Abstract P24: Perfluorocarbon-Induced Intra-Arrest Hypothermia Does Not Improve Survival in a Swine Model of Asphyxial Cardiac Arrest/Pulseless Electrical Activity
Background Pulseless electrical activity (PEA) is an important cause of cardiac arrest in pediatric and adult populations. Induction of rapid intra-arrest hypothermia improves resuscitation success in experimental models of ventricular fibrillation (VF) cardiac arrest. Our purpose was to determine if rapid induction of hypothermia with a cold perfluorocarbon (PFC)-based total liquid ventilation (TLV) system would also improve resuscitation in a swine model of asphyxial cardiac arrest/PEA.
Methods Twenty swine were randomly assigned to control (C, no ventilation, n=11) or TLV with precooled (2°C) PFC (n=9) groups. Asphyxia was induced by insertion of a rubber stopper into the endotracheal tube (ET). The asphyxial phase was continued in both groups until the loss of aortic pulsations (LOAP) was reached, defined as a pulse pressure less than 2mmHg. The TLV animals underwent asphyxial arrest for an additional 2 minutes after LOAP, followed by 3 minutes of PFC induced hypothermia, prior to starting CPR. The cold PFCs were preoxygenated for 2 minutes. The C animals underwent 5 minutes of post-LOAP asphyxia. Both groups then underwent CPR for at least 11 minutes or until success improbable. The endpoint of resuscitation was the resumption of spontaneous circulation (ROSC), defined as an unassisted peak systolic arterial pressure > 60 mmHg maintained for 10 minutes.
Results All 20 animals demonstrated PEA at the end of the asphyxial phase. Seven of 9 animals achieved ROSC in the TLV group vs. 5 of 11 in the C group (p=0.2). The mean pulmonary arterial (PA) temperature was lower in TLV animals starting 4 minutes after induction of hypothermia (TLV 36.3 ± SE 0.18 vs. C 38.1±0.16°C, p<0.0001). This PA temperature difference was sustained for the remainder of the CPR phase. Arterial pO2 was higher in TLV animals at 2.5 minutes of CPR (TLV 76±12 vs. C 44±2 mmHg; p=0.03). Mean coronary perfusion pressure during CPR (TLV 9.8±1.9 vs. C 9.7±1.4mmHg) did not differ between the two groups.
Conclusion Induction of moderate hypothermia using PFC-based TLV did not improve ROSC success in this swine model of asphyxial cardiac arrest/PEA, unlike prior VF arrest models. Greater depth and/or duration of hypothermia might yield better results.