Early electroencephalography for outcome prediction of postanoxic coma: A prospective cohort study

Abstract

Objective: To provide evidence that early electroencephalography (EEG) allows for reliable prediction of poor or good outcome after cardiac arrest.

Methods: In a 5-center prospective cohort study, we included consecutive, comatose survivors of cardiac arrest. Continuous EEG recordings were started as soon as possible and continued up to 5 days. Five-minute EEG epochs were assessed by 2 reviewers, independently, at 8 predefined time points from 6 hours to 5 days after cardiac arrest, blinded for patients' actual condition, treatment, and outcome. EEG patterns were categorized as generalized suppression (<10 μV), synchronous patterns with ≥50% suppression, continuous, or other. Outcome at 6 months was categorized as good (Cerebral Performance Category [CPC] = 1-2) or poor (CPC = 3-5).

Results: We included 850 patients, of whom 46% had a good outcome. Generalized suppression and synchronous patterns with ≥50% suppression predicted poor outcome without false positives at ≥6 hours after cardiac arrest. Their summed sensitivity was 0.47 (95% confidence interval [CI] = 0.42-0.51) at 12 hours and 0.30 (95% CI = 0.26-0.33) at 24 hours after cardiac arrest, with specificity of 1.00 (95% CI = 0.99-1.00) at both time points. At 36 hours or later, sensitivity for poor outcome was ≤0.22. Continuous EEG patterns at 12 hours predicted good outcome, with sensitivity of 0.50 (95% CI = 0.46-0.55) and specificity of 0.91 (95% CI = 0.88-0.93); at 24 hours or later, specificity for the prediction of good outcome was <0.90.

Interpretation: EEG allows for reliable prediction of poor outcome after cardiac arrest, with maximum sensitivity in the first 24 hours. Continuous EEG patterns at 12 hours after cardiac arrest are associated with good recovery. ANN NEUROL 2019;86:203-214.

Figure 1

Examples of synchronous patterns with ≥50% suppression. (A) Burst suppression with identical bursts. (B) Burst suppression with abrupt‐onset, generalized bursts (these bursts could alternatively be described as “highly epileptiform bursts”). (C) Burst suppression with abrupt‐onset, generalized bursts, alternating with generalized discharges. (D) Generalized periodic discharges on a suppressed background. [Color figure can be viewed at www.annalsofneurology.org]

Figure 2

Chance of good outcome, given the electroencephalographic (EEG) pattern and its timing after cardiac arrest. In each cell, the percentage indicates the chance of good outcome, the numbers in parentheses the corresponding 95% confidence interval, and N the number of patients with the EEG pattern at the given time. BS = burst suppression; GPD = generalized periodic discharge; Supp. = suppression; supp. bg. = suppressed background pattern. [Color figure can be viewed at www.annalsofneurology.org]

Figure 3

Predictive value of the electroencephalogram (EEG) as a function of time after cardiac arrest. "Corrected" values follow from the mixed model, which accounts for the sensitivity and specificity at the 8 time points being calculated from different, partially overlapping groups of patients. Error bars indicate 95% confidence intervals. Numbers (N) refer to the total number of patients with an EEG epoch available at the indicated time point. (A) Test characteristics for the prediction of poor outcome based on “suppression” or “synchronous pattern with ≥50% suppression.” (B) Test characteristics for the prediction of good outcome based on "continuous" EEG pattern. [Color figure can be viewed at www.annalsofneurology.org]

Figure 4

Prognostic yield of repeated electroencephalographic (EEG) assessment. This analysis includes only patients with an EEG recording started within 6 hours after cardiac arrest. Bars indicate the fraction of subjects in whom an unfavorable (“suppression” or “synchronous pattern with ≥50% suppression”) or favorable EEG pattern ("continuous") was observed up to the indicated time point, respectively. (A) Results for all 185 patients with poor outcome. (B) Results for all 155 patients with good outcome. [Color figure can be viewed at www.annalsofneurology.org]

Figure 5

Receiver operating characteristic (ROC) curves for multivariate models. Solid lines indicate ROC curves, lighter areas the corresponding 95% confidence intervals. Each subfigure shows results for the model without electroencephalography (EEG) and the model including EEG. Details for models that include EEG are shown in Table 3. (A) Models for prediction of poor outcome. Clinical parameters include age, initial cardiac rhythm (ventricular fibrillation [VF] or other), maximum dose of propofol in the first 24 hours after cardiac arrest, and the application of hypothermia (yes or no). (B) Models for prediction of good outcome. Clinical parameters include age, initial cardiac rhythm (VF or other), and maximum doses of propofol and fentanyl in the first 24 hours after cardiac arrest. [Color figure can be viewed at www.annalsofneurology.org]