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Difficulty: HardCardiovascular System

A 54-year-old man collapses in an airport terminal and is unresponsive. Bystanders immediately initiate cardiopulmonary resuscitation (CPR). Emergency medical services (EMS) arrive shortly after and confirm the patient is pulseless and apneic. The cardiac monitor displays coarse ventricular fibrillation. Arrange the following critical interventions in the correct chronological sequence for the management of this patient according to standard cardiac arrest algorithms.

  1. 1Deliver the initial unsynchronized defibrillation shock.
  2. 2Immediately resume continuous high-quality CPR for 2 minutes and establish intravenous access.
  3. 3Deliver a second unsynchronized defibrillation shock and subsequently administer intravenous epinephrine.
  4. 4Deliver a third unsynchronized defibrillation shock and subsequently administer intravenous amiodarone.

Answer

The correct sequence is to deliver the initial shock, immediately resume CPR while obtaining access, deliver a second shock followed by epinephrine, and finally deliver a third shock followed by amiodarone.
The Advanced Cardiac Life Support (ACLS) algorithm for pulseless ventricular tachycardia (pVT) and ventricular fibrillation (VF) dictates a precise sequence to maximize survival. When VF is identified, the immediate step is to deliver an unsynchronized defibrillation shock. Following the shock, chest compressions must be resumed immediately for 2 minutes without checking a pulse, during which time intravenous or intraosseous access is established. After 2 minutes, the rhythm is checked; if VF persists, a second shock is given. CPR is again resumed immediately, and the first dose of epinephrine (1 mg) is administered. After another 2 minutes, if VF is still present, a third shock is delivered. During the subsequent CPR cycle, an antiarrhythmic medication, typically amiodarone (300 mg bolus) or lidocaine, is administered to treat the refractory arrhythmia. This sequence precisely balances the need for electrical therapy with the critical requirement of maintaining coronary perfusion pressures through uninterrupted compressions.

Step-by-Step Solution

1
Identify the shockable rhythm and perform the primary intervention.
The initial unsynchronized defibrillation shock is delivered.
Ventricular fibrillation (VF) and pulseless ventricular tachycardia (pVT) require immediate defibrillation as the first definitive treatment to restore a perfusing rhythm.
2
Maintain systemic perfusion and prepare for medication administration.
High-quality CPR is resumed for 2 minutes without pausing for a pulse check, and intravenous/intraosseous access is established.
Defibrillation temporarily stuns the heart; immediate CPR provides necessary coronary and cerebral perfusion while the myocardium recovers. Access is needed for subsequent pharmacotherapy.
3
Address persistent ventricular fibrillation with a second shock and the first-line vasopressor.
A second defibrillation shock is delivered, followed by continued CPR and administration of intravenous epinephrine 1 mg.
If VF persists after the first shock and CPR cycle, a second shock is indicated. Epinephrine is added at this stage to increase aortic diastolic pressure and enhance coronary perfusion during CPR.
4
Address refractory ventricular fibrillation with a third shock and an antiarrhythmic agent.
A third defibrillation shock is delivered, followed by continued CPR and administration of intravenous amiodarone 300 mg.
For VF that is refractory to CPR, defibrillation, and a vasopressor, an antiarrhythmic drug (amiodarone or lidocaine) is administered to increase the likelihood of successful defibrillation on subsequent attempts.

Key Concept

Advanced Cardiac Life Support (ACLS) Pulseless Ventricular Tachycardia and Ventricular Fibrillation Algorithm
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Topics

Cardiovascular System

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