How to initiate an adenosine infusion?

How to Initiate an Adenosine Infusion

For pharmacologic stress testing (myocardial perfusion imaging), administer adenosine as a continuous intravenous infusion at 140 mcg/kg/min (0.14 mg/kg/min) over 6 minutes through a large peripheral vein, with the radiotracer injected at the 3-minute midpoint. 1

Dosing Protocol for Stress Testing

• Total dose: 0.84 mg/kg administered over the full 6-minute infusion period 1
• Infusion rate calculation: Use the formula: 0.14 (mg/kg/min) × patient weight (kg) ÷ 3 (mg/mL concentration) = infusion rate in mL/min 1
• Radiotracer timing: Inject Thallium-201 or other imaging agent at exactly 3 minutes into the adenosine infusion (the midpoint) 1
• Injection technique: Administer the radiotracer as close to the venous access site as possible to prevent inadvertent bolus increases in adenosine dose from IV tubing contents 1

Route and Access Requirements

• Administer only as a continuous peripheral intravenous infusion through a large vein, preferably a central vein 2, 1
• The intracoronary route has not been established for infusion protocols (though bolus intracoronary dosing exists for catheterization procedures) 1
• Ensure adequate IV access before beginning, as interruption of continuous delivery can cause fluctuations in coronary blood flow 3

Pre-Infusion Preparation

• Visually inspect adenosine solution for particulate matter or discoloration; do not administer if present 1
• Have resuscitative equipment and personnel immediately available, including a defibrillator 4, 1
• Establish continuous ECG monitoring throughout the procedure 4, 1
• Ensure patient has avoided methylxanthines (caffeine, theophylline, aminophylline) as these competitively antagonize adenosine's effects 3, 1

Monitoring During Infusion

• Continuous ECG monitoring is mandatory to detect AV block, bradycardia, or arrhythmias 4, 1
• Monitor blood pressure, as significant hypotension can occur 1
• Watch for respiratory distress, particularly in patients with any pulmonary disease history 1
• Common transient symptoms include flushing, chest discomfort, dyspnea, headache, and throat/neck/jaw discomfort—these typically resolve within 1-2 minutes of stopping the infusion 1, 5

Absolute Contraindications

• Bronchoconstrictive or bronchospastic lung disease (including asthma)—this is an absolute contraindication due to risk of severe bronchospasm 2, 1
• Second- or third-degree AV block or sick sinus syndrome (unless functioning pacemaker present) 4, 1
• Known hypersensitivity to adenosine 1

Important Safety Considerations

• Avoid Valsalva maneuvers during infusion as this interrupts drug delivery and causes fluctuations in coronary blood flow 2, 3
• Reduce initial dose to 3 mg for bolus protocols (not applicable to infusion) in patients taking dipyridamole or carbamazepine, those with transplanted hearts, or when using central venous access 3
• Be prepared to discontinue immediately if severe respiratory difficulties, persistent high-grade AV block, or symptomatic hypotension develop 1
• Rare but serious complications include cardiac arrest, ventricular arrhythmias, myocardial infarction, cerebrovascular accidents, and seizures 1

Alternative Dosing for Stress Echocardiography

• For adenosine stress echocardiography, the protocol uses 140 mcg/kg/min for up to 6 minutes with contrast agent infusion and imaging at rest, during adenosine infusion (starting 1 minute after adenosine begins), and during recovery 4
• Increase adenosine dosage by 20 mcg/kg/min (up to 220 mcg/kg/min maximum) if patient shows no signs of adenosine effect such as flushing, heart rate changes, or increased coronary flow velocity 4

Key Distinction: Infusion vs. Bolus

Note that adenosine infusion (for stress testing) differs fundamentally from adenosine bolus administration (for arrhythmia termination). The bolus protocol uses rapid IV push of 6-12 mg over 1-2 seconds followed by saline flush, which is NOT the same as the continuous infusion protocol described here 4, 6.