Adenosine on the NCLEX
Adenosine for SVT: rapid push with immediate flush, the expected pause, and what to tell the patient first.
Adenosine converts SVT by briefly stopping the AV node. Everything testable about it comes from a half-life measured in seconds.
What it is for
Stable SVT after vagal maneuvers fail. It blocks AV nodal conduction for a few seconds, which breaks the re-entry circuit driving the rhythm. Unstable SVT (hypotension, altered mentation, chest pain) gets synchronized cardioversion, not a drug.
How to give it
Half-life is under 10 seconds, so administration technique is the whole game: rapid IV push over 1-2 seconds, immediately followed by a 20 mL saline flush, through the most proximal port of a large IV (antecubital or better). A slow push metabolizes in the tubing and does nothing. First dose 6 mg; if no conversion, follow with 12 mg.
The pause
Expect a brief run of asystole or profound bradycardia on the monitor: a flat line for several seconds. This is the drug working, not an arrest. Run a continuous rhythm strip through the push so conversion is documented. Crash cart and pads nearby, because rarely the pause persists.
Warn the patient first
Tell them before you push: a few seconds of chest pressure, flushing, shortness of breath, and a feeling that something is very wrong. It passes in under a minute. An unwarned patient who feels their heart stop will not trust you again, and the NCLEX knows it: the teaching answer usually wins.
Cautions
Effects are potentiated in heart transplant recipients and by dipyridamole. Caffeine and theophylline blunt the effect. Bronchospasm can occur in severe asthma. None of that changes the core sequence: warn, push fast, flush, record.
Frequently asked
Why the immediate flush?
The drug dies in seconds. The flush slams the full dose into central circulation before it is metabolized.
The monitor shows asystole right after the push. Do you start CPR?
No. A several-second pause is the expected effect. Watch for the rhythm to resume; escalate only if it does not.
Adenosine for atrial fibrillation?
No. AFib is not AV-node dependent, so adenosine will not convert it. It can briefly unmask the underlying atrial activity, but that is diagnosis, not treatment.
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