AED: CPR after Shock, why?

[IvanD]

Hey all,

I have recently become a first aid, cpr/aed instructor with the ARC and this is a question often brought up by students and to be honest I haven't got this one quite figured out yet.

If the AED analyzes the pt's heart rhythm and determine that it's shockable. It shocks. Why do we continue CPR immediately? If it happens that the rhythm is shocked back to a normal sinus rhythm, wouldn't CPR disrupt the electrical impulse?

Also on a side note, I've heard different things about doing CPR on a heart that's pumping efficiently. I've heard that it will disrupt the normal impulses and screw it up and I've heard that it does nothing to the heart.

I appreciate any input, thanks guys.

 

[Handsome Robb]

Because even if the rhythm is converted the heart still wont be beating efficiently as it should be. The CPR helps the cardiac output and has shown no detrimental effects on a heart that has been converted back into a perfusing rhythm.

CPR will do nothing to disrupt an electrical rhythm. What electrical impulses are generated from CPR? None, its a mechanical action.

Even with ALS personnel using a manual defibrillator we continue CPR after a defibrillation with no pulse or rhythm check for 2 minutes.

 

[ArcticKat]

There was a similar discussion regarding this topic a few weeks ago.

http://www.emtlife.com/showthread.php?t=23838

 

[JPINFV]

It also decreases the time without CPR if ROSC hasn't been achieved.

 

[VCEMT]

This is my take on it.

Carburetor is the heart.
Defib is turning the engine back on.
Continuing CPR is giving it gas.

 

[the_negro_puppy]

From what I understand there is myocardial stunning after a counter-shock and you need to get straight back on compressions to give the heart the best chance of being re-perfused and beat effectively.

Compressions shouldn't effects the normal electrical impulses

 

[IvanD]

Got my answer! Thanks guys. Appreciate it!

 

[Akulahawk]

It also decreases the time without CPR if ROSC hasn't been achieved.

This is my take on it. Also, should ROSC occur, continuing CPR (done properly of course) shouldn't disrupt anything. IIRC, it's indicated for symptomatic bradycardias... where the rate is way too slow, but there's still perfusing beats. On top of all that, if you see a good rhythm return and the beats are perfusing, you can always stop...

 

[mycrofft]

Newer tx algorithms call for more and more continuous compressions.

Check your recent CPR class book or take the course.
The former contention that CPR will damage a beating heart has been discarded. The current (no pun intended) thinking is that compressions have to be prompt, fast, deep, and continuous; standing around waiting for the AED to say "Good Job, Bucko" is usually a waste of time because the majority of the time it will not return to a non-shockable rhythm unless it went systolic. The majority of cardiac cases requiring field resuscitation still present and end in death, but CPR and AED are the best shot before the drugs show up.
Notice they don't teach basic CPR people to take pulses anymore? And CPR has replaced supine abdominal thrusts for airway obstructions in the unconscious?

 

[Handsome Robb]

IIRC, it's indicated for symptomatic bradycardias... where the rate is way too slow, but there's still perfusing beats.

I believe that's only for the little whipper snappers but I may be wrong. But either way your correct.

 

[WTEngel]

I am looking through Circulation to find the specific study, I can not seem to find it though, however the outcome was this:

Out of a sampling of patients who received defibrillation during pulseless arrest, the number that converted into a PERFUSING rhythm was 0.

All of the patients were either refractory or converted into PEA, which required CPR for an unspecified duration in order to achieve detectable perfusion.

 

[Markhk]

I usually try to avoid posting material from a specific manufacturer, but this video might be an interesting one for you to as it attempted to explain away the 3-stacked shock model of previous guidelines.

http://www.youtube.com/watch?v=zr4Lc5VYuhA&feature=player_detailpage#t=83s

 

[mycrofft]

WT, by "pulseless", do you mean palpably , audibly, or electrically?

V tac or fib can be silent and impalpable, but I thought sometimes they came back with tx.

 

[samiam]

Because even if the rhythm is converted the heart still wont be beating efficiently as it should be. The CPR helps the cardiac output and has shown no detrimental effects on a heart that has been converted back into a perfusing rhythm.

CPR will do nothing to disrupt an electrical rhythm. What electrical impulses are generated from CPR? None, its a mechanical action.

Even with ALS personnel using a manual defibrillator we continue CPR after a defibrillation with no pulse or rhythm check for 2 minutes.

Side Question.... why does CPR create a waveform on the monitor?

 

[JPINFV]

Artifact.

 

[WTEngel]

The study mentions no "palpable" pulse.

 

[jjesusfreak01]

Side Question.... why does CPR create a waveform on the monitor?

Dangit, I was about to ask this...so I still want an answer???

Does it have anything to do with the fact that you are physically and temporarily changing the anatomy of the thoracic cavity with each compression?

 

[mycrofft]

Compressional artifact

I think that you can create a minuscule (hence detectable) electrophysiologic signal by compressing muscle or nerves.