A 68-year-old patient in the ICU suddenly develops ventricul… | 마이메르시 MyMerci
마이메르시 — 문제와 상세 해설까지 전부 무료 무료로 시작하기
Critical Care
문제

A 68-year-old patient in the ICU suddenly develops ventricular fibrillation (VF) on the cardiac monitor. The nurse immediately begins CPR. After 2 minutes of high-quality CPR, the first defibrillation is delivered at 200 joules biphasic, but VF persists. What is the nurse's next priority action?

해설
According to ACLS guidelines, after unsuccessful defibrillation, immediate CPR for 2 minutes is prioritized to maintain perfusion before the next shock. Other options (epinephrine, amiodarone, energy increase) are secondary and should not delay CPR.
같은 주제 다음 문제A 68-year-old patient in the ICU is experiencing ventricular fibrillation. The nurse is pr…

심화 해설



Core ACLS Principle for Shock-Refractory VF/pVT


In the management of ventricular fibrillation (VF) or pulseless ventricular tachycardia (pVT) that persists after a single defibrillation attempt, the immediate priority is not a subsequent stacked shock or drug administration, but the resumption of high-quality chest compressions. The 2021 Singapore Advanced Cardiac Life Support Guidelines, which align with international consensus, emphasize a "CPR First" approach after defibrillation. The defibrillator delivers energy to depolarize the myocardium, but the heart requires coronary perfusion pressure to generate an organized rhythm. This perfusion is generated exclusively by chest compressions.





Pathophysiology and Rationale for Immediate CPR


Defibrillation causes a period of myocardial stunning and transient asystole or pulseless electrical activity (PEA). Even if the shock successfully terminates VF, the heart is often not immediately ready to pump effectively. Without immediate compressions, the coronary perfusion pressure falls rapidly to zero, and the myocardium quickly becomes ischemic again, leading to refibrillation. The guideline mandates resuming chest compressions immediately after shock delivery, without pausing for a rhythm or pulse check, to maintain myocardial viability and increase the likelihood of a perfusing rhythm with the next shock.



The specified interval of 2 minutes of CPR before the next rhythm analysis and defibrillation is critical. This cycle allows for the delivery of high-quality compressions at a rate of 100-120/min, with a depth of at least 2 inches (5 cm), ensuring full chest recoil. This optimizes cardiac output and cerebral perfusion, building the metabolic reserve needed for a successful subsequent defibrillation.





Analysis of Incorrect Options


The incorrect options represent common ACLS interventions, but their timing in the sequence is what makes them inappropriate as the next step.




  • Option 1: Administer epinephrine 1 mg IV push immediately. While epinephrine is a first-line vasopressor in cardiac arrest due to its alpha-adrenergic effects that increase coronary and cerebral perfusion pressure, it is not given immediately after the first shock. Per ACLS algorithms, the first dose of epinephrine is administered during the CPR cycle after the second defibrillation attempt, typically within the first or second 2-minute CPR block. Giving it now would interrupt the critical immediate post-shock CPR.


  • Option 2: Increase defibrillation energy to 360 joules for the next shock. For biphasic defibrillators, the initial shock is typically 120-200 J. If the first shock fails, the energy for subsequent shocks should be escalated to the maximum available, often 360 J. However, this energy escalation is for the next shock, which is delivered after a full 2-minute cycle of CPR. It is not an action taken immediately while VF persists on the monitor; the immediate action is to resume compressions.


  • Option 4: Administer amiodarone 300 mg IV push before continuing. Amiodarone is the first-line antiarrhythmic for shock-refractory VF/pVT. It is indicated after the third defibrillation attempt. Administering it after only one shock is premature and would cause a detrimental interruption in chest compressions. The sequence is shock, CPR, shock, CPR + epinephrine, shock, CPR + amiodarone.





Clinical Reasoning and the ACLS Algorithm


The correct sequence, derived from the guideline, is a continuous loop of 2-minute CPR cycles punctuated by brief rhythm checks and shocks. The nurse's cognitive pathway should be: "Shock delivered, VF persists, therefore the next action is to immediately resume chest compressions." The foundational principle is that uninterrupted, high-quality CPR is the single most critical determinant of survival from cardiac arrest. All other interventions—advanced airway, vascular access, drug therapy—are secondary and must be performed in a way that minimizes any pause in compressions. The guideline explicitly structures the algorithm to prevent the common error of delaying CPR to perform other tasks.



임상 시나리오

Clinical Scenario
A 68-year-old ICU patient suddenly develops ventricular fibrillation on the cardiac monitor. The nurse initiates CPR and delivers the first biphasic shock at 200 joules after 2 minutes of high-quality compressions. The rhythm remains VF.
Priority Nursing Action
Immediately resume high-quality chest compressions. Do not pause for a rhythm or pulse check. Continue CPR for a full 2-minute cycle before the next rhythm analysis and defibrillation attempt.
Clinical Reasoning
CPR First After Shock: Defibrillation depolarizes the myocardium but causes a period of stunning where the heart cannot pump effectively. Coronary perfusion pressure, generated only by chest compressions, is required to deliver oxygen to the myocardium and allow an organized rhythm to emerge. Interrupting compressions leads to a rapid drop in perfusion pressure, causing ischemia and refibrillation.

Medication Timing: Epinephrine 1 mg IV is administered after the second shock. Amiodarone 300 mg IV is considered after the third shock. These drugs are never the priority over uninterrupted, high-quality CPR in the immediate post-shock phase.
ACLS Guideline Reference
The 2021 Singapore Advanced Cardiac Life Support Guidelines, aligned with international consensus, mandate immediate resumption of CPR for 2 minutes after each defibrillation attempt for shock-refractory VF/pVT. Rhythm analysis and pulse checks are performed only at the end of each 2-minute CPR cycle.

핵심 개념

Merci NCLEX-RN Question Bank 3,445 문제 · 로그인 없이 바로 볼 수 있어요

마이메르시로 국가고시 완벽 대비

기출문제와 상세 해설을 무료로. 내 약점을 분석하고 진도를 관리하며 더 똑똑하게 공부하세요.

무료로 시작하기
App Store Google Play

학습 참고용입니다. 실제 임상은 최신 지침과 소속 기관 프로토콜을 따르세요.