So I'm going to be talking to you guys about electrocautery. We have a nice diagram here, I mean a picture here from Star Wars. So we're going to start with a quote here. This is from an article in 1994 called Physics for Physicians, and it says, know your electrocautery. It is possibly the most dangerous tool we use in endoscopy. I have no disclosures. Here's a video of what might happen if you're not really sure of what you're doing with electrocautery. So be careful. You have to know what you're dealing with. So we're going to start with some basic terms from electrosurgery. You have to remember back to basic physics for some of these terms. So just a reminder. So current is the flow of electrons. The circuit is the pathway by which the current of electrons flows. And voltage is the force by which we're pushing those electrons along that circuit, and usually it's through a resistance. So if you remember Ohm's law, we can reorganize Ohm's law to V equals IR, or voltage, is the same as the product of current and resistance or impedance. And you can adjust any of those as needed to achieve your effect. So if you have a piece of tissue that has higher resistance, you may increase the voltage to achieve the same effect to get that current along. But you have to remember also, the more force you're putting in, the more potential for destruction. And then we'll come back to this later, but a definition of current density is important to understand. Current density meaning the amount of current that's flowing through a given area that you're trying to treat. So we'll cover that in detail later. Now we have to apply these concepts to endoscopy. We have to understand, what does the electrosurgical generator do? We have to understand the differences between cutting and coagulation currents, the differences between monopolar and bipolar circuits, and the understanding of force meaning power, and understanding, again, watts versus joules. So watts meaning how much energy you're giving at a rate, what's your joules per second. Joules meaning total energy. And we'll come back to current density towards the end. So we'll review all these topics. So what do electrosurgical generators do? Electrosurgical generators produce a high frequency alternating current. And the purpose here is to achieve a heating effect, a cautery effect. And so this is kind of where they fall along the spectrum of generation. So if you look towards the left, we have household appliances. They're typically in the 60 Hertz range. If you get exposed to a household appliance, this is where you'll feel a shock. When you get up to 100 kilohertz per second, that's where, or 100 kilohertz, that's where you get neuromuscular stimulation. This is around the frequency that anesthesiologists use when they're checking patients' stimulation during general anesthesia, during surgery. And then our electrosurgical generators are usually in the 350 kilohertz to 3 megahertz range. And then as you go further along, you see where AM radio and TV frequencies are. So between 100 kilohertz and 350 kilohertz is where the body loses its perception of the frequency. And so above 100 kilohertz, the brain no longer perceives frequencies at that level. And so that's why the patient does not get a shock when you're using thermal energy with our electrosurgical generators. So electrosurgical generators use a frequency above 350 kilohertz, where there's only a thermal effect. You don't get the neuromuscular stimulation. The patient doesn't feel a shock. And there's also no biochemical changes that occur at this range. So there's no differences, changes in the acid base of the tissue. So these are the basic principles for therapeutic effects for electrosurgical generators and the production of heat at the cellular level to achieve the desired effect. So remember, the heat is produced by a high-frequency alternating current. It flows along a circuit, and we'll get into the circuits in a second. And it's passing through tissue, and the tissue is what's providing the resistance and also completing the circuit for the current. Two basic principles to understand are the differences between cutting and coagulation currents. So cutting is achieved when you have electrosurgical generators above 200 volts. You're applying energy above 200 volts, or you're using a high current density to achieve a current cutting effect. What happens here is that the water in the cells boils very rapidly. And by boiling very rapidly, it causes the cells to burst or explode. With coagulation, you have a lower energy level. So you're under 200 volts, a lower current density. The cells here heat very slowly. So there's denaturation of the proteins in the cell. There's more desiccation and shrinking of the cells as opposed to that explosion effect. So these are the various temperatures that you can achieve these effects at. So when we have a high fever, 104 degrees, you can have cellular trauma that occurs at that level. But usually, that's reversible, and we recover after our fever. When you're up above 120, that's where irreversible cell damage occurs. And then when you're up at 212 degrees Fahrenheit, that's the level by which water boils. So that's where you get the boiling effect and the cutting effect from electrocautery. And somewhere in between that range, around 158 degrees, is where you get the coagulation effect. So not as high. You're not getting the boiling effect. You're getting more of that tissue desiccation effect instead. And when you get up to very high levels, carbonization is essentially causing a charring effect on the tissue. Now we can actually manipulate our electrosurgical generator to achieve different temperature, different thermal effects, depending on the tissue that we're trying to treat and the desired effect of what we're doing. We'll start all the way on the right side. When you have the pure cut mode, you have a constant waveform, constant energy. And that's a pure cut effect. Whereas on the opposite side, you have more of a coagulation effect. You only have 6% of the time in cutting. 94% of the time, you have a cooling off effect. And so the short bursts of cut with predominantly cooling time provides more of a coagulation effect. And it's during that cooling time that the tissue will desiccate instead of actual burst. And so for a lot of the different approaches or applications that we use in endoscopy, we have a blend between cutting and coagulation currents. And so you can manipulate that to achieve the effect that you want to, knowing your surgical generator. And here are some examples of different things that you can change when you're using your generator. You can change the cutting cycles. You can change the intervals between the cuts to achieve whatever effect you're trying to accomplish. Here again, so differences in terms of the effects. So all the way on the left-hand side, we have a low voltage, less than 200 voltage, but a constant waveform, a persistent waveform, so you have more of a coagulation effect. Right next to that, you have voltage greater than 200, so you're going to get more of the cells bursting, more of the boiling effect. And so you have cutting. It's almost a complete cut. There's very little coagulation effect with that, as you can see in the diagram. The next one shows essentially a 50% duty cycle. So this is some cutting and some coagulation effect, so you have a nice cut, but you also get a coagulation, a burning of the adjacent tissue. And then all the way on the right side, that's predominantly coagulation effect, so very little cutting, mostly just coagulation and burning. It's also important to understand resistance, the concept of resistance or impedance. If you look on the left-hand side here, you see that blood and gastrointestinal mucosa, they're very good conductors of electricity and energy. On the other side, you have bone and plastics, which are insulators, so they're poor conductors of energy. And so the higher the resistance of the tissue that you're trying to treat, the more that there's an obstruction to the flow of that current, and so you need to produce a higher current to achieve the desired effect. And this is important in a lot of the applications that we're going to use. As an example, for instance, the sheets for our tools are all designed in plastic, and that's to protect us from the energy in that circuit. We're not going to feel the electrical effect, our nurses, our techs are not going to feel the electrical effect, because we have that insulator between the device and ourselves. So it's important to know your generators and the units that you have at your respective institutions. You can either go back and kind of learn what you have and what are the ways to manipulate that to set the desired effects that you want. All the different generators that are available have all the different settings that you can adjust as needed. As an example, I work in an ambulatory surgery center and then two different hospital labs, and each of our labs has three different generators. So we know three different generators. We have to know how to manipulate each of those generators to achieve what we want to. And there's differences between different types of polyps in the hospital labs when we want to do a sphincterotomy or other effects using argon plasma or so. So become familiar with the unit that you have and how to use your unit properly to achieve the effect you want for your goal. Now how do we complete the circuit? So we've talked about the cutting and coagulation currents, but we have to make sure that we have a complete circuit. So the electrosurgical generator generates the current, and that goes to the tissue. Then we need that current to return from the tissue back to the generator. And there's different ways of achieving that. There's bipolar and there's monopolar circuits. So bipolar first. We actually use this less frequently, I think, than monopolar in endoscopy, but you may have some experience with this when you're treating GI bleeds if you're using gold probes. So in bipolar technology, no current actually goes through the patient. There's no need for a grounding pad with this. The current goes to the tissue within the device, and the return is also within the same device. So you have a delivery and a return electrodes within the same device. That's how the design of the gold probe is. Over here, you have the delivery and the return directly adjacent to each other. And the benefit of this is it provides a very nice local effect, and only on the tissue that the gold probe or that the device is in direct contact with. There's no current running through the rest of the body. There's no return circuit. The circuit is a very, very limited circuit. And so you can have a very nice local treatment effect. And so because of that, we have low maximal power outputs for these devices. This is in contrast to monopolar, which is what we more frequently will use. This is what we'll use for polypectomy, for sphincterotomy, APC. And the circuit is completed by going through the patient. And so for this reason, we use a grounding pad. So there's no return electrode within the device. There's only the active electrode, the delivery electrode. And then once the current has its effect in the patient, then you have to complete the circuit. So the current will then travel through the patient's tissue to the grounding pad. And then the grounding pad takes that and completes the circuit by bringing that back to the electrosurgical generator. So you need a grounding pad to have this effect. Some details about grounding pads. So there's a few different types that are available. Grounding pads, as I mentioned, are necessary to complete the circuit. And they're important because they help to disperse the current. So when you're applying the device directly, you're applying it to a very focal area where you're doing the treatment effect. And then that current is going to travel to the grounding pad. So the grounding pad actually has a bigger surface area to disperse the current. So if you had it at a very focal area, you'd be causing a burn at the point where the grounding pad is, too. So by having a greater surface area, you distribute that current. And so you don't get a burn on the patient on their skin. And for this reason, split pads are also preferred. Split pads give you better contact with the patient. But the generator and the pad are able to measure the resistance between the two portions of the pad. And so it's going to be able to compare the two. It's able to detect disparities between the current density and the flow on both sides. And it can actually shut down the machine if it detects a major discrepancy, so that we don't lead to a burn or unsafe treatment. Four basic ground rules for grounding pad safety. The area should be clean and dry. You don't want to apply this to any wet areas on the skin. You want to choose an area where there's good musculature and vascularity. And this is important because you want good vascularity. You want an area that's going to have more higher water content of the tissue to allow that current to travel. So you want to avoid bony prominences, avoid prosthetics, because those are areas where there's going to be higher impedance, higher resistance to your current. And you want to choose a place that's closer to the electrosurgical site. You want to keep that circuit smaller. You don't want it to travel throughout the body. You want to keep it a smaller circuit. So the ideal placement of the pad is usually on the flank. The patient's flank has good musculature and vascularity. And it provides the shortest circuit possible because the majority of what we're going to be doing is within the abdomen. So if you have it on the flank, you create a short circuit. In certain instances, for instance, in a patient who has a cardiac device or who has a hairy back, you might want to choose an alternative site such as the thigh. So hair, I just mentioned hair. So how does hair affect your current? So what hair does, it creates an air gap between the skin and the pad. And that creates an increase in resistance. And that air pocket that develops can actually lead to a buildup of current and actually can lead to sparking and singeing of the hair because the hair is flammable. So you have to be careful. So you want to eliminate any air pockets between the pad. You want to make sure that pad is nice and flat and right on the skin. And also you want to avoid tenting, again, because any space that's there can create an air pocket that can lead to sparking and burns on the patient's skin. Pacemakers, so it's important to know your patient's cardiac history, too. What kind of device do they have if they have a device? Is it a pacemaker? Is it an ICD? Is it a combination? So pacemakers, it's important to keep that in mind because the electrical current that we're generating can manipulate the pacemaker. The pacemaker can get confused sometimes by the electricity. So you want to keep your grounding pad at least 15 centimeters away from the cardiac device or really any monitor that we have. So we have all of our patients with EKG monitoring throughout the procedure. You want to keep the grounding pad at least 15 centimeters away from those electrodes So you can try to put it on the leg, on the thigh, or the hip to try to limit the potential for interference. So in patients who are pacemaker dependent and you're planning to use a fair bit of monopolar cautery, if we have more of a prolonged treatment time, for instance, when we're using APC to treat GAVE in the stomach, you might want to have cardiologists involved so that they can actually interrogate the device before and or after the procedure after you're done to make sure that the pacemaker is in its actual programmed setting. Rarely you can have these patients actually they flip or they change during the cautery session and then it may not return back to the original settings when you're done. So you have to be very careful and try to involve cardiology if needed. It's particularly important for patients that have ICDs too. So with ICDs you have to be extremely careful, right, because the current that goes through the body can actually, the ICD can think that that's actually an arrhythmia and can defibrillate the patient. So you want to have, you want to do this where you have access to a magnet, have access to your AED with the transcutaneous pacing available. And you want to involve your EP specialists or the device reps so that they can actually interrogate the device after you're done with it so that they can make sure that it's back in its original settings. You can use the magnet to deactivate the sensing during the treatment and then when you take the magnet off, the device should go back to its original programmed mode. But you should always be careful and we will always have our device specialists or device reps come and interrogate after we're done. So now getting to the concept of current density. And this diagram is meant to kind of show you, illustrate this concept. So some of us when we were young boys might have played with magnifying glasses and used magnifying glass to concentrate the solar energy, the heat energy from the sun into a focal area. In this example he's trying to take care of some ants. Instead of using a bug killer, he's going to take care of it himself. But you can concentrate that thermal energy in such a way where you can cause a burn. You can cause a burn on a leaf or a piece of paper. So this is the same concept as how we're manipulating current density in patients when we're using electrocautery. And this is primarily when we're talking about, for instance, using a polypectomy snare. The tighter you hold the snare, the tighter you pull the snare, the more concentrated that current density is going to be. You're going to have more of a cutting effect. And it's about achieving a balance for the type of tissue that you're trying to treat. So if you have a polyp that has a thick stalk, you might not want to just cut through that because you're going to have a vessel in there. You want to make sure that the vessel doesn't bleed. So you want to use some coagulation current. If you have the snare a little bit looser, you can get more of the coagulation first before you completely complete the polypectomy. As opposed to maybe more of a flat polyp where you want to limit the amount of transmural effect of the coagulations, you're going to prefer more of a cutting effect and less coag so you don't get more of a transmural effect and transmural coag and reduce your risk of post polypectomy syndrome, reduce your risk of perforation. So it's important to try to find a balance depending on the tissue you're treating. So you should start to see the occurrence. You'll see a little bit of a white treatment effect on the edges of the polypectomy site. Polyp's been removed. And no bleeding. We've got a nice polypectomy scar right there. And the white is the coagulation effect from the polypectomy, from the snare. So that's a typical hot snare polypectomy. So a little bit about APC now. How do we use APC? What is APC? How does APC work? So APC stands for argon plasma coagulation. Argon, if you remember, is a noble gas. It's a very stable gas. But to our benefit, it's easily ionizable. So it has a nice effect for us to use for cautery. This is the design of the APC probe. So the probe that you have actually has a small electrode in the center of it. And then it has argon gas around that electrode. And so when you activate the electrode, the argon gas becomes a plasma. It becomes ionized and it becomes a plasma. And once it does, it carries that current to the local tissue for treatment. This is a non-contact device as opposed to your gold probe or your bicap cautery that you're gonna be using for bleeders. This is a non-contact. So you want to be close to the tissue that you're treating but not on the tissue. The current can travel up to 10 millimeters from the tip of the device. And you can adjust the settings on this also depending on the type of treatment effect you're trying to achieve in the part of the body that you're working in, the part of the intestinal tract. So here's an example of APC. So it's non-contact. The current travels to the closest or the best area of conductivity. And it provides a very even kind of uniform coagulation effect. It's limited to about three millimeters of depth. It leaves a very thin SR over, which is very nice for superficial treatments. You can see that effect. There are different types of probes that are available. In the left-hand side, you see a forward flow probe. So the flow of the argon gas is directly forward out of the tip of the probe. You can also have side probes or circumferential probes where the flow is directed more tangentially. So if you have a tangential approach to the area that you're treating, you might prefer that probe instead of the forward flow probe. And here it doesn't come up very well, but on the right-hand side, you see kind of the optimal approach. The tip of the probe is about, or less than a centimeter away from the surface. And the current provides a nice thin treatment effect across the area of treatment. When you have contact, when you create contact, you can actually direct that argon gas into the submucosal area. You can get a deeper burn, and this will increase your risk of complications. And the treatment effect is very localized. And so this is really not what you're trying to achieve in these situations. You really want a nice superficial cautery effect. Here's another video. Kind of seeing a nice, good control. You keep the tip of the probe very close to, but not touching the mucosa. So applications for APC. We predominantly use this for treatment of vascular ectasias, whether that's AVMs in the stomach or small bowel, or for treatment of larger areas, such as that we see in GAVE or radiation-associated vascular ectasias in the rectum. You can use this for tissue ablation. So if you're doing a polypectomy and you have a portion of the polyp that you haven't been able to completely resect, you can ablate that polyp tissue to destroy the cells. You might use this to treat the periphery of a polypectomy site after a mucosal resection. Bleeding and malignancy is always hard to treat. Sometimes you can use APC to manage that when the patient can't have a surgical resection. You can use this as an adjunct to fistula closure. So in patients who have a persistent gastrocutaneous fistula after a PEG tube's been removed and they have constant leakage, you'll try to clip the inside of that fistula closed, it's helpful to use APC to trigger some re-epithelialization of that area. APC is not very helpful for the treatment of acute bleeding because it's a very superficial treatment effect. You can get immediate hemostasis or very quick hemostasis for AVMs, but really when you're dealing with ulcers and most of our acute GI bleeds, you wanna use a device that gives you good coaptation, which you can't really achieve with this. There's a number of considerations you need to keep in mind depending on where you're treating, what kind of tissue you're trying to treat, and then you can adjust the power, the flow, and the frequency with which you're tapping on the pedal to trigger that current. And so, this I think is the final slide. So it's very important basically, in summary, to know your generator, know the effects that the generator can create. And as the physician, this is really your responsibility. You're the one taking care of that patient. You shouldn't rely on the nurse or the tech to know exactly what they're doing. Of course, they're gonna know what they're doing, but when you go back, try to learn. Learn from, watch what your attending's doing, watch what your nurse is doing. Try to find out why are they changing different settings? Why are they using the setting that they're using? Ask questions. Why are you using for this polyp? Why'd you use something different for a different polyp? When you get into more advanced things with APC, why are you changing the flow rates and things like that? So know your equipment, know how to set this up because ultimately, this is gonna be your responsibility. And I think that's it. Any questions? Thanks, guys. Thank you.

electrocautery

medical procedures

electrosurgery

current

voltage

resistance