title: Comparison of shock-first strategy and cardiopulmonary resuscitation-first strategy in a porcine model of prolonged cardiac arrest.
abstract: OBJECTIVE
  The choice of a shock-first or a cardiopulmonary resuscitation (CPR)-first strategy in the treatment of prolonged cardiac arrest (CA) is still controversial. The purpose of this study was to compare the effects of these strategies on oxygen metabolism and resuscitation outcomes in a porcine model of 8min CA.
  
  
  METHODS
  Ventricular fibrillation (VF) was electrically induced. After 8min of untreated VF, 24 male inbred Wu-Zhi-Shan miniature pigs were randomized to receive either defibrillation first (ID group) or chest compression first (IC group). In the ID group, a shock was delivered immediately. If the defibrillation attempt failed to attain restoration of spontaneous circulation (ROSC), manual chest compressions were rapidly initiated at a rate of 100compressionsmin(-1), and the compression-to-ventilation ratio was 30:2. If VF persisted after five cycles of CPR, a second defibrillation attempt was made. In the IC group, chest compressions were delivered first, followed by a shock.
  
  
  RESULTS
  Hemodynamic variables, the VF waveform and blood gas analysis outcomes were recorded. Oxygen metabolism parameters and the amplitude spectrum area (AMSA) of the VF waveform were computed. There were no significant differences in the rate of ROSC and 24h survival between two groups. The ID group had lower lactic acid levels, higher cardiac output, better oxygen consumption and better oxygen extraction ratio at 4 and 6h after ROSC than the IC group.
  
  
  CONCLUSIONS
  In a porcine model of prolonged CA, the choice of a shock-first or CPR-first strategy did not affect the rate of ROSC and 24h survival, but the shock-first strategy might result in better hemodynamic status and better oxygen metabolism than the CPR-first strategy at the first 6h after ROSC.
authors: Emergency Department of Beijing Chaoyang Hospital, Capital Medical University, 8# Baijiazhuang Road, Chaoyang District, Beijing 100020, China.
authors: Zhi-Jun
authors: ZJ
authors: Guo
authors: Chun-Sheng
authors: CS
authors: Li
authors: Wen-Peng
authors: WP
authors: Yin
authors: Xiao-Min
authors: XM
authors: Hou
authors: Wei
authors: W
authors: Gu
authors: Da
authors: D
authors: Zhang
mesh_terms: D000818:Animals; D016887:Cardiopulmonary Resuscitation; D004195:Disease Models, Animal; D004554:Electric Countershock; D006323:Heart Arrest / Q000628:therapy*; D008297:Male; D013552:Swine; D013997:Time Factors