What is the initial management for a stable child presenting to the Emergency Department (ED) with Supraventricular Tachycardia (SVT) on Electrocardiogram (ECG)?

Initial Management of Stable Pediatric SVT in the Emergency Department

For a hemodynamically stable child with SVT, attempt vagal maneuvers first, followed immediately by adenosine if vagal maneuvers fail or are not feasible. 1

Immediate Assessment and Monitoring

Upon presentation, establish the following without delay:

• Maintain patent airway and administer oxygen 1
• Attach cardiac monitor and pulse oximetry to continuously assess rhythm and hemodynamic status 1
• Obtain IV/IO access for medication administration 1
• Record a 12-lead ECG if available, but do not delay therapy to obtain it 1

The key determination is whether the child shows signs of hemodynamic instability (hypotension, altered mental status, shock, chest pain, or acute heart failure), which would mandate immediate synchronized cardioversion instead of the stepwise approach below 2, 3.

First-Line Intervention: Vagal Maneuvers

Vagal maneuvers should be attempted first unless the patient is hemodynamically unstable or the procedure will unduly delay chemical or electrical cardioversion. 1

Age-Appropriate Techniques:

• For infants and young children: Apply ice to the face without occluding the airway (stimulates diving reflex) 1, 4
• For older children: Perform Valsalva maneuver (have the child blow through a narrow straw) or unilateral carotid sinus massage 1, 4

Vagal maneuvers have an overall success rate of approximately 27.7% 2, though effectiveness varies by age and SVT mechanism 1.

Second-Line Intervention: Adenosine

If IV/IO access is readily available, adenosine is the drug of choice for pharmacologic cardioversion. 1

Dosing Protocol:

• Initial dose: 0.1 mg/kg rapid IV bolus (maximum first dose: 6 mg) 1
• Second dose: 0.2 mg/kg rapid bolus (maximum second dose: 12 mg) 1
• Administration technique: Give as rapid bolus through a proximal/large vein, followed immediately by saline flush 1, 2

Expected Outcomes:

• Success rate: 90-95% for AVNRT and orthodromic AVRT 2
• First dose effectiveness: 56% in pediatric patients overall 5
• Second dose effectiveness: 50% of those who failed first dose 5

Critical Age Consideration:

Infants respond poorly to adenosine compared to older children. Only 1 of 17 episodes in infants responded to the first dose of adenosine in one study, and young age is associated with increased odds of adenosine-refractory SVT 5. The response to first-dose adenosine increases proportionally with age (OR 1.13 per year) 5.

Expected Side Effects:

Adenosine causes transient chest discomfort, shortness of breath, and flushing, which are minimal and self-limited 1, 2. Monitor rhythm continuously during administration to evaluate effect 1.

Management of Adenosine-Refractory SVT

If adenosine fails (occurs in approximately 15% of pediatric cases 5), consider:

• Procainamide IV: 15 mg/kg over 30-60 minutes 1
• Amiodarone IV: 5 mg/kg over 20-60 minutes 1

Do not routinely administer amiodarone and procainamide together. 1

Critical Pitfall to Avoid

Consultation with a pediatric arrhythmia expert is strongly recommended before treating hemodynamically stable children with medications beyond adenosine, as all antiarrhythmic therapies have potential for serious adverse effects. 1

When to Proceed to Synchronized Cardioversion

Even in initially stable patients, proceed immediately to synchronized cardioversion if:

• The patient develops hemodynamic instability at any point 1, 2
• Vagal maneuvers and adenosine both fail and the patient's condition deteriorates 1
• The rhythm is irregular and pre-excited atrial fibrillation is suspected (adenosine may precipitate ventricular fibrillation in this scenario) 2

Synchronized cardioversion is rarely performed for acute pediatric SVT but has essentially 100% success rate when indicated 3, 5.