Neurocognitive Function and Cerebral Emboli: Randomized Study of On-pump Versus Off-pump Coronary Artery Bypass Surgery

Background: Neurocognitive impairment can be a debilitating complication after coronary artery bypass graft surgery (CABG). Cardiopulmonary bypass, in particular, cerebral emboli, has been implicated. We compared neurocognitive function and cerebral emboli in patients undergoing on-pump and off-pump CABG.

Methods: 212 patients admitted for CABG were randomly assigned to on-pump (n = 104) or off-pump (n = 108) surgery. Embolic signals were detected with bilateral transcranial Doppler ultrasonography of the middle cerebral artery. Neurocognitive tests were administered preoperatively, on discharge from hospital, at 6 weeks, and at 6 months after surgery. Composite neurocognitive scores were derived using principal component analysis and were compared between the two groups, using analysis of covariance to adjust for baseline values.

Results: At discharge from hospital, the adjusted composite neurocognitive score was 0.25 standard deviations greater in the off-pump group compared with the on-pump group (95% confidence interval: 0.05 to 0.45; p = 0.01). There was no significant difference at 6 weeks (0.09 standard deviations, 95% confidence interval: -0.11 to +0.30; p = 0.4) and 6 months (-0.002 standard deviations, 95% confidence interval: -0.23 to +0.23; p = 1.0). Median number of embolic signals was 1,605 (751 to 2,473) during on-pump and 9 (4 to 27) in off-pump CABG (p < 0.001). Age, length of education, and on-pump status were independent predictors of the predischarge neurocognitive score (p = 0.02, 0.03, and 0.006, respectively).

Conclusions: Cerebral emboli are more prevalent during on-pump CABG. At discharge from hospital, neurocognitive function is better after off-pump surgery, possibly as a result of the lower embolic load. However, the difference in neurocognitive function does not persist at 6 weeks and 6 months.