Editing Electrosurgery


== '''Goals:''' ==

* Limited thermal damage to target tissue only
* Adequate haemostasis
* Tissue cutting/vaporisation/transection

== '''Theory:''' ==

* Current = flow of electrons per time (amperes)
* Voltage = force pushing current through the resistance (volts)
* Impedance/resistance = obstacle to the flow of current, measured in ohms
** Impedance and resistance are essentially the same - impedance is for AC circuits, while resistance is for DC circuits. I suspect any difference between them is beyond the scope of what surgeons need to know.
* Technically, we almost always use electrosurgery (AC) as opposed to electrocautery (DC). In AC circuits, the patient is included in the circuit.

== '''Tissue manipulation:''' ==

* Cut = continuous waveform which produces heat rapidly and vaporises tissue
** Hold electrode slightly away from tissue to focus heat
* Blend 1-3: progressive decrease in the 'duty cycle' length, causing a gradual change from cut to coag. Blend 1 is close to 'cut', while blend 3 is close to 'coag'.
* Coag = higher voltage, shorter bursts. Produces a coagulum instead of vaporising.
* The only variable which determines whether one waveform vaporises tissue and another produces a coagulum, is the rate at which heat is produced.
* Dessication occurs when the instrument is held directly against a vessel - lower temp, dries and denatures and forms thrombus. Note that this is normally achieved using a forceps.
* Fulguration - superficial coagulation over a wide area - achieved by applying energy without making tissue contact
* Electrovaporisation
** E.g. Prostate ablation



== '''Monopolar:''' ==

* Alternating current utilising a completed circuit from the instrument, through the patient, to the return electrode, to the machine, and back to the instrument
* Impedance causes heating. Impedance increases with resistance (impedance is technically '''resistance''' plus '''reactance''' in AC circuits - I am using impedance in this topic)
** Impedance can be increased by removing fluid, compressing arteries or putting tissue under tension.
*** Fluid conducts, and so reduces impedance, and since heat produced is proportional to impedance - fluid prevents heating
** Increasing the length of time also obviously increases thermal change
** Hence the mnemonic of how to increase thermal change at a point: 
*** A - first decrease the AREA of contact
**** Pad is high area, low impedance, low current = low heating
**** Electrode is low area, high impedance, high current = intense heating
*** R - second increase tissue RESISTANCE/IMPEDANCE
*** T - third increase TIME
*** Current/wattage can also be increased, but this should come last - it increases the risk of unwanted thermal change
* Risk of electrocution is low when AC < 100khZ is used. Monopolar is higher frequency (300-3800kHz)
* Selecting wattage
** Should be as low as possible to accomplish the task
** 20W is low - forces you to use the ART acronym
** Be aware that carbonisation occurs at 200-400 degrees - this should be avoided where possible - hallmark of non-refined technique

== '''Bipolar''' (allows the application of both electrodes on the target tissue): ==

* Tissue sealing and haemostasis is achieved by compression of tissue and local delivery of RF energy, resulting in thermal change
* Compression is important - prevents continued flow of blood, which can act as a heat-sink. Don't compress too much, or the tissue will be bypassed.
* Safer on pedicled structures
* Minimal tissue damage
* No possibility of return electrode burns/alternate site burns/capacitive coupling/insulation failure
* Can get stuck to coagulated tissue - one option is to reactivate underwater, which can create steam and often dislodge, rather than just pulling off

== Ligasure ==

* Maryland - available 23, 37 and 44cm
* Blunt tip - 23, 37, 44cm
* Curved small jaw open sealer/divider (I think this is the open one for thyroids)


== '''Argon beam coagulation:''' ==

* Spray ionised argon onto surface and it causes coagulation and fulgaration as it is sprayed onto surface
* Blows away blood and fluid as it applies to surface
* Thinner, more flexible eschar
* Good in radiation proctitis bleeding for example
* Be aware - instillation of gas into a closed cavity can increase pressure - should leave a port open
* Risk of gas instillation into open vein - air embolism

== '''Hazards:''' ==

* Hazards to patient 
** Hazards with careless use
*** Narrow pedicles can create higher current densities = ischaemia
**** Avoid by using bipolar instead of monopolar
*** Ignition - alcohol, anaesthetic gases, manitol, bowel prep
*** Inadvertent activation
*** Activation of PPM
**** Use magnet
**** Avoid monopolar
*** Internal defibrillators should be deactivated prior to OT and reactivated after
*** Direct coupling
**** Don't activate close to other laparoscopic instruments
**** Be very careful around staple lines or other small bits of metal
**** Be aware of arcing - may represent subtle failure of insulation
** Hazards with careful use
*** Return plate burns
**** Surface area reduced - excessive hair, adipose tissue, bony prominences, fluid invasion, adhesive failure, scar tissure
**** For best results, choose a well-vascularised muscle mass, close to operative site
*** Neuromuscular stimulation
*** Insulation failure
*** Capacitive coupling
* Hazards to operative staff
** Noxious gases
** Burns

== If not working ==

* Check all connections
* Patient/plate contact
* Generator settings
* Replace probe
* Replace machine

[[Category:Operating theatre]]