Blood transfusion after on-pump coronary artery bypass grafting: focus on modifiable risk factors

OBJECTIVES: Perioperative transfusions are known to increase morbidity and mortality after coronary artery bypass grafting (CABG). The aims of the study were (1) to identify the clinical profile of the patient subset at highest risk from transfusion and (2) to disclose causative relationship and dose-dependency of transfusion on hospital mortality. METHODS: A prospective observational design was employed on a cohort of 1047 consecutive patients (median age 63.2 +/- 9.3, 18.8% female, 30.6% diabetics, 31.9% urgent/emergent, 15.3% with low preoperative left ventricular ejection fraction (LVEF)) who underwent on-pump isolated CABG between January 2004 and December 2007. Univariate and multivariate regression analysis and post-hoc risk stratification, by means of propensity scoring and binary segmentation, were adopted. RESULTS: The following independent risk factors were identified: age, body surface area (BSA), preoperative glomerular filtration rate, preoperative haemoglobin, surgical priority, length of cardiopulmonary bypass, intraoperative haemodilution and early postoperative blood loss. The patient population was stratified in quintiles of transfusional risk, by means of propensity scoring. As to modifiable risk factors, patients in the highest quintiles of risk were those with BSA (< 1.73, preoperative haemoglobin < 12 g/dl, intraoperative haemoglobin < 8.0 g/dl and those undergoing cardiopulmonary bypass > 90). Binary segmentation was performed to avoid any association between red cell transfusion and worse outcomes being causative and dose-dependent. A dose-dependent pattern was disclosed, with patients receiving > 5 units being at highest risk. CONCLUSIONS: High exposure to blood transfusions may be prevented by preoperative patient stratification and by the close tailoring of management strategies on planning and implementing surgical timing, as well as by cardiopulmonary bypass technique.