CGM in The Operating Room

Yes, I totally get that, but when we go to theatre we take out all piercings to avoid the current ending up frying our ears, umbilicus, more sensitive parts in some cases…

What are the sensor electrodes made from? That is my concern. Might they act as a piercing? The old non Enlite Medtronic electrodes looked to be made from copper, which I was told last month is a decent conductor. Not sure about the new ones or Libre. I’ve not ever seen a Dexcom.

I’m quite clever at some things, but rather ignorant about current, volts, amps, conductivity etc. I’ve tried to learn, but…

I just don’t get electricity and where it goes and how much damage might occur.

This is absurd! :smirk:

I think you meant to say “jewelry”, not “piercings.” (A piercing cannot be “removed”.)

This is not the reason why jewelry is removed before surgery. Where did you hear this? Can you link to a reputable source?

1 Like

I normally remove all of mine. However last time in, the doctor siad it was fine to leave each of them attached.

Sensors are not electricity.

1 Like

@Morrisminor72, my degree is in Electrical Engineering (and physics). I know dis tuff.

Even blood, which has about the lowest resistance of anything human, is still not conductive enough to draw much of a current at the small voltages we’re talking about here. Utterly, totally, completely safe.

The quick, easy-to-understand explanation for everyone: The bugaboo to be worried about is Power. Power is the rate at which energy is expended/consumed, and energy is what messes with tissue, by heating it (or burning, in the extreme). Higher power, higher heating rate. Obviously, if the rate (power) is too high, tissue will heat faster than the body can dissipate it, so damage results eventually (faster with higher power). Sunlight is low-power enough that your body mass can dissipate the heat – but its there, that’s why the sun feels warm.

Take everything explained above, then think about microwave ovens. Higher power ones heat things faster, right?

Now, the standard unit of power in the metric system is the watt. Turns out that with electricity flowing through something that resists it (which is everything except superconductors), the power dissipated in the “thing” from the electricity flowing through it is simply the voltage the “thing” is in contact with, times the current that flows through the “thing”.

At 3 volts, the current that flows between any two points on or in the human body is miniscule. Concomitantly, the power dissipated therefore (voltage x current) is miniscule. So much so, that its inconsequential.

Now, it turns out that if you double the voltage this will also double the current, so the power will increase by a factor of 4! This rule generally holds for most “things”. So, while 3V doesn’t cause any problem, 110V will, being around 37 times the voltage resulting in 37x37=1369 times the power.

This is why household voltage (110V) will fry you, while 3V won’t even register.

1 Like

@Dave26, it’s not easy to follow what’s going on in this entertaining discussion, but I believe @Morrisminor72 is not worried about being electrocuted by the battery in the CGM transmitter, but instead about being electrocuted by an electrosurgical pencil via the CGM sensor/transmitter. These days, electrosurgery is very common. It does involve relatively high voltages, but at relatively high frequencies (a few hundreds of kHz I think). High-frequency ac current flows from a generator, through a pencil, a plasma arc established between the pencil tip and a patients skin, then disperses over the patient’s skin and returns back to the generator through a dispersing pad attached to the patient. The plasma arc serves as a “knife”. High frequency current flows through a wide area of the skin only, which is why one cannot be electrocuted, although the activated pencil can and will arc to whatever maybe placed in its vicinity, which is probably why @Morrisminor72 is saying that jewelry and such are not allowed in the theater. Some years back I had the pleasure of being the patient in a minor electrosurgery (in the theater :wink: ), which did not require general anesthesia, so I was able to converse with the surgeon, and to smell some burning flesh in the process (well, my burning flesh :slight_smile: ). Assuming a level of competency by the surgeon, the process is much safer compared to classical surgery.

No, no “reputable source” but it was something I was taught at medical school, many years ago. I no longer work in theatre, so it has not been top on my list of research priorities.

And in Australia, where I live, “piercings” are any jewellery or ornamentation that is inserted in skin. I am not quite sure what you are getting at here with regard to my command of language.

Given I have been accused of being silly and absurd in this thread, I shall leave you all to your expertness and quietly depart.

Thankyou Dave26 for your explanation. My concern remains that diathermy is not low power. If you say that blood and tissue would not conduct it, I believe you. I am fully aware that I cannot be zapped from within the sensor, seriously, I am not that stupid!! But current from the diathermy knife to the electrode plate via the sensor? That was my concern. Bye.

Indeed. Diathermy (i.e. electrosurgery) is not low power at all. I believe in the order of 50-100 W is dissipated in the arc and on the spot where the cut is made. That’s how the electrosurgical pencil cuts through! Your concerns @Morrisminor72 are reasonable and well justified. I think the responses you’ve received earlier were due to some misunderstandings, so no hard feelings.

2 Likes

@Dragan1 thanks for the awesome explanation!! :clap: While I’m steeped in physics and engineering, I’m a complete ignorant when it comes to what you described above, and it helps a lot to understand what the concern is.

Also, I was fascinated by what you shared, so went and did some googling to learn more. Fascinating… thanks again!

It’s been quite a while since I’ve been to the barber to have leeches drain some of my diseased humors… seems medicine has advanced a bit :grin:

1 Like

Help I have been trying to send you a message about the study, I have type 2 and have a smart phone.

Susie8

(post edited by TuDAdmin to remove email address - to private message members, click on their avatar picture and you’ll see a large button “Message”)

Well, dang. I am very unhappy to hear that, and at least for my own part apologize for what seems to have been a lapse in community civility. It really did seem like the responses to your comment were unnecessarily harsh and even somewhat misdirected. I had to look up what a diathermy knife was, and when I did it struck me as not at all absurd to worry about such a device coming into contact with other electrical equipment inserted into your body. Even if the answer is that there is no reason for concern, it could be phrased in a way that doesn’t imply the person asking is somehow idiotic or out of order. I for one would hope you’d stick around and give us another try.

2 Likes

What a GREAT idea to create a cheat sheet for the surgical team Sue27 ! Is this something you would consider sharing either publicly or privately? I personally would be very interested in something like this, especially since I am a frequent customer at my local Ortho.

Sorry @Dave26, you are WRONG, WRONG WRONG . Electrical leakage is an EXTREME HAZARD - this is a well known alternative fact. If you want proof I found this on t’internet

1 Like

I had exactly the opposite reaction from my surgery team during my double trigger finger release (which is admittedly a short 30-45 minute surgery).

Not only were the team largely uninterested in using my CGM (“we have to rely on finger stick tests” --yes, by all means confirm with your tests, but keep be the CGM receiver nearby to alert you of potential problems), they talked about the possible liability of losing the receiver as I was transferred from bed to bed, room to room. The surgical team had their way of doing things, and they were uninterested in having that rhythm disrupted.

In longer surgeries with diabetic patients, they do finger stick tests once per hour(!), and as such prefer blood sugars to be high when entering surgery because of this. It’s a totally messed up practice when there is clearly a better, healthier alternative, but that’s how they do it. It’s done for the anesthesiologist’s benefit, not the patient’s.

Oh and by the way, the pharmacists are the ones who adjust patient insulin levels in hospital, but for some reason that task has been farmed out to the anesthesiologist in the surgical suite. So in reality, the anesthesiologist generally does not have experience managing insulin levels in any context other than for the occasional insulin dependent diabetic while in surgery. This explains a lot, since they don’t have a big picture experience with diabetes. Hospital pharmacists at least handle day to day dosing of diabetic patients while in hospital.

This was explained to me by my wife, who was the pharmacist on duty in the OR during my surgery, and is very good at insulin dosing.

I went to a doc for trigger finger release and that bozo wanted to give me general anesthesia! I was incredulous, called his staff back another day to verify that he would refuse to do it under local. He declined. I dumped him.

Then I went to a great hand doc who did it under a local and it was a breeze. He did 2 of those in the course of a year or two. The results were perfection.

I didn’t have a CGM then BUT I’ve had surgery recently (knee replacement) and everyone was fine with me wearing both my pump and CGM. It was NO BIG DEAL. Any surgeon or anesthesologist in this day and age that balks at patients wearing one or both, should be avoided. I’ve had NUMEROUS surgeries while wearing a pump. I haven’t had the CGM long enough but for the knee surgery.

OMG. Been there; done that! They do a terrible job.

I never allow anyone in the hospital to tell me how much insulin to use and give my own shots, but when I had kidney stone surgery, I did follow my excellent surgeon’s advice and lowered my insulin the morning of surgery. I also allowed them to take control of my glucose levels during surgery. Everything went well.

The anesthesiologist is going to monitor and adjust bg’s as necessary, even if one is wearing a pump. that’s something to be discussed with them during pre-op. I give them my ISF and tell them I dont want to climb above a certain number. The docs do not want people running on the low side for surgery. they hate that. (My wife is an OR nurse so I speak with “insider” knowledge as well as my own experiences which are far too many).

I feel an overwhelming sense of distrust of doctors to control my BGs when under their care, especially when under anesthesia. Doctors feel an inordinate amount of fear regarding hypoglycemia. When they’re given the responsibility to control BGs, they will, almost to a person, choose to give hypoglycemia a wide berth. This, of course, often comes at the expense of hyperglycemia during the critical times of injury and illness when normal BGs can play a large role in outcomes.

Why do docs do this? What they fear most is a hypoglycemic episode on their watch. It embarrasses them in front of their colleagues and makes them vulnerable to lawsuits.

A blood sugar of 240+ mg/dL (13.3 mmol/L) is barely even noticed by anyone in the surgery theatre. The patient, however, if they’re paying attention, will notice and likely resent the choices made by the doctor in charge of BGs.

Of course, things can happen that are beyond the control of surgical physicians and I get that. What I don’t get is deliberate harm caused by doctors who think a few hours of hyperglycemia will not hurt anyone. Many studies have documented the role that hyperglycemia can play in post-surgery outcomes. I know it does increase the chances of succumbing to a hospital antibiotic-resistant super bug known to reside in many hospitals.

You might distrust them, but anesthesiologists do this for a living. They aren’t equivalent to the bumbling nonsense that other doctors exhibit when dealing with diabetic control, Terry. My wife has many years of experience working in the Operating Room as a nurse. She is currently employed AAMOF, at a far nicer facility than the previous one. When you “go under” your life is in the hands of the “gas man” regardless of if you are diabetic or not. They monitor your vitals and keep you alive while the surgeon does their thing.

I was once given 7U during surgery because I was too high. That was prudent, it worked out fine, and that is what the gas man should be doing—Keeping you out of hypo range, but keeping you from going excessively high. Again, communication is key to having them keep you within your comfortable limits, assuming the range is feasible. I don’t think any of us want to come out of surgery 300+.

Perhaps you fall a bit on the “control-freak” side? :slight_smile: No offense, please. I’m like that too, but when it comes to surgery, you need to have some faith that the people in the OR are the right ones for the job. Speak to the gas guy the night before surgery if not the day of. Tell him your concerns. Most all of them are very, very capable.

finally, choose your hospital wisely. Choose your surgeon wisely. And above all choose the anesthesiologist wisely: check around if you don’t know much about the gas man who will be assigned your case. I always set that up weeks in advance, but I have an “in” to do that.

1 Like