S100B and Cardiac Surgery

Sammanfattning: The brain-derived protein S100B is a 21 Kda dimerand have been used as a serum marker for brain damage of different etiology. The feasability of protein S100B as serum marker for brain damage after cardiac surgery was studied in this thesis. One unexpected finding was made, which changed the basis for interpration of S100B levels. Shed blood collected during surgery with cardiotomy suction contained high levels of S100B. In parallell, shed blood collected after surgery from drainage tubed also contained high levels of S100B. Retransfusion of this blood by means of cardiotomy suction or autotransfusion increased serum levels of S100B, making interpretation of serum samples drawn after retransfusion difficult to interpret, since the measured levels of S100B partly depended on extracerebral contamination. Th in vivo half-life for S100B was determined 25 minutes, and was not found to depend on glomerular filtration rate. As a consequence, any infusion of extracerebral S100B will be eliminated within 2-3 hours. A model for early S100B release was constructed, which corrected for extracerebral S100B and estimated release after surgery. With this model, a weak association was found between neuropsychological decline and increased release the first 4 hours after surgery. The nature of this association makes it difficult to use S100B in clinical practice for evaluating cognitive function in patients after surgery. In patients who suffered a brain infarction, absolute S100B levels 48 hours after surgery were found to correlate with size of the infarcted brain tissue. In these patients, S100B levels also predictedsurvival. In this group, patients with S100B above 0,5 microgram/L had shorter survival compared to those below that level. Increased S100B 48 hours after surgery was also associated with risk-factors for adverse neurological outcome.