Adenosine

[jwraider]

I was talking to someone recently (my preceptor) who said they would treat any rhythm over 150+ with adenosine. He was referring to atrial rhythms like Sinus tach, SVT, afib, and aflutter. I was somewhat perplexed because the mechanism of adenosine as I understand it is this:

Adenosine slows conduction time through the A-V node, can interrupt the reentry pathways through the A-V node, and can restore normal sinus rhythm in patients with paroxysmal supraventricular tachycardia (PSVT), including PSVT associated with Wolff-Parkinson-White Syndrome. Source

Which to me means it will have no direct effect on the SA node (sinus tach) or the atrium in general (afib/flutter) and potentially converts rhythms that are "re-entering" the atrium through extra pathways or the AV node.

I found a good web site that states "Adenosine is considered first line therapy for the investigation and termination of supraventricular tachycardias because of its efficacy and safety." and also goes onto explain the potential for creating new dysrhythmias with adenosine. Source

My definition for PSVT or SVT is a rhythm over 150 bpm that you can't see a P wave that is also regular with a narrow QRS. And SVT is the only rhythm I thought adenosine was for.

So I'm wondering if anyone can help me understand this further because my preceptor wants me to research the action of Adenosine further and come back to him. But I'm not finding anything that supports his methods and I don't feel it's a good idea to try and convince him I'm right. He is a great paramedic so either he's just off on this one issue or I don't fully understand the use of this drug clinically.

So would you use adenosine on Sinus tach at say 160bpm in a patient who is symptomatic but not ALOC (so not a cardio version candidate) ?

[Ghettomedic351]

Adenosine slows the conduction time through the AV node, and because it does this, it slows the ventricular conduction, which would be your QRS complex. Because it's slowing down that complex, it enables you to see what is going on in the atrias on the ECG. When the ventricles conduct the impulse, the QRS complex will over-ride and cover up what is going on in the atria thus making it impossible to determine the underlying rhythm. It's helpful to slow down the conduction to determine the underlying rhythm because it may alter your treatment, especially if you carry a decent cache of cardiac drugs (i.e., diltiazem, procainamide, amiodarone, etc.). Thus, the second bold part of your post: The investigation of supraventricular tachycardias. If it's PSVT the adenosine may terminate it, if it's a-fib with RVR you can slow the conduction enough to determine that is what the rhythm is, and treat according to patient presentation, with the correct medication.

I hope that was clearer than mud for you.

[Mateo_1387]

http://www.anaesthetist.com/icu/manage/dru...x.htm#index.htm

Try this site.

[jwraider]

Thanks guys.

That all makes sense that blocking the AV stops the ventricular response and let's you see what the atria is doing. Then you can treat appropriately. I guess what I'm getting at: what is the appropriate treatment once you know it's not a re-entry tachycardia? If it's Sinus Tach adenosine is doing nothing to fix the "problem" right? Because this is what I think he said he would do (treat a sinus tach with adenosine).

It doesn't make sense to me because the underlying problem that is creating a sinus tachycardia isn't something Adenosine will address.

Also thanks for the link I had no idea it had so many different effects on the body.

[defib_wizard]

when adenosine was first introduced it was widely taught that you could use it to slow down rhythms long enough to intepret them if needed as in a-fib with rvr versus svt. There are better ways of doing this than giving your pt 6-20 second of asystole. (remember do no harm)

sinus tach will change a little with O2 and IV fluid. It should also change with a vagal maneuver. A good hx will also help with this for differential dx.

A-fib with rvr will be slightly irreg even at rates >200

svt is usually very regular in rate and the pt typically complains or palpitations.

Another way to tell is increase the speed of your monitor tape to 50mm/sec if you have the option

[Just Plain Ruff]

now this is a great topic -that is all.

[spenac]

now this is a great topic -that is all.

I know how did this get in here while we were argueing about important things like pron and toys?

Thanks guys. As a paramedic student I have enjoyed reading this topic and it's links.

[jwraider]

I re-read my second Link and thoguht I'd repost to make sure other students found some of this stuff I'm finding helpful:

1) At the bottom it's saying Adenosine tends to preferentially block the anterograde AV pathway and cause a retrograde pathway or a re-entry pathway to be used actually causing a arrhythmia. Am I right in assuming this is a definite possibility for someone who is in Sinus tach?

2) Adenosine has additive effects with Digoxin, calcium channel blockers and beta blockers. You'll notice some of the seevre case studies gone awry the patient already had verapamil and digoxin on board.

3) Bronchospasm is a very possible side effect so be considerate of the PTs respiratory status. If they are SOB due to respiratory disease (versus cardiac reasons) use care.