A patient with atrial fibrillation is receiving continuous cardiac monitoring. The nurse observes a sudden change to ventricular tachycardia on the monitor. The patient becomes unresponsive with no palpable pulse. What is the nurse's immediate priority action?

In pulseless VT, immediate defibrillation is the priority as it can restore organized rhythm and circulation. Other interventions like epinephrine, compressions, or airway management are secondary after defibrillation.

Clinical Scenario Analysis
The monitor shows a sudden change from atrial fibrillation to ventricular tachycardia in a patient who is now unresponsive and pulseless. This clinical picture defines a shockable rhythm cardiac arrest. The immediate priority is to deliver the first shock as quickly as possible, as the probability of successful defibrillation declines rapidly with each passing minute.

Why Immediate Defibrillation is the Priority
In a witnessed, monitored cardiac arrest with a shockable rhythm (ventricular tachycardia or ventricular fibrillation), the underlying pathophysiology is chaotic, asynchronous electrical activity that prevents coordinated myocardial contraction. The most effective intervention is to depolarize a critical mass of the myocardium simultaneously with a direct-current shock, allowing the heart's natural pacemaker to resume control. The 2025 Korean Guidelines for Cardiopulmonary Resuscitation emphasize a structured approach to advanced life support, and the foundational step for a shockable rhythm is defibrillation. Initiating defibrillation with 200 joules biphasic is the correct, evidence-based priority action that directly treats the proximate cause of the arrest.

Analysis of Other Options Based on Guideline Principles
The guidelines establish a clear sequence of interventions that prioritizes early defibrillation over drug administration and advanced airway placement for shockable rhythms.

Option	Rationale for Not Being the Immediate Priority
1. Administer epinephrine 1 mg IV push immediately	While the guidelines recommend epinephrine as the vasopressor of choice during cardiac arrest, it is not the first intervention for a shockable rhythm. The initial priority is defibrillation. Epinephrine is administered after the first or second shock, typically every 3 to 5 minutes, to increase coronary and cerebral perfusion pressure during chest compressions. Delaying defibrillation to give a drug would be a critical error, as the rhythm's responsiveness to electrical therapy is time-sensitive [1].
3. Begin chest compressions at 100-120 per minute	High-quality chest compressions are a cornerstone of cardiac arrest management, but in a witnessed, monitored arrest with a shockable rhythm, the immediate action is defibrillation. The guidelines support a strategy where, if a defibrillator is immediately available, a shock should be delivered without a preceding period of chest compressions. Chest compressions are initiated immediately after the shock, without pausing for a rhythm check, to maintain myocardial perfusion [1].
4. Establish advanced airway with endotracheal intubation	Advanced airway management is a lower-priority intervention in the initial phase of a cardiac arrest. The guidelines focus on minimizing interruptions in chest compressions and delivering shocks. While the preferred initial route for drug administration is intravenous access, with intraosseous access as an alternative, securing an advanced airway is deferred until after the initial rhythm-specific interventions (defibrillation) and high-quality CPR are underway. The immediate goal is to restore a perfusing rhythm, not to intubate [1].

The core principle from the guideline update is a structured, evidence-based sequence: for a pulseless patient with a shockable rhythm, the immediate priority is to deliver a shock using a biphasic defibrillator at the manufacturer's recommended dose, typically 200 joules for the first shock. This action provides the best chance for return of spontaneous circulation ^[1].