How should adenosine be administered for supraventricular tachycardia?

How to Administer Adenosine for SVT

Administer adenosine as a rapid IV bolus through a proximal (large-bore) peripheral vein, starting with 6 mg, followed immediately by a 20 mL saline flush, with continuous ECG monitoring throughout the administration. 1

Administration Technique

Route and Preparation

• Use a proximal peripheral IV (antecubital or higher) for optimal delivery
• Have the adenosine dose drawn up and ready
• Prepare a 20 mL saline flush in a separate syringe
• Ensure continuous ECG recording is running before, during, and after administration 1

Injection Protocol

• Push the adenosine as a rapid bolus (over 1-2 seconds, not a slow push)
• Immediately follow with a rapid 20 mL saline flush to ensure the drug reaches central circulation before it degrades
• The extremely short half-life (seconds) means any delay in flushing will result in failure 1

Dosing Strategy

Standard peripheral dosing:

• First dose: 6 mg rapid IV bolus
• If no conversion after 1-2 minutes: 12 mg rapid IV bolus
• If still no conversion: 12 mg again (third dose) 2

This sequential approach achieves cumulative success rates of 57.4% after 6 mg and 93.4% after the second 12 mg dose 2.

Important dosing considerations:

• Recent evidence suggests the standard 6 mg initial dose may be suboptimal in heavier patients (>75-80 kg), with weight-adjusted dosing of 0.09-0.10 mg/kg potentially more effective 3, 4
• Some recent data support starting with 12 mg as the initial dose, showing 83% first-dose conversion versus 52% with 6 mg 4
• Central line dosing requires lower doses: Start with only 3 mg if administering through a central venous catheter, as 77% of patients convert with this dose centrally versus only 37% peripherally 5

Critical Safety Measures

Before Administration

• Have resuscitation equipment immediately available, including defibrillator and crash cart 1, 6
• Ensure the patient does NOT have:
  • Pre-excited atrial fibrillation (wide, irregular QRS) - adenosine is contraindicated
  • Severe asthma or active bronchospasm - adenosine is contraindicated 6
  • High-grade AV block without a pacemaker - adenosine is contraindicated 6

During Administration

• Warn the patient they will experience unpleasant but brief (<60 seconds) sensations: chest pressure/pain, dyspnea, flushing, sense of impending doom 1, 2
• Watch the monitor continuously - conversion typically occurs within 30 seconds of injection 2
• Document the rhythm strip showing the moment of conversion (or failure)

After Administration

• Watch for immediate recurrence - SVT can reinitiate within seconds to minutes in some patients 1
• Monitor for transient arrhythmias post-conversion (common and usually benign): premature atrial/ventricular beats, brief pauses 1
• Rare but serious: adenosine can precipitate atrial fibrillation, which in patients with WPW can conduct rapidly and degenerate to ventricular fibrillation 1, 6

Clinical Context and Alternatives

When Adenosine Fails or is Contraindicated

• Hemodynamically unstable patients: Proceed directly to synchronized cardioversion if adenosine fails or is not feasible 1
• Stable patients with failed adenosine: Consider IV calcium channel blockers (diltiazem, verapamil) or beta-blockers, though these have been downgraded in recent guidelines 7
• Pre-excited AF (irregular wide-complex): Use procainamide or ibutilide, NOT adenosine 1

Diagnostic Value

Even when adenosine doesn't terminate the arrhythmia, it provides diagnostic information by:

• Unmasking atrial flutter or atrial tachycardia through transient AV block
• Distinguishing true drug failure from successful termination with immediate reinitiation 1

Common Pitfalls to Avoid

1. Slow push or inadequate flush - The most common reason for adenosine failure is not pushing fast enough or failing to flush immediately and rapidly
2. Using a distal IV site (hand, wrist) - Drug degrades before reaching the heart
3. Not having the ECG recording - You lose critical diagnostic information
4. Giving adenosine for irregular wide-complex tachycardia - This may be pre-excited AF where adenosine is dangerous
5. Underdosing in obese patients - Consider higher initial doses (12 mg) or weight-based dosing in patients >80 kg 3, 4
6. Using standard peripheral doses through central lines - This delivers excessive drug to the heart; reduce to 3 mg initially 5