Data Interpretation: Arterial Blood Gas

Question 1

What are the 2 main conclusions to find in ABG interpretation?

Answer 1

If the patient has respiratory acidosis or respiratory alkalosis

If the patient has type 1 or type 2 respiratory failure

Question 2

What is the normal pH range in ABG interpretation?

Answer 2

pH 7.35-7.45

Question 3

Can a patient with respiratory acidosis or alkalosis still have a normal pH value?

Answer 3

Yes, if there is full compensation then the pH will be within normal range but near the range limits

Question 4

What value should you first look at in ABG interpretation?

Answer 4

The pH value

Question 5

In ABG interpretation, which 2 values should you look at after looking at the pH value?

Answer 5

CO2 value and HCO3- value

If patient’s pH is acidotic or alkalotic, these values indicate if its due to respiratory or metabolic causes

Question 6

In ABG interpretation, what is meant by respiratory acidosis?

Answer 6

The pH is normal/acidotic and is driven primarily by a high CO2 level in the blood

Question 7

In ABG interpretation, what is meant by respiratory alkalosis?

Answer 7

The pH is normal/high which is primarily driven by a low CO2 level

Question 8

In ABG interpretation, what is meant by uncompensation, partial or full compensation?

Answer 8

Partial compensation: pH value is not within normal range, secondary component is high

Full compensation: pH value is within normal range, secondary component is high

Uncompensation: pH value is not within normal range, secondary component is normal

Question 9

In ABG interpretation, what is meant by metabolic acidosis?

Answer 9

The pH value is normal/low which is primarily driven by low HCO3- value

Question 10

In ABG interpretation, what is meant by metabolic alkalosis?

Answer 10

The pH value is normal/high which is primarily driven by high HCO3- value

Question 11

What is the normal range of PaCO2, in ABG interpretation?

Answer 11

PaCO2: 4.5-6 kPa OR 35-45 mmHg

Question 12

What is the normal range of HCO3-, in ABG interpretation?

Answer 12

HCO3-: 22-26 mmol/L

Question 13

In ABG interpretation, what is meant by respiratory acidosis with full metabolic compensation?

Answer 13

pH: 7.35-7.45

PaCO2: (high) more than 6kPa/45mmHg

HCO3-: (high) more than 26 mmol/L

Question 14

In ABG interpretation, what is meant by respiratory acidosis with partial metabolic compensation?

Answer 14

pH: (low) below 7.35

PaCO2: (high) more than 6kPa/45mmHg

HCO3-: (high) more than 26 mmol/L

Question 15

In ABG interpretation, what is meant by uncompensated respiratory acidosis?

Answer 15

pH: (low) below 7.35

PaCO2: (high) more than 6 kPa/45mmHg

HCO3-: (normal) 22-26 mmol/L

Question 16

In ABG interpretation, what is meant by respiratory alkalosis with full metabolic compensation?

Answer 16

pH: (normal) 7.35-7.45

PaCO2: (low) less than 4.5 kPa/35 mmHg

HCO3-: (low) less than 22 mmol/L

Question 17

In ABG interpretation, what is meant by respiratory alkalosis with partial metabolic compensation?

Answer 17

pH: (high) more than 7.45

PaCO2: (low) less than 4.5 kPa/35 mmHg

HCO3-: (low) less than 22 mmol/L

Question 18

In ABG interpretation, what is meant by respiratory alkalosis with no compensation?

Answer 18

pH: (high) more than 7.45

PaCO2: (low) less than 4.5 kPa/35 mmHg

HCO3-: (normal) 22-26 mmol/L

Question 19

In ABG interpretation, what is meant by metabolic acidosis with full respiratory compensation?

Answer 19

pH: (normal) 7.35-7.45

PaCO2: (low) less than 4.5 kPa/35 mmHg

HCO3-: (low) less than 22 mmol/L

Question 20

In ABG interpretation, what is meant by metabolic acidosis with partial respiratory compensation?

Answer 20

pH: less than 7.35

PaCO2: (low) less than 4.5 kPa/35 mmHg

HCO3-: (low) less than 22 mmol/L

Question 21

In ABG interpretation, what is meant by metabolic acidosis with no compensation?

Answer 21

pH: (less) more than 7.35

PaCO2: normal

HCO3-: (low) less than 22 mmol/L

Question 22

In ABG interpretation, what is meant by metabolic alkalosis with full respiratory compensation?

Answer 22

pH: 7.35-7.45

PaCO2: (high) more than 6kPa/45 mmHg

HCO3-: (high) more than 26 mmol/L

Question 23

In ABG interpretation, what is meant by metabolic alkalosis with partial respiratory compensation?

Answer 23

pH: more than 7.45

PaCO2: (high) more than 6kPa/45 mmHg

HCO3-: (high) more than 26 mmol/L

Question 24

In ABG interpretation, what is meant by metabolic alkalosis with no compensation?

Answer 24

pH: more than 7.45

PaCO2: normal

HCO3-: (high) more than 26 mmol/L

Question 25

In ABG interpretation, what is meant by mixed acidosis?

Answer 25

Acidosis is caused by metabolic and respiratory causes pH: less than 7.35 PaCO2: (high) more than 6kPa/45mmHg HCO3-: (low) less than 22 mmol/L

Question 26

In ABG interpretation, what is meant by mixed alkalosis?

Answer 26

Alkalosis is caused by metabolic and respiratory causes pH: more than 7.45 PaCO2: (low) less than 4.5kPa/35mmHg HCO3-: (high) more than 26 mmol/L

Question 27

What are the causes of respiratory acidosis? SAINTS

Answer 27

Hypoventilation S: CNS depression eg. Stroke, drugs eg. opiate overdose A: Airway obstruction eg. COPD I: Increased dead space eg. pulmonary embolism N: Neuromuscular diseases T: Trauma to chest S: Sleep apnea

Question 28

What are the causes of respiratory alkalosis?

Answer 28

Hyperventilation and tachycardia: Anxiety, fear Pregnancy Hypoxia High altitudes Fever

Question 29

What are the causes of metabolic alkalosis? VOMED

Answer 29

V: Vomiting or aspiration O: Overcorrection of chronic high CO2 or any acidosis eg. diabetic ketoacidosis M: Mineralocorticoid excess eg. Cushing's E: Early sepsis D: Diuretics or diarrhoea

Question 30

What are the causes of metabolic acidosis? CAT MUDPILE

Answer 30

Congential heart failure, carbon monoxide Alcoholic ketoacidosis Toluline (methybenzine – used as an inhaled narcotic) Methanol, metformin Uraemia Diabetic Ketoacidosis Paracetamol Iron, isoniazid Lactate Ethanol, ethylene glycol Salicylate eg. aspirin

Question 31

Which values on an ABG indicate type 1 respiratory failure?

Answer 31

PaO2: less than 8 kPa (hypoxaemia) PaCO2: 4.5-6 kPa (normocapnia)

Question 32

Which values on an ABG indicate type 2 respiratory failure?

Answer 32

PaO2: less than 8 kPa (hypoxaemia) PaCO2: More than 6 kPa (hypercapnia)