Introduction: Anaemia in patients having surgery is associated with worse postoperative outcomes. Management with intravenous iron is an attractive therapeutic option, however, pre-operative intravenous iron administration is challenging. Evidence from interventional trials suggests that the greatest benefit is after hospital discharge. As anaemia is common after surgery, this meta-analysis aimed to evaluate the efficacy of postoperative iron therapy to increase haemoglobin levels.

Methods: Relevant databases were searched from inception to 6 April 2023. Randomised controlled trials in adults undergoing elective surgery with postoperative anaemia, comparing intravenous or oral iron with control groups were included. The primary outcome was haemoglobin level at the end of study. Secondary outcomes included quality of life; blood transfusion requirements; incidence of adverse events; requirement for readmission; and mortality.

Results: Fifteen randomised controlled trials including 1865 patients were identified. Seven studies investigated intravenous iron, six investigated oral iron and two compared intravenous with oral iron. Intravenous iron increased postoperative haemoglobin levels compared with placebo or no intervention (mean difference 4.51 g.l^-1, 95%CI 2.63-6.38, I² = 0%, p < 0.01), while oral iron was ineffective (mean difference 0.61 g.l^-1, 95%CI -2.79-4.01, I² = 23%, p = 0.66). The subgroup analysis identified patients after orthopaedic surgery as the group with the greatest benefit (mean difference 3.63 g.l^-1, 95%CI 0.78-6.47, I² = 20%, p = 0.02). There were no significant differences in the secondary outcomes.

Discussion: Our meta-analysis of iron therapy for treating anaemia after major surgery found that intravenous iron administered within 30 days of surgery increased haemoglobin levels effectively, whereas oral iron showed no benefit.

Keywords: elective surgery; haemoglobin; intravenous iron; oral iron; postoperative anaemia.

© 2025 The Author(s). Anaesthesia published by John Wiley & Sons Ltd on behalf of Association of Anaesthetists.