Transfusion and bleeding in coronary artery bypass grafting: an on-pump versus off-pump comparison

Blood transfusion rates in coronary artery bypass grafting (CABG) surgery using cardiopulmonary bypass (CPB) are typically higher compared with off-pump CABG (OPCAB). However, few studies have specifically examined intraoperative hemodilution as a contributing factor. The aim of this retrospective review was to compare the effect of using CPB or OPCAB on red blood cell (RBC) transfusion and postoperative bleeding. The lowest intraoperative hematocrit (Hct) was used as marker of intraoperative hemodilution. We reviewed the perioperative data of all isolated CABG patients at a metropolitan hospital from January 2003 to June 2005. Stepwise regression analyses were performed to determine whether CPB was an independent predictor of RBC transfusion, reoperation for bleeding, or postoperative chest drainage. Of a total of 1043 patients, there were 433 CPB and 610 off-pump cases. CPB use was not significantly related to increased RBC transfusions (odds ratio [OR], 0.98; 95% confidence interval [CI], 0.63-1.52; p = .921) and was associated with a lower incidence of reoperations for bleeding (OR, 0.4; 95% CI, 0.2-0.8; p = .009). There was less chest drainage over the first 12 hours in patients undergoing CPB (p < .0001); however, total postoperative chest drainage was not significantly related to operative procedure (p = .122). The lowest documented intraoperative Hct was a significant factor in RBC transfusions (OR, 0.89; p < .0001), an increased reoperation rate for bleeding (OR, 0.9; p = .001) and more postoperative chest drainage (log10-transformed: at 12 hours, b = -0.009, p < .0001; total, b = -0.006, p < .0001). CPB is not an independent risk factor in the incidence of RBC transfusions and is not associated with increased postoperative bleeding for isolated CABG. However, intraoperative hemodilution is an independent risk factor, with a lower intraoperative Hct associated with more RBC transfusions, increased reoperations for bleeding, and increased postoperative chest drainage. Addressing intraoperative hemodilution is important in minimizing CPB-associated morbidities.