Purpose: To determine the temporal evolution, clinical correlates, and prognostic significance of electroencephalographic (EEG) patterns in post-cardiac arrest comatose patients treated with hypothermia.
Methods: Prospective cohort study of consecutive post-anoxic patients receiving hypothermia and continuous EEG monitoring between May 2011 and June 2014 (n = 100). In addition to clinical variables, 5-min EEG clips at 6, 12, 24, 48, and 72 h after return of spontaneous circulation (ROSC) were reviewed. EEG background was classified according to the American Clinical Neurophysiological Society critical care EEG terminology. Clinical outcome at discharge was dichotomized as good [Glasgow outcome scale (GOS) 4-5, low to moderate disability] vs. poor (GOS 1-3, severe disability to death).
Results: Non-ventricular fibrillation/tachycardia arrest, longer time to ROSC, absence of brainstem reflexes, extensor or no motor response, lower pH, higher lactate, hypotension requiring >2 vasopressors, and absence of reactivity on EEG were all associated with poor outcome (all p values ≤ 0.01). Suppression-burst at any time indicated a poor prognosis, with a 0% false positive rate (FPR) [95% confidence interval (CI) 0-10%]. All patients (54/54) with suppression-burst or a low voltage (<20 µV) EEG at 24 h had a poor outcome, with an FPR of 0% [95% CI 0-8%]. Normal background voltage ≥ 20 µV without epileptiform discharges at any time interval carried a positive predictive value >70% for good outcome.
Conclusions: Suppression-burst or a low voltage at 24 h after ROSC was not compatible with good outcome in this series. Normal background voltage without epileptiform discharges predicted a good outcome.