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Amiodarone in Cardiac Arrest.

* Amiodarone is more effective than placebo for increasing survival to hospitalization in cardiac arrest patients who remain in ventricular fibrillation/pulseless ventricular tachycardia despite defibrillation and intravenous epinephrine.

* The efficacy of amiodarone compared with lidocaine for reestablishing a stable cardiac rhythm and a pulse in patients with ventricular fibrillation/pulseless ventricular tachycardia is unknown.

The Problem

A local ambulance company brings a 65-year-old man who collapsed while mowing his lawn to the emergency room in a small hospital. He has a history of coronary artery disease and congestive heart failure; he underwent coronary artery bypass graft surgery in 1996. His wife saw him clutch his chest and sit down on the ground. When she ran to help him, he was unresponsive. The patient's estimated "down time" is 5 minutes, and the initial rhythm on arrival at the patient's house was ventricular fibrillation. As the emergency medical technicians wheel the patient through the door, they explain that he has received epinephrine, countershocks, and an endotracheal tube. He remains in ventricular fibrillation. As resuscitation continues, the administration of lidocaine or amiodarone is considered. Amiodarone has been added to the list of antiarrhythmics to use for shock-refractory ventricular fibrillation with a class IIb level of evidence (fair to good evidence without evidence of harm). Lidocaine is class indetermina te (no good evidence available) according to the new Advanced Cardiopulmonary Life Support (ACLS) guidelines.

The Question

In patients with ventricular fibrillation refractory to defibrillation and epinephrine, is amiodarone more effective than lidocaine in reestablishing a stable cardiac rhythm?

Seeking evidence: A PubMed search is performed (www.ncbi.nlm.nih.gov/entrez). Selecting therapy and specificity under Clinical Queries and entering "amiodarone" and "cardiac arrest" yield an article on amiodarone use in cardiac arrest. (See "The Evidence" at right.)

Expert opinion: The recent addition of amiodarone to the list of antiarrhythmics to be used for ventricular fibrillation/pulseless ventricular tachycardia emphasizes the importance of periodically evaluating the medical literature and updating ACLS guidelines. It also should remind us that health care professionals should keep their ACLS certification current. Since there are no reliable mechanisms for physicians to be updated on new changes in the ACLS algorithms, periodic retraining ensures that patients will receive the most evidence-based life-sustaining interventions.

Clinical decision: Amiodarone is administered. The patient converts to a stable cardiac rhythm with a faint pulse. He is placed on dopamine and transferred to the ICU.

Assessor's summary: This article addresses a topic that is difficult to study in a clinical trial. This study provides more evidence than we have for any other antiarrhythmic in the ventricular fibrillation/pulseless ventricular tachycardia ACLS algorithm, other than magnesium for known hypomagnesemia. We would be most interested in a study assessing survival to discharge and neurologic status at discharge. We also would like to see a direct comparison between amiodarone and lidocaine. Finally we need to be cautious about the conclusions that we draw from the several subgroup analyses presented in this article.

The Evidence

Amiodarone for resuscitation after out-of-hospital cardiac arrest due to ventricular fibrillation.

N. Engl. J. Med. 341(12):871-78, 1999.

* Design: Prospective, double-blinded, randomized, placebo-controlled trial.

* Subjects: Over 500 individuals experiencing out-of-hospital cardiac arrest in Seattle. All subjects were in ventricular fibrillation or pulseless ventricular tachycardia and had not reestablished a pulse with defibrillation and epinephrine after a similar duration of resuscitation attempts.

* Intervention: 300 mg of IV amiodarone or placebo.

* Outcomes: The primary end point was survival to hospital admission. Secondary end points included survival to hospital discharge and functional neurologic status.

Results

Overall, cardiac arrest patients were more likely to survive to hospital admission if they received amiodarone (44%) rather than placebo (34%). The number needed to treat (NNT) to prevent one death prior to hospital arrival was 11. There were no significant differences between the treatment arms in any of the secondary end points, such as hospital discharge and neurologic function.

Subgroup analyses were performed:

* Ventricular fibrillation: 49% survival with amiodarone and 39% with placebo; the NNT was 10.

* Asystole/pulseless electrical activity: 17% survival with amiodarone and 12% with placebo; NNT was 19.

* Transient return of spontaneous circulation at some point prior to randomization: 64% survival with amiodarone and 41% with placebo; NNT was 5.

The authors are with the Mayo Clinic in Rochester, Minn.
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Article Details
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Author:ASHTON, RENDELL; EBBERT, JON O.; TANGALOS, ERIC G.
Publication:Internal Medicine News
Article Type:Brief Article
Geographic Code:1USA
Date:Oct 15, 2001
Words:714
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