血气分析(英文版)VIP免费

ABGINTERPRETATIONDebbieSanderPAS-IIObjectivesWhat’sanABG?UnderstandingAcid/BaseRelationshipGeneralapproachtoABGInterpretationClinicalcausesAbnormalABG’sCasestudiesTakehomeWhatisanABGArterialBloodGasDrawnfromartery-radial,brachial,femoralItisaninvasiveprocedure.Cautionmustbetakenwithpatientonanticoagulants.Helpsdifferentiateoxygendeficienciesfromprimaryventilatorydeficienciesfromprimarymetabolicacid-baseabnormalitiesWhatIsAnABG?pH[H+]PCO2PartialpressureCO2PO2PartialpressureO2HCO3BicarbonateBEBaseexcessSaO2OxygenSaturationAcid/BaseRelationshipThisrelationshipiscriticalforhomeostasisSignificantdeviationsfromnormalpHrangesarepoorlytoleratedandmaybelifethreateningAchievedbyRespiratoryandRenalsystemsCaseStudyNo.160y/omalecomesERc/oSOB.Tachypneic,tachycardic,diaphoreticandCyanotic.Dxacuteresp.failureandABG’sShowPaCO2wellbelownl,pHabovenl,PaO2isverylow.ThebloodgasdocumentResp.failureduetoprimaryO2problem.CaseStudyNo.260y/omalecomesERc/oSOB.Tachypneic,tachycardic,diaphoreticandCyanotic.Dxacuteresp.failureandABG’sShowPaCO2veryhigh,lowpHandPaO2ismoderatelylow.ThebloodgasdocumentResp.failureduetoprimarilyventilatoryinsufficiency.TherearetwobuffersthatworkinpairsH2CO3NaHCO3CarbonicacidbasebicarbonateThesebuffersarelinkedtotherespiratoryandrenalcompensatorysystemBuffersRespiratoryComponentfunctionofthelungsCarbonicacidH2CO3Approximately98%normalmetabolitesareintheformofCO2CO2+H2OH2CO3excessCO2exhaledbythelungsMetabolicComponentFunctionofthekidneysbasebicarbonateNaHCO3ProcessofkidneysexcretingH+intotheurineandreabsorbingHCO3-intothebloodfromtherenaltubules1)activeexchangeNa+forH+betweenthetubularcellsandglomerularfiltrate2)carbonicanhydraseisanenzymethataccelerateshydration/dehydrationCO2inrenalepithelialcellsH2O+CO2H2CO3HCO3+H+Acid/BaseRelationshipNormalABGvaluespH7.35–7.45PCO235–45mmHgPO280–100mmHgHCO322–26mmol/LBE-2-+2SaO2>95%AcidosisAlkalosispH<7.35PCO2>45HCO3<22pH>7.45PCO2<35HCO3>26RespiratoryAcidosisThinkofCO2asanacidfailureofthelungstoexhaleadequateCO2pH<7.35PCO2>45CO2+H2CO3pHCausesofRespiratoryAcidosisemphysemadrugoverdosenarcosisrespiratoryarrestairwayobstructionMetabolicAcidosisfailureofkidneyfunctionbloodHCO3whichresultsinavailabilityofrenaltubularHCO3forH+excretionpH<7.35HCO3<22CausesofMetabolicAcidosisrenalfailurediabeticketoacidosislacticacidosisexcessivediarrheacardiacarrestRespiratoryAlkalosistoomuchCO2exhaled(hyperventilation)PCO2,H2CO3insufficiency=pHpH>7.45PCO2<35CausesofRespiratoryAlkalosishyperventilationpanicd/opainpregnancyacuteanemiasalicylateoverdoseMetabolicAlkalosisplasmabicarbonatepH>7.45HCO3>26CausesofMetabolicAlkalosislossacidfromstomachorkidneyhypokalemiaexcessivealkaliintakeHowtoAnalyzeanABG1.PO2NL=80–100mmHg2.pHNL=7.35–7.45Acidotic<7.35Alkalotic>7.453.PCO2NL=35–45mmHgAcidotic>45Alkalotic<354.HCO3NL=22–26mmol/LAcidotic<22Alkalotic>26Four-stepABGInterpretationStep1:ExaminePaO2&SaO2DetermineoxygenstatusLowPaO2(<80mmHg)&SaO2meanshypoxiaNL/elevatedoxygenmeansadequateoxygenationStep2:pHacidosis<7.35alkalosis>7.45Four-stepABGInterpretationStep3:studyPaCO2&HCO3respiratoryirregularityifPaCO2abnl&HCO3NLmetabolicirregularityifHCO3abnl&PaCO2NLFour-stepABGInterpretationStep4:Determineifthereisacompensatorymech...