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Principles of Electrosurgery: Understanding Electrosurgical Waveforms and Tissue Effects
- 2. Table of Contents Properties of Electricity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Principles of Electrosurgery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Bipolar Electrosurgery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Monopolar Electrosurgery .........................................4 Tissue Effects Change as You ModifytheWaveform.....................5 Electrosurgical Tissue Effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Grounded Electrosurgical Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Isolated Electrosurgical Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Patient Return Electrodes .........................................9 Patient Return Electrode Monitoring Technology......................11 Adaptive Technologies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Radio Frequency Ablation ........................................14 Electrosurgery Safety Concerns During MIS ..........................16 Capacitive Coupling During Endoscopy ....................... ......17 Recommendations to Avoid Electrosurgical Patient Complications in MIS ...18 Coated Electrodes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 Argon-Enhanced Electrosurgery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 Surgical Smoke . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 OR Safety Precautions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 KeyTerms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
- 3. 2 Severalpropertiesofelectricitymustbeunderstoodinorderto understand electrosurgery.Electronsorbitthenucleiofatoms. Currentflowoccurswhen electronsflowfromoneatomtothe orbitofanadjacentatom.Voltageisthe âforceâ orâpushâ that provideselectronswiththeabilitytotravelfromatomto atom.If electronsencounterresistance,heatcanbeproduced.The resistance toelectron flowiscalled impedance. A completedcircuitmustbepresentinorderforelectronstoflow. A completed circuitisanintactpathwaythroughwhichelectrons cantravel.Inthisdiagram, voltageisgeneratedbythepower plant,providingthe force topushelectrons throughthe circuit. Theoriginalsourceoftheseelectronsistheearth(ground).To completethe circuittheelectronsmustreturntoground.Any groundedobjectcancomplete thecircuit,allowingtheelectrons toflowto ground. Current = flow of electrons during a period of time, measured in amperes Circuit = Pathway for the uninterrupted flow of electrons Voltage = force pushing current through the resistance, measured in volts Impedance/Obstacle to the flow of current, resistance = measured in ohms (impedance = resistance) Electrocautery Oftenâelectrocauteryâ is usedtodescribeelectrosurgery.Thisis incorrect. Electrocauteryreferstodirectcurrent(electrons flowinginonedirection) whereaselectrosurgeryuses alternatingcurrent.Duringelectrocautery, currentdoesnot enterthepatientâsbody.Onlytheheatedwirecomesin contact withtissue.Inelectrosurgery,thepatientis includedinthe circuitand current enters the patientâsbody.
- 4. 3 frequency Spectrum Standardelectricalcurrentalternatesatafrequencyof60 cycles persecond (Hz).Electrosurgical systemscouldfunctionatthis frequency,butbecause currentwouldbetransmittedthrough bodytissueat60 cycles,excessive neuromuscularstimulationand perhaps electrocution wouldresult. Becausenerveandmusclestimulationceaseat100,000 cycles/ second(100 kHz), electrosurgerycanbeperformedsafelyat âradioâfrequenciesabove100 kHz.Anelectrosurgicalgenerator takes60 cyclecurrentandincreasesthe frequencytoover 200,000 cyclespersecond.Atthisfrequencyelectrosurgical energycanpassthroughthepatientwithminimalneuromuscular stimulation andno riskof electrocution. Principles of Electrosurgery in the O.r. Principlesofelectricityarerelevantintheoperatingroom.The electrosurgical generatoristhesourceoftheelectronflowand voltage.Thecircuitiscomposed ofthegenerator,activeelectrode, patientandpatientreturnelectrode.Pathways togroundare numerousbutmayincludetheO.R.table,stirrups,staffmembers andequipment.Thepatientâstissueprovidestheimpedance, producingheatas the electronsovercome the impedance. *The circuit for the alternating current is depicted by arrows in opposite directions. Current*
- 5. 4 Bipolar Inbipolarelectrosurgery,boththeactiveelectrodeandreturn electrodefunctions areperformedatthesiteofsurgery.Thetwo tinesoftheforcepsperformthe activeandreturnelectrode functions.Onlythetissuegraspedisincludedinthe electrical circuit.Becausethereturnfunctionisperformedbyonetineofthe forceps,nopatientreturn electrode is needed. ⢠Active output and patient return functions are both accomplished at the site of surgery. ⢠Current path is confined to tissue grasped between forceps tines. ⢠Patient return electrode should not be applied for bipolar only procedures. Monopolar Monopolaristhemostcommonlyusedelectrosurgicalmodality. Thisisduetoits versatilityandclinicaleffectiveness.Inmonopolar electrosurgery,theactive electrodeisinthesurgicalsite.The patientreturnelectrodeissomewhereelseon thepatientâsbody. Thecurrentpassesthroughthepatientasitcompletesthe circuit from the activeelectrode tothe patientreturn electrode. ⢠The active electrode is in the wound. ⢠The patient return electrode is attached somewhere else on the patient. ⢠The current must flow through the patient to the patient return electrode. Active Return Current Tissue Bipolar Circuit This picture represents atypicalbipolarcircuit. Active Return
- 6. 5 Monopolar Circuit Thispicturerepresentsacommonmonopolarcircuit. There are four components tothe monopolarcircuit: ⢠generator ⢠Active Electrode ⢠Patient ⢠Patient return Electrode Electrosurgical generatorsareabletoproduceavarietyof electricalwaveforms. As waveformschange, sowillthe correspondingtissueeffects.Usinga constant waveform,like âcut,â thesurgeonisabletovaporizeorcuttissue.This waveform produces heat veryrapidly. Usinganintermittentwaveform,likeâcoagulation,âcausesthe generatorto modifythewaveformsothatthedutycycle(âonâ time)isreduced.This interruptedwaveformwillproducelessheat. Insteadoftissuevaporization,a coagulumis produced. A âblended currentâisnotamixtureofbothcuttingand coagulationcurrent butrathera modificationofthedutycycle.As yougofromBlend1 toBlend3 thedutycycleisprogressively reduced.A lowerdutycycleproduceslessheat. Consequently, Blend1 isabletovaporizetissuewithminimalhemostasis whereasBlend3 islesseffectiveatcuttingbuthasmaximum hemostasis. Theonlyvariablethatdetermineswhetheronewaveform vaporizestissueand anotherproducesa coagulumistherateat whichheatisproduced.Highheat producedrapidlycauses vaporization.Lowheatproducedmoreslowlycreatesa coagulum. Anyoneofthefivewaveformscanaccomplishbothtasksby modifyingthe variablesthatimpacttissue effect. low Voltage High Voltage Typical Example 100%on 50%on 50%off 40%on 60%off 25%on 75%off 6% on 94%off
- 7. 6 Electrosurgical Cutting Electrosurgicalcuttingdividestissuewithelectricsparksthatfocus intenseheat atthesurgicalsite.Bysparkingtotissue, thesurgeon producesmaximumcurrent concentration.Tocreatethissparkthe surgeonshouldholdtheelectrodeslightly awayfromthetissue. Thiswillproducethegreatestamountofheatoveravery short period oftime,whichresultsinvaporizationof tissue. fulguration Electrosurgical fulguration(sparkingwiththecoagulation waveform)coagulates andcharsthetissueoverawidearea. Sincethedutycycle(ontime)isonlyabout 6 percent,lessheatis produced.Theresultisthecreationofa coagulumrather than cellularvaporization.Inordertoovercomethehighimpedanceof air,the coagulationwaveformhassignificantlyhighervoltagethan thecuttingcurrent. Useofhighvoltagecoagulationcurrenthas implications duringminimally invasivesurgery. Desiccation Electrosurgical desiccationoccurswhentheelectrodeisindirect contactwiththe tissue.Desiccationisachievedmostefficiently withtheâcuttingâ current.By touchingthetissuewiththe electrode,thecurrentconcentrationisreduced.Less heatis generatedandnocuttingactionoccurs.Thecellsdryoutandform a coagulumrather thanvaporize and explode. Manysurgeonsroutinelyâcutâ withthecoagulationcurrent. Likewise,youcan coagulatewiththecuttingcurrentbyholding theelectrodeindirectcontactwith tissue. Itmaybenecessaryto adjustpowersettings andelectrodesizetoachieve thedesired surgicaleffect.Thebenefitofcoagulatingwiththecuttingcurrent is thatyouwillbeusingfarlessvoltage.Likewise,cuttingwiththe cutcurrentwill alsoaccomplishthetaskwithlessvoltage.Thisis animportant consideration duringminimally invasiveprocedures. Cut Low voltage waveform 100% duty cycle Coag High voltage waveform 6% dutycycle CoagBlendPure Cut Low Low Thermal Spread/Charring Voltage High High
- 8. 7 Variables Impacting Tissue Effect Inadditiontowaveformandpowersetting,othervariablesimpact tissueeffect. They include: Sizeoftheelectrode:Thesmallertheelectrode,thehigherthe current concentration.Consequently,thesametissueeffectcanbe achievedwitha smallerelectrode,eventhoughthepowersetting isreduced. Time:Atanygivensetting,thelongerthegeneratorisactivated, themoreheat is produced. And the greater the heat, the farther it will travel to adjacent tissue(thermal spread). Manipulationoftheelectrode:Thiscandeterminewhether vaporizationor coagulationoccurs.Thisisafunctionofcurrent densityandtheresultantheat producedwhilesparkingtotissue versus holdingthe electrode indirect contact withtissue. Type ofTissue: Tissuesvary widely in resistance. Eschar: Eschar is relatively high in resistance to current. Keeping electrodes clean and free of eschar will enhance performance by maintaining lower resistancewithinthe surgical circuit. ⢠Waveform ⢠Power Setting ⢠Size of Electrode ⢠Time ⢠Manipulation of Electrode ⢠Typeof Tissue ⢠Eschar Electrosurgical technologyhaschangeddramaticallysinceits introductioninthe 1920s. Generatorsoperatebytaking alternatingcurrentandincreasingits frequencyfrom50 or60 cycles/secondtoover200,000 cycles/second.Originally, generators usedgroundedcurrentfromawalloutlet. Itwasassumedthat once thecurrententeredthepatientâsbody,itwouldreturnto groundthroughthe patientreturnelectrode.Butelectricitywill alwaysseekthepathofleast resistance. Whentherearemany conductiveobjectstouchingthepatientand leadingtoground, thecurrentwillselectasitspathwaytogroundthemost conductiveobjectâ whichmaynotbethepatientreturnelectrode. Current concentrationatthispointmayleadtoanalternatesite burn. Active Return Alternate path to ground
- 9. Withthephenomenoncalledcurrentdivision,thecurrentmay split(ordivide) andfollowmorethanonepathtoground.The circuittogroundiscompleted whetherittravelstheintended electrosurgicalcircuittothepatientreturn electrodeortoan alternategroundreferencedsite.Patientsaretherebyexposed to theriskofalternatesiteburnsbecause(1)currentfollowsthe easiest, most conductivepath;(2)anygroundedobject,notjust thegenerator,cancomplete thecircuit;(3)thesurgical environmentoffersmanyalternativeroutestoground; (4)ifthe resistanceofthealternatepathislowenoughandthecurrent flowing togroundinthatpathissufficientlyconcentrated,an unintended burn may be produced atthealternategroundingsite. Thispictureshowsanalternatesiteburnthatoccurredwhena grounded electrosurgicalgenerator wasused witha ground-referencedECG device.TheECG electrodeprovided the pathof leastresistanceto ground. However, itdidnotdispersethecurrentovera largeenougharea.Theheat producedan alternatesiteburnundertheECG electrodedueto currentconcentration. Alternate site burn Isolated System In1968, electrosurgerywasrevolutionizedbyisolatedgenerator technology.Theisolated generatorisolatesthetherapeuticcurrent fromgroundbyreferencingitwithinthegenerator circuitry.In otherwords,inanisolatedelectrosurgicalsystem,thecircuitis completednotbythe groundbutbythegenerator.Eventhough groundedobjectsremainintheoperatingroom, electrosurgical currentfromisolatedgeneratorswillnotrecognizegrounded objectsaspathways tocompletethecircuit.Isolated electrosurgicalenergyrecognizesthepatientreturnelectrodeas thepreferred pathwaybacktothe generator. Byremovinggroundasareferenceforthecurrent,theisolated generatoreliminatesmanyofthe hazardsinherentingrounded systems,most importantly current divisionand alternate siteburns. 8
- 10. 9 Deactivated Isolated System Ifthecircuittothepatientreturnelectrodeisbroken,anisolated generatorwill deactivatethesystembecausethecurrentcannot return toits source. Generatorswithisolatedcircuitsmitigatethehazardofalternate siteburnsbut donotprotectthepatientfromreturnelectrode burns,suchasthe one shown atleft. Historically,patientreturnelectrodeburnshaveaccountedfor70 percentofthe injuriesreportedduringtheuseofelectrosurgery. Patientreturnelectrodesare notâinactiveâ orâpassive.âTheonly differencebetweentheâactiveâ electrode andthepatientreturn electrodeistheirsizeandrelativeconductivity.Thequality ofthe conductivityandcontactareaatthepad/patientinterfacemustbe maintainedtoprevent areturn electrode site injury. Padsite burn function of the Patient return Electrode Thefunctionofthepatientreturnelectrodeistoremovecurrent from the patientsafely. A return electrode burn occurs when the heat produced, over time, is not safelydissipatedbythesizeorconductivityofthe patientreturn electrode. Burn = CurrEnT X TIME ArEA
- 11. 10 Ideal return Electrode Contact with Current Dispersion Theidealpatientreturnelectrodesafelycollects currentdelivered tothepatient duringelectrosurgeryandcarriesthatcurrentaway. Toeliminatetheriskof currentconcentration,thepadshould present alargelowimpedance contact areatothe patient. Placementshouldbeonconductivetissuethatisclosetothe operativesite. Again,theonlydifferencebetweentheâactiveâ electrodeandthe patientreturn electrode istheirrelativesizeand conductivity. Concentratetheelectronsattheactiveelectrodeandhighheatis produced. Dispersethissamecurrentoveracomparativelylarge patientreturn electrode andlittleheat is produced. Dangerous return Electrode Contact with Current Concentration Ifthesurfaceareacontactbetweenthepatientandthereturn electrodeis reduced,oriftheimpedanceofthatcontactis increased,a dangerouscondition candevelop.Inthecaseof reducedcontactarea,thecurrentflowisconcentrated inasmaller area.As thecurrentconcentrationincreases,thetemperatureat the returnelectrodeincreases.Ifthetemperatureatthereturn electrodesite increasesenough,a patientburnmayresult.Surface areaimpedancecanbe compromisedbyexcessivehair,adipose tissue,bonyprominences,fluidinvasion, adhesivefailure,scar tissueandmany other variables. Assess Pad Site location Choose: Avoid: Well-vascularized muscle mass Vascular insufficiency Irregular bodycontours Bonyprominences Consider: Incision site/preparea Patientposition Other equipment onpatient Current Concentration/Density The more concentrated the energy the greater the thermodynamic effect. Low Current Concentration High Current Concentration High Current Concentration High Current Concentration
- 12. 11 return Electrode Monitoring REM⢠contactqualitymonitoringwasdevelopedtoprotect patientsfromburns duetoinadequatecontactofthereturn electrode.Padsiteburnsarecausedby decreasedcontactareaat thereturnelectrodesite.REMâ˘-equippedgenerators actively monitortheamountofimpedanceatthepatient/padinterface because thereisadirectrelationshipbetweenthisimpedanceand thecontactarea.The systemisdesignedtodeactivatethe generatorbeforeaninjurycanoccurifit detectsadangerously highlevel of impedance atthe patient/padinterface. Inordertoworkproperly,REMâ˘-equipped generatorsmustusea patient returnelectrodethatiscompatible,asdepictedinthe photoatright.Suchan electrodecanbeidentifiedbyitsâsplitâ appearanceâ thatis,ithastwo separateareasâ andaspecial plugwithacenterpin.REM⢠technologyhas beenprovensafein over 100 million procedures.
- 13. 45 35 30 10 5 0 0 1500 2000 2500 3000 3500 4000 Watt s Prostate in nonconductive solution 500 1000 Liver,muscle Bowel 25 Mesenteryomentum 20 GallBladder 15 Fat, scar,adhesions ForceFX⢠PER =98 Pegasys PER =61 Ohms Comparison in Pure Cut mode ofan Instant Response⢠generatorand a conventional generator. 12 Instant response⢠Technology Computer-controlled output is automaticallyadjusted ⢠Measures tissue impedance/resistance at the electrode contact site ⢠Provides instant response to changes in tissue impedance/resistance ⢠Produces consistent tissue effect as demonstrated by a high Power Efficiency rating (PEr)* of appoximately 98 (force fXâ˘-C) out of a possible 100 ⢠Controls maximum output voltage â Reduces capacitive couplingandvideo interference â Minimizessparking * Power Efficiency Rating (PER) is a measure of the ability of an electrosurgical generator to accurately deliver the selected power into a wide range of tissue types.
- 14. 13 Vessel Sealing Technology⢠An electrosurgicaltechnologythatcombinespressure and energy tocreatea seal . A specializedgenerator/instrumentsystemhasbeendeveloped thatis designedtoreliablysealvesselsandtissuebundlesfor surgicalligationbothin laparoscopicandopensurgery applications.Itappliesauniqueformofbipolar electrosurgeryin combinationwithoptimalpressuredeliverybytheinstruments in order tofusethe vesselwallsandcreate a permanent seal. The output is feedback-controlled so that a reliable seal is achieved in minimal timeindependentofthetypeoramountoftissueinthe jaws.The resultisreliable sealson vesselsup toand including 7 mmindiameterortissuebundleswithasingleactivation.The thermalspread issignificantlyreducedcomparedtotraditional bipolarsystemsandis comparabletoultrasoniccoagulation.The sealsiteisoftentranslucent, allowingevaluationofhemostasis priortocutting.Sealstrengthsare comparabletomechanical ligationtechniquessuchassuturesandclipsandare significantly strongerthanotherenergy-basedtechniquessuchasstandard bipolarorultrasoniccoagulation.Thesealshavebeenprovento withstand morethanthree times normal systolicblood pressure. Bipolar-typeGenerator ⢠low Voltage â 180V ⢠High Amperage â 4A ⢠Tissue response Instruments ⢠Precisely calibrated ⢠High pressure ⢠Open/laparoscopic System Operation ⢠Applies optimal pressure to vessel/tissue bundle ⢠Energy delivery cycle: - Measures initial resistance of tissue and chooses appropriate energysettings - Delivers pulsed energy withcontinuous feedback control Âť Pulses adapt as the cycle progresses - Senses that tissue response is complete and stops the cycle Step1 Step2 Step3 ⢠reliable, consistent permanent vessel wall fusion ⢠Minimal thermal spread ⢠reduced sticking and charring ⢠Seal strength higher than other energy- based techniques ⢠Seal strengths comparable to existing mechanical-based techniques
- 15. 14 radiofrequency Ablation System Alternatingcurrentthroughthetissuecreatesfrictionona molecularlevel. Increasedintracellulartemperaturegenerates localizedinterstitialheating.At temperaturesabove60 degrees centigrade,cellularproteinsrapidlydenature andcoagulate, resultingina lesion. How itworks TheValleylabâ˘RFAblationSystemwithCool-tip⢠Technology generatorâs feedbackalgorithmsensestissueimpedanceand automaticallydeliversthe optimumamountofradiofrequency energy.A uniqueelectrodedesign eliminatestissuecharringand allowsformaximumcurrentdelivery,resultingin alargerablation zoneinless time. Pretreatment* CT scanof4 cm hepatoma Post-treatmentwithValleylab⢠RFA System* CT scanonsix-month follow-up * See SNGoldberg in Bibliography
- 16. 15 Cool-tip⢠Ablation Thesystemâsgeneratorsoftwaremonitorstissueimpedanceand adjuststheoutputaccordingly. Pulsedenergydeliveryallowsthe targettissuetostabilize,reducingtissueimpedanceincreases that couldlimitRFoutput.Typical treatments are completed ina 12-minutecycle. The Cooling Effect Theelectrodeâsinternalcirculationofwatercoolsthetissue adjacenttotheexposedelectrode, maintaininglowimpedance duringthetreatmentcycle.Lowimpedancepermitsmaximum energy depositionfor alargerablation volume.
- 17. 16 Whenelectrosurgeryisusedinthecontextofminimallyinvasive surgery,itraises anewsetofsafetyconcerns.Someoftheseare: insulationfailure,direct couplingofcurrentandcapacitively coupledcurrent. Direct Coupling Directcouplingoccurswhentheuseraccidentallyactivatesthe generatorwhilethe activeelectrodeisnearanothermetal instrument.Thesecondaryinstrumentwill becomeenergized. This energywillseekapathwaytocompletethecircuittothe patient return electrode.There ispotential for significantpatientinjury. Donotactivatethegeneratorwhiletheactiveelectrodeis touchingor in closeproximity toanother metal object. Insulation failure Manysurgeonsroutinelyusethecoagulationwaveform.This waveformis comparativelyhighinvoltage.Thisvoltageorâpushâ cansparkthrough compromisedinsulation.Also,highvoltagecan âblowholesâinweak insulation.Breaksininsulationcancreate analternaterouteforthecurrentto flow.Ifthiscurrentis concentrated,itcancausesignificant injury. Youcangetthedesiredcoagulationeffectwithouthighvoltage, simplybyusing theâcuttingâ currentwhileholdingtheelectrode indirectcontactwithtissue. Thistechniquewillreducethe likelihoodofinsulationfailure.Remember,you cancoagulatewith thecuttingcurrentbyholdingtheelectrodeindirectcontact with tissue,therebyloweringthecurrentconcentration.Bylowering current concentrationyouwillreducetherateatwhichheatis producedandratherthan vaporizetissueyouwillcoagulate- even though you are activatingthe âcuttingâcurrent. ⢠Direct Coupling ⢠Insulation failure ⢠Capacitive Coupling ActiveElectrode Telescope with camera Telescope view Abdominal Wall MetalTrocar Cannula Laparoscopic View Bowel Electrode Insulation Failure Active Electrode Metal Instrument Bowel
- 18. 17 Metal Cannula System A capacitorisnotapartlabeledâcapacitorâinanelectrical device.It occurswhenevera nonconductorseparatestwo conductors. DuringMISprocedures,anâinadvertentcapacitorâmaybe createdbythe surgicalinstruments.Theconductiveactive electrodeissurroundedby nonconductiveinsulation.Thisinturnis surrounded by aconductive metal cannula. A capacitorcreatesanelectrostaticfieldbetweenthetwo conductorsand, asa resultacurrentinoneconductorcan, throughtheelectrostaticfield, inducea currentinthesecond conductor. InthecaseoftheâinadvertentcapacitorâinanMISprocedure,a capacitormay becreatedbythesurgicalinstrumentsâcomposition andplacement. Plastic Cannula System Capacitancecannotbeentirelyeliminatedwithanallplastic cannula.The patientâsconductivetissuecompletesthedefinition of acapacitor. Capacitance isreduced,but isnot eliminated. Hybrid Cannula System Theworstcaseoccurswhenametalcannulaisheldinplacebya plasticanchor (hybridcannulasystem).Themetalcannulastill createsacapacitorwiththe activeelectrode.However,theplastic abdominalwallanchorpreventsthe currentfromdissipating throughtheabdominalwall.Thecapacitivelycoupled currentmay exittoadjacenttissueonitswaytothepatientreturnelectrode. This cancausesignificant injury. Conductor (Metal Cannula) Insulator (Electrode Insulation) Conductor (ElectrodeTip) Nonconductor (Plastic Cannula) Insulator (Electrode Insulation) Capacitively Coupled Energy to Metal Cannula Conductor (ElectrodeTip) Plastic Collar BowelElectrodeTip
- 19. 18 Most potentialproblems canbe avoidedby followingthese 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 ⢠Select an all metal cannula system as the safest choice. Do not use hybrid cannula systems that mix metal with plastic. ⢠utilize available technology, such as a tissue response generator to reduce capacitive coupling or an active electrode monitoring system, to eliminate concerns about insulation failure and capacitive coupling. TeflonÂŽ (PTfE) Coating and Elastomeric Silicone Coating ⢠use of a coated blade facilitates removal of eschar but does not eliminate need for frequent cleaning â Prevent eschar buildup, which increases resistance and contributes to arcing â Eschar can ignite and cause a fire ⢠Wipes clean with a sponge, eliminating the use of a scratch pad ⢠Scratch pad creates grooves on stainless blades ⢠grooves contribute to eschar buildup NOTE: Anycannula system may be used if an active electrode monitor is utilized. Elastomeric Silicone Coated Electrode ⢠Bendable ⢠retains cleaning properties longer ⢠Coating will not crack or flake ⢠Cutting edge performance similar to stainless steel electrode ⢠Enables surgeon to use lower power settings â reduces potential for thermal spread.
- 20. 19 ArgOn-EnHAnCED ElECTrOSurgEry Argon flow Argon-enhanced electrosurgery incorporates a stream of argon gas to improvethesurgicaleffectivenessoftheelectrosurgical current. Properties of Argon gas Argongas isinertandnoncombustible,makingitasafemedium through whichtopasselectrosurgicalcurrent.Electrosurgical currenteasilyionizes argongas,makingitmoreconductivethan air.Thishighlyconductivestreamof ionizedgas providesthe electrical current anefficientpathway. Argon-Enhanced Coagulation and Cut Therearemanyadvantagestoargon-enhancedelectrosurgical cuttingand coagulation. ⢠Decreased smoke, odor ⢠noncontact in coagulation mode ⢠Decreased blood loss, rebleeding ⢠Decreased tissue damage ⢠flexible eschar ⢠Inert ⢠noncombustible ⢠Easily ionized by r f energy ⢠Creates bridge between electrode and tissue ⢠Heavier than air ⢠Displaces nitrogen and oxygen
- 21. 20 âThe smokeplumegeneratedfromelectrosurgery contains chemicalbyproducts.TheOccupational SafetyandHealth Administrationrecommendsthat smokeevacuationsystems beusedtoreduce potentialacuteandchronichealthrisks to patients andpersonnel.â AORN Recommended Practices for Electrosurgery2003 -0.92 -0.77 -0.17 0.24 0.48 -0.84 -0.72 -0.66 -0.44 -0.58 -0.28 0.03 0.37 6 5 4 3 2 1 Log (Diameter, ď˝m) Log(p/mLper ď˝m) Laser ESU Coag mode Spectral Content of Surgical Smoke Surgicalsmokeiscreatedwhentissueisheatedandcellularfluid isvaporized by the thermal actionofanenergy source. Researchhasshownthatsmokefromelectrosurgeryis similarin contentto thatproducedbya surgicallaser. Ifyoucurrently evacuatetheplumefroma laser,youshoulddolikewisefor smokecreatedbyelectrosurgical generators. ViralDNA,bacteria, carcinogens andirritantsareknowntobepresentin electrosurgical smoke.Universalprecautionsindicateasmoke evacuation system shouldbeused. TheNationalInstituteofOccupationalSafetyandHealth(NIOSH) andthe CenterforDiseaseContro(CDC) havealsostudied electrosurgical smoke at length.The organizations concluded: âResearchstudieshaveconfirmedthatthissmokeplumecan containtoxic gases andvaporssuchasbenzene,hydrogen cyanide,andformaldehyde, bioaerosols,deadandlivecellular material(including bloodfragments) and viruses.â Smoke Evacuation Devices Newproductshavebeenintroducedtomakesmokeevacuation easierand moreeffective.Smokeevacuationdevicescannowbe attached directly to a standardelectrosurgicalpencil. TheAssociationofOperatingRoomNursesrevisedthe RecommendedPractices forElectrosurgeryinthe1994 AORN StandardsandRecommendedPractices forPerioperativeNursing. AORNincludedarecommendationforevacuationof allsurgical smoke atthattime andupdated thisrecommendation in 1998.
- 22. 21 ⢠âThe ESu should not be used in the presence of flammable agents (i.e., alcohol and/or tincture-based agents)â AORN Recommended Practices for Electrosurgery 2003 ⢠Avoid oxygen-enriched environments ⢠use of a nonconductive holster is recommended by: â ECrI, los Angeles fire Marshall,AOrn â Cutting your legal risks of Electrosurgery in OBg Management âThe active electrode(s)shouldbeplacedin a clean, dry,well- insulated safetyholsterwhennotin use.â AORNRecommended Practices for Electrosurgery 2003 ⢠Do not use red rubber catheters or other materials as a sheath on active electrodes â red rubber and other plastic materials may ignite with high power settings and in the presence of an oxygen- enriched environment â use manufacturer-approved insulated tips Radiofrequency is notalways confinedbyinsulation.Current leakage doesoccur . ⢠It is recommended that: â Cords not be wrapped around metal instruments â Cords not be bundled together Al COHOl Insulated blade electrode Insulated needle electrode
- 23. ⢠Ensure removal of the patient's jewellery, including any piercings. ⢠Assess the patient for implanted electronic devices, and be aware of potential patient safety hazards associated with them. ⢠Check that the metal snaps on the patient's gown aren't contacting his skin. Also verify that there's no contact between the patient and any metal appliances, such as the operating room bed, stirrups, and positioning devices, to avoid patient injury from electrical current concentrating at the site of metal contact or alternate pathway burns. ⢠Ensure that the dispersive electrode to be used is compatible with the ESU and appropriate for the procedure type to avoid patient injury. Unless specified by the company, large patient-return electrodes aren't appropriate for neonates and infants who weigh less than 25 lb (11.3 kg) and can cause injury. ⢠Apply appropriate-sized electrodes according to the manufacturer's recommendations. Note that cutting a disposable electrode to fit a patient is contraindicated because it increases the risk of injury.2 ⢠Inspect the disposable electrode for the amount and expiration date of the conductive gel. Expired electrodes may have ineffective gel (for example, gel that is dry with age), which decreases adhesion to skin and increases the risk of injury. Avoiding Burns
- 24. ⢠Clean the skin surface where you'll place the dispersive electrode. Make sure that the area is dry before placing the electrode because moist skin inhibits complete adhesion of the electrode, leading to an increased risk of injury. Avoid placing the electrode over a hairy area, if possible; if you can't avoid such an area, clip and remove excess hair before placing the electrode because excess hair prevents the electrode from adhering to the skin. ⢠Avoid placing the single-use dispersive electrode over a metal prosthesis, a tattoo, or broken skin. Tissue over prostheses contains scar tissue, which can impede the return of the electrical current. Many tattoos contain metallic dyes, which could lead to patient injury. ⢠When the patient is positioned for the procedure, place the single-use dispersive electrode over a large, well-perfused muscle as close as possible to the surgical site to prevent buckling of the electrode, which would lead to inadequate skin contact. Don't use tape to anchor the electrode. If an electrode dislodges during the procedure, notify the surgeon, turn off the ESU, and apply a new electrode.5 Avoiding Burns Conât
- 25. ⢠Elderly patients are more prone to skin damage from the placement of patient return electrodes due to loss of skin elasticity and muscle mass. Use caution when choosing sites for placement. ⢠Ensure that the reusable patient-return electrode has appropriate patient contact with weight-bearing areas of the body and that a minimal amount of material is used between the dispersive electrode and the patient. Distance and barriers between the patient and return electrode increase impedance, which can result in an alternate site injury. ⢠Keep all dispersive electrodes dry and protected from fluid pooling and leakage. Liquids may prevent the dispersive electrode from adequately contacting the skin, leading to skin injury. ⢠Don't use electrodes when flammable agents are present. Alcohol-based preparation agents are considered flammable until they're completely dry. Vapors present during evaporation are also considered flammable. Check for fluid pooling and trapping under the drapes to decrease the risk of fire and fire-related injuries. Avoiding Burns Conât
- 26. ⢠Apply monitoring electrodes as far away from the surgical site as possible to avoid burns at electrocardiogram (ECG) electrode sites. ⢠Use separate dispersive electrodes for each ESU used in an operative procedure. Store active electrodes in holsters when not in use to decrease the risk of unintentional cautery activation, which can lead to surgical fires and patient injury. ⢠Keep electrode cords free from kinks and coils during use to minimize the risk of patient and surgical personnel injury from conduction of stray current and capacitive current. ⢠Clean active electrode tips during the surgical procedure, as needed. ⢠If the electrodes are coated, wipe them with a moistened sponge. Avoiding Burns Conât
- 27. 22 Active Electrode Anelectrosurgicalinstrumentoraccessorythatconcentratestheelectric(therapeutic) current atthe surgical site. Active Electrode Monitoring A systemthatcontinuouslyconductsstraycurrentfromthelaparoscopicelectrodeshaft backtothe generatorandawayfrompatienttissue.Italsomonitorsthelevelofstray current andinterruptsthe power shoulda dangerouslevelofleakage occur. Bipolar Electrosurgery Electrosurgerywherecurrentflowsbetweentwobipolarelectrodesthatarepositioned aroundtissueto createasurgicaleffect(usuallydesiccation). Currentpassesfromone electrode,throughthedesired tissue,toanotherelectrode,thuscompletingthecircuit without enteringany other part ofthepatientâs body. Capacitive Coupling Theconditionthatoccurswhenelectricalcurrentistransferredfromoneconductor(the activeelectrode), throughintactinsulation,intoadjacentconductivematerials(tissue, trocars,etc.). Circuit The pathalongwhichelectricity flows. Current Thenumberofelectrons movingpasta givenpointper second,measured inamperes (A). Current Division Electricalcurrentleavingtheintendedelectrosurgicalcircuitandfollowingalternate pathstoground; typicallythecauseofalternatesiteburnswhenusingagrounded generator. Cutting Theelectrosurgicaleffectthatresultsfromhighcurrentdensityinthetissuecausing cellularfluidto burstintosteamanddisruptthestructure.Voltageislowandcurrent flowis high. Desiccation Theelectrosurgicaleffectoftissuedehydrationandproteindenaturationcausedby directcontact betweentheelectrosurgicalelectrodeandtissue.Lowercurrentdensity thansparking (cut). Direct Coupling Theconditionthatoccurswhenoneelectricalconductor(theactiveelectrode)comes intodirectcontact withanothersecondaryconductor(scopes,graspers).Electrical current willflowfrom the first conductor intothe secondary one andenergize it. Electrosurgery Thepassageofhighfrequencyelectricalcurrentthroughtissuetocreateadesired clinicaleffect. frequency Therateatwhichacyclerepeatsitself;inelectrosurgery,thenumberofcyclespersecond thatcurrent alternates. fulguration Usingelectricalarcs(sparks)tocoagulatetissue.Thesparksjumpfromtheelectrode acrossanairgap tothe tissue.
- 28. 23 Instant r esponse⢠Technology Anelectrosurgicalgeneratortechnologythatcontinuouslymeasurestheimpedance presentedbytarget tissuetotheactiveelectrode,and,inresponsetochangesinthat impedance,makes corresponding adjustments inthe voltagedelivered inthe cutmodes. Insulation failure Theconditionthatoccurswhentheinsulationbarrieraroundanelectricalconductoris breached. As a result,current willtravel outside the intendedcircuit. IsolatedOutput The output ofanelectrosurgicalgenerator thatisnot referenced to earth (ground). Monopolar Electrosurgery A surgicalprocedureinwhichonlytheactiveelectrodeisinthesurgicalwound; electrosurgerythatdirects currentthroughthepatientâsbodyandrequirestheuseofa patientreturn electrode. Patient return Electrode A conductiveplateorpad(dispersiveelectrode)thatrecoversthetherapeuticcurrent fromthepatient duringelectrosurgery,dispersing itovera widesurfacearea,and returnsittotheelectrosurgicalgenerator. Platesareusuallyrigidandmadeofmetalor foil-coveredcardboard;padsare usually flexible. Power Efficiency rating (PEr) A measureoftheabilityofanelectrosurgicalgeneratortoaccuratelydeliverthe selected power intoawide rangeoftissue types. radiofrequency Ablation System A systemthatusesradiofrequencyenergytoeffectivelyheatandcoagulatetarget tissuefor ablation. r esistance Thelackofconductivityortheoppositiontotheflowofelectriccurrent,measuredin ohms.Alsocalled impedance. return Electrode Monitoring A systemthatactivelymonitorstissueimpedance(resistance)atthecontactbetween thepatientâsbody andthepatientreturnelectrodeandinterruptsthepowerifthe qualityofthe contact is compromised. rf/radiofrequency Frequenciesabove100 kHzthattransmitsradiosignals,thehigh-frequencycurrent usedin electrosurgery. Vessel Sealing Technology⢠A methodofligatingvesselsthatcombinesthermaleffectsofaspeciallymodified bipolar electrosurgicaloutputwithhighcompressionforcetoalterthecollagenand fuse/obliterate the vessel lumen. Voltage Theforcethatpusheselectriccurrentthroughresistance;electromotiveforceor potential differenceexpressedin volts. Watt Theunitofmeasurement for power.