BACKGROUND A risk during carotid endarterectomy (CEA) is cerebral ischemia as a result of clamping of the carotid artery. The Cerebral State Monitor is one of several electroencephalogram monitors that reflects level of consciousness of patients during anesthesia. The monitor reports level of consciousness with the empirical parameter Cerebral State Index (CSI) on a 0-100 scale. In this patient-controlled prospective pilot study, we compared the CSI measured from the surgical and control hemispheres of patients undergoing CEA surgery to determine whether the parameter is affected by presumed changes in cerebral blood flow. METHODS Fifteen consenting CEA patients entered this institutionally approved study. We connected a separate Cerebral State Monitor to the left and right sides of the patient's head and recorded CSI intraoperatively. We compared the control-side data with the surgical-side data. RESULTS Clamping caused the surgical-side CSI to drop below the control-side CSI. Shunt activation caused the CSI to rise above the control. The greatest difference between the surgical-side CSI and control-side CSI occurred at the completion of the CEA procedure. These observed trends were not statistically significant in this pilot project. CONCLUSION Our preliminary results suggest that the CSI, and perhaps other similar indexes, may indicate changes in cerebral blood flow acutely during CEA. Our findings lend promise to a new use for these types of electroencephalogram monitors, which are prevalent in operating rooms today.
Processed electroencephalogram response of patients undergoing carotid endarterectomy: a pilot study.