion is truly needed, within a safe range. The investigators want to learn whether the personalized approach is as safe as the standard approach for major outcomes after heart surgery, while reducing the amount of blood transfused. Participants may also choose to give blood and stool samples to a research biobank for future studies on recovery after cardiac surgery.