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8/11/2019 Final Abg Up to Date

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Definitions concerning acid base

disorders.

Systematic approach to acid-base

interpretation.

How to diagnose simple acid base

disorders?


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Acid

BasepH

Buffer

Acidemia

AlkalemiaAcidosis

Alkalosis

Acid Base Terminology


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Acid:

Tends to donate a proton (H+)

HCl (Acid)H ++ Cl

Base:Tends to accept a proton (H +)

NH3 (Base) + H+NH4+


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pH:

pH devised to facilitate working with small [H

+

]

pH = -log [H

+

]

Lower the pH more acidic

Higher the pH more alkaline

Acid BaseTerminology


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Balance done by buffer

system


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Bicarbonate buffer system

CO2 + H2O H2CO3 HCO3- + H+

By carbonic anhydrase enzymeImmediately act within sec


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Respiratory CO2 elimination

-Fast onset (min)

-Alveolar ventilation responds to PCO2

changes

CO

2CO2 CO

2

CO

2

CO

2CO

2

Cell

Metabolism


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Respiratory regulation

When breathing is increased, the blood

carbon dioxide level decreases and theblood becomes moreBasic.

When breathing is decreased, the bloodcarbon dioxide level increases and the

blood becomes moreAcidic.

It works within minutes.


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Kidney regulation

This work within hours or days.

The kidney generate& reabsorb Hco3 from tubularlumen and excrete hydrogen ion in the tubularlumen


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1. Extracellular buffering

Immediately acts

The first-responder

2.

Respiratory regulation of CO2 elimination

Fast onset (minutes)

Alveolar ventilation responds to PCO2

3. Renal regulation of H+/HCO3- excretion

Slower onset (

48 hr)

Kidney excretes excess [H+]


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pH 7.35-7.45

pCO2 35-45mmHgpO2 80-100mmHg

O2 Sat. 95-100%

HCO3 22-26mEq/L

Acid base balance

Blood tests Reference range


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Arterial blood gas (ABG) test

measures: Blood (pH)

The oxygen tension(PaO2)and saturation

(SaO2).

The Carbon dioxidetension (PaCO2)

TheHCO3level


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value

This test is used to:

Diagnosis of pH disturbance by

check the (PaCO2 and HCO3).Check the degree of body

compensation

Check the degree of blood oxygen

(tension and saturation) diagnosis

of hypoxia


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How It Is Done

Sample of arterial blood :

From the wrist OR From the groin

(radial artery) (femoral artery)


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(?Why)

Because you may give local anesthetic as

collection of blood from an artery is more

painful than vein as arteries are deeperand protected by nerves.


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"emia" - alterations in blood pH

pH < 7.35acidemia

pH > 7.45

alkalemia


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"os is" - pathologic process that may results in

alterations in blood pH primary process.

Acidosis (H)

By

PCO2 (> 45) or HCO3 (


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AlalKemia

AciDemia

w v


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How to solve problem?

Acid Base interpretation

1- look to ph

Ph 7.45 alkaemia

2-Change in HCO3 : metabolic disorder

3-Change in PCO2 : respiratory disorder


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Problem (1)

Ph : 7.30

PCO2 : 58

HCO3 : 25


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RESPIRATIOY ACIDOSIS


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Problem (2)

Ph : 7.55

PCO2 : 20

HCO3 : 26


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RESPIRATORY ALKALOSIS


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Problem (3)

Ph : 7.31

PCO2 : 34

HCO3 : 19


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Metabolic acidosis


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Problem (4)

Ph : 7.55

PCO2 : 37

HCO3 : 35


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METABOLIC ALKALOSIS


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Understand ?


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pH 7.48

pCO2 29mmHgHCO3 24mEq/L

Step 1. The pH is ----------Step 2. The PCO2 is ---------Step 3. The HCO3 is ---------The full diagnosis for this ABG is: -

Respiratory alkalosis


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pH 7.32


Step 1. The pH is ----------Step 2. The CO2 is ---------Step 3. The HCO3 is ---------

The full diagnosis for this ABG is: -----------------------

Respiratory acidosis


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pH 7.31


Metabolic acidosis




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pH 7.50




Metabolic alkalosis


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