A novel quantitative EEG injury measure of global cerebral ischemia

Objective: To develop a novel quantitative EEG (qEEG) based analysis method, cepstral distance (CD) and compare it to spectral distance (SD) in detecting EEG changes related to global ischemia in rats. Methods: Adult Wistar rats were subjected to asphyxic-cardiac arrest for sham, 1, 3, 5 and 7 min (n=5 per group). The EEG signal was processed and fitted into an autoregressive (AR) model. A pre-injury baseline EEG was compared to selected data segments during asphyxia and recovery. The dissimilarities in the EEG segments were measured using CD and SD. A segment measured was considered abnormal when it exceeded 30% of baseline and its duration was used as the index of injury. A comprehensive Neurodeficit Score (NDS) at 24 h was used to assess outcome and was correlated with CD and SD measures. Results: A higher correlation was found with CD and asphyxia time (r=0.81, P<0.001) compared to SD and asphyxia time (r=0.69, P<0.001). Correlation with cardiac arrest time (MAP<10 mmHg) showed that CD was superior (r=0.71, P<0.001) to SD (r=0.52, P=0.002). CD obtained during global ischemia and 90 min into recovery correlated significantly with NDS at 24 h after injury (Spearman coefficient=−0.83, P<0.005), and was more robust than the traditional SD (Spearman coefficient=−0.63, P<0.005). Conclusion: The novel qEEG-based injury index from CD was superior to SD in quantifying early cerebral dysfunction after cardiac arrest and in providing neurological prognosis at 24 h after global ischemia in adult rats. Studying early qEEG changes after asphyxic-cardiac arrest may provide new insights into the injury and recovery process, and present opportunities for therapy.