Understanding Adenosine (Adenocard)

So, recently, I was involved in a conversation, where the topic of Adenosine administration came up. It seems like there is a misunderstanding regarding its use and mechanism of action. Although this is not our classic ECG interpretation topic, I believe its worth talking about for a bit.

adenosine (1)

Adenosine, a Class V antiarrhythmic from the Vaughan Williams Classification, is an Endogenous Neucloside, meaning, already present in the body. In the EMS system, Adenosine is known for the treatment of Supraventricular Tachycardias (SVT), however, the reality is that, Adenosine is responsible for many actions in the body at a cellular level, depending on which receptor it binds to. During excessive reentry tachycardias (SVT), Adenosine, in simple terms, is given to slow down the overall ventricular rate.

Pharmacodynamics: 

  •  Adenosine binds to A1, one of multiple Adenosine receptors, which in the SA Node, it blocks L-type Calcium Channels and reduces Calcium influx, which may lead to a decreased firing rate, known as Negative Chronotropic Effect
  • Same channels at the AV Node, decrease conductivity , known as Negative Dromotropic Effect, down to the ventricles. This is what we want to do during tachyarrhythmias, especially with reentry capabilities, to slow down the ventricular rate

However, at higher or infused doses, such as during Cardiac Stress Test, Adenosine is given often as 60 mg over 4 minutes, not the typical administration for a reentry SVT right?

When infused slowly, Adenosine may bind to A2 receptors which in the heart and vasculature, can decrease Cyclic Adenosine Monophosphate (cAMP)

What is cAMP?

cAMP is a second messenger used to send signals from the cell membrane to intracellular areas to release chemicals like Calcium or break down proteins. Since Calcium is required for contraction and constriction, this leads to vasodilation. Physiologic changes in response to reduced blood pressure from vasodilation lead to increase heart rate to compensate for it. Understanding this details can help recognize complications that can happen when administrating Adenosine like AV blocks, short Asystole or other problems.

Other Adenosine receptors like Purinergic Receptors, for example, P1 receptors, lead to smooth muscle relaxation in the GI tracts.

Bottom line, Adenosine has many purposes in the body, therefore, it does not “die” or “dissapears” fast, but rather, it is used rapidly by the body, which is why it should be pushed fast, and as closed to the heart as possible, in order to reach the targeted areas during a reentry tachycardia, or “SVT”.

4 Comments

Leave a Reply

Your email address will not be published. Required fields are marked *

EMS 12-Lead

Cardiac Rhythm Analysis, 12-Lead ECG Interpretation, Resuscitation

JEMS Talk: Google Hangout

Comments
Ken Grauer, MD
Understanding Digoxin
Digoxin is used much less frequently these days than in the past - when it was a drug that virtually every patient with heart failure was taking. As a result - many clinicians in modern times are far less familiar (and comfortable) with how to dose Digoxin. Digoxin pharmacokinetics are linear - You double the…
2015-04-16 03:27:43
Ralph A
Transcutaneous Pacing Success!!! Part 1
Oh that was great....!!
2015-04-11 01:34:07
Ivan Rios
Understanding Amiodarone
I like your thought process. A Its not that Amiodarone is contraindicated in Hyperkalemia. In the event of arrest, Hyperkalemia usually leads to PEA and asystole. The Hyperkalemic effects on Action potential and Sodium potassium atpase channels should be addressed first in order for Amiodarone to work effectively. Once this is achieved, proper depolarization and…
2015-04-09 18:28:22
C galliher
Understanding Amiodarone
I hate cook book medics. I just do what my protocols say”.
2015-04-09 18:25:40
Chris g
Understanding Amiodarone
Cook book medic. I just do what my protocols say”.
2015-04-09 18:24:27

STEMI Expert?

  • Click here to find out!
  • 12-Lead ECG Challenge Smartphone App

    Photobucket

    12-Lead ECG Challenge Smartphone App - $5.99

  • Apple iOS
  • Android
  • Amazon
  • Web Based

  • FRN-TV video review
  • iMedicalApps.com review
  • Interested in resuscitation?

    FireEMS Blogs eNewsletter

    Sign-up to receive our free monthly eNewsletter

    Visitor Map / Stats

    Locations of visitors to this page


    LATEST EMS NEWS

    HOT FORUM DISCUSSIONS