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This is a common tool used by surgeons to make clean cuts that don't bleed. It's a probe that uses high power RF energy to cut and cauterise simultaneously.
This is the single use sterile pen that connects to a very complex and expensive machine that provides the RF energy at a fairly high voltage. The return path for the current is a flat electrode stuck onto a suitable area of the patient's body.
At the frequencies involved there's no electric shock effect. Just heat or burning at the point of contact. Further investigation shows that you can get blade, needle, ball and loop electrodes.
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This rather squirmy device is used by surgeons for making incisions in human flesh and then sealing up the winds, and it does so using a fairly high voltage in the region of hundreds to potentially thousands of volts at very high frequency. And as such, it doesn't really give a shock as such, it just burns, and this is just the bare disposable um surgical device that says single use. It comes sealed in a bag for each surgery, use and then gets disposed of for hygiene purposes, but the tip is not sharp uh just as well really given i've run my fingers on it. But when you push the top button here cut when it's connected to the machine, it will pass a high enough current that it will actually cut cut the flesh.

An advantage of this over a traditional scalpel is that the scalpel, as soon as you cut it, blood will be flowing everywhere. This effectively cauterizes cuts, but you also have another button called coagulate coag, which uh can be used to actually stop uh things bleeding just by running over the surface and what that does. It runs at lower power. So let's do some electrical testing this and see.

What's connected to what i would guess, this is basically just like almost a disposable multimeter probe, let's bring the meter in so we're going to guess that this here is the high voltage one and it's probably going straight to the tip, because it's well away from the Others - let's test that so on to there and on to the tip now what about so that is connected to the tip, but i guess others are the lower voltage signal. Let's put this across them: do they put a resistor across nope, maybe higher value resistor? I don't think i'll be using the other one as a common. Does it use another one as a common, the high voltage one? Oh, it is so uh that is now on the common here, which goes to the tip of the diathermy pen, and this is on one of the connections. Other connections is that just button per connection - oh, that is just a button to that one.

So that's the cut button. Is this connects this to this, and this is it going to be the same for the it is? I didn't expect that i suppose it makes sense in the sense that you've got a fairly high voltage. High current come out, so the circuitry would have to be able to actually withstand that. Maybe it's come up twice layers or something just to give a good separation, because it's quite nasty voltages and frequencies, so that is basically common and then the two buttons going to the common, which also goes to the tip and does all the burning.

Let's see if we can spudge this open, i don't think there's going to be a lot in it, it is really designed to be disposable. Is it welded shut in some way? I think it is. I shall bend it. Is this going to help? Have they glued it shut? I suppose, given this for surgery, they don't really want it filling out with blood.

Do they oh gruesome, let's uh, try and get a screwdriver in here at some point, i'm going to stab myself here and then wish. I did have a quarterizing pen to actually deal with it, so that is kind of opening up. Okay, we're getting there. I guess glued um.

Let me grab a pair of side cutters where's, my canipix. Oh there we go. Oh okay! This one has not been used. I'd like to say, it has not been exposed to blood.

It's very simple: oh yeah! It's just it's not even switches. As such, it's a a pre-made circuit board. Let me zoom down in this. It's just a circuit board with the three connections coming on and two little sellotaped on tactile discs and then the connection going to the output.

The black which they've got is the common is actually a burning tip. The other two are going straight to the buttons. No is that right, no, it's not right! I'm wrong red is going right up the middle to the tip here hold on. Let me get my meter.

It's covered over by printing. What hold on the sellotape is not helping here. Let's pull it, let's pull the tape off. It's so strange to see something like this just stuck together tape.

Ultimately, it is a disposable item. It's it's! What it does? It's, the all the circuitry. All the complexity is in the unit that actually does the high frequency rf energy stuff. Oh that's stuck on super well onto the cheap, uh srbp synthetic resin bonded paper type circuit board.

It's very cheap inside, but you know it's what it does it's what the bit that really matters here, yeah, i'm not doing very well here. I i'm kind of regretting not pausing for this bit, but not to worry. I think we all know the gist. Is the two buttons held down with sticky tape? I just wanted to check check what the connections were.

I'm just laughing around. Am i really is this even gon na help? So i'm guessing that when they put this together, this gets? Oh, can you unplug that then so for something that's disposable? It looks like it's unpluggable. I didn't even try that. So, let's pick those little discs off little discs are kind of almost like spot welded.

Oh no they're actually put through and folded back all right. So the white one is ducking backwards and forwards here the white is the common it's coming down connecting to the outer disc and then it's going down to the outer disc again and then it's going to the tip and the red and the black are the signals Back okay, so now, if i put this back in well, obviously it's not going to work now. I've done that, but if i put this back in, does that tip just actually just plug in then get the tip off it? Yes, it does so, even though it says it's disposable. Theoretically, you could just pop up a new tip into.

If you particularly, i don't know, do they have different shapes, i'm not really sure, but that's interesting, very interesting now. The other connection, just in case you're, wondering for this, is a pad that goes onto the patient. It just goes on to sort of fleshy area, and that provides the return path. The current, but there have been situations because, when they're doing surgery, the patient is under anesthetic.

There have been incidents when the pad has made a bad connection, and this has been used to cut at fairly high power and it's caused serious burns around the pad. Where it's not made of connection, so they kind of take it more seriously on patients who are under anesthetic uh, generally speaking, if you're doing it on a sort of like remedial thing, nothing too major sort of turn away and i'll do a local anaesthetic. The pad can go somewhere that the patient can actually give you feedback and say i'm getting a slight stinging sensation, but there we go it's disposable, it's functional, uh, the bit of equipment that powers. This will be the expensive bit, and this is just a very minimalist, simple disposable item, just basically circuit board placed in and then clipped together.

Very neat very interesting, although to be honest, it does make me feel just a little bit squeamish thinking about this thing in use, because you just know it's going to smell a burning flesh, but that's what these things do.

15 thoughts on “Inside a single-use electrosurgery/cauterising pen”
  1. Avataaar/Circle Created with python_avatars TheHipSurgeon says:

    I use this when peeling off the short external rotator muscles from the femur. The discussions below about the return electrode reminded me of the time when I did a research fellowship in Australia. I did surgery on sheep lumbar spines. Sticking a gel pad on a woolly sheep was impossible. One of the lab technicians, a Mr Love came up with the idea of a solid metal dildo which was passed up the sheep’s bum. It was known as The Love Electrode. Very effective it was too.

  2. Avataaar/Circle Created with python_avatars slugamano Junior says:

    We used to use an East German drum printer, Robotron EC7031. It used a capacityve drum position encoder, driven by a 200 kHz 100 V clean sinus signal. During setting the right encoder position if you touched the driver circuit you could smell the odour of your burning skin but couldn’t feel any pain.

  3. Avataaar/Circle Created with python_avatars Ralf Baechle says:

    There's also an indirectly heated variant more similar to a soldering iron. It's been used on me in the 80's during wisdom teeth surgery. No contact pad was put on me anywhere back then so it must have been an indirectly heated tip. Other than that all the pleasures described by Big Clive such as the smell of burned flesh and smoke from my mouth, not for the faint-hearted patient.

  4. Avataaar/Circle Created with python_avatars Andreas Grothusheitkamp says:

    My dentist used a nearly identical tool some time ago on me. I would think the current return path was capacitive coupled inside the chair. There were no other metallic parts in my vicinity. As far as I remember. And on the device front was only the blue wire and a earthing wire. But I could not see the backside.

    The other thing is. I don't think it is necessary to optoisolate the button inputs in the device. I would think the tip is simply the circuit reference (0V) and the high voltage is generated to ground. Which would make current metering easier too.

  5. Avataaar/Circle Created with python_avatars Karl Harvy Marx says:

    When I was trying to decide on a career, I "assisted" a vet operating on a dog that had long term problems after having puppies. It is a remarkably effective tool for cutting tissue without causing bleeding. The main thing I learned was a lot of care goes into cutting layer by layer and separating some of the layers for stitching up later. There was a bit of smoke but I don't remember it having a smell. As best as I can remember, he used the pen for almost everything. I enjoyed watching that. What turned me off was another vet castrating a goat–no anesthesia, slice to the bottom of the scrotum, a dizzying squeeze and snip, all with the poor goat screaming his lungs out. That nearly put me down for the count, and turned me off on being a vet.

  6. Avataaar/Circle Created with python_avatars David Springs says:

    I remember it well…a vasectomy while awake. The intolerable part was the smoke and smell. I think I won't be doing that again (for obvious reasons). No doubt they used these for my open heart surgery, broken femur surgery, hernia surgery, surgery to remove a cyst in the roof of my mouth, and rotator cuff surgery, but I wasn't awake for most of those. Kinda glad. Also wondering what's next?

  7. Avataaar/Circle Created with python_avatars Stephen Lounds says:

    Recently had operation under local to remove a lump on my back, which was a total success. My surgeon used one of these. Had an an awesome time watching the display on the main unit.

    Scar has healed well nice and smooth but looks a bit like a centipede form the stiches.

    Fantastic technology makes patients lives easier.

  8. Avataaar/Circle Created with python_avatars Afaq Saleem says:

    I had to go through a minor procedure to have some skin cautarize to deal with skin hardening on a finger. I got really worried when I saw pad and a probe and electrical current equipment, if its going to give me shock, lol. Surgeon explained its safe and no need to worry.

  9. Avataaar/Circle Created with python_avatars Mike S says:

    When I was an electronics tech we had a gold wire bonding machine used to connect surface mount components to other components or to gold covered traces on the substrate. The hollow tip the gold wire was fed through would vibrate at a very high rate of speed when it was pushed downwards (to close a switch), that created enough heat to melt the gold wire into the bonding surface. The wire bonds were very secure and could withstand several Gs. I'm not sure if the top of this device vibrates or if the frequency he mentioned just modulates the voltage it applies. Interesting tool.

  10. Avataaar/Circle Created with python_avatars C. Law says:

    I'm a vet student and saw my first laparoscopic spay last week, which was quite interesting – the exact procedure requires explaining anatomy and things which would be a bit of a nightmare in text, but the gist is if you imagine you have a dangly thing with a bloody great blood vessel going through it, you have a similar thing to this except it's a pair of grabbers/shears – you go along the dangly thing snipping it, cauterising each snip as you go, eventually cutting off the whole dangly bit entirely and sealing off said bloody great blood vessel in the process (without which the patient would bleed to death in seconds/minutes).

    Incidentally, surgical cuts bleed far less than you'd imagine – you can quite easily open up someone's entire abdomen with a scalpel with almost no blood at all; the odd vessel that does bleed can be clamped with a haemostat (kind of small locking pliers, basically). Cautery isn't really required usually, and can be actively harmful: you're killing the tissue either side thus they won't heal together, whereas the two sides of a scalpel cut will.

  11. Avataaar/Circle Created with python_avatars Tom Hoehler says:

    The electrosurgical unit has two waveform outputs. Cut waveform is a smooth sine wave, cautery is a nasty looking waveform. Two waveforms for two separate functions. And the cut mode is not used for the initial skin cut. That is done with a conventional blade type scalpel. Makes for a prettier scar.

  12. Avataaar/Circle Created with python_avatars Wayne Turner says:

    Hi ,I actually bought the machine that the pen fits in ,I could never find the probes ,The machine weighs about 40kg with a huge transformer .when you finish send me the pen and I can see if it works ? It lights up and when i tested for voltage it was really low voltage 2 vdc.where is the probe from? I just looked on Ebay and no 3 pin probes,if you want any pictures of the machine just ask ,best wishes stay healthy

  13. Avataaar/Circle Created with python_avatars Telliria says:

    Interesting story – We were called in to troubleshoot a problem in a surgery room. Whenever they used the electrosurgery pen all the video monitors in the room (except the surgeon's) went blue or static. Not surprisingly this was an EMI problem due to the device being plugged into the wall, very far away from everything else. It proved tricky to fix though, as the staff could not have a loose cable (grounding the device to the operating table) laying around for them to stumble on.

  14. Avataaar/Circle Created with python_avatars awmperry says:

    I remember them using electrocautery when my son was born by caesarean; I was sitting with my then wife (who was anaesthetised with an epidural rather than a general, so she could keep communicating) and found it fascinating to watch the wisps of smoke as they cauterised blood vessels as they went.

  15. Avataaar/Circle Created with python_avatars tycho says:

    Yes, there are different shapes and lengths of tips! Often, especially with minimall invasive small incision surgery, surgeons will bend the tip to reach around an angle. Being able to replace the tip without reconnecting the whole pen is efficient and more sterile 🙂

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