Preoperative Hemoglobin and Outcomes in Patients with CKD Undergoing Cardiac Surgery

Abstract

BACKGROUND AND OBJECTIVES: Preoperative anemia adversely affects outcomes of cardiothoracic surgery. However, in patients with CKD, treating anemia to a target of normal hemoglobin has been associated with increased risk of adverse cardiac and cerebrovascular events. We investigated the association between preoperative hemoglobin and outcomes of cardiac surgery in patients with CKD and assessed whether there was a level of preoperative hemoglobin below which the incidence of adverse surgical outcomes increases. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: This prospective observational study included adult patients with CKD stages 3-5 (eGFR<60 ml/min per 1.73 m(2)) undergoing cardiac surgery from February 2000 to January 2010. Patients were classified into four groups stratified by preoperative hemoglobin level: <10, 10-11.9, 12-13.9, and ≥ 14 g/dl. The outcomes were postoperative AKI requiring dialysis, sepsis, cerebrovascular accident, and mortality. RESULTS: In total, 788 patients with a mean eGFR of 43.5 ± 3.7 ml/min per 1.73 m(2) were evaluated, of whom 22.5% had preoperative hemoglobin within the normal range (men: 14-18 g/dl; women: 12-16 g/dl). Univariate analysis revealed an inverse relationship between the incidence of all adverse postoperative outcomes and hemoglobin level. Using hemoglobin as a continuous variable, multivariate logistic regression analysis showed a proportionally greater frequency of all adverse postoperative outcomes per 1-g/dl decrement of preoperative hemoglobin (mortality: odds ratio, 1.38; 95% confidence interval, 1.23 to 1.57; P<0.001; sepsis: odds ratio, 1.31; 95% confidence interval, 1.14 to 1.49; P<0.001; cerebrovascular accident: odds ratio, 1.31; 95% confidence interval, 1.00 to 1.67; P=0.03; postoperative hemodialysis: odds ratio, 1.38; 95% confidence interval, 1.11 to 1.75; P<0.01). Moreover, preoperative hemoglobin<12 g/dl was an independent risk factor for postoperative mortality (odds ratio, 2.6; 95% confidence interval, 1.1 to 7.3; P=0.04). CONCLUSIONS: Similar to the general population, preoperative anemia is associated with adverse postoperative outcomes in patients with CKD. Whether outcomes could be improved by therapeutically targeting higher preoperative hemoglobin levels before cardiac surgery in patients with underlying CKD remains to be determined.