Abstract 270: Developing a Ventricular Fibrillation Cardiac Arrest Rat Model - Pitfalls and Challenges

Abstract

Introduction: The ideal rodent model of ventricular fibrillation (VF) cardiac arrest (CA) produces consistent histologic and neurologic damage as target for novel therapies and shows a high survival rate to minimize animal use and allow for long term outcome. VF induction, chest compressions and ventilation are crucial techniques and published in many variants in literature. We report our experiences during model development. Materials and Methods: A non-randomized cohort study evaluating different methods of VF induction, chest compressions techniques, mechanical ventilation and defibrillation was performed with regards to it’s feasibility, complications, ROSC rate and survival. Results: Male Sprague-Dawley rats (350g, anesthetised, instrumented) underwent VF induction with 2 min endocardial fibrillation via a transjugular neonatal pacing catheter with minimal current use, low incidence of autodefibrillation and good resuscitability. Mechanical chest compressions with approx. 30% of thorax diameter depth were applied with a pneumatic thumper 200/min placed mid-sternally, tilted upwards. Strong fixation with tapes avoided throrax-instability. Epinephrine (20μg/kg) and NaHCO3 (1mmol/ kg) were administered before CPR start and epinephrine repeatedly given after defibrillations every 2min. For defibrillations (5J, biphasic) modified paediatric defi pads were used. ROSC was achieved in 7/10 animals in a 6 min CA group and 6/11 in a 8 min CA group. CPR time was 2.6±1.0 min (mean±SD), number of defibrillations needed 2±1 and a cumulative epinephrine dose of 46±10 μg/kg with no differences between groups. Conclusions: Researchers developing a VF CA model are facing a multitude of difficulties, a lack of data on model development and many variations published in literature, often without detailed description. We developed a CPR rat model for VF CA with graded cognitive deficits and long-term survival. We propose detailed description of model development, including ineffective methods, to facilitate experience exchange between research groups, to avoid that future experimental groups repeat possible mistakes.