This is a sub-study of the Preoperative Combined Iron Therapy trail in which some participants will be additionally randomized to combined iron supplementation or standarded treatment control to evaluate the impact on long-term outcomes.

Inclusion Criteria:

1. Participants must be at least 18 years of age.
2. Major cardiac surgery should encompass procedures such as coronary artery bypass grafting (CABG), valve surgery, or a combination of both.
3. Iron deficiency anemia is defined as having a ferritin level below 100 μg/L or a ferritin level below 300 μg/L accompanied by a transferrin saturation below 25%. Additionally, hemoglobin levels should range between 90 and 130 g/L for men or between 90 and 120 g/L for women.
4. The American Society of Anesthesiologists (ASA) classification should fall within Grade 1-3.
5. Prior to participation, the patient or their legal representative must provide informed consent.

Exclusion Criteria:

1. Contraindications for the administration of iron sucrose, ascorbic acid, or rHuEPO.
2. Presence of a temperature exceeding 37.5 °C or the utilization of non-prophylactic antibiotics.
3. Individuals with a weight equal to or less than 50kg.
4. Individuals with a family history of haemochromatosis or thalassaemia, or those with a transferrin saturation level exceeding 50% or a documented history of iron overload.
5. Presence of other known haematological disorders such as folic acid or vitamin B12 deficiency, haemolytic anaemia, haemoglobinopathies, iron granulocytic anaemia, G6PD deficiency, etc.
6. Requirement for emergency surgical intervention.
7. Severe hepatic or renal impairment, ALT >3 times the upper limit of normal value or AST >3 times the upper limit of normal value, creatinine >1.5 times the upper limit of normal value
8. Pregnant or lactating women
9. history of blood transfusion, intravenous iron or ascorbic acid use within 12 weeks prior to surgery
10. Acute blood loss, gastrointestinal bleeding, etc. in the preoperative period.

Blinding was maintained for outcome assessors, extracorporeal circulation staff, and all investigators not directly involved in the treatment process.