Serum protein S100 as marker of postoperative delirium after off-pump coronary artery bypass surgery: secondary analysis of two prospective randomized controlled trials.

BACKGROUND

To investigate the predictive value of S100 (biochemical marker of neuroglial injury) for the occurrence of postoperative delirium (POD) in patients undergoing off-pump coronary artery bypass (OPCAB)-surgery.

METHODS

We enrolled 92 patients older than 18 years undergoing elective OPCAB-surgery. Serum-levels of S100 were determined at baseline (BL), end of surgery (EOS) and on the first postoperative day (PD1). Postoperatively, all-patients were evaluated daily until PD5 for the presence of POD using the confusion assessment method (CAM) or the confusion assessment method for the intensive care unit (CAM-ICU) for patients in the intensive care unit (ICU).

RESULTS

The overall incidence of POD was 21%. S100-values on PD1 significantly predicted the occurrence of POD during the later hospital stay [area under the curve (AUC)=0.724 (95% confidence interval (CI): 0.619-0.814); p=0.0001] with an optimal cut-off level of 123 pg mL-1 (sensitivity 100%, specificity 44%). Below this value, the absence of POD was predicted correctly in 43.66% of patients without POD [negative predictive value (NPV) of 100% (95%CI: 88.8%-100.0%) - positive predictive value of 29.8% (95%CI: 18.4%-43.4%) and likelihood ratio (LR) of the negative result of 0.0].

CONCLUSIONS

S100-levels <123 pg mL-1 measured on PD1 reliably rule out the development of POD after elective OPCAB-surgery. This finding warrants testing whether S100-levels could be used for a risk stratification of cardiac surgical patients and for the initiation of preventive measures against POD in patients with high postoperative S100-levels.