Adenosine

In this lesson, we'll go over the medication adenosine and all of its effects, including indications, precautions and contraindications, and adult dosages. At the end of the lesson, we'll provide you with a Word about defibrillation.

Adenosine is effective at terminating narrow complex SVT due to a reentry involving the AV or sinus node. It's used for unstable narrow complex reentry tachycardia and should be given to the patient while also preparing to cardiovert.

Adenosine Indications

Indications for adenosine include:

• Narrow complex SVT
• Unstable narrow complex reentry tachycardia
• Regular and monomorphic wide complex tachycardia
• As a diagnostic maneuver for stable narrow complex SVT

Adenosine Precautions and Contraindications

There are some adenosine precautions and contraindications to be aware of, including:

• Poison or drug induced tachycardia
• 2nd or 3rd degree heart blocks
• Bronchoconstriction or asthma
• Irregular, polymorphic wide-complex tachycardia/VT (may cause patient deterioration)

Adenosine is safe to administer to pregnant patients.

Adenosine side effects include:

• Transient periods of flushing
• Chest pain
• Chest tightness
• Brief periods of asystole
• Brief periods of bradycardia
• Ventricular ectopy

Adult Dosage of Adenosine

Adenosine should be delivered via rapid IV push and follow the steps below when administering the drug.

1. Ensure your venous access is at the AC or above with at least an 18 ga. IV.
2. Place the patient in a moderate reverse Trendelenburg position before administering the drug. It is highly recommended that whatever extremity in which adenosine is administered is elevated.
3. A simple trick for easy administration is to set up a 3-way stop cock with adenosine one on side and 20 mL normal saline flush on the other.
4. Before, during and just after administering the medication, make sure your cardiac monitor is recording rhythm changes.
5. Rapidly administer the initial bolus of 6 mg.
6. Immediately follow the adenosine with the rapid normal saline flush.
7. Monitor the patient for desired outcomes.
8. A 2nd dose of 12 mg of adenosine can be given after 1 to 2 minutes if needed.

A Word (or Two) About Defibrillation

The Purpose of Defibrillation

Defibrillation does not restart the heart. Defibrillation only stuns the heart and briefly terminates all electrical activity, including V-fib and pulseless V-tach. If the heart is still viable, its normal pacemakers can eventually resume electrical activity, such as a return of spontaneous circulation, that ultimately results in a perfusing rhythm.

In the first minutes after successful defibrillation, however, any spontaneous rhythm is typically slow and may not create pulses or adequate perfusion. So we need to immediately resume CPR with compressions following every shock. 

Remember, not all shocks will lead to successful defibrillation. Which is also why it's important to resume high-quality CPR right away.

Clearing for Defibrillation

To ensure safety during defibrillation, always announce the shock warning. State the warning firmly and in a forceful voice before delivering each shock. This entire shock warning sequence should take less than 5 seconds:

1. Announce the shock – clear!
2. Check to make sure you're clear of contact with the patient, the stretcher, or other equipment.
3. Make a visual check to make sure that no other member of the team is touching the patient, stretcher, or other equipment.
4. Make sure oxygen isn't flowing across the patient's chest.
5. Deliver the shock to the patient.
6. Immediately resume CPR compressions.

When pressing the shock button, the operator of the defibrillator should be facing the patient, not the machine. This helps to ensure coordination with the chest compressor and to verify that no one accidentally resumed contact with the patient.

You don't necessarily need to say, clear (as you could choose another word), but you must warn other members of the team that you are about to deliver a shock and that everyone must stand clear of the patient. Though, uniformity isn't a bad thing, and if all are expecting to hear, clear, that might still be the best option.