When should adenosine be given to a patient with supraventricular tachycardia (SVT)?

Adenosine Administration for Supraventricular Tachycardia

Adenosine should be administered for SVT after vagal maneuvers have failed in hemodynamically stable patients, with an initial dose of 6 mg IV push followed by a 20 mL saline flush, and if necessary, up to two additional 12 mg doses at 1-2 minute intervals. 1

Indications for Adenosine

• Adenosine is indicated as first-line pharmacological therapy for regular, narrow-complex SVT after vagal maneuvers have failed, with success rates of 78-96% in terminating AVNRT and AVRT 1
• Adenosine is particularly effective for SVTs that involve the AV node in the reentrant circuit, including AV nodal reentrant tachycardia (AVNRT) and AV reciprocating tachycardia (AVRT) 2
• For hemodynamically unstable SVT, synchronized cardioversion is the primary treatment, though adenosine may be considered first if the tachycardia is regular with narrow QRS complexes 1

Administration Protocol

• Administer adenosine via a large proximal vein (e.g., antecubital) as a rapid IV push followed immediately by a 20 mL saline flush 3
• Initial dose: 6 mg IV push 3, 1
• If rhythm does not convert within 1-2 minutes, administer 12 mg IV push 3
• A third dose of 12 mg may be given if necessary after another 1-2 minutes 1
• Continuous ECG recording during administration helps diagnostically and distinguishes between drug failure and successful termination with immediate reinitiation 1

Diagnostic Value

• Adenosine serves as both a therapeutic and diagnostic agent for narrow-complex tachyarrhythmias 1
• For arrhythmias not involving the AV node (atrial flutter, atrial fibrillation), adenosine produces transient AV block without terminating the arrhythmia, which can help unmask the underlying atrial activity 2
• A defibrillator should be available when administering adenosine to any patient in whom Wolff-Parkinson-White syndrome is a consideration, due to the possibility of initiating atrial fibrillation with rapid ventricular rates 3

Special Considerations

• Larger doses may be required for patients with significant blood levels of theophylline, caffeine, or theobromine 3
• Reduce the initial dose to 3 mg in patients taking dipyridamole or carbamazepine, those with transplanted hearts, or if given by central venous access 3
• Adenosine is safe and effective during pregnancy 3, 1
• Adenosine should not be given to patients with asthma due to risk of bronchospasm 3
• Patients with impaired venous return to the right heart (e.g., pulmonary hypertension with right heart failure) may require higher-than-recommended doses of adenosine 4

Post-Conversion Management

• Monitor the patient for recurrence after conversion 3, 5
• Maintain continuous cardiac monitoring for at least 1-2 hours after successful conversion 5
• Treat any recurrence with adenosine or consider a longer-acting AV nodal blocking agent (e.g., diltiazem or β-blocker) 3, 5
• If adenosine reveals another form of SVT (such as atrial fibrillation or flutter), consider treatment with a longer-acting AV nodal blocking agent 3

Common Side Effects

• Side effects are common but transient due to adenosine's extremely short half-life (less than 10 seconds) 6
• Most common side effects include flushing, dyspnea, and chest discomfort 3
• Transient ventricular ectopy may occur but typically resolves within seconds 7