Energy options in gynecologic surgery

This webcast was supported by Ethicon Women’s Health and Urology.
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Energy options in gynecologic surgery—a topic very dear to me and very often understudied for all of us in our basic training.

And as a signpost of today’s presentation is the review that we’ll partake of fundamental knowledge and technique. And for me, when I take fundamental knowledge and technique and reduce it to its ingredients, it definitely leads to being safer and also contributes to efficacy and efficiency of surgery. And for me, when I combine these 2 elements and I think about really how they contribute to my practice and the outcome of patients, it’s surgical outcome. So today is really dedicated to improving outcome in patients.

Now, in order to hopefully communicate as best as possible with you, I want to review both new concepts and also what I would term electrosurgery vernacular.

In order to do that, I’d like to create a model here and build a water tower. And just think of…in order to get the water into the tower, you have to have some sort of push or force to create that reservoir. In electrosurgical terms, voltage is what provides that push that pushes the current through something called resistance, which is a variable ability for something to pass through a circuit. Obviously, if the resistance goes up, the aperture get smaller. You have to push harder. If you push larger amounts of current, you have to push harder. But these are the 3 elements of electricity, and so we have current, we have resistance, and we have voltage. But…only when we use a battery and a direct current do we really call this resistance. The proper term in electrosurgery for resistance is impedance. So for the rest of this talk, I’ll be using the word impedance instead of resistance to talk about that difficulty by which electrons pass through a circuit. But most importantly, and fundamentally, voltage is force.

When we think about force and voltage, we think about surgery. Whether it’s physical or it’s electrical, greater force is greater risk. So whatever we can do to minimize voltage is going to minimize unpredictable behavior of thermal modalities, and it will maximize our safety in tissue.

Now what is electrosurgery? It’s…taking something hot and burning something with it. When, in fact, what we do is we take alternating current in very small frequencies—60 cycles per second. And it gets plugged into an electrosurgical generator, our boga unit, as we refer to it in slang terms in operating surgery. And that is simply a machine that accelerates the frequency to very high frequency—to up to 3 million, but typically around 500,000 to 700,000 cycles per second versus 60. As that current is transmitted through cells, because they have ions in them and water, this energy is now converted to kinetic energy, because you have alternating current that flows against the resistance. And in overcoming this resistance, you get what’s called resisted heating, or the production of heat. So in fact, as you see, you take something that really has no temperature whatsoever, and we create temperature with it by the nature of passing current through something of variable resistance, called resistive heating.

So the question comes up—What determines whether coagulation or cutting occurs? Does it have to do with the salic generator? No, in fact it has nothing to do with the generator. Think about it. If we take tissue and we heat it up slowly, and we percolate the water out, we coagulate or we desiccate it. If we take the same tissue and we now heat it up very rapidly, we now create steam, and that steam is very explosive—it ruptures the cell membranes and you get vaporization, or what’s called cutting. So what’s the difference between the two? The only difference we see here on this graph is the rate at which we heat up tissue. So, in fact, we completely moderate between cutting and coagulation, based on simply how fast or how slowly we heat up the water in tissue. And how do we do that intuitively?

Well, we all do it as surgeons intuitively because we manipulate energy density. And how do we do that? Well, think of the old model. I think at least all the males here watching this presentation remember taking a magnifying glass and taking sun and heating up different structures with the sunlight. And we know that if it passed our hand through this part of the beam, it’s actually relatively cool. And if we now go to where we have the beam focused, we end up having a much warmer spot. What’s the difference here? It’s just a difference of energy density, and this is what we do. That’s relatively cool and that’s relatively hot.


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