Abstract 279: Increasing CPR Duration Prior To First Defibrillation Does Not Improve ROSC Or Survival In A Swine Model Of Prolonged Ventricular Fibrillation
Introduction: The optimum duration of cardiopulmonary resuscitation (CPR) prior to first rescue shock is not known. Clinical trials have used 90s and 180s. Neither of these durations may be optimal. We sought to determine the optimum duration of CPR prior to the first defibrillation attempt and whether this varied depending on the duration of ventricular fibrillation (VF). In this porcine model of basic life support, our outcomes were rates of return of spontaneous circulation (ROSC), survival, and coronary perfusion pressure (CPP).
Methods: We anesthetized and instrumented 45 swine and then induced VF. After 5 or 8 minutes of untreated VF, we randomized the swine to mechanical CPR for 90, 180, or 300s. A single rescue shock (150J biphasic) was then administered. If this shock failed, 2 minutes of mechanical CPR were completed prior to the next rescue shock. CPP was calculated for each 30 second epoch. ROSC was defined as a blood pressure >80mmHg sustained for 60s. Survival was defined as sustained ROSC for 20 minutes. Data were analyzed with Fisher’s exact test and ANOVA.
Results: In the 5 minute VF group, the rate of ROSC did not differ between the three groups (90s: 25%; 180s: 38%; 300s: 38%, p>.05) Survival rates did not differ (90s: 25%; 180s: 25%; 300s: 25%, p>0.05). In the 8 minute VF group, no animals experienced ROSC or survival. CPP are presented by 30 second epoch in the figure and did not differ between the three groups (p>0.05). CPPs decline after 180s of CPR.
Conclusions: ROSC and survival were equivalent regardless of VF duration and CPR duration. When CPR begins late, CPPs are low, stressing the importance of early CPR. We do not recommend 300s of CPR unless a defibrillator is unavailable.