In our ICU provision of  Advanced Life Support(ALS ) is taken very seriously and many study days spent training staff and performing simulated arrest situations as part of our yearly accreditation program. It is also something we are called upon to practice for real all too often.

From our Department we provide a rapid response service to wards where they will have started Basic Life Support(CPR) and attached an AED and begun to follow the prompts. Once we arrive on the scene or in the ICU itself this scenario you describe will play out in accordance with the most recent ALS guidelines.  

Yes while assessing the heart rhythm in the brief window of hands off we are to prep / charge the defibrillator and either deliver a shock or dump the charge as required. As a trained team with intimate knowledge of the defibrillator function I would say this is quite safe. In the hands of a less experienced team in a time of great stress. Possibly not. and so It is not standard procedure for non ALS trained personnel here. 

 Have I ever shocked the training mannequin rather than dumping the charge in the controlled drama of a training scenario..... Perhaps....

Good question.

Perhaps this is the reason that the native algorithm of the AED will favor not shocking over shocking a monitored rhythm in automatic mode.

The North American ACLS argues that course VF is statistically more likely to cardiovert than fine VF and further that fine VF is sometimes mistaken for asystole. Hence the ARC recommendation to magnify the screen size ,though with only an AED on hand that is not possible, It is important to differentiate between the two as treatment is not the same as you know. The ACLS advises that it if it is not possible to differentiate ,then it is acceptable to deliver a shock. "If it is fine VF you may terminate the rhythm. However if the rhythm is asystole defibrillation will be ineffective and you can continue to follow the asystole protocol with confidence". This seems reasonable as little time is lost and potential harm is minimized 

Good CPR and identification and treatment of underlying causes like the food bolus in the trachea we saw recently , the four H's and four T's,  will go a long way to a successful outcome. Rhythm identification and response in the ALS scenario may involve quite some clinical judgment and will depend on the actual situation and circumstances of the patient as they seldom conform to those scenarios in the training room. Being able to access the best information on which to base those decisions involves good teamwork and access to resources including a clear cardiac display and CPR ,airway security as well as  iv access, quick blood chemistry and blood gas analysis.

Philips report that the ,'Philips Heart Start Automated External Defibrillator 'is good for 300 shocks, before it has to be replaced.  I think that our ward AEDs can give 60 shocks without discharging the battery which itself should be good for 250.

Adequate for a few rounds of CPR.

Hope this is useful.

David.

In state of the art defibrillators, battery consumption should not be a concern so long as manufacturer's guidelines and maintenance recommendations are adhered to.  There is no question in my mind that charge-up can and should be accomplished while compressions are ongoing. As soon as the audible "ready" alert is heard, the team leader should order all hands off the patient for a rhythm assessment. A shock should then be promptly delivered if indicated.  Compressions should commence immediately thereafter.  There should be no pause for a pulse or rhythm check. Same deal if a shock is not indicated, i.e. begin compressions immediately while the charge is being dumped.  Reassessment occurs after two minutes or when signs of life appear.  If the whole team trains that way, this approach works like a well oiled machine. The risk of accidental shock is overblown, in my opinion.

NOTE: The above comment refers to ACLS trained clinicians, not the lay public with an AED.     

Interesting debate so far! From a UK perspective, I would suggest that the issue here is very much one of non-technical skills, rather than the physics of defibrillators. What has been described requires the attending team to have a met up before going on duty and introduced each other, identified their competencies and appointed a team leader. At an arrest, there needs to be situational awareness by all members,  team work, leadership, decision making and task management. Add in good communication between and amongst the team and issues like the one you have raised are safe and effective. Unfortunately, most healthcare professionals have had little teaching of non-technical skills. For these reasons, in the UK, the ALS course now places a much greater emphasis on non-technical skills and they form part of both the cardiac arrest teaching and assessment sessions. The feedback from candidates has identified this change as having been very important and useful. We believe this is the way forward and we hope it will be reflected in our outcomes.

I find it that doing CPR while it charges removes the need for worrying with the physics of battery life, risk for shocking a team member/patient who doesn't need a shock.

From a New Zealand perspective The NZ Resuscitation Council (NZ version of AHA and ERC) advocates and teaches charging with CPR continuing to reduce time with hands off the chest.  The evidence is clear that good CPR with minimal shock pauses results in increases survival.

Both ambulance providers teach and charge prior to rhythm checks.   The survival rate for OH CA was 16% for St John and 18% for Wellington Free Ambulance (WFA); WFA has recorded sick pauses down to 10 sec or less in some cases 3 sec!  This survival isn't Seattle 60% but composers to London and some Australian states 10%.

https://www.google.co.nz/url?sa=t&source=web&rct=j&url=http://www.stjohn.org.nz/News--Info/Our-Performance/Cardiac-Arrest-Annual-Report/&ved=0CCEQFjABahUKEwj1oqq7gb_IAhXJG5QKHew3C4k&usg=AFQjCNEWcXN9x-fs3F2tYKE9N_GOOv3MoA&sig2=E3xgLRCTvDJJk_IKIbCUyw

Good CPR and short preshock pauses leads to better ROSC and long term survival. 

Charging and focusing on good basic resus is the easiest way to improve OH CA outcomes.   Although there is limited research I'd also recommend the use of manual defibrillators to allows charging while CPR continues.   Andrew Swain did a small study and found AED shock pauses of upto 45 seconds.

https://www.google.co.nz/url?sa=t&source=web&rct=j&url=http://www.stjohn.org.nz/global/documents/out-of-hospital%2520cardiac%2520arrest%2520annual%2520report%25202013-2014.pdf&q=stJohn%20cardiacarrest&ved=0CB8QFjAAahUKEwj1oqq7gb_IAhXJG5QKHew3C4k&usg=AFQjCNEQVgDl25mCtDMqo1mZMHatFs9IVA&sig2=KH001Y6bVOa4YhnwWxleBgI hope this helps

I may have double up some links. But better more than less

https://www.google.co.nz/url?sa=t&source=web&rct=j&url=http://www.stjohn.org.nz/global/documents/out-of-hospital%2520cardiac%2520arrest%2520annual%2520report%25202013-2014.pdf&q=stJohn%20cardiacarrest&ved=0CB8QFjAAahUKEwj1oqq7gb_IAhXJG5QKHew3C4k&usg=AFQjCNEQVgDl25mCtDMqo1mZMHatFs9IVA&sig2=KH001Y6bVOa4YhnwWxleBg

Short answer - prehospital NO, in hospital YES, with a good team. It also depends if you are using sticky-pads or paddles - as the paddles are always off the patient the "dump" seems intuitively safer.

Usually small team doing resus, often very junior assistants or lay-public. If all-ALS team maybe

In trained responders charge while cpr continues.... then dump if not needed. The rationale is ANY interuption to cpr takes significant time to regenerate aortic root pressure. Our national guidelines reflect this.

Agree with Timothy above... 

If you wil use adhesive pads for defibrilation the problem will be resolved, because you can charge the DEF. and continue CPR to. You will interupt CPR only whwn deliver shock, and that is the guideline directive.

Hi Pieter,

It's an interesting question you asked one that I had to read twice to make sure I understood.

First Aiders, as in the general public, work place OHS officers, or the person that just so happened to grab the Defib at the Bendigo bank or shopping centre, your question doesn't really have relevance. Purely because AED's the units that the public have access to are ready to use and the really cool thing about most of them, yes have a far few shocks in them, as someone already said, but the sticky pad plugs generally can be swapped from one AED to the other so that if the battery was to go you can simply plug in the next AED. But if that was me I would be praying the Ambo's are not far away.

As a first aid instructor also I basically professionally bash into my students minds that CPR is more important then using a AED. And that if both are done together the persons chance of survival (we use the chain of survival as a term) is so much better.

But if I had to make the call use the Defib or use CPR.. CPR every time.

I'm sure you have an abundance of answers now. Has your view changed? Become more educated? More curious?

Completely agree with Ben Piper. It is all about minimizing the interruptions to the CPR.