What is the correct technique and dosing for intravenous adenosine administration in an adult with regular narrow‑complex supraventricular tachycardia and no contraindications?

How to Give Inj Adenosine

Administer adenosine as a 6 mg rapid IV bolus through the most proximal IV site possible (as close to the heart as feasible), injected over 1-2 seconds, immediately followed by a rapid 20 mL saline flush, with the patient supine. 1

Initial Dose and Administration Technique

• First dose: 6 mg as a rapid IV bolus over 1-2 seconds 1
• Critical technique points:
  • Use the most proximal IV site available (closest to the heart) 1
  • Inject rapidly over 1-2 seconds—speed is essential due to adenosine's extremely short half-life (<10 seconds) 1
  • Immediately follow with rapid saline flush (typically 20 mL) 1
  • Patient should be supine during administration 2

Subsequent Dosing if Initial Dose Fails

• If no response within 1-2 minutes: Give 12 mg rapid IV bolus 1
• Can repeat the 12 mg dose one additional time if needed 1
• The 18 mg bolus dose has been reported as safe in refractory cases 1

Critical Timing and Monitoring

• Continuous ECG monitoring is mandatory during administration 1
• Average time to termination of tachycardia is 30 seconds after injection 3
• Success rates: 57.4% with 6 mg, increasing to 93.4% after the 12 mg dose 3

Important Caveats and Pitfalls

Central vs. Peripheral Administration:

• If using a central line, start with only 3 mg (not 6 mg), as central administration requires significantly lower doses 4
• 77% of patients respond to 3 mg centrally vs. only 37% peripherally 4

Patient Factors Affecting Dosing:

• Higher body weight reduces first-dose success—patients weighing >80 kg have lower conversion rates with standard 6 mg dosing 5
• Patients with impaired venous return (right heart failure, pulmonary hypertension) may require higher doses due to delayed drug delivery 6
• Methylxanthines (caffeine, theophylline, aminophylline) antagonize adenosine—higher doses may be needed 1, 7
• Dipyridamole potentiates adenosine—use lower doses or avoid 1, 7

Safety Considerations:

• Have resuscitation equipment immediately available 2, 1
• Side effects (flushing, chest discomfort, dyspnea) occur in 30-36% but last <1 minute 3, 1
• Do not use in patients with second/third-degree AV block, sick sinus syndrome, asthma/bronchospasm, or known hypersensitivity 7
• Can precipitate atrial fibrillation with rapid ventricular response in pre-excitation syndromes—have cardioversion ready 1

Post-Conversion Management:

• Atrial or ventricular premature complexes immediately after conversion may reinitiate tachycardia 1
• Consider antiarrhythmic prophylaxis if immediate recurrence occurs 1

Alternative if Adenosine Fails

If adenosine fails after maximum dosing (6 mg → 12 mg → 12 mg), proceed to:

• Synchronized cardioversion if hemodynamically unstable 2, 1
• IV calcium channel blockers (diltiazem or verapamil) or beta-blockers if stable 2

The arm elevation technique (raising arm to 90° for 10 seconds after injection) shows no significant benefit over standard technique 8.