title: Prognostic value of electroencephalography (EEG) after out-of-hospital cardiac arrest in successfully resuscitated patients used in daily clinical practice.
abstract: BACKGROUND
  Out-of-hospital cardiac arrest (OHCA) is associated with a poor prognosis and predicting outcome is complex with neurophysiological testing and repeated clinical neurological examinations as key components of the assessment. In this study we examine the association between different electroencephalography (EEG) patterns and mortality in a clinical cohort of OHCA-patients.
  
  
  METHODS
  From 2002 to 2011 consecutive patients were admitted to an intensive-care-unit after resuscitation from OHCA. Utstein-criteria for pre-hospital data and review of individual patients' charts for post-resuscitation care were used. EEG reports were analysed according to the 2012 American Clinical Neurophysiology Society's guidelines.
  
  
  RESULTS
  A total of 1076 patients were included, and EEG was performed in 20% (n=219) with a median of 3(IQR 2-4) days after OHCA. Rhythmic Delta Activity (RDA) was found in 71 patients (36%) and Periodic Discharges (PD) in 100 patients (45%). Background EEG frequency of Alpha+ or Theta was noted in 107 patients (49%), and change in cerebral EEG activity to stimulation (reactivity) was found in 38 patients (17%). Suppression (all activity <10 μV) was found in 26 (12%) and burst-suppression in 17 (8%) patients. A favourable EEG pattern (reactivity, favourable background frequency and RDA) was independently associated with reduced mortality with hazard ratio (HR) 0.43 (95%CI: 0.24-0.76), p=0.004 (false positive rate: 31%) and a non-favourable EEG pattern (no reactivity, unfavourable background frequency, and PD, suppressed voltage or burst-suppression) was associated with higher mortality (HR=1.62(1.09-2.41), p=0.02) after adjustment for known prognostic factors (false positive rate: 9%).
  
  
  CONCLUSIONS
  EEG may be useful in work-up in prognostication of patients with OHCA. Findings such as Rhythmic Delta Activity (RDA) seem to be associated with a better prognosis, whereas suppressed voltage and burst-suppression patterns were associated with poor prognosis.
authors.affiliation: Department of Cardiology 2142, The Heart Center, Copenhagen University Hospital Rigshospitalet, Blegdamsvej 9, 2100 Copenhagen, Denmark.
authors.forename: Helle
authors.initials: H
authors.lastname: Søholm
authors.affiliation: Department of Neurophysiology, Copenhagen University Hospital Rigshospitalet, Denmark.
authors.forename: Troels Wesenberg
authors.initials: TW
authors.lastname: Kjær
authors.affiliation: Department of Cardiology 2142, The Heart Center, Copenhagen University Hospital Rigshospitalet, Blegdamsvej 9, 2100 Copenhagen, Denmark.
authors.forename: Jesper
authors.initials: J
authors.lastname: Kjaergaard
authors.affiliation: Department of Clinical Sciences, Division of Neurology, Lund University, Lund, Sweden.
authors.forename: Tobias
authors.initials: T
authors.lastname: Cronberg
authors.affiliation: Department of Cardiology 2142, The Heart Center, Copenhagen University Hospital Rigshospitalet, Blegdamsvej 9, 2100 Copenhagen, Denmark.
authors.forename: John
authors.initials: J
authors.lastname: Bro-Jeppesen
authors.affiliation: Emergency Medical Services, The Capital Region of Denmark, Denmark.
authors.forename: Freddy K
authors.initials: FK
authors.lastname: Lippert
authors.affiliation: Department of Cardiology 2142, The Heart Center, Copenhagen University Hospital Rigshospitalet, Blegdamsvej 9, 2100 Copenhagen, Denmark.
authors.forename: Lars
authors.initials: L
authors.lastname: Køber
authors.affiliation: Department of Thoracic Anaesthesiology, The Heart Center, Copenhagen University Hospital Rigshospitalet, Denmark.
authors.forename: Michael
authors.initials: M
authors.lastname: Wanscher
authors.affiliation: Department of Cardiology 2142, The Heart Center, Copenhagen University Hospital Rigshospitalet, Blegdamsvej 9, 2100 Copenhagen, Denmark. Electronic address: helle.soholm@gmail.com.
authors.forename: Christian
authors.initials: C
authors.lastname: Hassager
mesh_terms: D000368:Aged; D016887:Cardiopulmonary Resuscitation / Q000379:methods* / Q000401:mortality; D015331:Cohort Studies; D003266:Continuity of Patient Care; D004569:Electroencephalography / Q000379:methods*; D005260:Female; D058006:General Practice; D006801:Humans; D007362:Intensive Care Units; D008297:Male; D008875:Middle Aged; D008991:Monitoring, Physiologic / Q000379:methods; D009422:Nervous System Diseases / Q000175:diagnosis* / Q000453:epidemiology / Q000209:etiology; D058687:Out-of-Hospital Cardiac Arrest / Q000150:complications* / Q000628:therapy*; D011237:Predictive Value of Tests; D011379:Prognosis; D012189:Retrospective Studies; D018570:Risk Assessment; D017741:Survivors
keywords: Electroencephalography; Out-of-hospital cardiac arrest; Prognostication