LIN Sessions - Precharging the Defibrillator
Michele Lin MD, Sam Ghali MD and Anand Swaminathan MD
Take Home Points
▪ Charge the defibrillator before the rhythm check so you are ready to shock immediately upon recognizing a shockable rhythm.
▪ A main tenet of effective CPR is decreased time to defibrillation.
▪ It takes time to reach adequate coronary perfusion pressure.
● What is precharging the defibrillator? Charging the defibrillator before the rhythm check so you are ready to shock immediately upon recognizing a shockable rhythm.
● As team leader, you will call for the defibrillator to be charged while chest compressions are in progress. You are anticipating that you will find a shockable rhythm and precharging will allow you to deliver the shock without any extra pauses.
● ACLS has essentially been shaved down to basic BLS.
o One of the two main tenets of effective CPR is decreased time to defibrillation. If your defibrillator is charged before you encounter the rhythm and you are able to shock immediately without waiting for charging, you are decreasing time to defibrillation.
o Decreased total hands-off time has received a lot of attention recently. Chest compression fraction is the percentage of time of the resuscitation with chest compressions in progress. Increasing the hands-on time increases the chest compression fraction.
● What usually happens during a code? Chest compressions are in progress. The team leader calls for a pulse check. Compressions stop. Everyone looks at the monitor. If ventricular fibrillation or tachycardia is seen, the team leader calls for charging of the defibrillator. Someone shouts “clear”.
o The problem with this approach is that we are unprepared for what we will see during the rhythm check. We are not ready to take the next step.
● Coronary perfusion pressure (CPP) is not an on/off switch. It takes time to build. If you continue chest compressions while awaiting charging of the defibrillator, you still probably won’t have resumed adequate levels when you are interrupted again to deliver the shock.
● Why haven’t we been doing this? We have been following the guidelines which have not yet adopted this strategy. When you look up and see a shockable rhythm, you can deliver the shock immediately and resume chest compressions.
o What is the downside to adopting this strategy? Some worry that early precharging of the defibrillator could lead to accidental defibrillation of the person doing chest compressions. However, this is unlikely.
● How can you make this happen? Brief your team. The team leader, time keeper and chest compressors have to be on board. Tell the chest compressors beforehand. “We are going to be charging the defibrillator while you are doing compressions. You will hear it go off but don’t worry. It is just charging. We are not going to deliver the shock yet.” Remind them while charging is in progress.
● When do you start recharging the defibrillator? Know how the defibrillator works. It is important to know how long the defibrillator holds a charge. Some devices hold a charge for 60 seconds. Have the timekeeper alert you thirty seconds before the rhythm check. “OK, rhythm check in 30 seconds.” This alerts all team members. Chest compressors can prepare to switch. Ultrasound can be prepared. Charging of the defibrillator can be initiated.
● Data is limited. This is difficult to study. The only human study looked at CPR sensing defibrillator transcripts over a 3 year period. They had a total of 448 cycles of CPR with precharging of the defibrillator. They found significantly decreased hands-off time. However, it is a retrospective study. There may never be robust data available. There were no inappropriate shocks delivered and only one inadvertent shock.
o Edelson, DP et al. Safety and efficacy of defibrillator charging during ongoing chest compressions: a multi-center study. Resuscitation. 2010 Nov;81(11):1521-6. PMID: 20807672
● The Australian and New Zealand Committee of Resuscitation (ANZCOR) has adopted this into their guidelines. “If using a defibrillator in manual mode, the defibrillator should be charged during CPR as the end of the 2 minute loop of CPR approaches, to minimize interruptions to CPR and increase the likelihood of shock success.”
● Hands-on defibrillation. What about doing hands-on defibrillation and shocking while compressions are in progress? This may not be safe. Studies are mixed. Even if safety is not a concern, you are still shocking later than if the defibrillator was precharged. Precharging the defibrillator supersedes hands-on shocking entirely.