Preoperative anaemia is an independent predictor of 30-day mortality post-CABG and improves de predictive accuracy of EuroScore II
Authors: Rosler A , Constantin G , Nectoux P , Holz B S , Cardoso D , Letti E , Sales M C , Lucchese F A 
Published: October 2021

Abstract

Background
The impact of preoperative anaemia on the results of cardiovascular surgery has already been demonstrated by some authors. Some of the studies observed worse surgical results in anaemic patients, however, in others, no difference was observed. In addition, the impact that the inclusion of anaemia or haemoglobin would have as a predictor in a risk model such as EuroScore II is not yet known.

Purpose
To evaluate the impact of preoperative anaemia on 30-day mortality post-CRM and compare the predictive accuracy of EuroScore II with and without the inclusion of haemoglobin levels in the model.

Methods
Single center cohort with 2168 patients consecutively included between January 2010 and December 2020. All procedures were performed with cardiopulmonary bypass. 32 baseline and operative characteristics were assessed. The primary outcomes were 30-day mortality and the EuroScore II predictive accuracy. Patients were stratified into two groups according to anaemia status. WHO Classification – haemoglobin: men &lt;13 g/dL and women &lt;12 g/dL. No Anaemia Group (1301–60.1%) – Anaemia Group (867–39,9%). Univariate analysis was performed to compare the characteristics of the groups, the occurrence of death in 30 days and to verify variables associated with mortality. Logistic regression analyses were used to assess predictors of mortality and generate a set of probabilities for assessing the predictive accuracy of EuroScore II with and without the addition of haemoglobin in the model. The probabilities generated through the regressions were analysed by ROC curves, which in turn were compared using the DeLong test. The level of significance was 5% and the statistical analysis was performed using Python 3.0.

Results
The anaemic patients were older and had higher prevalence of conditions, such as: diabetes, renal impairment, smoking, HF class III or IV, RBC transfusion and highest mean of EuroScore II (p&lt;0.05 for all conditions). When comparing mortality in the groups, a significantly higher rate was observed in the anaemic group (2.2% vs 5.4%; p&lt;0.001). In view of the heterogeneity of the groups, an adjusted logistic regression model was applied. The results of the multivariate model demonstrated that preoperative anaemia was an independent risk predictor for the occurrence of death in 30 days after CABG (B: 0.597; SE: 0.27; Wald: 5.2; OR: 1.82; 95% CI 1.09–3.04; p=0.022). In addition, we were able to verify that the addition of preoperative haemoglobin to EuroScore II resulted in a significantly higher predictive accuracy when compared to the predictive accuracy of the isolated score (AUCs: 0,732 vs 0.709; p=0.032).

Conclusions
Preoperative anaemia was an independent risk predictor for the occurrence of death in 30 days after CABG. We were also able to verify that the addition of the preoperative haemoglobin levels to EuroScore II resulted in a significantly higher predictive accuracy, improving the performance of the surgical risk model.

Funding Acknowledgement
Type of funding sources: None. Figure 1. Haemoglobin vs 30-day mortalityFigure 2. Predictive accuracies – EuroScore II