Residual cognitive dysfunctioning at 6 months following coronary artery bypass graft surgery

Neuropsychological testing is a sensitive method for quantitative assessment of cognitive dysfunctioning following cardiopulmonary bypass (CPB). However, the methodological problems associated with this method, such as learning effects due to repeated testing and the effects of distress on test performance, have often been underestimated. In this study, these confounding effects were controlled for by including the spouses of patients, exposed to the same potential stress effects associated with the operation, as a nonsurgical control group. The experimental group consisted of 63 patients (40-75 years) undergoing elective coronary artery bypass graft (CABG) surgery. A battery of standardized neuropsychological tests was administered to both groups 2 weeks preoperatively and 1 week, 1 month, and 6 months postoperatively. Statistical testing of inter-group differences in preoperative to postoperative changes in test performance revealed the following results: (1) For immediate memory and learning, in general test scores showed the same time course for both groups. (2) For recent memory, patients' scores showed a significant deterioration at 1 month after CABG surgery compared with the scores of spouses. This effect had not completely disappeared at 6 months postoperatively. (3) For attention and psychomotor speed as well as verbal fluency, patients' scores had deteriorated significantly at 1 week after surgery, with incomplete recovery at 6 months. These negative cognitive effects were not related to the patients' ages or CPB parameters (duration of CPB, aortic cross-clamp time, mean flow and arterial pressure during CPB and aortic cross-clamping, and minimum nasopharyngeal temperature). No differences in self-ratings of mood over time were found between the patients and spouses. The results indicate that, when adequately controlling for the effects of learning and distress, some cognitive functions are still impaired at 6 months after CABG surgery.