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 Arterial Blood Gases (ABGs) Arterial Blood Gases (ABGs)

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 ABG Definition ABG Definition

Blood gases measure the pH (acidity),Blood gases measure the pH (acidity),oxygen content, and carbon dioxideoxygen content, and carbon dioxide

content of the blood. Usually, blood gasescontent of the blood. Usually, blood gasesare used to analyze the arterial blood. Inare used to analyze the arterial blood. Inrarer cases, venous blood may be used.rarer cases, venous blood may be used.

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Why do ABGsWhy do ABGs

The test is used to evaluate respiratoryThe test is used to evaluate respiratorydiseases and conditions that affect thediseases and conditions that affect the

lungs. It is used to determine thelungs. It is used to determine theeffectiveness of oxygen therapy. The acideffectiveness of oxygen therapy. The acid--base component of the test also givesbase component of the test also givesinformation on how well the kidneys areinformation on how well the kidneys are

functioning.functioning.

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How is the test performedHow is the test performed

The test is performed by collecting a sample of blood

from an artery. Using a small needle, the sample may be

collected from the radial artery in the wrist, the femoral

artery in the groin, or the brachial artery in the arm.

Before blood is drawn, the circulation to the hand may

be tested (if the wrist is the site). After the blood is

drawn, pressure must be applied to the puncture site for 

at least 5 minutes to completely stop the bleeding.

The test must be sent to the laboratory for analysis

immediately, or the accuracy of the results cannot be

guaranteed

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Obtaining the specimenObtaining the specimen

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Normal ValuesNormal Values

pH of 7.35 to 7.45pH of 7.35 to 7.45

Partial pressure of oxygen (PaO2)Partial pressure of oxygen (PaO2) -- 80 to80 to

100 mm Hg100 mm Hg Partial pressure of carbon dioxide (PaCO2)Partial pressure of carbon dioxide (PaCO2)

-- 35 to 45 mm Hg35 to 45 mm Hg

BicarbonateBicarbonate -- (HCO3)(HCO3) -- 22 to 26 mEq/liter22 to 26 mEq/liter Oxygen saturation (SaO2)Oxygen saturation (SaO2) -- 94% to 100%94% to 100%

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pHpH

pHpH Measures the relationship between acidsMeasures the relationship between acidsand bases in the blood.and bases in the blood.

7.357.35   7.45 (mean 7.40)7.45 (mean 7.40)

If pH is low = more acid in blood (<7.35)If pH is low = more acid in blood (<7.35)

If pH is high = more base in blood (>7.45)If pH is high = more base in blood (>7.45)

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PaO2PaO2

Reflects the lungs ability to oxygenate theReflects the lungs ability to oxygenate thebloodblood

8080--100100

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PaCO2PaCO2

 A true measure of alveolar ventilation A true measure of alveolar ventilation

Regulated by the rate and depth of respirationRegulated by the rate and depth of respiration

3535   4545

< 35 = Resp. alkalosis< 35 = Resp. alkalosis

>45 = Resp. acidosis>45 = Resp. acidosis

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HCO3HCO3

Indicates the amount of bicarbonate in theIndicates the amount of bicarbonate in thebloodblood

 Abnormal level reflects a metabolic Abnormal level reflects a metabolicproblem or the patient may beproblem or the patient may becompensating for a respiratory problemcompensating for a respiratory problem

22 22 --2626

< 22 = Metabolic acidosis< 22 = Metabolic acidosis

> 26 = Metabolic alkalosis> 26 = Metabolic alkalosis

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Base Excess (BE)Base Excess (BE)

Difference between the acidDifference between the acid--base levels inbase levels inthe bloodthe blood

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Respiratory AcidosisRespiratory Acidosis

pH = < 7.35pH = < 7.35

PaCO2 = > 45PaCO2 = > 45

 Alveolar hypoventilation Alveolar hypoventilation

S/SS/S   diminished respiration, HA, confusiondiminished respiration, HA, confusion

Treatment Treatment   Improve ventilationImprove ventilation

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Respiratory AlkalosisRespiratory Alkalosis

pH = > 7.45pH = > 7.45

PaCO2 = < 35PaCO2 = < 35

HyperventilationHyperventilation

S/SS/S   Hyperventilation, tetany, confusionHyperventilation, tetany, confusion

Treatment Treatment   Correct ventilationCorrect ventilation

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Metabolic AcidosisMetabolic Acidosis

pH = < 7.35pH = < 7.35

HCO3 = < 22HCO3 = < 22

Excess loss of bicarbonateExcess loss of bicarbonate

Treatment Treatment   Give IV bicarbonateGive IV bicarbonate

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Metabolic AlkalosisMetabolic Alkalosis

pH = > 7.45pH = > 7.45

HCO

3 = >26

HCO

3 = >26

Retained bicarbonateRetained bicarbonate

Treatment Treatment   Hydrogen & ChlorideHydrogen & Chloridereplacement replacement 

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Care PlanCare Plan

Ineffective breathing patternIneffective breathing pattern

Ineffective airway clearanceIneffective airway clearance

Impaired gas exchangeImpaired gas exchange

PainPain

 Anxiety Anxiety

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Practice ProblemsPractice Problems

 Apply your principles Apply your principles

 Assess pH Assess pH Label pH = Acidosis or AlkalosisLabel pH = Acidosis or Alkalosis

 Assess PaCO2 & HCO3 Assess PaCO2 & HCO3

Find the gas that matchesFind the gas that matches Treat symptoms and cause to correct Treat symptoms and cause to correct 

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Questions?Questions?