A 58-year-old male patient is recovering in the cardiac intensive care unit following an a… — USMLE Step 2 CK

A $58$ -year-old male patient is recovering in the cardiac intensive care unit following an anterior wall myocardial infarction. On hospital day $2$ , the telemetry alarms sound. The nurse finds the patient unresponsive and apneic, with no palpable carotid pulse. The bedside cardiac monitor displays a regular, wide-complex tachycardia at a rate of $210/\text{min}$ . Arrange the following resuscitation interventions in the most appropriate chronological sequence from first to last according to standard adult advanced cardiovascular life support (ACLS) algorithms.

1Initiation of high-quality cardiopulmonary resuscitation
2Delivery of an unsynchronized countershock
3Administration of intravenous epinephrine
4Administration of intravenous amiodarone

Answer

The correct chronological sequence is: 1) Initiation of high-quality cardiopulmonary resuscitation, 2) Delivery of an unsynchronized countershock, 3) Administration of intravenous epinephrine, 4) Administration of intravenous amiodarone.

According to the adult cardiac arrest algorithm for shockable rhythms (VF/pVT), high-quality CPR must be initiated immediately upon identifying pulselessness. The next immediate step is to deliver an unsynchronized countershock (defibrillation) as soon as the device is available. If the shockable rhythm persists after the first shock and subsequent 2 minutes of CPR, a second shock is delivered. Only after the second shock has failed is intravenous epinephrine (1 mg) indicated. If the rhythm still persists after a third shock, an antiarrhythmic such as intravenous amiodarone (300 mg bolus) is administered. Therefore, the strict chronological progression is CPR, then Defibrillation, then Epinephrine, then Amiodarone.

Step-by-Step Solution

Identify the clinical state

The patient is unresponsive, apneic, and pulseless, indicating a state of cardiac arrest.

This determines the need to immediately initiate the cardiac arrest algorithm rather than a tachycardia with a pulse algorithm.

Analyze the bedside cardiac rhythm

The monitor shows a wide-complex tachycardia at

210/\text{min}

in a pulseless patient, confirming pulseless ventricular tachycardia (pVT).

Pulseless VT is a shockable rhythm, dictating the specific right-sided branch of the ACLS cardiac arrest algorithm.

Determine the standardized sequence of interventions for a shockable rhythm

The protocol dictates immediate CPR, followed rapidly by defibrillation. If the rhythm persists, epinephrine is administered after the second shock, and amiodarone is given after the third shock.

This highly standardized sequence maximizes coronary perfusion pressure via CPR/vasopressors and addresses electrical instability hierarchically to optimize survival rates.

Key Concept

The standard ACLS sequence for pulseless ventricular tachycardia (pVT) prioritizes immediate cardiopulmonary resuscitation (CPR) and rapid unsynchronized defibrillation, followed by the sequential addition of epinephrine (after the 2nd shock) and amiodarone (after the 3rd shock) for refractory cases.

Estimated Time:1m 30s

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