Detection of Ischemic Electroencephalography Changes During Carotid Endarterectomy Using Synchronization Likelihood Analysis

Introduction: The intensive care unit is short of a suitable tool for instant detection of cerebral ischemia. Synchronization likelihood (SL) electroencephalography (EEG) analysis has proven to be a promising approach for instant online seizure detection. The aim of this study was to investigate the value of SL analysis in the detection of cerebral ischemia. Patients and Methods: SL analysis was studied using conventional EEG recordings during 143 carotid endarterectomy procedures. We compared EEG data before and after clamping of the carotid artery for 2 different anesthesia protocols (isoflurane or propofol) in patients with and without development of cerebral ischemia, making use of SL analysis. Cerebral ischemia was defined by using EEG variables. Results: Fifty-eight patients received isoflurane and 85 propofol anesthesia of whom overall 27% developed ischemia. In patients from the isoflurane group who developed ischemia, the mean overall SL decreased [from 0.220 (SD 0.052) before clamping to 0.208 (SD 0.044) after clamping; P = 0.06] In patients with ischemia in the propofol group, the mean overall SL remained stable (0.185; P = 0.87) Patients from both groups without development of ischemia had increased mean overall SL values after clamping [isoflurane: from 0.210 (SD 0.041) before clamping to 0.219 (SD 0.051) after clamping; P = 0.08. Propofol: from 0.188 (SD 0.019) to 0.189 (SD 0.021); P = 0.57]. Conclusions: No significant changes in the mean SL were observed after development of ischemia during either isoflurane or propofol anesthesia. SL analysis does not seem suitable for detection of cerebral ischemia in anesthetized patients.