Adenosine is an endogenous nucleoside that is capable of causing atrioventricular block when administered in pharmacological concentrations. It has the considerable advantage of having an ultra-short plasma half-life of only a few seconds. Side-effects are usually transient, and include flushing, chest tightness, and bronchospasm, although sustained acceleration of atrial flutter from 2:1 to 1:1 atrioventricular conduction has been reported. Atrioventricular block may persist for several seconds. It has superseded verapamil as the agent of choice for the acute termination of junctional re-entrant arrhythmias. It is administered as an extremely rapid intravenous bolus of between 3 and 20 mg in an escalating regime until therapeutic or diagnostic effect has been noted ( Camm and Garratll991) (Fig 1).

Adenosine also has a role in the diagnosis of arrhythmias, particularly broad complex arrhythmias where the non-cardiologist may not easily distinguish ventricular tachycardia from supraventricular arrhythmias conducted with aberration.

Fig. 1 Termination of atrial tachycardia with 12 mg of intravenous adenosine. Note impaired atrioventricular conduction in beats after successful termination.

Coping with Asthma

Coping with Asthma

If you suffer with asthma, you will no doubt be familiar with the uncomfortable sensations as your bronchial tubes begin to narrow and your muscles around them start to tighten. A sticky mucus known as phlegm begins to produce and increase within your bronchial tubes and you begin to wheeze, cough and struggle to breathe.

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