EBME Forums Forums Maintenance Technical Assistance duel diathermy operating

I have just found out a theatre has been operating using two ESU's at the same time with no problems far a long time but a sales rep has advised they should'nt be operating like this.
Can any of you advise me if this is a safe working practice or not? They are using 2 return plates placed on the same limb and both working in the same area. Dave

Dave are they fighting with the diathermies? (Dual/duel)
It depends on the make and type of machine whether there is a problem or not. Most modern machines have an isolated floating output so you can use two at once. I used to work in a cardiac hospital where they did it all the time harvesting a vein at one end and puting in as a by-pass graft at the other. But we chose our machines (Tyco Vally Lab Force-FX) with this in mind.
It is recommended that the plates for each machine be put near the area of use to ensure the current paths do not cross.
Robert

Robert,
Probably some good scientific reason for not crossing current paths.

DD,
Where 2 surgeons want to operate surgical diathermy simultaneously, we have bought valleylabs with 2 outputs. Seems like the safest option and also saves money on patient plates.

I think that the 'crossing of currents', from single channel units that Rojo refers to, means that a proportion or all the RF currents from each active would be returned via the the other unit's neutral plate since the neutrals would be common RF returns both connnected to the patient. I suppose the RF active currents would have to be compatible i.e. two similar single channel units being used.

Return currents in each circuit would have to be within acceptible tolerances (similar to active currents) but 'crossed current paths' might cause unexpected or less predictable return paths that might pass through tissues sensitive to heating that need to be avoided. Especially if the neutral plates are widely spaced apart and positioned at different sites.

I think the crossing return paths problem is to do with localised heating.
As the retun currents pass through the body there will be some IsquaredR heating happening. If these two paths cross, at that point there will be two lots of this heating so more likelyhood of tissue damage.
Using two similar diathermies is the best option. If you use an old one that does not have a floating output the REM monitor (or equivalent) on the new one gets very upset.
Robert

Yes, as far as I'm aware, recommendations are usually for the return path to be kept as short as possible i.e. the site of electrosurgery to neutral plate distance, hence return pathway impedance, is minimised; as is the RF current pathway within the patient. The benefit is that a lower power settings are usually required for the desired effect.

Also there's less opportunity or likelihood for RF leakage currents or even return currents to preferentially pass through lower impedance tissue (that may also be more sensitive to RF heating effects) than flow through some of the tissues between the surgical site and return circuit. A longer active to return distance may increase the opportunity for this.

My opinion is that operators should use a device specifically designed for dual operation if one is available - the functional aspects, monitoring, alarm functions and output interlocks are built-in.

Guys
When I went into theatre I found two different ESU's being used i.e.Valleylab FX and a Force two.
The patient was lying on their side with the surgeons working front and back and the return electrodes placed on the thigh, one nearer the hip and the other further down the thigh. Like yourselves I have great concern about using 2 different models and the return electrode placement. I think the higher return plate will be the more active of the two due to being closer and the leading edge of the plate could get warm!?
Will it help if the plates are turned side on, to the operating site but placed side by side?
First thing I need to do though is advise the team to use the same models at least. Next would be to trial new units with duel Coag then get them to spend some money and purcahse more approproate kit. Is there info out there in layman terms to help educate on diathermy issues?

Dave

I think first of all you should consider that the advice given on this site is the opinions of the individuals that post it and not necessarily from experts in electrosurgery. The other consideration is that nobody on this site has advised you to do anything - just made you aware of potential issues that could occur theoretically speaking.

On the issues of compatibility I was not inferring that similar electrosurgery units were compatible in the sense they should work together and be used for dual operation. Just that it may be possible for currents on two similar units to 'cross', as Rojo puts it, if the outputs are compatible i.e. can be detected/measured by each unit and a return path is completed.

However, based on what you say, I think it wouldn't do any harm to approach the sales representatives and clinical trainers from Valleylab to discuss any concerns about the use of their equipment.

If you still have concerns then perhaps you need to speak to an expert at the MHRA for advice, guidelines or recommendations concerning technical aspects of the use of electrosurgery - remember it is a clinical decision to use a device or not - the clinicians, theatre nurses/ODPs should be familiar with the equipment and be aware of what is and isn't good, bad or best practice. It's their responsibility at the end of the day, not yours, to decide what's acceptable use of equipment or not.

To partly answer your question - yes there have been publications from the MDA/MHRA on the technical and clinical aspects of electrosurgery and such things as posters highlighting best practice/responsibilities regarding electrosurgery.

All the well known manufacturers produce nice brochures about the principles of electrosurgery.

Similarly, instruction manuals for modern ESU’s mention that using two machines is often convenient or even essential. Each manufacturer lists points to be observed, but in general (as has been mentioned above) only two units of the same electrical type should be used.

I should imagine that the real danger is more from someone accidentally hitting the wrong foot-pedal!

But I must agree with Richard here. We are not (highly paid) surgeons, after all. Let’s leave the surgical decisions to them!

Hello,

Sorry for joining the decussion late!

I've taken a course in Radio Frequency Engineering and believe me electricity at high frequency can act in very peculiar ways. I've recently been involved in a question about a metal extractor inside a patient being directly connected to the theatre table, while a diathermy is used. We've reached a successful conclusion on the subject, but the issues are far from simple.

My question is should surgeons have to make decisions on issues like this. On what basis, probably a basic understanding of ohms law gained while studying for his exams as a student. Don't get me wrong surgeons are highly educated intelligent people, who make life and death decisions every day (hence their pay to account for this). We claim it's a clinical issue, but if we're honest with ourselves we know this problem is not in their field of expertise.

Maybe talking with manufacturers and people who run courses in electrical safety may point you in the right direction.

Adrian.