Neurocognitive dysfunction after coronary artery bypass surgery: a systematic review

Substantial, albeit scattered, evidence suggests that coronary artery bypass grafting may impair cognitive function. As methods and definitions differ greatly across studies, the reported incidence of cognitive decline after coronary bypass surgery varies widely as well. The aim of the present study was to systematically review those studies on cognitive decline that are relatively comparable and meet with certain quality criteria.

Four electronic databases and the references of several abstract books and earlier reviews were used to identify relevant literature. Stringent criteria, based in part on the 1994 consensus meeting on assessment of neurobehavioral outcomes after cardiac surgery, were used to assess the studies that were found. In total, 256 different titles were found, of which 23 met with the formulated selection criteria.

Twelve cohort studies and eleven intervention studies were evaluated. A pooled analysis of six highly comparable studies yielded a proportion of 22.5% (95% confidence interval, 18.7%-26.4%) of patients with a cognitive deficit (a decrease of at least 1 standard deviation in at least two of nine or ten tests) 2 months after the operation.

Neurocognitive dysfunction is a frequently occurring complication of coronary artery bypass grafting. The etiologic contribution of cardiopulmonary bypass to this complication will remain unclear until a randomized trial that directly compares off-pump and on-pump bypass surgery is carried out.