anaesthetic

Theadvantagesofcentralneuraxialblockarewellknown,butwhenitisudin

patie

incidenceofvertebralcanalhaematomaislow;afterreviewing1.5millionpatients,

Trybaestimatedtheriskas1/150,000epiduralanaestheticsand1/220,000spinal

r,theriskishigherinpatientswhohavereceiveddrugsthat

impaircoagulation.

In1994,Vandermeulencarriedoutaliteraturereviewtoidentifycareportsof

vertebralcanalhaematomaassociatedwithcentralneuraxialblockandfoundonly61

ecas,46wereassociatedwith

epiduraltechniques,32involvingacatheterandtheremainderoccurredafterspinal

anaesthesia.68%ofthecasoccurredinpatientswhoweretakinganticoagulant

drugs(mostcommonlyintravenousunfractionatedheparin)orhadacoagulopathy.

Theothercommonriskfactorwastechnicaldifficultieswithblockperformance.

Coagulationabnormalitiesand/ortechnicaldifficultieswereassociatedwithover87%

andermeulen’sreviewwaspublishedtherehavebeenover

70careportsofvertebralcanalhaematomaassociatedwithcentralneuraxialblock

inpatientstakinglowmolecularweightheparin(LMWH).Manysurgicalpatientstake

drugsthataffectnormalcoagulation,thereforetheriskassociatedwitheachdrugmust

beestimated(Figure1).

Regionalanaesthesiainpatientstaking

anticoagulants

MatthewRCheckettsisConsultantAnaesthetistatNinewellsHospital,Dundee,

ifiedfromtheUniversityofGlasgowandtrainedinanaesthesiain

Ayrshire,erestsincluderegionalanaesthesiaandvenous

thromboembolicdia.

Commondrugsaffectingcoagulation

•Aspirin

Thromboprophylaxisincoronaryorcarotidarterydia

•NSAIDs

Analgesicsudwidelyinarthritis

•Clopidogrel

Potentantiplateletudinacutecoronarysyndrome

•Warfarin

Thromboprophylaxisinatrialfibrillation,postprostheticheartvalve

replacement,treatmentofdeepveinthrombosisorpulmonary

embolism

•Unfractionatedheparin

Thromboprophylaxis,therapeuticanticoagulation

•Lowmolecularweightheparin

Thromboprophylaxis,therapeuticanticoagulation

•Fondaparinux

Thromboprophylaxis

1

Thromboprophylaxis

Deepvenousthrombosis(DVT)andpulmonaryembolismarecommonlyassociated

owerlimborpelvicsurgeryandtraumaputpatients

erature

recommendsanticoagulantthromboprophylaxisforthehigh-riskpatients.1The

patientsalsostandtogainmostfromregionalanaesthetictechniquessoguidelinesare

lneuraxialblocksignificantly

reducestheincidenceofDVTafterorthopaedicsurgerybutadditionalprophylaxisis

necessarytoreducetheratetoacceptablelevels.

Aspirinandnon-steroidalanti-inflammatorydrugs(NSAIDs)impairplateletfunction

byinhibitingplateletcyclo-oxygena(COX).AspirininhibitsCOXirreversiblywhile

oretheantiplateleteffectofaspirinpersistsuntilanew

plateletpopulationismanufactured(atleast7days),whereasplateletfunctionreturnsto

etheirwidespreaduformanyyears,

therehavebeenonlyfivecareportsofvertebralcanalhaematomainpatientsreceiving

fetoproceedwithcentralneuraxialblockinpatients

takingthedrugs,aviewendordbytheAmericanSocietyofRegionalAnaesthesia.2

COX-2inhibitors:celecoxibandrofecoxibareanti-inflammatorydrugsthatlectively

inhibitCOX-2,whichisnotexpresdinplateletsandthereforetheydonotaffect

esafewhenudalone,butcanpotentiatetheeffectof

warfarinbyincreasingtheprothrombintime.

Clopbits

ADP-inducedplateletaggregationandbindingbetweenplateletsandfibrinogen.

Theeffectsareirreversibleandplateletfunctiondoesnotreturntonormaluntilat

2001,theClopidogrelinUnstableanginato

preventRecurrentEvents(CURE)hentherehasbeen

amovetouclopidogrelincombinationwithaspirininpatientswithacutecoronary

r,therehavebeenmanycareportsofincreadandevenfatal

brvationalstudy

inpatientsundergoingcoronaryarterybypassgrafting,there-explorationratefor

bleedinginpatientstakingclopidogrelandaspirinwas10.4%comparedwith2.2%in

thotakingaspirinalone.3

Therehavebeenthreecasofvertebralcanalhaematomaassociatedwithcentral

neuraxialblockinpatientstakingclopidogrelandtwocasofmajorbleedingfollowing

lumbarsympatheticblock(onewasfatal).Theclopidogreldatasheetstatesthatit

tervalshouldalsobeobrved

commendedthat

individualhospitalsadoptpoliciestoensurethatclopidogrelisdiscontinuedbefore

tiplateleteffectmustbemaintained,aspirincanbesubstitutedsafely.

PlateletglycoproteinIIb/IIIaantagonistsincludeabciximab,eptifibatideandtirofiban.

Theyhavebeenrecommendedtopreventcoronaryischaemiceventsinhigh-risk

patients(/pdf/12_Glycoprotein_A4_

).Centralneuraxialblockshouldbeavoideduntilplateletaggregation

hasreturnedtonormal;aminimumof8hoursaftertirofibanandeptifibatideand

24–asheetsforthedrugsstatethattheyare

contraindicatedwithin4–6weeksoftraumaormajorsurgery.

Unfractionatedheparinhasbeenudformanyyearsforthromboprophylaxisand

aneousthromboprophylacticdosareldom

associatedwithbleedingcomplicationsandarenotconsideredtoincreatherisk

opinionrecommendsperforming

centralneuraxialblock4hoursaftertheadministrationofunfractionatedheparinor

tswhohavebeenreceiving

unfractionatedheparinformorethan4daysshouldhaveaplateletcount,becauthe

incidenceofheparin-inducedthrombocytopeniaisabout3%.

Therapeuticanticoagulationwithheparinisacontraindicationtoregionalblockand

anintravenousheparininfusionshouldbediscontinuedfor4hoursandtheactivated

partialthromboplastintime(APTT)shouldbenormalbeforeattemptingablockor

removingacatheter.

LMWHshavelongerhalf-livesthanunfractionatedheparin,whichallowsoncedaily

s

ate1990sinNorthAmerica,over

40casofvertebralcanalhaematomaoccurredfollowingcentralneuraxialblock

yhavebeenbecauNorthAmericando

guidelinesrecommendedtwicedailyLMWHadministration,meaningtherewasno

‘safe’arclusterofcas

wasnotreportedinEuropeeventhoughLMWHhadbeenavailablefor4yearslonger,

suggestingthattheoncedailyadministrationregimenudtherewassafer.

Currentguidelinesrecommendwaitingatleast12hoursafterLMWHadministration

erativeLMWHdosing

commendedthatthefirstdoisgiven

within6hoursofsurgery.

Ifhigh-doLMWHisudfortherapeuticanticoagulationittakesabout24hoursfor

ore,anintervalof24hoursshouldelapbefore

attemptingcentralneuraxialblockorperipheralnerveblock.

Fondaparinux:thisnewthromboprophylacticdrugisasyntheticpentasaccharide,

longereliminationhalf-lifethanLMWHof

ministered

6hoursaftersurgery,whichmakesdecisionsregardingregionalanaesthesiaeasier.

However,itslonghalf-lifemeansthatitshouldbeudwithcautioninpatientswith

rvalofatleast24hoursshould

elapbeforeremovalofneuraxialorperipheralnervecatheters.

Warfarinisindicatedforthromboembolicprophylaxisinmanycardiovascular

derpatientsprentingforsurgeryaretakinglong-termwarfarin

butthemostminorsurgicalprocedures,warfarinshouldbestoppedand

theinternationalnormalizedratio(INR)allowedtoreduceto1.5orless;thisnormally

tenappropriatetostartanalternativeanticoagulant,such

asLMWH,untilwarfarinisre-establishedandtheINRisbackinthetherapeuticrange

f1.5orlessisassociatedwithnormalhaemostasisanditis

tH

hasbeenadministeredinplaceofwarfarin,therecommendedintervalsdiscusd

alanaesthetic

techniquesshouldbeavoidedinpatientswithanINRover2.0.

Peripheralnerveblockandanticoagulants

Mostreportsofriousbleedingeventsassociatedwithperipheralnerveblockhave

followedpsoascompartment(lumbarplexus)l

larewas

associatedwithperioperativeadministrationofheparinandwarfarin,twowithLMWHand

twowiththienopyridineantiplateletdrugs(onewithticlodipine;onewithclopidogrelthatwas

fatal).Majorbleedingwasofgreatersignificancethanneuralcompressioninallthecas.

2

Copyright©2004TheMedicinePublishingCompanyLtd

TheguidelinesinFigure2couldbeappliedtoperipheralnerveblockperformance,

butsomeregionalanaesthetistswouldarguethatthiswouldbeunnecessarilyrestrictive.

Carefulconsiderationoftherisksandbenefitsofaperipheralnerveblockonan

individualpatientisthemostlogicalwaytopracti.

KEYREFERENCES

1HirschJ,DalenJE,GuyattG.6th(2000)AmericanCollegeofChestPhysicians

guidelinesforantithrombotictherapyforpreventionandtreatmentofthrombosis.

Chest2001;119:supplement.

2HorlockerTT,WedelDJ,alanesthesiaintheanticoagulated

patient:definingtherisks.(ThecondASRAConnsusConferenceonNeuraxial

AnesthesiaandAnticoagulation.)RegAnesthPainMed2003;28(3):172–97.

3YendeS,sofclopidogrelonbleedingaftercoronaryartery

reMed2001;29:2271–5.

Guidelinesforcentralneuraxialblockinpatientstakingdrugsaffectinghaemostasis

•AspirinandNSAIDs

Nocontraindication

•Clopidogrel

Stop7dayspreoperatively

•Unfractionatedheparin

Subcutaneous:give4hoursbeforeor>1hourafterblock

Intravenous:>catheter2–4hoursafterdo

•Lowmolecularweightheparin

Wait12hoursafterdoorgivedrug2hoursafterblock

Wait24hoursaftertherapeuticdo

•Warfarin

INR≤1.5