ABG's

Question 1

What is the normal value of blood pH?

Answer 1

7.35-7.45

Question 2

What is the normal value of PaO2?

Answer 2

10.7-13.3 kPa

Question 3

What is the normal value of PaCO2?

Answer 3

4.7-6.0 kPa

Question 4

What is the normal value of HCO3 (bicarbonate)?

Answer 4

22-26 mmol/L

Question 5

What does a low PaO2 indicate?

Answer 5

hypoxia and respiratory failure

Question 6

What are the characteristics of type 1 respiratory failure?

Answer 6

low PaO2
normal PaCO2

Question 7

What are the characteristics of type 2 respiratory failure?

Answer 7

low PaO2
raised PaCO2

Question 8

When is a patient classed as acidotic?

Answer 8

if pH is under 7.35

Question 9

When is a patient classed as alkalotic?

Answer 9

if pH is over 7.45

Question 10

What effect does carbon dioxide have on the blood?

Answer 10

makes blood acidotic by breaking down into carbonic acid

Question 11

What type of acidosis is indicated by a low pH with a raised PaCO2?

Answer 11

respiratory acidosis - the patient is acutely retaining CO2, which is making their blood acidotic

Question 12

What is bicarbonate?

Answer 12

this is produced by the kidneys and acts as a buffer to neutralise acid in the blood

Question 13

What is indicated by a raised bicarbonate?

Answer 13

this indicates the patient chronically retains CO2, e.g., patients with COPD

Question 14

What type of alkalosis is indicated by a high pH with a low PaCO2?

Answer 14

respiratory alkalosis - the patient likely has a raised RR, so is breathing too fast and therefore getting rid of too much CO2

Question 15

What are the most common causes of respiratory alkalosis?

Answer 15

hyperventilation due to anxiety
patients with a PE

Question 16

How can you tell the difference between respiratory alkalosis due to hyperventilation and that due to a PE?

Answer 16

patients with a PE will have a low PaO2
patients with hyperventilation will have a high PaO2

Question 17

What type of acidosis is indicated by a low pH with low bicarbonate?

Answer 17

metabolic acidosis

Question 18

List the possible causes of metabolic acidosis

Answer 18

raised lactate
raised ketones
increased hydrogen ions
reduced bicarbonate

Question 19

What does raised lactate indicate?

Answer 19

anaerobic respiration is occurring, suggesting the patient is hypoxic

Question 20

What do raised ketones indicate?

Answer 20

diabetic ketoacidosis

Question 21

What can lead to increased hydrogen ions?

Answer 21

renal failure
type 1 renal tubular acidosis
rhabdomyolysis

Question 22

What can lead to reduced bicarbonate?

Answer 22

diarrhoea
renal failure
type 2 renal tubular acidosis

Question 23

What type of alkalosis is indicated by raised pH with raised bicarbonate?

Answer 23

metabolic alkalosis

Question 24

How can hydrogen ions be lost, therefore leading to metabolic alkalosis?

Answer 24

from the GI tract through vomiting
from the kidneys, due to increased activity of aldosterone

Question 25

How does increased aldosterone activity lead to metabolic alkalosis?

Answer 25

increased activity results in increased hydrogen ion excretion from the kidneys, therefore increasing the pH

Question 26

What can cause increased activity of aldosterone?

Answer 26

Conn's syndrome liver cirrhosis heart failure loop diuretics thiazide diuretics

Question 27

How can you identify metabolic compensation in respiratory acidosis?

Answer 27

pH may appear normal due to the compensation bicarbonate will be raised

Question 28

How can you identify metabolic compensation in respiratory alkalosis?

Answer 28

pH may appear normal due to the compensation bicarbonate will be low

Question 29

How can you identify respiratory compensation in metabolic acidosis?

Answer 29

CO2 will be reduced

Question 30

How can you identify respiratory compensation in metabolic alkalosis?

Answer 30

CO2 will be raised

Question 31

What does base excess indicate?

Answer 31

this is a marker of metabolic acidosis or alkalosis indicated the amount of bicarbonate in the blood