Short-term and long-term neuropsychological consequences of cardiac surgery with extracorporeal circulation

Cognitive dysfunction after extracorporeal circulation is a major continuing problem in modern cardiac surgery. We designed this prospective study to update the incidence of postoperative neuropsychological changes after routine cardiopulmonary bypass (CPB) and to identify perioperative variables associated with these complications.

We assessed the patients with a comprehensive neuropsychological test battery 1 day before, 7 days after (n = 109) and 6 months after (n = 91) cardiopulmonary bypass. We used patients undergoing major vascular or thoracic surgery as a surgical control group (n = 20).

Repeated measures multivariate analysis of variance (using surgical group as a between-subjects factor) on the group data revealed significant changes early after surgery compared with the preoperative performance (P = 0.001). The early changes are characterized by a significant decrease of visual attention and verbal memory performance (univariate F-tests, always P < 0.05). Cardiac patients showing cognitive impairment after cardiac surgery had lower preoperative ejection fractions (P = 0.014) and a more complicated medical history (P = 0.046). At 6-month follow-up, the patients performed significantly better than before surgery (P < 0.001). CPB patients showing persistent cognitive impairment at follow-up were significantly older at the time of surgery (P = 0.005). Individual comparisons revealed that 45% of the patients undergoing CPB showed evidence of cognitive impairment soon after surgery. In 12% of the patients, the cognitive sequelae persisted at follow-up. Both group data and individual incidence rates revealed neither significant pre-post differences between the surgical groups nor a time-by-group interaction effect. Variables directly associated with CPB were not significantly associated with the occurrence of cognitive impairment after surgery.

We conclude that an important proportion of the cognitive impairment after cardiac surgery is likely to be due to nonspecific effects of surgery.