So, the next talk is going to be on electrocautery, and it's going to be by Dr. Neil Sharma. He's going to tell us what you need to know about the electrosurgical unit, the different aspects, modalities, and how, as a fellow, you can learn more about it. So, thank you so much. All right. Thank you to the course directors, Dr. Wah, thanks for the introduction, and ASGE. This is one of my favorite courses. I love seeing all the bright new faces into our field, and you guys are the future of our field. And hopefully, this is going to be helpful for you as you move forward in a really bright career. So, post-lunch, you guys are probably a little sleepy. I'm going to give you a lecture that may or may not put you to sleep, but it shouldn't. It should be the most exciting lecture. I'm the most excited about it for this event. Let's see how I ... this one. All right. So, starting off with a little Star Wars picture. So, electrocautery, this is really potentially the most dangerous tool we use in endoscopy. For myself, I'm an interventional endoscopist, and I think I've come to appreciate electrocautery significantly more in my journey through therapeutic endoscopy. But even if you never go into the realm of therapeutic endoscopy, each and every one of you will be utilizing electrocautery in some capacity, whether it's controlling bleeding or removing a polyp or resecting some other lesion. It is integral to what we do in the realm of endoscopy, and so it's important for us to kind of put it up front. Disclosures. Really, no relevant disclosures to this talk, though. I am a consultant for Medtronic, Boston Scientific, as well as Steris and Olympus. So, electrosurgical generators, what do they do? So, you have this generator, and there can be a variety of different generators. I think for the purpose of this talk, they're predominantly highlighting an Erbe generator, which is a power dose generator. But in your units, you may have an Olympus generator, a ConMed generator, or if you have an older lab, maybe even a StarMed generator. But they're all doing the same thing. They're basically producing a high-frequency alternating current, which means the current goes up and down. And when you think about the entirety of this talk, I want you to picture this waveform. So, the waveform has an amplitude or a height to it, which is the intensity, sometimes measured by voltage. It has a distance between the waves, which is the amount of time which is delivering this wave up and down. And then, sometimes it can be off, and when it's off, then that thermal energy is sitting there for a period of time. And I'll walk you through the course of the lecture as to what that means. What does this waveform do, and how can you manipulate it so that it can create the kind of effect that you want on the end target? Okay? So, why is the patient not electrocuted during electrosurgery? And really, this talk should be called electrosurgery, not electrocautery, because cautery and cut are different aspects of electrosurgery. But if you take a look at the hertz to megahertz that we work in, you can see how it is relevant to household items, all the way over to AM radio, to TV, and so on. And we're working within a particular frequency. But what's most important about this? So, what is it that we're trying to do, the therapeutic basis of what we're doing with electrosurgery? What we're trying to do is, we're trying to heat up cells, and we can heat them up in different ways, and the cells can vary. They can be blood cells, they could be tissue of different density. So, for example, the tissue of a gallbladder wall versus the tissue of a stomach versus the tissue of the cecum. They're all different in terms of their properties, and they're all different in terms of their thickness and resistance to taking that current that I just talked about that goes through that. And what we're doing is, we're heating them up. And if you heat them up slowly, like a slow cook, where the amplitude of that wave is not very high, and the wave does not come and go very fast, you're essentially doing a slow and low, and that causes a cooking, or coagulation, as you'll think of, where it's kind of freezing over the tissues, or maybe stopping bleeding in that scenario. If you heat up tissue very rapidly, and you do it with intensity, and you get over 100 Celsius, and that's really the numbers that you think about. Coagulation is usually between 60 to 90 degrees Celsius. But if you want to create cut, which is really vaporization or quick apoptosis of those cells, you're going to heat up that tissue very rapidly, and you're going to go over 100 degrees Celsius. And so that's what we're talking about. We're taking thermal energy, and depending on the waveform itself, and how quickly you cycle energy through that target, that creates the effect that you want, either vaporization in the form of a cut, or coagulation, or a combination if you blend that current in different ways. And that's what I want you to take away from this lecture, and understand that that's what we're trying to do. There's a lot of different ways you can manipulate that current, and we'll talk about that as we go through this talk. So how is heat produced? It's high-frequency alternating current. It goes through a circuit that involves some device that you're utilizing to coagulate or cut. And then it goes through that tissue, and then goes back to the generator. So I mentioned this just previously, cutting, you have a higher voltage. You have a very high current density, so it's zipping through that tissue. You create a waveform that goes very fast up, and then comes down. And what it's doing is, it's causing vaporization, or boiling, or bursting of that tissue, because you very rapidly heat it up to over 100 degrees Celsius. And that causes a cut, or a transection of that tissue. Coagulation, that waveform does not have that high of an amplitude, kind of moves more smoothly. Perhaps the waves are a little bit further apart, or perhaps they're off for a period of time. When they're off for a period of time, that heat has time to kind of set in, and that causes coagulation, which is different than cutting. And as it heats more slowly, the cells kind of shrink down, and instead of vaporizing, they're kind of shrinking and causing this coagulant effect. And effect is really how we look at coagulation. So when you put a coagulant thermal energy onto something, you see this kind of char around it. That's one of the ways that you can visually try to understand coagulant effect. So thermal effects on cells. So here you can see where there's trauma, and I kind of gave you where you really want to think about degrees in Celsius, but this is actually written in Fahrenheit, but it's the same concept. Coagulation is not quite as hot as cutting, as you can see. And again, the rapidity in which we elevate the temperature of those cells is so important. And you'll see that in a variety of different mechanisms. So when I talked about waveforms, and I always picture this, especially when I teach our advanced fellows, I spend a lot of time on waveforms and trying to get them to picture what it is that's happening when you're running the energy through a particular end target. So what is a duty cycle? A duty cycle is the time, it's actually the time in which a pulse wave goes over something divided by time. That's actually literally how you calculate a duty cycle. And a duty cycle is one cycle. So one period of time where you've delivered energy through some sort of end organ and the stop time. And then you take that total time, you divide it into the pulse. So a duty cycle is very, very low on coagulation. Why? Because I told you, I want to keep that current down, the amount of energy going through there slow, and give it a little bit of time for it to create a coagulant effect. Versus in a pure cut, which is all the way on the right, that's something you'd use like on a sphincterotomy, where you're just trying to cut a muscle. You want just pure cut. You really don't want any time between there for the coagulant to set in place. And sometimes the intensity of the amplitude is up as well. That's not shown as much in this picture. And then you can always create a blend, so you get some coagulant and some cut. And that's all we're doing. So it seems very complex, but how you manipulate the amount of amplitude of that current, the off time of that duty cycle, so making the duty cycle longer, and the amount of intensity of that current really is what creates a coagulant versus a cut effect or a blend of those two things. And so here you can see examples of what does it look like when you're looking at a piece of tissue, right? So coagulation all the way on the left, which is at a very low amplitude. And you see that effect, that's that little charring that's around where the probe is. Then you see a very high cut, where you're getting a lot of amplitude there. And then there's very limited space between every time the duty cycle goes through, and you're getting a nice deep cut in the second one on the left. Then you're getting a blend. So 50% duty cycle means you're giving a high amplitude, but then you're leaving space in between. So you're getting a combination of those two, right? So not quite as deep of the cut, but definitely some coagulant effect. And then you see this very low duty cycle, where you're getting a lot of char, a lot of effect around that area of time, because you're running energy, but you're stopping for a long period of time, and allowing that thermal effect to set in. So here's what it looks like. This is a regenerator. This is a VIO 300. There's a newer version that some of you might see now that doesn't have as much of the setting. It actually just looks a little simpler, because they've tried to simplify this, because they recognize that the vast majority of gastroenterologists, or general surgeons, to be honest, are looking for something where they plug it in, they play it, and it does its job, right? But I actually personally like this. And when I talk to our advanced fellows about this, I make them try to understand what it is that we do. So it says EMR on the top, which is endoscopic mucosal resection. So when I do a colon EMR, for example, I have a particular way in which I decide my settings. And it all goes back to the same concept I started with, which is, I want to manipulate that waveform to do something. So when you do a standard polypectomy, it may be a cold polypectomy with no thermal energy, which has become much more popular. Or traditionally, most people use the blue pedal, which is coagulation. So a limited amount of energy, a lot of effect to try to stop bleeding as the snare comes through an area. And the snare property also affects that current, and we'll talk about that. On the yellow side, which is what I typically use for hot EMR, I change my settings. And so you see three settings here, but it's not that complex. What they're really trying to do is manipulate the waveform, right? So what I'll typically use is like a 2-1-4, two effect, one cut duration, and then a four cut interval. Why am I doing that? This is really where the key of the concepts come in place. I use a 2-1-4 on my colon EMRs because I want a moderate amount of effect to a moderate amount of coagulation. So I don't want to just come through this large piece of tissue and just cut it, and it'll just start bleeding right away, right? But I want to be cautious because I don't want to use too much coagulation because I don't want post-polypectomy syndrome, where if I'm doing an EMR in the cecal wall, I don't want that energy to dissipate. Energy has to go somewhere. It's a living thing. It doesn't just go through and then stop. It stays there. The cut duration, that means how quickly it's coming through and the amplitude. I just want it to cut. I don't need it to be a very long duration. Otherwise, it actually, if you look at the waveform, it increases the amplitude and the amount of time that the power is on and that duty cycle goes up. So I just need it one. The cut interval, however, I have it at four. Why? Because I want time for it to coagulate after I come quickly cutting through the tissue. I want it to seal off, right? I don't want it to keep bleeding. Using an alternate example of the same thing as a waveform, if I wanted to do a sphincter anatomy, for example, use a different endo-cut setting, and I would just do one, one, one. So I basically wanted to just deliver fast energy, cycle through, have no stop time, so no really decrease in the cut interval, and I want it to have no effect. I don't want a bunch of char around the ampula. I just want it to come right through. So that's a one, one, one cycle. So that's me trying to try to explain to you how we can manipulate these settings, but it all just really goes back to the very beginning, which is what is the waveform doing and how are we trying to manipulate this energy to get it to do the end effect. So when you guys are looking at electrosurgery generators, there's typically two pedals. Yellow corresponds to yellow on the screen, which is more of a cut from the electrosurgical generator, and blue is more for coagulation. And again, that's more of that voltage that we talked about, how quickly it cycles through. Does it really make a big, big overall difference in terms of polyp, recurrence, and adverse events? It doesn't. So I think what's important here is you guys are going to go back to your institutions, and every one of your attendings, even within an institution, may have some slight difference on how they approach this. And at least for the RCTs, it's not made a major difference. But the principles remain the same. So everyone has a reasoning. They should have a reasoning based upon what I explained those waveforms to be and to do and what we're trying to achieve. That's the reasoning that I want you to hold on to and not stick to the dogma of, hey, it has to be this x, y, z setting, because you may come up with a better setting than what I have. And so when this cycle starts and you're delivering this waveform, it has to go through a circuit. So it goes out of the electrosurgery generator, through whatever device you have, through some end target where you're trying to either achieve coagulation of bleeding or cutting of a tissue, and then comes back to the generator. And that's a cycle of where the energy is traveling. And as it goes through that cycle, it's going to face resistance from the current. And this goes back to basic physics. So the resistance, as you can see on the screen, can vary depending upon what it is that it has to cycle through. So blood, very little resistance. When you look at fat, much higher resistance, bone, much higher resistance. And so that, obviously, you have to be thoughtful about when you look at how much current you're delivering to be able to achieve the effect, because it has to get through this area. And then the density. So any current, if you actually lower the amount of surface area that it goes through, that has a higher intensity. If you splay that same amount of energy over a larger area, then, obviously, the amount of energy focally delivered in one spot is going to be less. So if your snare is 4 millimeters in size versus 2 millimeters in size, the amount of current density is almost double in the 2 millimeter in size, assuming you're using the same settings, because you're splaying that energy out over a larger area. And that's where current density is important. Remember, as you've been in the lab now, so as you were in the lab, I think those were with me, I explained that when you're closing the snare, that current density is going up, and it's closing back towards the plastic part of the catheter. So you're actually changing the current density as you come through. That's something to be rather aware of as you're starting to cut through lesions. And here's a nice little example of this. You can see the current density is folding in, especially as the snare folds in, the current density goes up. So at the very end, you can kind of coming through things with a lot more current. And we talk about that with snare closure and transsection. So the diameter of the snare and the thickness of the snare are the things that actually really determine the amount of current density going through that time, along with how quickly your tech closes the snare. So you may be in a polypectomy, and you may have, it's a really big, broad, perunculated polyp, and you may be asked to kind of come through a little bit slower. So that way, it has time to go more through the duty cycle and create some of the coagulation effect as opposed to the cut effect where you're snapping through rather fast, you're delivering the energy rather quickly with high current density. All right, so that's the cycle that we're talking about. I already talked about this. Electrosurgical generator, through tissue, back to an electrosurgery generator. There's two types of devices that you'll hear about, bipolar and monopolar. Bipolar is a gold probe. It's one of the most commonly used bipolar devices, I think, that we use inside of endoscopy. And so no current goes to the body, so you don't have to pad the patient down. The current's actually going through the device, and the cycle goes right back up to the generator. So it's not going through the body itself. And we use a bipolar probe usually for cauterization of vessels in the setting of bleeding. So the only effect is on the contact tissue, no grounding pad. And you don't have to have as much power, right, because the cycle, it doesn't have to go through all this tissue to get back in the end of the cycle. It's a little bit different when you're looking at monopolar devices, which is the vast majority of devices. So if you have a polypectomy, ESD knives, sphincterotomy, needle knives, APC, you have to ground the person because you're creating a circuit that goes through the person that you're treating, through the device, through the person that you're treating, and then back to the generator. So it's a little broader circuit. So as I mentioned before, when it's traveling that area, it's going through things that have resistance. And we need to be thoughtful about where we put the grounding pad to perhaps make the circuit shorter, so it's more effective to what it is what we're doing, and to potentially avoid unnecessary impedance to that current. And so the area that we put the grounding pad, you'll typically hear, is clean and dry. We try to avoid areas with a lot of hair, because hair can cause impedance. We try to avoid areas that are extremely fatty. And we try to avoid bony prominences, so you necessarily won't put it on something where there's a very limited amount of tissue above them, like a scapula or something like that. So we typically like to go to the flank. The flank, especially if you're doing a colonoscopy, is a pretty short circuit. But even if they put it higher up on the flank, it's a pretty short circuit down to the stomach and so on. And so I mentioned a little bit about hair increasing the current density and potentially flammable, increasing resistance. So here's a nice picture of someone, and you can put it on the thigh, you can put it ideally on the flank, a little bit higher up, making the circuit shorter. But that's why we care about where we ground the patient and the value of how we're grounding the patient, how we think about the creation of the circuit. Again, all going back to that basic waveform that we're trying to create to do the effect that we want. When you put the grounding pad, and I would suggest this to all of you, I think it's really helpful to watch what the techs and nurses do during your first year. I mean, I certainly know that for our advanced fellows, I have them do some teching at some times during the year, so they understand all the devices. At the end of the day, you're the physician, so you're responsible for the outcome of that patient, right? So you need to know what's on the electrosurgery generator, you need to understand how it's all been set up, you need to know the devices. It's just as important as understanding the technique of the procedures that we do. So I would encourage you to pay attention to that. This is a really nice lecture, right after Raju does great lectures on polypectomy and his great tech training out of MD Anderson. And he always talks about how, you know, there's been times he's had a couple of bad bleeding episodes because he didn't really have the generator behind him, had it thought the techs had set it up the right way, and then get a lot of bleeding because it wasn't set up the way that they wanted. It's our responsibility to know this equipment, right? So a little bit about pacemakers and ICDs. So these can get affected because they have their own circuit, their own living electricity. And so their circuit can get affected by the circuit that we generate when we're doing endoscopy and using electrosurgery. So it's important to keep some distance between the electrodes if you can. You can place the pad away from that so the circuit interference does not get created. In some patients who are totally pacemaker-dependent, you may need to get cardiology clearance or have them independently paced and shut off their natural inherent pacer if you're doing a lot of cautery in a procedure. Most procedures, you don't use that much of cautery time. But some things, especially like a bad GI bleed, we're using a lot of APC, or certainly in my case for ESDs, I may use a lot of energy. And so then it's important not to create that interference. Same thing with ICDs, you can, again, ICDs are there for when the arrhythmia goes off, right? So you can salvage from that. You can shut them off, or you can have them far enough away if you're using just a little bit of time that you can just put a magnet on that for a period of time. But those are things that we need to be cognizant of because the electrical interference is a reality that can occur. I talked a little bit about APC. So APC is argon plasma coagulation. And so argon gas is ionized and sent out from this probe, and I'll give you a little video of the probe. And as it comes out, it gets energized, and it gets heated into the spark, and it causes basically a very superficial burn or coagulation of the area. The current intensity is not that high, and depending on how you manipulate it, from 20 watts to 90 watts, it can do different things, whether you're trying to kind of get an area to really scar down, or if you're just trying to superficially paint over little tiny vessels that might be oozing. It's more of a gentle way in which we can cause coagulation rather than a cut current. But of course, the current principles are the same, so you just need to keep in mind that you can manipulate the wattage or the intensity of that current a little bit to a certain degree. The other thing is it's contactless, so you don't want to be too far away. So it can only work within about 10 millimeters of the lesion. But if you're right on top of the lesion, it's not like that. It's not like a bipolar probe. And so what are the advantages? It's non-contact. So you can look at an area, you get better visualization, you don't have to just hold it there like the bipolar cauterization. So when you use a bipolar, you're putting the energy in, you're holding it there. When you turn the current off, you still hold it for a little period of time. And so you have what's called coaptive coagulation. Here you're further away, you're kind of just painting the area on top, and it creates a thinner eschar. The depth of coagulation is much lower, and it's much more even. It's a really easy way, especially if in the beginning when you're learning things like EMR, for example, and you want to oblate the edges. Sometimes we'll start with APC before, like a sneer tip. Or for bleeding, like a gave is another lesion that's very widespread, so you need to cover a large surface area to prevent bleeding, we'll use things like APC. And we'll have a little video of that here, too. So here you can see its ability to paint. You can see that kind of looks like a little fire that's shooting out. That's the argon gas that's being lit on fire. And again, you can manipulate the settings in terms of the wattage. You can also manipulate the flow rate, right, because this is really argon gas that's ionized as being lit on fire when we actually oblate these areas. It can be quite fun. It also relates to the Star Wars theme that we started out with. So applications of APC. Vascular ectasia, as I mentioned, gave us a radiation proctitis is another one that's been utilized for tissue ablation. So I mentioned ablating the margins after you've resected all the adenomatous tissue. You can use it for control of malignancy. You can use it as a salvage if you really crank the wattage up to ablate some tissue that can't necessarily be resected in palliative cases. You can use this as an adjunct to fistula closure because if you turn the wattage up, I use it sometimes as an adjunct to tor or outlet reduction when I do outlet reductions. And you can also use it for acute GI bleeding. It's really important to understand the generator and the electrocautery devices. I mentioned that, right? It's the physician. It's your responsibility. You want to keep these concepts very, very simple. So just understand waveforms. Keep in mind the electrical circuit that you're generating. Know how to set up equipment. Spend time with the equipment. Labs like this are a great time when you're going to ask a million questions. Play with any equipment you want. But when you get experienced techs or nurses, especially in that first couple of years, if you get a little free time, it's worthwhile going in the room, even not in the setting of actual patient care, and just asking, hey, how do you set this up? You'll get a lot out of that because you'll better understand what your devices are doing, But the purpose of it is how to troubleshoot when you get into trouble, and also understanding maybe where things can progress in the future as new devices come out, what are the concepts behind it, as opposed to just plug and play. And it'll keep you out of a little bit of trouble. So I think we have content, and then you write me notes up there, a little thing up there for them to scan. I was just curious, for the APC, it is non-contact, but if you are, let's say, on the tissue, is it for a higher risk of causing thermal damage? What's the downside? It's very superficial. But what you'll do is you'll clog up the probe very quickly, because the probe will get eventually coagulation on top of it, or eschar on top of it. So you won't really be able to create the effect that you want to create. You need some space there. So the space allows the ionized argon to come out, and it allows for enough time for it to be essentially lit on fire in order to be able to do its effect. Awesome. Thank you. Good question. Other questions? Everyone's got it. They're ready. They're ready to run the electrosurgery. Awesome.

electrocautery

electrosurgery

waveform manipulation

patient safety

bipolar and monopolar devices

argon plasma coagulation