28: Defibrillation and Cardioversion

INTRODUCTION

Defibrillation and cardioversion are used for rapid termination of a tachyarrhythmia (a fast abnormal rhythm originating either in the atrium or ventricle) that is unresponsive to baseline treatment or is causing the patient to have cardiovascular compromise (inadequate systemic perfusion). Baseline treatment consists of correcting metabolic problems, use of vagal maneuvers (bag of ice water over the eyes and face of the infant without obstructing the airway, pressure on closed eyelids), use of medications (adenosine, digoxin, propranolol, verapamil, amiodarone, procainamide, lidocaine, or magnesium sulfate), or transesophageal pacing. It is best to try these maneuvers or medical therapy if intravenous access is available. Neonatal arrhythmias are rare, and the majority of them can be treated with these initial measures.

Current defibrillators are capable of delivering 2 modes of shock: synchronized and unsynchronized. Synchronized shocks are lower dose and used for cardioversion. Unsynchronized shocks are higher dose and used for defibrillation. Pediatric cardiology consultation is recommended for all infants with a tachyarrhythmia.

I. INDICATIONS

1. Cardioversion (synchronized cardioversion)

   1. Unstable patients with tachyarrhythmias who have a perfusing rhythm but evidence of poor perfusion, heart failure, or hypotension (signs of cardiovascular compromise). Examples of tachyarrhythmias are:

      1. Tachycardia (supraventricular tachycardia [SVT] or ventricular tachycardia [VT]) with a pulse and poor perfusion

      2. Supraventricular tachycardia with shock and no vascular access

      3. Atrial flutter with shock

      4. Atrial fibrillation with shock (very rare in infants)

   2. Elective cardioversion in infants with stable SVT, VT, or atrial flutter (good tissue perfusion and pulses) unresponsive to other treatments. This is always done under the close supervision of a pediatric cardiologist. Sedation and a 12-lead electrocardiogram are recommended before cardioversion.

2. Defibrillation (asynchronized). Used in pulseless arrest with a shockable rhythm (VT and ventricular fibrillation). It is used in between cardiopulmonary resuscitation (CPR) and not used in asystole or pulseless electrical activity (PEA). The most common cause of a ventricular arrhythmia in a neonate is electrolyte imbalance. Defibrillation will not stop the arrhythmia in these patients. Defibrillation is the most effective treatment for ventricular fibrillation and pulseless ventricular tachycardia.

II. EQUIPMENT

1. External standard defibrillator (manual or semiautomated) and 2 paddles of the correct sizes with conductive pads. For infants, use the smallest size (usually measuring 4.5 cm). It is important to be familiar with your institution's equipment because there are many different types and models of machines. Pediatric-capable automatic external defibrillators (adult-automated external defibrillators with energy reducer pads) can be used for infants.

2. Other equipment. Heart rate monitor, airway equipment, resuscitation medications, antiarrhythmic medications, and equipment used in basic and advanced life support.

III. PROCEDURE

1. Adequate sedation (may not be possible in emergency situations), preoxygenation, and continuous heart monitoring are essential. Emergency airway equipment should be readily available.

2. Pain management. During a code, pain relief is not focused on. Depending on the type of procedure, sedation may be considered. ...