title: Comparison of neurological outcomes following witnessed out-of-hospital ventricular fibrillation defibrillated with either biphasic or monophasic automated external defibrillators.
abstract: BACKGROUND
  Biphasic waveform defibrillation results in higher rates of termination of fibrillation than monophasic waveform defibrillation but has not been shown to improve survival outcomes.
  
  
  OBJECTIVE
  To compare the effectiveness of a biphasic automated external defibrillator (AED) with a monophasic AED for witnessed out-of-hospital cardiac arrest (OHCA) due to ventricular fibrillation (VF).
  
  
  METHODS
  In a prospective population-based cohort study, adults with witnessed VF OHCA were treated with either monophasic or biphasic waveform AED shocks. The primary outcome measure was neurologically favourable 1-month survival, defined as a Cerebral Performance Categories score of 1 or 2.
  
  
  RESULTS
  Of 366 adults with witnessed OHCA of presumed cardiac aetiology, 74 (20%) had VF. Termination of VF with the first shock tended to occur more frequently after biphasic AED shocks (36/44 (82%) vs 20/30 (67%), p = 0.14). Return of spontaneous circulation (ROSC) occurred more frequently after biphasic AED shocks (29/44 (66%) vs 8/30 (27%), p = 0.001). Neurologically favourable 1-month survival was also more frequent in the biphasic group (10/44 (23%) vs 1/30 (3%), p = 0.04). The median time interval from the first shock to the second shock was 67 s in the monophasic group and 24 s in the biphasic group (p = 0.001).
  
  
  CONCLUSIONS
  Treatment with biphasic AED shocks improved the likelihood of ROSC and neurologically favourable 1-month survival after witnessed VF compared with monophasic AED shocks. In addition to waveform differences, a shorter time interval from the first shock to the second shock could account for the better outcomes with biphasic AED.
authors: Department of Traumatology and Acute Critical Medicine, Osaka University Graduate School of Medicine, Suita 5430035, Japan. kajihanapu@yahoo.co.jp
authors: K
authors: K
authors: Kajino
authors: T
authors: T
authors: Iwami
authors: R A
authors: RA
authors: Berg
authors: A
authors: A
authors: Hiraide
authors: Y
authors: Y
authors: Hayashi
authors: H
authors: H
authors: Yukioka
authors: H
authors: H
authors: Tanaka
authors: T
authors: T
authors: Shimazu
authors: H
authors: H
authors: Sugimoto
mesh_terms: D000328:Adult; D000368:Aged; D016887:Cardiopulmonary Resuscitation / Q000706:statistics & numerical data; D015331:Cohort Studies; D047548:Defibrillators; D004554:Electric Countershock / Q000706:statistics & numerical data*; D004632:Emergency Medical Services; D005260:Female; D006323:Heart Arrest / Q000628:therapy*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009422:Nervous System Diseases / Q000209:etiology*; D011446:Prospective Studies; D016896:Treatment Outcome; D014693:Ventricular Fibrillation / Q000628:therapy*