Operative risk and preoperative hematocrit in bypass graft surgery: Role of gender and blood transfusion.

Background: The association between lower preoperative hematocrit (Hct) and risk for morbidity/mortality after cardiac surgery is well established. We examined whether the impact of low preoperative Hct on outcome is modified by blood transfusion and operative risk in women and men undergoing nonemergent CABG surgery.

Methods: Patients having nonemergent, first-time, isolated CABG were included (N=2757). Logistic regressions assessed effect of hematocrit on major perioperative morbidity/mortality separately by males (n=2232) and females (n=525).

Results: Mean age was 63.2±10.1years, preoperative hematocrit was 38.9±4.8%, and STS risk score was 1.3±1.8%. Blood transfusion was more likely in female patients (26% vs. 12%, P<0.001). Multivariate analyses revealed that lower body mass index and lower preoperative hematocrit predicted transfusion in males and females, whereas older age (OR=1.03, P=0.017) also predicted transfusion in females. Major morbidity was also more likely in female patients (12% vs. 7%, P<0.001). In multivariate analyses, blood transfusion was the only predictive factor for major morbidity in females (OR=4.56, P<0.001). In males, higher body mass index (OR=1.07, P<0.001), lower hematocrit (OR=0.94, P=0.017), interaction of STS score with hematocrit (OR=1.02, P=0.045), and blood transfusion (OR=9.22, P<0.001) were significant predictors for major morbidity.

Conclusions: This study showed females were more likely to have blood transfusion and major morbidities after nonemergent CABG. Traditional factors that have been found to predict outcomes, such as hematocrit and STS risk, were related only to major morbidity in male patients. However, blood transfusion negatively impacted major outcome after nonemergent CABG surgery across all STS risk levels in both genders.