The impact of timing of intravenous iron supplementation on preoperative haemoglobin in patients scheduled for major surgery

Anaemia is frequent and an independent risk factor for morbidity and mortality in patients undergoing surgery. Iron deficiency (ID) is the main cause for anaemia and can be corrected by intravenous (IV) iron. The aim of this study was to investigate the timing of preoperative IV iron supplementation on preoperative haemoglobin (Hb) level. Surgical patients were screened for the presence of anaemia and ID from November 2015 to January 2020. In case of ID or iron deficiency anaemia (IDA), patients received IV iron supplementation. The timing of IV iron supplementation on preoperative Hb level was analysed by days and time frames clustered by 5 days before surgery. In total, 404 patients with IV iron supplementation were analysed. In all patients, IV iron was administered with a median (interquartile range [IQR]) of 3.0 (1.0; 9.0) days before surgery. Preoperative Hb level increased steadily starting from 6 days (0.13 [±1.2] g/dL) until 16 days before surgery (1.75 [±1.1] g/dL). Group comparison revealed a median preoperative Hb change of -0.2 (-0.5; 0.2) g/dL for days 1-5, 0.2 (0.0; 0.7) g/dL for days 6-10, 0.7 (0.2; 1.1) g/dL for days 11-15, 0.7 (0.2; 1.8) g/dL for days 16-20, 0.9 (0.3; 1.7) g/dL for days 21-25, 1.5 (0.4; 2.6) g/dL for days 26-30, and 0.6 (0.0; 1.7) g/dL for >31 days. Three patients received multiple administrations of IV iron which resulted in an increase in Hb of >4 g/dL. Supplementation of IV iron to increase Hb concentration preoperatively may be most effective if administered at least ten days before surgery.