So, our next speaker will be Dr. Joel Munzer, a professor at Medical University of South Carolina, who will give us our talk on electrocautery. It's my pleasure, again, to have Dr. Munzer here, my mentor and one of the best endoscopists I've ever met. Thank you for the kind words, Jason. I needed that this week. And thank you to Catherine and Jason for this invitation to be here. It's always an honor and a lot of fun to be at the ASGE First-Year Fellows course. The topic of my presentation is electrocautery. So electrocautery, I actually gave this exact talk at this course last year. And as I was preparing for that talk, I realized how little I actually remembered about sort of any basic principles of electrocautery. And as I looked at the slides for this year, I realized how much I had forgotten from last year. And so, it just sort of goes to show that you can be at least a modestly successful academic endoscopist without being in the weeds on electrocautery. I think it's more important to understand the big picture rather than sort of granular level details, because they are sort of big picture pieces I think are being more important. So, what I will say, though, I learned in the process is that electrocautery is a misnomer. What we're actually doing in gastrointestinal endoscopy is we are using a device to deliver electrical current to the tissue to heat the actual tissue. The device itself never gets hot. And the term for that is electrosurgery. Electrocautery is when the device itself gets hot and you transmit the heat to the tissue. And that's very uncommon in gastrointestinal endoscopy. And there are relatively few devices of which I'm aware, the most common of which is what's called a heater probe that uses electrocautery. So the proper term is electrosurgery. Like in many things in life, to stay happy and sane, you have to sweep some stuff under the rug. And so I will use the term electrocautery interchangeably with electrosurgery, but just know that electrocautery is technically not correct. So I have no confidence to disclose. So the fundamental purpose of an electrosurgical generator is to produce high-frequency AC or alternating current for the purpose of heating tissue to achieve some desired tissue effect, otherwise known as diathermy. And since it's AC current, an interesting question that comes up is how are you delivering AC current without actually electrocuting the patient or shocking the patient? And so it turns out that the threshold at which neuromuscular stimulation no longer occurs is about 100,000 hertz, beyond which, so if the frequency is higher than that, that's too fast for apparently neurotransmitters to sense. And so above 100,000 hertz, there's no neurostimulation, and most electrosurgical units work at three times that hertz, so in the sort of 350,000 range. In contrast, household items work at around 60 hertz, and so that's why your toaster oven can shock you, but the electrosurgical generator won't shock, it'll produce heat without an actual electrocution. So the therapeutic basis of electrosurgery is the production of heat at the tissue or cellular level, and heat is produced through, as we discussed, high-frequency alternating current that flows along a circuit which involves a device that you use to deliver that current to the tissue to achieve a desired tissue effect. It passes through the tissue, and it has to return to complete the circuit in order for it to work. And basically, we talk about tissue effects, and there are two main ones, and everything we try to achieve in gastrointestinal endoscopy is one of these two things, and usually some combination thereof. The first is cutting, so the process of transecting tissue. That's achieved at very high voltage, so voltage is the force that pushes current through the tissue. So a lot of force to push that current, so at voltages in excess of 200, you get what's called high current density, so a really high concentration of current at the tissue level, and what that does is it causes cellular water to heat rapidly, and the cells then will boil and burst, and that causes a transection along the cleavage plane, so you're actually cutting. On the other hand, coagulation occurs at lower voltages, so you have lower concentration of current at the tissue level, so lower current density, and in that context, the cells heat more slowly, and so instead of bursting, they sort of shrink, and they dry out, and they coagulate, right? So cutting is for the purpose of transecting tissue, whereas coagulation is for the purpose of clotting off blood vessels or ablating neoplastic tissue and so forth, and this all has to do with the voltage, above 200 is cutting, below 200 is coagulation, so just in terms of putting it in context for thermal effects on human cells, at 104 degrees Fahrenheit, so if you burn yourself in scalding hot water, that's reversible cellular trauma. At 120, you start to observe irreversible cellular trauma. It's not until you get to 158 degrees that there's a coagulation effect, and you have to be in excess of 200 degrees to get a cutting effect, and so when we're doing an EMR of a polyp, for example, our goal is to transect the tissue effectively and efficiently, but at the same time, to clot off the blood vessels so you have a bloodless procedure, right? So you're trying to achieve some combination of both cutting and coagulation, and you'd think the way the generator would do that is during the cutting phase, deliver current in excess of 200, and then during the coagulation phase, deliver current below 200 so you get a coagulation effect, but that's not how actually it does it at all. Coagulation is a separate mode altogether. For when you have a blended current that's blending coagulation and cutting, it actually only uses a high voltage current that is active during the cutting portion, and then it pauses, and when it pauses, that allows the tissue, particularly the tissue that's a little farther away from the transection plane, to cool off a little bit, and those cells don't burst. They sort of desiccate and shrink and coagulate, and so that's how you get a balance of cutting and coagulation along the penumbra. So if you deliver that high voltage current continuously, like in, let's see if I can successfully use this, in a, very challenging, okay, so, I'm up. So if you deliver it continuously at high voltage, you get what's called pure cut, right? And pure cut is as close as you get to using a cold scalpel, right? And so it cuts efficiently and effectively, but it's difficult to control, and you're doing nothing for hemostasis, otherwise you'd use a cold technique. And we do sometimes in EMRs, thanks to Cyrus Piraca and others, cold EMR is now becoming more popular, and that's no hemostasis whatsoever. But generally speaking, you want an element of hemostasis, and pure cut does not achieve that. But again, in order to achieve cutting and coagulation, there's a high voltage current during the cutting phase, and then it stops. It pauses for some amount of time, allowing the tissue that's slightly farther away from the cutting plane to cool off and coagulate. And that's how you get the balance. And so that sort of fraction of time on, so cutting time, and time off, is the blend, right? So, and that's known as the duty cycle, that sort of fraction. And so, stated otherwise, again, at less than 200 volts, you're getting pure coagulation, right? So you want to do that, let's say you're treating a vessel using a BICAP probe or something along those lines, using a soft coagulation grasper, or using some technology to ablate tissue. So it's less than 200, you get pure coagulation, there's destruction of tissue, but there's no cutting action whatsoever. Once you get above 200 volts, then you have cutting, and if it runs continuously, then you have pure cut. Again, very efficient at transecting tissue, effective at transecting tissue, but a little bit difficult to control from a technical point of view, and you have no, you're not addressing the blood vessels at all. But if you deliver the current for some amount of time, pause the current, let the tissue coagulate, and then deliver the current again, then you have a blended current. And so, if your time on is 50% of that cycle, then that's called a 50% duty cycle. But there are commercially available settings that provide 6% duty cycle, so time on for 6, and a lot of coagulation. And there's different reasons to use these, a lot of it's dealer's choice, but basically that balance is how you achieve what you intend at the tissue level. So this is what I typically use for endoscopic mucosal resection. It's a current called endocutQ at effect 3, cut duration 1, cut interval 3. This is much more important than the basic principles of electrocautery, in the sense that I know this current extremely well. And that's the most important thing you should get out of this talk, is during your fellowship, you should do your best to understand different currents and to have a good working knowledge of the effect of a certain current on tissue. Because if you know that well, as you gain experience, and by the way, this is not sort of passive. I mean, I learned it passively, but one thing I wish had been reinforced to me early on is that this is active. Every time you're in a case, different attendants are going to use different currents, but observe, see what happens, figure out from them how long does it take to transect typically with this current. Because that knowledge is critically important, because when things aren't going exactly as you expect, you want to have that sort of red flag, that sort of concerned feeling that will allow you to abort the process and address the problem before you've persisted and created a perforation or something along those lines. So there is absolutely no evidence to support this endocut313. The only reason I use it is because that's what Cyrus Paraka uses over there, and when, you know, he taught me how to do EMR, this is what he used, and I liked it. But now it's hard for me to change because I have so many years of experience using it that when things aren't going quite right, I immediately have a clear sense. So for example, I know how long I need to step on the pedal to transect most pieces of tissue that are grasped in a snare. Now occasionally it takes longer, and that could be because I've gotten a little bit too greedy, I've grabbed too much tissue, that's okay. It could be because there's a bunch of submucosal fat, and we know that fat is an insulator, it doesn't conduct electricity very well. But it also could be that I've captured the muscularis propria. And if I persist and transect, then I might put a hole in the esophagus. Sometimes that's okay because we're prepared to deal with that, but in most cases it's not worth it. Take a step back, release the tissue, go back to the drawing board, figure out what's not quite right, and I think that's the best way to sort of ensure safety during the procedure. And testament to the concept that there is no best electrosurgical current is a randomized control trial in which we participated that was published a couple years ago in Gastroenterology, which compared endocutQ to a more standard forced coagulation current. So we all believed at the time that endocutQ was going to be the best current, right? Because of all the quote-unquote smart currents, these are microprocessor-controlled currents. So in other words, the electrosurgical unit is sensing resistance at the tissue level, and it's readjusting its output in real time according to what it senses. And endocutQ is supposed to be the panacea, right? It's supposed to be the safest, achieve the best cutting action, and just enough coagulation to make sure that you don't leave residual neoplasm, et cetera, et cetera, et cetera. And it turns out in this rigorous randomized control trial that there was no difference in severe adverse events and no difference in polyp recurrence at the first surveillance colonoscopy, which again sort of reinforces the concept that there's no best current. There's only a best current for each one of us. Now sure, there's certain things you can't do with certain currents, and of course you'll learn that along the way. But for the bread and butter, the most important thing you'll get out of, hopefully you'll get out of today's lecture, is that you need to know the currents with which you're comfortable. So if something isn't quite right, that alerts you to the problem, and you have an opportunity to fix things before you've taken it too far. So another important concept that relates to this is that of resistance, which means impedance. And so what this is is an obstacle to the flow of current through tissue. So tissues that have greater resistance or greater impedance have less current flow. So they're more difficult to transect or cut, right? And there are some tissues that are known as conductors, like the GI mucosa, for example. So it should be relatively straightforward to transect GI mucosa. Whereas on the other hand, tissue obviously like bone that you're never going to cut through. Or fat, for example. Anybody who has so far had the opportunity to transect a lipoma, for example, it takes forever. It's super uncomfortable, because you're stepping on that pedal forever. And it's because fat is an insulator. But importantly, the clinical implication here is that muscle is more of an insulator than GI mucosa. So if you're doing an EMR, you should be able to transect through the mucosa quickly. But if it's taking too long, of course, there's a whole differential for that. Again, it could be that you grab too much tissue. It could be that there's some mucosal fat. For those of you who will do band-assisted EMR, you're transecting right adjacent to a band. And sometimes you capture the band, by mistake, and the band is plastic, which is an insulator. All those are possible. But the other possibility is that you've captured muscularis propria. And you have to account for that possibility, because if you persist and you have captured mucosa, then you're going to at least cause a muscle injury, if not a full-on perforation. So that's one implication of the resistance concept. The other implication is quite helpful, actually, from a hemostasis point of view, when you're using something like a gold probe or a bi-cap to treat a bleeding vessel. What happens is you deliver that less than 200-volt coagulation current, and you're treating the vessel. The tissue around that coagulates and dies. And coagulated dead tissue actually has really high resistance. So it prevents the current from sort of dissipating and diffusing broadly. And it prevents the current, ideally, from making it down into the muscularis propria. And this is actually a helpful concept clinically, because the way you're supposed to treat vessels with a bi-cap is you're supposed to push hard, and you're supposed to do that for an extended period of time, like 10 seconds of continuous burn. And in the EMR world, when you're using endocut, you're basically asking for a perforation. But in this context, because of this resistance phenomenon, the impedance is going up. And so in principle, the current should not dissipate far enough to cause injury to the muscle wall or extra-illuminally. And that's because of resistance developing as coagulation occurs. So it's an important consideration. So every year, I look at this slide, and I'm not 100% sure what the ASGE training committee intended for this. But I guess if you are a neighborhood hoodlum, and you want to assassinate insects, then you can use a magnifying glass to intensify the energy of the sun. And so I guess this speaks to the concept of current density. And current density is the concentration of current at the tissue level. Higher current density means easier, more straightforward transection. And the reciprocal is true. But current density is the interface between the technology, the electrosurgical unit, and the technical skill. Because what you do with the device is exactly how much current density you'll achieve. So for example, when you're grabbing a polyp, you need to have tight contact with that polyp to maximize current density, because you want a limited amount of surface area connecting the polyp to the device. Same thing for biliary sphincterotomy. If we're doing a sphincterotomy, and you have a cutting wire that's up against all this mucosa, then you've maximized your surface area, and you reduce current density. And what you end up doing is achieving a lot of scarring without a lot of transection. Whereas if you readjust, if you tighten the cutting wire, and you have a limited amount of contact, small surface area, then you've increased current density, and you improve your ability to transect tissue. Similarly with polypectomy, you want to have it tight to sort of optimize that surface area and current density. But if you squeeze too tight, for example, then the snare itself will become involuted so far in the tissue that you actually paradoxically increase the surface area of contact, and you reduce current density, and actually paradoxically becomes more challenging to transect the tissue. And so in terms of basic principles for EMR, in particular for snare closure and transection, one of the principles I always use is that I always try to close the snare tight enough, but not too tight. And one way you can sort of achieve that is that most commercially available snares have markings, have measurement markings between the index finger and the thumb, and this gives you a sense of how tightly you're closing the snare. And so generally speaking, for most EMR cases, what I will do is ask the assistant to close the snare down to 10 or 15 millimeters for two reasons. Number one is, in principle, that's the closure, that's the tightness that maximizes current density, but also, secondarily, and this is not evidence-based, but there is a belief that if you close that tight, if you happen to capture some muscularis propria, then because of that tight closure, you're likely to extrude it from the snare. So you might push it out of the snare, especially if you close, open, and then close back again. But 10 to 15 is basically our standard for transecting tissue. The other important principle that doesn't have much to do with electrocautery, but whenever you've closed the snare and you're about ready to transect, it's important to deflect the scope up and down or move the snare tip back and forth to establish at least to some extent that you have independent movement of the target tissue from the wall of the GI tract, because if they're moving in unison, there's a possibility that you've captured the muscularis propria, and that's a situation in which you might want to let go and sort of reassess. And the other principle that, again, speaks to impedance is short transection time. It takes a long time to cut through muscle, much longer than it takes to cut through mucosa. So again, if you're having a hard time, it could be for one of many different reasons, including the fact that you captured muscle. So I know with that endocut cue setting that in about three to four duty cycles, I should be through, even pretty generous pieces. But if it's dragging, then that's sort of an alarm bell going off, and I'll take a step back. Now, of course, there are situations, especially in this era of therapeutic endoscopy, where the intent, or at least where we accept the possibility of a full thickness resection because we're prepared to close it, but that should be a very esoteric situation. Generally speaking, particularly as you're starting, you don't want to just lay on the pedal, except if you're doing BICAP because it's coagulation. So I think it's important to recognize that electrical current must travel in a complete circuit that originates in the electrosurgical generator to the tissue through the device, leaving the tissue effect, but it has to make its way back, otherwise it won't work. It'll short, right? And so you have to have that complete circuit, and the implication is that there's two different ways of completing the circuit. One is through devices that are known as bipolar devices, which means that the device itself carries a delivery electrode as well as a return electrode, right in the device, right? And so the circuit is right at the target tissue. There's no current that flows through the body. So the effect is only on the contact tissue, and this is typically because of the science behind this that I don't fully understand. This is typically related to low voltage, low maximal power settings, so typically for coagulation, usually for hemostasis. This is what we do for esophageal RFA. Those are typically the bipolar devices, but you don't need a grounding pad because the circuit is in the device itself. And that's in contrast to monopolar coagulation, which is much more commonly used for polypectomy, sphincterotomy, APC, et cetera, and the grounding pad is necessary to complete the circuit. And the implication here is that the current goes elsewhere in the body, and that's important to recognize because there's a potential of injuring the GI tract itself, but of course that current is in many other places and could have potential implications particularly in the skin, right? And so it's important to sort of recognize the importance of the grounding pad. And so four rules for grounding pad safety include that the area should be clean and dry. And I have to confess, like the number of times in a week that I like think about the grounding pad is probably zero, but that speaks to the importance of a good culture around this, good nursing staff, good institutional policies, and so forth. But every once in a while, you're stepping on the pedal, and you know your current well, and you're like, this is not what's supposed to be happening. I'm uncomfortable with what's happening. And one of the things on your differential should be the grounding pad. So the area should be clean and dry. There should be good musculature and vascularity. Avoid bony prominences, prosthetics, scars. And it should be relatively close to the electrosurgical site so that your current's not traveling a huge distance, and there's no risk of dissipating the current, et cetera. Air can, hair can be problematic because if there's not great contact, that might increase the resistance and build up current density and in principle could be flammable. It's like, you know, I forever thought that, you know, smokers who are on oxygen, like I thought it was an old wives' tale that they could light themselves on fire until I actually saw a patient who did that, you know. And so I guess it's a similar situation, so you have to be cautious. But you know, typically in our unit, at least, we don't shave patients for this purpose. But I guess it's a consideration that hair could be a problem. Again, it needs to be well vascularized, shortest circuit possible, ideally on the flank, thigh if necessary. And then avoid tenting. The same type of situation, when it's tented, you can build current density and in principle end up burning the patient because the device, you know. So if the contact is very poor, it has guardrails, it has safeguards it's going to shut off. But if you're right on that sort of interface where it's not quite there and the machine doesn't sense that there's a problem, it'll, you know, it'll increase the voltage and you potentially end up with a burn. And the other implication of monopolar current is that it runs through the body and there's a possibility that it could impact patients with ICDs and pacemakers, right, naturally. Now, the likelihood of this happening is actually pretty low, but it can meaningfully have an impact in certain patients and these, you know, these guidelines are from a decade ago and this changes rapidly. The importance is to recognize that when this monopolar current, you have to know whether or not the patient has an ICD and a pacemaker and almost all units have institutional policies around this. A lot of times anesthesiologists are involved in the care of the patient and so it's just important to recognize that if you're going to do monopolar coagulation, you have to account for this phenomenon. So I'll spend the last couple of minutes here discussing APC, which is a unique form of electrosurgery. The way APC works is that argon gas flows through the system and then through a spark of electricity is ionized to deliver monopolar current to the tissue. It's a non-contact technology, so ideally you want to have separation between the tip of your APC probe and the GI tract wall. And if you don't, you can sort of, the gas comes out pretty forcefully. So if you don't, not only could the gas dissect in the submucosal layer of the GI tract wall, but occasionally you can get extraluminal gas. In fairness, most of the time that's not clinically significant. However, if a patient after one of these procedures comes back with abdominal pain for many reasons and you have a bunch of extraluminal gas, then you've invoked the possibility of a perforation, et cetera, et cetera. And so it's better not to complicate matters, plus it's much more effective, you know, if there's been, if there is some separation. The one unique thing about APC is that the current seeks the best area of conductivity. So you can fire straight ahead, you can fire sideways, and sometimes you can even use it to your advantage and you can treat like around a fold or around a stricture or something along those lines. If done well, it achieves even uniform coagulation. There's a shallow depth of coagulation and a thin eschar. And this is important in the sense that post-polypectomy, post-EMR, post-cautery bleeding typically occurs because an eschar forms. And that eschar typically falls off two to 15 days later. And delayed hemorrhage occurs at the time of that eschar, at the time the eschar sloughs off. And so with APC in principle, it's a thinner eschar, less depth, less involvement of sort of slightly larger submucosal arteries and arterioles and so forth. So in principle, less risk of delayed hemorrhage. This is an example of masterful skill in ablating what appears to be completely normal gastric mucosa. But it definitely shows you how when done well, it can be very effective and uniform and so forth. So we use APC all the time. We use them for angio-display AVMs, gave radiation proctopathy. It can be an adjunct for treating GI neoplasia, including polyp resection, certain types of malignancies in principle. In our practice, we use it probably more often than anything else to help close gastrointestinal fischli. Fischli are epithelialized. And epithelium will never heal to other epithelium. That's why your tongue doesn't heal to your cheeks. So you can close a fischli until you're blue in the face, but you're not going to achieve durable closure of epithelium to epithelium. And so you have to disrupt that epithelium. And typically, we do that with APC. We also do a lot of transoral outlet reductions for patients with Roux-en-Y gastric bypass who have weight regain because their gastrointestinal anastomosis is enlarged. And so you APC the daylights out of that and use that to try to create an inflammatory fibroinflammatory reaction that will scar it down and so forth. And in principle, you could use it for acute bleeding as long as it's an AVM superficial type lesion. So then in conclusion, since now I have gotten that, can somebody put that reserve thing over my flashing light? Anyway, in conclusion, I think the most important thing is understand the equipment. Understand the current effect on tissue. Get to the point where you're very comfortable. So if something isn't right, that'll alert you to think twice about what's happening. And also, it is important to know how to set up the equipment because if you don't, at least to some extent, eventually you'll get in a bad situation where you'll need it in real time and nobody can help you. And in principle, you should know this better than anyone in the room, although that does not apply to me on a regular basis, but at least I know how to set it up. So with that, I will conclude and thank you for your attention. And similarly, a plug for a four. I know this is exhilarating stuff. How long are three duty cycles? Is there like a sound that the machine makes or do you count how many seconds? Yeah. So, well, you know, so there's a bunch of electrosurgical generators available on the market. The one that we happen to use, the pulse is the cutting part and then the pause is the second part of the duty cycle. So every pulse is a new duty cycle. And so, you know, like I said, when I'm doing standard EMR typically and I step on the pedal, I know if by that fourth pulse not transected, there's something not right. Again, there's extenuating circumstances and sometimes it's the best decision to persist. But generally speaking, three to four pulses and, you know, usually when I give talks without getting into the weeds on electrocautery, it's usually two to three seconds is about that time. Is there a resource we can use like in later down the fellowship and in practice which so that we understand these, because equipments will be coming in every time, new equipments keep coming in. Yeah. So, you know, so I've minimized to some extent sort of the importance of electrosurgery, but like there's a whole world around, for example, the people who do a lot of ESD, right? There's a huge science around like, you know, what electrosurgical current to use for, you know, in this organ with this type of fibrosis. So there's actually a ton of resources, but it's very scattered. I will say this, and I've never actually plugged this before, but part of what I did to prepare for this talk is that I co-edit a textbook for gastrointestinal, called Clinical Gastrointestinal Endoscopy. And the electrosurgery section in that book is actually really, really awesome. And so that's how I, you know, sort of reminded myself of all these principles. And there's a great table in that chapter, and I'd be happy to share it. There's a great table that actually puts everything in context according to manufacturer. So what, you know, what a 4% duty cycle is for this manufacturer, what that's called, and so on and so forth. So to my knowledge, and you know, the faculty, correct me if I'm wrong, that's been by far the most helpful resource of which I am aware. Yeah, there's a, that is an incredible resource. I think once you learn it, right, and you've started to understand it a little better, you actually can have whatever your company electrosurgical unit is, just visit your fellowship endoscopy center. So if you say, listen, you know, I use this company, please come, we'll have a bunch of first, second, and third year fellows, teach me how to use your machine, surprisingly they'll come and teach you how to use their machine. Because they hope one day when you go into practice, you'll buy their machine. Yeah, I was going to say, it's not surprising at all, it's brilliant. I was trying to be nice, right? Yeah, yeah. But I mean, but legitimately, right, that's the best person to know, they're going to know things on a lot lower basis. So I would encourage you before they come to actually have some learning basis that you have some information before, otherwise they're going to say things and you're going to be like, oh, yeah, and not know anything about it. But it's actually very helpful. Yeah, that's actually a really good point. So I would recommend it. We actually, you know, when I did it with the places I've been, fellows have been very happy. Yeah, I was going to say the same thing, like whatever your company is, not only can the reps help you out in person, they can also give you documentation on the details of the machine that you're using also, like, we use Irby machines where I'm at, and they, there's a very detailed documentation about all the ins and outs of the settings of that machine. So your reps there can help you out with getting some additional reading materials also. Thank you.

electrocautery

electrosurgery

gastrointestinal endoscopy

cutting

coagulation

patient safety