Postoperative anemia is common in cardiac surgery with cardiopulmonary bypass. Iron deficiency delays the recovery from postoperative anemia and may negatively affect the postoperative trajectory of cardiac surgery patients. The objective of the study is to determine the effect of treatment of postoperative iron deficiency anemia with intravenous iron on disability 90 days after surgery. This will be evaluated in a randomized placebo-controlled double blind two-center trial in which 310 elective cardiac surgery patients will be included.

Rationale: Postoperative anemia is common in cardiac surgery with cardiopulmonary bypass. Iron deficiency delays the recovery from postoperative anemia and may negatively affect the postoperative trajectory of cardiac surgery patients.

Objective: To determine the effect of treatment of postoperative iron deficiency anemia (IDA) with intravenous iron (IVI) on disability 90 days after surgery.

Study design: Randomized placebo-controlled double blind two-center trial

Study population: 310 elderly patients (≥70 years) with moderate postoperative IDA on postoperative day (POD) 1 (hemoglobin (Hb) 85 - 110 g/L, ferritin concentration < 100 µg/L or iron saturation <20%) after uncomplicated elective cardiac surgery (aortic valve repair (AVR) and coronary artery bypass graft (CABG) surgery).

Intervention: Postoperative treatment with a single dose IVI (ferric derisomaltose, Monofer®, N = 155) compared to postoperative treatment with sodium chloride (NaCL) 0.9% (placebo, N = 155).

Main study endpoints: Primary endpoint is disability as measured by the 12- item World Health Organization Disability Assessment score 2.0 (WHODAS-12 at POD 90 after elective cardiac surgery. Secondary endpoints are change in patient reported outcome measures (PROMs) related to dyspnea (assessed with the Rose Dyspnea Score (RDS)) and to health-related quality of life (HRQL) (assessed with The Older Persons and Informal Caregivers-Short Form (TOPICS-SF) questionnaire) at POD 90, the number of postoperative red blood cell (RBC) transfusions, change in reticulocyte hemoglobin content (pg) from randomization to hospital discharge, Hb levels at discharge, hospital complications and days alive and out of hospital at 90 days. Lastly, the difference in functional outcomes (e.g. steep ramp or 6-minute walk test) and Hb value at POD 90 will be assessed as an exploratory endpoint.

Inclusion Criteria:

• Mentally competent with age ≥ 70 years
• Elective AVR or CABG surgery
• Expected uncomplicated postoperative trajectory, defined as:
• No inotropic agents or ventilation at time of final inclusion (POD 1)
• Expected discharge to general ward at POD 1
• Moderate postoperative IDA, defined as:
• Hb between 85 and 110 g/L and
• Ferritin <100 µg/L or
• Iron saturation (TSAT) < 20%

Exclusion Criteria:

• Medical history of iron overload/haemochromatosis
• Medical history of liver cirrhosis or ALT/AST value in blood serum triple of normal value (female patients: ALT >120, AST >105 U/L. Male patients: ALT>150, AST>135 U/L)
• Severe renal failure (eGFR<15ml/min/1.73m2)
• Recent treatment with IVI (<12 weeks prior)
• Serious or severe allergic reaction to IVI in medical history
• Severe asthma or eczema in medical history (atopic constitution)

Investigator and patient will be blinded for treatment allocation. As the IVI solution is brown and the placebo solution is colourless, the infusion bags and lines will be light-protected in order to prevent identification of the investigational product.