ICU必备课件1课件.ppt

ICU必备课件1课件.ppt

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ABGINTERPRETATION,DebbieSanderPAS-II,Objectives,WhatsanABG?

UnderstandingAcid/BaseRelationshipGeneralapproachtoABGInterpretationClinicalcausesAbnormalABGsCasestudiesTakehome,WhatisanABG,ArterialBloodGasDrawnfromartery-radial,brachial,femoralItisaninvasiveprocedure.Cautionmustbetakenwithpatientonanticoagulants.Helpsdifferentiateoxygendeficienciesfromprimaryventilatorydeficienciesfromprimarymetabolicacid-baseabnormalities,WhatIsAnABG?

pHH+PCO2PartialpressureCO2PO2PartialpressureO2HCO3BicarbonateBEBaseexcessSaO2OxygenSaturation,Acid/BaseRelationship,ThisrelationshipiscriticalforhomeostasisSignificantdeviationsfromnormalpHrangesarepoorlytoleratedandmaybelifethreateningAchievedbyRespiratoryandRenalsystems,CaseStudyNo.1,60y/omalecomesERc/oSOB.Tachypneic,tachycardic,diaphoreticandCyanotic.Dxacuteresp.failureandABGsShowPaCO2wellbelownl,pHabovenl,PaO2isverylow.ThebloodgasdocumentResp.failureduetoprimaryO2problem.,CaseStudyNo.2,60y/omalecomesERc/oSOB.Tachypneic,tachycardic,diaphoreticandCyanotic.Dxacuteresp.failureandABGsShowPaCO2veryhigh,lowpHandPaO2ismoderatelylow.ThebloodgasdocumentResp.failureduetoprimarilyventilatoryinsufficiency.,TherearetwobuffersthatworkinpairsH2CO3NaHCO3CarbonicacidbasebicarbonateThesebuffersarelinkedtotherespiratoryandrenalcompensatorysystem,Buffers,RespiratoryComponent,functionofthelungsCarbonicacidH2CO3Approximately98%normalmetabolitesareintheformofCO2CO2+H2OH2CO3excessCO2exhaledbythelungs,MetabolicComponent,FunctionofthekidneysbasebicarbonateNaHCO3ProcessofkidneysexcretingH+intotheurineandreabsorbingHCO3-intothebloodfromtherenaltubules1）activeexchangeNa+forH+betweenthetubularcellsandglomerularfiltrate2）carbonicanhydraseisanenzymethataccelerateshydration/dehydrationCO2inrenalepithelialcells,H2O+CO2H2CO3HCO3+H+,Acid/BaseRelationship,NormalABGvalues,pH7.357.45PCO23545mmHgPO280100mmHgHCO32226mmol/LBE-2-+2SaO295%,AcidosisAlkalosis,pH45HCO322,pH7.45PCO226,RespiratoryAcidosis,ThinkofCO2asanacidfailureofthelungstoexhaleadequateCO2pH45CO2+H2CO3pH,CausesofRespiratoryAcidosis,emphysemadrugoverdosenarcosisrespiratoryarrestairwayobstruction,MetabolicAcidosis,failureofkidneyfunctionbloodHCO3whichresultsinavailabilityofrenaltubularHCO3forH+excretionpH7.35HCO322,CausesofMetabolicAcidosis,renalfailurediabeticketoacidosislacticacidosisexcessivediarrheacardiacarrest,RespiratoryAlkalosis,toomuchCO2exhaled（hyperventilation）PCO2,H2CO3insufficiency=pHpH7.45PCO235,CausesofRespiratoryAlkalosis,hyperventilationpanicd/opainpregnancyacuteanemiasalicylateoverdose,MetabolicAlkalosis,plasmabicarbonatepH7.45HCO326,CausesofMetabolicAlkalosis,lossacidfromstomachorkidneyhypokalemiaexcessivealkaliintake,HowtoAnalyzeanABG,PO2NL=80100mmHg2.pHNL=7.357.45Acidotic7.45PCO2NL=3545mmHgAcidotic45Alkalotic26,Four-stepABGInterpretation,Step1:

ExaminePaO2&SaO2DetermineoxygenstatusLowPaO2（80mmHg）&SaO2meanshypoxiaNL/elevatedoxygenmeansadequateoxygenation,Step2:

pHacidosis7.45,Four-stepABGInterpretation,Step3:

studyPaCO2&HCO3respiratoryirregularityifPaCO2abnl&HCO3NLmetabolicirregularityifHCO3abnl&PaCO2NL,Four-stepABGInterpretation,Step4:

DetermineifthereisacompensatorymechanismworkingtotrytocorrectthepH.ie:

ifhaveprimaryrespiratoryacidosiswillhaveincreasedPaCO2anddecreasedpH.CompensationoccurswhenthekidneysretainHCO3.,Four-stepABGInterpretation,PaCO2pHRelationship,807.20607.30407.40307.50207.60,Compensated,Respiratory,Acidosis,CO2,MoreAbnormal,Respiratory,Acidosis,CO2,Expected,Mixed,Respiratory,Metabolic,Acidosis,CO2,LessAbnormal,CO2Change,c/w,Abnormality,Metabolic,MetabolicAcidosis,CO2,Normal,Compensated,Metabolic,Acidosis,CO2Change,opposes,Abnormality,Acidosis,ABGInterpretation,Compensated,Respiratory,Alkalosis,CO2,MoreAbnormal,Respiratory,Alkalosis,CO2,Expected,Mixed,Respiratory,Metabolic,Alkalosis,CO2,LessAbnormal,CO2Change,c/w,Abnormality,Metabolic,Alkalosis,CO2,Normal,Compensated,Metabolic,Alkalosis,CO2Change,opposes,Abnormality,Alkalosis,ABGInterpretation,RespiratoryAcidosis,pH7.30PaCO260HCO326,RespiratoryAlkalosis,pH7.50PaCO230HCO322,MetabolicAcidosis,pH7.30PaCO240HCO315,MetabolicAlkalosis,pH7.50PCO240HCO330,Whatarethecompensations?

RespiratoryacidosismetabolicalkalosisRespiratoryalkalosismetabolicacidosisInrespiratoryconditions,therefore,thekidneyswillattempttocompensateandvisaversa.Inchronicrespiratoryacidosis（COPD）thekidneysincreasetheeliminationofH+andabsorbmoreHCO3.TheABGwillShowNLpH,CO2andHCO3.Bufferskickinwithinminutes.Respiratorycompensationisrapidandstartswithinminutesandcompletewithin24hours.Kidneycompensationtakeshoursandupto5days.,MixedAcid-BaseAbnormalities,CaseStudyNo.3:

56yoneurologicdzrequiredventilatorsupportforseveralweeks.SheseemedmostcomfortablewhenhyperventilatedtoPaCO228-30mmHg.Sherequireddailydosesoflasixtoassureadequateurineoutputandreceived40mmol/LIVK+eachday.On10thdayofICUherABGon24%oxygen&VS:

ABGResults,pH7.62BP115/80mmHgPCO230mmHgPulse88/minPO285mmHgRR10/minHCO330mmol/LVT1000mlBE10mmol/LMV10LK+2.5mmol/L,Interpretation:

Acutealveolarhyperventilation（resp.alkalosis）andmetabolicalkalosiswithcorrectedhypoxemia.,CasestudyNo.4,27yoretardedwithinsulin-dependentDMarrivedatERfromtheinstitutionwherehelived.OnroomairABG&VS:

pH7.15BP180/110mmHgPCO222mmHgPulse130/minPO292mmHgRR40/minHCO39mmol/LVT800mlBE-30mmol/LMV32L,Interpretation:

Partlycompensatedmetabolicacidosis.,CasestudyNo.5,74yowithhxchronicrenalfailureandchronicdiuretictherapywasadmittedtoICUcomatoseandseverelydehydrated.On40%oxygenherABG&VS:

pH7.52BP130/90mmHgPCO255mmHgPulse120/minPO292mmHgRR25/minHCO342mmol/LVT150mlBE17mmol/LMV3.75L,Interpretation:

Partlycompensatedmetabolicalkalosiswithcorrectedhypoxemia.,CasestudyNo.6,43yoarrivesinER20minutesafteraMVAinwhichheinjuredhisfaceonthedashboard.Heisagitated,hasmottled,coldandclammyskinandhasobviouspartialairwayobstruction.Anoxygenmaskat10Lisplacedonhisface.ABG&VS:

pH7.10BP150/110mmHgPCO260mmHgPulse150/minPO2125mmHgRR45/minHCO318mmol/LVT?

mlBE-15mmol/LMV?

L.,Interpretation:

Acuteventilatoryfailure（resp.acidosis）andacutemetabolicacidosiswithcorrectedhypoxemia,CasestudyNo.7,17yo,48kgwithknowninsulin-dependentDMcametoERwithKussmaulbreathingandirregularpulse.RoomairABG&VS:

pH7.05BP140/90mmHgPCO212mmHgPulse118/minPO2108mmHgRR40/minHCO35mmol/LVT1200mlBE-30mmol/LMV48L,Interpretation:

Severepartlycompensatedmetabolicacidosiswithouthypoxemia.,CaseNo.7contd,Thispatientisindiabeticketoacidosis.IVglucoseandinsulinwereimmediatelyadministered.AjudgementwasmadethatsevereacidemiawasadverselyaffectingCVfunctionandbicarbwaselectedtorestorepHto7.20.Bicarbadministrationcalculation:

BasedeficitXweight（kg）430X48=360mmol/LAdmin1/2over15min&4repeatABG,CaseNo.7contd,ABGresultafterbicarb:

pH7.27BP130/80mmHgPCO225mmHgPulse100/minPO292mmHgRR22/minHCO311mmol/LVT600mlBE-14mmol/LMV13.2L,CasestudyNo.8,47yowasinPACUfor3hourss/pcholecystectomy.Shehadbeenon40%oxygenandABG&VS:

pH7.44BP130/90mmHgPCO232mmHgPulse95/min,regularPO2121mmHgRR20/minHCO322mmol/LVT350mlBE-2mmol/LMV7LSaO298%Hb13g/dL,CaseNo.8contd,Oxygenwaschangedto2LN/C.1/2hourpt.readytobeD/CtofloorandABG&VS:

pH7.41BP130/90mmHgPCO210mmHgPulse95/min,regularPO2148mmHgRR20/minHCO36mmol/LVT350mlBE-17mmol/LMV7LSaO299%Hb7g/dL,CaseNo.8contd,Whatisgoingon?

CaseNo.8contd,Ifthepicturedoesntfit,repeatABG!

pH7.45BP130/90mmHgPCO231mmHgPulse95/minPO287mmHgRR20/minHCO322mmol/LVT350mlBE-2mmol/LMV7LSaO296%Hb13g/dL,Technicalerrorwaspresumed.,CasestudyNo.9,67yowhohadclosedreductionoflegfxwithoutincident.FourdayslatersheexperiencedasuddenonsetofseverechestpainandSOB.RoomairABG&VS:

pH7.36BP130/90mmHgPCO233mmHgPulse100/minPO255mmHgRR25/minHCO318mmol/LBE-5mmol/LMV18LSaO288%,Interpretation:

Compensatedmetabolicacidosiswithmoderatehypoxemia.Dx:

PE,CasestudyNo.10,76yowithdocumentedchronichypercapniasecondarytosevereCOPDhasbeeninICUfor3dayswhilebeingtxforpneumonia.Shehadbeenstableforpast24hoursandwastransferredtogeneralfloor.Ptwason2Loxygen&ABG&VS:

pH7.44BP135/95mmHgPCO263mmHgPulse110/minPO252mmHgRR22/minHCO342mmol/LBE+16mmol/LMV10LSaO286%.,Interpretation:

Chronicventilatoryfailure（resp.acidosis）withuncorrectedhypoxemia,CaseNo.10contd,Shewasplacedon3Landmonitoredfornexthour.Sheremainedalert,orientedandcomfortable.ABGwasrepeated:

pH7.36BP140/100mmHgPCO275mmHgPulse105/minPO265mmHgRR24/minHCO342mmol/LBE+16mmol/LMV4.8LSaO292%.,Ptsventilatorypatternhaschangedtomorerapidandshallowbreathing.AlthoughstillacceptablethepHandCO2aretrendinginthewrongdirection.High-flowoxygenmaybebetterforthispttopreventintubation,TakeHomeMessage:

ValuableinformationcanbegainedfromanABGastothepatientsphysiologicconditionRememberthatABGanalysisifonlypartofthepatientassessment.Besystematicwithyouranalysis,startwithABCsasalwaysandlookforhypoxia（whichyoucanusuallytreatquickly）,thenfollowthefoursteps.AquickassessmentofpatientoxygenationcanbeachievedwithapulseoximeterwhichmeasuresSaO2.,ItsnotmagicunderstandingABGs,itjusttakesalittlepractice!

AnyQuestions?

References,Shapiro,BarryA.,etal;ClinicalApplicationofBloodGases;19942.AmericanJournalofNursing1999;Aug99（8）:

34-63.JournalPostAnesthesiaNursing1990;Aug;5（4）264-724.Irvine,David;ABGInterpretation,ARou