Friday, 10 September 2010

MRCP revision battle 7.4: Adenosine

Adenosine is a purine nucleoside which clinically is used to try and terminate SVTs/expose the underlying rhythm.  While doing so it has the potential to cause cardiac standstill, so it can have a unique dual action of increasing the adminstering doctor's heart rate in proportion to how much it decreases the receiving patients heart rate.

It's half life is 8 to 15 seconds, and it works by activating potassium channels which decreases AVN conduction.

The effect of adenosine is increased by dipridamol and carbamezepine.
The effect of adenosine is decreased by aminophylline.

A positive of adenosine is that it has no significant negatively inotropic effects.

Risks associated with its use include:
  • enhancing conduction through the accessory pathway in Wolff-Parkinson-White
  • causing a dangerously fast ventricular response in pre-excited AF/flutter

The side effects include:
  • anxiety
  • chest tightness
  • bronchospasm (avoid in asthma)
  • facial flushing
  • nausea

The usual dosing regime is 6mg, then if unsuccessful 12mg 2 mins later and if still unsuccessful another 12mg 2 mins after that.  Ensure cardiac monitoring is in place when it is given (it can cause cardiac standstill) and remember that given its short halflife it must be given as a rapid bolus, flushed instantly with saline.

So to the final revision battle of the day, with that most feared ECG pattern: the broad complex tachycardia.