Serum biomarkers of brain injury after uncomplicated cardiac surgery: Secondary analysis from a randomized trial

Background: Postoperative cognitive dysfunction is common after cardiac surgery. Postoperative measurements of brain injury biomarkers may identify brain damage and predict cognitive dysfunction. We describe the release patterns of five brain injury markers in serum and plasma after uncomplicated cardiac surgery. Methods: Sixty-one elective cardiac surgery patients were randomized to undergo surgery with either a dextran-based prime or a crystalloid prime. Blood samples were taken immediately before surgery, and 2 and 24 h after surgery. Concentrations of the brain injury biomarkers S100B, glial fibrillary acidic protein (GFAP), tau, neurofilament light (NfL) and neuron-specific enolase (NSE)) and the blood-brain barrier injury marker beta-trace protein were analyzed. Concentrations of brain injury biomarkers were correlated to patients' age, operation time, and degree of hemolysis. Results: No significant difference in brain injury biomarkers was observed between the prime groups. All brain injury biomarkers increased significantly after surgery (tau +456% (25th-75th percentile 327%-702%), NfL +57% (28%-87%), S100B +1145% (783%-2158%), GFAP +17% (-3%-43%), NSE +168% (106%-228%), while beta-trace protein was reduced (-11% (-17-3%). Tau, S100B, and NSE peaked at 2h, NfL and GFAP at 24 h. Postoperative concentrations of brain injury markers correlated to age, operation time, and/or hemolysis. Conclusion: Uncomplicated cardiac surgery with cardiopulmonary bypass is associated with an increase in serum/plasma levels of all the studied injury markers, without signs of blood-brain barrier injury. The biomarkers differ markedly in their levels of release and time course. Further investigations are required to study associations between perioperative release of biomarkers, postoperative cognitive function and clinical outcome. Editorial Comment In a secondary analysis of a randomized trial, Barbu and colleagues report that several markers of neuronal and astroglial injury, but not blood-brain barrier injury, increased after uncomplicated elective cardiac surgery with cardiopulmonary bypass in the absence of clinical signs of neurological damage.