defibrillation /difī′brilā″shən/ , the termination of ventricular fibrillation or pulseless ventricular tachycardia (inefficient, asynchronous contraction) by delivery of an electric shock to the patient’s precordium. It is a common emergency measure generally performed by a physician, specially trained nurse, or paramedic. A device called an automated external defibrillator (AED) is designed for use by the lay public. In external defibrillation, one paddle is placed to the right of the upper sternum below the clavicle, and the other is applied to the midaxillary line of the left lower rib cage. In internal defibrillation, which may be performed during open-heart surgery, the paddles are placed directly on the heart. The defibrillator, usually a condenser-discharge system, is set to deliver between 200 and 360 J. If shocks fail to restore a perfusion rhythm, cardiopulmonary resuscitation is begun. Repeat shocks also are attempted periodically until ventricular fibrillation ceases or the efforts are deemed futile. See also automated external defibrillator. −defibrillate, v.
