Reduced EEG montage has a high accuracy in the post cardiac arrest setting

Objective: To study if comatose cardiac arrest patients can be assessed with a reduced number of EEG electrodes. Methods: 110 routine EEGs from 67 consecutive patients, including both hypothermic and normothermic EEGs were retrospectively assessed by three blinded EEG-experts using two different electrode montages. A standard 19-electrode-montage was compared to the reduced version of the same EEGs, down-sampled to six electrodes (F3, T3, P3, F4, T4, P4). We used intra-rater and inter-observer statistics to assess the reliability of the reduced montage for background features and discharges. Results: The reduced montage had almost perfect performance for background continuity (κ 0.80–0.88), including identification of highly malignant backgrounds (burst-suppression/suppression) (κ 0.85–0.94) and benign backgrounds (continuous/nearly continuous) (κ 0.85–0.91). We found substantial performance for identifying rhythmic/periodic discharges (κ 0.79–0.86). The reduced montage had high accuracy for assessment of both highly malignant (sensitivity 91–95%, specificity 94–99%) and benign (sensitivity 89–98%, specificity 91–96%) backgrounds, and periodic/rhythmic patterns (sensitivity 79–100%, specificity 89–99%), compared to the full montage. The inter-observer variability was not increased by the reduced montage. Conclusion: Reduced EEG had high performance for classifying important background and discharge patterns in this post cardiac arrest cohort. Significance: Our results support the use of reduced EEG-montage for monitoring comatose cardiac arrest patients.