EPINEPHRINE IN VENTRICULAR FIBRILLATION: FRIEND OR FOE?AREVIEW FOR THE EMERGENCY NURSE Authors: Theodoros Xanthos, MD, PhD, Ioannis Pantazopoulos, MD, MSc, Theano Demestiha, MD, PhD, and Konstantinos Stroumpoulis, MD, PhD, Athens, Greece Section Editor: Allison A. Muller, PharmD, D.ABAT Earn Up to 8.5 CE Hours. See page 425. T he incidence of cardiac arrest in North America and Europe is approximately 1 million each year, with dismal survival and hospital discharge rates. 1 The rate of survival of patients with in-hospital cardiac arrest is about 16%. 2 Ventricular fibrillation (VF) is the electrocardiographic rhythm observed in up to 40% of the cases when help arrives, but it is estimated to be the etiologic factor for more than 70% of cardiac arrests. 3 During CPR, the coronary perfusion pressure (CPP), defined as the pressure gradient between the aorta and the right atrium at the decompression phase, is positively cor- related with return of spontaneous circulation (ROSC) and survival. 4 However, the blood flow generated during CPR rarely exceeds 30% of the normal cardiac output. Therefore a further increase in systemic vascular resistance is necessary for augmenting CPP. This is the place for vasopressor use as an adjunctive therapy to CPR to increase both myocar- dial and cerebral perfusion pressures. 5 The aim of this article is to describe the current recom- mendations regarding epinephrine in the VF setting and to emphasize that its use during VF arrest is not a panacea. Three-Phase VF Model The 3-phase model of VF proposed by Weisfeldt and Becker, 6 based largely on animal studies, is divided into the following phases: (1) the electrical phase (up to 4 min- utes after cardiac arrest), (2) the circulatory or hemody- namic phase (4-10 minutes after cardiac arrest), and (3) the metabolic phase (>10 minutes after cardiac arrest). According to this model, VF response to therapies is time dependent. In the electrical phase, the fibrillating myocar- dium has not, by that time, used up all its energy stores, and a rescue defibrillation attempt may be successful. This is the reason why the benefit of automated external defi- brillator use has been shown in various settings including casinos, airplanes, airports, and the community. 7 During the hemodynamic phase, immediate electrical defibrillation is typically unsuccessful and reduces the chances of survival. 8 Generation of adequate cerebral perfu- sion pressure and CPP is critical if defibrillation is to suc- ceed and the patient to survive without any neurologic deficits. During this phase, evidence supports administra- tion of vasopressors. In fact, vasopressor administration is necessary to elevate CPP higher than the required threshold of 20 mm Hg for achieving ROSC. 9 There are indications that this phase can be extended even to 17 minutes after cardiac arrest with optimal resuscitation techniques such as good-quality chest compressions, as well as the correct timing of vasopressor administration. 10 During the metabolic phase, prolonged ischemia, in association with epinephrine-induced vasoconstriction and endotoxin release in the circulation, results in severe organ damage. In this period, resuscitative efforts are rarely successful. 6 Epinephrine’s Actions Epinephrine is a nonselective α-adrenoreceptor (α 1 and α 2 ) and β-adrenoreceptor (β 1 and β 2 ) agonist. Its benefi- cial effects are mediated by α-adrenergic receptors causing arterial and arteriolar vasoconstriction in the skin, mucosa, Theodoros Xanthos is a medical doctor, Department of Anatomy, Medical School, University of Athens, Athens, Greece. Ioannis Pantazopoulos is a medical doctor, 12th Department of Respiratory Medicine, Sotiria General Hospital, Athens, Greece. Theano Demestiha is a medical doctor, Department of Anatomy, Medical School, University of Athens, Athens, Greece. Konstantinos Stroumpoulis is a medical doctor, Department of Anatomy, Medical School, University of Athens, Athens, Greece. For correspondence, write: Theodoros Xanthos, PhD, Department of Anatomy, Medical School, University of Athens, 75 Mikras Asias Street, 11527, Athens, Greece; E-mail: theodorosxanthos@yahoo.com. J Emerg Nurs 2011;37:408-12. Available online 22 February 2011. 0099-1767/$36.00 Copyright © 2011 Emergency Nurses Association. Published by Elsevier Inc. All rights reserved. doi: 10.1016/j.jen.2010.10.007 PHARM/TOX CORNER 408 JOURNAL OF EMERGENCY NURSING VOLUME 37 • ISSUE 4 July 2011