Efficacy of intravenous iron supplementation in reducing transfusion risk following cardiac surgery: an updated meta-analysis of randomised controlled trials

Background: Previous meta-analyses of intravenous iron supplementation for reducing red blood cell (RBC) transfusion risk after cardiac surgery were inconclusive because of limited data. This updated meta-analysis incorporates recent evidence. Methods: Major databases were searched on May 2, 2024 for randomised controlled trials comparing the incidence of RBC transfusion between adult patients receiving intravenous iron supplementation and those receiving controls (i.e. oral iron or placebo) after cardiac surgery. The secondary outcomes included the number of RBC units transfused, postoperative haemoglobin levels, iron status, complications, and length of hospital stay. Trial sequential analysis was conducted to examine the robustness of evidence. Results: Fourteen randomised controlled trials including 2043 subjects were identified. Intravenous iron supplementation was found to reduce the RBC transfusion risk compared with controls (relative risk 0.77, 95% confidence interval [CI] 0.65–0.91, P=0.002, n=1955, I²=61%, certainty of evidence: moderate). The trial sequential analysis supported the robustness of the evidence. Furthermore, haemoglobin levels were higher in the intravenous iron supplementation group on postoperative days 4–10 (mean difference 0.17 g dl⁻¹, 95% CI 0.06–0.29, n=1989) and >21 days (mean difference 0.66 g/dl⁻¹, 95% CI 0.36–0.95, n=1008). Postoperative iron status also improved with Intravenous iron supplementation, particularly on postoperative days 4–10. There were no significant differences in other outcomes, including mortality. Conclusions: Intravenous iron supplementation can reduce RBC transfusion risk and improve postoperative haemoglobin level and iron status after cardiac surgery, supporting the implementation of Intravenous iron supplementation in perioperative blood management strategies. Systematic review protocol: CRD42024542206 (PROSPERO).