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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.
Pro Tip #1: It's important to note that adenosine does not convert atrial fibrillation, atrial flutter, or ventricular tachycardia.
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 induced tachycardia
- Drug induced tachycardia
- 2nd degree heart blocks
- 3rd degree heart blocks
Adenosine is safe to administer to pregnant patients.
Pro Tip #2: Adenosine is less effective in patients who are taking theophylline or caffeine. And if administered for irregular polymorphic wide complex tachycardia or V-tach, it could cause a deterioration including hypotension.
Adenosine side effects include:
- Transient periods of flushing
- Chest pain
- Chest tightness
- Brief periods of asystole
- Brief periods of bradycardia
- Ventricular ectopy
Pro Tip #3: Reduce the initial dose of adenosine to 3mg in patients who are also receiving dipyridamole or carbamazepine, in heart transplant patients, or if adenosine is given by central venous access.
Remember, transient periods of sinus bradycardia and ventricular ectopy are common after termination of SVT.
Adult Dosage of Adenosine
Adenosine should be delivered via rapid IV push and follow the steps below when administering the drug.
1. First, 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.
2. Rapidly administer the initial bolus of 6 mg over 1 to 3 seconds.
3. Follow the adenosine with a normal saline bolus of 20 ml. A 2nd dose of 12 mg of adenosine can be given after 1 to 2 minutes if needed.
4. While administering the medication, make sure to record the rhythm strip.
Pro Tip #4: Draw up the adenosine dose and saline flush in two separate syringes. Attach both syringes to the IV injection port that's closest to the patient. Clamp the IV tubing above the injection port. Push the IV adenosine as quickly as possible. While maintaining pressure on the adenosine plunger, push the normal saline flush as quickly as possible after the adenosine.
5. Unclamp the IV tubing.
6. Monitor the outcome.
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 rhythm, 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. The patient needs CPR, beginning with chest compressions, for several minutes until sufficient heart function resumes.
Also, not all shocks will lead to successful defibrillation. Which is why it's important to resume high-quality CPR immediately after a shock, beginning with chest compressions.
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:
- Announce the shock – clear!
- Check to make sure you're clear of contact with the patient, the stretcher, or other equipment.
- Make a visual check to make sure that no other member of the team is touching the patient, stretcher, or other equipment.
- Make sure oxygen isn't flowing across the patient's chest.
- Deliver the shock to the patient.
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.
