Prognostic value of continuous EEG monitoring during therapeutic hypothermia after cardiac arrest

Abstract

IntroductionContinuous EEG (cEEG) is increasingly used to monitor brain function in neuro-ICU patients. However, its value in patients with coma after cardiac arrest (CA), particularly in the setting of therapeutic hypothermia (TH), is only beginning to be elucidated. The aim of this study was to examine whether cEEG performed during TH may predict outcome.MethodsFrom April 2009 to April 2010, we prospectively studied 34 consecutive comatose patients treated with TH after CA who were monitored with cEEG, initiated during hypothermia and maintained after rewarming. EEG background reactivity to painful stimulation was tested. We analyzed the association between cEEG findings and neurologic outcome, assessed at 2 months with the Glasgow-Pittsburgh Cerebral Performance Categories (CPC).ResultsContinuous EEG recording was started 12 ± 6 hours after CA and lasted 30 ± 11 hours. Nonreactive cEEG background (12 of 15 (75%) among nonsurvivors versus none of 19 (0) survivors; P < 0.001) and prolonged discontinuous "burst-suppression" activity (11 of 15 (73%) versus none of 19; P < 0.001) were significantly associated with mortality. EEG seizures with absent background reactivity also differed significantly (seven of 15 (47%) versus none of 12 (0); P = 0.001). In patients with nonreactive background or seizures/epileptiform discharges on cEEG, no improvement was seen after TH. Nonreactive cEEG background during TH had a positive predictive value of 100% (95% confidence interval (CI), 74 to 100%) and a false-positive rate of 0 (95% CI, 0 to 18%) for mortality. All survivors had cEEG background reactivity, and the majority of them (14 (74%) of 19) had a favorable outcome (CPC 1 or 2).ConclusionsContinuous EEG monitoring showing a nonreactive or discontinuous background during TH is strongly associated with unfavorable outcome in patients with coma after CA. These data warrant larger studies to confirm the value of continuous EEG monitoring in predicting prognosis after CA and TH.

The Utility of EEG, SSEP, and Other Neurophysiologic Tools to Guide Neurocritical Care

“…Rewarming is a common time for seizures to occur, either because a clinical motoric component (e.g., myoclonic status epilepticus) is revealed after discontinuation of paralytics [34,35], or because sedation or hypothermia suppressed or treated the electrographic activity [35]. In addition to detecting seizures, EEG demonstration of a reactive background rhythm or a continuous pattern on amplitude-integrated EEG had a high likelihood of good neurological prognosis, despite the presence of seizures [36][37][38]. Although myoclonic status may have a worse prognosis than nonconvulsive status epileptic in the setting of cardiac arrest treated with hypothermia, myoclonic status is not homogeneous and may have a worse prognosis when "reticular" rather than when associated with an EEG correlate [39].…”

Use of hypothermia in the intensive care unit

“…When correlating to NSE, a continuous EEG pattern demonstrated lower NSE levels compared to a burstsuppression, or flat and non-reactive, background [186] . Recent studies have demonstrated the ability of EEG to identify patients with a poor prognosis based on malignant patterns and good prognosis based on benign patterns [184,188,189] . Patients presenting in a burst-suppression pattern at either initiation of EEG or normothermia, or in SE at normothermia did not regain consciousness.…”

Prognostication in Post Cardiac Arrest Patients Treated with Therapeutic Hypothermia

“…It would seem that waiting at least 72 hours post rewarming and 72 hours post cessation of any analgesia, sedation, or neuromuscular blocking agents, is a good start, however, as stated in multiple studies thus reviewed, the neurological exam must be accompanied by at least one other modality. EEG has a robust amount of evidence with regard to prognostication in the post cardiac arrest TH patients (27,34,35). It can be safely stated that EEG should be performed as early as possible post cardiac arrest, and electrographical seizures should be treated aggressively (14).…”

“…Those patients that succumbed in this trial did not display continuous patterns on their cEEG. Rossetti et al looked at 34 post cardiac arrest TH patients receiving cEEG monitoring (35). They found that the survivors in this study, all 19 out of 34, had reactive backgrounds.…”