What is the recommended dose of adenosine (adenosine) and normal saline (NS) to administer for supraventricular tachycardia (SVT) to normalize heart rhythm?

Adenosine Dosing for SVT

For stable SVT, administer 6 mg of adenosine as a rapid IV push through a large proximal vein (preferably antecubital), followed immediately by a 20 mL normal saline flush. 1, 2

Initial Dosing Protocol

• First dose: 6 mg adenosine IV push followed by 20 mL normal saline flush 1, 2
• Administer as a rapid bolus over 1-2 seconds through the largest accessible vein, preferably antecubital 1, 2
• The saline flush must be given immediately after the adenosine bolus to ensure the drug reaches the heart before its extremely short half-life (less than 10 seconds) renders it ineffective 1, 3

Subsequent Dosing if Initial Dose Fails

• If no conversion within 1-2 minutes: Give 12 mg IV push followed by 20 mL saline flush 1, 2
• If still no conversion: Repeat 12 mg IV push followed by 20 mL saline flush (one additional time) 1, 2
• Maximum total dose reported as safe is up to 24-30 mg, though standard protocols stop at 24 mg 1, 4

Critical Administration Technique

The American Heart Association emphasizes that adenosine must be given as a rapid IV push (injected over 1-2 seconds) followed immediately by the saline flush to maximize effectiveness 1. The drug should be administered "as proximal or as close to the heart as possible" 1. A recent study demonstrated that a single-syringe technique (diluting adenosine in 20 mL saline and giving as one bolus) was non-inferior to the traditional double-syringe technique, with 100% termination rate 5.

Dose Modifications

Reduce initial dose to 3 mg in these specific situations: 1, 2, 6

• Patients taking dipyridamole or carbamazepine
• Patients with transplanted hearts
• Administration via central venous access

Increase dose (may require higher than standard doses) for: 1, 2, 6

• Patients with significant blood levels of theophylline, caffeine, or theobromine
• Patients with impaired venous return (e.g., right heart failure, pulmonary hypertension) 3

Success Rates and Expectations

• The initial 6 mg dose successfully converts 70-80% of SVT cases 2, 4
• Overall success rate with adenosine (all doses combined) is 78-96% for AVNRT and AVRT 2
• Approximately 95% of AVNRT cases terminate with adenosine 2
• In prehospital settings, 70% of confirmed PSVT cases converted with the initial 6 mg bolus 4

Essential Monitoring and Safety

• Continuous ECG monitoring is mandatory during adenosine administration 1, 6
• Have a defibrillator immediately available, especially if Wolff-Parkinson-White syndrome is a consideration, as adenosine can precipitate atrial fibrillation with rapid ventricular rates 2
• Monitor for transient side effects including flushing, chest pain, dyspnea, and transient AV block—these typically resolve within 60 seconds due to adenosine's ultra-short half-life 1, 2

Absolute Contraindications

Do not give adenosine in these situations: 1, 6

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

Common Pitfall to Avoid

The most common error is administering adenosine too slowly or through a distal/small vein, which allows the drug to be metabolized before reaching the heart 1, 3. This is why the American Heart Association specifically recommends using a large proximal vein (antecubital preferred) with rapid push administration 1, 2. Failure to follow this technique is a primary reason for apparent "adenosine failure" in SVT treatment.

If Adenosine Fails

After maximum adenosine dosing, consider: 1, 2, 6

• Longer-acting AV nodal blocking agents such as diltiazem (0.25 mg/kg IV over 2 minutes) or metoprolol (2.5-5 mg IV bolus)
• Synchronized cardioversion if patient becomes hemodynamically unstable