What is the recommended dose and treatment protocol for adenosine (adenosine) in pediatric patients with supraventricular tachycardia (SVT)?

Adenosine for Pediatric SVT

Adenosine is highly effective and safe for treating supraventricular tachycardia in children, with an initial dose of 0.1 mg/kg (100 mcg/kg) recommended as the starting bolus, followed by 0.2 mg/kg (200 mcg/kg) if needed, up to a maximum of 0.3 mg/kg (300 mcg/kg). 1

Recommended Dosing Protocol

Initial Dose

• Start with 0.1 mg/kg (100 mcg/kg) as a rapid IV bolus 1, 2, 3
• This is higher than the adult starting dose of 6 mg and reflects the higher doses needed in children compared to adults 1
• Administer via a large proximal vein followed immediately by a rapid 5-10 mL saline flush 4

Escalation Strategy

• If no response after 1-2 minutes, give 0.2 mg/kg (200 mcg/kg) 1, 2, 3, 5
• If still no response, give 0.3 mg/kg (300 mcg/kg) as the final dose 3, 6
• The median effective dose in pediatric studies is 200 mcg/kg, with only 36% of children responding to the initial 100 mcg/kg dose 3

Maximum Dose

• Do not exceed 0.3 mg/kg per dose 3, 6
• Some older guidelines mentioned 0.25 mg/kg as maximum, but recent evidence supports up to 0.3 mg/kg 7, 3

Clinical Efficacy

Success Rates

• Overall cardioversion success rate is 72-88% for all SVT types 2, 6
• For AV node-dependent SVT (the most common type), success rate reaches 79-96% 1, 2, 6
• Approximately 90% success rate when adenosine or verapamil are used, superior to digoxin (61-71%) 1

Important Considerations

• Early re-initiation of SVT occurs in 25% of episodes after successful cardioversion 2
• This is due to adenosine's extremely short half-life (0.6-10 seconds), so have additional antiarrhythmic therapy ready if prophylaxis is needed 7

Special Populations

Pre-excitation (Wolff-Parkinson-White)

• Children with pre-excitation require significantly higher doses (mean 220.8 mcg/kg vs. 177.2 mcg/kg in those without pre-excitation, p=0.039) 3
• Consider starting at 0.2 mg/kg in patients with known or suspected pre-excitation 3

Infants and Neonates

• Adenosine is safe and effective even in critically ill infants requiring mechanical ventilation 7
• Use the same weight-based dosing protocol 1, 7
• Twenty-five percent of pediatric SVT episodes occur in infants under 1 year of age 6

Patients on Cardiac Medications

• Adenosine can be safely used in children already taking digoxin 6
• However, avoid verapamil in infants due to risk of severe hypotension, bradycardia, heart block, and death 1

Administration Technique

Critical Steps

• Use a large, proximal peripheral vein (antecubital preferred) 4
• Administer as the most rapid IV push possible 4, 7
• Immediately follow with 5-10 mL rapid saline flush 4
• Monitor continuously with ECG, blood pressure, and pulse oximetry 7

Common Pitfall

• Slow administration or inadequate flush will result in treatment failure due to adenosine's ultra-short half-life 7

Adverse Effects

Expected Transient Effects (resolve in seconds)

• Flushing, chest discomfort, dyspnea, irritability 1, 7, 5, 6
• Brief sinus bradycardia or varying degrees of AV block 7, 5
• Transient ventricular ectopics (3-5 seconds) 5
• Mild hypotension (lasting <45 seconds) 5

Serious Adverse Effects

• No significant adverse effects occurred in multiple pediatric studies 2, 5, 6
• No cases of bronchospasm or hemodynamically significant arrhythmias were reported 6
• All side effects are transient due to the drug's extremely short half-life 7, 5

Contraindications

Absolute Contraindications

• Second- or third-degree AV block (unless functioning pacemaker present) 8
• Sick sinus syndrome or symptomatic bradycardia (unless functioning pacemaker present) 8
• Known bronchospastic lung disease (asthma) 8
• Known hypersensitivity to adenosine 8

Important Note on Asthma

• Despite theoretical concerns, no bronchospasm was reported in pediatric studies, including 13 patients with asthma history 6
• However, FDA labeling maintains asthma as a contraindication 8

Alternative Therapies for Refractory SVT

When Adenosine Fails

• Procainamide has higher success rates than amiodarone for refractory pediatric SVT with equal adverse effects 1
• Synchronized cardioversion is preferred for unstable patients or when pharmacologic therapy fails 1
• Avoid verapamil in infants due to multiple reports of cardiovascular collapse and death 1

Hemodynamically Unstable Patients

• Proceed directly to synchronized cardioversion rather than attempting adenosine 1

Key Clinical Pearls

• Higher initial doses (0.1 mg/kg) are more effective than the older recommended 0.05 mg/kg starting dose, with only 16% responding to 0.05 mg/kg versus 36% to 0.1 mg/kg 2, 3
• Adenosine can be used diagnostically to elicit occult pre-excitation patterns after cardioversion 2, 5
• Have resuscitation equipment immediately available, though serious complications are extremely rare 4, 8
• The drug's ultra-short half-life is both an advantage (transient side effects) and disadvantage (frequent SVT recurrence) 7