Abstract 91: Failure of Propranolol and Epinephrine Combination to Improve Resuscitability and Short-Term Survival in a Rat Model of Ventricular Fibrillation.
Introduction: We have previously reported no benefits associated with early administration of epinephrine (EPI) during resuscitation from VF. EPI stimulation of α1 and β-adrenergic receptors has been shown to increase the severity of myocardial ischemic injury.
Hypotheses: We investigated whether administration of propranolol (PRO) concomitantly with EPI mitigates adverse effects of EPI enabling early drug administration to improve resuscitability and short-term survival in a rat model of VF and closed-chest resuscitation.
Methods: Three groups of 6 rats each underwent 10 mins of untreated VF followed by 8 mins of chest compression (CC) before attempting defibrillation. Rats were randomized to receive a combination of PRO (0.4 mg/kg) and EPI (0.02 mg/kg) into the right atrium immediately before CC (PRO + EPI0-mins), at 3 min of CC (PRO + EPI3-mins), or at 6 min of CC (PRO + EPI6-mins). Depth of compression was titrated to achieve an aortic diastolic pressure between 26 and 28 mmHg in the absence of EPI and between 34 and 36 mmHg in the presence of EPI.
Results: Five of 6 animals in each treatment group were successfully resuscitated without differences in 240-min survival. Moreover, no improvement in survival was evident when compared to our previously reported EPI series (Figure⇓).
Conclusions: In this model of VF and closed-chest resuscitation early administration of PRO + EPI did not improve resuscitability or short-term survival. Further work is required to understand the mechanisms underlying the lack of beneficial effects associated with β-adrenergic blockade in our model.