Intravenous iron therapy for patients with preoperative iron deficiency or anaemia undergoing cardiac surgery reduces blood transfusions: a systematic review and meta-analysis

OBJECTIVES The benefits of preoperative intravenous (IV) iron treatment in cardiac surgery patients with preoperative anaemia or iron deficiency have not been well-established. We performed a systematic review and meta-analysis to determine the effects of treating preoperative anaemia or iron deficiency with IV iron in adult cardiac surgery patients. METHODS We searched Cochrane Central Register of Controlled Trials, Medical Literature Analysis and Retrieval Systems Online and Excerpta Medica Database for randomized controlled trials (RCTs) and observational studies comparing IV iron to oral iron or no iron. We performed title and abstract, full-text screening, data extraction and risk of bias assessment independently and in duplicate. We pooled data using a random effects model and evaluated the overall quality of evidence. RESULTS We identified 4 RCTs and 7 observational studies. Pooled data from observational studies suggested a benefit of IV iron compared to no iron on mortality [relative risk 0.39, 95% confidence interval (CI) 0.23–0.65; P < 0.001, very low quality], units transfused per patient (mean difference −1.22, 95% CI −1.85 to −0.60; P < 0.001, very low quality), renal injury (relative risk 0.50, 95% CI 0.36–0.69; P < 0.001, very low quality) and hospital length of stay (mean difference −4.24 days, 95% CI −6.86 to −1.63; P = 0.001, very low quality). Pooled data from RCTs demonstrated a reduction in the number of patients transfused with IV iron compared to oral or no iron (relative risk 0.81, 95% CI 0.70–0.94; P = 0.005, moderate quality). The pooled estimates of effect from RCTs for mortality, hospital length of stay, units transfused per patient and renal injury were consistent in direction with observational studies. CONCLUSIONS This meta-analysis suggests that IV iron improves postoperative morbidity in adult cardiac surgery patients with preoperative anaemia or iron deficiency. A large, rigorous, placebo-controlled, double-blinded, multicentre trial is needed to clarify the role of IV iron in this patient population. Clinical trial registration International prospective register of systematic reviews ID Number CRD42019122844