The Prognostic Value of Simplified EEG in Out-of-Hospital Cardiac Arrest Patients

BackgroundWe previously validated simplified electroencephalogram (EEG) tracings obtained by a bispectral index (BIS) device against standard EEG. This retrospective study now investigated whether BIS EEG tracings can predict neurological outcome after cardiac arrest (CA).MethodsBilateral BIS monitoring (BIS VISTA, Aspect Medical Systems, Inc. Norwood, USA) was started following intensive care unit admission. Six, 12, 18, 24, 36 and 48h after targeted temperature management (TTM) at 33 degrees C was started, BIS EEG tracings were extracted and reviewed by two neurophysiologists for the presence of slow diffuse rhythm, burst suppression, cerebral inactivity and epileptic activity (defined as continuous, monomorphic, >2Hz generalized sharp activity or continuous, monomorphic, <2Hz generalized blunt activity). At 180days post-CA, neurological outcome was determined using cerebral performance category (CPC) classification (CPC1-2: good and CPC3-5: poor neurological outcome).ResultsSixty-three out-of-hospital cardiac arrest patients were enrolled for data analysis of whom 32 had a good and 31 a poor neurological outcome. Epileptic activity within 6-12h predicted CPC3-5 with a positive predictive value (PPV) of 100%. Epileptic activity within time frames 18-24 and 36-48h showed a PPV for CPC3-5 of 90 and 93%, respectively. Cerebral inactivity within 6-12h predicted CPC3-5 with a PPV of 57%. In contrast, cerebral inactivity between 36 and 48h predicted CPC3-5 with a PPV of 100%. The pattern with the worst predictive power at any time point was burst suppression with PPV of 44, 57 and 40% at 6-12h, at 18-24h and at 36-48h, respectively. Slow diffuse rhythms at 6-12h, at 18-24h and at 36-48h predicted CPC1-2 with PPV of 74, 76 and 80%, respectively.ConclusionBased on simplified BIS EEG, the presence of epileptic activity at any time and cerebral inactivity after the end of TTM may assist poor outcome prognostication in successfully resuscitated CA patients. A slow diffuse rhythm at any time after CA was indicative for a good neurological outcome.