Retrospective Visual and Quantitative Assessment of Burst Suppression With and Without Identical Bursts in Patients After Cardiac Arrest.

BACKGROUND

The objective of this study was to assess the prognostic significance of identical bursts (IBs) in cardiac arrest survivors with burst suppression on continuous electroencephalogram (cEEG) monitoring. Burst suppression with IBs is associated with poor neurological outcomes and mortality.

METHODS

We conducted a retrospective analysis of cardiac arrest survivors admitted to a US academic medical center between 2013 and 2021 who had an EEG background of burst suppression. EEG and clinical features were extracted from our institutional review board-approved repositories. EEG features were qualitatively and quantitatively rated at 0, 12, 24, 48, and 72 h following initiation of monitoring. Qualitative visual assessment occurred, blinded to all clinical features, including outcomes, and in accordance with the current American Clinical Neurophysiology Society definition. Quantitative assessment involved manual marking of 50 consecutive pairs of bursts and interburst intervals (IBIs) for analysis. Similarity of bursts/IBIs were assessed with correlation coefficients. The primary clinical outcome was survival to hospital discharge. Comparisons were performed between groups, and a multivariate model was generated for significant variables.

RESULTS

Of 593 cardiac arrest patients, 203 (34.2%) had burst suppression. Thirty-one (15.3%) patients with burst suppression survived. IBs were detected in 80 patients (39.4% of burst suppression). No patient with qualitatively identified IBs had a good neurological outcome (76 deceased, 4 in a state of unresponsive wakefulness). Whereas 11 of 123 (8.9%) with burst suppression without IB had Cerebral Performance Category scores of 1-2. Quantitative analysis of 268 instances of burst suppression demonstrated that mortality was associated with longer bursts, longer IBIs, and higher burst correlation coefficients (i.e., bursts that were more similar to each other) only when allowing analysis of the first 2 s of bursts. Binary logistic regression showed that the only independent EEG predictor of mortality was the burst correlation coefficient measured over 2 s (adjusted odds ratio 4.82 [95% confidence interval 1.21-8.42], p = 0.009).

CONCLUSIONS

Using a single-center US cohort, IBs within 72 h post cardiac arrest were strongly associated with poor outcomes. Quantitative analysis revealed that including the first 2 s of the bursts was superior to limiting the analysis to 0.5-1 s.