Determinants of cognitive change after coronary artery bypass surgery: a multifactorial problem

Background. Several studies have investigated predictors of cognitive decline after coronary artery bypass grafting (CABG), but there is little consensus as to which specific factors are predictive of poor cognitive outcomes. Methods. We evaluated 127 patients undergoing CABG with standardized neuropsychological tests preoperatively, at 1 month and at 1 year. The outcome measure was a continuous variable reflecting change in z-scores for eight cognitive domains over time for individual patients. Univariate analyses were performed to evaluate the association between the demographic, operative, and postoperative factors and the cognitive outcome variables. Factors that were significant were included in a multiple linear regression analysis. Results. Among the medical history variables, diabetes was associated with change in executive functions and psychomotor speed. Some of the operative variables were associated with short-term changes, but none with the 1-year outcomes. For example, the surgeon’s rating of degree of difficulty in selecting a cross-clamp site was associated with change in attention. Higher mean pump rate during the procedure was associated with improved performance on tests of language. The cognitive domains associated with medical variables were different from those associated with surgical variables, and the associations observed at 1-year were different from those seen at 1-month. Conclusions. Change in cognition after CABG is associated with both medical and surgical variables. The specifics of these associations depend on the choice of time points after surgery. This suggests that there are multiple etiologies for these changes, with nonspecific effects of anesthesia and prolonged surgery interacting with the more specific effects of the surgical procedure itself.