Defibrillation is an emergency medical procedure that delivers a therapeutic dose of electrical current to the heart. This electrical shock depolarizes a critical mass of the heart muscle simultaneously, terminating chaotic electrical activity and allowing the natural pacemaker of the heart to resume normal sinus rhythm. It is exclusively indicated for cardiac arrest presentations involving shockable rhythms.
Understanding the electrical chaos inside the myocardium clarifies why emergency intervention is time-critical. In Ventricular Fibrillation (VF), multiple ectopic foci fire rapidly and independently across the ventricles. The heart muscle loses coordinated contraction, ceasing cardiac output entirely within seconds. Cerebral hypoxia follows rapidly, leading to irreversible brain damage if untreated.
Pulseless Ventricular Tachycardia (VT) features a single, fast, and regular ventricular pacemaker firing at rates often exceeding 150 beats per minute. Although the rhythm may appear organized on the cardiac monitor, mechanical contraction is too weak to generate a pulse, effectively rendering the patient in cardiac arrest. Both rhythms demand rapid electrical termination before myocardial energy stores become completely depleted.
Modern resuscitation relies heavily on advanced waveform technology. Monophasic defibrillators deliver current in a single direction, requiring higher energy levels—typically starting at 360 Joules—to successfully terminate arrhythmias.
Biphasic defibrillators send current in one direction and then reverse it midway through the shock. This bidirectional flow lowers the necessary energy threshold, usually starting between 120 and 200 Joules. Lower energy delivery reduces the risk of post-shock myocardial dysfunction while maintaining high success rates for conversion.
Before delivering any electrical shock, the nurse must ensure environmental and clinical safety to prevent accidental injury to the resuscitation team.
Executing a defibrillation safely requires a disciplined sequence of actions during a resuscitation code.
Once the shock is delivered, immediate resumption of cardiopulmonary resuscitation for two minutes takes priority before re-evaluating the cardiac rhythm. When a perfusing rhythm returns, comprehensive post-resuscitation care begins.
Despite careful execution, challenges and adverse effects can arise during defibrillation. Skin burns frequently occur if insufficient conductive gel is used or if electrode pads are improperly applied. Myocardial stunning may temporarily impair cardiac contractility after high-energy shocks.
Equipment failure represents another critical risk. If the defibrillator displays a "pads off" or poor contact error message, the nurse must check cable connections, ensure firm downward pressure on manual paddles, or replace dried-out adhesive pads immediately.