Ultrasound-guided peripheral nerve blocks in anticoagulated patients - case series

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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:leohcferraro@yahoo.com.br(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/oucomoutrosdistúrbiosdacoagulação desdequeguiadosporultrassomefeitosporanestesiologistacomvastaexperiênciaem blo-queiosguiados.Entretanto,maioressériesdevemserfeitasparacomprovar asegurança 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 heparin5000U8/8h, simvas-tatin 20mgday−1, enalapril 20mg 12/12h, glibenclamide 5mg2×day,andmetformin850mg2×day.

Surgicalschedule

Righttranstibialamputation.

Proposedanesthesia

Ultrasound-guided femoral and sciatic nerve blocks and electricalnervestimulator.

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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,andaspirin100mgday−1duetorecentballoon

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 75mgday−1 due toleftiliac

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.

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_._The_patient_was

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).

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.

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,isosorbide20mg8/8h,atenolol

50mgday−1,hydralazine50mg12/12h,andregularinsulin.

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.

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 75mgday−1,

propra-nolol 80mgday−1, omeprazole 20mgday−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=71mgdL−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.

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,warfarin5mgday−1, captopril150mgday−1,

carvedilol50mgday−1,furosemide80mgday−1,simvastatin

20mgday−1. Preoperative tests: hemoglobina=9.4gdL−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.Patientistakentotheoperatingroom

forurgentsurgicalcleaningofrightkneepioarthritis.

Surgicalcleaningofrightknee.

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.

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

Forexample,inaseriesof4879patientswhounderwent cardiaccatheterizationorcoronaryangioplastyprocedures, during which the patients are anticoagulated, the fre-quencyofvascularcomplicationswas0.39%.Cathetersize and degree of anticoagulation inﬂuence the frequency of complicac¸ões.15 _However, _no _neurological _{complications}

occurredasaresultofvascular complications.The largest study to assess the risk of bleeding complications asso-ciated with peripheral nerve block included 670 patients who underwent continuous lumbar plexus block. In this study,patientsundergoinghiparthroplastywere anticoagu-lated withwarfarin andhad theirlumbar plexus catheter removed on the second day after surgery. At catheter removal time, the INR was measured. Of the 670 cases, 36% had an INR>1.4 at catheter removal. Only one case of bleeding was seen in a patient with INR>3.0, which was treated with local compression.16 _Only ₂₆ _cases _of

significant bleeding complications after plexus or periph-eral nerve blocks have been described in the literature in patients with normal or impaired hemostasis. In all patientswithneurologicaldeficit,neurologicalrecoverywas complete between 6 and 12 months. Although bleeding within a neurovascularsheath may resultin severe hypo-volemia, the chance of irreversible neurological ischemia decreasesduetotheexpandabilityfeatureofmost periph-eral locations. Despite the small number of reports, this series suggests that the main complication of peripheral nerveblocksinanticoagulatedpatientsissignificantblood loss, and not neurological deficit. It is noteworthy that the reported complications arose mainly in cases under-going deep blockade, such as lumbar plexus block, or thoseusingcatheterforcontinuousplexusblock.17---20_Thus,

the best way to assess the risks of a peripheral block could be the individualization of each route, as periph-eralblocksvaryindepth,scalability,andpossibilityoflocal compression.

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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.

17.WelleRS,GerancherJC,CrewsJC,etal.Extensive retroperi-tonealhematomawithoutneurologicdeﬁcitintwopatientswho

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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.

21.Kozek-LangeneckerSA,FriesD,GütlM.Locoregional anesthe-siaand coagulationinhibitors.Recommendations oftheTask Force on Perioperative Coagulation of the Austrian Society forAnesthesiologyandIntensiveCareMedicine.Anaesthesist. 2005;54:476---84.