Abstract 191: Mechanical Postconditioning with Chest Compression Pauses at the Initiation of CPR Prevents Neurological Dysfunction at 24 Hours in Pigs After 15 Minutes of Untreated Ventricular Fibrillation

Abstract

Background: Mechanical post conditioning (PC) with intermittent initiation of flow (“stutter” reperfusion) has been shown to decrease infarction size in ST elevation infarction and decrease ischemic stroke size in animals. We hypothesize that when using sodium nitroprusside-enhanced cardiopulmonary resuscitation (SNPeCPR) mechanical post conditioning with stutter CPR (20-second CPR pauses), begun immediately on SNPeCPR initiation, will improve 24-hour cerebral function compared to 12 hours of therapeutic hypothermia (TH) post resuscitation. Methods: 14 anesthetized and intubated pigs underwent 15 minutes of untreated VF followed by 5 minutes of SNPeCPR comprised of active compression decompression CPR plus an inspiratory impedance threshold device combined with abdominal binding. 2 mg of sodium nitroprusside (SNP) were given IV at minute 1 and 1 mg at minute 3 of CPR. All animals received in addition 0.5 mg of epinephrine at minute 5, 30 seconds before the first defibrillation attempt. Six animals (PC group), were treated with 40 seconds of SNPeCPR and the first dose of SNP, then followed by 20-second pauses (cessation of perfusion) and 20 seconds of SNPeCPR with a total of 4 cycles for up to 3 minutes. After that, animals had uninterrupted SNPeCPR until defibrillation at minute 5. The other 8 animals (TH group) had SNPeCPR for a total of 5 minutes without interruptions. The TH group received 12 hours of TH (core temp=33°C). The PC group received no TH. Cerebral performance category (CPC) was scored at 24 hours by a veterinarian blinded to the treatment group. Results: During SNPeCPR, there were no hemodynamic differences except for a significantly higher aortic pressure response to epinephrine at min 5 (SBP/DBP; 148±12/78±7 in the PC group versus 110±9/62±5 mmHg in the TH group, p<0.05). Both groups had 100% return of spontaneous circulation rates and 24-hour survival. CPC was significantly lower in the PC group (1±0 = normal) versus the TH group (2.4±0.8 = mild to moderate disability), p<0.01. Conclusion: In this porcine model of cardiac arrest and SNPeCPR, mechanical PC with pauses in compressions at the initiation of the resuscitation efforts prevented 24-hour neurological dysfunction after 15 minutes of untreated VF and was superior to TH.