Introduction: Extracorporeal cardiopulmonary resuscitation (ECPR) is a feasible and effective resuscitation strategy for refractory cardiac arrest, but often fails to restore heart and brain function. Intravascular coagulation (IC) contributes to the “no-reflow phenomenon”, which is a potential cause of organ failure after prolonged cardiac arrest.
Hypothesis: The goal of this study was to assess if early administration of unfractionated heparin during prolonged cardiac arrest (CA) mitigates IC and improves recovery of cardiac and neurologic function with ECPR.
Methods: Ten healthy pigs (45±5 Kg) were instrumented under general anesthesia for cardiovascular monitoring, intracranial pressure (ICP), urine output, cortical EEG and somatosensory evoked potentials (SSEPs). Ventricular fibrillation cardiac arrest was electrically induced and remained untreated for 8 minutes followed by 4 minutes of manual CPR and 33 minutes of mechanical CPR. Animals were randomized to receive an intravenous bolus of unfractionated heparin (200 units/Kg) or placebo 8 minutes after onset of VF. ECPR was initiated after 45 minutes of cardiac arrest via cannulas placed in the femoral vessels and the cephalic vein. Animals were maintained on ECPR for up to 24 hours or until ongoing resuscitation was deemed futile based on predetermined criteria. Primary outcomes were recovery of heart function based on echocardiography and brain function based on EEG and SSEPs.
Results: Recovery of heart function following defibrillation during ECPR occurred in 1/5 animals in the placebo group and 0/5 animals in the heparin group. Quantitative EEG and SEEP analysis revealed no recovery of brain activity in either group. Mean lactate levels increased significantly during CPR and the first 2 hours of ECPR, but were not statistically different between groups (19.4±4.7 placebo vs. 19.8±3.1 heparin after 2 hours of ECPR (p>0.05)). ICP was also increased during ECPR with a trend toward a greater increase after early intra-arrest heparin (15.4±7.5 placebo vs. 32.6±28.5 heparin after 4 hours of ECPR (p>0.05)).
Conclusion: Overall, we were unable to detect a beneficial effect of early intra-arrest heparin therapy in this swine model of prolonged refractory cardiac arrest treated with ECPR.