国外文献

Optimalhemodialysiscatheterselection

Maintainingpatientsonhemodialysiscathetersforthelongtermissuboptimalfrombothpatientcomfortandhealthcarecostperspectives.TheNationalKidneyFoundationKid-neyDiseaseOutcomesQualityInitiative(NKF-K/DOQI)guidelinesrecommendthatlessthan10%ofchronicrenalfailurepatientsbemaintainedondialysiscathetersbecauseofthehighratesofcomplications.17Intermsofhealthcarecost,theUnitedStatesspends$1to1.5billionannuallyonmain-tainingpatientswhousehemodialysiscatheters.18However,only10%ofthatistheactualcostofthedialysiscathetersthemselves.Alargeportionofthiscostgoestowardthehos-pitalizationandproceduralcostsnecessarytomanagepost-placementcomplicationsandcatheterexchange.Therefore,selectingadialysiscatheterthatminimizestheseeventscanyieldmanypatientandsocialbene ts.

CatheterMaterials

Short-Term/AcuteCatheters

Ingeneral,short-termcentralvenouscatheters(CVCs)forhemodialysisdonothaveaDacronretentioncuffandarenottunneled.19Whilethemajorityoflong-termCVCsaretun-neled,nontunneledshort-termcathetersareeasiertoplaceandremove.Thesecatheterscanberapidlyreplacedoveraguidewireatthebedsideandwithoutasurgeonorradio-graphicguidance.Therefore,thecathetershaftmustberigidenoughtoprogressthroughthesubcutaneoustissues.19Theymayalsobeprecurvedforjugularplacementovertheclavicletoreducedpatientdiscomfortandcathetermovement–relatedin-juryattheexitsite.20

Thecurrentstandardshort-termcatheterisaduallumencatheter,withthevenousport2to3cmdistaltothearterialporttopreventrecirculation.21Selectingbetweenthetwomajorbiomaterials,polyurethaneandsilicone,re ectsatradeoffbetweeneaseofplacementandblood ow.Therigidpolyurethanecathetercanbemoreeasilyplacedoverguide-wirewithoutasheath.Thematerialprovidesaninitialstiff-nessoninsertion,butthensoftenswhenexposedtobodytemperature.22Itcanalsowithstandhighnegativeaspirationpressures,permittingadequatehemodialysiswithasmallerdiametercatheter.Newerdesignsutilizesiliconetoprovidealargerlumenforhigherblood ow,reaching400mL/minorgreaterasopposedto250mL/minwithpolyurethanecathe-ters.21However,becauseofthe exibilityofthematerial,apeel-awaysheathmustbeemployed.

TheacutedialysiscathetermarketintheUnitedStatescon-sistsof vemajorcathetermanufacturers:Covidien(Mans eld,MA),ArrowInternational(Reading,PA),BardAccessSystems(SaltLakeCity,UT),AngioDynamics(Queensbury,NY),andMedcomp(Harleysville,PA).CovidienMAHURKAR,Arrow,BardNiagara,andMedCompDuoFlowacutedialysiscathetersaremadefrompolyurethane.Othercatheters,suchastheAngioDynamicsSchonXLandMedcompHemocatharemadefromsiliconeandincludeinsertionstyletstoproviderigidityonin-sertion.

ChronicCatheters

AccordingtoNKF-K/DOQIguidelines,long-termtunneledcuffedcathetersshouldbeinsertedwhenanticipateduseis3weeksorlonger.17Theselong-termcathetersaredesignedto

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besoftsothatendovasculartraumacanbeminimized.23Arigidshaftandtaperedtip,whichmaketheacutehemodial-ysiscathetereasytoinsert,alsorendersitunsuitableforlong-termuse.Ifleftforalongtimewithinthesuperiorvenacavaorrightatrium,therigid,sharpmaterialcouldcausesigni -cantinjurytothetissues.24

Chronichemodialysiscathetersarealmostalwaystun-neled,withabondedcuffforanchoringandforpreventingbacterialmigration.Centralvenousaccesshasbeenassoci-atedwithbacteremiaincidencesof2to7cases/1000cathe-ter-days.However,theratefornontunneledcathetersrangesfrom3.8to6.5/1000catheter-days,and1.6to5.5/1000catheter-daysfortunneledcuffedcatheters.25-29Whiletheseretrospectivestudiesdifferinde nitionandprotocol,ameta-analysisofrandomized,controlledtrialsbyRandolphandcoworkers30demonstratedthatcuf ngandtunnelingofcath-etersreducestheriskforcatheter-relatedbacteremiaby44to77%.Tunneledcathetershavealsobeenshowntoconferlowerinfectionandhospitalizationrates.16,31-33

ThechronicdialysiscathetermarketintheUnitedStatesconsistsofthefollowingcathetermanufacturers:Covidien,Arrow,Bard,AngioDynamics,Medcomp,BostonScienti c(Natick,MA),andSpire(Bedford,MA).Themajorityofthesechroniccathetersaremadefrompolyurethane,whichpro-videsaninitialstiffnessoninsertion,butthensoftenswhenexposedtobodytemperature.Othercatheters,suchastheCovidienPermcath,MedcompHemo-Cath,andMedcompHemo-Flowaremadeofsilicone.

Historically,long-termaccessdevicesweremadefrommedical-gradesiliconerubber.Itofferedasoft, exiblema-terialcausinglessdamagetotheintimaoftheveinoninser-tion.Itsbiocompatibility,relativelynonthrombogenicsur-face,andresistancetochemicalshelptoincreaselongevityandminimizecomplicationssuchasthrombosisandinfec-tion.ThecathetersaregenerallyautoclavedorEtOgasster-ilized.Thesoftnessofthesiliconepolymeralsoallowsforalargerlumenandplacementwithintherightatriumformax-imumblood ows.However,becauseoftoitsinherentsoft-ness,siliconecathetersoftenrequirethickerwallstopreventcollapseunderlowpressuresandtoavoidkinking.34Addi-tionally,thenecessityofalarge-diameterpeel-awaysheathimpliesalargercannulationholeinthevein.

Advancesinmaterialtechnologyhaveresultedinthetran-sitionfromsilicone-baseddialysiscatheterstotheuseofpolyurethane.Thermoplasticpolyurethanes(ormelt-pro-cessablepolyurethanes)areusedextensivelyinmedicalde-vices.Theyarecomposedoflong-chainlinearpolymerswithoutcross-links,whichareweaklybondedatroomtem-perature,butbecomefreetoslidepastoneanotherundersuf cientthermalenergy—suchasprovidedbythebody.35ComparedwithsiliconecathetersofthesameFrenchsize,polyurethanecatheterscanhavelargerinternaldiameterswithoutsacri cingrigidityoutsideofthebodyand exibilitywithinthebody.Theincreaseinlumendiameterresultsinincreasedblood owrate.Thecathetersareeasytoinsert,astheysoftenonentryintothebody.Agoodcathetermustalsohavesuf cientcolumnstrength,enablingittoadvanceintothebodywithminimaltangling.35Likesiliconecatheters,theseproductsarealsobiocompatible,nonthrombogenic,andEtOgassterilized.Inthecaseofmultilumenpolyure-thanecatheters,thinintraluminalwallscanbeconstructed,