Arterial blood gas analysis (ABG)

An arterial-blood gas test measures the amounts of arterial gases, such as oxygen and carbon dioxide. An ABG test requires that a small volume of blood be drawn from the radial artery with a syringe and a thin needle, but sometimes the femoral artery in the groin or another site is used.
The common indications for ABGs are:
Respiratory compromise, which leads to hypoxia or diminished ventilation.
Peri- or postcardiopulmonary arrest or collapse.
Medical conditions that cause significant metabolic derangement, such as sepsis, diabetic ketoacidosis, renal failure, heart failure, toxic substance ingestion, drug overdose, trauma, or burns.
Evaluating the effectiveness of therapies, monitoring the patient's clinical status, and determining treatment needs. For instance, clinicians often titrate oxygenation therapy, adjust the level of ventilator support, and make decisions about fluid and electrolyte therapy based on ABG results.
During the perioperative phase of major surgeries, which includes the preoperative, intraoperative, and postoperative care of the patient.
The components of an ABG analysis are PaO2, SaO2, hydrogen ion concentration (pH), PaCO2, HCO3-, base excess, and serum levels of hemoglobin, lactate, glucose, and electrolytes (sodium, potassium, calcium, and chloride).

1. ARTERIAL BLOOD GAS
ANALYSIS
Presented by
Mr. B.KalyankumarMsc[N]
Dept Of MSN

2. INTRODUCTION
Thebodynormallymaintainsasteadybalancebetweenacids
producedduringmetabolismandbasesthatneutralizeand
promotetheexcretionoftheacids.Manyhealthproblems
mayleadtoacid-baseimbalancesinadditiontofluidand
electrolyteimbalances.PatientswithDiabetesmellitus,
chronicobstructivepulmonarydiseaseandkidneydisease
frequentlydevelopacid-baseimbalances.Vomitingand
diarrhoeamaycauselossofacidsandbasesinadditionto
fluidsandelectrolytes.Thekidneysareanessentialbuffer
systemforacids,andinolderadult,thekidneyarelessable
tocompensateforanacidload.Thenursemustalways
considerthepossibilityofacid-baseimbalancesinpatients
withseriousillness.

3. ELECTROLYTE
Electrolytearesubstanceswhosemoleculessplitintoions,when
placedinwater.Ionsareelectricallychargedparticles.Cations
arepositivelychargedparticlesandAnionsarenegatively
chargedions.
Anions:
Bicarbonate: 22-26 mEq/L
Chloride : 96-106 mEq/L
Phosphate: 2.8-4.5 mEq/L
Cations:
Potassium : 3.5-5.0 mEq/L
Magnesium: 1.5-2.5 mEq/L
Sodium: 135-145 mEq/L
Calcium: (Total) 4.5-5.5 mEq/L
Calcium(Ionized): 2.25-2.75 mEq/L

4. PH ANDHYDROGEN IONCONCENTRATION
pHandhydrogenionconcentration:
Theacidityoralkalinityofasolutiondependsonitshydrogenion
(H+)concentration.AnincreaseH+concentrationleadstoacidosis,
adecreaseleadstoalkalinity.
Despitethefactthatacidsareproducedbythebodydaily;theH+
concentrationofbodyfluidissmall(0.0004mEq/L).Hydrogenion
concentrationisusuallyexpressedasanegative
logarithm(symbolizedaspH).
AsolutionwithapHof7isconsideredneutral.Anacidsolution
hasapHlessthan7andanalkalinesolutionhasapHgreaterthan7.
Bloodisslightlyalkaline(pH7.35-7.45).

5. ACID BASE REGULATION
Thebody’smetabolicprocessesconstantlyproduceacids.These
acidsmustbeneutralizedandexcretedtomaintainacid-base
balance.Thebodyhasmechanismsbywhichitregulatesacid-
basebalancetomaintainthearterialpHbetween7.35-7.45.
These mechanisms are
Buffer system
Respiratory system
Renal system

6. Theregulatorymechanismsreactatdifferentspeeds
Bufferreactimmediately
Therespiratorysystemrespondsinminutesandreaches
maximumeffectiveinhours.
Therenalsystemresponsetakes2-3daystorespond
maximally,butkidneycanmaintainbalanceindefinitelyin
chronicimbalances.

7. BUFFER SYSTEM
Thebuffersystemisthefastestactingsystemandprimary
regulatoryofacid-basebalance.Bufferactchemicallyto
changestrongacidsintoweakeracidsortobindacidsto
neutralizetheireffect.Thebuffersinthebodyincludecarbonic
acid-bicarbonate,plasmaproteinandhaemoglobinbuffers.
Thebufferfunctiontominimizetheeffectofacidsonblood
pHuntiltheycanbeexcretedfromthebody.Bufferscan’t
maintainpHwithouttheadequatefunctioningofthe
respiratoryandrenalsystem.

9. RESPIRATORY SYSTEM
ThelungsmaintainanormalPhbyexcretingco2andwater,
whichareby-productsofcellularmetabolism.
TheamountofCo2intheblooddirectlyrelatestocarbonic
acidconcentrationandsubsequentlytoH+concentration.With
increasedrespirationsmoreCo2isexpelledandlessremainsin
theblood,thisleadstolesscarbonicacidandlessH+.

10. RENAL SYSTEM
Under normal conditions, the kidneys reabsorb and conserve
all of the bicarbonate they filter. The kidneys can Generate
additional bicarbonate to eliminate excess H+ as
compensation for acidosis.
The 3 mechanisms of acid elimination are
1) Secretion of small amounts of free hydrogen into the renal
tubule
2) Combination of H+ with ammonia (NH3) to form
ammonium
3) Excretion of weak acids

11. ALTERATIONSINACID-BASEBALANCE
Acidbaseimbalancesareclassifiedasrespiratoryor
metabolic.Respiratoryimbalancesaffectcarbonicacid
concentrations,metabolicimbalancesaffectbase
bicarbonate.

12. Respiratoryacidosis(Pco2):Respiratoryacidosis(carbonicacid
excessPco2>45)occurswheneverthereishypoventilation.
Hypoventilationresultsinabuild-upofCo2.
Causes:COPD,sedativeoverdose,obesity,pneumonia,
atelectasis,mechanicalhypoventilation.

13. Clinicalmanifestations:Increasedpulseandrespiratoryrate,
increasedbloodpressure,ICPmayincrease
Management:Treatmentisdirectedatimprovingventilation.
Bronchodilatorshelpreducebronchialspasm
Antibioticsareusedtotreatrespiratoryinfections.
Thrombolyticoranticoagulantsareusedforpulmonaryemboli.
Mechanicalventilation
Placingthepatientinsemi-fowlerspositionfacilitatesexpansion
ofthechestwall.

14. RESPIRATORYALKALOSIS(PCO2)
Respiratoryalkalosis(CarbonicaciddeficitPco2<35)occurs
withhyperventilation.
Causes:Hyperventilation(causedbyhypoxia,fear,anxiety,
pain,exercise)Mechanicalhyperventilation
Management:Ifthecauseisanxiety,thepatientisinstructedto
breathmoreslowlytoallowCo2toaccumulate,asedativemay
berequiredtorelievehyperventilationinveryanxiouspatients

15. METABOLICACIDOSIS(HCO3)
BicarbonatedeficitHco3<22
Causes:Diabeticketoacidosis,starvation,severediarrhoea,renal
failure,shock
Clinicalmanifestations:Headache,confusion,drowsiness,
increasedrespiratoryrate,nauseaandvomiting,peripheral
vasodilation.

16. Management:Bicarbonateadministered
Treatmentmodalitiesmayalsoincludehemodialysisor
peritonealdialysis.

17. METABOLICALKALOSIS(HCO3)
BicarbonateexcessHco3>26(occurswhenalossofacid)
Causes:severevomiting,ingestionofbakingsoda,Diuretic
therapy,potassiumdeficit
Clinicalmanifestations:Dizziness,hypokalemia,decreased
calcium
Management:Restorefluidvolume,KCLcorrection,
H2receptorantagonist(Cimetidine).

18. COMPENSATION LEVEL
Compensated ABG
Partially compensated
ABG
Uncompensated ABG

20. PROCEDURE

21. INDICATIONS
Providesabloodspecimenfordirectmeasurementofpartial
pressureofcarbondioxide(Paco2)andpartialpressureof
oxygen(O2)
❖Hydrogenionactivity(PH)
❖Totalhaemoglobin(Hb)
❖Bicarbonatelevel(HCO3)
❖Baseexcess.

22. CONT….
ThroughArterialbloodgasanalysiscanidentifyRespiratoryand
Metabolicconditionsofthepatient
Forstartingcontinuousarterialbloodpressuremonitoringinan
emergency
Theneedtoquanitatepatientsresponsetotherapeuticintervention
anddiagnosticevaluation(Eg.Oxygentherapy).

23. ResultsofaAllen’stest(collateralcirculationtest)are
indicativeofinadequatebloodsupplytothehand.
Arterialpunctureshouldnotbeperformedthroughalesionor
distaltoasurgicalshunt.
Anticoagulationtherapy(Eg-Heparin,streptokinase)maybea
relativecontraindicationforarterialpuncture.
CONTRA INDICATIONS

24. Samplemustbeanticoagulatedwithimmediateexpulsionof
airbubbles.
Sampleshouldbeimmediatelyanalyzedwithin10-15minutes.
TheRadialarteryismostcommonlyusedtoobtainthesample.
However,thefemoralarteryandbrachialarterycanbeusedif
necessary.Ifthepatientalreadyhasapre-existingarterialline,
thiscanbeusedtoobtainthesample.
PRINCIPLES

25. BloodgaskitOR
2mldisposablesyringe
Alcoholswab
Disposablegloves
Plasticbag&crushedice
Lidocaine(optional)
Vialofheparin
Label
Arterialcatheter.
ARTICLES

26. Identifypatientbyaskingname
Recordpatientsinspiredoxygenconcentration
Heparinizethe2mlsyringe,holdsyringeinanuprightposition
andexpelexcessheparinandairbubbles
Washhands,anddongloves
Palpatetheradial,brachialorfemoralartery
IfRadialarteryselectedforpuncture,performAllen’stest.
Note:IftheUlnararterydoesnothavesufficientbloodsupply
toperfuseentirehandtheradialarteryshouldnotbeused.
PROCEDURE

27. ALLEN’STEST

28. Cleanwithalcoholswabincircularmotion
Skinandsubcutaneoustissuemaybeinfiltratedwithlocal
anestheticagentifneeded
Insertneedleat45radial,60brachialand90femoral
Withdrawtheneedleandapplypressure
Checkbubblesinsyringe
Placethecappedsyringeinthecontaineroficeimmediately
Maintainfirmpressureonthepuncturesitefor5minutes
Sendlabeled,icedspecimentothelabimmediately
Documentationinclude:Timethesamplewasdrawn,puncture
site,timepressurewasapplied
Ifthepatientisreceivingmechanicalventilation,FIO2should
bedocumented.

30. GOOD TIME WITH YOU