Fluid and Electrolyte Therapy in the Pediatric Patient：流體和電解質(zhì)在兒科病人的治療

FluidandElectrolyteTherapyinthePediatricPatientStevePiecuchMD,MPHDepartmentofPediatricsLincolnMedicalCenter

MaintenanceRequirementsIntroductiontothePrinciplesofFluidandElectrolyteTherapyImportanttounderstandtheunderlyingphysiologicprinciplesofatherapycommonlyemployedinpediatricsUnderstandingbasicprinciplesessentialfortheunderstandingofthemanagementofmorecomplexdisorderssuchas:CholeraDenguePyloricstenosisDKAHyperosmoticnon-ketoticcomaCrystalloidandColloidCrystalloid:Waterandelectrolytesolution DoesnotremainwithintheintravascularspacebutratherdistributestotheentireextracellularspaceOnlyimpactsontheintracellularspaceifitcausesachangeinextracellularosmolarityE.g.:0.9%NaCl,D50.3%NaClColloid:ContainslargeparticleswhichtendtoremainwithinthebloodvesselsColloidpreferentiallyexpandstheintravascularspacebecausetheparticlesexertoncoticforcewhichretainswaterwithintheintravascularspaceE.g.:5%albumin,blood,dextransolutionIsotonicSalineSolutionIsotonicsalinesolution:Solutionsuchas0.9%NaClorRinger’slactatewithaNaconcentrationsimilartothatofplasmawaterCrystalloiddistributesthroughouttheextracellularspaceInfusionofcrystalloidwillcauseafluidshiftintooroutoftheintracellularspaceonlyifitcreatesanosmoticgradientbetweentheextracellularandintracellularspaceIsotonicsalinedoesnotchangetheosmolarityoftheextracellularspaceTherefore:IsotonicsalinesolutionremainswithinandexpandstheextracellularspaceandhasminimaleffectontheintracellularspaceMaintenanceFluidandElectrolyteRequirementsMaintenance:ThereplacementofnormalongoinglossesNormallyserumNaconcentrationisapproximately140meq/landserumKconcentrationisapproximately4meq/lMaintenancesolutionreplacesnormallossesMaintenancesolutiondoesnothaveanelectrolyteconcentrationequaltoserumbecausetheelectrolytecompositionofurineandstoolisnotequaltothatofserumMaintenancefluidscommonlyprovidedasa5%dextrosesolutionDextroseprovidessomeenergyandpreventshypoglycemiaSparesproteinCannotmeetpatient’snutritionalrequirementswith5%(or10%)dextroseMaintenanceRequirementsareaFunctionofCaloricRequirements0-10kg: 100kcal/kg10-20kg: 50kcal/kg>20kg: 20kcal/kgExamples:8kg:8kgX100kcal/kg=800kcal.12kg:10kgX100kcal/kg+2kgX50kcal/kg=1000kcal+100kcal=1100kcal20kg:10kgX100kcal/kg+10kgX50kcal/kg=1000kcal+500kcal=1500kcal25kg:10kgX100kcal/kg+10kgX50kcal/kg+5kgX20kcal/kg=1000kcal+500kcal+100kcal=1600kcalWaterandElectrolyteRequirementsareDeterminedbyCaloricRequirementsRequirementsper100kcal:100mlwater(providedasa5%dextrosesolution)2-4meqNa2meqK2meqClPlasma:AnionisabalanceofClandbase(bicarbonate)Maintenancesolution:CanprovidesomeanionasClandsomeasbase(lactate,citrate,phosphate)orcanprovideallofitasClBut:Providinglargevolumesoffluid(e.g.,inDKAorhypovolemicshock)withalloftheanionasClwillpromoteahyperchloremicmetabolicacidosisStandardMaintenanceSolutionD5Wwith20-40meq/lNaCland20meq/lKCl(orKAcetateorKPhosphate)willworkwellasamaintenancesolutioninmostpediatricpatientsCanuseD50.2%(orD50.3%)NaClwith20meq/lKCl(orKAcetateorKPhosphate)asmaintenancesolutionRecentarticleadvocatedroutineuseofisotonicsalinesolutionforpediatricmaintenancesolution

Somediseasestates:AnothersolutionmightbeappropriateE.g.:SicklecellanemiapatientsmayhavearelativelyhighNarequirementduetohighurinaryNalosses0.9%NaCl(withoutdextrose)inheadtraumapatientsKshouldbeusedwithcautionoromittedinpatientswithrenalinsufficiencyWaterandElectrolyteRequirementsBasedonWeightWater:0-10kg:100ml/kg10-20kg:1000mlplus50ml/kg>20kg:1500mlplus20ml/kgElectrolytes:Na:2-3meq/kgK:1-2meq/kgWaterrequirementisthesameaswiththecaloric-basedsystemElectrolyterequirementisgreaterthanwithcaloric-basedsystem:ElectrolyterequirementisadirectlinearfunctionofweightRoutineUseofD50.45%NaClasMaintenanceSolutioninOlderPatientsCalculatewaterandelectrolyterequirementsonaper100kcalbasis:RelationshipbetweenwaterandelectrolyterequirementsisfixedanddoesnotchangeasweightincreasesBut:Ifthewaterrequirementiscalculatedonaper100kcalbasisandtheNarequirementiscalculatedonaperkgbasis,thenasthepatient’sweightincreasestheNarequirementwillincreaseatagreaterratethanthewaterrequirementHeavierchildrenwillrequireamaintenancesolutionwithahigherNaconcentrationWhy:Becausethewaterrequirementdoesnotincreaselinearlyasweightincreases:AsweightincreasesthewaterrequirementasexpressedonaperkgbasisdecreasesRoutineUseofD50.45%NaClasMaintenanceSolution(Continued)ConsiderNaconcentrationofmaintenancesolutionifestimateNarequirementtobe3meq/kg(not2-4meq/100kcal)10kg: 30meqNain1000ml:30meq/l:20kg: 60meqNain1500ml:40meq/l40kg: 120meqNain1900ml:63meq/l70kg: 210meqNain2500ml:84meq/lThisexplainswhycommerciallyavailablemaintenancesolutionsexistwhicharedesignedforchildrenbelowandaboveaspecificweightRememberdiscussionaboutprovidingsomeanionasbase:ThisexplainswhycommercialsolutionsmaycontainsomeanionintheformoflactateorcitrateDehydrationDehydrationGoodworkingdefinitioninpediatrics:Lossofbodyfluid,usuallypredominantlyfromtheextracellularspace,duetodecreasedintakeand/orincreasedlossesMostcommoncauseisprobablyacutegastroenteritisFailuretoreplacefluidslostfromostomiesanddrainswithanappropriatesolutionmaycausesignificantelectrolyteimbalanceanddehydrationPatientswithapparentlyacceptableintakemaydevelopsignificantfluidandelectrolyteimbalancesE.g.:InfantwithaventriculardrainwillloseasignificantamountofNaintheventricularfluidSuchaninfantmaydevelopseverehyponatremiaifexclusivelyfedhumanmilk(lowNa)ClassifyDehydrationastoTypeIsonatremicdehydration:SerumNabetween130meq/land150meq/lHyponatremicdehydration:SerumNa<130meq/lHypernatremicdehydration:SerumNa>150meq/lSerumNaandosmolarityHypernatremicpatientsarealwayshyperosmolarIsonatremicpatientsarenotalwaysisoosmolarE.g.:SerumNa140meq/landglucose600mg/dlHyponatremicpatientsarenotalwayshypoosmolarE.g.:SerumNa129meq/landglucose800mg/dlNote:IsonatremicorhypernatremicpatientwithnormalglucosemaybehyperosmolarduetomannitolOngoingAbnormalLossesMaintenancesolutionisdesignedtoreplaceongoingnormallossesOngoingabnormallosses:Diarrhea,ostomydrainage,chesttubedrainage,ventricularfluiddrainagePossibletomeasureelectrolytesinthefluidbutisusuallyunnecessaryMaybeusefulifthereisalargevolumeofdrainageaccompaniedbysignificantelectrolyteimbalanceNasogasricdrainage:0.45%(or0.9%)NaClwith20-40meq/lKClIleostomydrainage:0.9%NaClwith10-20meq/lKClorKAcetateClinicalFindingsinDehydrationHistory:Refusaltofeed,vomiting,diarrhea,decreasedurineoutputIncreasedrisk:Childrenwithdefectivethirstmechanism,DI,impairedaccesstowaterPhysical:Sunkenfontanel,decreasedtears,decreasedskinturgor,tachycardia,weakpulses,coolextremitiesHypotensionisalatefindingwhichoccursonlyaftercompensatorymechanismshavefailedLaboratory:Metabolicacidosis,increasedBUN,increasedcreatinine,increasedurinespecificgravityClassifyDehydrationastoSeverityMild:Earliestsignsofdehydration30-50ml/kgdeficit(3-5%dehydration)Moderate:Signsofdehydrationmorepronounced60-100ml/kgdeficit(6-10%)Severe:Impendingoractualcirculatoryfailure90-150ml/kgdeficit(9-15%)Smallerchildren(e.g.,<2yearsold)use5%-10%-15%dehydrationInlargerchildren(e.g.,>2yearsold)use3%-6%-9%ratherthan5%-10%-15%toavoidprovidingexcessivevolumesoffluidAlternativeapproach:IVrateofoneandahalfmaintenanceformildtomoderatedehydrationandtwicemaintenanceformoderatetoseveredehydrationSeverity(Continued)Canuseweightchangetoestimatethevolumeofthedeficitifthechangeisrecent(i.e.,over24hours)andyouareconfidentthattheweightsarereliableRecentweightlossimpliespredominantlyawaterlossDegreeofdehydrationisanestimate,notprecise(analogoustoavisualestimateofserumbilirubin)InitiallyunderestimatingthedegreeofdehydrationisnotharmfulsolongasanyexistingorimpendingcirculatoryfailureisrecognizedandtreatedappropriatelyInitiallyoverestimatingthedegreeofdehydrationisnotharmfulsolongastheoverestimateisrecognizedandthefluidregimenisappropriatelyadjustedIsonatremicDehydrationTraditionalManagementofIsonatremicDehydration24hourrepair:Providethedeficitandoneday’smaintenanceovera24hourperiodGivehalfthetotalinthefirst8hoursVolumeoffluidgivenduringanemergencyphase(i.e.,bolus)isincludedaspartofthefirst8hour’sfluidsThesecondhalfisgivenovertheremaining16hoursEmergencyphase:Oneormore20ml/kgbolusesof0.9%NaClinmoderatetoseveredehydrationRepairsolution:MaintenanceanddeficitrequirementscombinedInisonatremicdehydrationcanuseD50.45%(or0.3%)NaClwith20meq/lKCl(orKAcetate)RepairofIsonatremicDehydration(Example)21kgpatientwith10%dehydrationTotal24hourrequirement:3620mlMaintenance:1520mlDeficit:2100ml1810mlinfirst8hourand1810mlinnext16hoursEmergencyphase:2isotonicsalinebolusesforatotalof40ml/kg(840ml)over1hourRepairsolution:D50.45%NaClwith20meq/lKCl1810ml–840ml:970mlovernext7hours:139ml/hr1810mlinnext16hours:113ml/hrRepairSolutioninIsonatremicDehydration:AssumptionsDeficitisprimarilyfromtheextracellularspaceSerumNaconcentrationunchanged:ThereforethedeficitmusthaveNaconcentrationapproximatelyequaltothatofplasmawater:150meq/lNaconcentrationofplasmawaterishigherthanthatofserumbecauseserumcontainssolidssuchasalbuminwhichreducetheNaconcentrationIgnorecomponentofthedeficitwhichconsistsofintracellularfluidwithalowNaandahighKconcentrationIgnoremaintenanceelectrolyterequirementsbecausetheyarerelativelyinsignificantcomparedwiththedeficitelectrolyterequirementsSomeauthoritiesincludethemaintenanceelectrolytesintheircalculationsRepairSolutioninIsonatremicDehydration(Continued)10kgpatientwith5%dehydration:Maintenance:1000mlwaterDeficit:500mlwaterand75meqNa1500mlwaterand75meqNa:0.3%NaCl10kgpatientwith10%dehydration:Maintenance:1000mlwaterDeficit:1000mlwaterand150meqNa2000mlwaterand150meqNa:0.45%NaClRemember:NadeficitexistsandmustbereplacedinisonatremicdehydrationeventhoughserumNaisnormalNadeficit:NacomponentoftheisotonicvolumelossRepairSolutioninIsonatremicDehydration(Continued)D50.45%(orD50.3%)NaClwith20meq/lKClorKAcetateworkswellasarepairsolutionTheNarequirementisdeterminedbythedeficitThegreaterthedeficitrelativetothemaintenancerequirements,thegreatertheNaconcentrationneedstobeModeratetoseveredehydration:D50.45%NaClpreferredoverD50.3%NaClChronicdehydrationassociatedwithasignificantintracellularloss:Somepatientsmaydevelophypokalemiaandrequire30-40meq/lofKintherepairsolutionActualCalculations:ModifiedFinbergTechniqueExample:12kgpatientwith10%isonatremicdehydrationMaintenancevolume:1100mlDeficitvolume:1200mlDeficitNa:1.2litersX150meq/l=180meqRepairthedehydration:Give2300mlofwaterand180meqofNaovera24hourperiodTechnique:Givehalfoverfirst8hoursandtheremainderoverthenext16hoursGive20ml/kgisotonicsalinebolusifhavedeficit>10%ModifiedFinbergTechnique(Continued)12kgpatientwith10%dehydration:Require2300mlofwaterand180meqofNaovera24hourperiodEmergencyphase:20ml/kgX12kg=240mlof0.9%NaCl240mlofwater37meqofNaRepairsolutionWater:2300ml-240ml=2060mlNa:180meq-37meq=143meq2060mlofwaterwith143meqofNa5%dextrosesolutionwith69meq/lofNaGive1150mloverfirst8hoursand1150mloverfollowing16hours1150ml–240ml(bolus)=910ml910ml/8hr=113.8ml/hr1150ml/16hr=71.8ml/hrSummarize:12kgpatientwith10%IsonatremicDehydrationEmergencyphase:20ml/kgofisotonicsaline240mlof0.9%NaClDextrosefreefluidbolus:CorrecthypoglycemiaseparatelyifnecessaryRepairsolution:5%dextrosesolutionwith69meq/lofNaD50.45%NaClcloseenough(77meq/lNa)Repairsolutionshouldinclude20-40meq/lofKtomeetKneedsandtoreplaceanyintracellulardeficitFirst8hours:2300ml/2=1150ml-240ml=910ml/8hr=114ml/hrSubsequent18hours:1150ml/16hours=72ml/hrAlternativeApproachestotheRepairofIsonatremicDehydrationGivemaintenanceevenlyover24hoursbutgivehalfthedeficitoverthefirst8hoursandtherestofthedeficitoverthenext16hoursComplicated:EitherusedifferentIVbagsforthemaintenanceanddeficitfluidsorchangetheelectrolytecompositionoftherepairsolutionafterthefirst8hoursEstimatingrelativecontributionsof