Tachycardia - treatment with adenosine

• Adenosine slows conduction time through the A-V node, can interrupt the reentry pathways through the AV node, and can restore normal sinus rhythm in patients with paroxysmal supraventricular tachycardia (PSVT), including PSVT associated with Wolff- Parkinson-White Syndrome. Intravenously administered adenosine is rapidly cleared from the circulation via cellular uptake, primarily by erythrocytes and vascular endothelial cells. Adenosine has a half- life of less than 10 seconds in whole blood.

ADMINISTRATION ROUTES: IV

ALTERNATIVE NAMES: Adenocor

ICU INDICATIONS:

1. Conversion to sinus rhythm of paroxysmal supraventricular tachycardia (PSVT), including that associated with accessory bypass tracts (Wolff-Parkinson-White Syndrome).

PRESENTATION AND ADMINISTRATION:

• IV: Adenosine comes in a vial containing 6mg in 2mls solution
• Compatible with the following IV fluids: Normal Saline Store at room temperature
• DO NOT REFRIGERATE as crystallisation may occur. The solution must be clear at the time of use.

DOSAGE:

• Adenosine injection should be given as a rapid bolus by the peripheral IV route. It should be given as close to the patient as possible and followed by a rapid saline flush (this is best achieved by using a three-way tap system) The recommended IV doses for adults are as follows: Initial dose: 6 mg given as a rapid IV bolus (administered over a 1-2 second period). Repeat administration: If the first dose does not result in elimination of the supraventricular tachycardia within 1-2 minutes, 12 mg should be given as a rapid IV bolus. This 12 mg dose may be repeated a second time if required. Central venous administration of adenosine has not been systematically studied; however, in the ICU setting this route of administration is acceptable.

DOSAGE IN RENAL FAILURE AND RENAL REPLACEMENT THERAPY:

• No dosage adjustment is required in renal failure or renal replacement therapy.

DOSAGE IN PAEDIATRICS:

• Paediatric Patients with a Body Weight < 50 kg:
  • Initial dose: Give 0.05 to 0.1 mg/kg as a rapid IV bolus given either centrally or peripherally. A saline flush should follow.
  • Repeat administration: If conversion of PSVT does not occur within 1-2 minutes, additional bolus injections of adenosine can be administered at incrementally higher doses, increasing the amount given by 0.05 to 0.1 mg/kg. Follow each bolus with a saline flush. This process should continue until sinus rhythm is established or a maximum single dose of 0.3 mg/kg is used.
• Paediatric Patients with a Body Weight > 50 kg: Administer the adult dose.

CLINICAL PHARMACOLOGY:

• Adenosine slows conduction time through the A-V node, can interrupt the reentry pathways through the AV node, and can restore normal sinus rhythm in patients with paroxysmal supraventricular tachycardia (PSVT), including PSVT associated with Wolff- Parkinson-White Syndrome. Intravenously administered adenosine is rapidly cleared from the circulation via cellular uptake, primarily by erythrocytes and vascular endothelial cells. Adenosine has a half- life of less than 10 seconds in whole blood.

CONTRAINDICATIONS:

1. Second- or third-degree A-V block (except in patients with a functioning artificial pacemaker).
2. Sinus node disease, such as sick sinus syndrome or symptomatic bradycardia (except in patients with a functioning artificial pacemaker).
3. Known hypersensitivity to adenosine.

WARNINGS

• Heart Block: Adenosine injection exerts its effect by decreasing conduction through the A-V node and may produce a short lasting first-, second- or third-degree heart block. Appropriate therapy should be instituted as needed. Patients who develop high-level block on one dose of adensoine should not be given additional doses. Because of the very short half- life of adenosine, these effects are generally self-limiting.
• Asystole and VF: Transient or prolonged episodes of asystole have been reported with fatal outcomes in some cases. Rarely, ventricular fibrillation has been reported following adenosine administration, including both resuscitated and fatal events. In most instances, these cases were associated with the concomitant use of digoxin and, less frequently with digoxin and verapamil. Although no causal relationship or drug-drug interaction has been established, adenosine should be used with caution in patients receiving digoxin or digoxin and verapamil in combination.
• Arrhythmias at Time of Conversion: At the time of conversion to normal sinus rhythm, a variety of new rhythms may appear on the electrocardiogram. They generally last only a few seconds without intervention, and may take the form of premature ventricular contractions, atrial premature contractions, sinus bradycardia, sinus tachycardia, skipped beats, and varying degrees of A-V nodal block. Such findings are seen in 55% of patients.
• Bronchoconstriction: Adenosine has been administered to a limited number of patients with asthma and mild to moderate exacerbation of their symptoms has been reported. Adenosine should be used with caution in patients with obstructive lung disease or asthma. Adenosine should be discontinued in any patient who develops severe respiratory difficulties.

PRECAUTIONS

• General: See CONTRAINDICATIONS and WARNINGS

IMPORTANT DRUG INTERACTIONS FOR THE ICU

• Digoxin with or without verapamil use may be rarely associated with ventricular fibrillation when combined with adenosine (see WARNINGS).
• The effects of adenosine are antagonised by methylxanthines such as caffeine and theophylline. In the presence of these methylxanthines, larger doses of adenosine may be required or adenosine may not be effective.
• Adenosine effects are potentiated by dipyridamole (persantin). Thus, smaller doses of adenosine may be effective in the presence of dipyridamole.
• Carbamazepine has been reported to increase the degree of heart block produced by adenosine.

ADVERSE REACTIONS

• The half-life of adenosine is less than 10 seconds. Thus, adverse effects are generally rapidly self-limiting.
• Body as a Whole: Apprehension
• Cardiovascular System: Facial flushing, headache, sweating, palpitations, chest pain, hypotension
• Respiratory System: Bronchospasm, shortness of breath/dyspnea, chest pressure
• Digestive System: Nausea, metallic taste, tightness in throat, pressure in groin.
• Nervous System: Lightheadedness, dizziness, tingling in arms, numbness, blurred vision, burning sensation

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http://lifeinthefastlane.com/book/critical-care-drugs/adenosine/