Precountershock cardiopulmonary resuscitation improves initial response to defibrillation from prolonged ventricular fibrillation: A randomized, controlled swine study*

OBJECTIVES: To compare immediate countershocks (defibrillation 1st) with precountershock cardiopulmonary resuscitation (CPR 1st) for prolonged ventricular fibrillation (VF). DESIGN: Randomized, controlled trial. SETTING: University animal laboratory. SUBJECTS: Thirty swine (27 +/- 1 kg). INTERVENTIONS: After 8 mins of untreated ventricular fibrillation, swine were randomly assigned to receive either immediate countershocks or CPR for 90 secs followed by countershocks. MEASUREMENTS AND MAIN RESULTS: After the first set of shocks, nine of 15 CPR 1st animals attained return of spontaneous circulation vs. 0 of 15 defibrillation 1st animals (p <.001), and pulseless electrical activity occurred in only one of 15 CPR 1st animals vs. ten of 15 defibrillation 1st animals (p <.01). The ultimate outcomes in the two groups were not different: Return of spontaneous circulation and 24-hr survival occurred in 15 of 15 CPR 1st and 13 of 15 defibrillation 1st animals. Good neurologic outcome at 24 hrs occurred in 12 of 15 CPR 1st and nine of 15 defibrillation 1st animals. None of the animals was successfully resuscitated with defibrillation alone; all successfully resuscitated animals were provided with chest compressions during the resuscitation. The ventricular fibrillation median frequency by fast Fourier transformation decreased during the untreated ventricular fibrillation interval in both groups (9.7 +/- 0.3 Hz and 10.1 +/- 0.2 Hz after 1 min vs. 8.8 +/- 0.3 Hz and 8.9 +/- 0.5 Hz at 8 mins, respectively). Because the ventricular fibrillation median frequency substantially increased after CPR 1st, it was much higher in the CPR 1st group before the first shock (15.1 +/- 0.9 Hz vs. 8.9 +/- 0.5 Hz, p <.001). The ventricular fibrillation median frequency before the first countershock was much higher in the animals that attained return of spontaneous circulation after the first set of shocks vs. those that did not (16.1 +/- 1.3 Hz vs. 10.0 +/- 0.6 Hz, p <.0001) CONCLUSIONS: Precountershock CPR can result in substantial physiologic benefits and superior response to initial defibrillation attempts compared with immediate defibrillation in the setting of prolonged ventricular fibrillation.