The Relationship between EEG Findings and Prognosis in Out-of-Hospital Cardiac Arrest Patients during Therapeutic Hypothermia

ABSTRACT

PURPOSE: Prediction of neurologic outcome in survivors after cardiac arrest is difficult. In particular, since therapeutic hypothermia has emerged as the standard treatment for post cardiac arrest syndrome, the prediction has been more difficult. Methods for prediction of neurologic prognosis include the general neurologic examination, SSEPs, EEG, serum biomarkers, and so on. Among these, EEG was recommended for detection of non-convulsive seizure since early phase of post cardiac arrest syndrome. However, the relationship between EEG finding and neurologic outcome is not yet clear. METHODS: We conducted a retrospective observational study using a prospectively collected hypothermia database. We collected EEG findings during hypothermia and other data from January 2010 to December 2012. The EEG findings were classified according to five patterns as extremely low voltage, continuous slow wave, burst suppression, status epilepticus, and other. We analyzed the relationship between EEG pattern and one-month CPC score after cardiac arrest. RESULTS: During the study period, 121 patients were enrolled in the hypothermia database. Among these patients, 84 patients underwent EEG during hypothermia and were enrolled. The EEG patterns of enrolled patients were 20 extremely low voltage, 39 generalized slow wave, 15 burst suppression, 8 status epilepticus, and 2 alpha coma. None of the periodic, status eplilepticus, and alpha coma pattern patients showed a good neurologic outcome (CPC 1 or 2). Two of 20 extremely low voltage and 28 of 39 continuous slow wave pattern patients recovered to good neurologic outcome. CONCLUSION: Burst suppression and status epilepticus EEG pattern during hypothermia treatment showed an association with poor neurologic outcome.