2. Obtaining Blood GasObtaining Blood Gas
SamplesSamples
Radial artery- best siteRadial artery- best site
located superficially, easy to palpatelocated superficially, easy to palpate
& stabilize& stabilize
excellent collateral circulation viaexcellent collateral circulation via
ulnar arteryulnar artery
not adjacent to large veinsnot adjacent to large veins
probing needle relatively pain-free ifprobing needle relatively pain-free if
periosteum is avoidedperiosteum is avoided
3. TechniqueTechnique for Radial Arteryfor Radial Artery
PuncturePuncture
Explain process to patient. Examine skin,Explain process to patient. Examine skin,
palpate radial & ulnar arteries. Performpalpate radial & ulnar arteries. Perform
modified Allen Test.modified Allen Test.
4. The Allen TestThe Allen Test
have the patienthave the patient
clench his/her fistclench his/her fist
press on bothpress on both
radial and ulnarradial and ulnar
arteriesarteries
have the patienthave the patient
unclench fistunclench fist
test for goodtest for good
collateral flow.collateral flow.
5. Technique for Radial ArteryTechnique for Radial Artery
PuncturePuncture
Position patient- hyperextend wrist. CleanPosition patient- hyperextend wrist. Clean
site with 70% isopropyl alcohol.site with 70% isopropyl alcohol.
Use latex gloves while doing procedure.Use latex gloves while doing procedure.
Local anesthesia may be used.Local anesthesia may be used.
Use G20 or G21 needle. Flush syringe withUse G20 or G21 needle. Flush syringe with
sodium heparin (10 mg/ml or 1,000sodium heparin (10 mg/ml or 1,000
units/ml) & empty.units/ml) & empty. 0.15-0.25 ml of heparin will0.15-0.25 ml of heparin will
anticoagulate 2-4 ml of blood.anticoagulate 2-4 ml of blood.
6. Technique for Radial ArteryTechnique for Radial Artery
PuncturePuncture
Palpate artery with one hand while holdingPalpate artery with one hand while holding
properly prepared syringe & needle with otherproperly prepared syringe & needle with other
hand. Hold syringe like a pencil & enter skinhand. Hold syringe like a pencil & enter skin
at 45at 45
o
. Advance needle slowly.
Never redirect needle without first withdrawing toNever redirect needle without first withdrawing to
subcutaneous tissue.subcutaneous tissue.
Obtain 2-4 ml blood. If possible don’t aspirate.Obtain 2-4 ml blood. If possible don’t aspirate.
Remove air bubbles from syringe. ImmediatelyRemove air bubbles from syringe. Immediately
seal syringe with cap.seal syringe with cap.
Place sample in ice slush. Analyze blood samplePlace sample in ice slush. Analyze blood sample
within 10 minutes.within 10 minutes.
Apply pressure to site until bleeding has stopped.Apply pressure to site until bleeding has stopped.
7. Potential ComplicationsPotential Complications
PainPain
Hematoma, hemorrhageHematoma, hemorrhage
Trauma to vesselTrauma to vessel
ArteriospasmArteriospasm
Air or clotted-bloodAir or clotted-blood
emboliemboli
Vasovagal responseVasovagal response
Arterial occlusionArterial occlusion
InfectionInfection
8. Indications for ABGIndications for ABG
Assess ventilation & acid-baseAssess ventilation & acid-base
balancebalance
Assess oxygenation statusAssess oxygenation status
12. Traditional Respiratory Acid-Base NomenclatureTraditional Respiratory Acid-Base Nomenclature
NomenclatureNomenclature pHpH PCOPCO
22
[HCO3][HCO3]
pp
BEBE
RespiratoryRespiratory
acidosisacidosis
Uncompensated (acute)Uncompensated (acute) NN NN
Partly compensatedPartly compensated
(subacute)(subacute)
Compensated (chronic)Compensated (chronic)
NN
RespiratoryRespiratory
alkalosisalkalosis
Uncompensated (acute)Uncompensated (acute) NN NN
Partly compensatedPartly compensated
(subacute)(subacute)
Compensated (chronic)Compensated (chronic) NN
13. Base Excess/ DeficitBase Excess/ Deficit
Blood with large buffering capacity:Blood with large buffering capacity:
significant changes in acid content with little change in freesignificant changes in acid content with little change in free
HH++
concentrations (pH)concentrations (pH)
Acidemia or alkalemia:Acidemia or alkalemia: buffering capacity, > potential forbuffering capacity, > potential for
pH change from any given change in HpH change from any given change in H++
contentcontent
Buffering capacity depends on:Buffering capacity depends on:
[HCO[HCO33
--
]]
RBC massRBC mass
other factorsother factors
Base excess/deficit= (measured pH – predicted pH) x 100 xBase excess/deficit= (measured pH – predicted pH) x 100 x
2/32/3
Normal metabolic acid-base status:Normal metabolic acid-base status: ++ 3 mmol/L3 mmol/L
Relatively balanced metabolic acid-base status:Relatively balanced metabolic acid-base status: ++ 55
mmol/Lmmol/L
Clinically significant imbalance:Clinically significant imbalance: ++ 1010
mmol/Lmmol/L
33. Steps for Analyzing Acid- Base DisturbancesSteps for Analyzing Acid- Base Disturbances
Is patient acidemic or alkalotic?Is patient acidemic or alkalotic? pHpH
Is disturbance primarily respiratory or metabolic?Is disturbance primarily respiratory or metabolic?
PCOPCO22, [HCO, [HCO33
--
]]
If disturbance respiratory, is it acute or chronic?If disturbance respiratory, is it acute or chronic?
If disturbance metabolic, is anion gap normal orIf disturbance metabolic, is anion gap normal or
abnormal?abnormal?
If disturbance metabolic, is the respiratoryIf disturbance metabolic, is the respiratory
system compensating adequately?system compensating adequately?
If disturbance is anion gap metabolic acidosis, areIf disturbance is anion gap metabolic acidosis, are
there any other metabolic disturbances present?there any other metabolic disturbances present?
37. 1. Is the patient hypoxemic or normoxemic?1. Is the patient hypoxemic or normoxemic?
Indices of Oxygenation:Indices of Oxygenation:
a. AaDOa. AaDO22 = PAO= PAO22 – PaO– PaO22
PAOPAO22 = FiO= FiO22 (713) –(713) – PaCOPaCO22
0.80.8
PaOPaO22 = obtained from blood gas determination= obtained from blood gas determination
b. aAOb. aAO22 == PaOPaO22
PAOPAO22
c. P/F ratio =c. P/F ratio = POPO22
FiOFiO22
Normal Value:Normal Value: patientspatients << 60 y. o. > 40060 y. o. > 400
patients > 60 y. o. expected P/F =patients > 60 y. o. expected P/F =
400400
–– [(age in years – 60) x 5][(age in years – 60) x 5]
Actual P/F Ratio < expected =Actual P/F Ratio < expected = hypoxemichypoxemic
Actual P/F RatioActual P/F Ratio >> expected =expected = normoxemicnormoxemic
38. 2. If hypoxemic, is it uncorrected,2. If hypoxemic, is it uncorrected,
corrected, or overcorrected?corrected, or overcorrected?
With OWith O22 supplementationsupplementation
PaOPaO22 (mmHg)(mmHg)
Uncorrected hypoxemiaUncorrected hypoxemia < 80< 80
Corrected hypoxemiaCorrected hypoxemia 80 – 12080 – 120
OvercorrectedOvercorrected > 120> 120
FiOFiO22 to PaOto PaO22 Relationship in Normal LungsRelationship in Normal Lungs
FiOFiO22 PaOPaO22 (mmHg)(mmHg)
0.300.30 > 150> 150
0.400.40 > 200> 200
0.500.50 > 250> 250
0.800.80 > 400> 400
1.001.00 > 500> 500
39. Room Air (patientRoom Air (patient << 60 y. o.)60 y. o.)
PaOPaO22 (mmHg)(mmHg)
Mild hypoxemiaMild hypoxemia 60 to < 8060 to < 80
Moderate hypoxemiaModerate hypoxemia 40 to < 6040 to < 60
Severe hypoxemiaSevere hypoxemia < 40< 40
For each year > 60 subtract 1 mmHg for limits ofFor each year > 60 subtract 1 mmHg for limits of
mild &mild &
moderate hypoxemia.moderate hypoxemia.
At any age, PaOAt any age, PaO22 < 40 mmHg indicates severe< 40 mmHg indicates severe
hypoxemia.hypoxemia.
40. 3. If normoxemic, is oxygenation3. If normoxemic, is oxygenation
adequate or more thanadequate or more than
adequate?adequate?