The Effects of Methoxamine and Epinephrine on Survival and Regional Distribution of Cardiac Output in Dogs with Prolonged Ventricular Fibrillation

This study compares the effects of methoxamine, a pure α1-agonist, and epinephrine on cerebral and myocardial blood flow, central hemodynamics, and survival in a randomized placebo-controlled fashion during prolonged ventricular fibrillation (VF) in a canine model. Twenty-four anesthetized and ventilated adult mongrel dogs were instrumented for regional blood flow determinations using radio-labeled microspheres. The dogs were randomized to receive either 20 mg of methoxamine as a single intravenous bolus or repeated boluses of 0.02 mg/kg of epinephrine, 0.2 mg/kg of epinephrine, or normal saline solution placebo beginning at three minutes following induction of VF and initiation of closed chest cardiac massage (CCCM). Organ blood flow measurements were determined during normal sinus rhythm and after five and 20 minutes of VF. All six dogs receiving methoxamine were successfully resuscitated in contrast to only one in each of the epinephrine-treated groups and none of the dogs receiving placebo (p