Cerebral Oximetry is Unreliable in the Detection of Cerebral Ischemia During Carotid Endarterectomy

Back to Annual Symposium
Back to Program

Jason M. Clark, MD, Mark L. Friedell, MD, Xiao-Feng Zhang, MD, Michael R. Isley, PhD.
Orlando Regional Medical Center, Orlando, FL, USA.

OBJECTIVE--Several reports in the literature have extolled the value of cerebral oximetry (rSO2) as a neuromonitoring device during carotid endarterectomy (CEA). The use of rSO2 is enticing because it is simpler and less expensive than electroencephalography (EEG)--the current gold standard--and median nerve somatosensory evoked potentials (SSEP). This study was performed to compare the efficacy of rSO2 with the other two neuromonitoring modalities in detecting cerebral ischemia and determining when to shunt during CEA.
METHODS--- From 10/2000 to 6/2006, 326 CEAs were performed by six surgeons under general anesthesia. Shunting was done selectively, based upon EEG, SSEP and rSO2 monitoring under the auspices of an intraoperative neurophysiologist. All cases were retrospectively reviewed to see if discrepancies existed between EEG/SSEP and rSO2.
RESULTS--- 22 cases (6.7%) showed significant discrepancies. Sixteen cases showed no significant EEG/SSEP changes but profound changes in rSO2: no shunts were placed. In five cases there was no change in rSO2 but a profound change in EEG/SSEP: shunts were used in all cases. In one case, early in the series, the EEG and SSEP were unchanged but the rSO2 dropped precipitously and a shunt was placed. There were no perioperative strokes.
CONCLUSIONS--- Relying on rSO2 alone for selective shunting is potentially dangerous and might have led to intraoperative ischemic strokes in 5 cases and the unnecessary use of shunts in at least 16 cases in this series. The use of rSO2 adds nothing to the information provided by EEG/SSEP in determining when to shunt during CEA.

Back to Annual Symposium
Back to Program