Rev. Bras. Anestesiol. vol.66 número6

REVISTA

BRASILEIRA

DE

ANESTESIOLOGIA

SCIENTIFIC

ARTICLE

Analysis

of

the

prevalence

of

atelectasis

in

patients

undergoing

bariatric

surgery

夽

Letícia

Baltieri

_,

_Fabiana

_Sobral

_{Peixoto-Souza}

_,

_Irineu

_{Rasera-Junior}

_,

Maria

Imaculada

de

Lima

Montebelo

_,

_Dirceu

_Costa

,

Eli

Maria

Pazzianotto-Forti

a_{UniversidadeEstadualdeCampinas(Unicamp),ProgramadePós-Graduac¸ãoemCiênciasdaCirurgia,Campinas,SP,Brazil} b_{UniversidadeNovedeJulho(Uninove),ProgramadePós-Graduac¸ãoemCiênciasdaReabilitac¸ão,SãoPaulo,SP,Brazil} c_{ClínicaBariátricadePiracicaba,Piracicaba,SP,Brazil}

d_{UniversidadeMetodistadePiracicaba(Unimep),ProgramadePós-Graduac¸ãoemCiênciasdoMovimentoHumano,Piracicaba,SP,}

Brazil

e_{UniversidadeFederaldeSãoCarlos(UFSCar),ProgramadePós-Graduac¸ãoemFisioterapia,SãoCarlos,SP,Brazil}

Received14April2014;accepted26November2014 Availableonline25November2015

KEYWORDS

Morbidobesity;

Bariatricsurgery;

Pulmonary atelectasis; Physiotherapy specialty

Abstract

Backgroundandobjective: To observe the prevalence of atelectasis in patients undergoing bariatric surgery and the influence ofthe body mass index (BMI), gender and age on the prevalenceofatelectasis.

Method: Retrospectivestudy of407 patientsandreportsonchestX-rayscarried outbefore andafterbariatricsurgeryoveraperiodof14months.Onlypatientswhounderwentbariatric surgerybylaparotomywereincluded.

Results:Therewasanoverallprevalenceof37.84%ofatelectasis,withthehighestprevalence inthelungbasesandwithgreaterprevalenceinwomen(RR=1.48).Therewasaratioof30% fortheinfluenceofageforindividualsundertheageof36,andof45%forthoseolderthan36 (RR=0.68).TherewasnosignificantinfluenceofBMIontheprevalenceofatelectasis.

Conclusion: Theprevalenceofatelectasisinbariatricsurgeryis37%andthemainriskfactors arebeingfemaleandagedover36years.

©2015SociedadeBrasileiradeAnestesiologia.Publishedby ElsevierEditoraLtda.Thisisan openaccessarticleundertheCCBY-NC-NDlicense( http://creativecommons.org/licenses/by-nc-nd/4.0/).

夽 _{Institution:UniversidadeMetodistadePiracicaba(Unimep),Piracicaba,SP,Brazil.}

∗_{Correspondingauthor.}

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

http://dx.doi.org/10.1016/j.bjane.2014.11.016

PALAVRAS-CHAVE

Obesidademórbida;

Cirurgiabariatrica;

Atelectasia pulmonar; Especialidade

emFisioterapia

Análisedaprevalênciadeatelectasiaempacientessubmetidosàcirurgiabariátrica

Resumo

Justificativaeobjectivo:Observar aprevalência de atelectasiaem pacientessubmetidos à cirurgia bariátrica e a influênciado índice de massa corporal (IMC), sexo e idade sobre a prevalênciadeatelectasia.

Método: Estudoretrospectivode407pacienteselaudos deradiografias detórax realizadas anteseapósacirurgiabariátricaduranteumperíodode14meses.Apenasospacientes sub-metidosàcirurgiabariátricaporlaparotomiaforamincluídos.

Resultados: Houveumaprevalênciageraldeatelectasiade37,84%,commaiorprevalêncianas basespulmonareseemmulheres(RR=1,48).Houveumaproporc¸ãode30%paraainfluênciada idadenosindivíduoscomidadeinferiora36anosede45%naquelescomidadesuperiora36 anos(RR=0,68).NãohouveinfluênciasignificativadoIMCsobreaprevalênciadeatelectasia.

Conclusão:Aprevalênciadeatelectasiaemcirurgiabariátricaéde37%,eosprincipaisfatores deriscosãosexofemininoeidadesuperiora36anos.

©2015SociedadeBrasileiradeAnestesiologia.PublicadoporElsevierEditoraLtda.Este ´eum artigoOpen Accesssobumalicenc¸aCCBY-NC-ND( http://creativecommons.org/licenses/by-nc-nd/4.0/).

Introduction

Obesityhasreachedepidemicproportions,andin2008over 1.4billionadultswereoverweight.1,2_{Inadditiontothe} co-morbiditiesthataccompanyobesesubjects,somechangesin therespiratorysystemandlungfunctioncanalsobefound, duetotheaccumulationoffataroundtheribs,diaphragm andabdomen,thuslimitingmovementoftheribcage.3

Obesity is achronic disease,3,4 _{and bariatricsurgery is} indicatedfor patientswhodonotrespondtoconservative treatment.4

InastudybyChungetal.5_{itwasshownthatobesityis} aforerunnerfortheappearanceofintraandpost-operative respiratory complications during or after surgery. Since gastroplasty, one of the bariatric surgery techniques, is upper abdominalsurgery, it presents changes inherent to this procedure, such as reduced lung volumes, increased respiratory rateand respiratory muscle dysfunction.6 _The appearanceofatelectasisisfrequentamongst alltypesof patientduringgeneralanesthesia.7,8_{Onsubmittingpatients} toelective upperabdominalsurgery,Pereiraetal.9 _found a 32% incidence of pulmonary complications in patients whopresentedtherestrictivepulmonarysyndrome,as com-paredto6%ofcomplicationsinpatientswithoutrespiratory co-morbidities. Atelectasis appeared in 34% of the whole sample.

Thesituationisworseinobesepatientsinwhom atelec-tasismayappearandpersistforupto24hafterextubation, which does not occur in non-obese patients.10 _Moreover, evenduring the surgical procedure, handling the abdom-inal cavity results in diaphragmatic elevation andfurther increasesthepossibilityofatelectasis.11

AccordingtoMartí-Valeri etal.,12 _{whostudiedpatients} suffering from obstructive apnea sleep syndrome (OASS), aprevalenceof17%of atelectasiswasdiagnosedbychest radiographyafterbariatricsurgery.

However,thereisalackofdataintheliterature concern-ingthe prevalence of atelectasias afterbariatric surgery,

eventhoughitisknownthatthiscouldconstituteoneofthe causesof pulmonarydysfunctionandrespiratoryfailurein thesepatients.

To recognize and identify postoperative respiratory complications after upper abdominal surgery could con-tributetothedevelopmentofpreventivestrategies.

Thehypothesisofthisstudyisthatpatientswithmorbid obesity whoundergo surgery may have a higher index of atelectasisduetoincreasedabdominalfatandtheneedfor generalanesthesia.

The aim of this study was to observe the prevalence of atelectasis in obese and morbidly obese patients who undergogastroplastyusingtheRoux-YGastricBypass tech-nique(RYGB)bylaparotomy,evaluatingthechestX-rays48h aftersurgery,andalsoobservinganyinfluenceoftheBMI, genderorageontheprevalenceofatelectasis.

Methods

Thestudyfollowedethicalguidelinesandwasapprovedby theEthicsCommitteeoftheMethodistUniversityof Piraci-caba,SP,Brazil(protocolnumber09/08).Thisisa retrospec-tivestudyinwhichchestX-rayreportsmadeafterbariatric surgerywereanalyzedatthemomentofhospitaldischarge (48h after surgery). Data were collected for a period of 14 months. The reports were collected fromthe medical recordsofpatientswhohadundergonebariatricsurgery.

OnlypatientssubmittedtoRYGB-type bariatricsurgery by laparotomy, witha BMIabove 35kg/m2_{, nopulmonary}

symptomsorlungdisease,normalpulmonary functiontest and normal preoperative chest X-ray, were included. All patientsweresubmittedtothepulmonaryfunctiontestand hadachestX-ray,butnolungdiseaseswereidentified. Dys-pneawasnotconsideredasarespiratoryco-morbidity,since itiscommoninpatientswithmorbidobesity.

oftheirhospitalstay,leadtoanincreasedriskofpulmonary complications,requirehospitalizationintheIntensiveCare Unit(ICU)ortheuseofcontinuouspressureairwaypressure (CPAP),bi-levelpositiveairwaypressure(BIPAP)therapyor additionaloxygen-therapyapartfromthestandardizedone duringpostoperativerecovery,orwhoshowedunstable post-operativeconditions.

They were submitted to a pre-anesthetic of inhaled sevoflurane and intravenous propofol, with maintenance of the anesthetic by continuous infusion pumping of remifentanil. Neuromuscular blockers (rocuronium, pan-curonium)wereadministeredduringtheprocedureandalso morphine, the latter being administered until complete post-anesthetic recovery,as required. Dipirona and keto-profen were used as analgesics in the ward by way of a periferic catheter.Mechanical ventilation wascarried out usingtheDrägerFabiusGSequipmentinthecontrolled vol-umemodewithatidalvolumeof6---8mL/kg,PEEPof5cm H2Oandinhaledoxygenfractionbetween0.4and0.6.The

patientsremainedinthe hospitalfor threedaysandtheir pre-operative chestX-ray reports showednoparenchymal lungalterationsaccordingtothereportmadebythe radiol-ogist.

In the postoperative period,all patients received con-ventional respiratory physiotherapy twice a day, with deepbreathing,use ofincentivespirometry,resourcesfor bronchial hygiene if needed, active or assisted coughing andassisted walking(at least60m)during thesession. In addition,allpatientstookpartinafollow-uppreoperative multidisciplinary group (doctor,physiotherapist, dietician, psychologistandphysicaltrainer).

The radiological examinationswere carried out during thepostoperativeperiod,i.e.,48hafterbariatricsurgery, beforehospitaldischarge.Therewerefoursessionsof phys-iotherapybeforetakingthechestX-rays,withtwosessions onthefirstpostoperativedayandtwosessionsonthesecond postoperativeday.

The chestX-ray examinationswereevaluatedfromthe report issued by the hospital radiologist. The following criteria were used to detect the presence of atelectasis accordingtoWoodringandReed13_{:displacementof} interlob-ularfissures,pulmonaryopacity,elevationofthediaphragm, displacementof thetrachea,heart, mediastinumand pul-monary hilum, compensatory hyperinflation of the lungs, coming together of the ribs and loss of alveolar volume. Data regarding age, gender, height, current body mass, ideal body weight, body mass excess and BMI were also collected.

The data were processedusing the Statistical Package for Social Sciences for Personal Computers(version 13.0) and the BioStat (version 5.3). The Shapiro---Wilktest was appliedtotestnormalityand,inthecaseofnormality;the data werepresented asthe mean andstandard deviation (SD).Thepatientsincludedwerecomputedinthedatabase alongwiththedemographicanddichotomizedinformation as‘‘yes’’or ‘‘no’’forthefollowing radiographicchanges: atelectasis,cardiacabnormalities,pneumoperitoneum, pul-monary congestion, pleural effusion and pneumonia. The statistical analysis was based on a study of the relation-ship betweenthe resultsof the atelectasisdetectiontest andthevariables:BMI, ageandgender, usingtherelative risk(RR)withaconfidenceintervalof95%.Inaddition,the

Table1 Characteristicsofthegroup:continuousvariables.

Mean±SD Range

Age(years) 36.96±10.16 18---68 Height(cm) 163.40±8.33 142---194 Bodymass(kg) 121.05±21.99 79.8---238.3 Excessbodyweight(kg)a _{65.98±20.35 26---174.2} BMI(kg/m2_{) 45.16±6.33 35.46---74.37}

BMI,bodymassindex.

a _{Based on the ideal body weight recommended by the}

MetropolitanLifeFoundation.14

chi-square(G-test)wasusedtoanalyzethestatistical asso-ciationbetweengenderandatelectasis.FortheBMIandage data,cut-offpointswereestablishedfortheanalysis,based onthemedianofthedata.p-Values≤0.05wereconsidered statisticallysignificant.

Results

The mean surgery time was 132±12min. The patients remainedinthepost-anesthesiarecoveryroomforan aver-age of 3h and received a 28% oxygen supply during this period.Whennecessary,theyreceivedanalgesicsaccording toamedicalprescription andrespiratoryphysical therapy twiceadayduringthepost-operativeperiod,including exer-ciseswithdeepandfractionatedinspiration,coughing,use ofarespiratoryencourageranddeambulation.

Ofthe patientswithnormalpreoperative chestX-rays, 413patientswereselected,and theirpostoperativechest X-rays (one per patient) were collected for analysis. Of these,sixpatientsandtheirpostoperativechestX-rayswere excludedbecausetheyweretakenintheexpirationphases, hamperingtheanalysis.Thus407patientsandtheirexams wereanalyzed.Tables1and2summarizethecharacteristics ofthegroup,anditcanbeseenthatwomenmadeupthe majorityofthesample,82.8%.

Table 2 Characteristics of the group: categorical variables.

n %

Gender

Female 337 82.8

Male 70 17.2

BMI

<40 92 22.6

40---49 224 55.04

≥50 84 20.64

Smoker

Yes 32 7.86

No 346 85.01

Ex-smoker

Yes 29 7.13

No 317 77.89

180

154 (37.8%)

80 (19.6%)

39 (9.58%)

23 (5.65%)

14 (3.44%)

8 (1.97%) 160

140

120

100

80

60

40

20

0

Atelectasis Cardiac abnormality Pneumoperitoneum Pulmonary congestion

Pleural effusion

Pneumonia

Figure1 Prevalenceofradiographicalterations.

Table3 Locationofatelectasis.

Locationofatelectasis n(%)

Rightlung

Base 26(6.58)

Thirdmiddle 5(1.27)

Apex 1(0.25)

Baseandthirdmiddle 1(0.25)

Leftlung

Base 24(6.08)

Thirdmiddle 9(2.28)

Apex 1(0.25)

Total 2(0.51)

Bilateral

Bases 58(14.68)

Predominanceonleft 9(2.28)

Predominanceonright 7(1.77)

Thirdmiddle 5(1.27)

Basesandthirdmiddle 2(0.51)

Others 4(1.01)

Onanalyzingtheradiologyreportsaprevalenceof37.84%

ofatelectasiswasobservedinthesample(Fig.1),located

mainlyinthelungbases,ascanbeseeninTable3. Itcanbe seenin Table3thatsome patientspresented atelectasisinmorethanone regionofthelung. However, itisworthmentioningthatnoneofthepatientsdiagnosed withatelectasisshowedanyclinicalrepercussions.

Astatisticallysignificantdifferencewasfoundbetween thegendersfortheprevalenceofatelectasis,withgreater prevalenceinwomen(p=0.043).By analyzingtherelative riskaRRof1.48(95%CI0.98---2.21,p=0.02)wasobserved andaratioof40%forwomenand27%formen.When ana-lyzingtheinfluenceofageontheprevalenceofatelectasis anRRof0.68(95%CI0.52---0.88,p=0.001)wasfoundanda ratioof30%forindividualsundertheageof36yearsand45% forindividualsovertheageof36years.TheRRoftheBMI fortheprevalenceofatelectasiswas0.94(95%CI0.73---1.21,

p=0.35)withaprevalence of36%for individualswithBMI below44kg/m2_{versus38%forindividualswithaBMIabove}

44kg/m2_.

Discussion

It can be seen that women made up the majority of the sampleinthisstudy,inagreementwiththestudyofOgden etal.15_{inwhichahigherprevalenceofobesitywasobserved} inwomen.

Inbariatricsurgery, several studies have reportedthat obesity isan independentriskfactor for thedevelopment of postoperative complications,5,16,17 _{and during general} anesthesia,pulmonarycomplicationsoftenarise,including atelectasis.7,18_{Howevertheresultsofthisstudyshowedno} increaseintheriskofatelectasisduetotheincreaseinBMI. AccordingtoWoodringandReed,13_{themorbidlyobesecan} show compression atelectasis of the lung parenchyma as a resultofthe abdominalcontents movingthediaphragm in a cephalic direction, which can be aggravated in the supineposition.Duringgeneralanesthesia,atelectasiscan develop,eveninhealthyindividuals,andisassociatedwith anincreasedintra-operativeshunt,leadingtogasexchange impairment.19 _{Perhapsthe best explanationfor its} occur-rence is a dysfunction of the diaphragm by way of an inhibitionofthephrenicnervereflexduringsurgical manipu-lation,withconsequentdiaphragmaticparesis.20_Atelectasis appearswithinminutesaftertheinductionofanesthesiaat 85%---90%, and its adverse effects persist in the postoper-ativeperiod,affectingrecoveryofthepatient.10,19,21_Such effectsofgeneralanesthesiaaremorepronouncedinobese individuals.

InastudycarriedoutbyEichenbergeretal.10_obeseand eutrophicindividualswereaccompaniedbychestcomputed tomography,carriedoutintheperiodsbeforetheinduction ofanesthesia,afterextubationand24haftersurgery.They observedthatatelectasisappearedinbothpatientprofiles aftertheinductionofanesthesia,butintheeutrophic indi-vidualsitwasresolvedinafewhours,whereasitpersisted for up to 24h after surgery in the obeseindividuals. The resultspresentedinthisstudyshowedahighprevalenceof atelectasis(37.84%)inthepopulationofpatientsundergoing bariatricsurgery.Althoughdealingwithlaminaratelectasis, thepresenceofthischangecangenerategreaterimpactin the morbidly obese,who alreadyhave alterations in lung functionandrespiratorymusclemechanics.3,22,23

second day after surgery, or approximately 48h after surgery. The study of Eichenberger et al.10 _{stopped the} assessments24hafterextubation,butthepresentstudystill observed a high prevalence of atelectasis even48h after surgery.

The presenceofatelectasisinthepostoperativeperiod may result in the very frequent complaint of dyspnea in morbidlyobesepatients.24_{Mostoftheatelectasisobserved} inthepresent studywaslocated inthelungbase regions. AccordingtoSood25 _{theobeseindividualhasincreased} air-wayclosureinthedependentregionsofthelungandthereis cephalicdisplacementofthediaphragmduetothe compres-sion of the abdominal contents. In these patients, these alterations are more pronounced after bariatric surgery, adding other factors such as pain, the fear of breathing deeply and suppression of thee cough mechanism, either becauseofpainordecreasedmucociliaryclearancedueto intubation,anesthesiaandanalgesia,causingthe accumu-lationofpulmonarysecretionsandfavoringtheemergence ofatelectasis.26

The hypotheses of this study included the possibilities ofincreasingatelectasiswithincreasingageandBMI.This hypothesis was only confirmed for the age variable, for which,byadoptingthemedianvalueof36years,ahigher prevalenceofatelectasiswasobservedintheoldergroup. The factthat norelationship wasfound betweenBMI and the prevalence of atelectasis can be explained by the sample being composed only of morbidly obese patients, thosemostat riskfordevelopingatelectasis.10 _Ifthe sam-ple had been constituted of eutrophic individuals in the samepostoperative clinical conditionsandsurgical proce-dure, maybe the risk observed would have been higher in the morbidly obese patients. As for the female gen-der as a risk factor for the development of atelectasis, one hypothesis which may explain this, at least in part, was the presence of excessively large breasts in these morbidly obese volunteers. According to Cunha et al.,27 big and bulky breasts can have a restrictive effect on thechest,interferingwithrespiratorydynamics,andthey observed an increase in total lung capacity (TLC) and residualvolume(RV) in volunteerssubjected toreductive mastoplasty. The decrease in TLC and RV prior to breast reduction may favor the appearance of pulmonary alter-ations.

Due to the greatrisk of pulmonary complications that patients are exposed to in the post-operative period, it wouldbehelpfultothinkofeffectivemethodstominimize thesecomplications.

One way of preventing the pulmonary complications related to bariatric surgery and other upper abdominal surgeryistheearlyonsetofrespiratorytherapy,with mon-itoringateverystageofinpatientandoutpatientsessions, includingtheuseofincentivespirometryandpositive pres-sure, whichpromotes rapid recovery oflung function and preventstheformationofatelectasis.26,28---32

Thusit wasconcludedthat48hafterbariatricsurgery, theprevalenceofatelectasisinthepopulationinquestion was37%, whichcanbeconsideredrelevant.The atelecta-siswaspredominantlyinthelungbases,andthemainrisk factorsforitsdevelopmentweretobefemaleandover36 yearsofage.

Limitations

of

the

study

Thelimitationofthisstudyisrelatedtothefactthatthere was no group of eutrophic individuals undergoing upper abdominalsurgeryinparallelwiththeobesegroup,inorder tocomparetheprevalenceofatelectasisinthesetwo pop-ulationsandtoestablishtherelativeriskinpatientswitha widerrangeofBMI.

Conflicts

of

interest

Theauthorsdeclarenoconflictsofinterest.

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