Alpha-methylnorepinephrine, a selective alpha(2)-adrenergic agonist for cardiac resuscitation

OBJECTIVES The purpose of this study was to investigate the effects of a se lective alpha(2)-adrenergic agonist, alpha-methylnorepinephrine (alphaMNE) as an alternative vasopressor agent during cardiopulmonary resuscitation (C PR). BACKGROUND For more than 40 years, epinephrine has been the vasopressor age nt of choice for CPR. Its beta- and alpha(1)-adrenergic effects increase my ocardial oxygen consumption, magnify global myocardial ischemia and increas e the severity of postresuscitation myocardial dysfunction. METHODS Ventricular fibrillation (VF) was induced in 20 Sprague-Dawley rats . After 8 min of untreated VF, mechanical ventilation and precordial compre ssion began. AlphaMNE, epinephrine or saline placebo was injected into the right atrium 2 min after the start of precordial compression. As an additio nal control, one group of animals was pretreated with alpha, receptor block er, yohimbine, before injection of alphaMNE. Defibrillation was attempted 4 min later. Left ventricular pressure, dP/dt(40) negative dP/dt and cardiac index were measured for an interval of 240 min after resuscitation. RESULTS Except for saline placebo and yohimbine-treated animals, comparable increases in coronary perfusion pressure were observed after each drug int ervention. All animals were successfully resuscitated. Left ventricular dia stolic pressure, cardiac index, dP/dt,, and negative dP/dt were more optima l after alphaMNE; this was associated with significantly better postresusci tation survival. Pretreatment with yohimbine abolished the beneficial effec ts of alphaMNE. CONCLUSIONS The selective alpha(2)-adrenergic agonist, alphaMNE, was as eff ective as epinephrine for initial cardiac resuscitation but provided striki ngly better postresuscitation myocardial function and survival. (J Am Coil Cardiol 2001;37:951-6) (C) 2001 by the American College of Cardiology.