Is female sex an independent risk factor for perioperative transfusion in coronary artery bypass graft surgery?

BACKGROUND

Perioperative red blood cell transfusion is a risk factor for postoperative mortality and morbidity in coronary artery bypass grafting (CABG). Females have a higher risk of red blood cell transfusion, but few previous studies have accounted for preoperative hematocrit and female sex together as risk factors for red blood cell transfusion. We evaluated female sex as an independent risk factor for red blood cell transfusion in CABG, while accounting for hematocrit.

STUDY DESIGN

A cardiac surgery database was reviewed for isolated, primary, first-time CABG operations from a single center from January 2005 to June 2009. Demographic and clinical variables were evaluated as risk factors of red blood cell transfusion using univariate (Student t-test and chi-square test) and multivariate (logistic regression) analyses.

RESULTS

Of 2,107 patients (ALL-patients) reviewed, 640 had known hematocrit (KNOWN-Hct). Women had lower hematocrit (35.77% ± 4.07% vs 40.06% ± 4.79% for men). On multivariate analysis of ALL-patients, older age, smaller body surface area, and female sex were risk factors; higher ejection fraction and off-pump surgery were associated with less red blood cell transfusion. On multivariate analysis of KNOWN-Hct, older age, lower hematocrit, smaller body surface area, and lower ejection fraction were risk factors of red blood cell transfusion and sex was not a significant risk factor in this group.

CONCLUSIONS

Female sex is not an independent risk factor for red blood cell transfusion in CABG when preoperative hematocrit is included as a covariate in a multivariable model. A lower hematocrit could explain some of the sex-specific disparities in outcomes after CABG and should be included in future analyses.