Delayed Deterioration of EEG Background Rhythm Post-cardiac Arrest

Background Electroencephalogram (EEG) background continuity is associated with a favorable prognosis in cardiac arrest patients post-therapeutic hypothermia. However, the continuous EEG in a subset of patients will undergo 'delayed EEG deterioration'; they will invariably have poor outcome. The aim of this study was to characterize this phenomenon. Methods We studied a prospectively collected cohort of consecutive cardiac arrest patients who underwent therapeutic hypothermia between July 2012 and May 2015. We identified patients with an initially favorable EEG rhythm post-cooling and characterized a subset of patients with delayed EEG deterioration. Results A total of 133 patients were included in the analysis. Of these, 69/133 (51.9%) had an initially favorable EEG. Of those patients with initially favorable EEG, 7/69 (10.1%) had a subsequent deterioration. Delayed EEG deterioration was associated with poor outcome. The median time to deterioration was 55 h. Conclusions Delayed EEG deterioration is associated with poor clinical outcomes. We hypothesize that this is the result of delayed neuronal degeneration, the exact mechanism requiring further exploration. Identifying patients with delayed EEG deterioration post-therapeutic hypothermia is paramount as further interventions may yet salvage their outcomes, though further study is needed.