CPR Electrical Therapy Principles 3 — Questions and Answers
Question 1: Which of the following is a contraindication to transcutaneous pacing?
- Symptomatic bradycardia with hypotension
- Hypothermic cardiac arrest with bradycardia (Correct answer)
- Third-degree AV block with hemodynamic instability
- Atropine-refractory symptomatic bradycardia
Correct answer: Hypothermic cardiac arrest with bradycardia
In hypothermic cardiac arrest, pacing is generally avoided because the cold heart is prone to VF and warming is the primary treatment.
Question 2: When applying defibrillator pads, the anterior-posterior electrode placement is preferred in which situation?
- When the patient is obese
- When the patient has a permanent pacemaker (Correct answer)
- During pediatric defibrillation
- When performing synchronized cardioversion only
Correct answer: When the patient has a permanent pacemaker
Anterior-posterior pad placement avoids delivering energy directly through a permanent pacemaker's leads and generator.
Question 3: The recommended initial energy for biphasic defibrillation of ventricular fibrillation is:
- 50-75 joules
- 120-200 joules (Correct answer)
- 300 joules
- 360 joules
Correct answer: 120-200 joules
Current AHA guidelines recommend 120-200J for the initial biphasic shock in VF, following the manufacturer's specifications.
Question 4: During transcutaneous pacing, you observe pacing spikes on the monitor but no pulse. This is called:
- Oversensing
- Electrical capture without mechanical capture (Correct answer)
- Failure to sense
- Undersensing
Correct answer: Electrical capture without mechanical capture
Electrical capture without mechanical capture means the heart is receiving the electrical stimulus but not contracting effectively in response.
Question 5: Which antiarrhythmic drug is given concurrently with CPR and defibrillation for shock-refractory VF?
- Adenosine
- Amiodarone (Correct answer)
- Diltiazem
- Magnesium sulfate
Correct answer: Amiodarone
Amiodarone 300mg IV/IO is the first-line antiarrhythmic for shock-refractory VF in the ACLS algorithm.
Question 6: What physiological parameter most directly determines how much energy is required to defibrillate a patient?
- Body weight
- Transthoracic impedance (Correct answer)
- Heart rate prior to arrest
- Blood pressure
Correct answer: Transthoracic impedance
Transthoracic impedance determines resistance to current flow through the chest; higher impedance requires more energy for effective defibrillation.
Question 7: A patient in polymorphic VT (Torsades de Pointes) with a pulse becomes unstable. The MOST appropriate electrical therapy is:
- Synchronized cardioversion at 100J
- Unsynchronized defibrillation at 200J (Correct answer)
- Transcutaneous pacing to overdrive suppress
- Synchronized cardioversion at 360J
Correct answer: Unsynchronized defibrillation at 200J
Torsades de Pointes with an unstable pulse is treated with unsynchronized defibrillation because the irregular morphology makes synchronization unreliable.
CPR Electrical Therapy Principles 3
Which of the following is a contraindication to transcutaneous pacing?