Abstract Sun801: A Porcine Model of Cardiac Arrest Without Pre-Arrest Fluid Loading, Sternal Molding, or Epinephrine

Abstract

Introduction: A large fraction of investigators studying cardiac arrest use piston-based sternal compression CPR ( PBSC-CPR ). Many use one or more of (1) pre-arrest fluid loading, (2) “sternal molding,” or (3) intra-arrest epinephrine as adjuncts to enhance hemodynamics and achieve return of spontaneous circulation ( ROSC ). In contrast to PBSC-CPR, circumferential constriction CPR ( CC-CPR ) applies more motive force to the chest and does not damage thoracic skeletal structures that may facilitate recoil-based venous return. When used as a model system, CC-CPR may not require the commonly used therapeutic adjuncts. Hypothesis: CC-CPR may not require pre-arrest fluid loading, “sternal molding,” or intra-arrest epinephrine to achieve indicators of hemodynamics associated with ROSC. Methods: Retrospective observational report of multiple porcine studies. Ventricular fibrillation was induced in female Yorkshire swine (n = 8, 30 kg). CPR was provided by a prototype pneumatic CC-CPR device. CC-CPR was alternated in 45-second epochs between varying constriction rates (60, 80, 100, 120/min) and duty cycles (30-50%). CPR was performed for 20 minutes. No epinephrine was administered for the first ten minutes of arrest. No “sternal molding” or similar mechanical conditioning was performed. Some animals received pre-arrest fluid loading to raise the right atrial ( RA ) pressure to 5mmHg. Aortic ( Ao ) and RA pressures were measured by micromanometer catheters, and coronary perfusion pressure ( CPP ) was derived. Pressures were noted at the beginning of each epoch for the first 10 minutes of each experiment. Mean pressures in animals with and without fluid loading were evaluated by paired t-tests. Skeletal injuries were evaluated at postmortem. Results: During the first 10 minutes of resuscitation, CPP in both groups was above the standard threshold for ROSC (CPP ≥ 15) (Figure). No hemodynamic indicators were statistically different, although there was a slight trend toward higher RA and lower CPP in animals which received pre-arrest fluid loading. Only one thoracic skeletal fracture was noted. Conclusion: In this preliminary series, CC-CPR appeared to achieve perfusion pressures predictive of ROSC without any of the adjuncts commonly used with PBSC-CPR. Because each of the PBSC-CPR adjuncts may be associated with a degree of harm, CC-CPR may be an attractive method for both animal models and human clinical resuscitation.