Abg
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Transcript of Abg
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Arterial Blood Gas AnalysisArterial Blood Gas Analysis
Dr. Tongjun MaDr. Tongjun Ma
Emergency Department of Emergency Department of Tianjin medical university Tianjin medical university
General HospitalGeneral Hospital
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3 parts:introduction: contents, indicationsartery puncture techniqueexplain the important
measurements
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Contents of ABGContents of ABG
MeasurespH Percent of H+ ConcentrationpCO2Pressure of Carbon Dioxide
pO2 Pressure of Oxygen
Sao2 Oxygen Saturation
BE Base ExcessHCO3 Bicarbonate
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IndicationsIndications
assess respiratory functionadequacy of ventilation and oxygenationmake changes in treatment, such as ventilator settings
evaluate acid-base status
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Blood sample collection Blood sample collection
2 methods:artery puncturecapillary blood
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Complications of PunctureComplications of PunctureBleeding
Local, occultIschemic consequences
spasm, thrombosis, embolismtrauma
Nerve, tendon InfectionWith the use of proper technique, the complication rate is extremely low.
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Puncture sitesPuncture sites consider
the risk of hemorrhage and how to controlthe risk of complete blood flow loss the risk of injury patient comfort and nursing care concerns
possible sites: Radial, Femoral, Brachial
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Radial arteryRadial artery
the one most commonly usedcollateral circulationthe risk of obtaining venous blood or damaging a nerve is low
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Femoral arteryFemoral artery
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Brachial arteryBrachial artery
the risk of complications is greater than radial artery
has little collateral circulation
avoid except in extreme circumstances
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Puncture techniquePuncture technique
4 steps:Preparationcleanse the skin, local anesthesiaPunctureCap the syringe and transport
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Preparation 1Preparation 1
Preparation of ClientOxygen, the settings for the respirator, the temperature Found the artery
The pulsations of the radial artery should be palpable just proximal to the transverse wrist creases
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Preparation 2Preparation 2Syringe
a prepackaged ABG kit Choose a syringe with minimal dead space (e.g., BD insulin syringe) ,0.5-1.0 ml, Airtight
Heparinized, eliminate heparin-related errors ,All heparin should be ejected
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Step 2 Step 2
cleanse the skiniodine and alcohol
local anesthesiaan intradermal wheal of 1% lidocaine
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PuncturePuncture
Angle30°to 45°, 60 °, 75 °
If resistance is met or no blood returns, the needle should be slowly withdrawnpress for 5 minutes or longer to control bleeding
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Cap and transportCap and transport
expel all air bubbles within 2 min Cap the syringe transport to the laboratory
put the sample on ice if the test is not completed within 10 min
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Key pointsKey pointsUse small-gauge needleDo not puncture the same site repeatedlyConfirm the potency of the ulnar artery
Doppler examinationAllen test
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What is pHWhat is pH
Acidic AlkalineNeutral
0 14
7
How acidic or base a substance is Scale runs from 1 – 14 Less than 7 is acidic, Greater than 7 is base
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ArterialArterial Blood pHBlood pH
7.4 AcademiaAcidosis?
Alkalemia Alkalosis?
7.35~7.45
6.8 7.8
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ImportanceImportance of pH of pH
Ensure metabolic intermediates are in the ionized state
Intracellular enzymes have a pH optimum DNA, RNA and protein synthesis is
facilitated at this pH
Every enzymatic reaction in the body is affected by pH!
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Adverse Clinical Effects of AcidemiaAdverse Clinical Effects of Acidemia
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CompensationCompensation
The goal is to try to maintain normal pHIf the compensation occurs fully, the pH
returns to normalIf the compensating organ cant work hard
enough to compensate, the pH will still be abnormal
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Lungs CompensationLungs Compensation
by changing respiratory rate pH (acid) , respiratory rate to blow off
CO2
Very sensitive and can compensate quicklytires easily so cant continue long term
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Body is openBody is openIf add 12 mM H+ to closed system
– if all acid is buffered
– [CO2] = 13.2, [HCO3] = 12, pH = 6.06: lethalIf add 12 mM H+ to body
– Body is open through lungs, all extra CO2 expelled
– [CO2] = 1.2, [HCO3] =12, pH = 7.1
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Kidneys CompensationKidneys CompensationChanges the amount of hydrogen excreted
and bicarbonate retained pH (acid) = kidneys excrete more H+ and
retain more bicarbonate so HCO3
More powerful but slower (hours to days)
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pHpH
pH?
uncompensated alkalosis
pH ↓ ?
uncompensated acidosis
Normal pH?
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PCOPCO22
Carried as carbonic acid , so it has an inverse ration with pH
Controlled by the lungs Normal range 35~ 45 mmHg
35 = hyperventilation or base (alkalosis) 45 = hypoventilation or acidic (acidosis)
[H2CO3]: 40×0.03=1.2mmol/L
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HCOHCO33--
Measurement of amount of bicarbonate in blood
Normal range 22~ 26 mmol/L, Controlled by kidneys 22 = acidosis 26 = alkalosis
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Hendersen-Hasselbalch equationHendersen-Hasselbalch equation
)(
)(]-[
2
3
Acid
Base
CO
HCO
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If = 1 pH = 6.12
3 ][
CO
HCO
If = 10 pH = 7.12
3 ][
CO
HCO
If = 20 pH = 7.42
3 ][
CO
HCO
If = 30 pH = 7.62
3 ][
CO
HCO
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Base ExcessBase Excess
Indication of how much extra base is available to the body
Normal ABG: -2 to +2 -2 = acidic (acidosis)
+2 = base (alkalosis)
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PaOPaO22
Measures oxygen carried by red blood cells and dissolved in plasma
75-100mmHg <75=hypoxiadrops about 3-5mmHg for each decade after
30 years of age
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SaOSaO22
the actual amount of oxygen carried by Hb compared with the amount of oxygen that Hb is capable of carrying
95~100% Often measured by a probe that is attached to a fin
ger or earlobe decreased occurs in carbon monoxide poisoning a
nd hypoxia Unreliable if peripheral perfusion is poor or in the
presence of nail polish, excessive movement
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Comparison with PO2 values Comparison with PO2 values
98% 100mmHg
95% 80mmHg
89% 60mmHg
84% 50mmHg
35% 20mmHg
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Review of Normal ABGReview of Normal ABG
pH 7.35 – 7.45pCO2 35 – 45pO2 75 – 100HCO3
- 22 – 26
SaO2 95%
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Thank youThank you