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Pre‐operative optimisation with intravenous iron in cardiac surgery: some considerations

We thank Quarterman et al. for their recent article [1], which is in line with current scientific interest in patient blood management (PBM) programmes in cardiac surgery. Discussing their results, the authors mention that the pre-operative administration of intravenous iron does not reduce the rate of transfusion of red cells, surgical wound infections, re-operation for bleeding or in-hospital mortality. It should be noted that the introduction of PBM in cardiac surgery has shown a statistically significant reduction in the rates of transfusion of red cells, platelets and fresh frozen plasma, and length of hospital stay [2]. However, the haemoglobin (Hb) optimisation that forms part of the first pillar of PBM has been analysed in several prospective studies with small sample sizes that do not provide statistically significant conclusions on whether this strategy reduces transfusion requirements [3, 4], consistent with the results obtained byQuarterman et al. [1]. A detailed analysis of the study [1] reveals that the authors do not include a flowchart showing the total number of patients operated on during the 3-year study period or the number of patients that were eventually included in the statistical analysis. The authors do specify, however, that of the 314 patients treated with intravenous iron, 190 were included due to the type of surgery performed and the administration of intravenous iron in the 90 days before surgery. Only 39% of the patients treated with intravenous iron achieved Hb ≥ 130 g.l. The results show the transfusion rate was greater in anaemic patients that received intravenous iron compared with non-anaemic patients (60% vs. 22%, p < 0.001). However, the authors do not specify the difference in transfusion rates between treated anaemic patients who achieved Hb levels of 130 g.l and those that did not reach the target Hb. We believe this could generate a hidden bias with respect to the benefit of correcting anaemia with intravenous iron alone, without taking into account the erythropoietic stimulation factors recommended in different types of anaemia in the EACTS/EACTA guidelines on PBM for adult cardiac surgery [5]. On the other hand, we agree that the Hb cut-off value indicating the need to treat patients before cardiac surgery should be 130 g.l, regardless of sex. This is the value currently recommended by different expert guidelines [6] and international consensuses [7]. This is because it has been shown that Hb values between 120 and 129 g.l in women have been associated with an increase in the need for transfusion of red cells in cardiac surgery [8]. It should also be noted that 116 of the 190 anaemic patients included in the study group presented with Hb levels between 120 and 129 g.l, giving a mean increase in Hb of only 8 g.l. We agree with the authors’ suggestion of individualising target Hb, ferritin or transferrin saturation on the basis of factors such as the cause of anaemia, previous Hb or associatedmorbidity. Although it seems obvious that Hb optimisation will reduce transfusion requirements, the hypothesis is difficult to prove scientifically in isolation due to the limitations of the study, the lack of a standardised protocol for the administration of antifibrinolytic agents, or a transfusion protocol. The results are likely to be favourable only when all three pillars are combined in a studywith a large sample size [2].