Preoperative Hematocrit Is a Powerful Predictor of Adverse Outcomes in Coronary Artery Bypass Graft Surgery: A Report From The Society of Thoracic Surgeons Adult Cardiac Surgery Database

BACKGROUND: Small series have identified a relationship between preoperative hematocrit (HCT) and outcomes in coronary artery bypass graft (CABG) surgery. The Society of Thoracic Surgeons (STS) Adult Cardiac Surgery Database (ACSD) began collecting preoperative HCT data in 2008. In this study, analyses were performed to determine the impact of preoperative HCT on perioperative morbidity and mortality among patients undergoing isolated CABG.

METHODS:

Data were collected on 182,599 patients who underwent primary isolated on-pump CABG between 2008 and 2009 and were included in the STS ACSD. Data were included only from centers that performed more than 100 on-pump cases per year during the period of study. Dialysis patients as well as those with previous cardiovascular operations or missing data for HCT were excluded. We then performed multivariable analysis using the 2008 STS CABG risk model as a guide, including HCT as a predictor. Logistic regression was performed for operative mortality and other adverse outcomes.

RESULTS:

Overall operative mortality was 1.6% (3,005 of 182,599). Compared with patients with anemia (HCT <33%), patients with HCT of at least 42% had lower mortality (1.1% versus 3.4%; p < 0.0001) and lower rates of renal failure (2.0% versus 7.8%; p < 0.0001), stroke (0.9% versus 1.8%; p < 0.0001), prolonged ventilation (8.4% versus 17.5%; p < 0.0001), and deep sternal wound infection (0.3% versus 0.6%; p < 0.0001). In adjusted analyses, each 5-point decrease in preoperative HCT was associated with an 8% higher odds of death (odds ratio, 1.08; p = 0.0003), a 22% increase in the odds of postoperative renal failure (odds ratio, 1.22; p < 0.0001), and a 10% increase in the risk of deep sternal wound infection (odds ratio, 1.10; p < 0.01). Similar results were observed among patients (n = 74,292) undergoing elective CABG. The percentage of patients receiving perioperative blood transfusion decreased from 88.5% in the anemic group (HCT <33%) to 32.5% in patients with HCT of at least 42% (p < 0.0001).

CONCLUSIONS:

Preoperative HCT is a powerful independent predictor of perioperative mortality as well as renal failure and deep sternal wound infection in patients undergoing isolated primary CABG operations. These findings should prompt investigation of strategies to increase preoperative HCT.