title: Auditory-evoked potentials during coma: do they improve our prediction of awakening in comatose patients?
abstract: OBJECTIVE
  The mismatch negativity (MMN), an auditory event-related potential, has been identified as a good indicator of recovery of consciousness during coma. We explored the predictive value of the MMN and other auditory-evoked potentials including brainstem and middle-latency potentials for predicting awakening in comatose patients after cardiac arrest or cardiogenic shock.
  
  
  METHODS
  Auditory brainstem, middle-latency (Pa wave), and event-related potentials (N100 and MMN waves) were recorded in 17 comatose patients and 9 surgical patients matched by age and coronary artery disease. Comatose patients were followed up daily to determine recovery of consciousness and classified as awakened and nonawakened.
  
  
  RESULTS
  Among the auditory-evoked potentials, the presence or absence of MMN best discriminated between patients who awakened or those who did not. Mismatch negativity was present during coma in all patients who awakened (7/7) and in 2 of those (2/10) who did not awaken. In patients who awakened and in whom MMN was detected, 3 of those awakened between 2 and 3 days and 4 between 9 and 21 days after evoked potential examination. All awakened patients had intact N100 waves and identifiable brainstem and middle-latency waves. In nonawakened patients, N100 and Pa waves were detected in 5 cases (50%) and brainstem waves in 9 (90%).
  
  
  CONCLUSIONS
  The MMN is a good predictor of awakening in comatose patients after cardiac arrest and cardiogenic shock and can be measured days before awakening encouraging ongoing life support.
authors.affiliation: Division of Cardiac Surgery, University of Ottawa Heart Institute, Ottawa, Ontario, Canada; The Ottawa Hospital Research Institute, Ottawa, Ontario, Canada. Electronic address: rrodriguez@toh.on.ca.
authors.forename: Rosendo A
authors.initials: RA
authors.lastname: Rodriguez
authors.affiliation: Division of Neurology, Department of Medicine, The Ottawa Hospital, Ottawa, Ontario, Canada.
authors.forename: Miguel
authors.initials: M
authors.lastname: Bussière
authors.affiliation: Division of Cardiology, University of Ottawa Heart Institute, Ottawa, Ontario, Canada.
authors.forename: Michael
authors.initials: M
authors.lastname: Froeschl
authors.affiliation: Division of Cardiac Anesthesia, University of Ottawa Heart Institute, Ottawa, Ontario, Canada.
authors.forename: Howard J
authors.initials: HJ
authors.lastname: Nathan
mesh_terms: D000368:Aged; D003128:Coma / Q000175:diagnosis* / Q000503:physiopathology*; D003243:Consciousness / Q000502:physiology*; D004569:Electroencephalography; D005072:Evoked Potentials, Auditory / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011379:Prognosis
keywords: Auditory-evoked potentials; Awakening; Cardiac arrest; Coma; Consciousness