title: Precountershock cardiopulmonary resuscitation improves ventricular fibrillation median frequency and myocardial readiness for successful defibrillation from prolonged ventricular fibrillation: a randomized, controlled swine study.
abstract: OBJECTIVE
  After prolonged ventricular fibrillation (VF), precountershock cardiopulmonary resuscitation (CPR) will improve myocardial "readiness" for defibrillation compared with immediate defibrillation.
  
  
  METHODS
  After 10 minutes of untreated VF, 32 swine (27+/-1 kg) were randomly assigned to receive immediate countershocks (DEFIB), CPR for 3 minutes followed by countershocks (CPR), or CPR for 3 minutes plus intravenous epinephrine followed by countershocks (CPR+EPI). VF waveform was evaluated by fast Fourier transformation.
  
  
  RESULTS
  VF amplitude and median frequency by fast Fourier transformation decreased during the untreated VF interval in all groups, and the median frequency subsequently increased during each minute of precountershock CPR. Although the VF median frequency in the 3 groups did not differ after 10 minutes of untreated VF (8.9+/-0.8 Hz versus 8.4+/-0.5 Hz versus 7.3+/-0.5 Hz, respectively), immediately before the first shock the VF median frequency was much lower in the DEFIB group than in either the CPR or CPR+EPI groups (8.9+/-0.8 Hz versus 13.1+/-0.8 Hz versus 13.8+/-0.9 Hz, respectively; P <.01). None of the 10 animals in the DEFIB group attained return of spontaneous circulation after the first set of shocks versus 5 of 10 animals in the CPR group and 6 of 12 animals in the CPR+EPI group (DEFIB versus each CPR group; P <.05). Cardiac output 1 hour after resuscitation was substantially worse in the DEFIB group than in the CPR or CPR+EPI groups (74+/-7 mL/kg per minute versus 119+/-7 mL/kg per minute versus 104+/-15 mL/kg per minute; P <.05).
  
  
  CONCLUSIONS
  Precountershock CPR can result in substantial physiologic benefits compared with immediate defibrillation in the setting of prolonged VF. Moreover, these benefits can be attained with or without the addition of intravenous epinephrine.
authors.affiliation: Steele Memorial Children's Research Center and the Department of Pediatrics, University of Arizona College of Medicine, Tucson 85724-5073, USA. rberg@peds.arizona.edu
authors.forename: Robert Allen
authors.initials: RA
authors.lastname: Berg
authors.forename: Ronald Willard
authors.initials: RW
authors.lastname: Hilwig
authors.forename: Karl B
authors.initials: KB
authors.lastname: Kern
authors.forename: Gordon Allen
authors.initials: GA
authors.lastname: Ewy
mesh_terms: D000818:Animals; D016887:Cardiopulmonary Resuscitation / Q000379:methods*; D004554:Electric Countershock / Q000379:methods*; D004837:Epinephrine / Q000627:therapeutic use; D013552:Swine; D013566:Sympathomimetics / Q000627:therapeutic use; D014693:Ventricular Fibrillation / Q000188:drug therapy / Q000628:therapy*
chemical_list: D013566:Sympathomimetics; D004837:Epinephrine