PALS Tachycardia 4 — Questions and Answers
Question 1: A 5-year-old presents with palpitations, pallor, and a heart rate of 240 bpm. After ice pack application to the face, the rate abruptly converts to 95 bpm. What rhythm did this child most likely have?
- Sinus tachycardia
- Atrial fibrillation
- SVT (Correct answer)
- Ventricular fibrillation
Correct answer: SVT
The abrupt conversion to normal rate following a vagal maneuver (ice pack facial immersion) is characteristic of SVT, which terminates abruptly rather than gradually.
Question 2: Which ECG finding is most characteristic of ventricular tachycardia (VT) compared to SVT with aberrancy?
- Narrow QRS complexes <0.08 seconds
- AV dissociation visible on the tracing (Correct answer)
- Retrograde P waves immediately after QRS
- Rate less than 150 bpm
Correct answer: AV dissociation visible on the tracing
AV dissociation (independent P waves and QRS complexes) is a classic marker of ventricular tachycardia that helps distinguish it from SVT with aberrancy.
Question 3: A 9-year-old with Wolff-Parkinson-White (WPW) syndrome develops rapid atrial fibrillation. Which drug should be AVOIDED?
- Procainamide
- Amiodarone infusion (in some guidelines)
- Adenosine (Correct answer)
- Synchronized cardioversion
Correct answer: Adenosine
Adenosine (and AV nodal blocking agents) should be avoided in WPW with atrial fibrillation as they can accelerate conduction through the accessory pathway, causing VF.
Question 4: What is the correct energy dose for the SECOND attempt at synchronized cardioversion in a child with unstable SVT if the first attempt at 1 J/kg was unsuccessful?
- 1.5 J/kg
- 2 J/kg (Correct answer)
- 4 J/kg
- 5 J/kg
Correct answer: 2 J/kg
PALS guidelines recommend escalating synchronized cardioversion from 0.5-1 J/kg to 2 J/kg for the second and subsequent attempts.
Question 5: A nurse asks why the defibrillator must be in 'synchronized' mode before cardioverting SVT. What is the correct explanation?
- To deliver more energy than standard defibrillation
- To avoid delivering a shock during the vulnerable T-wave period (Correct answer)
- To allow multiple shocks in rapid succession
- To reduce the energy requirement by 50%
Correct answer: To avoid delivering a shock during the vulnerable T-wave period
Synchronized cardioversion delivers the shock on the R wave to avoid the vulnerable T-wave repolarization period, which could trigger ventricular fibrillation.
Question 6: In a 2-month-old infant with confirmed SVT who is mildly symptomatic, what is the preferred initial pharmacological treatment?
- Verapamil 0.1 mg/kg IV
- Adenosine 0.1 mg/kg rapid IV (Correct answer)
- Digoxin 10 mcg/kg IV
- Propranolol 0.01 mg/kg IV
Correct answer: Adenosine 0.1 mg/kg rapid IV
Adenosine 0.1 mg/kg rapid IV is the first-line pharmacological treatment for SVT in infants when vagal maneuvers fail, regardless of age.
Question 7: A child in SVT has an IV established in the hand. Adenosine is ordered. Compared to a central line or antecubital IV, what adjustment should be made?
- Reduce the dose by half
- No adjustment needed; technique is the same
- Use an even faster flush and ensure rapid delivery to central circulation (Correct answer)
- Adenosine cannot be given peripherally; use IO instead
Correct answer: Use an even faster flush and ensure rapid delivery to central circulation
When adenosine is given via a distal peripheral IV, a very rapid flush of 5-10 mL NS must immediately follow to push the drug centrally before it degrades.
PALS Tachycardia 4
A 5-year-old presents with palpitations, pallor, and a heart rate of 240 bpm.
After ice pack application to the face, the rate abruptly converts to 95 bpm.
What rhythm did this child most likely have?