Association between non-anemic iron deficiency and outcomes following off-pump coronary artery bypass surgery: A retrospective analysis

Non-anemic iron deficiency (ID) may be harmful during cardiac surgery with cardiopulmonary bypass. However, its impact on off-pump coronary artery bypass (OPCAB) remains unclear. This study examined the association between non-anemic ID and outcomes following OPCAB. This single-center retrospective study included non-anemic patients who underwent OPCAB between November 2016 and May 2023. Patients were classified by preoperative ID status, defined as serum ferritin < 100 μg/L or 100-300 μg/L with C-reactive protein > 5 mg/L or transferrin saturation < 20%. The risk of primary outcome, defined as the composite of acute kidney injury, permanent stroke, deep sternal wound infection, hemostatic reoperation, prolonged mechanical ventilation, delirium, myocardial infarction, and 30-day mortality, was compared using multivariable logistic regression. Mediation analysis was performed to determine the indirect effects of non-anemic ID via perioperative red blood cell (RBC) transfusion. Of the 433 non-anemic patients, 229 (52.9%) had ID. The incidence of composite outcome was similar between patients with and without ID (30.1% vs. 22.5%, P = 0.075). ID was not significantly associated with the composite outcome, whereas perioperative transfusion (odds ratio: 2.101, 95% confidence interval [1.169-3.778], P = 0.013) showed significant associations. Perioperative RBC transfusion was more common in patients with ID (25.8% vs 10.8%, P < 0.001). Mediation analysis suggested that RBC transfusion partially mediated the effect of ID on the composite outcome. Preoperative ID was not associated with adverse outcomes in non-anemic patients who had undergone OPCAB. However, its indirect impact via RBC transfusion warrants further investigation.