Background-Hemodilutional anemia during cardiopulmonary bypass (CPB) is associated with increased mortality during coronary artery bypass graft (CABG) surgery. The impact of intraoperative red blood cell (RBC) transfusion to treat anemia during surgery is less understood. We examined the relationship between anemia during CPB, RBC transfusion, and risk of low-output heart failure (LOF). Methods and Results-Data were collected on 8004 isolated CABG patients in northern New England between 1996

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... d 2004. Patients were excluded if they experienced postoperative bleeding or received Ն3 units of transfused RBCs. LOF was defined as need for intraoperative or postoperative intra-aortic balloon pump, return to CPB, or Ն2 inotropes at 48 hours. Having a lower nadir HCT was also associated with an increased risk of developing LOF (adjusted odds ratio, 0.90; 95% CI, 0.82 to 0.92; Pϭ0.016), and that risk was further increased when patients received RBC transfusion. When adjusted for nadir hematocrit, exposure to RBC transfusion was a significant, independent predictor of LOF (adjusted odds ratio, 1.27; 95% CI, 1.00 to 1.61; Pϭ0.047). Conclusions-In this study, we observed that exposure to both hemodilutional anemia and RBC transfusion during surgery are associated with increased risk of LOF, defined as placement of an intraoperative or postoperative intra-aortic balloon pump, return to CPB after initial separation, or treatment with Ն2 inotropes at 48 hours postoperatively, after CABG. The risk of LOF is greater among patients exposed to intraoperative RBCs versus anemia alone. (Circulation. 2006; 114[suppl I]:I-43-I-48.)