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How Not to Fry Defibrillators With Dual-Sequential Shocks

June 21, 2019

Written by Clay Smith

Spoon Feed
Learn how to avoid frying one defibrillator with the other if you use dual-sequential defibrillation (DSD) as well as the most effective pad placement and inter-shock timing.

Why does this matter?
DSD use is becoming more prevalent. However, the evidence for its effectiveness is questionable, and energy from one defibrillator may damage the other, which is not covered under warranty. How can the pads be placed to reduce transfer of energy from one machine to the other? Also, what’s the best timing: simultaneous, slightly delayed, or what?

Thank you, pigs.
This was a two-part trial using pigs. When pads were placed in an orthogonal (perpendicular) arrangement, there was a 50-fold drop in the voltage transferred from one defibrillator to the other. See below. Image B would be a good option in humans. They found that an orthogonal arrangement was also the most successful at terminating v-fib. Regarding the ideal delay between shocks, overlapping (simultaneous) appeared to be best, followed by a 100msec delay. A 50msec delay was actually worse. This may explain the variable anecdotal reports about the efficacy of DSD. A delay of >200msec was no different than just doing stacked shocks from a single defibrillator. Under conditions in which conversion of v-fib occurred just 30% of the time using lateral two-pad placement and a single shock from a single defibrillator, with 4 pads – both lateral and anterior-posterior pad placement (orthogonal or near perpendicular) – and an overlapping (simultaneous) shock delivered from two defibrillators, conversion out of v-fib to a normal rhythm occurred 98.8% of the time (83 of 84 attempts).

In summary, to avoid frying your defibrillator, place the pads as far apart as possible in a perpendicular arrangement, such as image B below. DSD really works if done correctly, at least in pigs, but simultaneous shocks or a <10msec delay is best. This was done in a research setting with precision control on the inter-shock delay, which is not possible in real life with two defibrillators being manually discharged.

From cited article

An investigation of inter-shock timing and electrode placement for double-sequential defibrillation. Resuscitation. 2019 May 4. pii: S0300-9572(19)30158-3. doi: 10.1016/j.resuscitation.2019.04.042. [Epub ahead of print]

Reviewed by Thomas Davis

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