PALS Tachycardia 5 — Questions and Answers
Question 1: A 6-year-old with SVT is being monitored; the team cannot obtain IV access. What alternative route can adenosine be given?
- Intramuscular (IM)
- Intraosseous (IO) (Correct answer)
- Sublingual
- Intranasal
Correct answer: Intraosseous (IO)
Intraosseous (IO) access is an acceptable alternative to IV for adenosine administration when IV access cannot be established rapidly.
Question 2: Which of the following best describes the mechanism of action of adenosine in terminating SVT?
- Blocks sodium channels in ventricular myocytes
- Transiently blocks AV nodal conduction, interrupting re-entry circuits (Correct answer)
- Increases cardiac output by enhancing contractility
- Prolongs the QT interval to reset the rhythm
Correct answer: Transiently blocks AV nodal conduction, interrupting re-entry circuits
Adenosine acts on A1 receptors to transiently block AV nodal conduction, which interrupts the re-entry circuit responsible for most SVT.
Question 3: A 4-year-old with SVT converts to sinus rhythm after adenosine but then reverts to SVT 30 seconds later. What does this most likely indicate?
- Adenosine was the wrong drug and should not be repeated
- The dose was adequate but the underlying trigger needs treatment (Correct answer)
- The rhythm is actually VT and not SVT
- Adenosine should be given again at the same dose
Correct answer: The dose was adequate but the underlying trigger needs treatment
Recurrence of SVT after successful adenosine conversion often indicates a persistent underlying trigger (e.g., fever, electrolyte abnormality) or an accessory pathway; the next dose should be doubled or an alternative agent considered.
Question 4: What is the maximum single dose of adenosine in a pediatric patient?
- 6 mg
- 12 mg (Correct answer)
- 18 mg
- 0.5 mg/kg
Correct answer: 12 mg
The maximum single dose of adenosine in children is 12 mg, regardless of weight, to prevent excessive side effects.
Question 5: Which sign most reliably indicates that a child with tachycardia has progressed to cardiovascular compromise requiring immediate intervention?
- Heart rate above 180 bpm
- Altered mental status and poor perfusion despite tachycardia (Correct answer)
- Mild irritability and fussiness
- Mild tachypnea without retractions
Correct answer: Altered mental status and poor perfusion despite tachycardia
Altered mental status combined with poor perfusion (weak pulses, mottling, prolonged cap refill) indicates end-organ compromise and mandates immediate treatment.
Question 6: A 12-year-old athlete collapses on the field with a wide-complex tachycardia at 210 bpm and no pulse. What is the correct immediate intervention?
- Adenosine 0.1 mg/kg rapid IV
- Synchronized cardioversion at 1 J/kg
- Unsynchronized defibrillation at 2 J/kg (Correct answer)
- Amiodarone 5 mg/kg IV over 20 minutes
Correct answer: Unsynchronized defibrillation at 2 J/kg
Pulseless wide-complex tachycardia (VT without a pulse) is treated as VF: immediate unsynchronized defibrillation at 2 J/kg followed by CPR.
Question 7: During resuscitation of a child with pulseless VT, after the first defibrillation attempt and 2 minutes of CPR, the rhythm check reveals ongoing VT without a pulse. What drug is given next?
- Adenosine 0.1 mg/kg IV
- Epinephrine 0.01 mg/kg IV/IO (Correct answer)
- Verapamil 0.1 mg/kg IV
- Atropine 0.02 mg/kg IV
Correct answer: Epinephrine 0.01 mg/kg IV/IO
For shockable rhythms (pulseless VT/VF), epinephrine 0.01 mg/kg IV/IO is given after the second shock and then every 3-5 minutes during CPR.
PALS Tachycardia 5
A 6-year-old with SVT is being monitored; the team cannot obtain IV access.
What alternative route can adenosine be given?