POAM is a multicenter, randomized, controlled, internal pilot trial, using a conventional, parallel group, two-armed design at 3 cardiac surgery centres in Canada. The study is designed to assess the feasibility of a future, definitive RCT investigating whether, in patients with chronic iron-deficiency anemia undergoing cardiac surgery, IV iron therapy in the postoperative period (initiated shortly after surgery, and repeated at 42 days after surgery, if needed) improves clinical outcomes (days alive and out of hospital at 90 days after surgery; DAOH-90) relative to placebo.

Inclusion Criteria:

Patients who are undergoing any non-emergency open cardiac surgery and who meet all following criteria:

1. Age greater than 18 years old

2. Preoperative iron-deficiency with or without anemia (defined as Hb <130 g/L) with any one of:

   1. ferritin ≤100 μg/l; or
   2. ferritin ≤ 300 μg/L and transferrin saturation ≤ 20%; or
   3. reticulocyte Hb content < 29 pg, where available

Exclusion Criteria:

Patients who meet any of the following criteria are not eligible for the study:

1. specialized procedures (e.g., ventricular assist device insertion, thoracoabdominal aneurysm, complex adult congenital surgery and heart transplant)

2. established contraindications to IV iron:

   1. hypersensitivity to the iron product
   2. history of >2 food and/or drug allergic reactions (excluding drug intolerance)
   3. non-iron deficiency anemias such as myelodysplastic syndrome
   4. history of iron overload or disturbances in use of iron such as hemochromatosis or hemosiderosis
   5. decompensated liver cirrhosis (MELD ≥ 19) or active hepatitis
   6. active infection

3. preoperative unstable hemodynamics defined as the requirement for vasopressors or inotropes, or active bleeding (as noted in the clinical record and/or defined as a requirement for red blood cell transfusion for ongoing clinical bleeding)

4. refusal of blood products for religious or other reasons

5. known pregnancy

6. already enrolled in this trial

7. enrolment in another interventional trial which may impact anemia or transfusion management (for example, a trial of hemostatic therapies, such as tranexamic acid)

8. receipt of intravenous iron at any point in the 6 weeks prior to randomization

This is a blinded study, with patients randomized to receive ferric derisomaltose (Monoferric) or placebo. Given that the products have different physical appearances, an unblinded research pharmacist/delegated staff will prepare the IMP then blind the appearance of the IMP for both the intervention group and control group by covering the IV bag and tubing with opaque plastic. All other clinicians, research coordinators, outcome assessors, and patients will remain blinded by using a generic product label in the patient chart and/or the electronic product name (i.e., POAM study drug dose 1 and dose 2, rather than specifying type of product used).