The Effect of Preoperative Anemia on the Outcome After Coronary Surgery

Preoperative anemia is associated with increased morbidity and mortality after cardiac surgery. Since anemia is ultimately treated with red blood cell transfusions, we investigated the independent impact of anemia and transfusion on the outcome after coronary artery bypass grafting (CABG).

This study included 2761 consecutive patients who underwent isolated CABG. Anemia was defined as hemoglobin <12.0 g/dL in women and <13.0 g/dL in men. The main outcomes were 30-day and late mortality.

Patients with preoperative anemia had an increased prevalence of significant comorbidities and were associated with higher unadjusted risk of early and late adverse events. Propensity score matching resulted in 560 pairs with similar baseline and operative characteristics. In these matched pairs, anemic patients had an increased risk of late all-cause death (P = 0.047) and acute kidney injury (P < 0.0001). However, when adjusted for the severity of perioperative bleeding, preoperative anemia was not associated with an increased mortality risk (HR 1.10, 95% CI 0.86-1.39). Instead, this regression model showed that the European CABG registry (E-CABG) bleeding classification was an independent predictor of late mortality (compared to grade 0: grade 1, HR 1.93, 95% CI 1.37-2.73, grade 2, HR 2.19, 95% CI 1.50-3.18, grade 3, HR 5.59, 95% CI 3.34-9.39, P < 0.0001).

When adjusted for important baseline characteristics and operative factors as well as for the severity of perioperative bleeding and the amount of transfused blood products, anemia was not associated with an increased risk of adverse events. Increased exposure to blood transfusion among anemic patients may be the determinant of their poorer late survival.