Does S100 release predict cognitive dysfunction after coronary artery bypass surgery?

OBJECTIVE: To assess if S100β protein release after cardiac surgery indicates cerebral injury. METHODS: 105 patients undergoing CABG surgery were assessed on a standardized battery of nine neuropsychological tests before surgery, prior to hospital discharge, and three months post-operatively. Blood samples for S100β protein were obtained preoperatively (T0), one hour (T1), six hours (T6), and 24 hours (T24) after the cessation of CPB and analyzed using a standardized commercial assay. The area under the curve (AUC) of S100β release for each patient was correlated against psychometric change scores (postoperative and preoperative test score differences) using a Bonferroni corrected Pearson's correlation coefficient. Linear mixed effects models, using a Bonferroni bound to account for multiple comparisons, were also used to analyze the dependence of neuropsychological scores on IQ, age, time after surgery and S100β AUC. RESULTS: The mean (SD) age of the patients was 63 (9) years. The median duration of bypass was 65 (IQ range 51-75) minutes. The median (IQ range) of S100β in ug/L was 0.03 (0-0.06) at T0, 0.98 (0.55-1.50) at T1, 0.27 (0.16-0.39) at T6 and 0.19 (0.11-0.31) at T24. No significant association was found between S100β release either at individual time points or as an AUC and early or 3-month postoperative change scores for any of the psychometric tests. The linear mixed effect models showed no significant effects for any test on S100β AUC but significant effects on most tests against IQ, age and time of postoperative test. DISCUSSION: Small and transient increases in S100β protein are detectable in most patients after cardiac surgery but are not a reliable marker of neuronal injury.