Rev. Bras. Anestesiol. vol.67 número1

(1)

REVISTA

BRASILEIRA

DE

ANESTESIOLOGIA

PublicaçãoOficialdaSociedadeBrasileiradeAnestesiologia

www.sba.com.br

SCIENTIFIC

ARTICLE

Simple

method

for

determining

the

size

of

the

ProSeal

laryngeal

mask

airway

in

children:

a

prospective

observational

study

Murat

Haliloglu

∗

_,

_Sevgi

_Bilgen,

_Neslihan

_Uzture,

_Ozge

_Koner

YeditepeUniversitySchoolofMedicine,DepartmentofAnesthesiologyandReanimation,Istanbul,Turkey

Received21May2015;accepted22June2015 Availableonline19March2016

KEYWORDS

Child; Earauricle; ProSeallaryngeal maskairway

Abstract

Backgroundandobjectives: ThesizeoftheProSeallaryngealmaskairwayinchildrenis deter-mined by thepatient’s weight.However, insome instances, analternativemethodmay be required.ThisstudyaimedtocomparesizingbytheauriclewithconventionalProSeallaryngeal maskairwaysizingbyweightinchildren.

Methods:Afterapprovalbytheinstitutionalethicsboardandwritteninformedconsentfrom parents,197childrenwithAmericanSocietyofAnesthesiologistsphysicalstatusI---IIwhowere scheduledforaroutinegenitourinaryoperationwereincludedinthestudy.ThecorrectProSeal laryngeal maskairwaysizewas determinedaccordingtothesizeoftheauricle inchildren. Theresultswerecomparedwiththestandardweight-basedmethodrecommendedbythe man-ufacturer’s guidelines. The patients were classified into different groups depending onthe ProSeallaryngealmaskairwaysizesasdeterminedbybothmethods.Agreementbetweenboth techniqueswasevaluatedwithcoefficientstatistics.

Results:Insertionandadequateventilationwereachievedin185patientsatthefirstattempt, and12patients requiredasecondattempt.Threepatientshadtobeintubated.Agreement betweenthetwomethodsofsizeselectionoftheProSeallaryngealmaskairwaywasmoderate usingstatistics.

Conclusions: ChoosingthesizeoftheProSeallaryngealmaskairwayinchildrenaccordingto theauricle ofthechildisvalidandpractical.Inparticular,thisisanalternativemethod in situationswherethepatient’sweightisunknown,suchasinemergencysituations.

∗_{Corresponding}_author.

E-mail:[email protected](M.Haliloglu).

http://dx.doi.org/10.1016/j.bjane.2015.06.004

(2)

otamanhodaorelhaemcrianc¸as.Osresultadosforamcomparadoscomosdométodopadrão, baseadonopeso,recomendadopelasdiretrizesdofabricante.Ospacientesforamclassificados emdiferentesgrupos,dependendodostamanhosdasMLPSconformedeterminadoporambosos métodos.Aconcordânciaentreasduastécnicasfoiavaliadacomasestatísticasdocoeficiente kappa(k).

Resultados: Inserçãoeventilaçãoadequadaforamobtidasem185pacientesnaprimeira ten-tativa,e12 pacientesprecisaramde umasegundatentativa. Trêspacientesprecisaramser intubados.AconcordânciaentreosdoismétodosdeseleçãodotamanhodaMLPSfoimoderada usandoaestatística␬.

Conclusões:AescolhadotamanhodaMLPSemcriançasdeacordocomaorelhadacriançaé válidaeprática.Emparticular,esseéummétodoalternativoemsituaçõesnasquaisopesodo pacienteédesconhecido,comoemsituaçõesdeemergência.

Introduction

The ProSeal laryngeal mask airway (PLMA) has been

fre-quently used for airway management not only in the

operatingroom,butalsointheprehospitalandemergency

caresetting.1,2_The_PLMA_was_developed_by_Dr._Archie_Brain

in2000.3_The _PLMA_has_two_lumens_separating_the

alimen-tary and respiratory channels from each other, forminga

more effective seal than the LMA-Classic. This

supraglot-tic airway device has gained popularity in the pediatric

population. Selection of theoptimal size is important for

safeandeffectiveuseofthePLMA.Inchildren,the

manu-facturerrecommends thatthesize ofthePLMAshouldbe

basedonweight.4 _The _{weight-related}_technique,_which _is

thegoldstandardmethod,isnotalwaysapplicable.In

emer-gencyservices,thepatient’sweightissometimesunknown

oremergencyprovidershavesomedifficultiesrecallingthe

relationship between weight and size. In addition,

over-weightandunderweightchildrenmaybeexcludedfromthe

rangedefinedbytheweight-basedtable.5

In the following observational study,we evaluatedthe

suitability of the previously described, auricle size-based

method of PLMA selection for children in the Turkish

population.6 _The _primary_goal _of _our _study _was_to

deter-minewhethertheauriclesize-basedPLMAselectionmethod

isinagreementwiththeweight-basedformulaforpediatric

patients.Oursecondarygoalwastoachieveasuccessrateof

insertionofthePLMAofgreaterthan90%withtheauricle

size-basedtechniqueatthe firstattempt.Tovalidatethis

procedure,the size ofthe PLMAas determinedaccording

totheauricle-basedandage-basedformulawascompared

withthemanufacturer’sweight-basedformula.

Methods

ThisstudywasconductedwithIRBapprovalandwas

regis-teredwiththewww.clinicaltrials.govprotocol registration

system (NCT02257411).After obtaining approval fromthe

EthicsCommitteeof ourhospital(no346:18.06.2013) and

writtenparentalinformedconsent,thestudywasconducted

according tothe Declaration of Helsinki. This prospective

studywasperformedin197patientsoveraperiodof1year.

Childrenwith AmericanSociety of Anesthesiologists (ASA)

physicalstatusI---II,whowerescheduledforagenitourinary

operation,andin whomaPLMAwasindicatedfor general

anesthesia, wereeligibletoparticipatein thestudy.

Chil-drenandtheirparentswereseen1daybeforetheplanned

operationintheanesthesiapre-assessmentclinic.Exclusion

criteriaincludedanexpecteddurationofsurgerymorethan

3h,patientswhowereoutsidetherangeofthe15thto85th

growthpercentilesforweightand/orheightinchildrenup

to15yearsofage,gastro-esophagealreflux,ariskof aspira-tion,anairwayinfectioninthelast6weeks,orthepresence

ofdecreasedpulmonaryorchestwallcompliance.

Patientsfastedfor at least 6---8h for solids and2h for

clear fluids. According to the hospital protocol of

pre-medication,oralMidazolam0.5mg·kg−1_was_provided₃₀_min

beforeinductiontoallchildren.The childrenwereplaced

(3)

Figure1 SizeofthePLMA.

pillow to achieve an optimal position. Routine

monitor-ingwas performed, includingan electrocardiogram,pulse

oximeter,gasanalyser,non-invasivearterialpressure moni-tor,tidalvolumemonitor,andairwaypressuremonitor.After

four breaths of oxygen in 60% nitrous oxide,the

vaporiz-ers were set at 7% for sevoflurane. Facemaskventilation

wasperformed untilconditionsweresuitablefor insertion

of the laryngeal mask (loss of eyelash reflex, jaw

relax-ation, absence of movement). Muscle relaxants were not

used in the patients. As part of the pilot study,the size

of the auricle was measured with a ruler in the vertical

and horizontaldimensions in thefirst 20 participants and

theclosestcorrespondingsizeofthePLMAwaschosenfor

insertion (Fig. 1). Following the pilot study, selection of

thePLMAwasperformedbasedonvisualobservationrather

thanmeasurement(Fig.2).Iftheauriclefellbetweentwo

sizesof PLMA,theweight-based sizewaspreferred.Allof

thePLMAswereinsertedbytwoexperienced

anesthesiolo-gists,accordingtothemanufacturer’sinstructionswiththe

cuff fully deflated using the digital technique. Following

insertionof thePLMA,thedeviceswere inflateduntil the

cuffpressurereached60cmH2O,andtheywereconnected

tothebreathingcircuit.Fixationwasperformedaccording

tothemanufacturer’sinstructions.7_The_{volume-controlled}

mode with tidal volume at 8mL/kg was applied to the

patients.Respiratoryrateswereadjustedbyestablishingthe

inspiratory/expiratoryratioat1:2andtheend-tidalcarbon

dioxide at 30---35mmHg.Anesthesia wasmaintained using

sevoflurane in 66% nitrousoxide at 1.3 minimumalveolar

concentrations.Informationonthepatients’characteristics

wasobtainedaftertheoperationtoavoidbiaswhen

choos-ingthesizeofthePLMA.Foreachpatient,thesizechosen

withourmethod wascomparedwiththe sizedetermined

by the patient’s weight,according to the manufacturer’s

guidelines.

Initialassessmentofventilationwasperformedby

obser-vationofsquarewavetracingoncapnographyand

thoraco-abdominalmovement. In case of failure of insertion, the

PLMAwasremoved andtheweight-based suitablesizefor

childrenwasinserted.Theinsertiontimewasdefinedasthe

timebetweenremovalofthefacemaskandobservationof

thefirstend-tidalcarbondioxidewaveafterinsertionofthe PLMAintothemouth.Ifinsertioncouldnotbeachievedafter twoattemptsorifmechanicalventilationfailed(i.e.,high

peakairway pressure, high gas leakage, and an improper

airwaypressuretrace),itwasregardedasafailureandthe

childwasexcludedfromthestudy.Oropharyngealleak

pres-surewasdeterminedbyclosingtheexpiratoryvalveofthe

circuitwhen anaudiblenoisewasheard overthemouth.8

Becauseofsafetyconcerns;themaximalacceptable

oropha-ryngealleakpressurewas40cmH2O.Thecuffpressurewas

standardizedat60cmH2Oinallofthepatients.

The PLMA was removed at the end of surgery after

thechild returnedto an appropriatespontaneous

breath-ing pattern and was fully awake. Side effects (stridor,

laryngospasm,bronchospasm, orblood onthePLMA)were

recordedduringmaintenanceandrecoveryfromanesthesia.

Aftercompletion of thesurgery, the weight-based and

auricle-based PLMA selection techniques were compared

withthePLMAselectionaccordingtoage.

(4)

http://graphpad.com/quickcalcs/kappa2).SPSS(Statistical

Package for Social Sciences) for Windows 15.0 software

(SPSS,Chicago,IL)wasusedforstatisticalanalysis.

Results

Thepatients’demographiccharacteristicsandsurgicaland

anestheticpropertiesareshowninTable1.Themeantimeof

insertionofthePLMA,thenumberofinsertionattemptsand

successtoadequate ventilationarealsoshowninTable1.

Inthreeofthepatients,attemptsatinsertionofthePLMA

failedandthepatientshadtobeintubated.

Tables2and3showsacomparisonofthetwomethodsof

sizeselectionforthePLMA(weight-basedandauricle

size-based).InTable2,patientsweighing30kgwereincludedin thesizeofthe2.5PLMAgroup.InTable3,patientsweighing 30kgwereincludedinthesizeofthe3PLMAgroup.

Seventy-threepercentofthe patientsin Table2 and67.5% ofthe

patients in Table 3were found tobe in the rangeof the

recommendedweightbasedsize.

Agreementbetween the twomethods ofsize selection

of the PLMA (weight-based and auricle size-based) when

30kgpatientswereincludedinthe2.5sizePLMAgroupwas

goodusingstatistics(=0.62;SE=0.039,95%confidence

Table 1 Demographic data and surgical and anesthetic

properties.

Age(years) 4.7±2.9

Sex(female/male) 84(42.6%)/113(57.4%)

Weight(kg) 20.3±9.8

Height(cm) 106.8±22.5

ASAI/II 180(91.4%)/17(8.6%)

InsertiontimeofPLMA(s) 15±1.6

Durationofanesthesia (min)

70.5±14.7

Successrateplacement

Atthefirstattempt 185(93.9%)

Atthesecondattempt 12(6.1%)

Oropharyngealleak pressure;cmH2O

28.6±1.4

Peakinspiratorypressure; cmH2O

13.8±1.9

Complications

Bloodtingedequipment 7(3.6%)

Dataareshownasmean±standarddeviationornumber(%). PLMA,ProSeallaryngealmaskairway.

Total(n) 12 11 80 87 7 197

Dataareshownasnumber(n)ofpatients.

Table3 PLMAsizeaccording toweightandauricle

size-basedtechniques(30kgpatientswereincludedinthe3size PLMAgroup).

Weight-based Auricle-sizedbased

1 1.5 2 2.5 3 Total(n)

1 8 0 0 0 0 8

1.5 4 9 2 0 0 15

2 0 2 74 0 0 76

2.5 0 0 4 35 0 39

3 0 0 0 52 7 59

Total(n) 12 11 80 87 7 197

Dataarepresentedasnumber(n)ofpatients.

interval [CI]=0.54---0.70). The strengthwith theweighted

-testwas0.74,whichshowedgoodstrengthofagreement

between the two methods. Agreement between the two methodsofsizeselectionofthePLMAwhen30kgpatients were included in the 3 size PLMA group was moderate using statistics ( =0.56; SE=0.039, 95%CI=0.48---0.63). The strength of agreement withthe weighted kappatest was0.70, which alsoshowed goodstrength of agreement betweenthetwomethods.Theauriclesize-basedPLMAsize of 2.5 corresponded toaPLMA sizeof 3 according tothe weight-basedchart(Tables2and3).

Table4shows comparisonof theauricle-based method

size selection of the PLMA with age groups. Agreement

between thetwomethodsof sizeselection wasmoderate

Table4 PLMAsizesbasedonauriclesizeandage.

Age-based Auriclesize-based

1 1.5 2 2.5 3 Total(n)

<6months 12 0 0 0 0 12

6m---1.5yr 0 10 5 0 0 15

2---3yr 0 1 75 0 0 76

4---6yr 0 0 0 22 0 22

7yr 0 0 0 38 3 41

≥8yr 0 0 0 27 4 31

Total(n) 12 15 75 87 7 197

(5)

using statistics( =0.53;SE=0.039,95% CI=0.45---0.60). Thestrengthofagreementwiththeweightedkappatestwas 0.74, whichshowed goodstrength of agreementbetween thetwomethods.

Blood was identified on the PLMA after removal in sevenpatientsinthepostoperativeperiod.However,other complications, such as loss of airway, stridor, and laryn-gospasm,werenotdetected.

Discussion

The auricle size-based PLMA selection method showed a good correlation with the body weight-based selection methodin pediatric patients. Auricle size-basedselection resultedinasuccessrateofinsertionofthePLMAgreater than90%atthefirstattempt.

When the patients were classified according to age groups, auricle size-based PLMAselection appeared tobe more consistent than the weight-based chart, especially in children whowere 7 years of age. The PLMA size of 3 appearedtofitchildren≥8yearsoldthebestaccordingto ourauricle-size based method,whereas theweight-based methodproposedhalfasizelargerofPLMA.However, mak-inganassumptionaboutthesuccessofweight-basedPLMA selectioninpatientsolderthan7yearsisdifficult.Because theearsizedependsonageratherthanbodysize,prediction ofthePLMAsizebasedonageappearstobemoresuitable. Supraglottic airway devices, especially the laryngeal maskairway(LMA),haveincreasinglyreplacedendotracheal intubationnotjustintheoperatingroom,butalsoin prehos-pitalandemergencycaresettings.9_Because_of_anatomical

differences,LMAusemayresultindifficultinsertion,airway

obstruction,increasedventilatorpressure,and

oropharyn-gealleakinchildren.10,11_In_these_cases,_choosing_the

appro-priatesizeisimportantforsuccessfulinsertionandadequate

ventilation.Selectionofaninappropriately-sizedPLMAhas

been suggested asthe reason of malposition of laryngeal

masks.12,13 _Selection _of _the _appropriate _size _of _PLMA _in

childrenisnotevidence-based,andisderivedfrom

recom-mendationsoftheLMAmanufacturer.Themanufacturer

rec-ommendsthattheselectionofsizebebasedonweight.4,14

Voyagisetal. showedthatheightshould beconsideredin

selectingthesizeoftheLMA.15_Another_study_showed_that

usingasize2.5LMA(‘‘up-sizing’’)providedabetterfitthan size2inchildrenweighing10---20kg.16_Size_1.5_PLMA_can_be

usedinolderchildrenweighingmorethan10kg.17

Because development of the oropharyngeal cavity and

tissues surrounding the upper airway is linearly related

to age and height independently of sex or weight of a

child, pure weight-based methods may not be the most

suitable.14_In_addition,_overweight_and_underweight_children

may be excluded from the range defined by the

weight-basedtable.18 _In_emergency_situations,_the_true_weight_of

the patientis unknown and cannotbe easily determined.

In these cases, the patient’s weight may be incorrectly

estimated,19 _which _could _cause _an _{inappropriate} _size _of

PLMAtobeselected.Sometimesinthesesituations,

medi-calstaffcannotremembertherelationshipbetweenweight

andsize.

Oropharyngealleakpressureindicatesthedegreeof

air-wayprotection,thefeasibilityforpositiveventilation,and

thelikelihoodforsuccessfulplacementofaPLMA.8_To

pre-vent gas leakage and aspiration of pharyngeal secretion,

oropharyngealleakpressuremayneedtoexceedthe

pres-sure of fluid at the posterior pharyngeal wall, which is

approximatelyup to10cmH2O.20 Similarto ourfindings,

Goldmannetal.foundthatoropharyngealleakpressurewith

thePLMAwas28.60±1.36cmH2O.21

In our study, the insertion time was comparable with

thatreportedpreviously.15 _Insertion_of _the_PLMA_and

ven-tilationofthelungswerecompletelyunsuccessfulinthree

patients who showed anatomical positioning of grade 4.

Thesepatients hadtobeintubated. The anatomical

posi-tion was assessed by fiberoptic broncoscopy and graded:

1=vocal cords (visual obstruction of epiglottis to

lar-ynx<50%);2=arytenoidsorposteriorpartofthelaryngeal inlet;3=epiglottis(visual obstruction of epiglottis to lar-ynx>50%);and4=noglottalview;orviewofepiglottis.22

Similartoourfindings,Goldmannetal.showedthatthe

successrateofinsertionatthefirstattemptwas87%.Our

studyshowedthattheproposedauricle-basedsizingmethod

waseffectivein determiningtheappropriatesizeofPLMA

inchildren.

Inourstudy,wealsoincludedpatientswhowerelessthan

6monthsof age,differentfromthestudydone byZahoor

etal.whichisoneofthelimitationsoftheirstudy.6_Another

differencewithZahoor’sstudyisthatweperformedtwo

dif-ferentevaluationstodeterminethedifferenceswhen30kg

patientswerecategorizedtoeitherthe2.5or3sizePLMA

groups.Furthermore,wealsoexaminedwhetherdifferent

agegroupscorrelatedwellwithweight-orauriclesize-based

PLMAselection.Anotherstudyusedthewidthoftheindex,

middle,andringfingersofthepatientstodeterminethesize oftheLMA.23_In_that_previous_study,_the_mean_body_weight_of

thepatientsinthelaryngealmask3groupwas44±11.4kg.

The standard deviation in the data of these patients was

high.Thiswiderangeofbodyweightwithinthesamegroup

mayhavedistortedevaluationofthedata.

AllofthePLMAswereinsertedbyexperienced

anesthe-siologists,andourdatamaynotbeapplicabletothosewith

lessexperience.Thisisalimitationofourstudy.Future

stud-iesneed to determine the viability of the earsize based

PLMAselectionforchildrenwhoareoverweightandwhether

theuseofthismethodisadequateforadults.

Summary

We conclude that the proposed auricle-based method for

determiningtheappropriatesizeofthePLMAisuseful

com-paredwiththemanufacturer’sweight-basedformula.Inthis

case,theauricle-basedsizedeterminationmethodcanbe

appliedinclinicalpracticeasanalternativemethodtothe

weight-basedformula.

Conflicts

of

interest

Theauthorsdeclarenoconflictsofinterest.

Acknowledgments

WethankEmiMaedawhoprovidedmedicalwritingservices

(6)

waysizeforoverweightandunderweightchildren.Anaesthesia. 2010;65:50---3.

6.ZahoorA,AhmadN,SerecheG,etal.Anovelmethodfor laryn-geal maskairway size selectioninpaediatricpatients. EurJ Anaesthesiol.2012;29:386---90.

7.LMAProsealTMInstructionManual.1sted.SanDiego,CA,USA; 2000.

8.KellerC,Brimacombe JR,KellerK,etal.Comparisonoffour methodsforassessingairwaysealingpressurewiththelaryngeal maskairwayinadultpatients.BrJAnaesth.1999;82:286---7.

9.Jolliffe L, Jackson I. Airway management in the outpatient setting:newdevicesandtechniques.CurrOpinAnaesthesiol. 2008;21:719---22.

10.ParkC,BahkJH,AhnWS,etal.Thelaryngealmaskairwayin infantsandchildren.CanJAnaesth.2001;48:413---7.

11.MasonDG,BinghamRM.Thelaryngealmaskairwayinchildren. Anaesthesia.1990;45:760---3.

12.CookTM,LeeG,NolanJP.TheProSeallaryngealmaskairway: areviewoftheliterature.CanJAnaesth.2005;52:739---60.

algorithm.Anesthesiology.1996;84:686---99.

18.Johnston DF, Wrigley SR, Robb PJ, et al. The laryngeal maskairwayinpaediatricanaesthesia.Anaesthesia.1990;45: 924---7.

19.GreigA,RyanJ,GlucksmanE.Howgoodaredoctorsat estimat-ingchildren’sweight?JAccidEmergMed.1997;14:101---3.

20.BrimacombeJ,BerryA, BrainAI.Optimalintracuffpressures withthelaryngealmask.BrJAnaesth.1996;77:295---6.

21.Goldmann K, Roettger C, Wulf H. The size 1(1/2) ProSeal laryngealmaskairwayininfants:arandomized,crossover inves-tigationwiththeClassiclaryngealmaskairway.AnesthAnalg. 2006;102:405---10.

22.CookTM,McKinstryC,Hardy R,etal. Randomizedcrossover comparisonoftheProSeallaryngealmaskairwaywiththe Laryn-gealTubeduringanaesthesiawithcontrolledventilation.BrJ Anaesth.2003;91:678---83.