Preoperative hematocrit as a predictor of perioperative morbidities following nonemergent coronary artery bypass surgery.

BACKGROUND: Preoperative hematocrit (HCT) has predicted inferior outcome following cardiac surgery. However, the potential for preoperative HCT to be a marker for sicker patients was not well explored. This study examined the impact of HCT on outcome following nonemergent coronary artery bypass grafting (CABG) and whether the association is modified by operative risk or intraoperative blood transfusion. METHODS: Nonemergent isolated CABG surgery patients were included (N = 2306). Logistic regressions were conducted to assess the effect of HCT on major perioperative morbidities. Separate analyses were conducted on tertiles of STS score (<0.55%, n = 768; 0.55% to 1.15%, n = 771; >1.15%, n = 767). RESULTS: Mean age was 63.1 ± 10.1, preoperative HCT was 38.9 ± 4.8, and STS score was 1.4 ± 2.0% (median = 0.79%). In univariate (OR = 0.89, p < 0.001) and multivariate (OR = 0.93, p < 0.001) analyses, lower HCT predicted major morbidity. Lower HCT predicted major morbidity only in the highest risk tertile (OR = 0.93, p < 0.001) and the same result was found after multivariate adjustment (OR = 0.92, p < 0.001). Following inclusion of intraoperative transfusion in a multivariate model, preoperative HCT remained an independent predictor for major morbidity (OR = 0.95, p = 0.01), while transfusion was also a strong predictor (OR = 4.86, p < 0.001). Addition of transfusion to multivariate models by STS risk tertiles revealed preoperative HCT remained predictive only in the highest risk group (OR = 0.95, p = 0.03) while transfusion was a strong predictor in all three risk tertiles (OR = 3.97 to 10.36; p-values < 0.001). CONCLUSIONS: Lower preoperative HCT was associated with higher odds for perioperative morbidity in nonemergent CABG patients with higher STS risk. Additionally, intraoperative blood transfusion negatively impacted all STS risk groups. Preoperative strategies to mitigate anemia may reduce transfusions and improve outcome in CABG patients.