Abstract P130: Limits of Resuscitation From Prolonged Cardiac Arrest Under Optimal Reperfusion Conditions With Cardiopulmonary Bypass
Background: Cardiac arrest in the out-of-hospital setting often goes untreated for long durations, whilst pathophysiological mechanisms progress. It is not known whether there is a duration of cardiac arrest after which resuscitation is physiologically impossible. We sought to examine the effect of very long durations of cardiac arrest on resuscitation outcomes under optimal laboratory conditions.
Objective: Explore the duration of cardiac arrest after which the heart cannot be resuscitated.
Methods: Twelve domestic mixed breed swine (27.1kg +/−2.3kg) were sedated, anaesthetized and paralyzed. Mechanical ventilation with room air was provided. Pressure transducing catheters were placed in the right atrium and aorta via left side femoral cutdown. Large diameter bypass catheters were placed in the right external jugular vein and right femoral artery for bypass outflow and inflow, respectively. Ventricular fibrillation (VF) was induced with a 3-second 100mA transthoracic shock. VF was left untreated for 15, 20, 25, or 30 minutes, followed by cardiopulmonary bypass with a centrifugal pump bypass system (Bard CPS). After 10 minutes of bypass reperfusion, defibrillation was attempted at 1 minute intervals, contingent on ECG rhythm, until return of spontaneous circulation (ROSC) or 20 minutes of unsuccessful resuscitation.
Results: Three animals were assigned to each VF duration group. All animals in the 15 minute group achieved ROSC. Two animals in the 20 minute group and 1 animal in the 25 minute group achieved ROSC. No animals enduring 30 minutes of untreated VF were successfully resuscitated.
Conclusion: In this preliminary study, 25 minutes of untreated ventricular fibrillation was the limit for resuscitation under optimal reperfusion conditions. Ten minutes of bypass reperfusion may be inadequate when VF is greater than 25 minutes.