05/04/23 1

ABG ANALYSIS

05/04/23 2

Purpose of ABG Analysis:

To evaluate how effective the lungs are in bringing oxygen to the blood and removing carbon dioxide from it.

05/04/23 3

Radial artery is the most frequently used artery for ABGs

05/04/23 4

Allen’s Test Patient clenches fist Apply firm pressure to

radial & ulnar arteries Patient relaxes hand Release pressure on

the ulnar artery Palm should flush

within 5-15 secs

05/04/23 5

Arterial Blood Sampling Prep site Pierce skin over arterial at a 60-

90° angle Obtain 3 mL of blood without

air bubbles Twirl syringe to mix heparin

with sample Place in ice Hold pressure for 5-10 minutes Wait 30 minutes before drawing

sample if O2 setting changed

05/04/23 6

Documentation Must Include:

Presence of positive Allen’s Test Date and time of procedure Site chosen Patient’s tolerance to procedure FiO2 patient is on at the time the sample is drawn

Chart By Exception: Adverse side effects of procedure Length of time pressure applied, if greater than 5 minutes Negative Allen’s Test

05/04/23 7

Key to body’s response to acid-base imbalance is:

Hydrogen Ion Concentration

When H+ HCO3- + H+ H2CO3 CO2 + H2O

When H+ CO2 + H2O H2CO3 HCO3- + H+

05/04/23 8

05/04/23 9

Components of ABG pH- Hydrogen ion concentration in plasma PaCO2- Partial pressure of CO2 dissolved in

plasma HCO3- Bicarbonate concentration in plasma PaO2- Partial pressure of O2 dissolved in

plasma Base Excess- The amount of base

05/04/23 10

Interpretation of ABGs

05/04/23 11

pH pH reflects the hydrogen ion (H+)

concentration of plasma pH range

0= pure acid 14= pure base 7.0 =neutral (equal parts acids/base)

Normal pH in the blood = 7.35- 7.45

05/04/23 12

AcidosisDecrease in pH resulting from an increase in

hydrogen ion concentration

H+

05/04/23 13

AlkalosisIncrease in pH resulting from a decrease in

hydrogen ion concentration

05/04/23 14

FOUR STEPS to evaluate ABGs

1. Evaluate each number2. Check pH to determine cause of imbalance3. Find value that matches acid-base status of pH4. Determine extent of compensation:

Absent Partial Complete

05/04/23 15

Step 1 evaluating each number Is the pH on the acid or

alkaline side? What does the PaCO2

show? What does the HCO3

show? Does the PaO2 show

hypoxemia? Buffer

Base

HCO3 ph

acid

CO2

PO2 hgb

05/04/23 16

Step 2 Is the pH on the acid or alkaline side?

Normal pH 7.35 - 7.45

pH < 7.40 = acidosis

pH > 7.40 = alkalosis

05/04/23 17

Step 3 Does the PaCO2 match the pH?

Normal PaCO2 35-45 mm Hg

PaCO2 > 45

PaCO2 < 35

05/04/23 18

Step 3Does the HCO3 match the pH? Normal HCO3 22 - 26 mEq/L

HCO3 < 22

HCO3 > 26

05/04/23 19

Which System is Involved? Lungs

(Respiratory)

Kidneys(Metabolic)

05/04/23 20

Step 4What is the extent of compensation?

Absent - value that doesn’t match the pH is normal Partial - value that doesn’t match the pH & pH are

above or below normal Complete - value that doesn’t match the pH is above

or below normal, but the pH is normal

05/04/23 21

Metabolic System compensates for the Respiratory System Respiratory acidosis

Kidneys re-absorb more bicarbonate

Respiratory alkalosis Kidneys excrete more bicarbonate

05/04/23 22

Respiratory System compensates for Metabolic abnormalities Metabolic acidosis

Hyperventilation lowers PaCO2 so the ratio of Bicarbonate to Carbonic acid returns to normal

Metabolic alkalosis Hypoventilation so the PaCO2 rises and the ratio of

Bicarbonate to Carbonic Acid returns to normal

05/04/23 23

OxygenOxygen is carried in the blood in two ways: In combination with hemoglobin Dissolved in plasma

97% bound by Hgb

3% dissolved in plasma

05/04/23 24

PaO2

Normal on room air 80-100 mm Hg Mild hypoxemia = 60-80 mmHg Moderate hypoxemia = 40-60 mmHg Severe hypoxemia = below 40 mmHg

05/04/23 25

Does the PaO2 show hypoxemia?

Is the client hypoxemic? Is the client’s PaO2 or SaO2 low? Is the client anemic?

•Normal PaO2 is 80-100

•Normal SaO2 is 95-100

05/04/23 26

ABG Example pH 7.48 PaCO2 32 HCO3 22 Normal

Uncompensated Respiratory Alkalosis

05/04/23 27

Acid-Base DisordersABG Disorder Possible Causes Signs and

SymptomsRespiratory Acidosis CNS depression

(barbiturate or sedative OD)AsphyxiaHypoventilationCOPD Respiratory muscle weakness (Guillain-Barre)Chest wall abnormality (obesity)

DiaphoresisHeadacheTachycardiaConfusionRestlessnessApprehension

05/04/23 28

Acid-Base DisordersABG Disorder Possible Causes Signs and

SymptomsRespiratory Alkalosis Hyperventilation

Respiratory stimulation (septicemia, encephalitis, brain injury, salisylate poisoning)Gram-negative bacteremia

Rapid, deep respirationsParesthesiasLight-headednessTwitchingAnxietyFear

05/04/23 29

Acid-Base DisordersABG Disorder Possible Causes Signs and

SymptomsMetabolic Acidosis HCO3- depletion

from diarrheaExcessive production of organic acidsInadequate excretions of acids from renal diseaseDKA, Lactic acidosisShock, GI fistulas

Rapid, deep breathingFruity breathFatigueHeadacheLethargyNauseaVomitingComa

05/04/23 30

Acid-Base DisordersABG Disorder Possible Causes Signs and

SymptomsMetabolic Alkalosis Loss of hydorchloric

acid from vomiting or NG suctioningLoss of hydrogen ions due to increased renal excretion from diuretic therapyExcessive alkali ingestion

Slow, shallow respirationsMuscle twitchingHypertonic musclesRestlessnessTetany (convulsion)Coma

05/04/23 31

ABG Case Studies

Exercises

05/04/23 32

A patient was admitted to the ICU after suffering a stroke. The third day, the patient is more lethargic than the day before. His lung sounds are diminished in the lower lobes. ABGs are drawn and the following results were obtained.

pH 7.33 PaCO2 55 HCO3 29 PaO2 60

05/04/23 33

What is the ABG result for the CVA patient? 25% 25%25%25%

1. Comp. resp. acidosis with mild hypoxemia

2. Part. Comp. resp. acidosis with mild hypoxemia

3. Part. Comp. metabolic acidosis with mod. hypoxemia

4. Comp. metabolic alkalosis with mod. hypoxemia

05/04/23 34

A postop cholecystectomy patient is hyperventilating due to anxiety and pain. She complains of tingling and numbness in her fingers. Her ABG values are as follows:

pH 7.55 PaCO2 28 HCO3 24 PaO2 90

05/04/23 35

What is the ABG result for the S/P cholecystectomy patient?

25% 25%25%25%

1. Comp. resp. alkalosis with normal oxygenation

2. Part. comp. resp. alkalosis with mild hypoxemia

3. Uncomp. Resp. alkalosis with normal oxygenation

4. Comp. metabolic alkalosis with mild hypoxemia

05/04/23 36

A patient has acute tubular necrosis, brought on by cardiopulmonary arrest. His ABG results are as follows:

pH 7.32 PaCO2 34 HCO3 17 PaO2 95

05/04/23 37

What is the ABG result for the ATN patient?25% 25%25%25%

1. Comp. resp. acidosis with normal oxygenation

2. Comp. metabolic alkalosis with normal oxygenation

3. Uncomp. metabolic acidosis with mild hypoxemia

4. Part. comp. metabolic acidosis with normal oxygenation

05/04/23 38

A patient has a history of pancreatitis. He has been vomiting for several days PTA. He presently has a NGT to suction. His ABG values are as follows:

pH 7.52 PaCO2 49 HCO3 40 PaO2 93

05/04/23 39

What is the ABG result for the patient with pancreatitis?

25% 25%25%25%

1. Part. comp. metabolic alkalosis with normal oxygenation

2. Comp. metabolic acidosis with normal oxygenation

3. Comp. respiratory alkalosis with normal oxygenation

4. Part. comp. resp. alkalosis with normal oxygenation

05/04/23 40

A patient has a history of smoking three packs of cigarettes for 40 years and has a history of COPD. His ABG’s are as follows:

pH 7.35 PaCO2 70 HCO3 30 PaO2 55

05/04/23 41

What is the ABG result for the COPD patient?

25% 25%25%25%1. Part. comp. resp. acidosis, mod.

hypoxemia 2. Comp. metabolic alkalosis, mod.

hypoxemia3. Comp. resp. acidosis, mod.

hypoxemia4. Part. comp. metabolic acidosis,

mod. hypoxemia

05/04/23 42

Please click on the “Escape” key to exit this PowerPoint Presentation.Thank you.