The Prognostic Value of 48-h Continuous EEG During Therapeutic Hypothermia After Cardiac Arrest

Background The aim of this study was to evaluate the prognostic value of continuous electroencephalogram (cEEG) during the first 48 h following cardiac arrest (CA) in patients treated with targeted temperature management (TTM). Methods We reviewed data from 92 comatose post-CA patients over a 6 year-period; cEEG recordings were performed during TTM and restoration of normothermia. EEG findings were divided into four time-periods: 0–8, 8–16, 16–24, and 24–48 h after CA. Background EEG findings were defined as moderate encephalopathy (diffuse slowing with reactivity/variability), severe encephalopathy (diffuse slowing without reactivity/variability), burst suppression or suppression, and dichotomized as malignant (suppression/burst suppression/severe encephalopathy) or benign (moderate encephalopathy). Epileptiform activity was defined as the presence of seizures, sporadic epileptiform discharges, or periodic discharges. Neurological outcome was assessed at 3 months using the cerebral performance categories (CPC) score (good outcome: CPC 1–2). Results 26/92 (28 %) patients had a good outcome. Malignant patterns were associated with a poor outcome at all time-points, with a high positive predictive value (94–97 %) but a poor negative predictive value (44–56 %). Epileptiform activity did not influence the prognostic value of EEG patterns. All patients with moderate encephalopathy and seizures or generalized periodic discharges had a poor outcome. Conclusions cEEG can identify patients with poor outcome from the first hours following CA, with limited predictive value for good outcome. Epileptiform activity did not improve the prognostic accuracy of EEG, but seizures and generalized periodic discharges were associated with poor outcome even when developing on a benign EEG pattern.