Evidence favoring the use of an α2-selective vasopressor agent for cardiopulmonary resuscitation

Background - Both alpha(1)- and beta-adrenergic agonists increase the severity of global myocardial ischemic injury. We hypothesized that combined beta- and alpha(1)-adrenergic blockade would improve initial resuscitation and postresuscitation myocardial and neurological functions. We further hypothesized that the resulting alpha(2)-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 alpha(1)- 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 alpha(1)- and beta-adrenergic blockade. Postresuscitation neurological function was also improved after alpha(1)- and beta-block in comparison with unblocked epinephrine and after vasopressin. Conclusions - Equipressor doses of epinephrine, epinephrine after alpha(1)- and beta-adrenergic blockade, and vasopressin were equally effective in restoring spontaneous circulation after prolonged ventricular fibrillation. However, combined alpha(1)- and beta-adrenergic blockade, which represented a predominantly selective alpha(2)-vasopressor effect, resulted in improved postresuscitation cardiac and neurological recovery.