When is Adenosine indicated in the Advanced Cardiovascular Life Support (ACLS) protocol?

Adenosine Indications in the ACLS Protocol

Intravenous adenosine is indicated in the ACLS protocol for the acute treatment of supraventricular tachycardia (SVT) in hemodynamically stable patients. 1, 2

Primary Indications

• First-line pharmacological therapy for narrow-complex regular tachycardias after vagal maneuvers have failed
• Diagnostic tool for differentiating SVT mechanisms when the rhythm is unclear
• Therapeutic agent for terminating SVT that involves the AV node in the reentrant circuit

Specific SVT Types Where Adenosine is Indicated

1. AVNRT (AV Nodal Reentrant Tachycardia)

   • Highly effective with 95% success rate 2
   • Class I, Level B-R recommendation 1

2. AVRT (AV Reciprocating Tachycardia)

   • Effective for accessory pathway-mediated tachycardias 1
   • Particularly useful in orthodromic AVRT

3. Some forms of focal Atrial Tachycardia

   • May terminate certain types of focal AT 1

Diagnostic Value

• Helps differentiate between various SVT mechanisms by:
  • Producing transient AV block that makes atrial activity visible 1
  • Revealing underlying rhythm in wide-complex tachycardias of uncertain origin
  • Distinguishing between SVT with aberrancy and ventricular tachycardia

When Adenosine is NOT Effective (but still diagnostically useful)

• Atrial flutter or atrial reentry tachycardia (>70% of SVT episodes in adults with repaired congenital heart disease) 1
• Atrial fibrillation
• Ventricular tachycardia

Administration Protocol

1. Initial dose: 6 mg rapid IV bolus
2. If ineffective after 1-2 minutes: 12 mg IV bolus
3. May repeat 12 mg dose once more if necessary
4. Always follow with rapid saline flush

Important Considerations and Precautions

• Short half-life (0.6-10 seconds) makes it safer than other agents 3

• Common side effects include flushing, dyspnea, chest pain, and brief bradycardia

• Use with caution in patients with:

  • Severe asthma (relative contraindication)
  • Patients on theophylline (may require higher doses)
  • Patients on dipyridamole (effects are potentiated)
  • Patients on carbamazepine (higher risk of heart block)

• High recurrence rate (up to 57%) may necessitate additional therapy with other antiarrhythmic agents 4

Position in ACLS Algorithm for SVT

1. Assess hemodynamic stability
2. If unstable: immediate synchronized cardioversion
3. If stable:
   • First: Vagal maneuvers
   • Second: Adenosine (6 mg, then 12 mg if needed)
   • Third: Calcium channel blockers (diltiazem/verapamil) or beta blockers
   • Fourth: Consider synchronized cardioversion if medications fail

Special Populations

• ACHD (Adult Congenital Heart Disease) patients: Adenosine is recommended for acute treatment of SVT 1
• Pregnancy: Adenosine is considered safe due to its short half-life 2
• Post-cardiac arrest: Can be used for SVT occurring after resuscitation 5

Remember that adenosine should never delay cardioversion in hemodynamically unstable patients, and proper rhythm identification is crucial for appropriate management.