We thank Dr. Cuenca et al.  for their comments on our article about the efficacy of intravenous iron sucrose in the treatment of preoperative anemia in patients undergoing major orthopedic surgery,1and are glad to answer their comments.

We used the World Health Organization definition for anemia as inclusion criteria for our study and reviewed the literature concerning iron deficiency anemia. Interestingly, there is not one universally applicable definition for iron deficiency anemia. Recent papers by Thomas et al.  2–4indicate that the traditional definition for iron deficiency anemia with mean corpuscular volume < 80 fl or a ferritin level < 15–30 μg/l or transferrin saturation < 15% does not take into account the effect of a possible inflammatory state. Therefore, we measured C-reactive protein as well as leukocyte count for every patient at the moment of inclusion. Leukocyte counts ranged from 4,300 to 9,500/μl (reference values being 4,000–10,000/μl in our laboratory) and C-reactive protein ranged from 0 to 12 mg/l (reference, < 7 mg/l). By measuring the soluble transferrin receptor and calculating the ferritin index (soluble transferrin receptor/log ferritin ratio), and using different cutoff values depending on the measured C-reactive protein, we were able to select iron deficiency anemia.

The theoretical total iron deficit for a target hemoglobin of 15 g/dl was calculated for every patient. Total iron deficit was 1,088 ± 239 mg, indicating that the administered dose of 900 mg was indeed slightly less than theoretically needed. Therefore, higher doses may be used in future studies. The perioperative blood loss was not considered in the calculation of the total iron dose, because only the preoperative hemoglobin increase was assessed.

We compared the transfusion outcome of our group of patients with the study of Cuenca et al.  5and found astonishing similarities in both groups treated with intravenous iron. Comparing our results with a combined erythropoietin and intravenous iron treatment6or a treatment with oral iron7appears inadequate.8 

The question on repeated low dose intravenous iron was assessed in patients on hemodialysis.9Schiesser et al.  9showed that it is possible to maintain the iron status and the hemoglobin level with low dose intravenous iron. However, such a regimen did not allow improving the hemoglobin level. Nevertheless, in orthopedic surgery a direct comparison between repeated low dose versus  high dose intravenous iron regimen may be the subject of a future study.

In conclusion, intravenous iron should be considered for the relative rapid correction of iron deficiency anemia. However, the real benefit of such a regimen in the context of (orthopedic) surgery needs to be proven in a future prospective, randomized, placebo-controlled trial.

*University Hospital and University of Zurich, Zurich, Switzerland. oliver.theusinger@usz.ch

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