What is the initial energy level of a biphasic defibrillator?

Appeared in: SGPGI Nursing Officer-2024

Explanation

Biphasic defibrillators deliver current in two phases, which is more effective at terminating arrhythmias like ventricular fibrillation (VF).
Due to their higher efficiency, they require less energy than monophasic devices.
The standard recommended initial energy dose for an adult using a biphasic defibrillator is 120 to 200 Joules (J), as per Advanced Cardiac Life Support (ACLS) guidelines.
This lower energy level reduces the risk of heart muscle damage and skin burns.

Option A: This range includes 360 J, which is the standard energy level for a monophasic defibrillator, not the initial dose for a biphasic one. While subsequent biphasic shocks may be escalated, the initial dose is lower.
Option C: This energy range (120-200 J) is correct for a biphasic defibrillator, not a monophasic one. Monophasic devices are less efficient and require a higher energy dose.
Option D: This energy level is far too low for effective defibrillation in an adult using a monophasic device. Such low energy would not successfully terminate ventricular fibrillation.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Defibrillation Energy Levels (Biphasic vs. Monophasic) as background academic context rather than a clinical decision trigger.
Using the correct initial energy dose is a critical step in ACLS protocols to maximize the chance of successful defibrillation and return of spontaneous circulation (ROSC).
Biphasic defibrillators are the current standard of care as they cause less myocardial injury and skin burns compared to monophasic devices due to the lower energy used.
Nurses must be able to quickly identify the type of defibrillator available (biphasic or monophasic) and select the appropriate energy level during a cardiac arrest emergency.

How to Approach the Question

First, identify the key terms in the question: 'initial energy level' and 'biphasic defibrillator'.
Recall the two main types of defibrillators used in clinical practice: monophasic and biphasic.
Remember the fundamental difference in their efficiency: biphasic waveforms are more effective and therefore require less energy.
Associate 'biphasic' with the recommended lower energy range for an initial shock (120-200 J).
Associate 'monophasic' with the standard higher, single-shock energy level (360 J).
Evaluate the given options to find the one that correctly matches the defibrillator type with its corresponding energy range.

Concept Tested & Keywords

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E6 Medicine Davidson Principles Practice 24e p. 502-504

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Attempt every question from this paper in a timed mock, then review the full solution for each one.