[lapappey]

Was having an interesting discussion the other day and wondered what people think. AED's were criticized for their inability to recognize occult VF, seeing as the only monitor one lead (lead I?) and per ACLS asystole should be recognized in more than one lead before treatment, i.e. before deciding not to shock. Now, anyone who has heard healthcare professionals gripe about medical TV shows knows that we don't shock asystole, blah blah blah. How should this problem be dealt with? If AEDs used a five-leadwire system, then the AED could r/o occult VF masquearding as asystole by checking more than one lead. I guess this would be characterized as being to complicated for laypersons but "green and white are on the right, christmas trees below the knees, chocolate lies close to the heart", or whatever isn't exactly rocket science. Would this be a decent solution? Is there even a significant problem? What do folks think?

[zambezi]

I think making a five lead system with the typical lead placement would be too difficult for someone without training...not because alll laypersons are idiots but because if a lay person is using an AED, chances are the situation is emergent and full of adrenaline with a lot of people not thinking straight...the wires would get tangled, people would be trying to put this color here and that one there and uncle joe would be jumping in to fix this or that...maybe I am being overdramatic but in a critical situation (especially when a family member is involved) people just can't think straight for the most part. I personally would rather have the AED shock anything that might resemble VF, fine or otherwise. My reasoning is (and this is just my opinion!!) is that if it is a fine VF, a shock could bring the person back into a rhythm that perfuses. If it is asystole, the patient is either already dead or needs further advanced intervention/medication. In a field situation with laypersons, I think that shocking is the best option in case of that fine VF...shocking a person in asytole without further intervention isn't going to change the outcome...hopefully someone can do CPR until ACLS people come...

[lapappey]

Ah, but shocking asystole can actually have a negative effect on outcomes. So we can't shock asystole indiscriminately on the basis of "it might be occult VF." I was poking around on the net and apparently about 2.5% of VF's are occult in at least one lead. Not a large percentage. Not an insignificant one either.

Is it the case that the coarseness of fibrilitory waves bears an inverse relationship to the incidence of successful defibrilation? Is there a significant difference b/t occult & obvious VF in terms of outcome (barring treatment of VF as asystole.)

What if AED's had, as they do, two pads, plus a brown electrode that the user is instructed to place over the heart, and then we could monitor one or another of the MCL's? That's not too challenging. Or weren't the two leads asystole is confirmed in supposed to be perpendicular ... that would require RA, LA, and RL (or what have you.)

Now, AED's used by EMT-Basics are a bit more worrisome to me than AED's used by laypeople (this was actually what the discussion I was having was about but I totally didn't put it in my post) ... now, EMT-Basics are not qualified to read strips, but they're certainly not incapable of hooking up five electrodes, and if this caues 2.5% of the population to have a better outcome, why on earth not? Especially since EMT-B's may well be with the pt for a considerable length of time before ALS arrives. Come to think of it, recognizing VF & VT isn't rocket science either. If an unlicensed monitor tech can do it in a tele unit, why on earth can't an EMT-B?

[begalli]

Originally Posted by zambezi

I personally would rather have the AED shock anything that might resemble VF, fine or otherwise. My reasoning is (and this is just my opinion!!) is that if it is a fine VF, a shock could bring the person back into a rhythm that perfuses. If it is asystole, the patient is either already dead or needs further advanced intervention/medication.

I am of the same opinion.

Heck, even I sometimes have to stop and think in my head...white/right; snow/over grass; smoke/over fire.

[zambezi]

Originally Posted by lapappey

Ah, but shocking asystole can actually have a negative effect on outcomes. So we can't shock asystole indiscriminately on the basis of "it might be occult VF." I was poking around on the net and apparently about 2.5% of VF's are occult in at least one lead. Not a large percentage. Not an insignificant one either.

Is it the case that the coarseness of fibrilitory waves bears an inverse relationship to the incidence of successful defibrilation? Is there a significant difference b/t occult & obvious VF in terms of outcome (barring treatment of VF as asystole.)

What if AED's had, as they do, two pads, plus a brown electrode that the user is instructed to place over the heart, and then we could monitor one or another of the MCL's? That's not too challenging. Or weren't the two leads asystole is confirmed in supposed to be perpendicular ... that would require RA, LA, and RL (or what have you.)

Now, AED's used by EMT-Basics are a bit more worrisome to me than AED's used by laypeople (this was actually what the discussion I was having was about but I totally didn't put it in my post) ... now, EMT-Basics are not qualified to read strips, but they're certainly not incapable of hooking up five electrodes, and if this caues 2.5% of the population to have a better outcome, why on earth not? Especially since EMT-B's may well be with the pt for a considerable length of time before ALS arrives. Come to think of it, recognizing VF & VT isn't rocket science either. If an unlicensed monitor tech can do it in a tele unit, why on earth can't an EMT-B?

I agree, that an emt-b vs. a lay person that is related to the coding person may have a better chance of getting lead placement right. I also think that the patches plus the brown electrode would be easy...I think you could even label it without difficulty...I agree that we should do what is best for the population...I don't think that a class on "the shockable rhythms" vs others as an added back up might not be bad (mabye they already have this, I don't know).

I think that having one extra lead easily placed would be a good idea of the AED could automatically switch to a different lead for vericfication of asytole vs fine VF (how much longer would it take to defibrillate if the machine has to switch leads is another question) Its too bad the AED couldn't analyze two leads at once...
I still think in that less than ideal situation, the AED as it stands now works pretty well...it will be interesting to see how it changes as it becomes more widespread (we finally got them in all of our local schools here!!)

As a side note, I didn't mean to infer that anything without a pulse should be indiscriminately defibrillated (as it sounded when I reread my post...)
However, I wonder if defibrillating what might be that fine VF vs asystole out in the field would really change outcomes all that much- only because if you are in that non perfusing rhythm for x amount of time before further help can arrive your chances of survival are minimal anyway...However, I do agree that we can't just shock everything....
I am unsure if the coarseness of the VF waves has any effect on the ease of conversion after defibrillation...I am sure that there have been some studies done somewhere...when I have some spare time I will see if I can find anything...

I am interested to hear what others have to say about this...as I stated in my first post, these are just my opinions and I haven't had time to do additional reseach about it...

[lapappey]

Originally Posted by zambezi

<snip>
I think that having one extra lead easily placed would be a good idea of the AED could automatically switch to a different lead for vericfication of asytole vs fine VF (how much longer would it take to defibrillate if the machine has to switch leads is another question) Its too bad the AED couldn't analyze two leads at once...

There would be no change in time for defibrilation if VF was obvious in Lead II(AED's do monitor lead II, right? I said Lead I earlier and that was definitely wrong now that I think about it). If asystole was detected, then the AED would go ahead and monitor Lead MCL1, or Lead I, or what have you, and if VF was found there, zap; if no VF, "No shock indicated."

(BTW-apparently the two leads monitored need to be perpendicular. So I and III? Hmm. BTW again-what the heck lead is being technically being monitored if anterior-posterior placing of the pads is used?)

Originally Posted by zambezi

I still think in that less than ideal situation, the AED as it stands now works pretty well...it will be interesting to see how it changes as it becomes more widespread (we finally got them in all of our local schools here!!)

Most definitely AED's are a Good Thing and they are at the very least better than nothing. What I'd be interested to see is if there is an easy enough way to give the 2.5% of VFers who are occult in one lead a chance to get shocked by an AED.

Originally Posted by zambezi

<snip>
I am unsure if the coarseness of the VF waves has any effect on the ease of conversion after defibrillation...I am sure that there have been some studies done somewhere...when I have some spare time I will see if I can find anything...

I think coarser VF = more electrical activity = more electrical activity to become organized electrical activity after depolarization. Read this somewhere, but I can't give you chapter and verse on it.

An interesting paper on this is Cummins & Austin (1988) in Annals of Emergency Medicine 17(8). The abstract says:

We investigated the frequency with which a "vector of ventricular fibrillation" may exist in persons in prehospital cardiac arrest. Emergency medical technicians trained in defibrillation were directed to record the rhythm in three different monitor leads whenever they noted an initial flat line. Before these lead switches, the technicians performed a flat line protocol that included inspection of the lead connections to the patient and to the defibrillator, and checks of the calibration and battery status of the devices. They performed this flat line protocol for 127 cardiac arrest patients; 118 were in confirmed asystole after technical problems were corrected. Ventricular fibrillation was detected in only three (2.5%) when the monitor lead was switched. Initial technical problems were more frequent and were identified for ten patients (8%). The frequency of occult ventricular fibrillation (three of 118 asystolic patients) yields a 95% confidence that the true frequency is no greater than 8% to 9%. This suggests that ventricular fibrillation masquerading as asystole is rare. These data do not support protocols for empiric countershocks of patients with an initial flat line on the monitor.

****

I read this as saying that a policy of "shocking everything" is bad (which we agree on), but however that switching leads is important enough.

An interesting web page arguing that ACLS should drop the policy of not shocking asystole is: http://www.defib.net/asyswk.htm.

ACLS '92, quoted above, says:

Rescuers should confirm asystole as the rhythm when faced with a flat line on the monitor by changing to another lead on the lead-select switch or by changing placement of the defibrillation paddles by 90(degrees). Operator errors that lead to "false asystole" are much more common than VF that masquerades as false asystole.

****

With reference to the above article.

What a can of worms I've opened up

[tridil2000]

[quote=lapappey]Ah, but shocking asystole can actually have a negative effect on outcomes. So we can't shock asystole indiscriminately on the basis of "it might be occult VF."

you know, in 18 years i've never seen anyone make it out of icu alive after an episode of asystole. even if a rhythm came back, they never survived the course of hospitilization after that.

sad but true.

[lapappey]

Point taken, point definitely taken--

So should all pulseless patients be shocked in the field? Does ACLS only mandate not shocking asystole because in the hospital we have resources to confirm that asystole is asystole?

I really don't know. Any opinions?

[quote=tridil2000]

Originally Posted by lapappey

Ah, but shocking asystole can actually have a negative effect on outcomes. So we can't shock asystole indiscriminately on the basis of "it might be occult VF."

you know, in 18 years i've never seen anyone make it out of icu alive after an episode of asystole. even if a rhythm came back, they never survived the course of hospitilization after that.

sad but true.