Simplified frontal EEG in adults under veno-arterial extracorporeal membrane oxygenation

BackgroundEEG-based prognostication studies in intensive care units often rely on a standard 21-electrode montage ((std)EEG) requiring substantial human, technical, and financial resources. We here evaluate whether a simplified 4-frontal electrode montage ((4-front)EEG) can detect EEG patterns associated with poor outcomes in adult patients under veno-arterial extracorporeal membrane oxygenation (VA-ECMO).MethodsWe conducted a reanalysis of EEG data from a prospective cohort on 118 adult patients under VA-ECMO, in whom EEG was performed on admission to intensive care. EEG patterns of interest included background rhythm, discontinuity, reactivity, and the Synek's score. They were all reassessed by an intensivist on a (4-front)EEG montage, whose analysis was then compared to an expert's interpretation made on (std)EEG recordings. The main outcome measure was the degree of correlation between (4-front)EEG and (std)EEG montages to identify EEG patterns of interest. The performance of the Synek scores calculated on (4-front)EEG and (std)EEG montage to predict outcomes (i.e., 28-day mortality and 90-day Rankin score >= 4) was investigated in a secondary exploratory analysis.ResultsThe detection of EEG patterns using (4-front)EEG was statistically similar to that of (std)EEG for background rhythm (Spearman rank test, rho =0.66, p<0.001), discontinuity (Cohen's kappa, <kappa>=0.955), reactivity (kappa =0.739) and the Synek's score (rho =0.794, p<0.001). Using the Synek classification, we found similar performances between (4-front)EEG and (std)EEG montages in predicting 28-day mortality (AUC (4-front)EEG 0.71, AUC (std)EEG 0.68) and for 90-day poor neurologic outcome (AUC (4-front)EEG 0.71, AUC (std)EEG 0.66). An exploratory analysis confirmed that the Synek scores determined by 4 or 21 electrodes were independently associated with 28-day mortality and poor 90-day functional outcome.ConclusionIn adult patients under VA-ECMO, a simplified 4-frontal electrode EEG montage interpreted by an intensivist, detected common EEG patterns associated with poor outcomes, with a performance similar to that of a standard EEG montage interpreted by expert neurophysiologists. This simplified montage could be implemented as part of a multimodal evaluation for bedside prognostication.