Arterial Blood Gases & Acid Base Regulation

Question 1

What should be in equilibrium with pCO2 (theoretical)?

Answer 1

Bicarbonate

Question 2

What is FMetHb?

Answer 2

ferritin NOT ferrous in the haem- molecule that is unable to bind O2

Question 3

What does acidosis need to correct?

Answer 3

alkalosis

Question 4

What does hyperventilation result in?

Answer 4

increased CO2 clearance

Question 5

What are the 4 key aspects found from an ABG?

Answer 5

• what is the type of imbalance?
• what is the aetiology of imbalance?
• any homeostatic compensation?
• oxygenation?

Question 6

How to assess compensation?

Answer 6

• both values should change
• only one indicates it is UNcompensated
• changes in pH suggest partial compensation

Question 7

What is base excess?

Answer 7

the difference between the actual bicarbonate and the expected bicarbonate

Question 8

How do you calculate pH?

Answer 8

-log10[H+]

Question 9

How do you calculate [H+]?

Answer 9

10^-pH

Question 10

What is an acid?

Answer 10

any molecule that has a loosely bound H+ ion that it can donate

Question 11

What is an base?

Answer 11

an anionic (-ive) molecule that can reversibly bind protons

Question 12

What proportion of acid is respiratory (CO2) or metabolic (lactic, HCl…)?

Answer 12

about 95:5

Question 13

What does alkalosis need to correct?

Answer 13

acidosis

Question 14

What can cause a rapid compensation?

Answer 14

changes in ventilation change CO2 ventilation, altering pH

Question 15

What can cause a slow compensation?

Answer 15

Changes in HCO3- and H+ retention/secretion in the kidneys, lead to changes in pH

Question 16

How long does slow consumption take?

Answer 16

up to days

Question 17

What is acidosis/alkalosis?

Answer 17

conditions that cause a change in pH

Question 18

What is alkalaemia/acidaemia?

Answer 18

whether pH is above/below 7.35-7.45.

Question 19

What are the different types of imbalance?

Answer 19

• acidosis
• alkalosis
• normal

Question 20

What are the different aetiologies of an imbalance?

Answer 20

• respiratory (acidosis/alkalosis)
• metabolic (acidosis/alkalosis)
• mixed (respiratory and metabolic)
• nroaml

Question 21

What are the different forms of homeostatic compensation?

Answer 21

• uncompensated
• partially compensated
• fully compensated

Question 22

What are the different forms of oxygenation?

Answer 22

• Hypoxaemia
• Normoxaemia
• Hyperoxaemia

Question 23

How do you differentiate between respiratory and metabolic causes?

Answer 23

look at the CO2 level

Question 24

What would indicate compensation?

Answer 24

• changes in PaO2 and PaCO2

- changes in pH (if not normal, partial)

Question 25

What do changes in BE indicate?

Answer 25

decrease if in respiratory alkalosis - for compensation (or vice versa)

Question 26

What is a normal PaCO2?

Answer 26

4.7-6.4 kPa

Question 27

What is a normal base excess?

Answer 27

-2 - 2

Question 28

What is a normal PaO2?

Answer 28

10-13.5kPa

Question 29

What can indicated partial compensation?

Answer 29

changes in PaCO2 or BE that would help with alkalosis/acidosis but no change in pH yet

Question 30

What is seen in uncompensated respiratory acidosis?

Answer 30

- low pH - high PaCO2 - normal BE

Question 31

What is seen in partially compensated respiratory acidosis?

Answer 31

- low pH - high PaCO2 - high BE

Question 32

What is seen in fully compensated respiratory acidosis?

Answer 32

- normal pH - high PaCO2 - high BE

Question 33

What is seen in uncompensated respiratory alkalosis?

Answer 33

- high pH - low PCO2 - normal BE

Question 34

What is seen in partially compensated respiratory alkalosis?

Answer 34

- high pH - low PCO2 - low BE

Question 35

What is seen in fully compensated respiratory alkalosis?

Answer 35

- normal pH - low PCO2 - low BE

Question 36

What is seen in uncompensated metabolic acidosis?

Answer 36

- low pH - normal PaCO2 - low BE

Question 37

What is seen in partially compensated metabolic acidosis?

Answer 37

- low pH - low PaCO2 - low BE

Question 38

What is seen in fully compensated metabolic acidosis?

Answer 38

- normal pH - low PaCO2 - low BE

Question 39

What is seen in uncompensated metabolic alkalosis?

Answer 39

- high pH - normal PCO2 - high BE

Question 40

What is seen in partially compensated metabolic alkalosis?

Answer 40

- high pH - high PCO2 - high BE

Question 41

What is seen in fully compensated metabolic alkalosis?

Answer 41

- normal pH - high PCO2 - high BE

Question 42

What mechanism is used to compensate for respiratory acidosis?

Answer 42

chronic: increased HCO3- retention

Question 43

What can cause respiratory acidosis?

Answer 43

hypoventilation

Question 44

What can cause respiratory alkalosis?

Answer 44

hyperventilation

Question 45

What mechanism is used to compensate for respiratory alkalosis?

Answer 45

chronic phase: reduced HCO3- retention/reabsorption

Question 46

What can cause metabolic acidosis?

Answer 46

- diarrhoea | - H+ gaining/HCO3- losing conditions

Question 47

What mechanism is used to compensate for metabolic acidosis?

Answer 47

hyperventilation

Question 48

What can cause metabolic alkalosis?

Answer 48

- vomiting | - H+ losing/HCO3- gaining conditions

Question 49

What mechanism is used to compensate for metabolic alkalosis?

Answer 49

hypoventilation