Continuous electroencephalogram patterns are suggestive of eventual neurologic outcomes in post-cardiac arrest patients treated with therapeutic hypothermia

Introduction: Therapeutic hypothermia (TH) after cardiac arrest (CA) resuscitation is the first therapy proven to increase survival to discharge and neurologic recovery. Methods for neurologic and mortality prognostication after CA resuscitation have been called into question because they were developed based on evidence that was developed prior to the advent of TH. This study examines the relationship between electroencephalogram (EEG) patterns and mortality and neurologic outcomes in post-CA patients undergoing TH. Methods: Eighty-three of 732 patients who had continuous EEG (cEEG) monitoring during TH were included. Continuous EEG tracings were classified as isoelectric, low voltage, burst suppression, epileptic form, and diffuse slowing. Primary outcomes are survival to discharge and Cerebral Performance Categories (CPCs) at hospital discharge. Results: Among patients with favorable neurologic outcomes (CPC1 and CPC2), the duration cardiopulmonary resuscitation and time until return of spontaneous circulation were shorter than observed in patients with poorer neurologic outcomes (CPC3, CPC4, and CPC5). The time to target temperature was equivalent among neurologic outcome groups (499.5 minutes vs 431.0 minutes, P = .09). Favorable neurologic outcome was associated with initial presentation with ventricular tachycardia or ventricular fibrillation and had cEEG patterns suggestive of diffuse slowing and epileptiform waves. Discussion: The use of cEEG can provide prognostication information otherwise not obtainable by clinical examination. Specific cEEG patterns predicted probability of mortality for patients according to their initial rhythm of CA as a function of cardiopulmonary resuscitation time.