Neuropsychological change and S-100 protein release in 130 unselected patients undergoing cardiac surgery

S-100 protein promises to be a valuable surrogate end point for cerebral injury. This is of particular interest within the context of cardiac surgery. We sought to explore the relationship between change in neurospychological performance attributable to cardiopulmonary bypass and the release of brain-specific S-100 protein.

In an observational comparative study in a University Hospital Cardiac Surgical Unit, S-100 protein release during and 5 hours after the onset of cardiopulmonary bypass was compared with change (from preoperative to 6 to 8 weeks postoperative) in neuropsychological tests in 130 patients undergoing the full range of cardiac surgical procedures.

Neuropsychological performance usually improved, being significantly so in 10 of 25 parameters. S-100 area under the curve (AUC) protein release correlated with age (r=0.24, P<0.008) and bypass time (r=0.17, P<0.02). S-100 Cmax correlated with bypass times (r=0.29, P<0.0001). Bypass times correlated with memory performance (Rey R5; r=-0.21, P<0.03). Less S-100 protein release was associated with better neuropsychological performance, as indexed by significant correlations with the Rey Auditory Verbal Learning memory test, descending Critical Flicker Fusion thresholds, and the Hospital Anxiety and Depression rating scales, typically around r=0.2. Multiple regression models showed that neuropsychological tests accounted for 23% of the variance associated with S-100 AUC release, after partialing out the effects of age and bypass time.

The correlation between S-100 protein release and neuropsychological function supports the belief that it is a measure of brain injury, which may be useful in future studies of mechanisms and prevention.