Biochemical markers for brain damage after cardiac surgery -- time profile and correlation with cognitive dysfunction

Cerebral dysfunction is common after cardiac surgery and may be reflected in increasing blood concentrations of neuron specific enolase (NSE) and S-100 beta protein. The aim of the study was to determine the optimal timing of blood sampling.

We studied 15 patients undergoing coronary artery bypass grafting. Serum concentrations of NSE and S-100 beta protein were measured before surgery and after 12, 18, 24, 30, and 36 h. Neuropsychological testing was performed before surgery, at discharge from hospital and after 3 months.

Serum concentrations of both NSE and S-100 beta protein increased significantly. At the first postoperative test, seven patients had cognitive dysfunction and a significant correlation was found between the composite z-score and the increase in the NSE level after 36 h (R = 0.76, P=0.001). The median increase in NSE after 36 h was 4.1 microg/l in patients having cognitive dysfunction and 0.9 microg/l in the remaining patients (P<0.05). No significant correlation was found between cognitive dysfunction and the increase in S-100 beta protein. After 3 months, no statistically significant correlation was found between either NSE or S-100 beta protein and cognitive dysfunction.

NSE seems to be a useful blood marker for early cognitive dysfunction after coronary artery bypass grafting, optimal timing of blood sampling being at approximately 36 h postoperatively.