AIM

The objectives of this study were to assess the return of spontaneous circulation rates and hemodynamic response of large swine (>65Kg) during cardiopulmonary resuscitation after nontraumatic cardiac arrest using the COBRA-OS® aortic occlusion balloon and to address limitations of large swine closed-chest cardiopulmonary resuscitation by comparing closed-chest vs. open-chest cardiopulmonary resuscitation.

METHODS

Yorkshire pigs ( = 10) weighing >65 kg were anesthetized and ventilated. After 7 min of untreated ventricular fibrillation (VF), animals were randomized to receive mechanical closed-chest cardiopulmonary resuscitation or open-chest cardiac massage. Following a 5-minute low-flow state, advanced cardiac life support algorithms were started and the COBRA-OS® was inflated in the thoracic aorta. Animals that achieved return of spontaneous circulation were re-started on mechanical ventilation and medications, CPR, defibrillation, and aortic occlusion were discontinued. The primary outcome was return of spontaneous circulation and secondary outcomes were mean arterial pressures generated in the low flow and aortic occlusion states before return of spontaneous circulation. Groups were compared with a -test or Mann-Whitney test for normal and non-parametric data, respectively, while categorical data was compared with the chi square test.

RESULTS

Return of spontaneous circulation was obtained in 4 animals (80%) in the open cardiac massage group and none in the mechanical closed-chest CPR group ( < 0.05). The COBRA-OS® successfully occluded all aortas and animals experienced higher mean arterial pressures in both groups with aortic occlusion (median 15 mm Hg, IQR 13-23 mm Hg), but with a higher MAP difference in the open cardiac massage group (-12.2 mm Hg, [-2.581, -21.819]).

CONCLUSIONS

Consideration should be given to intra-thoracic cardiac massage to increase cardiopulmonary resuscitation effectiveness and therefore return of spontaneous circulation rates in large (>65 kg) swine models of nontraumatic cardiac arrest. The COBRA-OS® demonstrated feasibility for use in this model.The Keenan Research Center, Li Ka Shing Knowledge Institute of St. Michael's Hospital Animal Care Committee: ACC Protocol #726.