Evidence favoring the use of an alpha2-selective vasopressor agent for cardiopulmonary resuscitation

Abstract

Background: Both alpha1- and beta-adrenergic agonists increase the severity of global myocardial ischemic injury. We hypothesized that combined beta- and alpha1-adrenergic blockade would improve initial resuscitation and postresuscitation myocardial and neurological functions. We further hypothesized that the resulting alpha2-actions of relatively brief duration would favor improved functions compared with the more prolonged effect of nonadrenergic vasopressin.

Methods and results: Three groups of 5 male domestic pigs weighing 37+/-3 kg were investigated. Ventricular fibrillation was untreated for 7 minutes before the start of precordial compression, mechanical ventilation, and attempted defibrillation. Animals were randomized to receive central venous injections of equipressor doses of (1) epinephrine, (2) epinephrine in which both alpha1- and beta-adrenergic effects were blocked by previous administration of prazosin and propranolol, and (3) vasopressin during CPR. All but 1 animal were successfully resuscitated. After injection of epinephrine, significantly better cardiac output and fractional area change, together with lesser increases in troponin I, were observed after alpha1- and beta-adrenergic blockade. Postresuscitation neurological function was also improved after alpha1- and beta-block in comparison with unblocked epinephrine and after vasopressin.

Conclusions: Equipressor doses of epinephrine, epinephrine after alpha1- and beta-adrenergic blockade, and vasopressin were equally effective in restoring spontaneous circulation after prolonged ventricular fibrillation. However, combined alpha1- and beta-adrenergic blockade, which represented a predominantly selective alpha2-vasopressor effect, resulted in improved postresuscitation cardiac and neurological recovery.