Preoperative Anaemia Indeed Increases Operative Mortality after Isolated CABG: a Sharpened Risk Factor Identification with Sequential Analysis

Objective:

• To demonstrate that the negative impact of preoperative anaemia on in-hospital survival after CABG is real and more rapidly detected by sequential analysis than by a conventional odd-ratio analysis.

Methods:

• We studied a consecutive series of 1282 patients who underwent isolated CABG surgery in our department between 2008 and 2017 and analyzed in-hospital outcome taking into account preoperative status including variables for EuroScore and serum hemoglobin level. We categorized patients into two groups according to preoperative anaemia (WHO definition). The effect of preoperative anaemia on in-hospital mortality was analyzed with CUSUMs of failures assuming a postoperative mortality between 2.5 and 4% (H0 for sequential analysis) as well as with the method of Odd-ratios.

Results:

• Preoperative anaemia was diagnosed in 393 patients (conventional sex ratio 391:100). In hospital mortality was below 3% for patients with a preoperative serum hemoglobin level above 12g/dL and above 6% in the other instance. H0 was confirmed for non-preoperative anaemic patients (lower alarm line crossed for the 609th patient). Conversely H1 was confirmed for preoperative anaemic patients (higher alarm line crossed for the 266th patient). The Odd-Ratio for in-hospital mortality in preoperative anaemic patients was 1,93 (p=0.03) in this series however underpowered for a type II risk of 0.2.

Conclusion:

• Preoperative anaemia is a common feature in coronary surgery and indeed increases operative mortality after isolated CABG. The number of patients needed to be included in the study is lower when results are monitored with sequential analysis which therefore sharpens identification of risk-factors for in-hospital mortality. Our results confirm the importance of preoperative anaemia as a potentially modifiable risk factor in isolated coronary surgery.