Abstract 16: A Metabolic Model of Pulseless Electrical Activity
Introduction: Resuscitation research may not translate well to the clinical arena because pre-clinical cardiac arrest research often uses a ventricular fibrillation (VF) model while a majority of patients present with pulseless electrical activity or asystole (PEA/A). A large fraction of these patients have respiratory symptoms prior to arrest and are likely to be hypoxic. In order to model the pathophysiology leading to PEA/A, we studied a model of cardiac arrest with a long prodromal period without VF induction.
Methods and Results: Six anesthetized swine, 31±2.6 kg, were instrumented for electrocardiogram, aortic pressure measurement, and arterial blood gas sampling. After baseline measurements, ventilation gas was switched from 100% oxygen to a mixture of 12% oxygen and 88% nitrogen. Six minutes following loss of aortic pulsations (pulse pressure < 2 mmHg), mechanical chest compressions (100/min) and ventilations (10/min, 100% O2) were started. Arterial oxygen saturation (%O2) dropped from 99.8+0.1 percent at baseline to 42.5+12.6 percent after 30 minutes of the hypoxic gas mixture with a minimum of 37.4+18 %O2 in the last sample drawn prior to PEA/A. Aortic systolic pressure was maintained >60 mm Hg for 291±129 minutes. Systolic aortic pulse pressure <2 mm Hg occurred at 299±123 minutes after beginning the hypoxic gas mixture. Arterial pH, base excess (BE), and serum glucose decreased progressively (Base pH 7.514+0.06 vs. pre-arrest 7.171+0.113, P<0.05; BE 7+2 vs. -14+6, P<0.05; glucose 100+20 vs. 46+12, P>0.05). Two of 6 animals had return of spontaneous circulation during resuscitation.
Conclusion: This model of cardiac arrest with a long prodromal period allows study of resuscitation and post-resuscitation physiology in animals that resembles a portion of the PEA/A arrest population who suffer from hypoxic respiratory failure. A better understanding of these patients may lead to more focused and effective treatments.
- © 2011 by American Heart Association, Inc.