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Soldering irons get hot. Light bulb filaments also get hot. Cautery pen filaments get so hot that they can cut through flesh effortlessly. Physicians routinely use them for small surgical procedures. Unlike a scalpel, a cautery pen uses the heat from the filament to both cut and seal bloodflow, which can minimize the risk of infection and post-op complications. They are available at most online medical suppliers for around $12 each.

We ordered a handful after our surgeon friends in Ocotal, Nicaragua mentioned that these devices are a huge help, but their disposability makes them too expensive for them since they cannot be resterilized. That means that our friends can only use them when a donation of equipment comes into town. Opening one up and figuring out how it works led to some fun surprises.

The pens arrived like any other medical device, sealed in a bag with the proper warnings.

Do Not Reuse!

Sometimes that’s the most important warning in medical hardware. There are some medical devices, such as syringes, that you absolutely, never ever want to reuse. There are others that are designed for reuse after proper cleaning—laryngoscopes, stethoscopes, surgical forceps. The manufacturer of these cautery pens definitely wanted us to know that you cannot reuse this product. In practice, they run out power and then you are forced to throw them away.

There are other models of cautery pens that have detachable tips, but these are twice the price. Any possibility of using safety as an excuse for making these devices automatically disposable did not make any sense. So we decided to open up and understand the intricate mechanisms that make up a cauterizer.

I expected a transformer, some type of power converter, a super capacitor. Instead, $12 gets you the electronics complexity of a pocket flashlight. Maybe they weren’t so special after all?

Aah, the tips. Maybe the tips are in fact special, some sort of complex alloy that’s optimally designed to heat up using two AA batteries. That would justify the price, and why the manufacturers can rack up the cost of a reusable one to $24.

To investigate, we took the metal tips down the street to our friends at the MIT Materials Science Department, where they have a Scanning Electron Microscope. In the hands of material scientist Mike Tarkanian, we performed a chemical analysis on the tip using a technique called EDXA (energy dispersive X-Ray analysis). In a moment, the instrument told us what the material make-up of our tips were: Mostly aluminum, with a few other trace elements.

Additional research led us to something called Kanthal thermocouple wire, which costs around $25 for a spool of 1000 feet online. Given that our tips measure around 1.3 cm, that yields roughly 23,000 tips per spool. That’s a lot of surgeries for $25, and that’s the way it should be.

Jose Gomez-Marquez

I design medical devices for the developing world at MIT. Our lab creates DIY kits called MEDIKits for docs nurses in the field to come up with their own solutions.


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Comments

  1. David says:

    I don’t get why you’re so incredulous…

    Our lab used to hack these for re-use (in acute studies only), and before they were on the market, we used to build our own using the handle from a soldering gun. $12 for a disposable flashlight, which comes in a sterile packet, and is subject to the myriad of quality control and regulatory oversight applied to medical devices, seems a reasonable deal to me.

  2. I think most of the $12 is paying for the sterilization, quality control, and legal fees that medical equipment must undergo.

  3. Dave Nash says:

    I hadn’t realised these were for medical use; I have an identical tool used for carving wax used in lost wax casting, bought for around £20… I feel robbed!

  4. Dave Bell says:

    Sounds typical for Medical Products. Nothing’s too expensive, where your life is concerned, right?

    Another example:
    We’ve all seen countless medical and trauma TV shows, where first responders insert an IV line in the victim, and hang a liter bag of Lactated Ringer’s Solution (LRS). LRS is a dilute solution of various salts and sugar, in a sterile container, and serves to maintain blood volume until bleeding can be stopped and suitable blood or plasma is available for transfusion. A real life-saver, without argument.
    In a hospital, they’ll charge you something like $100 for that bag of (mostly) water.

    On the other hand, it’s a great tool for supportive treatment of small animals. We’ve saved several cats with failing kidneys, while their bodies heal and they recover, with subcutaneous (under the loose skin) infusions of LRS.
    One chain veterinary clinic charges $26 for a bag of LRS, *exactly* the same product, made to exactly the same standards, purity, and sterility, as the ones in the ambulance.
    A local non-chain vet charges us $6 for the same bag.
    A major on-line veterinary supply sells it – again, the *same* thing – for $4.99.

    And a sterilized throw-away 2-AA flashlight with a loop of aluminum wire costs $12.

    1. MikeCBET says:

      Hospitals also have vital departments that will never generate a profit. Emergency Departments, Neonatal ICUs, anything women’s health (mammography, etc), Oncology treatment will never ever make a profit for a hospital. To keep these departments open, hospitals have to make as much profit as they can in other places. I’m not saying it’s right, but that’s the way it is.

  5. Nick says:

    The majority of the markup has to be from medical device regulation and sterilization. Each box is supposed to be tracked by serial number down to the end-user through the distributor too, in the case of a recall. I’ve had some recalled for a production mistake that left the safety switch loose, which apparently led to some boxes of them on fire.

    Plus, the market for them is relatively small; not a lot customers to spread that cost over. Most get used in kits where no electricity can be counted on, or for offices with small volumes. The cost of going to special-purpose equpment (one of which is made by the same manufacturer) where the entire handle is resterilizable and there’s lots more control of power/temperature.

    1. Nick says:

      Accidentally published when the bus bumped a bit…

      Anyways a full-on electro-surgical generator or hyfrecator makes a lot more sense cost wise, compared to a few boxes of disposable cauteries. Probably not for a medical-missions trip though.

      It’s neat to see one apart though, if I remember correctly one of the many warnings on them is not to disassemble because of danger. :)

  6. With the addition of a pot/PWM circuit, they look perfect for welding plastic. …and that wire sounds like a good match for an extruder head.

  7. mzl says:

    The first step in the evolution of the lightsaber.

  8. Dustbuster says:

    Are these not to be reused because of the danger of cross-contamination? I would have thought that anything hot enough to cauterize flesh would also kill any pathogens it came into contact with. Even if not, it seems like hacking the disposables so the tips can be replaced and/or resterilized would be the way to go.

    1. joe says:

      I am a bio med equip tech and I work with medical missions full time. The contamination can come from a few sources. Yes, the TIP gets hot and is sterile, but only the tip. This can become contaminated if it is not in a sterile container after use, but the entire unit must be sterile or the germs can migrate to the tip. The handle after touching with non-sterile hands becomes contaminated. It is considered contaminated even during surgery, now listen carefully, it is contaminated with the patient’s internal bodily fluids so it is still considered sterile to that operation, not another. The cost to re-sterilize it is very high considering the cost to purchase the unit. It cannot be treated in an autoclave (steam heat and pressure), you cannot soak it in a solution (parts internal can corrode and short). Your only safe option is to gas sterilize it. The unit is not water proof so germs can get inside it once the package is opened. Gas will enter it and sterilize the interior. So, it becomes a cost issue. I have only seen these used for small operations not for a more invasive surgical procedure, basically cosmetic type of surgeries. By the way, you can light a propane or natural gas stove with these as well.

  9. Chris says:

    So where do the batteries end up? Do they just end up in the landfill?

    1. Eric says:

      I would imagine it is incinerated like most medical waste.

  10. TheHeadlessSourceMan says:

    That tells us all the pieces, but could you post something on how to build our own?

    1. This will definitely be part I of II towards make these more accessible, particularly in low resource areas. Sterilization is also important and have a fairly mature project on using solar power as well as interesting forms of affordable gas sterilization in developing countries. It was great to confirm that there a lot of you out there who were already hacking medicine in this way!

  11. Daryuosh says:

    Hello,i am seurger i want to know how much is price reusable cautery pen with chargeable battery,can you send to Azerbaijan Baku.I am waiting you.
    Best regards
    Dr.Jafari

  12. […] on event for that week — Little Devices Lab person cannot make it personally, but suggestedhttp://makezine.com/2012/03/20/the-secret-life-of-disposable-cautery-pens/ […]