Anaemia in cardiac surgery – a retrospective review of a centre's experience with a pre‐operative intravenous iron clinic

Abstract

Summary Pre‐operative anaemia is associated with higher rates of transfusion and worse outcomes, including prolonged hospital stay, morbidity and mortality. Iron deficiency is associated with significantly lower haemoglobin levels throughout the peri‐operative period and more frequent blood transfusion. Correction of iron stores before surgery forms part of the first pillar of patient blood management. We established a pre‐operative anaemia clinic to aid identification and treatment of patients with iron deficiency anaemia scheduled for elective cardiac surgery. We present a retrospective observational review of our experience from January 2017 to December 2019. One‐hundred and ninety patients received treatment with intravenous iron, a median of 21 days before cardiac surgery. Of these, 179 had a formal laboratory haemoglobin level measured before surgery, demonstrating a median rise in haemoglobin of 8.0 g.l‐1. Patients treated with i.v. iron demonstrated a significantly higher incidence of transfusion (60%) compared with the non‐anaemic cohort (22%) during the same time period, p < 0.001. Significantly higher rates of new requirement for renal replacement therapy (6.7% vs. 0.6%, p < 0.001) and of stroke (3.7% vs. 1.2%, p = 0.010) were also seen in this group compared with those without anaemia, although there was no significant difference in in‐hospital mortality (1.6% vs. 0.8%, p = 0.230). In patients where the presenting haemoglobin was less than 130 g.l‐1, but there was no intervention or treatment, there was no difference in rates of transfusion or of complications compared with the anaemic group treated with iron. In patients with proven iron deficiency anaemia, supplementation with intravenous iron showed only a modest effect on haemoglobin and this group still had a significantly higher transfusion requirement than the non‐anaemic cohort. Supplementation with intravenous iron did not improve outcomes compared with patients with anaemia who did not receive intravenous iron and did not reduce peri‐operative risk to non‐anaemic levels. Questions remain regarding identification of patients who will receive most benefit, the use of concomitant treatment with other agents, and the optimum time frames for treatment in order to produce benefit in the real‐world setting.

Pre-operative Intravenous Iron to Optimise Patients Before Cardiac Surgery

“…The rise in Hb prior to surgery and percentage of patients who achieved non-anaemic status was smaller than that observed in the retrospective cardiac surgery studies [30,31]. There are a few possible reasons, the time before surgery was much shorter in the PREVENTT trial (median 15 days) and patients received a single dose of 1000 mg intravenous iron rather than a weight-appropriate dose.…”

“…The successful implementation of pre-operative anaemia pathways and treatment of IDA patients prior to surgery in NHS systems fraught with difficulties has to be commended [30,31]. In 2015, only 25% of 3,793 anaemic patients undergoing elective surgery in England, were treated for their anaemia pre-operatively and barriers to PBM strategies included time pressures and lack of staff education [47].…”

“…The work undertaken by Evans, Quarterman and Richards generates more questions for future research rather than answering the question -does pre-operative intravenous iron reduce the need for blood transfusion in elective surgery? In Evans' and Quarterman's studies, for those patients who achieved non-anaemic status by the time of surgery, intravenous iron was effective at reducing transfusion requirement, but likely the truly iron deficient patients achieved the best response [30,31,34].…”

“…Quarterman et al have also successfully implemented a pre-operative anaemia pathway and published a retrospective study of their findings [31]. This pathway shows similarities to the Cardiff Pathway in that anaemia is defined as Hb <130 mg/mL in both men and women and the same treatment administered i.e., a single dose of 20 mg/kg of intravenous iron.…”

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

“…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.…”