The Effect of Preoperative Anemia on Patients Undergoing Cardiac Surgery: A Propensity-Matched Analysis

It is unknown if anemia in the absence of transfusions is an independent risk factor for adverse outcomes in cardiac surgery, and if correction to higher hemoglobin targets impacts these outcomes. This is a retrospective review of 3848 cardiac surgery patients. Propensity matching was completed using 41 covariates. Intraoperative Anemia Analysis matched patients with or without anemia who did not receive intraoperative transfusions (n = 392/group), while Intraoperative Transfusion Analysis matched anemic patients treated conventionally with intraoperative transfusions to end cardiopulmonary bypass hemoglobin greater or less than 95 g/L (n = 261/group). Outcomes of death, renal failure, and 2 composite outcomes were assessed using paired analysis techniques. Study composite 1 consisted of prolonged ventilation, renal failure, myocardial infarction, stroke, or deep sternal wound infection, while composite 2 was the TRICS-III composite. In the Intraoperative Anemia Analysis, anemia was associated with mortality (P = 0.034), stroke (P = 0.021), renal failure (P = 0.015), and a significant increase in the composite measure (control 8.7% vs anemia 16.1%, P = 0.002). These findings were unchanged in patients who did not receive any postoperative transfusions. The Intraoperative Transfusion Analysis showed no difference in mortality or the composite outcome between groups. There was a significant increase in low cardiac output in the lower threshold group (P = 0.001). There were no differences in outcomes between those who did and did not receive postoperative transfusions (P > 0.05). Preoperative anemia in the absence of transfusions is a risk factor for morbidity and mortality after cardiac surgery, and there is no evidence that transfusion to higher end cardiopulmonary bypass hemoglobin levels impacted this risk.