Defibrillation & Synchronized Cardioversion Energy Settings
Remembering all the different energy setting needed for synchronized cardioversion and defibrillation is confusing for a lot of people. A question I’m frequently asked at the ACLS classes I teach is, “how do you remember what energy is needed when cardioverting or defibrillating someone?” The answer to that question is today’s Pass ACLS tip topic.
We can break down energy settings into 3 basic categories based on technology:
- Automated External defibrillator (AED);
- Biphasic defibrillators; and
- Monophasic defibrillators.
Automated External Defibrillator (AED)
Defibrillation: AEDs are designed to be used by first responders, and lay people with only minimal medical training, so the controls are simple and pre-programmed into the machine. When using an AED, the provider only needs to turn it on, attach the pads (preferably while CPR compressions are being performed), and follow the verbal commands. If a shock is indicated, the AED will charge to a pre-programmed amount of electricity without any input from the user.
Cardioversion: AEDs are only used in cardiac arrest situations so only a defib energy setting is programmed into the machine. AEDs should not be used on patients with a pulse.
Biphasic Defibrillators
Defibrillation: Because of the mechanism, biphasic defibrillation lowers the electrical threshold needed to be successful; 200 j for a biphasic shock vs 360 for monophasic. This is a good thing because passing electrical current through tissue, even with the best intentions, causes tissue damage. Most modern biphasic defibrillators have an ability to measure the impedance/resistance between the pads and can adjust the energy up or down to maximize effectiveness. When using a biphasic defibrillator it’s generally advised to use the manufacturer’ s suggested settings, or use the built in settings and let the electronics do the rest. If you don’t know the recommended setting, use 200 j.
Cardioversion: Just like defibrillation, the energy needed for cardioversion when using a biphasic device is less, and is calculated by the machine. Be sure to engage the “Sync” function when cardioverting, then use the manufacturer’ s recommendation. You can tell when the sync is engaged on most monitors because an icon will appear adjacent to each QRS complex. For safety’s sake, remember that, when cardioverting, it can take several seconds for the defibrillator to discharge after pushing the button. The team leader must ensure that nobody touches the patient until after the defibrillator has discharged.
Monophasic Defibrillators
Defibrillation: As mentioned before, monophasic defibrillators generally require a higher energy setting to successfully convert a fibrillating heart than a biphasic defibrillator. The energy setting when using a monophasic defibrillator is 360 j. Monophasic defibrillators don’t calculate the impedance between the pads or paddles so no adjustments to subsequent shocks is needed. For V-Fib or pulseless V-Tach, just set it to 360j and leave it.
Cardioversion: 50j should be used as a starting point for cardioversion of narrow complex SVTs while 100-150j should be used for wide-complex tachycardias such as VTach with a pulse. If the initial synchronized shock at these settings is unsuccessful, the energy should be increased in 50j increments up to a maximum of 360j.
