The standard treatment for ventricular fibrillation, defibrillation involves using external pads or paddles to direct an electrical current through the patient’s heart. The current causes the myocardium to depolarize; this, in turn, encourages the sinoatrial node to resume control of the heart’s electrical activity. This current can be delivered by a monophasic or biphasic defibrillator.

Defibrillators with monophasic waveforms deliver current in one direction (as shown below). Few monophasic defibrillators are being manufactured, but some are still in use. For monophasic defibrillation to be effective, a high amount of electrical current is required.


With biphasic defibrillation, the electrical current discharged from the pads or paddles travels in a positive direction for a specified duration and then reverses and flows in a negative direction for the remaining time of the electrical discharge (as shown on next page). It delivers two currents of electricity and lowers the defibrillation threshold of the heart muscle, making it possible to successfully defibrillate ventricular fibrillation with smaller amounts of energy. The biphasic defibrillator can adjust for differences in impedance or the resistance of the current through the chest. This helps reduce the number of shocks needed to terminate ventricular fibrillation. Biphasic technology uses lower
energy levels and fewer shocks, thus reducing the damage to the myocardial muscle. Biphasic defibrillators, when used at the clinically appropriate energy level, may be used for defibrillation and, when placed in the synchronized mode, may be used for synchronized cardioversion.


The external (hands-off) pads delivering the current are placed on the patient’s chest. Paddles may be used directly on the chest using conductive defibrillation pads, or, during cardiac surgery when the patient’s chest is open, sterile defibrillation paddles may be placed directly on the myocardium. (See Using a defibrillator.)

Using the self-adhesive (hands-off) defibrillation pads has been shown to be as effective as paddles, with the advantage of being convenient and safe, and allow rapid delivery of a shock, if necessary. They can also be used for monitoring and are recommended for routine use, if available, instead of paddles.1

Patients with a history of ventricular fibrillation may be candidates for an implantable cardioverter-defibrillator (ICD), a sophisticated device that automatically discharges an electrical current when it senses a ventricular tachyarrhythmia. (See Understanding the ICD, page 226.)

Preparation of Equipment

Connect the defibrillation pads or paddles to the defibrillator and check that the defibrillator battery is adequately charged or the defibrillator electrical cord is plugged into the wall. Ensure that resuscitation equipment and medications are immediately available.

Jul 21, 2016 | Posted by in NURSING | Comments Off on Defibrillation

Full access? Get Clinical Tree

Get Clinical Tree app for offline access