ANEWRADIOFREQUENCY(RF)BIPOLARSYSTEMFORFUSINGARTERIESUPTOAND
INCLUDING8MMINDIAMETER
R.D.Tucker
UniversityofIowaHospitalsandClinics,IowaCity,IA
Abstract
Background:SeveralsystemsarecommerciallyavailableforbipolarRFcurrentvesselsealing.This
studyexaminesanewsystem(BFM1)consistingofagenerator,whichautomaticallydeliversthe
necessaryenergy,andseveraldisposablebipolarinstruments.
Methods:Varioussizedarteriesweresealedwithbothcopperalloyandstainlesssteelelectrodes
andtissuetemperaturesweremeasuredbythermocoupleinaninvivoporcinemodel.
Tissue/electrodestickingwasmeasuredonascaleof1(noadherence)to4(tissueattachedto
jaws).Thesectionswereremovedandthesealburstpressurewasmeasured.Histologicalanalysis
wasperformedontheseals;anewthermalassessmentwasutilizedthatquantifiedtheamountof
“preservedvessel”damageratherthanthetypical“thermalspread”assessment.
Results:Arteriesweregroupedbysize:2-3(n=8),4-5(n=12)and6-8(n=46)mm;the
correspondingaverageburstpressureswere889,995,and896mmofHgwitharangeof350to
2110mmofHg.Theaveragetemperatureoftheelectrode-tissueinterfacewas97Cwitharangeof
67to118C.Stickingvaluesaveraged1.2.
Conclusions:ArterialsealsproducedbytheBFMsystemareequaltoorsuperiortotheleadingRF
bipolarsystemsin:burstpressure,damagetotheportionofthevesseltobepreservedandsticking.
Introduction
Theuseofvesselsealingelectrosurgicalsystemsinsurgicalprocedureshasbeenincreasinginthe
lastseveralyears.Thesesystemsareanattractivealternativetosuturingandclipapplyingbecause
oftheirspeedandversatility.Thisstudyexaminesanewvesselsealingsystemproducedby
BioFuseMedicalTechnologies(BFM)andquantitativelycomparestheBFMsystemwithanother
commerciallyavailablesystem(GyrusCorporation).Thesealedvesselburststrength,lateral
thermalspread,andamountofpost-sealtissuestickingtotheforcepswasquantifiedand
compared.
1TheoriginalpaperreferredtothegeneratortheLTCgeneratorandLiveTissueConnect.LTCwasthename
ofthecompanythattransitionedtowhatisnowBioFuseMedicalTechnologies,Inc.(BFM).ThetermsLTC
andLiveTissueConnecthavebeenreplacedwithBFMandBioFuseMedicalTechnologies.
TheBFMsystemconsistsofabipolarforceps,Figure1,whichareelectrifiedwitharadiofrequency
(RF)electrosurgerygenerator.Theforceps’selectrodesareplacedacrosstheveinorartery,andan
RFcurrentpassesfromthegeneratortooneelectrodeoftheforceps,throughthevesseltothe
secondelectrodeoftheforcepsandthenreturnstothegeneratortocompletethecircuitThe
systememploysanew,uniquesoftwarealgorithmandRFoutputthatisdesignedtosensecorrectly
sealedvesselsandautomaticallystopcurrentflow,minimizetissuestickingandminimizecollateral
tissuedamage.
Figure1:forcepsandcloseupofjaw
Thephysicalsealisaccomplishedbydenaturingcollagenandothercellularmacromoleculesinthe
vesselwallandfusingthesemolecules,bothphysicallyandchemically,intoanon-leakingseal.
Applyingtoomuchcurrentresultsinfurtherbreakdownofthelargemoleculesintosmaller
componentsaswellascharring,producingasealunabletowithstandsystemicbloodpressures.
Conversely,aninsufficientquantityofenergywillresultinthelackofpermanentbondingofthe
largemolecules,leadingtoapoorseal.TheBFMgenerator’salgorithmmeasurestheimportant
tissuevariablesinrealtimeandprocessesthesevariablestoinsurethatthecorrectamountof
energyisdeliveredtoproducethepropersealingeffect.
MaterialsandMethods
SusScrofiapigsweregivenIMketamineat14.7mg/kgandIVacepromazineat1.5mg/kgasa
preanesthetic.Surgicalplanewasmaintainedbyinhalationofisoflurane,3%solution.Allanimals
wereconnectedtoheartratemonitor,oxygenmonitorandventilator.Standardcutdownswere
performedontheexternalfemoral,femoral,leftiliac,brachialandcarotidarteries.Afterthefascia
wasremovedfromthevessel,theelectrodewascrossclampedonthearteryandtheRFcurrent
wasapplieduntilthevesselwassealed.
InthecaseoftheBFMsystemthegeneratorispreprogrammedtodeliverenergyandstop
automaticallyonceavesselsealisobtained.TheGyrussystemisenergizeduntilageneratorsound
changeindicatesthatthesealiscomplete,andatthispoint,thecurrentismanuallystopped.
Immediatelyafterthesealing,theforcepswereremovedandthetissue/forcepsstickingwas
gradedonascaleof0to4;0wasgivenfornotissueadherencetotheforcepsjawand4wasgiven
forthecompleteadhesionofthetwoelectrodestothetissue.
Inseveralofthesealsasmallthermocouplewasplacedatthecenterandproximalendofthejaw
andthetissuetemperaturewasmonitoredduringthesealingprocess.Notearrowsonfigurebelow.
Afterasealwascompleted,thevesselwasremovedandtheopenendtiedtoafinecannula.Saline
wasslowlyinfusedatarateof7ml/minwithamicroprocessorcontrolledsyringepumpandthe
vesselpressurewasmeasuredviaaYconnectortoadigitalmanometer.Thepressurewas
increaseduntilavalueof350mmHg±30mmHgwasreached;thispressurewasheldfor10
seconds.Thepressurewasthenincreasedatthesame7ml/minrateuntileitherthesealorthe
vesselwallburst.Thisultimateburstpressure(maximumpressure)wasautomaticallycaptured
andrecordedbythedigitalmanometer.
Next,thevesselwasplacedin10%bufferedformalinforatleast24hours.Thevesselswerecut
longitudinallyandplacedinparaffinblocks.Theblocksweresectionedand3microncutswere
stainedwithhematoxylinandeosin.Allsampleswerethenexaminedblindlybyasingle
pathologist.Thethermalspreadfromtheedgeoftheforcepsjawwasmeasuredbyacalibrated
ocularusingstandardlightmicroscopyandpolarizedlightmicroscopy.
AttheconclusionoftheexperimentsthepigswereeuthanizedbyanIVinjectionofpentobarbital,
90mg/kg,intoanearvein.
Results
•
AvesselbeingsealedisshowninFigure2;typicalsealsareshowninFigure3.Theseals
wereperformedontheleftcarotidarterywiththeBFMsystematanoutputsettingof50.
FIG.1:Forcepssealingvessel FIG2;Sealedvessel
•
Fortheburstpressuretesting,thearteriesweregroupedbysize:2to3mm;4to5mm,and
6to7mm.TheBFMsystemwasalsotestedon8mmarteriesbuttheGyrussystemwasnot
testedasitisnotFDAapprovedforvesselsgreaterthan7mm.Table1givestheaverage
burstpressureandstandarddeviationforeachofthevesselsizegroupsfortheLTCand
Gyrussystems.Thegroupvaluesarenotstatisticallydifferent.
Table1:Averagevesselburstpressure±standarderror(inmmofHg)fortheBFMandGyrus
systems.ThenumberofvesselstestedisgivenasN.
Diameter,
2to3mm 4to5mm
SE,Number Avg±SE
Avg±SE
Vessels
N
N
LTC
Gyrus
6to7mm
Avg±SE
N
916±79
1008±126 917±82
10
8
10
792±72
962±159
993±112
11
4
11
•
TheburstpressureaverageandstandarderrorforthesealsproducedbytheBFMsystem
on8mmarterieswas640±71mmofHg.
•
Theaverageburstpressureforallofthesealedvesselsforbothsystemswas:BFM,942mm
ofHgandGyrus,903mmofHg.
•
Afterthesealingthemeasuredstickingratingwasanaverageof0.06±0.14fortheBFM
systemand1.27±0.47fortheGyrussystem.
•
Duringthesealingprocessthemaximumaveragetemperatureoftheelectrode-tissue
interfacefortheBFMbipolarsealingdevicewas97ºCwitharangeof67ºCto118ºC.
•
Thethermalspreadfromtheedgeoftheelectrodejawwasalsomeasured;allvesselsizes
weregroupedtogether.Table2comparesthethermalspreaddatafortheBFMandGyrus
systems.TheBFMaveragelateralthermalspreadissignificantlylessthantheGyrus
thermalspreadatp=0.03.
Table2:Lateralthermalspreadfromthejawedge(inmm).
Avg±SE
N
LTC
0.40±0.08
52
Gyrus
0.72±0.10
51
Conclusions
•
TheBFMsystemproducesconsistentandreliableseals.
•
Bothsystemsmettheperformancecriteriaofholdingapressureofapproximately350mm
ofHgforaperiodof10seconds.
•
Thesealburstpressuresmadewiththetwosystemwerestatisticallyequivalent,although
theBFMsystemsealpressureswereslightlyhigher.
•
TheBFMsystemproducessealswithvirtuallynotissuestickingtotheforcepswhilethe
Gyrussystemproducedaslightamountofsticking.
•
TheautomatedBFMsystememploysauniqueoutputthatcontrolsthetissuetemperature
toanarrowrange,effectivelyminimizingdamagetonormaltissueandpreventingoverdesiccationandcharringinthesealitself.
•
TheBFMsystemproducedsignificantlylesslateralthermalspreadfromtheedgeofthejaw
thantheGyrussystem.
Summary
TheBFMopensealingsystemproducessealswithaburststrengththatisstatisticallyequaltobut
slightlyhigherthanthosefromtheGyrussystem.Thesesealswerecreatedwithnoticeablyless
tissuestickingandsignificantlylesslateralthermalspreadthanwiththeGyrussystem.