Early Postoperative Intravenous Iron Versus Oral Iron for the Treatment of Anemia Following Cardiac Surgery: A Randomized Controlled Trial

BACKGROUND: Postoperative anemia is a common complication after cardiac surgery, often persisting for months and substantially affecting patient recovery. Despite its prevalence, optimal treatment strategies are lacking. We aimed to evaluate whether early postoperative intravenous (IV) iron is more effective than daily oral iron in correcting anemia after cardiac surgery. METHODS: This single-center, pragmatic randomized controlled trial enrolled 110 cardiac surgery patients with moderate postoperative anemia (hemoglobin 8-11 g/dL). Participants were randomized 1:1 to receive either a single infusion of 20 mg/kg ferric derisomaltose on postoperative day 1 (IV iron group, n = 57) or 100 mg oral ferrous sulfate twice daily for 4 weeks (oral iron group, n = 53). All outcomes were assessed at 4 weeks postrandomization. The primary composite outcome aimed to measure treatment success, defined as the proportion of participants who were (a) no longer anemic (per World Health Organization criteria) and (b) neither had received allogeneic red blood cell (RBC) transfusions after randomization. Secondary end points included differences in hemoglobin levels, RBC transfusion rates, iron metrics, 6-minute walk test distances, hospital length of stay, and patient-reported outcomes. RESULTS: Primary outcome data were available for 53 participants in the IV iron group and 51 in the oral iron group. The proportion of participants who achieved the primary end point did not differ significantly between groups (28% vs 16%; risk difference 13%, 95% confidence interval CI, -3% to 28%; P = .121). No statistically significant differences were observed in anemia prevalence (66% vs 82%; P = .058) or RBC transfusion rates (17% vs 33%; P = .054). Mean hemoglobin levels (± standard deviation) were higher in the IV iron group (12.0 ± 1.1 g/dL vs 11.4 ± 1.3 g/dL; P = .013). None of the participants in the IV iron group had ferritin levels <100 µg/L, compared to 26% in the oral iron group (P < .001, accounting for 95% CI for 0 numerators). No significant differences were observed in the 6-minute walk test, hospital length of stay, or patient-reported outcomes. Notably, no serious adverse events related to ferric derisomaltose were reported. CONCLUSIONS: Early postoperative IV iron did not demonstrate superiority over oral iron for the primary outcome. However, secondary end points suggest it may improve hemoglobin levels and reduce the prevalence of postoperative iron deficiency. These findings warrant further investigation in larger trials to confirm the clinical effectiveness of early postoperative IV iron.