Related Experiment Video
Updated: Jan 13, 2026
Microvascular Embolism Mouse Model for In Vivo Two-photon Microscopy Using Fluorescent Polystyrene Microspheres
Published on: November 21, 2025
S100 protein and its relation to cerebral microemboli in on-pump and off-pump coronary artery bypass surgery
Reza Motallebzadeh1, Robin Kanagasabay, Martin Bland
1Department of Cardiac Surgery, St George's Hospital and Medical School, London SW17 0QT, UK.
Insights
On-pump coronary artery bypass grafting (CABG) surgery generated significantly more cerebral microemboli than off-pump CABG. S100 beta levels were higher during on-pump CABG, but no correlation was found between S100 beta and microemboli.
Area of Science:
- Cardiovascular Surgery
- Neurology
- Biomarker Research
Background:
- S100 protein is a marker for cerebral injury.
- Previous studies on S100 levels during coronary artery bypass grafting (CABG) are limited by extracerebral contamination.
- Cerebral microemboli (high-intensity transient signals or HITS) are suspected to cause neurocognitive dysfunction after CABG.
Purpose of the Study:
- To compare the number of HITS during on-pump versus off-pump CABG.
- To accurately measure S100 levels by minimizing extracerebral contamination.
- To assess the relationship between S100 changes and HITS during CABG.
Main Methods:
- Thirty-five patients were randomized to on-pump (n=20) or off-pump (n=15) CABG.
- High-intensity transient signals (HITS) were monitored using transcranial Doppler ultrasonography.
- S100 protein levels were measured preoperatively, intraoperatively, and 48 hours postoperatively, with a cell saver used in the on-pump group to reduce contamination.
Main Results:
- On-pump CABG showed significantly more HITS (2016+/-1897) than off-pump CABG (16+/-21).
- Intraoperative S100 levels were 1.6 times higher in the on-pump group compared to the off-pump group (P=0.01).
- No correlation was found between S100 levels and HITS in either group.
Conclusions:
- On-pump CABG is associated with a significantly higher number of cerebral microemboli compared to off-pump CABG.
- This study demonstrated higher S100 beta levels during on-pump CABG, though not statistically significant, due to minimized extracerebral contamination.
- No correlation between S100 beta and microemboli count was observed, potentially due to the study's sample size.
Objectives:
S100 protein has been used as a marker for cerebral injury. Studies have reported lower levels in off-pump coronary artery surgery (CABG) compared to on-pump surgery. However, most of these are flawed as S100 from extracerebral sources was included (e.g. blood from cardiotomy suckers). Microemboli (high-intensity transient signals or HITS) during CABG have been implicated as a cause of postoperative neurocognitive dysfunction. The aim of this study was to compare the number of HITS during on-pump and off-pump CABG, measure S100 accurately by excluding extracerebral sources, and assess whether any changes in S100 were related to HITS.
Methods:
Thirty-five patients admitted for CABG were randomised to on-pump (n=20) or off-pump (n=15) surgery. Bilateral transcranial Doppler ultrasonography was performed on the middle cerebral artery to detect HITS. S100 was measured preoperatively, at termination of bypass in on-pump surgery, at completion of anastomoses in off-pump surgery, and 48 h postoperatively. A cell saver was used instead of cardiotomy suction in the on-pump group in order to limit extracerebral contamination of the S100 assay.
Results:
The number of HITS was 2016+/-1897 during on-pump and 16+/-21 during off-pump surgery (P<0.0001). In on-pump surgery S100 increased from 0.05+/-0.03 to 0.50+/-0.28 microg/l (P<0.0001) at termination of bypass. In off-pump surgery S100 increased from 0.08+/-0.05 to 0.35+/-0.20 microg/l (P<0.0001) at completion of anastomoses. The mean intraoperative S100 in the on-pump group was 1.6 times greater compared to that in the off-pump group (95% CI 0.88-2.8; P=0.01). There was no evidence of a relationship between S100 and HITS in both groups. By 48 h S100 decreased to 0.22+/-0.14 microg/l in the on-pump and 0.21+/-0.09 microg/l in the off-pump group (P<0.0001, compared to the preoperative value).
Conclusions:
We have demonstrated a significantly higher number of cerebral microemboli in patients undergoing on-pump compared to off-pump CABG. By limiting contamination from extracerebral sources, we have shown S100 beta levels during on-pump CABG one and a half times greater than that in off-pump, although this did not reach statistical significance. In addition, we have shown no correlation between S100 beta and the total microemboli count, possibly because of the small numbers in this study.
