Perioperative nadir hemoglobin concentration and outcome in off-pump coronary artery bypass surgery ― A retrospective review

Background: Emerging evidence advocates the use of restrictive transfusion strategies at hemoglobin (Hb) levels of approximately 7–8 g/dL in cardiac surgeries using cardiopulmonary bypass. Yet, it is unclear whether the same thresholds can be applied to off-pump coronary bypass (OPCAB) that accompanies cardiac displacement and warm regional ischemia-reperfusion injury without the aid of a bypass machine. The aim of this study is to investigate the relationship between perioperative nadir Hb level and outcome following OPCAB. Methods and Results: Medical records of 1,360 patients were reviewed. Hb levels were serially assessed during and after surgery. The incidence of composite endpoints was 35%, which included myocardial infarction, stroke, acute kidney injury, sternal infection, reoperation, prolonged mechanical ventilation, and in-hospital mortality. The nadir Hb level was significantly lower in the morbidity group than in the non-morbidity group (8.1 [7.4−9.1] vs. 8.8 [7.9−9.8] g/dL, P<0.001). Multivariable logistic regression analysis revealed nadir Hb as an independent risk factor of adverse outcome (odds ratio: 0.878, 95% confidence intervals: 0.776−0.994, P=0.04), whereas preoperative anemia and perioperative transfusion were not. The critical value of Hb for predicting detrimental outcome was 8.05 g/dL. Conclusions: A significant association is found between perioperative nadir Hb and adverse outcome after OPCAB. Although preoperative anemia was not associated with poor prognosis per se, it was the only modifiable risk factor that was closely linked to nadir Hb.