RESUSCITATION AFTER PROLONGED CARDIAC ARREST

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Cardiac resuscitation is contingent on prompt restoration of myocardial perfusion with reestablishment of aerobic myocardial metabolism. With conventional techniques of closed-chest CPR, the time available for reversing "sudden death" by restoration of myocardial perfusion is typically limited to approximately 8 minutes. After 8 minutes, resuscitability and long term survival are remote. This application addresses options for improving myocardial resuscitability and long term outcome after prolonged cardiac arrest. We propose to compare extracorporeal pump oxygenation (ECPO) utilizing femoral artery and jugular vein access and internal cardiac massage (ICM) after thoracotomy as interventions for cardiac resuscitation after 10, 15 and 20 minutes of clinical death in an animal model. A well established porcine model is utilized in which ventricular fibrillation is induced. We have previously demonstrated resuscitation and 48-hour survival with return of critical function in this model when ECPO was started after an interval of 15 min of circulatory arrest. Three sets of experiments are planned in which VF is maintained for either 10, 15 or 20 minutes without intervention. Failing to restore circulation after external countershock, either ICM or ECPO is utilized. We anticipate that ECPO will provide more optimal systemic and myocardial blood flow, greater resuscitability, greater 48-hour survival, and better neurological outcome than internal cardiac massage. When the duration of clinical death is prolonged from 10 to 15 and subsequently to 20 minutes, such differences in effectiveness are likely to be magnified. As an important part of this study, we anticipate that the end-tidal carbon dioxide tension (P which correlates closely with pulmonary blood flow and therefore cardiac CPR, serves as a noninvasive monitor for guiding both initiation and discontinuation of these advanced life support techniques. These studies are intended to serve as the basis for planning clinical evaluation of ECPO (and possibly ICM) for the management of patients who sustain prolonged cardiac arrest and who cannot be successfully resuscitated by conventional methods of closed chest cardiac compression. We plan to establish objective measurements and especially noninvasive PETC02 monitoring to guide appropriate selection and timing of either or both ICM and ECPO interventions.