Rev. Bras. Anestesiol. vol.65 número5

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RevBrasAnestesiol.2015;65(5):349---352

REVISTA

BRASILEIRA

DE

ANESTESIOLOGIA

Official Publication of the Brazilian Society of Anesthesiology

www.sba.com.br

SCIENTIFIC

ARTICLE

Effectiveness

of

sub-Tenon’s

block

in

pediatric

strabismus

surgery

Kasim

Tuzcu

a,∗

,

Mesut

Coskun

b

,

Esra

Ayhan

Tuzcu

b

,

Murat

Karcioglu

a

,

Isil

Davarci

a

_,

_Sedat

_Hakimoglu

a

_,

_Suzan

_Aydın

a

_,

_Selim

_Turhanoglu

a

a_Department_of_{Anesthesiology}_and_Reanimation,_Medical_Faculty_of_the_Mustafa_Kemal_University,_Hatay,_Turkey

b_Department_of_{Ophthalmology,}_Medical_Faculty_of_the_Mustafa_Kemal_University,_Hatay,_Turkey

Received27November2013;accepted5February2014 Availableonline11March2014

KEYWORDS

Sub-Tenon’sblock; Pediatricstrabismus surgery;

Anesthesia

Abstract

Backgroundandobjectives: Strabismussurgeryisafrequentlyperformedpediatricocular pro-cedure.Afrequentlyoccurringmajorprobleminpatientsreceivingthistreatmentinvolvesthe oculocardiacreflex.Thisreflexisassociatedwithanincreasedincidenceofpostoperative nau-sea,vomiting,andpain.Theaimofthisstudywastoinvestigatetheeffectsofasub-Tenon’s blockontheoculocardiacreflex,pain,andpostoperativenauseaandvomiting.

Methods:Forty patients aged 5---16years with American Society ofAnesthesiologistsstatus I---IIundergoingelectivestrabismussurgerywereincludedinthisstudy.Patientsincludedwere randomly assignedinto two groups byusing asealed envelopemethod. Ingroup 1(n=20), patientsdidnotreceivesub-Tenon’sanesthesia.Ingroup2(n=20),followingintubation, sub-Tenon’sanesthesiawasperformedwiththeeyeundergoingsurgery.Atropineuse,painscores, oculocardiacreflex,andpostoperativenauseaandvomitingincidenceswerecomparedbetween groups.

Results:There were no significantdifferences between groups with regard tooculocardiac reflexandatropineuse(p>0.05).Painscores30minpost-surgeryweresignificantlylowerin group2thaningroup1(p<0.05).Additionalanalgesicneededduringthepostoperativeperiod wassignificantlyloweringroup2comparedtogroup1(p<0.05).

Conclusions: Inconclusion,wethinkthatasub-Tenon’sblock,combinedwithgeneral anesthe-sia,isnoteffectiveandreliableindecreasingoculocardiacreflexandpostoperativenausea andvomiting. However, thismethodis safe forreducing postoperative painanddecreasing additionalanalgesiarequiredinpediatricstrabismussurgery.

∗_{Corresponding}_author.

E-mail:[email protected](K.Tuzcu).

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350 K.Tuzcuetal.

PALAVRAS-CHAVE

Bloqueio subtenoniano; Cirurgiade estrabismo pediátrico; Anestesia

Eficáciadobloqueiosubtenonianoemcirurgiadeestrabismopediátrico

Resumo

Justificativaeobjetivo:A cirurgia de estrabismoé um procedimento oftalmológico comum em pediatria. Umgrande problemaque ocorrecomfrequência em pacientessubmetidos a essetratamentoenvolveoreflexooculocardíaco.Essereflexoestáassociadoao aumentoda incidênciadenáusea,vômitoedor.Oobjetivodesteestudofoiinvestigarosefeitosdo blo-queio subtenoniano sobre o reflexo oculocardíaco, a dor, anáusea e o vômito no período pós-operatório.

Métodos: Foramincluídosnoestudo40pacientesentre5-16anos,estadofísicoASAI-II, sub-metidos àcirurgia eletivade estrabismo.Foramrandomicamentealocados em doisgrupos, comométododeenvelopelacrado.NoGrupo1(n=20),pacientesnãoreceberambloqueio sub-tenoniano.NoGrupo 2(n=20),apósaintubac¸ão,obloqueiosubtenonianofoifeitonoolho submetidoàcirurgia.Usodeatropina,escoresdedor,reflexooculocardíacoeincidênciade náuseaevômitoforamcomparados.

Resultados: Nãohouvediferenc¸a significativaentreos grupos em relac¸ãoao reflexo oculo-cardíacoeaousodeatropina(p>0,05).Osescoresdedorem30minutosdepós-operatório foramsignificativamentemenoresnoGrupo2doquenoGrupo1(p<0,05).Anecessidadede analgésicoadicionalduranteoperíodopós-operatóriofoisignificativamentemenornoGrupo2 doquenoGrupo1(p<0,05).

Conclusões:Obloqueiosubtenoniano,emcombinac¸ãocomanestesiageral,nãoéeficaze con-fiávelparadiminuiroreflexooculocardíaco,bemcomonáuseaevômitopós-operatórios(NVPO). Porém,essemétodoéseguroparadiminuiradornoperíodopós-operatórioereduziraanalgesia adicionalnecessáriaemcirurgiadeestrabismopediátrico.

Introduction

Strabismussurgeryisoneofthemostfrequentlyperformed pediatric ocular operations.1 _However, _it _can _cause

unfa-vorablesideeffectsduringintraoperativeandpostoperative periods.Typically,themajorproblemsassociatedwith

stra-bismussurgeriesincludeincreasedriskoftheoculocardiac

reflex (32---90%). This reflex may occur in response to a

retractionoftheextra-ocularmusclesandisassociatedwith

anincreasedpostoperativenauseaandvomiting(PONV)

inci-dence(46---85%)resultingfromtheoculometricreflex.2---4

Inthepediatricpopulation,anotherimportantproblem

is postoperative pain management. Because of potential

side effects, opiates and non-steroidal anti-inflammatory

drugsshouldbeusedcautiouslyinthesecases,particularly

in outpatient surgeries. In recent years, regional

anes-thesiatechniques havebeen recommendedinconjunction

withgeneralanesthesia.5---8_{Sub-Tenon’s}_block_is_one_of_the

regionalanesthetictechniquesusedinocular surgery.This

techniqueinvolveslocalanestheticsbeinginjectedposterior toTenon’scapsule.

In thisstudy, we aimedto investigate theeffects of a

sub-Tenon’sblock on theoculocardiac reflex(OCR), pain,

andpostoperativenauseaandvomiting(PONV).

Methods

Forty patients aged 5---16 years with AmericanSociety of

Anesthesiologists(ASA)physicalstatusI---IIundergoing

elec-tive strabismus surgery were included in this study. All

the parents were informed and gave their written

con-sent. Ethical approval for this study wasprovided by the

localEthicsCommittee.Patientswithanocular pathology

other than strabismus, patients allergic tothe anesthetic

agent,and childrenwithout communicationabilities were

excluded. During the preanesthesia evaluation, children

wereencouragedtoreportpostoperativepain,ifpresent.

Forpremedication,0.5mg/kgmidazolaminaparticle-free

fruitjuicewasorallygiventoallpatients1hbeforesurgery.

Anesthesia induction wasachievedby 2.5mg/kg propofol,

1␮g/kgfentanyl,and0.6mg/kgrocuronium.Patientswere

intubatedtosecuretheirairway.Anesthesiawasmaintained

by2---3%sevofluraneina50%:50%(v/v)O2toairmixture.No

additionalfentanyldosewasused.Sevoflurane

concentra-tion wasincreasedby 0.5% when an increase higher than

20%, comparedtobaseline values,occurred in heart rate

and meanarterial pressure (MAP).End-tidal CO2 pressure

wasmaintainedbetween30and35mmHgduringsurgery.

Thepatientswererandomlyassignedintotwogroupsby

usingasealedenvelopemethod.Ingroup1(n=20),patients didnotreceivesub-Tenon’sanesthesia.Ingroup2(n=20),

followingintubation,sub-Tenon’sanesthesiawasperformed

withtheeyeundergoingsurgery.Sub-Tenon’sanesthesiawas

performed with 5% bupivacaine (0.08ml/kg). Under

ster-ile conditions, a 19-gauge curved, blunt metallic cannula

(25mm) wasinsertedintosub-Tenon’sspaceandthelocal

anestheticwasinjected.Surgerybegan5minafterthe

sub-Tenon’sinjection.

Allpatientsweremonitoredfor heartrate,blood

pres-sure, peripheral oxygen saturation (SpO2), and end-tidal

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Sub-Tenon’sblockinstrabismussurgery 351

Table1 Demographicdataofthepatients.

Group1 Group2 p

Age(years) 9(5---16) 11(5---16) 0.743 Weight(kg) 33.5(14---65) 38.5(17---65) 0.597 Gender(M/F) 8/12 10/10 0.525 Totalmuscles(1/2/3) 2/15/3 2/16/2 0.739 Operationtimes 75(30---150) 67.5(60---135) 0.735

5min. OCRwasconsidered anacuteincrease, higherthan 20%,inheartrateoranacutedecreaseinheartratebelow 60beats/min. In the case of OCR in this study,the surgi-calstimuluswaswithdrawn. Ifapatientdid notrespond, atropinewasgiven.Intraoperativefollow-upwasperformed by an anesthesiologist blinded tostudy groups. Paraceta-mol(15mg/kg,i.v.)wasgiventoallpatients15minbefore completion of the operation. When the operations were completed, patients were extubated by an antagonizing neuromuscular block with neostigmin and atropine. Pain, nausea,andvomitingwereassessedat 30minandat1,2, 4,and6haftersurgery.

Postoperative follow-up was performed by clinicians blinded to study groups. Postoperative pain was assessed by using a verbal pain scale (0=no pain; 1=mild pain; 2=moderate pain; 3=severe pain; 4=very severe pain). Additionalanalgesicdoses(ibuprofen,10mg/kg,p.o.)were giventopatientswithpainat amoderateor higherlevel. NumericscoringwasusedforPONV(0=nonausea;1=nausea ispresent,butnovomiting;3=vomitingoncewithin30min; 4=vomitingtwoormoretimeswithin30min).Ondansetron (0.1mg/kg,i.v.)wasgivenincasesofvomiting.

SPSS for Windows, version 15.0, wasused for statisti-calanalysis.Bothdescriptiveandanalyticalstatisticswere used.Chi-square/Fischer’stestswereusedforcomparisons betweencategoricalvariables.Normaldistributionsof con-tinuousvariables weretested witha Kolmogorov---Smirnov test.Mann-Whitney Utestswereusedtocomparemedian valuesbetweengroups. Statisticalsignificancewas consid-eredasp<0.05forallstatisticalanalysis.

Results

Inthisstudy,40patientswereassignedtooneoftwogroups with 20 patients per group. There were no significant differencesbetweengroupsregardingage,gender,weight, number of muscles operated on, and operation times (p>0.05).DemographicdataareshowninTable1.

AlthoughtheOCRdevelopedinfewerpatientsingroup2

(n=7)comparedtogroup1(n=10),therewasnosignificant

3 4

2

1

0

V

e

rbal r

a

ting scale

30 min 1 h 2 h 4 h 6 h

Group I

Group II

Time

Figure1 Postoperativeverbalratingscale.

difference between groups (p>0.05). There was also no

significant difference in atropine use due to the OCR

betweengroups(p>0.05;Table2).

AlthoughPONVwasobservedinfewerpatientsingroup2,

therewasnosignificantdifferenceinPONVscoresbetween

thegroups (p>0.05).Ingroup1,therewasnauseainfour

andvomiting insevenpatients,whereasingroup 2,there

wasnausea in two patients and vomiting in two patients

(Table2).

Whenpainscores30minaftersurgerywereconsidered,

painscoresweresignificantlyloweringroup2thaningroup 1(p<0.05)(Fig.1).Additionalanalgesic needsduringthe

postoperative period were significantly lower in group 2

compared to group 1 (p<0.05). Fifteen patients needed

additionalanalgesicdosesingroup1,whileonlysixpatients

neededadditionalanalgesicdosesingroup2.

Discussion

Regionalanesthesiaisusedasanadjunct togeneral

anes-thesia in children. Several studies have reported that

preoperative regional blocks reduce the need for

intra-operative anesthetic and opiates, and it contributes to

postoperative analgesia.9---12 _In _{ophthalmological} _surgery,

severaltypesofregionalblocksareusedincluding

peribul-bar, retrobulbar, and sub-Tenon’s blocks. However, in

peribulbarandretrobulbarblocks,systemiclife-threatening

complications or ocular complications may occur. These

conditions may include subarachnoid, intravenous local

anestheticsinjections,ocularcomplications,suchasglobe

perforation, nerve injury, and retrobulbar hemorrhage

that may potentially cause loss of vision.13---16 _As

sub-Tenon’s block is performed under direct visualization, it

provides a safe anesthesia with minimal risk for severe

complications.17,18

Table2 Incidenceofsideeffectsandsupplementarydrugrequirementspresentedasn(%).

Group1(n=20) Group2(n=20) p

IntraoperativeOCR 10(50%) 7(35%) 0.337

Intraoperativeatropine 4(20%) 4(20%) 1

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352 K.Tuzcuetal. OCR,atrigeminal---vagal reflexresponsemanifesting as

cardiac arrhythmias and hypotension, occurs in response to retraction of extra-ocular muscles during strabismus surgery. Several maneuvers have been proposed to elimi-nateorreduceOCRintheliterature.However,noneofthese methods are considered effective, safe, or acceptable.1,3

Intramuscularadministrationofanticholinergicagentsused

in premedication, such as atropine and glycopyrrolate,

areinadequateinpreventingOCR.19 _In_strabismus_surgery,

manipulation of extraocular muscles also increases PONV

incidencebystimulatingtheoculometricreflex.1,3---5

Astudyinwhichpropofolanesthesiawasusedinpediatric

strabismussurgeryreportedthatsub-Tenon’sblock

signifi-cantlydecreased OCR and PONVincidence.5 _In _our _study,

although OCR and PONV were less commonly observed in

thegroupthatunderwentsub-Tenon’sblock,thedifference

betweengroupswasnotsignificant.Thedifferencebetween

twostudygroups,despiteidenticalnumbersofpatientsin

groups, could be due to the distinct anesthetic methods

used.Propofolinfusioncouldhavecontributedtodecreased

PONVincidence.However,thisdoes notexplainthelower

incidenceofOCR.

In the pediatric population, another major

prob-lem is postoperative pain management. In recent years,

sub-Tenon’s block has frequently been used in

oph-thalmic surgery, as it provides akinesia in the globe and

has potential advantages over needle-based blocks.1,17,20

In a sub-Tenon’s block, local anesthetic is injected

posterior to Tenon’s capsule and distributed with

extra-ocularmuscles, therebyexertinganesthetic andanalgesic

effects.20,21

AstudybySteibetal.5 _reported_that_{sub-Tenon’s}_block

decreased postoperative pain when compared to a

con-trolgroupthatwasinjectedwithsaline.Inanotherstudy,

sub-Tenon’sblockwascomparedtoanintravenousfentanyl

injectionandreportedthatsub-Tenon’sblockprovided

bet-teranalgesia.7 _In_our_study,_{postoperative}_pain_scores_and

the need for additional analgesic were decreased in the

groupthatunderwentsub-Tenon’sblock;theseresultsare

inagreementwithliterature.5,10,22

In conclusion, we think that sub-Tenon’s block,

com-binedwithgeneralanesthesia,isnoteffectiveorreliablein

decreasingOCRandPONV.Furtherstudieswithlarger

sam-plesizes areneeded;however,asub-Tenon’sblockissafe

forreducingpostoperativepainandtheneedforadditional

analgesiainpediatricstrabismussurgery.

Authorship

KT, MC, EAT, MK and ID conceived the study and

partici-patedinitsdesignandcoordinationandhelpedtodraftthe

manuscript.SH,SAandSTperformedthereviewofthe

liter-ature,wrotetheinitialdraftandperformedthestatistical

analyses. MCand EAT performed surgery and drafted the

manuscript.ID andST analyzedthedata.Allauthorsread

andapprovedthefinalmanuscript.

Conflicts

of

interest

Theauthorsdeclarenoconflictsofinterest.

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