EBME Forums Forums Maintenance Technical Assistance Using two electrosurgerys simultaneously

Has anyone come accross a situation where two surgical teams use two diathermies simultaneously on one patient? Apart from the obvious risks e.g. current cross-over, what are other forseen dangers and why should such practice be ovoided? Any documents relating to this practice would be useful.

Yes it is quite common in cardiac by-pass surgery. One team on the chest and another on the leg, harvesting a vein.
With modern floating diathermies there is not a real problem, the old earth referenced ones caused major issues.
Robert

Yes. I believe it's quite a common practice. And I have seen some literature (article) about it somewhere. Positioning of the return plates are important, of course (but there again it always is).

Try Google!

Regarding any risk to the patient (real or imagined) ... bear in mind that s/he is already undergoing (what is probably "major") surgery, under a general anaesthetic etc. - just to keep things in perspective.

Yes its very common. We have been doing it for 10+ years in our cardiac theatres. Using 2 x force FX's (one for chest, one for harvesting)

In later years we have purchased ERBE VIO300's as they have a different way of dealing with simultaneous coag.

What does the manual say?

During a previous job, the question was asked whether it was acceptable practice. The device manual said that it was acceptable, although it specifically said to not connect the units via an equipotential cable.

Contrary to this, an apparent expert within the organisation said that it should not be done, although the basis of his argument (and dismissal of the manufacturer's documentation) was that "we don't know where currents will go".

As Geoff said, return plate positioning is important, even with a single unit. Bearing in mind that current density is the underlying process by which electrosurgery is achieved, one should be aiming to avoid return current passing through thin areas of flesh.

And of course, current follows the path of least resistance.

Which currents were your local expert thinking of there, I wonder?

We need to distinguish here between the intentional output (cutting etc.) from the ESU(s) and any extraneous "by-products" concerning leakage currents, earth loops and what-have-you which could (and probably will, at least at the micro-amp level) occur as a result of having two ESU's blazing away at the same time.

Either way, the "currents" will go where all currents end up - down the drain to earth somewhere. I suppose that the guy was worried about the paths they might follow within the patient's body. Again, that's what careful positioning of the return plate (two in the case being discussed) is all about. As well as that of the patient himself, of course (hopefully he hasn't got an arm hanging over the table, dangling into a puddle on the floor - or touching metal on the table, etc., etc.).

To cover all the bases, we should also need to wonder about the earthing (actual, and relative to each other) of any or all other equipment in use nearby.

But - as I have already hinted at - that second group (leakage currents et al) may be considered negligible when compared with the active (working) current; and an "acceptable risk" when set against what the surgeon is trying to achieve.

Meanwhile:- yes, as always, Ohm's Law (and those of all his mates) applies. So yes (just as water always seeks its own level), current will always follow the path of least resistance. You can trust me on that one!

To be honest, I've never really liked them. They're just another complication (and point of confusion) as far as I'm concerned. And in certain scenarios they can effectively pass (share) leakage currents from faulty equipment to non-faulty kit, with (possibly) unwelcome consequences! Touch Currents, Risk Currents ... call them what you will.

Does anyone have a good word for them? Equipotential Points (and cables), that is.

The only place I've ever found them useful was as an expedient in [censored] conditions where (for example) an ECG recorder could be strapped to a heating radiator to gain an earth (that is, in circumstances where the mains supply lacked a proper earth).

IMHO a decent (proper) earth connection via the protective earth conductor of the mains cable on each piece of equipment is all that is ever required.

You only really need these in the USA* where their standard mains power supply is frightening to those used to the (over the top) UK standards. Why do you need a "medical grade" plug? Because standard ones are not good enough.
Robert

* And possibly other places that follow their practice (But I expect some travellers abroad can name worse)

And back to the topic........
It is common practice to use two diathermies on one patient as long as you take some sensible precautions such as placing he pads near the area being cut.
Your know-it-all doesn't.
Robert

A quick side step:-

1) I think you'll find that the "Equipotential Terminal" saga was a European "initiative" (possibly even DIN). Its scope goes beyond just electromedical equipment, but also includes all exposed conductive surfaces with the "patient environment". The idea being to peg all exposed metal down to to a single local "earth" (for want of a better word). The bit I'm not too keen on is the "daisy chain" (or perhaps snowflake) circuit that can arise. Electrical safety purists might argue that they have a valid use in "cardiac" situations, in that they pin down equipment (so connected) to zero volts potential difference enclosure to enclosure. But do they? What would the PD between kit at the farthest points on the "daisy chain" be, assuming that there was indeed a bit of leakage current passing along the equipotential cabling? And are we actually hoping to achieve a zero volts situation (I have seen various micro-voltage allowances mentioned over the years)? Perhaps I had better leave it to others to debate the finer points of a few micro-amps floating around here or there.

2) The US "Hospital Grade" plugs are good quality; the design ensures that they have a nice (snug) fit into the wall outlet. But ... (as I may have mentioned before) their down-side is that *they direct the cable (sticking) out at right-angles to the wall outlet. That is, rather than pointing the cable "down the wall" (as the standard UK mains plug does). Not only does this result in the plug "sagging" at the outlet (due to the weight of the cable), but also introduces a trip hazard (not to mention something else for passing carts to smash into). In short, the Law of Unintended Consequences rears its head once again. Or (if I was feeling unkind):- a design defect! Unless, of course, the idea behind it was (is) to allow the cable to be used to readily yank the plug out of the wall outlet (or "cord", plug and "receptacle" in US parlance).

3) Yes; I could name "far worse" (but won't, as no doubt we can all guess where they're likely to be):- places where the concept of the need for an electrical "earth" is not readily understood, shall we say. Or others where the "earth" is actually tied to the centre tap of a supply transformer (and therefore likely to be about half way between - what we might call - Live and Neutral) ... yes, there are places like that. The UK system is not OTT. It just happens to be the best! And that's why we don't want it watered down by ever more Euro mumbo-jumbo (that seeks to "harmonize" by aiming towards the Lowest Common Denominator).

* The ubiquitous, original and traditional version, that is.