Volume 75, Issue 8 p. 1039-1049
Original Article
Free Access

Efficacy of quadruple treatment on different types of pre-operative anaemia: secondary analysis of a randomised controlled trial

J. Rössler

J. Rössler

Resident

Institute of Anesthesiology, University of Zurich and University Hospital Zurich, Zurich, Switzerland

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I. Hegemann

I. Hegemann

Consultant

Department of Medical Oncology and Haematology, University of Zurich and University Hospital Zurich, Zurich, Switzerland

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F. Schoenrath

F. Schoenrath

Consultant

Department of Cardiothoracic and Vascular Surgery, German Heart Centre Berlin, German Centre for Cardiovascular Research, Berlin, Germany

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B. Seifert

B. Seifert

Professor

Department of Biostatistics, Epidemiology, Biostatistics and Prevention Institute, University of Zurich, Switzerland

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A. Kaserer

A. Kaserer

Consultant

Institute of Anesthesiology, University of Zurich and University Hospital Zurich, Zurich, Switzerland

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G. H. Spahn

G. H. Spahn

Research Fellow

Institute of Anesthesiology, University of Zurich and University Hospital Zurich, Zurich, Switzerland

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V. Falk

V. Falk

Professor and Chairman/Professor

Department of Cardiothoracic and Vascular Surgery, German Heart Centre Berlin, German Centre for Cardiovascular Research, Berlin, Germany

Department of Cardiothoracic Surgery, Charité – Universitätsmedizin Berlin, Germany

Department of Health Science and Technology, Swiss Federal Institute of Technology, Zürich, Switzerland

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D. R. Spahn

Corresponding Author

D. R. Spahn

Professor and Chairman

Institute of Anesthesiology, University of Zurich and University Hospital Zurich, Zurich, Switzerland

Correspondence to: D. R. Spahn

Email: [email protected]

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First published: 27 April 2020
Citations: 12

Summary

In patients with pre-operative anaemia undergoing cardiac surgery, combination treatment with intravenous iron, subcutaneous erythropoietin alpha, vitamin B12 and oral folic acid reduces allogeneic blood product transfusions. It is unclear if certain types of anaemia particularly benefit from this treatment. We performed a post-hoc analysis of anaemic patients from a randomised trial on the ‘Effect of ultra-short-term treatment of patients with iron deficiency or anaemia undergoing cardiac surgery’. We used linear regression analyses to examine the efficacy of a combination anaemia treatment compared with placebo on the following deficiencies, each representing a part of the combination treatment: ferritin and transferrin saturation; endogenous erythropoietin; holotranscobalamine; and folic acid in erythrocytes. Efficacy was defined as change in reticulocyte count from baseline to the first, third and fifth postoperative days and represented erythropoietic activity in the immediate peri-operative recovery phase. In all 253 anaemic patients, iron deficiency was the most common cause of anaemia. Treatment significantly increased reticulocyte count in all regression analyses on postoperative days 1, 3 and 5 (all p < 0.001). Baseline ferritin and endogenous erythropoietin were negatively associated with change in reticulocyte count on postoperative day 5, with an unstandardised regression coefficient B of −0.08 (95%CI −0.14 to −0.02) and −0.14 (95%CI −0.23 to −0.06), respectively. Quadruple anaemia treatment was effective regardless of the cause of anaemia and its effect manifested early in the peri-operative recovery phase. The more pronounced a deficiency was, the stronger the subsequent boost to erythropoiesis may have been.

Introduction

Anaemia is a common comorbidity in patients undergoing cardiac surgery, with a prevalence of about 30–40% 1, 2. Pre-operative anaemia in cardiac surgery is independently associated with longer hospital stay and increased postoperative mortality 3, 4. Further, it leads to more red blood cell transfusions, which have been linked to adverse events and worse outcomes for patients 3. Major bleeding with anaemia and subsequent transfusions has been called “the deadly triad of cardiac surgery5. While tolerating anaemia with restrictive transfusion triggers may be preferable to red blood cell transfusions 6, the concept of patient blood management aims to treat anaemia and optimise a patient's red blood cell mass before surgery 7, 8. Patient blood management is a multidisciplinary, multimodal medical concept comprising a variety of measures, with the aim of improving clinical outcomes. Treatment of anaemia is one of the core measures and the specific therapy depends on the cause of the anaemia and its severity.

The most common cause of anaemia is iron deficiency 9, 10. Iron is a crucial component of erythropoiesis and reduction in stores results in iron deficiency anaemia 11, 12. Iron deficiency alone is associated with an increase in mortality in cardiac surgery 13. However, iron-restricted erythropoiesis can also result from impaired delivery of iron to erythroid precursors, which is common in anaemia of chronic disease 12, 14. Here the pro-inflammatory state upregulates acute phase proteins like hepcidin, which inhibits intestinal iron absorption, as well as iron transportation and cellular release 14, 15. Inflammation further leads to a down-regulation of erythropoietin receptor expression, reduces erythropoietin plasma levels and thereby reduces haematopoietic stimulation 14. Endogenous erythropoietin production also declines in advanced chronic kidney disease with subsequent renal anaemia.

Ideally, erythropoietin and parenteral iron should be administered several days before a planned intervention, since the earliest increase in the reticulocyte count occurs after 2–3 days 16, 17. In everyday clinical practice, however, patients who are due to have cardiac surgery are often evaluated on the day before surgery. In this setting, Spahn et al. showed that an ultra-short-term combination treatment with intravenous (i.v.) iron, subcutaneous erythropoietin alpha, vitamin B12 and oral folic acid reduced red blood cell and total allogeneic blood product transfusions in patients with pre-operative anaemia undergoing elective cardiac surgery 18. The effect of treatment on haemoglobin and reticulocyte count was observed on the first postoperative day. This immediate effect is of particular importance in peri-operative medicine, when aiming for optimal recovery after surgery. In this present study, we aimed to assess the efficacy of this quadruple combination treatment in different subtypes of anaemia among the anaemic participants in the study by Spahn et al. and, in particular, to investigate if a specific substrate or hormone deficiency would particularly benefit from substitution. We focused on the immediate course of erythropoiesis in the first five postoperative days.

Methods

The original trial by Spahn et al. was a single-centre, randomised, double-blind, parallel-group controlled study evaluating the efficacy of an ultra-short-term anaemia or iron deficiency treatment in patients undergoing elective cardiac surgery. The methods and main results have recently been reported 18. In brief, we enroled adults with planned coronary artery bypass grafting or valve surgery. Subjects having isolated and combined procedures were eligible. A detailed list of eligibility criteria is available as in the Supporting Information (Table S1). We gained written informed consent from all patients.

Subjects were randomly allocated and received the study intervention on the day of the pre-operative anaesthetic assessment, which usually took place the day before the procedure or, if the surgery was on a Monday, on the preceding Friday. Randomisation sequences were provided by the Clinical Trials Centre of the University of Zurich with a 1:1 allocation and were stratified by the following: type of surgery; primary vs. revision procedures; cardiopulmonary bypass technique; and presence of dual platelet inhibition. The intervention and placebo consisted of the following: ferric carboxymaltose 20 mg.kg−1 up to a maximum of 1000 mg (Ferinject®, Vifor (International) AG, St. Gallen, Switzerland) or normal saline 250 ml, given intravenously through an opaque infusion over 30 min; erythropoietin alpha 40,000U (Eprex®, Janssen-Cilag AG, Baar, Switzerland) or saline 1 ml given subcutaneously; vitamin B12 1 mg (Vitarubin®-superconc., Streuli Pharma AG, Uznach, Switzerland) or saline 1 ml given subcutaneously; and folic acid 5 mg (acidum folicum, Streuli Pharma AG, Uznach, Switzerland) or a placebo tablet given orally. Vital signs were assessed during and for 15 min after administration.

Furthermore, standard peri-operative management at the University Hospital of Zurich dictated pre-operative antibiotic prophylaxis, thrombosis prophylaxis with compression stockings and additional heparin depending on peri-operative mobility and strict adherence to hospital transfusion guidelines. Transfusion triggers were Hb 70–80 g.l−1 intra-operatively and in the ICU, or Hb 80 g.l−1 on the regular ward.

We recorded outcomes during the primary hospitalisation until postoperative day 5. We aimed to investigate the immediate effect of the combination treatment on erythropoiesis. Therefore, the primary efficacy outcome of this sub-study was the difference in reticulocyte count dependent on specific deficiencies from baseline to postoperative days 1, 3 and 5. Individual increases in reticulocyte count from baseline to each postoperative day were assessed for each participant in the treatment and the placebo group. As reticulocyte count represents erythropoietic activity, its change implied altered activity 19. Thus, we were able to determine the efficacy of the treatment and its effect on erythropoiesis, compared with the natural erythropoietic stimulation of postprocedural anaemia.

The prevalence of anaemia subtypes is shown as a baseline. In the original study, iron deficiency anaemia was defined as ferritin < 100 μg.l−1. In the current secondary analysis however, we defined iron deficiency anaemia as ferritin < 100 μg.l−1 or transferrin saturation < 20%. Renal anaemia was specified according to measured endogenous erythropoietin < 10 U.l−1. This is a more accurate determinant of renal anaemia, compared with the frequently used estimated glomerular filtration rate 20. Vitamin B12 deficiency was defined as holotranscobalamine < 50 pmol.l−1, and folate deficiency as folic acid in erythrocyte < 140 μg.l−1. We further analysed the association of the different baseline laboratory values. Laboratory analyses were conducted by the ISO/IEC 17025 accredited University Centre for Laboratory Medicine and Pathology of the University Hospital Zurich. Detailed information on specific assays is available as in the Supporting Infomation (Table S3).

Continuous variables were compared between treatment and placebo groups using the Mann-Whitney test. Categorical variables were compared using the Chi-square test. We used Spearman's rank correlation to analyse relations between baseline laboratory values. We performed linear regression to analyse the effect of treatment and baseline values on relative changes in reticulocytes from baseline to postoperative days 1, 3 and 5. For these analyses, variables were logarithmically transformed. Normal distribution of residuals was assessed visually using histograms, normal p-p plots, and Tukey-Anscombe plots. When we detected extreme residuals (absolute studentised residuals > 3), we performed a sensitivity analysis by excluding the corresponding observations. As no substantial changes were observed, we have reported the original analyses. We also analysed interactions between treatment and baseline laboratory values. We reported the results of the additive regression even if significant interactions were detected (Table 3). We included significant interactions in multivariate regression (Table 4). These interactions were centred at the mean of the corresponding baseline variable, such that the corresponding main effects were valid for mean baseline values.

For the regression analysis, ‘F(df1, df2)’ denoted the test statistic of the overall F-test with degrees of freedom df1 and df2. The ‘R2’ value represented the proportion of variance explained, ‘Beta’ the standardised and ‘B’ the unstandardised regression coefficient. Spearman's rank correlation was presented as ‘rs(n)’, where n indicated the number of pairs available.

We carried out all statistical analyses in IBM SPSS Statistics 25 (IBM Corp., NY, USA). We considered p values < 0.05 to be statistically significant with the exception of Spearman's rank correlations, where the level of significance was set to 0.01.

Results

We originally enroled 253 patients with anaemia (haemoglobin concentration (Hb) < 120 g.l−1 in women and Hb < 130 g.l−1 in men) and 252 patients with isolated iron deficiency (ferritin < 100 μg.l−1, no anaemia) at the University Hospital of Zurich from 9 January 2014 to 19 July 2017. In the current secondary analysis, we present data from the 253 patients with anaemia. Results from all 505 patients who received an intervention or placebo, as well as details of the study protocol, have been previously reported 18. We did not include nine subjects from our original sample of 253 patients from the analysis (Fig. 1).

Details are in the caption following the image
Consort flow diagram. ECMO, extra-corporeal membrane oxygenation.

In the anaemia group, baseline patient characteristics were well-matched. In addition, the distributions of the number of patients who met certain deficiency criteria were similar (Table 1). Iron deficiency was the most common cause of anaemia in the 244 patients with anaemia, occurring in 151 (62%) patients, followed by 59 (24%) patients with a deficiencies in endogenous erythropoietin and 58 (24%) patients with vitamin B12 deficiency; no deficiency in any of the five variables could be found in 43 (18%) patients (Table 1; Fig. 2).

Table 1. Characteristics of the patients in the treatment and placebo groups at baseline. Values are mean (SD) or number (proportion). There were no significant differences between the two groups
Treatment Placebo
n = 122 n = 122
Age; years 71.7 (8.7) 70.9 (10.3)
Female sex 37 (30%) 31 (25%)
Height; cm 168 (9) 168 (10)
Weight; kg 78.3 (15.4) 77.7 (15.4)
BMI; kg.m−2 27.7 (4.8) 27.4 (5.0)
EuroSCORE II 3.5 (4.4) 3.7 (4.1)
Haemoglobin; g.l−1 117 (10) 118 (9)
Reticulocyte count; g.l−1 59 (28) 56 (25)
Reticulocyte haemoglobin; pg 33 (3) 33 (4)
Ferritin; mg.l−1 231 (205) 248 (297)
Transferrin saturation; % 23 (18) 21 (11)
Creatinine; mmol.l−1 96 (28) 96 (31)
eGFR; ml.min−1 67 (20) 69 (22)
Endogenous erythropoietin; U.l−1 22 (24) 18 (14)
Holotranscobalamine; pmol.l−1 105 (70) 86 (52)
Folic acid in erythrocyte; g.l−1 526 (330) 516 (318)
C-reactive protein; mg.l−1 11 (16) 14 (27)
Deficiency criteria met; no. (%)
Ferritin < 100 μg.l−1 38 (31%) 37 (30%)
Transferrin saturation < 20% 63 (52%) 61 (50%)
Ferritin < 100 μg.l−1 or transferrin saturation < 20% 76 (63%) 75 (62%)
Endogenous erythropoietin < 10 U.l−1 33 (27%) 26 (21%)
Holotranscobalamine < 50 pmol.l−1 24 (20%) 34 (28%)
Folic acid in erythrocyte < 140 μg.l−1 0 0
C-reactive protein > 5 mg.l−1 54 (44%) 52 (43%)
  • eGFR, estimated glomerular filtration rate, calculated using the CKD-EPI (Chronic Kidney Disease Epidemiology Collaboration) formula.
Details are in the caption following the image
Area-proportional Venn diagram of anaemia-causing deficiencies. No deficiency was found in any of the five variables in 43 patients.

We assessed the relationship between different baseline laboratory values by Spearman's rank-order correlation. Baseline endogenous erythropoietin and reticulocyte count showed a moderate, statistically significant correlation, rs(241) = 0.30, p < 0.001. Furthermore, there were significant, weak negative correlations between baseline endogenous erythropoietin and ferritin, rs(242) = −0.23, p < 0.001; as well as transferrin saturation, rs(242) = 0.27, p < 0.001. Baseline holotranscobalamine showed a weak, positive correlation with folic acid in the erythrocytes, rs(241) = 0.29, p < 0.001 (Table 2).

Table 2. Spearman's correlation of patient baseline laboratory values
Ferritin Transferrin saturation Endogenous erythropoietin Folic acid in erythrocyte Holotranscobalamine Reticulocyte count
Ferritin 1
Transferrin saturation 0.27a 1
Endogenous erythropoietin −0.17a −0.23a 1
Folic acid in erythrocyte −0.10 0.04 0.11 1
Holotranscobalamine 0.09 0.01 −0.09 0.29a 1
Reticulocyte count 0.07 −0.01 0.30a 0.11 0.02 1
  • a Correlation significant at the 0.01 level (2-tailed).

We performed different additive linear regressions to predict the changes in reticulocyte count from baseline dependent on treatment and each baseline laboratory value (i.e. ferritin, transferrin saturation, endogenous erythropoietin, holotranscobalamine and folic acid in the erythrocytes).

The effect of treatment was significant in all five additive models on postoperative days 1, 3 and 5. The effect of baseline ferritin was significantly negatively associated with changes in reticulocyte count only on postoperative day 5. The interaction between the effect of baseline ferritin and the treatment effect was not significant on postoperative day 1, displayed a trend on postoperative day 3 and showed a significant interaction on postoperative day 5. Baseline endogenous erythropoietin was negatively associated with changes in reticulocyte count on postoperative day 5, where the effect also showed a trend interaction with treatment. Folic acid in the erythrocyte at baseline displayed a significant, negative association with changes in reticulocyte count on postoperative day 1, as did baseline holotranscobalamine on postoperative days 1 and 3 (Table 3; Fig. 3).

Table 3. Linear regression. The outcome variable is the change in reticulocytes from baseline to postoperative days 1, 3 and 5. Independent variables are treatment and baseline laboratory values
Postoperative day 1 Postoperative day 3 Postoperative day 5
B (95%CI) p value B (95%CI) p value B (95%CI) p value
Log (ferritin) −0.03 (−0.08 to 0.02) 0.185 −0.04 (−0.09 to 0.01) 0.085b −0.08 (−0.14 to −0.02) 0.011a
Effect of treatment 0.15 (0.11 to 0.19) < 0.001 0.22 (0.18 to 0.27) < 0.001 0.18 (0.13 to 0.23) < 0.001
Log (transferrin saturation) −0.08 (−0.16 to 0.01) 0.064 −0.04 (−0.13 to 0.05) 0.393 0.00 (−0.11 to 0.11) 0.944b
Effect of treatment 0.15 (0.11 to 0.19) < 0.001 0.22 (0.18 to 0.27) < 0.001 0.18 (0.13 to 0.23) < 0.001
Log(endogenous erythropoietin) −0.01 (−0.08 to 0.06) 0.728 −0.05 (−0.12 to 0.02) 0.179 −0.14 (−0.23 to −0.06) 0.001b
Effect of treatment 0.15 (0.11 to 0.19) < 0.001 0.23 (0.18 to 0.27) < 0.001 0.18 (0.13 to 0.23) < 0.001
Log (folic acid in erythrocyte) −0.11 (−0.20 to −0.01) 0.030 −0.10 (−0.20 to 0.01) 0.064 −0.06 (−0.19 to 0.06) 0.329
Effect of treatment 0.15 (0.11 to 0.19) < 0.001 0.23 (0.19 to 0.27) < 0.001 0.18 (0.13 to 0.23) 0.329
Log (holotranscobolamine) −0.10 (−0.17 to −0.03) 0.004 −0.09 (−0.17 to −0.02) 0.011 −0.08 (−0.17 to 0.00) 0.061
Effect of treatment 0.15 (0.11 to 0.19) < 0.001 0.23 (0.19 to 0.27) < 0.001 0.18 (0.13 to 0.24) < 0.001
  • a Significant interaction at the 0.05 level.
  • b Trend interaction at the 0.1 level.
Details are in the caption following the image
Scatterplots from additive linear regression. Change in reticulocyte count is assessed from baseline to postoperative days 1, 3 and 5 in association with baseline laboratory values in the treatment (red) and placebo (blue) group. The y-axis’ origin is marked with a black line.

The multiple regression models significantly predicted changes in reticulocyte count from baseline, on: postoperative day 1 (F(6, 208) = 10.4, p < 0.001, adj. R2=0.21); postoperative day 3 (F(7, 215) = 19.6, p < 0.001, adj. R2=0.37) and postoperative day 5 (F(7, 208) = 15.5, p < 0.001, adj. R2=0.32). In all three models the treatment variables contributed significantly to the prediction. Endogenous erythropoietin also did so on postoperative days 3 and 5, and holotranscobalamine on postoperative days 1 and 3. The interaction of baseline ferritin with the treatment variable also added statistically significantly to the prediction on postoperative days 3 and 5 (Table 4).

Table 4. Multivariate regression for change in reticulocytes from baseline to postoperative days 1, 3 and 5. The ‘Beta’ value represents the standardised and ‘B’ the unstandardised regression coefficient
  Beta B (95%CI) p value
Change in reticulocytes from baseline to postoperative day 1
Treatment 0.47 0.16 (0.12–0.20) < 0.001
log (ferritin) −0.03 −0.01 (−0.06 to 0.04) 0.617
log (transferrin saturation) −0.11 −0.08 (−0.18 to 0.01) 0.083
log (endogenous erythropoietin) −0.07 −0.04 (−0.11 to 0.03) 0.277
log (folic acid in erythrocyte) −0.08 −0.07 (−0.17 to 0.03) 0.192
log (holotranscobalamine) −0.15 −0.09 (−0.16 to −0.02) 0.019
Change in reticulocytes from baseline to postoperative day 3
 Treatment 0.60 0.23 (0.19–0.28) < 0.001
 log (ferritin) 0.02 0.01 (−0.06 to 0.08) 0.792
 Interaction of ferritin with treatment −0.16 −0.10 (−0.20 to 0.00) 0.043
 log (transferrin saturation) −0.04 −0.04 (−0.13 to 0.06) 0.462
 log (endogenous erythropoietin) −0.14 −0.10 (−0.18 to −0.02) 0.015
 log (folic acid in erythrocyte) −0.05 −0.05 (−0.16 to 0.06) 0.347
 log (holotranscobalamine) −0.13 −0.08 (−0.16 to −0.01) 0.031
Change in reticulocytes from baseline to postoperative day 5
 Treatment 0.45 0.19 (0.14–0.24) < 0.001
 log (ferritin) −0.01 0.00 (−0.09 to 0.08) 0.918
 Interaction of ferritin with treatment −0.28 −0.19 (−0.31 to −0.08) 0.001
 log (transferrin saturation) 0.02 0.02 (−0.10 to 0.13) 0.751
 log (endogenous erythropoietin) −0.30 −0.22 (−0.31 to −0.13) < 0.001
 log (folic acid in erythrocyte) −0.01 −0.01 (−0.13 to 0.12) 0.937
 log (holotranscobalamine) −0.12 −0.09 (−0.18 to 0.00) 0.054

Discussion

In this study, we analysed data from 244 anaemic patients from the previously published randomised trial by Spahn et al. and evaluated the efficacy of a combination anaemia treatment on different anaemia-causing substrate deficiencies. The original study showed that, in patients with pre-operative anaemia undergoing elective cardiac surgery, a combination treatment with i.v. iron, subcutaneous erythropoietin alpha, vitamin B12 and oral folic acid reduced allogeneic blood product transfusions 18. We have now demonstrated that the combination treatment was effective in increasing reticulocyte count regardless of the cause of anaemia. We analysed deficiencies in the baseline laboratory data reflecting the four components of the combination treatment to investigate different anaemia subtypes: ferritin and transferrin saturation for i.v. iron; endogenous erythropoietin for subcutaneous erythropoietin alpha; holotranscobalamine for oral vitamin B12; and folic acid in the erythrocytes for oral folic acid. In additive regression for each deficiency as well as in the multivariate model adjusting for all deficiencies, treatment was a significant predictor of reticulocyte increase on all postoperative days.

Iron deficiency anaemia was the most common type of anaemia in our sample, with around 62% of all anaemic patients suffering from either low ferritin or low transferrin saturation. Patients with low baseline ferritin in particular benefited from the combination treatment, as can be seen by the negative regression coefficient for ferritin and significant interaction with treatment (Table 3). This became more pronounced on postoperative days 3 and 5, although the effect of treatment was already apparent on postoperative day 1. Ferritin represents iron storage, where inadequate levels lead to iron deficiency anaemia. Iron deficiency itself, however, is already associated with worse peri-operative outcomes in cardiac surgery, regardless of the presence or absence of anaemia 13. We also observed a similar effect of treatment in patients with low transferrin saturation – a marker of inadequate iron supply, which also leads to iron deficiency 21. Our results support the fact that pre-operative replenishment of these diminished iron stores is advisable 21.

Even though all patients analysed were anaemic, endogenous erythropoietin levels were below 10 U.l−1 in 24%. In patients with anaemia, erythropoietin should increase as a natural homeostatic reaction. Inadequate erythropoietin production in response to stimuli leads to anaemia, as can be seen in renal anaemia or anaemia of chronic disease 14, 15, 22. Its supplementation has been shown to treat anaemia effectively 23, 24. The combination treatment showed efficacy, regardless of baseline erythropoietin level. The association with endogenous erythropoietin in the placebo group, however, is not as straightforward. In our cohort of anaemic patients, erythropoietin levels at baseline correlated with reticulocyte count at baseline. In the placebo group, patients with high baseline erythropoietin may not have shown an increase in reticulocytes postoperatively because erythropoietic stimulation was already present. However, as the patients were still anaemic, the stimulation was likely to have been inadequate. In these patients the combination treatment may have additionally boosted erythropoiesis.

Importantly, we chose to classify renal anaemia by measured erythropoietin levels, as the glomerular filtration rate is often an inadequate surrogate marker. Unless the glomerular filtration rate is very low, it correlates poorly with true endogenous erythropoietin 20. Thus, by analysing true endogenous erythropoietin levels, we have limited a significant potential source of bias. In clinical practice, the cost-benefit relationship of measuring endogenous erythropoietin or using glomerular filtration rate as a surrogate marker in diagnosing causes of anaemia diagnostics may be debated.

No patients suffered from folate deficiency. Our study was conducted in a single-centre in Switzerland, where folate levels are usually sufficient, even in the elderly general population 25. There are, however, many countries with restricted access to folate-rich balanced nutrition, and in addition there are circumstances that require higher folate levels (e.g. pregnancy) and folate supplementation has no relevant adverse effects 26. Vitamin B12 deficiency was more common, as 24% of patients had insufficient levels of holotranscobalamine. Here, although the effect of the combination treatment was also significant, there was a significant negative association between baseline holotranscobalamine and changes in reticulocytes on postoperative days 1 and 3, without an interaction with the treatment variable. This suggests that patients with significant vitamin B12 deficiency respond particularly well to the combination treatment.

The course of erythropoietic activity (i.e. change in reticulocyte count) over time highlights another important difference between the treatment and placebo groups (Fig. 3). In the treatment group, reticulocytes had already increased significantly by postoperative day 1. This implies an early boost to erythropoiesis 19. In the placebo group, however, there was almost no change in reticulocytes during this time, as well as on postoperative day 3. The reticulocyte count eventually also increased in the placebo group on postoperative day 5. This increase was an expected physiological response to peri-operative blood loss 27. As most blood is lost during the surgical procedure itself, this suggests a 5-day-long window with impaired haemopoietic recovery. The combination treatment, however, facilitated immediate haemopoietic recovery after surgery as represented by an increase in reticulocytes on postoperative day 1. This improved and earlier recovery time is of crucial importance to peri-operative medicine. Whereas the effects of iron and erythropoietin on reticulocytes generally only manifest themselves after 3–4 days and 2–3 days, respectively 16, 17, 21, 28, the combination treatment seemed to quicken the haemopoietic response. This accelerated response was proposed as the main mechanism of reduced blood transfusion in the original study 18.

Many forms of anaemia exist, each with its own cause. Different forms of anaemia can overlap and, therefore, classification can be difficult. Depending on the underlying cause, anaemia treatment ranges from taking supplements to undergoing medical procedures. Our approach to classifying anaemia according to the measured substrate deficiency is unique, and provides physicians in the peri-operative setting with a simplified treatment modality in a complex clinical environment. We have now demonstrated the efficiency of this treatment, independent of the underlying cause of anaemia. This is a very important finding in the peri-operative setting, as anaemia is independently associated with impaired peri-operative outcome 4 and should therefore be treated fast and reliably. Treatment of anaemia should not be restricted to cardiac surgery, but considered before any type of major surgery.

The management of pre-operative anaemia, especially with little time before a procedure with a high risk of major blood loss, can be challenging. As patients with profound iron deficiency particularly benefit from the combination treatment, our study supports the practice of measuring iron markers (i.e. ferritin and transferrin saturation) pre-operatively 21. However, as iron-replete patients show an accelerated haemopoietic response as well, the co-administration of parenteral iron irrespective of iron status may be considered individually in time-sensitive situations with potentially increased iron demand. Pre-operative measurement of endogenous erythropoietin might be more difficult, because low levels may be caused by an erythropoietin deficiency or by negative feedback from sufficient erythropoiesis 29. Erythropoietin supplementation offers promise for future anaemia treatment as part of comprehensive patient blood management. It is not licensed for use in patients with cardiovascular disease in some countries due to concerns about possible prothrombotic properties. However, a prospective randomised study in cardiac surgery as well as a meta-analysis of 18,917 critically ill patients found no such effects 30, 31. This is consistent with the results of our previously reported data, although the study was not powered for that particular outcome measure 18. Additional supplementation of vitamin B12 and folate has few side-effects and may be considered as an adjunct to anaemia therapy without precise laboratory measurements. As i.v. iron, subcutaneous erythropoietin alpha, vitamin B12 and oral folic acid were always co-administered in this study, it is not possible to say if a specific treatment was more effective than others. However, we can say conclusively that the combination treatment was effective regardless of deficiency, potentially because it was just that – a combination treatment.

The strengths of our study are that the data were derived from a prospective, randomised clinical trial. Data were pre-specified and 97% complete. However, our study has some limitations. Although we prospectively collected extensive laboratory data regarding different types of deficiencies, we only did so at baseline. The course of the substrate deficiencies evaluated would have given additional insights into the treatment response. Our follow-up of the course of reticulocytes was also limited to the fifth postoperative day. Further studies should examine the whole haemopoietic recovery process. Further limitations of the randomised controlled trial were outlined in the original paper 18.

In conclusion, combination treatment with i.v. iron, subcutaneous erythropoietin alpha, vitamin B12 and oral folic was effective regardless of the cause of anaemia, and especially in the early phases of peri-operative recovery. The more pronounced a deficiency was, the stronger the subsequent boost to erythropoiesis may have been when assessed by an increase in reticulocyte count.

Acknowledgements

IH has received speaker honorarium by Vifor Pharma Switzerland. FS has received honoraria, consultancy fees or travel support from Bayer, Medtronic GmbH, Biotronik SE & Co., Abbott GmbH & Co. KG, Sanofi S.A., Berlin Heart, and Novartis Pharma GmbH, Cardiorentis AG. VF has received educational grants (including travel support), fees for lectures and speeches, fees for professional consultation, and research and study funds from Medtronic GmbH, BIOTRONIK SE & Co., Abbott GmbH & Co. KG, Boston Scientific, Edwards Lifesciences, Berlin Heart, Novartis Pharma GmbH, JOTEC GmbH and Zurich Heart. DS's academic department is receiving grant support from the Swiss National Science Foundation; the Swiss Society of Anesthesiology and Reanimation; and the Swiss Foundation for Anesthesia Research, and Vifor SA. DS is co-chair of the ABC-Trauma Faculty, sponsored by unrestricted educational grants from: Novo Nordisk Health Care AG; CSL Behring GmbH; LFB Biomédicaments; and Octapharma AG. DS received honoraria/travel support for consulting or lecturing from: Danube University of Krems; US Department of Defense; European Society of Anesthesiology; Korean Society for Patient Blood Management; Korean Society of Anesthesiologists; Baxter AG; Baxter S.p.A.; Bayer AG, Bayer Pharma AG; B. Braun Melsungen AG; Boehringer Ingelheim GmbH; Bristol-Myers-Squibb; CSL Behring GmbH; Celgene International II Sàrl; Curacyte AG; Daiichi Sankyo AG; GlaxoSmithKline GmbH & Co. KG; Haemonetics; Instrumentation Laboratory (Werfen), USA LFB Biomédicaments; Merck Sharp & Dohme; Octapharma AG; Organon AG; PAION Deutschland GmbH; Pharmacosmos A/S; Photonics Healthcare B.V.; Pierre Fabre Pharma; Roche Diagnostics International Ltd; Roche Pharma AG; Sarstedt AG & Co.; Schering-Plough International; Tem International GmbH; Verum Diagnostica GmbH; Vifor Pharma; Vifor (International) AG; and Zuellig Pharma Holdings, Singapore.

The study was funded by the Swiss Foundation for Anaesthesia Research, a grant from Vifor Pharma and funds of the Institute of Anaesthesiology of the University Hospital of Zurich, Switzerland. The Swiss Foundation for Anaesthesia Research and Vifor Pharma had no role in the design of the study; the collection, analysis, and interpretation of data; the writing of this report or the decision to submit this article for publication. No other external funding or competing interests declared.