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

Background: Cerebral dysfunction is common after cardiac surgery and may be reflected in increasing blood concentrations of neuron specific enolase (NSE) and S-100β protein. The aim of the study was to determine the optimal timing of blood sampling. Methods: We studied 15 patients undergoing coronary artery bypass grafting. Serum concentrations of NSE and S-100β 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. Results: Serum concentrations of both NSE and S-100β 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 µg/l in patients having cognitive dysfunction and 0.9 µg/l in the remaining patients (P<0.05). No significant correlation was found between cognitive dysfunction and the increase in S-100β protein. After 3 months, no statistically significant correlation was found between either NSE or S-100β protein and cognitive dysfunction. Conclusion: 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.