血氣分析英文版課件

ABGINTERPRETATIONDebbieSanderPAS-IIABGINTERPRETATION1ObjectivesWhat’sanABG?

UnderstandingAcid/BaseRelationship

GeneralapproachtoABGInterpretation

ClinicalcausesAbnormalABG’s

Casestudies

TakehomeObjectivesWhat’sanABG?

2WhatisanABGArterialBloodGasDrawnfromartery-radial,brachial,femoralItisaninvasiveprocedure.Cautionmustbetakenwithpatientonanticoagulants.Helpsdifferentiateoxygendeficienciesfromprimaryventilatorydeficienciesfromprimarymetabolicacid-baseabnormalitiesWhatisanABGArterialBloodG3WhatIsAnABG?pH [H+]PCO2PartialpressureCO2PO2PartialpressureO2HCO3BicarbonateBE BaseexcessSaO2 OxygenSaturationWhatIsAnABG?pH [H+]4Acid/BaseRelationshipThisrelationshipiscriticalforhomeostasis

SignificantdeviationsfromnormalpHrangesare

poorlytoleratedandmaybelifethreatening

AchievedbyRespiratoryandRenalsystemsAcid/BaseRelationshipThisre5CaseStudyNo.160y/omalecomesERc/oSOB.Tachypneic,tachycardic,diaphoreticandCyanotic.Dxacuteresp.failureandABG’sShowPaCO2wellbelownl,pHabovenl,PaO2isverylow.ThebloodgasdocumentResp.failureduetoprimaryO2problem.CaseStudyNo.160y/omaleco6CaseStudyNo.260y/omalecomesERc/oSOB.Tachypneic,tachycardic,diaphoreticandCyanotic.Dxacuteresp.failureandABG’sShowPaCO2veryhigh,lowpHandPaO2ismoderatelylow.ThebloodgasdocumentResp.failureduetoprimarilyventilatoryinsufficiency.CaseStudyNo.260y/omaleco7TherearetwobuffersthatworkinpairsH2CO3 NaHCO3

Carbonicacid basebicarbonate

Thesebuffersarelinkedtotherespiratoryand

renalcompensatorysystemBuffersTherearetwobuffersthatwor8RespiratoryComponentfunctionofthelungsCarbonicacidH2CO3

Approximately98%normalmetabolitesareintheform

ofCO2CO2+H2O

H2CO3excessCO2exhaledbythelungsRespiratoryComponentfunction9MetabolicComponentFunctionofthekidneysbasebicarbonateNaHCO3

ProcessofkidneysexcretingH+intotheurineandreabsorbing

HCO3-intothebloodfromtherenaltubules

1)activeexchangeNa+forH+betweenthetubular

cellsandglomerularfiltrate

2)carbonicanhydraseisanenzymethataccelerates

hydration/dehydrationCO2

inrenalepithelialcellsMetabolicComponentFunctiono10H2O+CO2

H2CO3

HCO3+H+Acid/BaseRelationshipH2O+CO2H2C11NormalABGvaluespH 7.35–7.45PCO2 35–45mmHgPO2 80–100mmHgHCO3 22–26mmol/LBE -2-+2SaO2 >95%

NormalABGvaluespH 7.35–7.12Acidosis AlkalosispH <7.35PCO2 >45HCO3 <22pH >7.45PCO2 <35HCO3 >26Acidosis AlkalosispH <7.35pH13RespiratoryAcidosisThinkofCO2asanacidfailureofthelungstoexhaleadequateCO2

pH<7.35 PCO2>45CO2 +H2CO3

pHRespiratoryAcidosisThinkof14CausesofRespiratoryAcidosisemphysemadrugoverdosenarcosisrespiratoryarrestairwayobstructionCausesofRespiratoryAcidosis15MetabolicAcidosisfailureofkidneyfunction

bloodHCO3whichresultsinavailabilityofrenal

tubularHCO3forH+excretionpH<7.35HCO3<22MetabolicAcidosisfailureof16CausesofMetabolicAcidosisrenalfailurediabeticketoacidosislacticacidosisexcessivediarrheacardiacarrestCausesofMetabolicAcidosisr17RespiratoryAlkalosistoomuchCO2exhaled(hyperventilation)

PCO2,H2CO3insufficiency=pHpH>7.45PCO2<35RespiratoryAlkalosistoomuch18CausesofRespiratoryAlkalosishyperventilationpanicd/opainpregnancyacuteanemiasalicylateoverdoseCausesofRespiratoryAlkalosi19MetabolicAlkalosis

plasmabicarbonatepH>7.45HCO3>26MetabolicAlkalosisplasmab20CausesofMetabolicAlkalosis

lossacidfromstomachorkidneyhypokalemiaexcessivealkaliintakeCausesofMetabolicAlkalosis21HowtoAnalyzeanABGPO2 NL =80–100mmHg2.pH NL =7.35–7.45 Acidotic <7.35 Alkalotic >7.45PCO2 NL =35–45mmHg Acidotic >45 Alkalotic <35HCO3 NL =22–26mmol/L Acidotic<22 Alkalotic >26HowtoAnalyzeanABGPO2 NL =22Four-stepABGInterpretationStep1:

ExaminePaO2&SaO2DetermineoxygenstatusLowPaO2(<80mmHg)&SaO2meanshypoxiaNL/elevatedoxygenmeansadequateoxygenationFour-stepABGInterpretationSt23Step2:pH acidosis <7.35 alkalosis >7.45Four-stepABGInterpretationStep2:Four-stepABGInterpret24Step3:studyPaCO2&HCO3respiratoryirregularityifPaCO2abnl&HCO3NLmetabolicirregularityifHCO3abnl&PaCO2NLFour-stepABGInterpretationStep3:Four-stepABGInterpret25Step4:DetermineifthereisacompensatorymechanismworkingtotrytocorrectthepH.ie:ifhaveprimaryrespiratoryacidosiswillhaveincreasedPaCO2anddecreasedpH.CompensationoccurswhenthekidneysretainHCO3.Four-stepABGInterpretationStep4:Four-stepABGInterpret26~PaCO2

–pHRelationship80 7.20

60 7.30

40

7.40

30 7.50

20 7.60~PaCO2–pHRelationship80 727CompensatedRespiratoryAcidosisCO2MoreAbnormalRespiratoryAcidosisCO2ExpectedMixedRespiratoryMetabolicAcidosisCO2LessAbnormalCO2Changec/wAbnormalityMetabolicMetabolic

AcidosisCO2NormalCompensatedMetabolicAcidosisCO2ChangeopposesAbnormalityAcidosisABGInterpretationCompensatedRespiratoryAcidosis28CompensatedRespiratoryAlkalosisCO2MoreAbnormalRespiratoryAlkalosisCO2ExpectedMixedRespiratoryMetabolicAlkalosisCO2LessAbnormalCO2Changec/wAbnormalityMetabolicAlkalosisCO2NormalCompensatedMetabolicAlkalosisCO2ChangeopposesAbnormalityAlkalosisABGInterpretationCompensatedRespiratoryAlkalosi29RespiratoryAcidosispH 7.30PaCO2 60HCO3 26RespiratoryAcidosispH 7.3030RespiratoryAlkalosispH 7.50PaCO2 30HCO3 22RespiratoryAlkalosispH 7.5031MetabolicAcidosispH 7.30PaCO2 40HCO315MetabolicAcidosispH 7.3032MetabolicAlkalosispH 7.50PCO240HCO3 30MetabolicAlkalosispH 7.5033Whatarethecompensations?Respiratoryacidosis metabolicalkalosisRespiratoryalkalosis metabolicacidosisInrespiratoryconditions,therefore,thekidneyswillattempttocompensateandvisaversa.Inchronicrespiratoryacidosis(COPD)thekidneysincreasetheeliminationofH+andabsorbmoreHCO3.TheABGwillShowNLpH,CO2andHCO3.Bufferskickinwithinminutes.Respiratorycompensationisrapidandstartswithinminutesandcompletewithin24hours.Kidneycompensationtakeshoursandupto5days.Whatarethecompensations?Res34MixedAcid-BaseAbnormalitiesCaseStudyNo.3:56yo

neurologicdzrequiredventilatorsupportforseveralweeks.SheseemedmostcomfortablewhenhyperventilatedtoPaCO228-30mmHg.Sherequireddailydosesoflasixtoassureadequateurineoutputandreceived40mmol/LIVK+eachday.On10thdayofICUherABGon24%oxygen&VS:MixedAcid-BaseAbnormalities35ABGResultspH 7.62 BP 115/80mmHgPCO2 30mmHg Pulse 88/minPO2 85mmHg RR 10/minHCO3 30mmol/L VT 1000mlBE 10mmol/L MV 10LK+ 2.5mmol/LInterpretation: Acutealveolarhyperventilation(resp.alkalosis)andmetabolicalkalosiswithcorrectedhypoxemia.ABGResultspH 7.62 BP 115/8036CasestudyNo.427yoretarded

withinsulin-dependentDMarrivedatERfromtheinstitutionwherehelived.OnroomairABG&VS:pH 7.15 BP 180/110mmHgPCO2 22mmHg Pulse 130/minPO2 92mmHg RR 40/minHCO3 9mmol/L VT 800mlBE -30mmol/L MV 32LInterpretation: Partlycompensatedmetabolicacidosis.CasestudyNo.427yoretarded37CasestudyNo.574yo

withhxchronicrenalfailureandchronicdiuretictherapywasadmittedtoICUcomatoseandseverelydehydrated.On40%oxygenherABG&VS:pH 7.52 BP 130/90mmHgPCO2 55mmHg Pulse 120/minPO2 92mmHg RR 25/minHCO3 42mmol/L VT 150mlBE 17mmol/L MV 3.75LInterpretation: Partlycompensatedmetabolicalkalosiswithcorrectedhypoxemia.CasestudyNo.574yowithh38CasestudyNo.643yo

arrivesinER20minutesafteraMVAinwhichheinjuredhisfaceonthedashboard.Heisagitated,hasmottled,coldandclammyskinandhasobviouspartialairwayobstruction.Anoxygenmaskat10Lisplacedonhisface.ABG&VS:pH 7.10 BP 150/110mmHgPCO2 60mmHg Pulse 150/minPO2 125mmHg RR 45/minHCO3 18mmol/L VT ?mlBE -15mmol/L MV ?L.Interpretation: Acuteventilatoryfailure(resp.acidosis)andacutemetabolicacidosiswithcorrectedhypoxemiaCasestudyNo.643yoarrive39CasestudyNo.717yo,48kg

withknowninsulin-dependentDMcametoERwithKussmaulbreathingandirregularpulse.RoomairABG&VS:pH 7.05 BP 140/90mmHgPCO2 12mmHg Pulse 118/minPO2 108mmHg RR 40/minHCO3 5mmol/L VT 1200mlBE -30mmol/L MV 48LInterpretation: Severepartlycompensatedmetabolicacidosiswithouthypoxemia.CasestudyNo.717yo,48kg40CaseNo.7cont’dThispatientisindiabeticketoacidosis.IVglucoseandinsulinwereimmediatelyadministered.AjudgementwasmadethatsevereacidemiawasadverselyaffectingCVfunctionandbicarbwaselectedtorestorepHto7.20.Bicarbadministrationcalculation:BasedeficitXweight(kg) 4 30X48=360mmol/L Admin1/2over15min&4 repeatABGCaseNo.7cont’dThispatient41CaseNo.7cont’dABGresultafterbicarb:pH 7.27 BP 130/80mmHgPCO2 25mmHg Pulse 100/minPO2 92mmHg RR 22/minHCO3 11mmol/L VT 600mlBE -14mmol/L MV 13.2LCaseNo.7cont’dABGresultaf42CasestudyNo.847yo

wasinPACUfor3hourss/pcholecystectomy.Shehadbeenon40%oxygenandABG&VS:pH 7.44 BP 130/90mmHgPCO2 32mmHg Pulse 95/min,regularPO2 121mmHg RR 20/minHCO3 22mmol/L VT 350mlBE -2mmol/L MV 7LSaO2 98%Hb 13g/dLCasestudyNo.847yowasin43CaseNo.8cont’dOxygenwaschangedto2LN/C.1/2hourpt.readytobeD/CtofloorandABG&VS:pH 7.41 BP 130/90mmHgPCO2 10mmHg Pulse 95/min,regularPO2 148mmHg RR 20/minHCO3 6mmol/L VT 350mlBE -17mmol/L MV 7LSaO2 99%Hb 7g/dLCaseNo.8cont’dOxygenwasch44CaseNo.8cont’dWhatisgoingon?CaseNo.8cont’dWhatisg45CaseNo.8cont’dIfthepicturedoesn’tfit,repeatABG!!pH 7.45 BP 130/90mmHgPCO2 31mmHg Pulse 95/minPO2 87mmHg RR 20/minHCO3 22mmol/L VT 350mlBE -2mmol/L MV 7LSaO2 96%Hb 13g/dLTechnicalerrorwaspresumed.CaseNo.8cont’dIfthepictur46CasestudyNo.967yo

whohadclosedreductionoflegfxwithoutincident.FourdayslatersheexperiencedasuddenonsetofseverechestpainandSOB.RoomairABG&VS:pH 7.36 BP 130/90mmHgPCO2 33mmHg Pulse 100/minPO2 55mmHg RR 25/minHCO3 18mmol/L BE -5mmol/L MV 18LSaO2 88%

Interpretation: Compensatedmetabolicacidosiswithmoderatehypoxemia.Dx:PECasestudyNo.967yowhoha47CasestudyNo.1076yo

withdocumentedchronichypercapniasecondarytosevereCOPDhasbeeninICUfor3dayswhilebeingtxforpneumonia.Shehadbeenstableforpast24hoursandwastransferredtogeneralfloor.Ptwason2Loxygen&ABG&VS:pH 7.44 BP 135/95mmHgPCO2 63mmHg Pulse 110/minPO2 52mmHg RR 22/minHCO3 42mmol/L BE +16mmol/L MV 10LSaO2 86%.Interpretation: Chronicventilatoryfailure(resp.acidosis)withuncorrectedhypoxemiaCasestudyNo.1076yowith48CaseNo.10cont’dShewasplacedon3Landmonitoredfornexthour.Sheremainedalert,orientedandcomfortable.ABGwasrepeated:pH 7.36 BP 140/100mmHgPCO2 75mmHg Pulse 105/minPO2 65mmHg RR 24/minHCO3 42mmol/L BE +16mmol/L MV 4.8LSaO2 92%.Pt’sventilatorypatternhaschangedtomorerapidandshallowbreathing.AlthoughstillacceptablethepHandCO2aretrendinginthewrongdirection.High-flowoxygenmaybebetterforthispttopreventintubationCaseNo.10cont’dShewasplac49TakeHomeMessage:ValuableinformationcanbegainedfromanABGastothepatientsphysiologicconditionRememberthatABGanalysisifonlypartofthepatientassessment.

Besystematicwithyouranalysis,startwithABC’sasalways

andlookforhypoxia(whichyoucanusuallytreatquickly),

thenfollowthefoursteps.

Aquickassessmentofpatientoxygenationcanbeachieved

withapulseoximeterwhichmeasuresSaO2.

TakeHomeMessage:Va50It’snotmagicunderstandingABG’s,itju