What is a Watt? What is a Watt? Everything you ever Everything you ever wanted to know about wanted to know about Electrosurgery.Electrosurgery.

Fahad bamehriz, MDFahad bamehriz, MD

HistoryHistory

Benjamin Franklin: 18th Century-first experimentsBenjamin Franklin: 18th Century-first experiments Arsene D'Arsonval: first to experiment with alternating

currents in the late 19th century• first to study clinical effects with modulated and

non-modulated current Beer 1910: First endoscopic use of

electrosurgery• Fulguration of bladder tumours using the

cystoscope Bovie and Cushing 1928: first electrosurgical

generator with continuous sinewave current

Fundamentals of Fundamentals of ElectricityElectricity

Electricity is electrons freed from atomsElectricity is electrons freed from atoms Current <I> is electrons flowing in the Current <I> is electrons flowing in the

same direction (measured in amperes)same direction (measured in amperes)• flow from negative to positive terminalflow from negative to positive terminal

Voltage <V> is the electromotive force to Voltage <V> is the electromotive force to drive the current through the conductordrive the current through the conductor• difference in potential between the polesdifference in potential between the poles

Current that is one-way is direct current Current that is one-way is direct current <DC><DC>

Fundamentals of Fundamentals of ElectricityElectricity

Current that reverses direction is Current that reverses direction is alternating <AC>alternating <AC>• The movement of electrons reverses direction The movement of electrons reverses direction

at regular intervals <cycles per at regular intervals <cycles per second=hertz>second=hertz>

Resistance <R> is the difficulty that a Resistance <R> is the difficulty that a material presents to the flow of electricity material presents to the flow of electricity <ohms><ohms>• WATER IS THE KEY FOR TISSUESWATER IS THE KEY FOR TISSUES• More water less resistanceMore water less resistance

Fundamentals of Fundamentals of ElectricityElectricity

High School Physics:High School Physics: Ohm’s Law: V=I X ROhm’s Law: V=I X R Power is the rate of doing work <watts>Power is the rate of doing work <watts> W=I X VW=I X V W=IW=I22 X R X R W=VW=V22/R/R Total quantity of electrons moved and Total quantity of electrons moved and

the pressure gradient against which the the pressure gradient against which the movement occurredmovement occurred

Alternating CurrentAlternating Current

Household power: 60 cycles/sHousehold power: 60 cycles/s AM Radio: 550-1600 kHzAM Radio: 550-1600 kHz Electrosurgical generators: 500-3000 Electrosurgical generators: 500-3000

kHz kHz

Current WaveformsCurrent Waveforms

Modulated current is just interrupted Modulated current is just interrupted currentcurrent• this is the COAG buttonthis is the COAG button• highest peak to peak voltagehighest peak to peak voltage

Non-modulated current is a continuous Non-modulated current is a continuous sinewavesinewave• this is the CUT buttonthis is the CUT button• low peak to peak voltagelow peak to peak voltage

Current WaveformsCurrent Waveforms

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"CUT"

"COAG" "RETURN"

ESUBlend 1

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Fulguration - "Coag"

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WATTS

Frequency 500,000 Hz

Frequency 500,000 Hz

Frequency 500,000 Hz

Frequency 500,000 HzFrequency 500,000 Hz

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M.G.Munro M.D.

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ESUBlend 1

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Fulguration - "Coag"

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WATTS

Frequency 500,000 Hz

Frequency 500,000 Hz

Frequency 500,000 Hz

Frequency 500,000 HzFrequency 500,000 Hz

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Cellular EffectsCellular Effects

Vaporization (cutting):Vaporization (cutting):• rapid oscillation of cell positive and negative rapid oscillation of cell positive and negative

ions causing high temperatures (600 °c) and ions causing high temperatures (600 °c) and converting mechanical energy to thermal converting mechanical energy to thermal energy.energy.

• Cell expansion and steam formation lead to cell Cell expansion and steam formation lead to cell explosionexplosion

Dessication/Coagulation:Dessication/Coagulation:• slower process with temperatures at 70-100 °c slower process with temperatures at 70-100 °c

and evaporation of intracellular water and and evaporation of intracellular water and protein denaturationprotein denaturation

Cellular EffectsCellular Effects

M.G.Munro M.D.

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H 02

H 02

H 02H 02

H 02

H 02

LOW POWER DENSITYDesiccation/ Coagulation

HIGH POWER DENSITYVaporization/ Cutting

Cellular EffectsCellular Effects

Fulguration: Superficial coagulation of Fulguration: Superficial coagulation of broad tissue surface using electrical arcs broad tissue surface using electrical arcs of high voltage of modulated currentof high voltage of modulated current

rapid desiccation and tissue resistance rapid desiccation and tissue resistance limits current flowlimits current flow

the only really good reason to use the only really good reason to use modulated currentmodulated current

Cellular EffectsCellular Effects

Cautery: destruction of tissue by the Cautery: destruction of tissue by the application of heat or a caustic application of heat or a caustic substancesubstance• ie: grasping tissue with pickups and ie: grasping tissue with pickups and

touching pickups with active electrodetouching pickups with active electrode

CapacitanceCapacitance

Property of an electrical circuit to store Property of an electrical circuit to store energyenergy

Capacitor=any device that can create Capacitor=any device that can create capacitancecapacitance• exists when two conductors with different exists when two conductors with different

potentials are separated by an insulatorpotentials are separated by an insulator• the difference between them creates an the difference between them creates an

electrostatic forceelectrostatic force• capacitance is directly proportional to voltagecapacitance is directly proportional to voltage

OR CapacitorsOR Capacitors

SurgeonsSurgeons Pts’ jewelryPts’ jewelry OR tableOR table IV poleIV pole idle electrodeidle electrode surgical instrumentssurgical instruments

• induced currents may lead to alternate induced currents may lead to alternate current pathways back to groundcurrent pathways back to ground

• surface area key…small is badsurface area key…small is bad

GroundingGrounding

A form of conductive connection between A form of conductive connection between a circuit and eartha circuit and earth

earth can absorb infinite electrical chargesearth can absorb infinite electrical charges equalization occursequalization occurs Risk of alternate site burns (EKG Risk of alternate site burns (EKG

electrode) eliminated by dispersive return electrode) eliminated by dispersive return electrode (blue pad)electrode (blue pad)• low impedance route back homelow impedance route back home• remember hair, scar and fat freeremember hair, scar and fat free

Dispersive (return) Dispersive (return) Electrode InjuryElectrode Injury

Return ElectrodeReturn Electrode

Modern generators have alarmsModern generators have alarms place in a non-dependent areaplace in a non-dependent area area with good blood flow (water area with good blood flow (water

concept)concept) *****if the generator doesn’t work: *****if the generator doesn’t work:

check return electrode**********check return electrode********** DO NOT TURN UP THE GENERATOR!!!DO NOT TURN UP THE GENERATOR!!!

Direct CouplingDirect Coupling

Activated electrode unintentionally Activated electrode unintentionally touches another metal objecttouches another metal object

may be out of the field of viewmay be out of the field of view may be undetectedmay be undetected avoided by staying aware of location of avoided by staying aware of location of

all instrumentsall instruments

Direct CouplingDirect Coupling

Capacitive CouplingCapacitive Coupling

Induction of stray current to surrounding Induction of stray current to surrounding capacitor through insulation of active capacitor through insulation of active electrodeelectrode• active monopolar electrode, insulation, metal active monopolar electrode, insulation, metal

cannulacannula• worse with higher voltage, smaller cannulas, worse with higher voltage, smaller cannulas,

longer electrodeslonger electrodes Minimize by using a Non-modulated Minimize by using a Non-modulated

(cutting) current(cutting) current Avoid hybrid (metal and plastic cannulas)Avoid hybrid (metal and plastic cannulas)

Capacitative Capacitative CouplingCoupling

Insulation FailureInsulation Failure

Insulation can be damaged by very high Insulation can be damaged by very high currentscurrents

Breaks and holes can be caused by Breaks and holes can be caused by cannula valves or cleaningcannula valves or cleaning

If defective spot on active electrode If defective spot on active electrode touches tissue, damage may occurtouches tissue, damage may occur

inspect instruments for damageinspect instruments for damage

Current DensityCurrent Density

Electrons congregate on edgesElectrons congregate on edges determined by shape and size of determined by shape and size of

electrodeelectrode same device may be multifunctionalsame device may be multifunctional

• i.e. flat vs. sharp edge of spatula electrodei.e. flat vs. sharp edge of spatula electrode important for loop excisions, important for loop excisions,

hysteroscopy and of course hysteroscopy and of course laparoscopylaparoscopy

Bipolar ElectrosurgeryBipolar Electrosurgery

Active and return electrode are on the Active and return electrode are on the instrument togetherinstrument together

eliminates risk of capacitive coupling and eliminates risk of capacitive coupling and alternate current pathwaysalternate current pathways

lower power requirements needed lower power requirements needed secondary to high concentration of secondary to high concentration of current between the polescurrent between the poles

So…..use unmodulated current with low So…..use unmodulated current with low peak to peak voltagepeak to peak voltage

Therefore, only dessication and Therefore, only dessication and coagulation possiblecoagulation possible

Bipolar ElectrosurgeryBipolar Electrosurgery

Able to grasp and compress blood Able to grasp and compress blood vesselsvessels

Able to dessicate tissue that is Able to dessicate tissue that is immersed in fluid immersed in fluid

Limited to small “bites of tissue”, large Limited to small “bites of tissue”, large pedicles not idealpedicles not ideal

May have increased thermal spread May have increased thermal spread than monopolarthan monopolar

Bipolar CurrentBipolar Current

ESU

25WATTS

Bipolar

AMMETER

0 105

ConclusionsConclusions

Keep active electrode clean, carbon Keep active electrode clean, carbon impedes current flowimpedes current flow

Know your instruments!!!Know your instruments!!! Remember Ohm’s lawRemember Ohm’s law Think :-)Think :-)