Blood Gas Analysis & - PowerPoint Presentation

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Blood Gas Analysis &Blood Gas Analyser

Radadiya Shraddha

Kevadiya Pinal

Goti Priyanka

Thummar Vaishali

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INTRODUCTION

An arterial blood gas (ABG) analysis measures

pH (Concentration of H+)

pO

₂

(Partial Pressure of O2)

pCO

₂

(

Partial Pressure of

CO2

)

HCO

₃⁻

(Bicarbonate)

Base excess

Anion gap

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PURPOSE of ABG

To Know metabolic

or respiratory acid-base

disorder

Differentiate Metabolic & Respiratory disorder

Differentiate Acidosis & Alkalosis

Differentiate stage of compensation

Uncompensated

Partial compensated

Fully Compensated ,

To Monitor the patient with ventilator support.

To monitor the patient with respiratory disorder.

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Procedure

Sterilized

skin.

Anesthetize

site.

Take heparinized glass

syringe ( Why glass syringe ?)

Expel any residual heparin out through the needle.

Feel along the course of the radial

artery / brachial artery / femoral artery

Palpate for maximum pulsation with the middle and index finger.

Hold

the needle at a 45-60

degree angle to the skin surface.

Once the artery is punctured, arterial pressure does pulsating flow of blood in the syringe.

After collection, withdraw the needle and apply pressure over the site with a dry sponge.

Then bend

needle to prevent gas exchange from

air or

Block needle with rubber.

Transport syringe with bag of ice.

Continue to maintain pressure of puncture site for up to 10 minutes. (If patient is on anticoagulant medication apply pressure for 15 minutes).

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Principle of Ion Selective Electrode

By the specific electrode particular ion or gas component is diffused through the specific membrane & it will make change in electrical potential.That change in electrical potential reflect concentration of gas in Blood.

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pH

pH is equal to the negative log of the hydrogen ion concentration pH = - log [H⁺]Membrane : Glass membrane

STATE

pH

NORMAL

7.35 – 7.45

ACIDOSIS

<7.35

ALKALOSIS

>7.45

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Leaky Membrane / Ceramic Junction of Reference electrode

At Reference electrode

Made up of Ceramic / Teflon membrane

Allow to diffuse

KCl

Why KCL get diffuse ?????

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Principle

Two electrode : Reference electrode

Glass electrode

In Reference electrode:

HgCl

₂

+ KCl

→

K⁺ + Cl⁻ + e⁻

(e⁻ is measured by voltmeter)

In Glass electrode:

Selective for H⁺ ion

Buffer in glass membrane neutralised H⁺ & make changes in electron potential.

That change measure with respect to ref electrode.

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Why saturated KCL is there as buffer in reference electrode?

KCl continuously react with Ag/AgCl₂

Continuously KCl breakdown to = K⁺ & Cl

⁻

KCl get used up

So KCl

is there as saturated form / highly concentrated.

To compensate loss of KCl

To keep equilibrium in breakdown of KCl ,during

all

measurement

.

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pCO₂

It is partial pressure of CO₂ in arterial blood. PrincipleTwo electrode:- reference electrode - glass electrodeGas permeable membrane:CO2 diffuse across the outer membraneOuter membrane is not permeable for HCO₃⁻ & H⁺CO₂ + H₂O H₂CO₃ ↔ H+ + HCO₃⁻

Carbonic anhydrase

STATE

pCO

₂(mmHg)

NORMAL

38 - 42

HYPOCAPNIA

<38

HYPERCAPNIA

>42

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pO₂

The

partial pressure of oxygen that is dissolved in arterial blood.

New Born – Acceptable range 40-70 mmHg.

pO₂

determination is carried out to assess the

O₂

carrying capacity of blood Hb

.

The PO

2

electrode basically consists of two terminals:

(1) The cathode, made of Platinum (negatively charged)

(2) The anode, made of Ag/ AgCl (positively charged)

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Principle

At Cathode;

O

₂

+ 2H

₂

O + 4e⁻

→ 2H₂O₂ + 2e⁻ → 4OH⁻

Electron came from battery.

End product, OH⁻ is neutralised by sat. KCl buffer solution.

4OH⁻ + 4KCl → 4KOH + 4Cl⁻

At Anode;

AgCl → Ag⁺ + Cl⁻ + e⁻

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STATE

pO₂ (mm

Hg)

NORMAL

80-100

HYPOXEMIA

<80

HYPEROXEMIA

>120

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HCO3⁻

Bicarbonate determined by finding out the actual bicarbonate conc. of plasma separated from blood taken anaerobically.Unit : milliequivalents/ liter.It can be calculated from pH and pCO₂ by using the Henderson-Hasselbalch equation. pH = pK + log [pK=6.1;for HCO₃⁻/CO₂ in plasma]Normal range: 22 -28 mEq/L

 

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Base Excess

Base excess is the defined as the amount of strong acid required to titrate blood to pH 7.40 at 37°C and pCO

₂ 40 mmHg.

Normal range : -2.0 to +2.0

Base excess = Alkalosis

Base deficit = Acidosis

Fully calculated value.

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BE Calculation:

Base excess = 0.93 (HCO

₃⁻

- 24.4 + 14.8 (pH - 7.4 ))

= 0.93*HCO

₃⁻

+ 13.77pH – 124.58

Base deficit

:

defined as the amount of

base

required to titrate blood to pH 7.40 at 37°C and pCO

₂ 40 mmHg.

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Disturbances in acid-base balance

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  pH(7.35 – 7.45)pO2(95 - 100)pCO2(32 - 44)HCO3-(22 - 26)MetabolicacidosisUncompensatedLowNormalNormalLowPartially compensatedLowNormalLowLowFully compensated7.35NormalLowLowMetabolicAlkalosisUncompensatedHighNormalNormalHighPartially compensatedHighNormalHighHighFully compensated7.45NormalHighHighRespiratoryacidosisUncompensatedLowNormal/ LowHighNormalPartially compensatedLowNormal/LowHighHighFully compensated7.35Normal/LowHighHighRespiratoryAlkalosisUncompensatedHighHigh / Normal /LowLowNormalPartially compensatedHighHigh / Normal /LowLowLowFully compensated7.45High / Normal /LowLowLow

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Anion gap

The anion gap is the difference between total number of cations and total number of anions in blood.

Anion gap = total no. of cations – total no. of anions

Normal anion gap is 6-12 meq/L.

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Loss of either Cl⁻ or HCO

₃⁻

Metabolic acidosisExamples: 1) Vomiting & diarrhea 2) Renal failure

Loss of negatively charged albumin

Retention of Cl⁻

& HCO₃⁻AlkalosisDecrease Na+Hypoalbuminemia

High anion gap

Low anion gap

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THANK YOU

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