So now we take an electrosurgical instrument, and this instrument is universal—it’s a monopolar electrosurgical spoon. And we now look at…we have 2 possibilities with this instrument. One possibility is we have a large flat surface, a large surface area. The current density is going to be relatively low. So what do we expect it to do? It’s going to desiccate or coagulate the tissue. We now take the same instrument. We just turn it to the edge. We now have a small surface area. We have a much higher current density. What do you expect it to do? It’s going to vaporize or cut.
So now, let’s take a look and see if that’s actually true. Here we take a monopolar spoon. It vaporizes—we’re using a small surface area—and we take it and we turn it to a larger surface area that’s flat. It’s going to simply coagulate, desiccate the tissue—no cutting whatsoever. Now I’m going to take it and move it to the edge again, simply moderating the density of energy, and we have a very efficient cut. This is the moderation of current density having nothing to do with the generator settings.
Now, what do we need to get a cut? Well, we have to focus the energy. We have to spark. And so, what do we need to create a spark between the electrode and the surface of tissue? We need to create this spark with energy, and the minimum threshold for that is about 200 volts. So now, hopefully, you ask yourself the question, Where is there 200 volts coming out of your generator—the cutting, blend, or coag side? Well, it comes out of every side of the generator.
So we can cut and we can spark, regardless of where we are at the generator. And so we see this video and we know that this is being created by both a blend, cut, and coag current without difficulty whatsoever. So now, hopefully, we can ask the question, Does it matter? Do we care where we are on the side of the generator to create this cut, since it all works that way? And let’s take a look to see if there’s a basis for caring.
So now, for the first time, I’ll bring up the concept to you—What comes out of this box? This is essentially what comes out of the box.
You see on the cutting side of your generator, it’s an unmodulated…called simply uninterrupted, relatively low-voltage sign wave. And we start to blend and go to coag—if you notice, you have interruption of current, and you see a dramatic rise in the voltage. And finally, on the coag side of the generator, you see, in fact, the voltage is quite high and, in fact, the current’s off most of the time. It’s actually sparking.
So, look at where that voltage is. Here’s the lower voltage and there’s the higher voltage. Remember, voltage is risk, voltage is force. So, we know that the coag side of our generator is the least predictable and most thermally destructive part of the generator.
Now, let’s take a look at the cut edges of a piece of tissue. So look at the difference in the thermal margins of these cuts when you compare the cut blade form, the blend wave form, and the coag wave form. And let me help you understand this concept of blend. So, many people think blend means that we blend a little of this and we blend a little bit of that and we get some sort of a mixed wave out of the generator. No. The blend refers to a blended tissue effect. And what happens when you blend 1, blend 2, blend 3, and finally the coag, you’re starting to go from a pure cut to now a cut with more thermal margins. And notice on the coag side, you cut very efficiently, but you have a much wider swath of destruction. And so, if you see that and you think about it, your thermal spread or charring is much higher on the coag side. Your voltage is higher and, of course, the adverse is true on the cut in side of your generator. So we, essentially, as laparoscopic and also laparotomic surgeons, should learn how to live on the cutting, uninterrupted side of our generator, where there’s low voltage for virtually everything we do. And there are selective reasons to say, “I would want to be on the coag side of my generator,” and that’s—remember—bigger voltage, bigger push. If we need a bigger push because we have higher resistance or if we want to get more hemostasis because we’ve got wider thermal margins, we would want to be there. So think about it. Cutting through erectus muscle, cutting through myometrium, cutting through fat, cutting through adhesions—these are all situations where either you want more hemostasis at the edge or you need a bigger push to cut, as in cutting fat or cutting adhesions. So exemplary of this, let’s say you’re doing total laparoscopic hysterectomy. You’re going to incise the vaginal cuff off of the lower cervical tissue. And, of course, we would want to be somewhere on the blend side, if not coag, because we’ve got to hemostase the vessels in the vagina. So this is a perfect example. You would selectively use a certain side of your generator to get a certain desired effect because you expect the thermal margins, in this case, to be more vascular.