Adenosine in Critical Care and Diagnostics

Vocabulary practice flashcards covering the pharmacologic classification, receptor mechanisms, clinical uses, side effects, contraindications, and dosing protocols of adenosine.

Adenosine

A naturally occurring organic compound and purine nucleoside (composed of adenine and a ribose molecule) classified as a class five or miscellaneous antiarrhythmic.

Pyrenergic adenosine receptors

A multitude of receptors distributed throughout the body that exert effects across the immune, cardiovascular, neurologic, respiratory, and urinary systems.

$A_1$ adenosine receptor

A receptor located in cardiac AV nodal tissue that slows impulse transmission by forcing potassium out of the cells and inhibiting calcium influx, producing a transient heart block at the AV node.

$A_{2b}$ receptor

A receptor found in endothelial tissue, specifically of arteries, whose activation leads to relaxation of smooth muscle and subsequent vasodilation.

Half-life of adenosine

An extremely short duration of approximately $10\,\text{seconds}$.

Adenosine side effects

Shortness of breath, chest pain or pressure, nausea, vomiting, headache, flushing, sweating, lightheadedness, dizziness, numbness, blurred vision, palpitations, arrhythmias, heart blocks, and hypotension.

Contraindications to adenosine

Conditions in which the drug should not be given, specifically second- or third-degree heart block, sick sinus syndrome, and in patients exhibiting signs and symptoms of an acute MI.

Supraventricular tachycardia (SVT)

A critical care arrhythmia indication for adenosine, which utilizes transient AV block to slow rapid rates, convert reentrant arrhythmias (such as AVRT and AVNRT), or expose underlying rhythms when heart rates exceed $150\,\text{bpm}$.

Ventricular asystole

A pause of a few seconds in ventricular activity that adenosine can cause immediately following administration.

Initial SVT dose of adenosine

A dose of $6\,\text{mg}$ administered by rapid IV push.

Three-way stopcock technique

A recommended administration setup attaching the adenosine syringe and a $10\,\text{ml}$ flush syringe together to push the drug rapidly and flush it immediately due to its ultra-short half-life.

Repeat SVT dosing of adenosine

A subsequent rapid IV push dose of $12\,\text{mg}$, which may be repeated one additional time if ineffective (never exceeding a single dose of $12\,\text{mg}$).

Regadenosine (Lexiscan)

An analog of adenosine with a longer half-life and greater receptor specificity, frequently selected for pharmacologic cardiac stress testing when exercise is not feasible.

Cardiac steel

A phenomenon during pharmacologic stress testing where endothelial-mediated dilation of coronary vessels provokes ischemia post-blockage, eliciting diagnostic chest pain.

Diagnostic stress test dosing of adenosine

An intravenous infusion of $140\,\mu\text{g/kg/min}$ administered continuously over a duration of $6\,\text{minutes}$.