Intensive Care Paramedic Drugs - Adenosine

Front 1

What are the contraindications for adenosine?

Back 1

1. Sick sinus syndrome with out a pacemaker

2. Previous 2nd or 3rd HB with out a pacemaker
3. Heart transplantation (denervated)

All the contraindications relate to the risk of causing life threatening bradycardia.

Front 2

What are the precautions to adenosine use?

Back 2

1. Asthma

2. CORD

May cause bronchospasm due to the decreased cyclic adenosine monophosphate production. (G protein receptor)

Front 3

Describe the administration of adenosine?

Back 3

1. Adults only / Child requires consultation

2. 6mg/2ml undiluted as a rapid push into the right ACF with 20ml saline as a rapid push

3. Repeated if ineffective at 12mg/4ml.

Front 4

What is the onset of effect and duration of effect?

Back 4

1. 2-5 seconds on set

2. 10 -20 seconds duration due to it being metabolised by erythrocytes and vascular endothelial cells.

Front 5

What receptors dose adenosine work on?

Back 5

There are 4 adenosine receptors
a1, a2a, a2b, & a3. They are all G protein coupled

Front 6

Describe the mechanism of action for adenosine?

Back 6

1. Causes a HB at the AV node

2. This is mediated by the a1 receptor

3. Inhibits adenylyl cyclase

4. Thus decreases cAMP (cyclic adenosine monophosphate)
5. This cause hyperpolarisation as potassium moves out

6. Now there is a delay in conduction thus allowing the termination of a re entry tachycardia

Front 7

Describe the pharmacokinetics of adenosine?

Back 7

1. Short duration

2. Due to its rapid uptake & metabolism by erythrocytes and vascular endothelia cells.

Front 8

Describe the pharmacodynamics of adenosine?

Back 8

1. Adenosine is endogenous nucleoside

2. Exerts its pharmacological effect on adenosine receptors

3. Also relaxes vascular smooth muscle due to a reduced calcium uptake

4. Has -ve chronotopic, dromotropic, & inotropic effects.

Front 9

Talk about the elimination of adenosine.

Back 9

1. Metabolised by the cell and converted to adenosine monophosphate.

2. There is no renal or hepatic clearance required

Front 10

Is Wolff-Parkinson White syndrome a contraindication to adenosine administration?

Back 10

1. No

2. But the rhythm must clearly be SVT

3. If there is a chance it is fast AF it is contraindicated.

4. Adenosine may cause VF if given in fast AF

Front 11

Dose adenosine reduce cardiac output?

Back 11

1. Yes

2. Due to the creation of HB at the AV node

3. Also due to the inhibition of calcium uptake into vascular smooth muscle causing hypotension through vasodilation

Front 12

What are the common adverse effects of adenosine?

Back 12

Bradycardia, Sinus pause, ventricular ectopy, SOB, urge to breath deeply, bronchospasm, headache, light-headedness, nausea, flushing, feeling of chest pressure, & feeling of apprehension

Front 13

Are there any interactions with adenosine?

Back 13

Yes

1.Dipyridamole (inhibits thrombus formation) inhibits the uptake of adenosine producing a prolonged effect (40seconds).
2. *diazepam may have a similar effect

3. Caffine will reduce its effectiveness