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mgr22

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Technically, 7 joules is 7 joules (a unit of energy, same as watt-seconds), but we've pretty much settled on the notion that less energy delivered with a biphasic device can be as effective as more with a monophasic device. There are variables, though -- e.g., patient size, device, type of biphasic delivery. Also, whenever you see doses rounded to nice, neat numbers like 150 or 200, you can be sure there's some estimating going on. There's no evidence evolution favored the decimal system.
 

Jacm

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Technically, 7 joules is 7 joules (a unit of energy, same as watt-seconds), but we've pretty much settled on the notion that less energy delivered with a biphasic device can be as effective as more with a monophasic device. There are variables, though -- e.g., patient size, device, type of biphasic delivery. Also, whenever you see doses rounded to nice, neat numbers like 150 or 200, you can be sure there's some estimating going on. There's no evidence evolution favored the decimal system.
So the lower settings do not do nothing from 2 joules to 20 joules
 

mgr22

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So the lower settings do not do nothing from 2 joules to 20 joules
Uh, I guess I don't understand the question. Maybe I should have started by asking how you came up with 7 joules. If you're wondering whether low energy settings are ever used, the answer is yes, on peds, for whom electrical therapy is supposed to be weight related.

Is there a specific case you have in mind?
 

Jacm

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Uh, I guess I don't understand the question. Maybe I should have started by asking how you came up with 7 joules. If you're wondering whether low energy settings are ever used, the answer is yes, on peds, for whom electrical therapy is supposed to be weight related.

Is there a specific case you have in mind?
Someone had tolsd me that the lower setting can be used on adults
 

mgr22

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Someone had tolsd me that the lower setting can be used on adults
There are different indications for electrical therapy. In general, for a normal-sized adult with a closed chest, doses for cardioversion would be at least 50j, and for cardiac arrests at least, say, 120j. As I mentioned before, there are several variables.

The closest I could get to your 20j setting would be a 40kg adult who is being treated as a ped because of their size. According to PALS, the first attempt at cardioversion could be as low as .5j/kg = 20j. Please understand that this is all very contrived. Rather than just concede the possibility of a small adult being cardioverted at 20j, I'd rather tell you that what you're suggesting is unlikely.
 

Peak

ED/Prehospital Registered Nurse
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There are only two times I've given a dose that small, one being on infants/toddlers and the other being with internal paddles (although typically we still start with 10 joules in adults).

The problem with small doses is that there is a lot of tissue to cross in adults. We know that the vast majority of adults only need 10-20 joules when defibrillated with internal paddles so we can surmise the remainder of the 150-200 joules that adults get predominantly get blocked/used/resisted by other tissues.

Specifically to monophasic versus biphasic the vast majority of modern external defibrillators are biphasic and studies suggest them to be far more effective. Monophasic defibrillation goes only from one pad to another, biphasic will go from one to the other and back.

Some hospitals still hold on to their monophasic defibrillators because you can defibrillated with two at once and effective end up with a 720 joule shock for very obese patients. Many services still have monophasic defibrillators because they don't want to or can't spend the money on new monitors. There is still a rather large number in CVORs as some surgeons prefer it for internal paddles.

Generally speaking, for external defibrillation, the literature often supports larger doses rather than smaller ones.
 
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