The EEGs were done at 24 hours after ROSC in this study:
Non-ventricular fibrillation/tachycardia arrest, longer time to ROSC, absence of brainstem reflexes, extensor or no motor response, lower pH, higher lactate, hypotension requiring greater than 2 vasopressors, and absence of reactivity on EEG were all associated with poor outcome (all p values less than or equal to 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 (less than 20 µV) EEG at 24 h had a poor outcome, with an FPR of 0 % [95 % CI 0–8 %]. Normal background voltage greater than or equal to 20 µV without epileptiform discharges at any time interval carried a positive predictive value greater than 70 % for good outcome.
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.
Of note, all of the patients in this study had induced hypothermia. If these findings are confirmed (this was a small study) they will challenge the present notion that it takes several days post cardiac arrest to assess neurologic prognosis in patients who receive hypothermia.