Abstract 16996: Controlled Pauses (“Stutter”) CPR Did Not Improve ROSC or 4-hour Survival in a Porcine Model of VF-induced Cardiac Arrest

Abstract

Introduction: Ischemic post-conditioning (IPC) has shown promise in mitigating ischemia-reperfusion injury. Controlled pauses during CPR (CP-CPR) following cardiac arrest (CA) and prolonged downtime may help invoke IPC mechanisms and have been shown to improve neurological outcome in swine. We tested whether CP-CPR would improve return of spontaneous circulation (ROSC) and/or 4-hr survival rates, compared with standard CPR from a mechanical chest compression device (M-CPR), following prolonged downtime in a porcine model of ventricular fibrillation (VF)-induced CA. Methods: Twenty anesthetized and instrumented pigs were block randomized to two protocols. Following 10 min of VF, mechanical CPR was initiated (100 comp/min, 50% duty cycle, 2 inch depth). Over the first 5 minutes of CPR, the M-CPR protocol group received continuous chest compressions, while the CP-CPR protocol included four 20-sec pauses in compressions starting at 40, 100, 160, and 220 sec. All other interventions were the same in the two groups. After 5 minutes, a first shock was delivered during a pause. If the shock failed to convert to a perfusing rhythm for ≥ 30 s with a systolic aortic pressure (sAoP) ≥ 50 mmHg for at least the first three contiguous sAoP values, CPR was continued in 2 min cycles, followed by a shock (if indicated) at the end of each cycle, for up to 10 cycles. As soon as these criteria were met between two CPR cycles, ROSC was documented and a post-resuscitation protocol was initiated. During the post-resuscitation protocol, inotropic agents were provided as needed to maintain sAoP ≥ 50 mmHg. Survival was declared if the sAoP was maintained above threshold for 4 hrs following ROSC. Results: Nineteen animals were successfully instrumented for data gathering (9 CP-CPR, 10 M-CPR). In the CP-CPR and M-CPR groups respectively, 3/9 (33%) vs. 5/10 (50%) achieved ROSC (p = 0.46); when ROSC was achieved, time to ROSC was 7.7±1.2 min vs. 5.8±1.1 min (p = 0.08). All animals that achieved ROSC survived to 4 hours. Conclusions: In a porcine model of CA following prolonged VF, CP-CPR did not improve ROSC or 4-hr survival. The trend towards delayed time to ROSC suggests controlled pauses may impair initial resuscitation, even if they ultimately improve neurological outcome. Further studies are warranted.