Thursday, September 09, 2010

Operating Better, With Electricity!

Sharp knives. Sutures. Hot lights and warm blood. Great music. That's what most folks picture when thinking about operating rooms. It's easy to overlook that we make use of plain old electrical energy in the OR --- electrosurgery. Sounds like something from a '50s SciFi novel. Perhaps a gift from the Red Lectroids from the 8th dimension?

Actually, the modern era of electrosurgery started in 1926, courtesy of Dr. William Bovie, a physicist, and Dr. Harvey Cushing, the father of neurosurgery in the US. The term "Bovie" is still standard jargon for the electrosurgical generator used in surgery, though most surgeons are only casually aware of its origins (there is a fair amount of history here and here, for those interested; image from Medscape). Me? Back in the dark ages, when (general, non-GYN) laparoscopic surgery was undergoing rapid growth and research opportunities abounded, I spent a year doing research, teaching laparoscopic surgery courses, and writing papers & book chapters. There had been considerable debate about the relative merits of using laser energy versus electrosurgery in laparoscopic gallbladder removal, and I landed the plum job of writing one of the papers that helped relegate laser laparoscopic cholecystectomy to the dustbin. Of course, as these things go, I also had many more writing assignments, including a book chapter entitled "Endoscopic Technology" for a book about laparoscopic and endoscopic surgery.

Let's just say, for someone who struggled to remember everything his father taught him about wiring a house, I learned quite a bit about electricity to write that chapter. And I learned even more about the potential for patient safety problems when using electrosurgery. For simplicity, though, the best way to think about electrosurgery is to picture a complete electrical circuit (image source):

Any interruption in the circuit results in cessation of the flow of electrical energy (electrons). In the operating room, the "battery" is the electrosurgical generator, and rather than lighting a lamp, the energy is focused in the tip of an instrument, resulting in heat and tissue destruction, also called diathermy, where it is focused.

OK, wait a minute. The generator is connected to the instrument, which is supposed to deliver electrical energy. But that doesn't make a complete circuit --- where is the rest of the circuit connecting back to the generator?

Well, a big chunk of the circuit is made, just like Soylent Green, of people! More accurately, of one person -- the patient --, to whom is attached a grounding pad (the passive electrode) that then connects back to the generator. Voila! A complete circuit is made, allowing high current density produced at the tip of the instrument (the active electrode) to cut and cauterize tissue.

So what's different about using electrosurgery in laparoscopy? Well, a couple of things. First, we must use long instruments to reach the operative field, with an active electrode only at the tip of some of them. Second, those instruments must pass through trocars that maintain a seal to prevent the escape of CO2 from the inflated abdomen. And finally, we use a non-insulated telescope attached to a video camera to view what is happening in the operative field. As a result, there are many places where electricity may end up flowing other than where it is intended to be focused. If the active electrode/cautery tip is activated against an uninsulated portion of another instrument, tissue that is in contact with that instrument can be injured. If the cautery tip is activated out of view of the camera, it can result in unrecognized tissue injury. And there is a more complex problem called capacitive coupling, unique to laparoscopic surgery, that can result in tissue injury.

Perhaps the most pernicious risk, however, is insulation failure. Because we want action only at the tip of the active electrode, the remainder of the length of the instrument is insulated to prevent "leakage" of electricity ---- which can cause a tissue burn when the shaft of the instrument is laying against, for example, a piece of bowel, well out of view of the operative field. That risk, I have always felt, can be eliminated by using disposable rather than reusable cautery instruments. Additionally, the other instruments not actively delivering electrical injury may have insulation defects, and can similarly cause injury if they are used in contact with the active electrode/cautery.

Looks like I may be right for a change --- Insulation failure in laparoscopic instruments is a study published in Surgical Endoscopy earlier this year (unfortunately no unregistered access to article or abstract). Basically, the authors looked at reusable and disposable laparoscopic instruments used to deliver electrical energy and tested them for insulation defects. From the abstract:
Two hundred twenty-six laparoscopic instruments were tested (165 reusable). Insulation failure occurred more often in reusable (19%; 31/165) than in disposable instruments (3%; 2/61; p less than 0.01). When reusable sets were evaluated, 71% (12/17) were found to have at least one instrument with insulation failure. Insulation failure incidence in reusable instruments was similar between hospitals that routinely checked for insulation failure (19%; 25/130) and hospitals that do not routinely check for insulation failures (33%; 7/21; p = 0.16). Insulation failure was most common in the distal third of the instruments (54%; 25/46) compared to the middle or proximal third of the instruments (p less than 0.05).
Hmmm. One in five reusable instruments was found to have an insulation failure. Cue The Doors:
Five to one, baby
One in five
No one here gets out alive, now
You get yours, baby
I'll get mine
Gonna make it, baby
If we try

Hold on. If this was a humongous problem, wouldn't general surgeons be seeing electrosurgical injuries from laparoscopic surgery on a weekly basis? Yep. And we don't. Perversely, I would say that is a bit of an issue ---- because this is seen very rarely, it is something about which one may be less than vigilant.

From my standpoint, I have a few things I insist upon when doing laparoscopic surgery; most importantly, I will only use disposable cautery instruments, as they are heavily used and most prone to insulation failure. Secondly, I don't use any other instruments to help deliver electrical energy/cautery; in open surgery, we frequently pick up a small bleeding vessel with a pair of forceps and then deliver the cautery against the forceps, delivering the electricity through them to the tissue that they hold --- for me, an absolute never in laparoscopic surgery. Finally, when appropriate I use alternate methods of delivering energy to tissues --- bipolar electrosurgery (that's another post) or high frequency ultrasonic energy most commonly.

In the end, the problem associated with insulation failure is really no different than many other potential pitfalls in medicine --- being well aware of the potential problem is the best method of its prevention.