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Bipolar diathermy

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30/08/2006

Diathermy

  • Diathermy is the use of high frequency electric current to produce heat
  • Used to cut/vaporise tissue or to produce coagulation
  • Electrical frequency is in the range of 300 kHz to 3 MHz (mains electricity is 50 Hz) 
  • Patients body forms part of the electrical circuit
  • Current has no effect on muscles

Monopolar diathermy

  • Electrical plate is placed on patient and acts as indifferent electrode
  • Current passes between instrument and indifferent electrode
  • As surface area of instrument is an order of magnitude less than that of the plate
  • Localised heating is produced at tip of instrument
  • Minimal heating effect produced at indifferent electrode

Bipolar diathermy

  • Two electrodes are combined in the instrument (e.g. forceps)
  • Current passes between tips and not through patient
  • Provided that you do not create a capacitor, bipolar is the safest for laparoscopic surgery

When electrosurgery is used in the context of minimally invasive surgery, it raises a new set of safety concerns.  These include: insulation failure, direct coupling of current and capacitively coupled current.

A capacitor is created/occurs whenever a nonconductor separates two conductors.  During laparoscopic procedures, an “inadvertent capacitor” may be created by the surgical instrumentation.  In the normal sequence of events, the conductive active electrode is surrounded by nonconductive insulation.  This, in turn, is in many instances surrounded by a conductive metal cannula.  A capacitor creates an electrostatic field between the two conductors and as a result, a current in one conductor can, through the electrostatic field, induce a current in the second conductor.

Capacitance cannot be entirely eliminated with a plastic cannula. The patient’s conductive tissue completes the definition of a capacitor. Capacitance is reduced, but is not eliminated.

The worst case scenario occurs when a metal cannula is held in place by a plastic anchor. The metal cannula still creates a capacitor with the active electrode.  However, the plastic abdominal wall anchor prevents the current from dissipating through the abdominal wall. The capacitively coupled current may exit to adjacent tissue on its way to the patient return electrode eg bowel. This can cause significant injury.

Most potential problems can be avoided by following these simple guidelines:

  • Inspect insulation carefully
  • Use lowest possible power setting
  • Use a low voltage waveform (cut)
  • Use brief intermittent activation vs. prolonged activation
  • Do not activate in open circuit
  • Do not activate in close proximity or direct contact with another instrument
  • Use bipolar electrosurgery when appropriate
  • Do not use hybrid cannula systems that mix metal with plastic.

Laparoscopic Bipolar Dissection

MicroFrance

BLA have used MicroFrance bipolar forceps with great success for conducting radical prostatectomy and nephrectomy over a number of years.  They are also very useful for appendicectomy (dividing the appendix mesentery).  There are two types available

Reusable

  • Flat forceps eg Manhes fine dissecting forceps CM131 (see below).  Whilst these are favored by gynaecologists, in our experience they tend to get stuck to the coagulated tissue and are hard to remove.  This can be a problem when used to divide blood vessels.


  •  BLAs preference has been to use fenestrated forceps and in particular the CEV634-1A Mouiel forceps (see below)

An alternative is shorter, stubbier Botella forceps



The fenestrated model has been a very reliable and effective tool (cuts tissue and seals vessels) and their reusability makes them a much cheaper alternative than other energy sources which are more widely advertised eg Harmonic

They work using any bipolar diathermy lead connection and any standard electrical generator.  We have used them in over 350 radical prostatectomies and nephrectomies without the need for a replacement (see below).   In one of our hospitals we have a pair that always seem to be "at the menders".  They are of course now over five years old! 

We would have used them in our colorectal work if our NHS Trust had invested in the product 10 years ago.  What a saving that would have been!

MicroFrance instruments and diathermy are distributed throughout the UK by:

Surgical Instrument Group Holdings Ltd
89A Gloucester Road
Croydon
Surrey
CRO 2DN

Tel:      0845 310 1103
Fax:     0208 683 1105
Email:  info@sighltd.com

SIGH provide a "healthcheck" of the insulation and integrity of their bipolar forceps and cables - hospitals must check on these after every 50 autoclavings.  They collect & return the forceps & cables free of charge.  Instruments are reinsulated and cables replaced as necessary.  The instrumentation is warranted for 300 autoclave cycles.

 

Disposable bipolar instruments

Ethicon Endopath

Ethicon produce a 5mm disposable bipolar forceps (EBF01).  Whilst this instrument will work with any electrical generator, it does require the additional purchase of its' own Ethicon Endopath specific lead or "flying banana".  As these need to be autoclaved between cases and can easily be dropped you will need two.  Whilst they are popular with gynaecologists, they have non-fenestrated tips which in our experience tend to stick to tissue.

Gyrus - PK bipolar system 

Gyrus (well known in urology and gynaecology circles for their TURP electrosurgical systems and bipolar forceps) has recently introduced a new laparoscopic system - PlasmaCision.  "The only technology to offer rapid simultaneous seal and cut". 

They claim that it is dependable, precise and achieves consistent vessel coagulation and sealing with minimal sticking of the tissues to the instrumentation.  This is due in part to a reduced coagulum developing.  Their system includes pulse-off periods allowing tissue to cool (instruments also have gold plated jaws to allow rapid cooling) as well as for moisture to return to the targeted area. 

You can use the instrumentation (33cm 5mm PKS Plasma Trissector - Order# 940010PC - list price £350) to dissect and mobilise tissue.  Price is negotiable and is based on unit usage; it can work out substantially cheaper than Harmonic.  Our current purchase price is £257.  They also produce a J-Hook (#956010PC - for £ 150) and standard bipolar scissors (#960000PK).  Both instruments come in 33 and 45cm lengths.  Their system is similar to ultrasonic dissectors in that it produces an audible tone to let the surgeon know when the tissue is desiccated or when shorting is occurring.

We have used the J-Hook to good effect in performing a TME anterior resection in a man with a BMI of 55!  I don't think that we could have done that with our usual Harmonic.  It also proved effective in undertaking an extended right hemicolectomy (Haem-o-Lok for the vessels).  In both cases there was no charring.  It was particularly useful in dissecting anterior to the pancreas and taking down the splenic flexure.  It is well worth a trial and clearly has major financial implications over alternative systems.  We have not compared it with the Lotus hook.

To be honest I was not too impressed by their original Trissector.  It produced an awful lot of vapor and it was not particularly good at dividing the peritoneum.  It did however cut through the ICA/V with surprisingly good effect.  Whilst it might not be as hot as Harmonic, it does get very hot!  Gyrus have been tinkering with the generator settings and when we used the new Trissector for a laparoscopic dissection of the rectovaginal septum I was well impressed.  It was much better than Harmonic and the cheeper alternative the ordinary J hook.

Gyrus are keen for surgeons to evaluate their PK system (Link provided - see above).  It is certainly worth a trial, particularly the Hook before embarking on purchasing an ultrasound dissecting system.  If you have an aversion to Orange - it is best avoided!

The electrical generator is provided Gyrus on longterm loan free of charge - a potential £12,000 saving on Harmonic if you like it.  They also undertake to service and repair it free of charge.
 
Contact details:

Gyrus International Ltd.
410 Wharfedale Road
Winnersh Triangle
Berkshire RG41 5RA

Phone: 44 (0) 1189.219700
Fax: 44 (0) 1189.219800

0r contact  simon.angove@gyrusacmi.com  



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