• K Kajino, T Iwami, R A Berg, A Hiraide, Y Hayashi, H Yukioka, H Tanaka, T Shimazu, and H Sugimoto.
• Department of Traumatology and Acute Critical Medicine, Osaka University Graduate School of Medicine, Suita 5430035, Japan. kajihanapu@yahoo.co.jp
• Emerg Med J. 2009 Jul 1;26(7):492-6.

BackgroundBiphasic waveform defibrillation results in higher rates of termination of fibrillation than monophasic waveform defibrillation but has not been shown to improve survival outcomes.ObjectiveTo 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).MethodsIn 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.ResultsOf 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).ConclusionsTreatment 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.

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