Metabolic evidence of inadequate coronary blood flow during closed-chest resuscitation in dogs

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Abstract
Closed-chest cardiopulmonary resuscitation (CPR) produces only small pressure differences across the coronary circulation and relatively little coronary blood flow in dogs with ventricular fibrillation. To determine whether coronary flow during experimental resuscitation is sufficient to maintain aerobic myocardial metabolism, we measured left ventricular adenosine triphosphate (ATP) and lactate concentrations before and immediately after a 20 min period of CPR in six fibrillating dogs. The mean aortic-right atrial pressure difference generated during CPR averaged 5.4 ± 2.6 mmHg (SEM) and 3.2 ± 2.6 mmHg at the beginning and end of the 20 min period, respectively. Left ventricular myocardial blood flow (measured with radioactive microspheres) averaged 16.7 ± 5.7% of prearrest values during the first 10 min of CPR, and 8.5 ± 4.8% of prearrest values during the second 10 min of CPR. Biopsies after CPR contained less ATP (3.3 ± 0.1 vs 4.7 ± 0.5 nmol·mg-1, pvs 1.9 ± 0.2 nmol·mg-1, p<0.01) than control biopsies. We conclude that coronary blood flow during CPR is inadequate relative to myocardial oxygen demands during ventricular fibrillation in dogs. The techniques developed in this study provide a potential means of assessing the effects of experimental interventions on myocardial oxygenation during CPR.