The effect of NaCl 0.9% and NaCl 0.45% on sodium, chloride, and acid–base balance in a PICU population

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www.jped.com.br

ORIGINAL

ARTICLE

The

effect

of

NaCl

0.9%

and

NaCl

0.45%

on

sodium,

chloride,

and

acid---base

balance

in

a

PICU

population

夽,夽夽

Helena

Isabel

Almeida

a,∗

_,

_Maria

_Inês

_Mascarenhas

a

_,

_Helena

_Cristina

_Loureiro

a

_,

Clara

S. Abadesso

a

_,

_Pedro

_S.

_Nunes

a

_,

_Marta

_S.

_Moniz

a

_,

_Maria

_Céu

_Machado

b

a_Pediatric_Intensive_Care_Unit,_Pediatric_Department,_Hospital_Prof._Doutor_Fernando_Fonseca_EPE,_Amadora,_Portugal b_Faculty_of_Medicine,_Universidade_de_Lisboa,_Lisbon,_Portugal

Received22August2014;accepted17December2014 Availableonline10June2015

KEYWORDS Acid---base equilibrium; Chloride; Hyponatremia; Maintenanceﬂuids; Pediatrics; Sodium Abstract

Objectives: Tostudytheeffectoftwointravenousmaintenanceﬂuidsonplasmasodium(Na), andacid---basebalanceinpediatricintensivecarepatientsduringtheﬁrst24hofhospitalization.

Methods: A prospective randomized controlled study was performed, which allocated 233 patients togroups: (A)NaCl0.9%or(B)NaCl0.45%. Patientswereaged 1dayto18 years, hadnormalelectrolyteconcentrations,andsufferedanacuteinsult(medical/surgical).Main outcomemeasured:changeinplasmasodium.Parametrictests:t-tests,ANOVA,X2_statistical signiﬁcancelevelwassetat˛=0.05.

Results: Group A(n=130):serum Naincreasedby 2.91(±3.9)mmol/Lat24h(p<0.01);2% patientshadNahigherthan150mmol/L.MeanurinaryNa:106.6(_±56.8)mmol/L.Nochange inpHat0and24h.GroupB(n=103):serumNadidnotdisplaystatisticallysigniﬁcantchanges. FifteenpercentofthepatientshadNa<135mmol/Lat24h.Thetwoﬂuidshaddifferenteffects onrespiratoryandpost-operativesituations.

Conclusions: Theuseofsaline0.9%wasassociatedwithalowerincidenceofelectrolyte dis-turbances.

夽 _Please_cite_this_article_as:_Almeida_HI,_Mascarenhas_MI,_Loureiro_HC,_Abadesso_CS,_Nunes_PS,_Moniz_MS,_et_al._The_effect_of_NaCl_0.9%

andNaCl0.45%onsodium,chloride,andacid---basebalanceinaPICUpopulation.JPediatr(RioJ).2015;91:499---505.

夽夽_Study_conducted_at_Pediatric_Intensive_Care_Unit,_Department_of_Pediatrics,_Hospital_Prof._Doutor_Fernando_Fonseca_EPE,_Amadora,

Portugal.

∗_{Corresponding}_author.

E-mail:lenaizabel@gmail.com(H.I.Almeida).

http://dx.doi.org/10.1016/j.jped.2014.12.003

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PALAVRAS-CHAVE EquilíbrioÁcido-Base; Cloreto; Hiponatremia; Fluidosde manutenc¸ão; Pediatria; Sódio

EfeitodoNaCla0,9%edoNaCla0,45%sobreosódio,cloretoeequilíbrioácido-base

emumapopulac¸ãodeUTIP

Resumo

Objetivo: Estudar o efeito de dois fluidos de manutenção intravenosos sobre o sódio (Na) plasmáticoeoequilíbrioácido-baseempacientesdeterapiaintensivapediátricaduranteas primeiras24horasdeinternação.

Métodos: Foirealizado um estudocontroladorandomizadoprospectivo.Alocamos aleatoria-mente233pacientesparaosgrupos:(A)NaCla0,9%ou(B)NaCla0,45%.Ospacientescom 1dia a18 anosde idade apresentavam concentrac¸ões normais de eletrólitose sofriam de insulto agudo (médico/cirúrgico). Principal resultado: variac¸ão no sódio plasmático. Testes paramétricos:testet,ANOVA,qui-quadrado.Onívelderelevânciaestatísticafoiestabelecido em_˛=0,05.

Resultados: GrupoA(n=130):oNaséricoaumentou2,91(±3,9)mmolL−1em24h(p<0,01); 2% dos pacientes apresentaram Na acima de 150mmolL−1. Concentração média de Na na urina: 106,6 (±56,8)mmolL−1.Sem alteração nopH em 0 e 24h. Grupo B (n=103): o Na sériconãoapresentoualterações estatisticamentesignificativas.15%dospacientes apresen-taramNa<135mmolL−1em24h.Osdoisfluidostiveramefeitosdiferentessobreassituações respiratóriaepós-operatória.

Conclusão: Ousodesoluc¸ãoﬁsiológicaa0,9%foiassociadoàmenorincidênciadedistúrbios eletrolíticos.

Introduction

The choice of maintenance ﬂuids in hospitalized patients

is an issue thatphysicians frequently have toconsider.In

the last decade, the recognition of severe complications

associatedwithexcessvolumeadministrationandiatrogenic

hyponatremiahasraisedincreasedinterestinthe

prescrip-tionofﬂuidsandonitsconsequences,especiallyincritical

careconditions.1---4

Hyponatremia is deﬁned as a concentration of plasma Nalowerthan135mmol/L.5_Nearly_all_hospitalized_patients

have the risk of developing hyponatremia as a result of the potential presence of known stimuli for producing anti-diuretic-hormone (ADH).6---9 _In _children _admitted _to_a

PICU,10---12 _many _such _stimuli _may _be _present: ₍₁₎ _those

relatedto hemodynamic status --- hypovolemiaor hyperv-olemiaand(2)thoserelatedtoinappropriate antidiuretic hormone release syndrome (IADHRS), present in central nervoussystem disturbances,pulmonarydiseases, tumors, andpostoperativeconditions.2,3,6,10---12_Until_recently,

hypo-tonic ﬂuids (0.2---0.3% saline) were used as maintenance ﬂuidsforhospitalizedchildren,basedontheHolliday---Segar equation,13,14_but_recent_studies_showed_that_hyponatremia

maybeexacerbatedbyhypotonicintravenousﬂuids.15---19

Hypernatremia,whichmaybedeﬁnedasserumNahigher than145mmol/L(althoughvaluesunder150mmol/Larenot considereddeleterious),hasalsobeenextensivelydescribed inpatientsin intensive careunits.10,11 _At _admission,_2---6%

of patients are hypernatremic, and during the course of treatment in the ICU, 4---26% of patients become hyper-natremic. Many factors may contribute to hypernatremia

in thesepatients,suchaspatientinability tocontrolfree water intake(sedated, intubated, mental statusaltered), fluidrestriction,excessivefluidlosses,andtreatmentwith Nacontainingfluids.AsPICUpatientsareatincreasedrisk of developingelectrolyte imbalance,it wouldbe relevant to identify a maintenancefluid not associated with elec-trolyticdisturbances,suitabletoadministertoawiderange ofpatients.

ThisstudycomparestheeffectsonNahomeostasisand acid---basebalance,inpatientsadmittedtothePICU,oftwo intravenousmaintenancefluids:NaCl0.9%,with154mEqNa andCl/L(FluidA),andNaCl0.45%,with75mEqNaandCl/L (FluidB),bothin5%dextrose.FluidAishypernatremicand hyperosmotic, while FluidB is hyponatremicand closeto plasma osmolarity. These are the two maintenance fluids mostusedinthis department,wherelowerNa concentra-tionintravenousfluids(includingsaline0.18%)havenotbeen usedsince2000.

Theprimaryobjectiveofthestudywastodetermineand compare theeffects at 24h onplasma Naof thetwo ﬂu-idsstudied.Otheroutcomesconsideredweretheincidence of hypernatremia and hyponatremia, urinary excretion of electrolytes,andacid---basebalance(pH,bicarbonate,base excess,totalCO2,chloride)after24hundertreatmentwith thetwomaintenanceﬂuids.

In contrast with the postoperative pediatric patient, thereisstillapaucity ofclinical trialscomparingisotonic andhypotonicﬂuidsinotherpediatricsettings,namely criti-calcarechildren.ThisstudyisusefulasitaddressesthePICU populationandincludesaspectsnotconsideredinprevious works.

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Methods

Studydesign

A prospective, randomized, open, label-controlled study

wasused,witha simplerandomizationlist.Patientswere

distributedbetweentwogroups,AandB.InGroupApatients

weretreatedwithsaline0.9%in5%dextroseasmaintenance

ﬂuid,whileinGroupBpatientsreceivedsaline0.45%in5%

dextroseasmaintenanceﬂuid.Datawerecollectedat24h.

Thestudywasterminatedwhenenteralﬂuidswere

admin-isteredataratehigherthanmL/kg/hinchildrenlessthan

10kgor10mL/hinolderchildren.

Participants

ThisstudywasconductedinasecondaryPICUwith11beds

thatadmits450patientsannually.Patientsaged1dayto18

yearsoldwereincluded,withanacuteinsult(medicalor

sur-gical),whoneededexclusiveadministrationofintravenous

ﬂuidsfor morethan24h.Patientswithsevereelectrolyte

andacid---basedisturbances,metabolicdisease,plasmaNa

lowerthan135mEq/Lorhigherthan150mEq/L,renal

insuf-ﬁciency,orwhorefusedtosign aninformedconsentwere

excludedfromthestudy.Duringthestudy,patientsinwhom

themaintenanceﬂuidwasswitched orinterrupted before

24hwereexcluded.

Interventionsandtherapeuticprotocol

Inbotharmsofthestudy,ﬂuidvolumeprotocolswerethe

same.Inpatientswithrespiratorydisease,ﬂuidrestriction

withadministrationof50---90% of thevolumeproposedby

theHolliday---Segarequationwasused.Inabdominalsurgery,

100---120% of the dailyproposed intake wasadministered.

Duringthisstudy,everyﬂuidressuscitationwasdonewith

NaCl0.9%,20mL/kgfor20---30min,whenshockorpre-shock

were detected. A daily waterbalance of zero was aimed

in this set of patients, and diuretic (furosemide), when

needed,wasadministeredtoachievethisgoal.

Datacollection,variables,andoutcomes

This study used a questionnaire designed to collect

epi-demiologic,clinical,andlaboratorydata.Variablesincluded

were:date,gender,age,weight,neonate(y/n),diagnosis,

diagnosticgroup, previous existence ofa chronic disease,

PIM2(PediatricIndexofMortality),needforﬂuidexpansion,

diuretics, volume of ﬂuids administered, urinary output,

water balance,Na, Cl, potassium, pH andbicarbonate at

T0h (prior to ﬂuid administration) and 24h, and urinary

ionogramatT24h.

Primary outcomewasthedifferencebetweenNaat T0

andT24hinmmol/L(Na24h/Na0h) withmaintenance

Fluids A and B. Secondary outcomes were: incidence of

hyper or hyponatremia, pH, bicarbonate, base excess,

tCO2andchlorideatT24h,andurinaryexcretionofNaand

Cl.

Samplesize

Inapriorpilotstudy,20 _the_present_authors_detected_a

dif-ference in serumNa of 2mmol/L after 24h using normal salineor0.45%salineinPICUpatients.For˛=0.05,apower of0.9,andanexpecteddifferenceof2mmol/LinserumNa at24h betweenthetwogroups,it wasconcludedthat66 patientswereneededin eacharm ofthestudy.Fora dif-ferencebetweenthetwovaluesof1.5mmol/L,eachgroup wouldneed117patients.

Randomization

Patientswererandomizedusingasinglesequenceofrandom

assignments,withasimplerandomizationtablebetweenthe

twoarms of the study (Fluids Aand B). The physician in

chargeofthepatientconsultedthisrandomizationtableand

assignedthechildtoGroupAorB.

Statisticalmethods

Descriptivestatisticswerecalculatedforthewholesample

andforGroupsAandB.Thedataweretestedfornormality,

asrequired by subsequentparametric statistical tests. To

analyzedifferencesinNabetweenT0andT24h(main

out-come)anddifferencesinClandacid---basebalancebetween

T0and T24 and between electrolytesin Groups A and B,

independentandpairedt-testsandANOVAwereused.The

univariateanalysisalso utilizedX2_._Statistical _{signiﬁcance}

levelwassetat 0.05.Datawereanalyzed usingSPSS

ver-sion19(SPSS,Inc.,SPSSforWindows,Version19.0,Chicago,

USA).

Ethics

Informedconsentwasobtainedfromtheparents/guardians

ofpatientsunder16yearsold,andfromadolescentsaged16

orolder.ThestudywasapprovedbytheEthicsCommittee

ofHospitalFernandoFonseca.

Results

Flowchart

During2011, 268 episodeswere included and randomized

toarm A---FluidA(n=135)orB---FluidB(n=133)ofthe

study.InGroupsA andB,5 and30episodes,respectively,

wereexcludedbecauseofmissingdataconsideredrelevant

forthestudy.Attheend,therewere130patientsinGroup

Aand103inGroupB,foratotalof233patientsanalyzed

(Fig.1).

Results

From the 233 patients included in the study, 137 were

male and 42 were neonates. Their median age was

12 months (minimum age 0.37 months, maximum 204

months).Seventy-ﬁve (33.6%) had a previous chronic

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Assessed for eligibility (n = 268)

Excluded (n = 15)

♦ Did not meet inclusion criteria (n = 15)

Analysed (n = 135)

♦Excluded from analysis (missing data) (n = 5) Lost to follow-up (give reasons) (n = 0) Discontinued intervention (give reasons) (n = 0) Allocated to intervention A (n = 135)

♦ Received allocated intervention (n = 135)

Lost to follow-up (give reasons) (n = 0) Discontinued intervention (change of maintenance fluid before 24h) (n = 15) Allocated to intervention B (n = 133)

♦ Received allocated intervention (n = 133)

♦ Did not receive allocated intervention (n = 0)

Analysed (n = 118)

♦ Excluded from analysis (missing data) (n = 15) Allocation Analysis Follow-up Randomized (n = 253) Enrollment

Figure1 Studyﬂowchart.CONSORT2010ﬂowchart.

onewereadmittedforarespiratoryproblem,65aftermajor

surgery,24forshock,and23hadmiscellaneousconditions.

Fifty-threepatientsweremechanicallyventilated.

Fluid volume aimed for a daily balance of 0 and

var-iedbetween 24% (respiratory patient)and 193% (surgical

patient)ofbasalﬂuidrequirements,withameanof91.0%.

Dailywaterbalancehadameanof+2.4mL,withastandard

deviation of388mL.The median was+125mL, with

mini-mumof−688andmaximumof2066mL.Meanandmedian

urine output were,respectively, 2.15mL/kg/h (±1.6) and

1.7mL/kg/h (min 0.25, max 10.5). Fifty-one had

hemo-dynamic instability. Volume expansion was needed in 43

Table1 EmographicandclinicalcharacterizationofGroupsAandB.

GroupA(n=130) GroupB(n=103) p

Gender

Male(%) 80(62%) 53(57%) 0.28

Female(%) 48(38%) 44(43%)

Meanage(months)(SD) 49.9(SD±62.5) 41.1(SD±64.4) 0.22

Chronicdisease(%) 38(29.7%) 39(40.2%) 0.1 Mechanicalventilation(%) 31(23.8%) 22(21.4%) 0.79 Waterbalanceat24h(mL) 252.2(SD_±330.7) 244.7(SD_±440.6) 0.73 Na+_at_T0_h _138.1_(SD_±_4.30) _137.7_(SD_±_3.09) _0.72 Cl−atT0h 103.7(SD_±4.50) 102.4(SD_±4.14) 0.59 pHatT0h 7.34(SD±0.093) 7.34(SD±0.097) 0.78 HCO3atT0h 24.8(SD±3.99) 24.9(SD±4.47) 0.43

Dailyﬂuid(%basicneeds) 90.8%(SD±18.9) 91.5%(SD±28.6) 0.12

Diuretics 63/128(49%) 40/94(42.5%) 0.15

Fluidresuscitation 22/128(17.2%) 11/91(12.1%) 0.16

NaCl0.9%(20---30mL/kg)

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Table2 Sodium,pH,andtCO2variationbetweenGroups AandB. GroupA (n=130) GroupB (n=103) p Na+ _2.89_±_4.0 _0.32_±_3.8 _0.00 pH 0.02±0.07 0.05±0.10 0.20 tCO2 1.58±3.6 1.34±2.8 0.81

patients,diureticsin105,bloodproductsin35,and

inotrop-icsin30.PlasmaNa,Cl,pH,andurinaryNaandClatT0and

T24areshowninTable1.

The 35patientsexcluded fromthestudyhadamedian age of 13 months,19 were male, and theirmean sodium was137.9mmol/L.

ComparisonofeffectsofFluidsAandB

Descriptive statistics show that both groups were similar

regarding age, gender, chronic disease, PIM2, diagnostic

groups,mechanicalventilation,Na,Cl,pHatthebeginning

ofthestudy,waterbalance,volumeadministered,andurine

output.Useofdiureticsandvolumeexpansionwere

statis-tically similarin bothgroups (Table1). Basedonthis, the

effectsofbothﬂuids(AandB)onNaandpHbalancewere compared(Table2).

EffectsonNa

GroupA---NaCl0.9%(n=130)

Using Fluid A, serum Na increased from 138.1mmol/L

(±4.3)attimeT0to140.9mmol/L(±4.9)atT24h,witha

meanincreaseof2.9mmol/L(±3.9)(p<0.01).Tenpatients

(5%) had Na higher than 145mmol/L and three of them

hadsodiumhigherthan150mmol/L (151.4;152.6;155.0).

This corresponds to an attributable risk of 2%. Seven

patients in this group had hyponatremia, with Na higher

than 130mmol/L. Urinary Na in this group had a mean

of 106.6mmol/L (±56.8). Clinical symptomatologydue to

hypernatremiaorhyponatremiawasnotregistered.

GroupB---NaCl0.45%(n=103)

WithFluidB,atT0,serumNawas137.86mmol/L(±3.1),and

at T24,137.81mmol/L (±3.0), witha meandifferenceof

−0.2mmol/L,whichwasnotstatisticallysigniﬁcant.

Four-teenpatients hadNavaluesunder135mmol/L(130---134).

Inthese14patients,thedifferencesinNabetweenT0and

T24variedfrom0.5to−10mmol/Landcorrespondedtoan

attributablerisk of15%. None ofthesepatients had

clini-calsignsofhyponatremia.Twopatientshadhypernatremia

(Naof146.5and147mmol/L).UrinaryNainthisgrouphad

a meanof 81.8mmol/L (±5.0), and thisvalue was

statis-ticallysigniﬁcantlydifferentfromtheNaurinaryexcretion

withFluidA(p=0.04).

Effectofbothﬂuidsonacid---basebalance

HCO3 pH, totalcontent inCO2 andbase excess increased

inbothgroups fromT0toT24.Therewerenostatistically

signiﬁcant differences using these maintenance ﬂuids.

Saline0.9%andsaline0.45%increasedthetotalCO2at24h

(Table2).

Fluid A increased serum Cl levels from 104.0mmol/L (±4.7) to106.7mmol/L (±6.7) (p<0.01).FluidBchanged the initial Cl from 102.7mmol/L (±4.2) to 102.3mmol/L (±6.1);thiswasnotasigniﬁcantdifference(Table2).

Neonates(n=42)

Based on different physiologic knowledge, neonates are

expectedtobehavedifferentlyfromolderchildrenin

rela-tion to electrolyte balance. This study observed those

aspectsandconcludedthatneonatesinGroupAhadgreater

increasesinNaserumconcentration(5.0±4.6mmol/L

ver-sus 2.5±3.8mmol/L in older children) at 24h, and one

neonatehadaplasmaNalevelof152.6mmol/L.InGroupB,

nodifferencesweredetectedintheseparametersbetween

neonates and older children. No differences were seen

betweenneonatesandchildreninrelationtourinary

elec-trolyteexcretionandurinaryoutput.

Respiratoryandpost-operatorypatients

Differences were detected between major diagnostic

groups,assubsequentlyexplained(Table3).

Respiratorygroup(n=121)

When using Fluid A (n=63), the Na plasma

concentra-tion increased by 3.42mmol/L (±4.2), and decreased by

0.3mmol/L (±3.6) when using FluidB (n=58) (p<0.001).

Urinary excretion withFluid A was104.3mmol/L (±49.3)

and84.8mmol/L(±49.8)withFluidB,withnostatistically

differencebetweenthesevalues.

Post-operativegroup(n=65)

In post-operative patients, urinary excretion of Na was

141.6mmol/L(±69.7)withFluidA(n=33)and59.5mmol/L

(±39.4) with Fluid B (n=20), p<0.001. The differences

in serum Na when using Fluids A or B were not

statis-tically signiﬁcant. In this group of patients, electrolyte

urinary excretion was signiﬁcantly different between the

twogroups, andthe differencein serumelectrolytes was

notstatisticallysigniﬁcant.

Discussion

Saline 0.9% was compared to saline 0.45%. The risk of

hypernatremiausingsaline0.9%wassigniﬁcantlylower(2%)

thantheriskofhyponatremiausingsaline0.45%(15%),and

hyponatremiais arelevant issue inintensive care units.21

BothﬂuidsinducedmarkedurinaryexcretionofNa. Sabaetal.,22_in_their_clinical_trial_with₃₆_children,

com-paredtheuse of normal salineto saline0.45% and found thatthe differencebetweenthe change in Na concentra-tionwas notsigniﬁcant. They did notanalyze changes in pHorchlorideconcentrations,northeurinaryexcretionof electrolytes.

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Table3 Differencesinelectrolytesvariationbetweendiagnosticgroups:respiratoryandpost-surgical.

Diagnostic group

0.9%Saline(A) 0.45%Saline(B)

Na+ _U_Na+ _Cl− _U_Cl− _Na+ _U_Na+ _Cl− _U_Cl− Respiratory, mmol/L (n=121) 3.42(_±4.2) 104.3(_±49.3) 2.7(_±5.1) 134.6(_±51.5) _−0.3(_±3.6) 84.8(_±49.8) _−1.7(_±5.6) 108.1(_±55.4) Post-surgical, mmol/L (n=63) 1.6(±2.7) 141.6(±69.7) 0.8(±6.2) 168.3(±78.5) −0.02(±5.1) 59.5(±39.4) 1.6(±4.1) 95.8(±47.0)

Reyetal.,12_in_a_prospective_randomized_study,_compared

theutilizationoffluidswith30---50mmol/LNatofluidswith 136mmol/L Na in a group of 134 ICU patients. They also concludedthathypotonicfluidsincreasedtheriskof hypona-tremia. They described only one case of hypernatremia with normal saline. In the present study hypernatremia wasdetected in three patients, which corresponds to an attributableriskof2%.Thisdiscrepancymaybedueto dif-ferentclinicaland therapeutic situationsbetween studies (differenthemodynamic status), although theywere both conductedinPICUs.

Yung and Keeley23 _compared _normal _saline _with _0.18%

salinein aPICU population, concludingthatboth mainte-nanceﬂuidswererelatedwithhyponatremia.Theirsample wassmallerandinsomeaspectsdifferentfromthe popula-tionstudiedinthisstudy:mostofthepatientsweresurgical, mildlyill,andnotventilated.TheyalsostudiedtheNa uri-nary output, which wassimilar in both groups and lower thanthatofthepresentsample.Inthepresent study,the hypotonicﬂuidstudiedalsoinducedhyponatremia.

There are studies including only post-operative patients24---26_: _Choong _et _al.24 _conducted _a _randomized

controlledtrialincluding258patients(someofthem admit-ted to the PICU) comparing 0.45% saline to 0.9% saline. The 0.9% ﬂuid proved to be less deleterious. Coulthard etal.26_compared_the_effects_on_plasma_sodium_at_16---18_h

ofHartmann’ssolutionand5%dextroseor0.45%salineand 5% dextrose in 82 patients following major surgery; they concludedthatthepostoperativefallinNawassmallerin childrenwhoreceivedHartmann’ssolutionand5%dextrose. Thepresentresultsagreewiththeseconclusions.

Effectsonacid---basebalancewerealsoregarded.Saline 0.9%,whenusedinlargevolumes,isknowntocause hyper-chloremicmetabolicacidosis27_;_based_on_these_results_it_is

possibletoconcludethatwhenusedasmaintenanceﬂuid, saline0.9%orsaline0.45%didnothavethateffect,although bothﬂuidsincreasedthetotalCO2.

In this sample of 233 acutely ill medical and surgical patients,0.45%normalsalineinducedhyponatremiain15% ofthepatients, andnone ofthe fluidsinduced significant changesinacid---basebalance.Theseresultsstrengthenthe choiceofanisonatremicmaintenancefluidinthisgroupof patients.

This study has several strengths beyond the size of the sample. To the authors’ knowledge, no other stud-iesfocused onthe effectof maintenance ﬂuidson serum Cl concentrations or acid---base balance. In this study, no effects on acid---base balance were seen with the use of the two different ﬂuids. Individualizing twodiagnostic

groups (respiratory and postoperative) showed different effectsonNaandClconcentrations.Thisraisesthe possibil-ityof interferenceof differenthormonalor multifactorial mechanisms. Postoperative patients excreted higher con-centrations of Na and Cl, which may be related to ADH secretion.McCluskeyetal.28 _showed_that_in_adult

noncar-diac surgery, hyperchloremia is associated with mortality andlongerhospitalization.

Certainlimitationsinherenttothisstudymustbe recog-nized: 35patients wereexcluded(5 fromGroupA and30 from Group B)due tomissing data or interruption of the study;demonstratingthatthetwogroupsstudiedwere sim-ilaratthebeginningofthestudy,andthatthe35patients excludedhadthesameepidemiologiccharacteristicsasthe 233patientsincludedattenuatesthislimitation.

Withthisprospectivecontrolledrandomizedstudy,ithas been observed that although both saline 0.9% and saline 0.45% may be usedin a PICU during 24h asmaintenance fluids,normalsalineshouldbepreferred,asitwasableto increaseplasmaNa,incontrastto0.45%saline,whichwas associated witharelevant risk ofhyponatremia. No clini-calsignsofhypernatremiaorhyponatremiaweredetected. Noneofthefluidsinducedhyperchloremicmetabolic acido-sis.The studyshows thattheprescription ofmaintenance fluids must take into account age, diagnosis, fluid bal-ance, andtheuseofdiuretics orexpansionfluids. Studies addressingthesedifferentvariablesneedtobeperformed. TheuseofbalancedfluidslikeRinger’slactateorother poly-electrolytesolutionsneedstobestudied,astheymayhave substantialclinicaladvantagesinrelationtoNaClfluids.

Conﬂicts

of

interest

Theauthorsdeclarenoconﬂictsofinterest.

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