6406259
Description
Flashcards by Andrew Street, updated more than 1 year ago
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Created by Andrew Street
over 8 years ago
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| Question | Answer |
| Indications for adenosine. | • SVT - 1st line diagnostic and therapeutic agent |
| MOA of adenosine. | Adenosine is an agonist of adenosine receptors on cell surfaces. In the HT, activation of these G protein-coupled receptors induces a number of effects, including reducing the frequency of spontaneous depolarisations (automaticity) & ^resistance to depolarisation (refractoriness). In turn, this transiently slows the sinus rate, conduction velocity, & ^AV node refractoriness. Many forms of SVT arise from a self-perpetuating electrical (re-entry) circuit that takes in the AV node. ^refractoriness in the AV node breaks the re-entry circuit, which allows normal depolarisations from the SA node to resume control of HR (cardioversion). Where the circuit does not involve the AV node (e.g. in atrial flutter), adenosine will not induce cardioversion. However, by blocking conduction to the ventricles, it allows closer inspection of the atrial rhythm on the ECG. This may reveal the diagnosis. The duration of effect of adenosine is very short because it is rapidly taken up by cells. Its half-life in plasma <10 secs. |
| SE's of adenosine. | • Bradycardia • Asystole • Can induce unpleasant sensations for the pt - 'a sinking feeling in the chest', SOB, a sense of 'impending doom' |
| CI's, warnings, & important interactions of adenosine. | CI's: • HT • Coronary ischaemia • Decompensated HT failure • Can induce bronchospasm so avoid in asthmatics/COPD Cautions: • HT transplant pt's as very sensitive to effects Important interactions: Dipyridamole blocks cellular uptake of adenosine, which prolongs & potentiates its effect: the dose of adenosine should be halved. Theophylline, aminophylline & caffeine are competitive antagonists of adenosine receptors & reduce its effect. Pt's who have taken these drugs respond poorly & may require higher doses. |
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