Rev. Bras. Anestesiol. vol.66 número5

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REVISTA

BRASILEIRA

DE

ANESTESIOLOGIA

PublicaçãoOficialdaSociedadeBrasileiradeAnestesiologia

www.sba.com.br

SCIENTIFIC

ARTICLE

Patient

state

index

and

cerebral

blood

flow

changes

during

shoulder

arthroscopy

in

beach

chair

position

Mehmet

Ilke

Buget

a,∗

,

Ata

Can

Atalar

b

,

Ipek

Saadet

Edipoglu

a

,

Zerrin

Sungur

a

,

Nukhet

Sivrikoz

a

_,

_Meltem

_Karadeniz

a

_,

_Esra

_Saka

a

_,

_Suleyman

_Kucukay

a

_,

_Mert

_N.

_Senturk

a

a_˙Istanbul_University,_Istanbul_Medical_Faculty,_Department_of_{Anaesthesiology, ˙Istanbul,}_Turkey

b_˙Istanbul_University,_Istanbul_Medical_Faculty,_Department_of_Orthopedics_and_{Traumatology, ˙Istanbul,}_Turkey

Received21December2014;accepted13February2015 Availableonline1October2015

KEYWORDS

Patientstateindex;

Cerebral;

Cerebralbloodflow;

Beachchairposition

Abstract

Backgroundandobjectives: The aim ofthe study were to demonstrate the possible hemo-dynamic changes andcerebralbloodflowalterationsinpatients who werepositioned from supinetobeachchairposition;andtodetectifthepositionchangecausesanycorticalactivity alterationasmeasuredbythe4-channeledelectroencephalographymonitor.

Methods:35patientswereincluded.Beforetheinduction,meanarterialpressureandpatient stateindexvalueswererecorded(T0).Aftertheintubation,doppler-ultrasonographyofthe patients’internalcarotidandvertebralarterieswereevaluatedtoacquirecerebralbloodflow valuesfromtheformula.Insupineposition,meanarterialpressure,patientstateindexand cerebralbloodflowvalueswererecorded(T1)andthepatientwaspositionedtobeachchair position.After5minallmeasurementswererepeated(T2).Measurementsofpatientstateindex andmeanarterialpressurewererepeatedafter20(T3),and40(T4)min.

Results:There was a significant decrease between T0 and T1 in heart rate (80.5±11.6 vs. 75.9±14.4beats/min), MAP (105.8±21.9 vs.78.9±18.4mmHg) and PSI (88.5±8.3 vs. 30.3±9.7)(allp<0.05).Meanarterialpressuredecreasedsignificantlyafterpositionchange, andremaineddecreased,comparedtoT1.Theoverallanalysisofpatientstateindexvalues (T1---T4)showednosignificantchange;however,comparingonlyT1andT2resultedina stat-icallysignificantdecreaseinpatientstateindex.Therewasasignificantdecreaseincerebral bloodflowafterbeachchairposition.

Conclusion:Beachchair positionwas associatedwithadecreaseincerebralbloodflowand patientstateindexvalues.Patientstateindexwasaffectedbythegravitationalchangeofthe cerebralbloodflow;however,bothfactorswerenotdirectlycorrelatedtoeachother.Moreover, thedecreaseinpatientstateindexvaluewastransientandreturnedtonormalvalueswithin 20min.

∗_{Corresponding}_author.

E-mail:mbuget@yahoo.com(M.I.Buget). http://dx.doi.org/10.1016/j.bjane.2015.02.002

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PALAVRAS-CHAVE

PatientStateIndex; Cerebral;

Fluxosanguíneo

cerebral;

Posic¸ãodecadeira

depraia

PatientStateIndex_e_alterac_¸ões_do_fluxo_sanguíneo_cerebral_durante

artroscopiadoombroemposic¸ãodecadeiradepraia

Resumo

Justificativaeobjetivos: Oobjetivodoestudofoidemonstraraspossíveisalterações hemod-inâmicasedofluxosanguíneocerebral(FSC)empacientesqueforamposicionadosdesupinação para cadeira depraia (CP)edetectar seamudança deposiçãocausaalguma alteração na atividadecorticalcomomensuradopelomonitordeEEGcom4canais.

Métodos: Nototal,35pacientesforamincluídos.Antesdaindução,osvaloresdaPAMedoIEP foramregistrados(T0).Apósaintubação,ultrassonografiascomDopplerdacarótidainternae artériasvertebraisdospacientesforamavaliadaspara adquirirosvaloresdoFSCapartirda fórmula.Emsupinação,osvaloresdaPAM,IEPeFSCforamregistrados(T1)eopacientefoi posicionadoemCP.Após5minutos,todasasmensuraçõesforamrepetidas(T2).Asmensurações doIEPePAMforamrepetidasapós20(T3)e40minutos(T4).

Resultados: HouveumadiminuiçãosignificativaentreT0eT1naFC(80,5±11,6vs.75,9±14,4 bpm),PAM(105,8±21,9vs.78,9±18,4mmHg)eIEP(88,5±8,3vs.30,3±9,7)(p<0,05para todos).APAMdiminuiusignificativamenteapósamudançadeposiçãoepermaneceudiminuída emrelaçãoaT1.AanáliseglobaldosvaloresdoIEP(T1-T4)nãomostrounenhumamudança significativa, mas a comparação de apenas T1 e T2 resultou em redução estatisticamente significativadoIEP.HouvereduçãosignificativadoFSCapósoposicionadoemCP.

Conclusão:Oposicionado em CPfoi associadoàdiminuiçãodo FSCe dosvalores do IEP.O IEPfoiafetadopelamudançagravitacionaldoFSC;noentanto,ambososfatoresnãoestavam diretamentecorrelacionadosentresi.Alémdisso,adiminuiçãodovalordoIEPfoitransitória evoltouaosvaloresnormaisdentrode20minutos.

Introduction

Inshoulderarthroscopysurgeriesbeachchairposition(BCP) is often useddue tocertain advantages1_: _combined _with

‘‘controlledhypotension’’,itprovideseasieranatomic ori-entation and set-up, better visualization of subacromial spaceandglenohumeralstructures,anditisabetterchoice than lateral decubitus position for open surgeries. It also provides optimal upper extremity rotation control,2 _and

under normal circumstances many patients are operated in theBCP without any seriousadverse events;3 _however,

whenthepatientsarepositionedfromsupinetoBCPunder generalanesthesia,a markedreductionin cardiacoutput, meanarterialpressure(MAP)andcerebral perfusion pres-sure(CPP)canbeencountered.1,2,4

Following its relative recent introduction into the anesthesia practice, ‘‘Monitoring the depth of anesthe-sia’’ (DoA) is nowbecoming an important part of routine anesthesiamonitoring. TheSedlineelectroencephalograph based monitor is one such DoA monitoring options, and is used to monitor the state of the brain by real-time data by processing a 4-channel EEGsignals and providing numericalvaluetermedthePatientStateIndex(PSI).PSIis processedquantitativeEEGindextoevaluatethedegreeof consciousnessduringbothgeneralanesthesiaandconscious sedation.5 _The_sensitivity_of _the_PSI_index_depends_on_the

neurometrics technology it is using, and it can evaluate both the background EEG and the brain’s response to anesthetic agents.6---8 _Some _clinical _results _suggest _that

there are differences between DoA monitoring devices

(includingPSI)inevaluationofneurologicaldata.6,9_Several

studies have shown that changes in both hemodynamic status and cerebral perfusion can affect the accuracy of DoA measurements.10---12 _In _a _recent _study, _effects _of _BCP

onthebispectralindexhavebeeninvestigated;13_however,

therelationofBCPandcerebralbloodflow(CBF)andtheir effectsonPSIhavenotbeeninvestigatedbefore.

The hypothesis of this prospectivestudy wasthat BCP withcontrolledhypotensionwouldcauseaparalleldecrease bothinCBFandthePSI-value.Theaimsofthestudywere todemonstratethepossiblehemodynamicchangesandCBF alterationsinpatientswhowerepositionedfromsupineto beachchairposition(primaryoutcome);andtodetectifthe changefromsupinetobeachchairposition(BCP)causesany corticalactivityalterationasmeasuredbythe4channeled sedationmonitor(SedlineTM₎_(secondary_outcome)._As_a

ter-tiaryoutcomewehaveinvestigatedthetimecourseofPSI andbloodpressure.

Methods

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differencesamongthemeanswitha0.05significancelevel (two-tailed).

Informed consentwastaken from35 patientswhohad arthroscopicshouldersurgeryandagreedtojoinourstudy. Patientsbetweenage of18---80without anycarotid steno-sisororthostatichypotensionwereincluded.Patientswith anASA status3, 4or 5 andpatientswithcerebrovascular diseaseswereexcluded.

Allpatientswerepre-hydratedpriortotheirarrivalinto theoperatingroomwith1000ccsalineandpre-medicated with 2mg of midazolam. For postoperative analgesia all patientshadasingleshotinterscaleneblockunderUSG guid-ance.StandardmonitorisationincludedECG,SpO2,arterial pressure,capnography (Draeger ˙InfinityXL,Draeger Medi-cal Inc., 3135 Quarry Road, Telford, PA 18969, USA) and fourchanneledEEGtoevaluatethebrainfunction(Sedline withPSIMasimoCorporation,Irvine,USA).Invasivearterial pressuremonitorisation wasperformed via a 20G arterial cannulainsertedradialarteryonthenon-operated extrem-ity.Thetransduceroftheinvasivearterialmonitorwaskept at the level of heart. Before the induction, MAP and PSI valueswererecorded(T0).

Forallthepatientsanesthesiawasinducedwithfentanyl 1.5␮g/kg;propofol2mg/kg;rocuronium0.6mg/kg;andall

patientshadtrachealintubation.Inallpatients,anesthesia wasmaintainedwithremifentanilinfusion,50%O2/N2O

mix-tureanddesfluranetokeependtidaldesfluranelevelwas keptas6%.

After the intubation, Doppler USG of the patients’ internal carotid artery (ICA) and vertebral arteries were evaluated. The time averaged mean velocity (VTAM) was measuredforthevessels.Vesseldiameterwasmeasuredon USGandthecross-sectionalareaofeachvesselwas deter-mined with the formula r2. Flow volume is the product

ofVTAMandcross-sectionalarea.Thesumoftheflow vol-umes of ICA and vertebral artery was equal to the total CBF.14

Insupineposition,MAP,PSIandCBFvalueswererecorded (T1), and the patient was positioned to BCP. Both in supine and BCP, remifentanil infusion was started with 0.05␮/kg/minandwastitrated tomaintain MAPbetween

50and75mmHg.After5minfollowingpositioningto beach-chair, all measurements were repeated (T2). Patients, in whoma50%ormorereductioninCBFwasobserved,were excludedfromthestudy.Theoperationstartedimmediately afterT2recordings. Throughouttheoperation,inspiratory desfluraneconcentrationwasadjustedaccordingtothe end-tidalconcentration(i.e.not toPSI).MAPwaskeptat the valueinT2viaadjustmentintheratioofremifentanil infu-sion.IfMAPdecreased below50mmHg,a bolusof 500mL of colloidal solution and/or 1mg ephedrine IVwasgiven; ifMAPincreasedabove75mmHg(with noincreaseinPSI), theinfusionrateofremifentanilwasincreased.Violationof MAPaboveandbelowthelimits(50---75mmHg)wasnotan exclusioncriterion,unlessitwaspossibletomanageitback totherange.

Measurements of PSI and MAP were repeated after 20 (T3),and 40 (T4)min. Because of application difficulties, CBFwasnotmeasuredduringtheoperation(i.e.T3andT4). Attheendoftheoperation,patientswerepositionedback tosupine;extubationwasperformedregardingthePSIvalue andclinicalevaluation.AllpatientswerekeptinthePACU

Table1 Demographiccharacteristicsofthepatients.

Gender(F/M) 24/11

(68.6%/31.4%)

Age 48.4±12

Bodyweight(kg) 78.3±11.41

Height(cm) 169.71±13.09

for30min;aftertheassessmentofmodified-AldreteScore

andVAS,thepatientsweredischargedtotheward.

Statistical

analysis

SPSS.20softwarewasusedfortheanalysis.Pairedsamplest

-testsformeanswereusedforthepreinduction(T1)andpost

induction(T1)valuesofallmeasurements.Tocomparedata

(formeanarterialpressure(MAP),heartrate(HR),andPSI

afterthe induction(T1---T4),repeatedmeasuresof ANOVA

testwereperformed withTukey-testasposthoc;whereas

changesincerebralbloodflow(CBF)(T1vs.T2)were

eval-uatedwithpaired t-test. The p-value <0.05 wasnotedas

significant. Correlation between changes in PSI, MAP and

CBF after position change (i.e. between T1 and T2) was

examinedwithlinearregressiontests.

Results

Thirty-five patients were included in the study. Patient

demographicsareshowninTable1.Noneofthepatientswas

excludedfromthestudyduetoanyintraoperativeexclusion criteria.

TherewasasignificantdecreasebetweenT0andT1inHR (80.5±11.6 vs. 75.9±14.4beats/min), MAP (105.8±21.9 vs. 78.9±18.4mmHg) and PSI (88.5±8.3 vs. 30.3±9.7) (allp<0.05).Results ofT1toT4canbefoundin Table2. Meanarterialpressuredecreasedsignificantlyafterposition change toBCP, andremaineddecreased, comparedtoT1. TheoverallanalysisofPSI-values(T1---T4)showedno signifi-cantchange;however,comparingonlyT1andT2(immediate change fromsupinetoBCP)resultedina statically signifi-cantdecreaseinPSI(p-value<0.05).Therewasasignificant decreaseinCBFafterBCP(Figs.1and2).

800 700 600 500 400 300 200 100 0

T1

CBF (ml/min) PSI value

90 80 70 60 50 40 30 20 10 0 T2

MAP (mmHg)

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Table2 TimecourseofMAP,CBFandPSI(MAP,meanarterialpressure;CBF,cerebralbloodflow).T1,supine;T2,immediate afterbeachchairposition;T3,20minafterBCP;T4,40minafterBCP.

T1 (supine)

T2 (BCP)

T3

(BCP---20min)

T4

(BCP---40min)

MAP(mmHg)a _78.9_±_18.4 _64.9_±_12.1 _71.6_±_8.7 _68.2_±_10.7

CBF(ml/min)b _755.59_±_106.18 _586.75_±_84.79 _Not_measured _Not_measured

PSI(%)c _30.3_±_9.7 _27.3_±_7.2 _30.5_±_9.2 _30.5_±_7.5

a _p_>_0.0001;_where_T1_vs_T2:_p_<_0.001;_T1_vs_T3:_p_<_0.5;_T1_vs_T4:_p_<_0.01. b _p_<_0.001.

c _No_significant_change_with_repeated_measures_of_ANOVA;_p₌_0.0142_when_compared_only_T1_vs_T2.

90 _78.9

80 70 60 50

40 30.3428

30 20 10 0

T1

64.9

27.31

T2

PSI value

71.6

30.514285

T3

MAP (mmHg)

Figure2 Timecourse ofPSI-value:T1, supine; T2, beach-chairposition(BCP);T3,BCPafter20min;T4,BCPafter40min. NotethatthereisnosignificantchangeinPSIvalues,whenall measurementsarecompared.IfonlyT1vs.T2arecompared, thereisasignificantdecrease(p=0.0142).

None of the changes in the hemodynamic parameters studiedcorrelatedwithchangesinPSIvalues.Similarly,the changesincerebralbloodflowdidnotinteractwithchanges in level of sedation (PSI) (Linear Regressions regarding changesT1---T0:MAPvs.PSI(R-squared:0.05);CBFvs.PSI (R-squared:0.02);BPvs.CBF(R-squared:0.07);forall cor-relations:p>0.05).

Discussion

Inthisstudywehaveshownthatchangingthepositionfrom supinetobeach-chairwasassociatedwithadecreaseinMAP, CBFand alsoPSI-levels; whereby the decrease in PSIwas temporaryforonly20min,theMAPvaluesweredecreased throughouttheprocess.

ItshouldbenotedthatadecreaseinMAPis‘‘warranted’’ to achieve a decrease in bleeding during the operation; therefore it was not a ‘‘variable’’ of the protocol of our study,butitwaskeptwithinafixedmarginwithremifentanil infusion. BCP offers further advantages to a ‘‘controlled hypotension’’,suchasanatomicalpositioning,reduceduse ofarmtractionanddecreasedriskofbrachialplexusinjury. The majority of the studies investigating the changes in bloodpressurehavefoundadecreaseassociatedwith posi-tion change, probably due to gravitational reasons. The standard practice is to keep the MAP within limits after changingtoBCPtoachievetheadditiveadvantagesofBCP and controlled hypotension. We have shown that after a transient decrease in PSI parallel to MAP, the PSI values returnedtoinitialvalues.

CerebralbloodflowcanaffectthePSIvaluebothdirectly orindirectlyoverMAP.StudiesregardingtheCBFalterations

have reported contradictory results. McCulloch et al.15

foundthatBCPwasassociatedwithadecreaseinCBF,whilst Soedingetal.14_did_not_observe_any_change._One_of_the

pri-mary aimsof this study was todemonstrate the possible hemodynamicchangesandcerebral bloodflow alterations inpatientswhowerepositionedfromsupinetobeachchair position;wehaveshownthatbothbloodpressureandCBF decreasedsignificantlyafterpositionchange.Ourresultsare similartotheresultsfromtheMcCuloghstudy,atleastfor theinitialperiodofBCP.15

Inarecentstudy,Leeetal.13_have_examined_the

relation-shipbetweenbispectralindex,anotherDoAmonitor (BIS), withBCP. TheyfoundadecreaseinBISafterchangingthe positiontoBCP. However,inthat studythechange inCBF wasnot investigated; moreover, the results were limited to15min afterBCP. In ourstudy,we couldshow thatthe decreaseinPSIwasparalleltodecreasesinMAPandalsoCBF. Inaddition,thisdecreasewastransientfor20min,although thedecreaseinMAPpersisted.

Several studies have shown the reliability of differ-ent DoA monitors.16---19 _Obviously, _there _are _some _factors

affectingthe sensitivityandspecificity ofthesemonitors. Kawanishietal.haveshownthatBCPcanhavesomeimpact onBispectral Index,i.e. BCP cancause a decreasein BIS values.20 _Kawanishi _compared _patients _in _supine _position

andBCP,andinterestingly,thedifferenceinBISvalueswere observedonlyasasuccessionoftheposition,whereas end-tidalanestheticgasconcentrationandmeanbloodpressure didnotsignificantlydifferbetweenthegroupsconsistently. Itcanbeassumed thatthedecrease inCBFasaresultof gravitationalchangewouldalsocauseachangeincortical activitiesofthepatient.Ourstudyconfirmstheinformation ofthedecreaseinDoAmonitoringvaluealsofortheSedline monitor,andaddssomeimportantinformationtothisissue. First,althoughboththeBCPandthecontrolled hypoten-sionhavecontinued duringthe operation,PSIvalue hasa trendtowardthevaluesinsupinepositionandhasreached themwithinapproximately20min.Thiscanbeexplainedby ‘‘autoregulation’’ofthecerebralperfusion.Indeed,there wasalsoadecreaseinCBFimmediately aftertheposition change.Unfortunately,it wasnotpossibletomeasurethe CBFduringtheoperation.Itcanbeassumedthatthe cere-bralblood flowincreased toinitialvaluesagain, although thebloodpressureremainedlow.

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(i.e.corticalactivities).Thisresultconcludesthatalthough PSIcanbeaffectedbythepositionchangetobeach-chair; clearly,itisstillaDoAmonitorandisnotsuggestedtobea monitorofperfusion.

Some case reports have shown complications of BCP regardingcerebralischemia.PohlandCullenreportedfour casesof ischemic brainand spinal cordinjury,and Bhatti reported visual loss, and external opthalmoplegia after shouldersurgeries.21,22_The_authors_of_those_studies_assumed

thatthesecomplicationswereassociatedmostlywith pos-turalhypotensionandcerebralhypoperfusion.Fortunately, thefrequencyofthesecomplicationsisratherlowinthe lit-erature;evenlowerinpatientswhohadnopreviousfindings thatcouldaffectthecerebralperfusion(e.g.carotid steno-sis,atherosclerosis,etc.).Asamatteroffact,inourstudy, onlypatientswithoutanypreviousfindingsaffectingtheCBF wereincluded.ItcanbespeculatedthattheincreaseofPSI within20minafterBCFis,(insomespecificrange)an indica-toroftheautoregulationofCBF.Inpatientswithhigherrisk ofcerebralhypoperfusion,theeffectsofCBFpluscontrolled hypotensioncanvary.

The most important limitationof the study is thatthe CBFcouldnotbemeasuredduringtheoperation;thiswas notpossiblebecauseofthecloseproximityoftheoperation area;and even if a measurement were possible, its reli-abilitywouldbequestionable.However,thetimecourseof theCBFwasnotthehypothesisofthestudy,norwasitthe secondaryoutcome.

Similarly, cerebral oximetry has not been performed, becausethedealofthestudywasregardingtheperfusion andnottheoxygenationofthecortex.Patientswitha pos-sibleimpairmentofcerebralperfusionandperhapsalsoof cerebralautoregulationhavebeenexcludedfromthestudy. Therefore,thefindingsandalsothetimecourseinthisgroup ofpatientsshouldbeexaminedinfurtherstudies.

Inconclusion,ithasbeen shownthatbeachchair posi-tionwasassociatedwithadecreaseinbothcerebralblood flowandPSIvalue.PSI(i.e.corticalelectroencephalic activ-ities)wasaffectedbythegravitationalchangeoftheCBF; however,both factors arenot directly correlated toeach other.Moreover,thedecreaseinPSIvaluewastransientand returnedtonormalvalueswithin20min.

Conflicts

of

interest

Theauthorsdeclarenoconflictsofinterest.

Acknowledgements

WewouldliketothankMasimoCorporationforloaningthe Sedlinemonitorandsensorusedduringthestudy.

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