Rev. Bras. Anestesiol. vol.67 número1

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REVISTA

BRASILEIRA

DE

ANESTESIOLOGIA

Publicação Oficial da Sociedade Brasileira de Anestesiologia

www.sba.com.br

CLINICAL

INFORMATION

Ultrasound-guided

peripheral

nerve

blocks

in

anticoagulated

patients

---

case

series

Luis

Eduardo

Silveira

Martins

a

_,

_Leonardo

_Henrique

_Cunha

_Ferraro

a,b,∗

_,

Alexandre

Takeda

a,b

_,

_Masashi

_Munechika

a,b

_,

_Maria

_Angela

_Tardelli

a,b

a_Universidade_Federal_de_São_Paulo_(Unifesp),_Escola_Paulista_de_Medicina,_Disciplina_de_{Anestesiologia,}_Dor_e_Terapia_Intensiva,

SãoPaulo,SP,Brazil

b_Sociedade_Brasileira_de_{Anestesiologia,}_São_Paulo,_SP,_Brazil

Received20May2015;accepted15June2015

Availableonline26October2016

KEYWORDS Peripheralnerve block;

Ultrasound; Coagulation

Abstract

Backgroundandobjectives: The adventof ultrasound hasbrought many benefits to periph-eralnerveblocks.Itincludesbothsafetyandeffectiveness,giventhepossibilityofvisualizing the neurovascular structures andthe needleduring the procedure.Despitethese benefits, thereisnoconsensusintheliteratureontheuseofthistechniqueinanticoagulatedpatients orwithothercoagulationdisorders.Moreover,peripheralblocksvaryindepth,spreadability, andpossibilityoflocalcompression.However,fewsocietiestakeitintoaccountwhen draw-ingupitsrecommendations,establishingasinglerecommendationforperformingperipheral blocks,regardlessoftherouteused.Theobjectiveofthisseriesistoexpandthediscussionon peripheralnerveblockinanticoagulatedpatients.

Casereports: This series reports 9 cases of superficial peripheral nerve blocks guided by ultrasound inpatients withprimary or secondary dyscrasias.All blocks were performed by experiencedanesthesiologistsinthemanagementofultrasound,andtherewasnobruisingor neurologicalinjuriesinthecases.

Conclusions:This caseseriessupport thediscussiononconducting surfaceperipheralnerve blocksandeasylocalknowledgeastheaxillary,interscalene,femoral,saphenousorpopliteal inanticoagulatedpatients,ondualantiaggregationtherapyand/orwithothercoagulation dis-orders,providedthatguidedbyultrasoundandperformedbyananesthesiologistwithextensive experienceinguidednerveblocks.However,largerseriesshouldbeperformedtoprovethe safetyofthetechniqueforthesepatients.

∗_{Corresponding}_author.

E-mail:[email protected](L.H.Ferraro).

http://dx.doi.org/10.1016/j.bjane.2015.06.005

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PALAVRAS-CHAVE Bloqueionervo periférico; Ultrassom; Coagulac¸ão

Bloqueiosdenervosperiféricosguiadosporultrassomempacientesanticoagulados ---sériedecasos

Resumo

Justificativaeobjetivos: Oadventodaultrassonografiatrouxeinúmerosbenefíciosparaos blo-queiosdenervosperiféricos.Agregoutantosegurançaquantoeficácia,dadaapossibilidadede visualizaçãodeestruturasneurovascularesedaagulhaduranteoprocedimento.Apesardesses benefícios,nãoháconsensonaliteraturasobreousodatécnicaempacientesanticoaguladosou comoutrosdistúrbiosdacoagulação.Alémdisso,osbloqueiosperiféricosvariamcomrelaçãoà profundidade,expansibilidadeepossibilidadedecompressãolocal.Porém,poucassociedades levamissoemconsideraçãoparaelaborarsuasrecomendações,estabelecemumrecomendação única parabloqueiosperiféricos,independentementedaviausada. Oobjetivodestasérieé ampliaradiscussãosobrebloqueiodenervosperiféricosempacientesanticoagulados. Relatodecasos: Estasérierelata9casosdebloqueiosdenervosperiféricossuperficiaisguiados porultrassonografiaempacientescomdiscrasiasprimáriasousecundárias.Todososbloqueios foramfeitosporanestesiologistasexperientesnomanejodoultrassom,quenãoforam obser-vadoshematomasoulesõesneurológicasnoscasos.

Conclusões: Asériedecasosemquestãoajudaadiscussãosobrebloqueiosperiféricos superfici-aisedefácilcompressãolocal,comooaxilar,interescalênico,femoral,safenooupoplíteo,em pacientesanticoagulados,duplamenteantiagregadose/oucomoutrosdistúrbiosdacoagulac¸ão desdequeguiadosporultrassomefeitosporanestesiologistacomvastaexperiênciaem blo-queiosguiados.Entretanto,maioressériesdevemserfeitasparacomprovar aseguranc¸a da técnicaparaessespacientes.

Introduction

Theuseofultrasoundisincreasinglypresentintheeveryday lifeofanesthesiologists.Itisusedfordeepveinpuncture, peripheral block or even for neuraxial nerve blocks. The introduction of ultrasoundhas come toadd safety, effec-tiveness,andsuccesstosurgicalprocedures.1

Some benefits of this technique over neurostimulation havebeendemonstratedintheliterature.Amongthese,we highlight lowerincidenceoffailure,lesstimetoperform, shorterlatency,prolongedblockade,andlowerriskof acci-dentalvascularpuncture.2---10_Less_likely_to_promote_vascular lesions,ultrasound is an interesting tool toguide periph-eralnerveblocks,particularlyinpatientsonanticoagulants or withcoagulation disorders,which impose certain chal-lenges for regionalanesthesia dueto therisk of bleeding complicationsincaseofvascularinjury,especiallyatsites thathindervesselcompression.11

Despite the benefits mentioned, thereis no consensus in the literature regarding the indication of ultrasound-guided peripheral nerve blocks in patients with bleeding disorders. Despite the popularization and development of this technique, there are few cases described in the literature with the use of ultrasound in this type of patient.12

Below, we present a series of cases in which sciatic, femoral,andbrachialplexusnerveblocksguidedby ultra-sound wereperformed in anticoagulated patients, double

aggregatedor withother coagulation disorderswere per-formed.

Case

reports

SeeTable1.

Case1

SRR, female, 63 years old, ASA 3, history of systemic hypertension, chronic renal failure in conservative treat-ment, and type 2 diabetes mellitus. The patient was taken piperacillin---tazobactam due to severe focal sepsis on right lower limb, scheduled for transtibial amputa-tion.She wasalsotakenaspirin 100mgday−1_, _clopidogrel 75mgday−1_,_{unfractionated} _heparin₅₀₀₀_U_8/8_h, simvas-tatin 20mgday−1_, _enalapril ₂₀_mg _12/12_h, _{glibenclamide} 5mg2×day,andmetformin850mg2×day.

Surgicalschedule

Righttranstibialamputation.

Proposedanesthesia

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Table1 Summaryofultrasound-guidedperipheralnerveblocksinanticoagulatedpatients.

Aspirin Age Blockade Dyscrasia/drug Novel

neurological deficit

Hematoma Nerve

stimulator

Case1 3 63 Femoral+sciatic Aspirin+clopidogrel+heparin No No Yes

Case2 4 57 Femoral+sciatic Aspirin+clopidogrel No No Yes

Case3 3 74 Femoral+sciatic Aspirin+clopidogrel No No Yes

Case4 3 54 Interscalene

brachialplexus

Liverdisease(AP 61%)+thrombocytopenia 97,000mm−3

No No No

Case5 3 32 Femoral+sciatic Enoxaparin60mg12/12h No No No

Case6 4 73 Interscalene

brachialplexus

Aspirin+unfractionatedheparin No No No

Case7 3 71 Femoral+sciatic Clopidogrel+INR1.57 No No No

Case8 4 65 Femoral+sciatic Aspirin+clopidogrel+AP30%INR3.33 No No Yes

Case9 3 71 Femoral+sciatic Aspirin+warfarin(AP10%INR5.87) No No No

Femoralnerveblockwasperformed,inguinallevelwith 0.375% bupivacaine (10mL), with vasoconstrictor in 1.5% lidocaine (10mL), vasoconstrictor associated with sciatic nerve block, popliteal approach with 0.375% bupivacaine (15mL)andvasoconstrictor,and1.5%lidocaine(15mL)with vasoconstrictor.

The procedure was uneventful. In the postoperative period,thepatientprogressedwithadequate paincontrol andnochangesinsensitivityormotorfunctioninthe terri-toryoftheblockednerves.

Case2

ACR, 57 years old, ASA 4, history of dialysis for chronic renalfailure,chronicatrialfibrillation,hypertension,type 2 diabetes mellitus, and smoker (40packyears−1_). _The patientwas taking losartan, clonidine, enalapril, nifedip-ine, hydralazine, NPH insulin, in addition to clopidogrel 75mgday−1_,_and_aspirin₁₀₀_mg_day−1_due_to_recent_balloon angioplastyinrightposteriortibialartery.

Righttransmetatarsalamputation.

Ultrasound-guided femoral and sciatic nerve blocks and peripheralnervestimulator.

Femoralnerveblockwasperformed,inguinallevelwith 0.5% ropivacaine (10mL) and 1.5% lidocaine (10mL) with vasoconstrictor associated with sciatic nerve blockade, poplitealapproachwith0.5%ropivacaine(15mL)and1.5% lidocaine(10mL)withvasoconstrictor.

Surgicalprocedurewasuneventful,withdurationof1h and25min under lightsedation. Takentopost-anesthesia careunit (PACU),thepatient evolvedwithadequate pain control and no neurological deficits was seen in the first postoperativeperiod.

Case3

RCB, male, 74 years old, ASA 3, history of systemic hypertensionandperipheral arterialdisease,takenaspirin 100mgday−1 _and _clopidogrel ₇₅_mg_day−1 _due _to_left_iliac

arterystent1monthearly.

Lefttranstibialamputation.

Femoral nerve block was performed, popliteal level, with0.5% ropivacaine(10mL) and1.5%lidocaine (10mL), withvasoconstrictorassociatedwithsciaticnerveblockade, posterior suprapopliteal approach with 0.5% ropivacaine (10mL)and1.5%lidocaine(10mL)withvasoconstrictor.

Surgicalprocedurewasuneventful,withdurationof3h under light sedation. Taken toPACU, the patientevolved withadequatepaincontrolandnoneurologicaldeficitswas seeninthefirstpostoperativeperiod.

Case4

VLBNQ, female, 54 years old, ASA 3 due to liver disease secondarytohepatitisCvirus(HCV)infection,altered coag-ulation (61% prothrombin activity, INR 1.59). Additional testsevidencedplateletcount97,000␮L−1.Thepatientwas broughttotheoperatingroomforfixationofaleftforearm complexfracture.

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Proposedanesthetictechnique

General anesthesia associated with ultrasound-guided brachialplexusblock.

Ultrasound-guidedbrachialplexusblockwasperformed, interscalene approach, with 0.375% bupivacaine with vasoconstrictor(10mL)associatedwith0.25%lidocainewith vasoconstrictor(20mL).

Surgicalprocedurewasuneventful,withdurationof4h and50min.TakentoPACUundersensoryandmotorblock, thepatientevolvedwithadequatepaincontrolandno neu-rological deficitsseen in thefirst postoperative periodat hospitaldischarge.

Case5

FAS,male,32yearsold,ASA3duetothromboangiitis oblit-erans, taking enoxaparin 60mg 12/12h. The patient was broughttotheoperatingroomfordebridementofleft fore-footulcer.

Surgicaldebridementofleftforefootulcer.

Ultrasound-guidedfemoralandsciaticnerveblocks. Ultrasound-guided sciatic nerve block was performed, poplitealapproach, with0.375%bupivacaine(20mL) with-outvasoconstrictor,associatedwith1.5%lidocaine(20mL) withoutvasoconstrictor.

Surgicalprocedurewasuneventful,withdurationof1h under light sedation. Takento PACU,the patient evolved withadequatepaincontrolandnoneurologicaldeficitsseen inthefirstpostoperativeperiod.

Case6

LHO, female, 73 years old, ASA 4 due to chronic renal failureonhemodialysis,coronaryarterydisease,heart fail-ure, diabetes mellitus, and hypertension.It evolvedwith arteriovenous fistula thrombosis in the left upper limb. BroughttotheoperatingroomforFogarty thromboembolec-tomy.Takingunfractionatedheparinincontinuousinfusion pump,aspirin100mgday−1_,_isosorbide₂₀_mg_8/8_h,_atenolol 50mgday−1_,_hydralazine₅₀_mg_12/12_h,_and_regular_insulin.

Fogartythromboembolectomyofleftbrachiocephalic arte-riovenousfistula.

Ultrasound-guidedbrachialplexusblock

Ultrasound-guidedbrachialplexusblockwasperformed, axillary approach, with0.5% ropivacaine (15mL).Surgical procedurewasuneventful,withdurationof2hand10min

underlight sedation. Taken toPACU, the patient evolved withadequatepaincontrolwithoutneurologicaldeficitsor bruisingseeninthefirstpostoperativeperiodandwas dis-chargedonthethirdpostoperativeperiod.

Case7

Malepatient,71yearsold,ASA3duetosystemic hyperten-sion,type2diabetes mellitus, congestiveheart failureof ischemicetiology(three previousacutemyocardial infarc-tion,underwentcoronaryarterybypasssurgeryin2010;at theproceduretime,withoutangina,dyspnea,orthopnea), dyslipidemia,andsmoker(180pack-years).Taking clopido-grel 75mgday−1 _with _INR _1.57; _chest _radiograph _showed bilateralcongestionwithcostophrenicsinusopacificationon theright,andmarkedcardiomegaly.

Righttranstibialamputation.

Ultrasound-guidedfemoralandsciaticnerveblocks. Femoralnerveblockwasperformed,inguinallevel,with 0.5%ropivacaine(10mL) and1.5% lidocaine(10mL) with-outvasoconstrictorassociatedwithsciaticnerveblockwith poplitealapproach,with0.5%ropivacaine(10mL)and1.5% lidocaine(10mL)withoutvasoconstrictor.

Surgicalprocedurewasuneventfulunderlightsedation, withdurationof 1h and15min. At theend of the proce-dure,the patientwastakentothe recoveryroom. Inthe first24haftersurgery,therewerenobleeding,bruising,or novel neurologicaldeficits.Patient showed improvedpain controlinthefirst10haftertheprocedure.

Case8

Male patient, 65 years old, ASA 4 due to exacerbated chronic obstructivepulmonary disease, chronic renal fail-ureonhemodialysis,peripheralarterialdiseaseinthelower limbs,dyslipidemia,hypertension,tobacco(50pack-years) and alcohol consumption. Taking aspirin 100mgday−1_, clopidogrel 75mgday−1_, _captopril ₇₅_mg_day−1_, propra-nolol 80mgday−1_, _omeprazole ₂₀_mg_day−1_. _Preoperative tests:hemoglobina=7.9gdL−1_;_hematocrits₌_22.6%; leuko-cytes=13.100␮L−1; platelets=263.000␮L−1; prothrombin activity=30%; international normalized ratio=3.39; acti-vatedthromboplastintime=172.4swithnormalizedratioof 6.63;creatinine=6.30mgdL−1_;_urea₌₇₁_mg_dL−1_._Admitted totheinfirmaryforexacerbatedCOPDtreatment; evolved withpaininthelegandleftfoot.Vascularsurgeryfor left footevaluation revealed the presence of necrosis in 1st, 2nd,3rd,and4thtoes andwoundwithinfectious signsin theanteriorregion;emergencyamputationwasindicated.

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Femoralnerveblockwasperformed,inguinallevel,with 0.375%bupivacaine(20mL)withvasoconstrictorassociated with sciatic nerve blockade with subsequent infragluteal approachwithlidocaine1.5%(20mL)without vasoconstric-tor.

Surgicalprocedurewasuneventful,withdurationof1h and45min.The patientwastakentoPACU.Postoperative limbperfusionassessmentwasperformedusingDopplerand neurologicexaminationwasperformedtocheckthemotor responseintheterritoryofthefemoralandsciaticnerves, both within the normal range. On physical examination, therewas nodevelopment of hematoma at the puncture site.Thepatientremainedwithoutpaininthefirst10hafter theblockade.

Case9

Male patient, 71 years old, ASA 3 due to congestive heartfailureofischemicetiology(acutemyocardial infarc-tion, septal and inferior wall, two years ago), atrial fibrillation, chronic arterial disease of the lower limbs, hypertension, former smoker, ex-alcoholic; taking aspirin 100mgday−1_,_warfarin₅_mg_day−1_, _captopril₁₅₀_mg_day−1_,

carvedilol50mgday−1_,_furosemide₈₀_mg_day−1_,_simvastatin 20mgday−1_. _Preoperative _tests: _hemoglobina₌_9.4_g_dL−1_; hematocrit=27.8%; platelet=335,000␮L−1; prothrombin activity=10%; international normalized ratio=5.84; acti-vatedthromboplastin time=84s; urea=120mgdL−1_; crea-tinine=2.17mgdL−1_._Patient_is_taken_to_the_operating_room forurgentsurgicalcleaningofrightkneepioarthritis.

Surgicalcleaningofrightknee.

Ultrasound-guidedfemoralandsciaticnerveblocks. Femoral nerve block was performed, inguinal level, guidedbyultrasoundandperipheralnervestimulator,with 0.375%bupivacaine(20mL)withoutvasoconstrictor associ-atedwithUS-guidedinfraglutealsciaticblockandperipheral nervestimulator,with1.5%lidocaine(20mL)without vaso-constrictor.

Surgicalprocedurewasuneventful,withdurationof1h and30min.Postoperatively,thepatientshowednobruising atthepuncturesiteandthetestshowednomotororsensory changesin theterritory ofthefemoralandsciaticnerves. Thepatientremainedwithoutpaininthefirst12hafterthe blockade.

Therewerenoneurovascularcomplications inthenine reportedcases.Patientswerefollowed-upinthefirst24h aftersurgery,andnonovelneurologicaldeficitorhematoma wasfoundatthepuncturesites.Allprocedureswereguided byultrasound,andnerve stimulatorwasalsousedinfour cases.

Discussion

Withadvancesinmedicine,introductionofnewdrugsand technologies,lifeexpectancyhasincreasedsignificantlyin recent decades. With this advance, it has been observed a higher prevalence of cardiovascular diseases. Thus, it is routine to come across patients taking anticoagulant drugs and/or antiplatelet agents admitted tothe operat-ing room for urgent/emergency surgery. It is known that thediscontinuationofantiplateletdrugs,suchasclopidogrel andaspirin,maybringcomplications.Studiessuggest that aspirin discontinuation increases the incidence of throm-boticeventsin3.4%.13

Althoughspinalhematomais themostseriousbleeding complicationofregionalanesthesiaduetothecatastrophic effect of medullary canal bleeding, not expandable and non-compressible, the risk associated with techniques of plexus and peripheral nerves blocks is not well defined. Thefrequencyandseverityofbleedingcomplicationsafter plexusandperipheralnerveblockshavebeenlittlestudied. However, some reports of serious complications following vascular catheterizationfor surgical, radiological or heart procedureshavebeen describedintheliteratureandmay helpestimatethe riskofsome oftheperipheral blocksin thispopulation.14

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Table2 Societiesofanesthesiologyandguidelinesforperipheralblocksinthepresenceofanticoagulants.

ASRA2010 Therisksafterperipheralnerveblocksremainunclear.Conservativelyapplyrecommendationsto neuraxialanesthesiainhypocoagulatedpatientsinplexusanesthesiaorperipheralnervetechniques. ESRA2010 Therisksafterperipheralnerveblocksremainunclear.Conservativelyapplyrecommendationsto

neuraxialanesthesiainhypocoagulatedpatientsinplexusanesthesiaorperipheralnervetechniques. Germany2005 Lumbarplexusblockshouldfollowthesamerecommendationsofneuraxialblocks.

Wheneverpossible,thetimeintervalsfortheinsertionshouldfollowtherecommendationsof neuraxialblocks.

Donotcontraindicatetheexecutionofsuperficialperipheralnerveblock(singleprick)---axillary, femoralanddistalsciaticinpatientstakingaspirinandanticoagulants.

Austria2005 Deepblocks(performedinplacesofdifficultcompression),suchasinterscaleneblock,supra-, infra-clavicular,andlumbarplexus,shouldfollowthesamerecommendationsofneuraxialblocks.

Some societies, suchastheAustrianand German Soci-eties of Anesthesiology explicitly differentiate superficial nerve,deepperipheral, andneuraxialblocks.Ofthefirst, theaxillary,femoral,anddistalpoplitealmaybeperformed inthepresenceofanticoagulation(Table2).21

Furthermore,another factorthat shouldbeconsidered in peripheral nerve blocks in anticoagulated patients is theuseofultrasound.Meta-analysiscomparing ultrasound-guided peripheral nerveblock withthe classictechniques (paresthesia and neurostimulation) demonstrated a lower incidence of vascular puncture in cases with the aid of ultrasound.8

Thus, in our institution a protocol was established in which peripheral blocks are considered in anticoagulated patientsinthefollowingsituations:

Superficial blockage and of easy compression site; for example: axillary, interscalene, femoral, saphenous, popliteal.

Blockadesmustbeguidedbyultrasoundandmustbe per-formedbyananesthesiologistwithextensiveexperiencein guidednerveblocks.

Therefore,takingintoaccountthebenefitsof ultrasound-guided peripheral nerve puncture, as well as some characteristics of some routes for blockade, such as the depthandthepossibilityofcompression, someperipheral nerveblocksmaybecameasafeoptioninpatientswith pri-maryorsecondaryblooddyscrasias.However,largerseries shouldbeconductedtoprovethesafetyofthe technique forthesepatients.

Conflicts

of

interest

Theauthorsdeclarenoconflictsofinterest.

References

1.RandoK,Castelli J,PrattJP, etal. Ultrasound-guided inter-naljugularveincatheterization:arandomizedcontrolledtrial. HeartLungVessel.2014;6:13---23.

2.KapralS,GreherM,HuberG,etal.Ultrasonographicguidance improvesthesuccessrateofinterscalenebrachialplexus block-ade.RegAnesthPainMed.2008;33:253---8.

3.PerlasA,BrullR,ChanVWS,etal.Ultrasoundguidanceimproves thesuccess ofsciaticnerveblockatthepoplitealfossa. Reg AnesthPainMed.2008;33:259---65.

4.SauterAR,DodgsonMS,StubhaugA,etal.Electricalnerve stim-ulationorultrasoundguidanceforlateralsagittalinfraclavicular blocks:arandomized,controlled,observer-blinded, compara-tivestudy.AnesthAnalg.2008;106:1910---5.

5.ChanVW,PerlasA,McCartneyCJ,etal.Ultrasoundguidance improvessuccessrateofaxillarybrachialplexusblock.CanJ Anaesth.2007;54:176---82.

6.Domingo-Triado V, Selfa S, Martınez F, et al. Ultrasound guidanceforlateralmidfemoralsciaticnerveblock:a prospec-tive,comparative,randomizedstudy.AnesthAnalg.2007;104: 1270---4.

7.WilliamsSR,ChouinardP,ArcandG,etal.Ultrasoundguidance speedsexecutionand improvesthequalityofsupraclavicular block.AnesthAnalg.2003;97:1518---23.

8.AbrahamsMS,AzizMF,FuRF,etal.Ultrasoundguidance com-pared with electrical neurostimulation for peripheral nerve block: asystematic reviewand meta-analysis ofrandomized controlledtrials.BrJAnaesth.2009;102:408---17.

9.WarmanP,NichollsB.Ultrasound-guidednerveblocks:efficacy andsafety.BestPractResClinAnaesthesiol.2009;23:313---26.

10.Koscielniak-Nielsen ZJ. Ultrasound-guided peripheral nerve blocks: what are the benefits? Acta Anaesthesiol Scand. 2008;52:727---37.

11.Ferraro LHC, Tardelli MA, Yamashita AM, et al. Bloqueio dos nervos femoral e isquiático guiados por ultrassom em pacienteanticoagulado.Relatodecasos.RevBrasAnestesiol. 2010;60:422---8.

12.Bigeleisen PE. Ultrasound-guided infraclavicular block in an anticoagulated and anesthetized patient. Anesth Analg. 2007;104:1285---7;

KhelemskyY,RosenblattMA.Ultrasound-guidedsupraclavicular blockinapatientanticoagulatedwithargatroban.PainPract. 2008;8:152.

13.MaulazAB,BezerraD,MichelP,etal.Effectofdiscontinuing aspirintherapyontheriskofbrainisquemicstroke.ArchNeurol. 2005;62:1217---20.

14.HorlockerTT,WedelDJ,RowlingsonJC,etal.Regional anes-thesiainthepatientreceivingantithromboticorthrombolytic therapy: American Society of Regional Anesthesia and Pain MedicineEvidence-BasedGuidelines(ThirdEdition).RegAnesth PainMed.2010;35:64---101.

15.Fransson SG, Nylander E. Vascular injury following cardiac catheterization, coronary angiography, and coronary angio-plasty.EurHeartJ.1994;15:232---5.

16.ChellyJE,SzczodryDM,NeumannKJ.Internationalnormalized ratioandprothrombintimevaluesbeforetheremovalofa lum-barplexuscatheterinpatientsreceivingwarfarinaftertotal hipreplacement.BrJAnaesth.2008;101:250---4.

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underwentlumbarplexusblockandwerelateranticoagulated. Anesthesiology.2003;98:581---5.

18.Bicker P, Brandes J, Lee M, et al. Bleeding complications from femoraland sciaticnerve cathetersin patients receiv-ing low molecular weight heparin. Anesth Analg. 2006;103: 1036---7.

19.KleinSM,D’ErcoleF,GreengrassRA,etal.Enoxaparin associ-atedwithpsoashematomaandlumbarplexopathyafterlumbar plexusblock.Anesthesiology.1997;87:1576---9.

20.WelleR, Gerancher JC, Crews J, et al. Extensive retroperi-tonealhematomawithoutneurologicdeficitintwopatientswho underwentlumbarplexusblockandwerelateranticoagulated. Anesthesiology.2003;98:581---5.