Abstracts

Rationale: Therapeutic hypothermia (TH) has been proven to improve neurological outcome in survivors of cardiac arrest. An accurate neurologic evaluation is not possible during hypothermia to assess for prognostication and continuous EEG monitoring (cEEG) has been recommended as a possible tool to determine outcome. However, few studies have reported the use of cEEG during hypothermia and eventual outcome. Our objective was to evaluate whether EEG patterns during hypothermia or after rewarming are associated with outcomes in patients post cardiac arrest Methods: We did a retrospective study of all patients who were treated between July 2009 through April 2013 with TH post cardiac arrest. Eighteen patients who had ≧ 1 days of routine or cEEG monitoring which was initiated during hypothermia were selected. TH was achieved using a standard protocol at our institution with goal temperature of 33°C for at least 24 hours. Variables recorded included age, gender, race, comorbidities, type of cardiac arrest, estimated resuscitation time, whether goal temperature was achieved, rewarming time, EEG characteristics throughout the hospital stay, the use of anti-epileptic drugs (AEDs) or anesthetics and discharge outcome. EEG patterns were characterized as "malignant" if there was burst suppression, status epilepticus, myoclonic status, generalized periodic discharges (GPDs) or alpha coma. Benign patterns included focal discharges, periodic discharges (LPDs) without evolution or diffuse slowing. Results: Twelve patients (66.6%) were male, the mean age of patients was 49.4 years (SD ± 18.6), and fifteen patients (83.3%) were African American. Cardiac arrest was due to pulseless electrical activity in 55.5% with asystole and ventricular fibrillation being 22.2% each. The mean downtime was 17.4 minutes (SD ± 14.8). Twelve patients (66.6%) had a malignant pattern on the initial EEG. All remained malignant on the last EEG and none survived hospitalization. Average recording time was 3.5 days. All of these patients received either anesthetics, AEDs or both by day 1. Six patients (33.3%) had a benign pattern (LPDs - two, diffuse slowing - four) on the initial EEG and three survived.One was discharged to nursing home and two were discharged home. All six patients had diffuse slowing on the last EEG prior to discharge. Average recording time was 9.2 days. Conclusions: Our study showed that patients who had malignant patterns on EEG during hypothermia remained in malignant patterns post rewarming and had a 100% mortality rate. Patients who had benign abnormal patterns during hypothermia all showed diffuse slowing on the last EEG and had improved survival rate at time of hospital discharge. This study shows that the initial EEG recording in hypothermia in post cardiac arrest patients is a reliable prognostic marker of outcome. However, inherent weaknesses of retrospective data collection and small sample size may have affected our results. Large, prospective trials are needed to validate these findings.