Nonanemic Iron Deficiency in Cardiac Surgery: A Retrospective Observational Study

•One-third of patients presenting for elective cardiac surgery have NAID.•NAID increases patient risk of becoming anemic by the time of surgery.•Allogeneic transfusion is more common in patients who are NAID versus NAIR.•A ferritin of ≥100 μg/L, rather than >30 μg/L, decreases allogeneic transfusion. Anemia and iron deficiency in patients having cardiac surgery increases their perioperative risk. Nonanemic iron deficiency (NAID) in this group is less well-described. We aimed to investigate the incidence and outcomes of patients with NAID undergoing cardiac surgery. Retrospective observational study. A single, tertiary referral center. Adult patients who were preassessed and underwent cardiac surgery during the study period had data collected. We enrolled 537 patients enrolled and divided them into 4 groups according to hemoglobin and ferritin: NAID, nonanemic iron replete, iron-deficiency anemia (IDA), and non–iron-deficiency anemia. This study was not interventional, but assessed the impact of anemia and iron deficiency on patient outcomes. The primary outcome was the incidence of NAID. Secondary outcomes included the number of patients who became anemic awaiting surgery, allogeneic transfusion burden, length of stay, postoperative complications, and death. 179 of 537 patients (33.3%) had NAID. Seventeen patients (9.5%) became anemic in the NAID group compared with 7 (3.3%) in the nonanemic iron replete group while awaiting for surgery (p = 0.02). Patients with NAID were more likely to receive allogeneic transfusions (33% vs 23%; p = 0.04) and had poorer recovery of hemoglobin at follow-up (13.2 ± 1.46 g/dL vs 13.9 ± 1.46 g/dL; p < 0.001). NAID is common and can lead to progression to anemia and increased transfusion. Iron replacement should be considered in patients with NAID in the preoperative setting. A prospective interventional trial is required to demonstrate the benefit of being iron replete.