O81 High frequency EEG activity is associated with preserved cerebral function in critical illness

Abstract

Objectives To assess the value of continuous electroencephalography (cEEG) in detecting delirium in a medical intensive care unit (ICU), applying a visual, qualitative analysis in accordance with The American Clinical Neurophysiology Society’s Standardized Critical Care Terminology. Methods Single-center prospective observational study including 102 patients with sepsis or septic shock. Full scalp cEEG was recorded continuously after admission.Delirium screening was applied six times daily using the Confusion Assessment Method for the ICU (CAM-ICU). Results Sixty-six patients (65%) had at least one episode of delirium during their ICU stay; thirty (29%) remained delirium-free; six patients (6%) remained comatose and unassessable. In total, 6723 h of EEG-recordings were visually analyzed. Preserved beta activity (>13 Hz) was independently associated with staying delirium-free ( p 10 - 7 ) along with preserved EEG reactivity ( p 0.001 ). Reduced beta activity emerged as the stronger predictor for delirium, eliminating theta and delta electrographic band power. Time-dependent Cox regression associated burst suppression with reduced mortality. Sporadic periodic discharges occurred in fifteen patients of whom 87% were delirious. Treatment-requiring epileptic or non-convulsive EEG activity was not observed. Discussion Neuronal desynchronization expressed as loss of high frequency EEG activity could be a potential biomarker for delirium. Whether this is superior to bedside clinical screening with validated tests such as the CAM-ICU remains to be further examined. Conclusions Beta activity was the strongest predictor of preserved cerebral function in septic patients and superior to the previously described association between delirium and low frequency delta activity. Non-convulsive activity was not observed. Significance Early detection of cerebral deterioration by cEEG may provide a window for intervention to improve outcome.