10. Acid-Base regulation

Question 1

Alkalaemia

Answer 1

Higher-than-normal pH of blood

Question 2

Acidaemia

Answer 2

Lower-than-normal pH of blood

Question 3

Alkalosis

Answer 3

Circumstances that will decrease [H+] and increase pH

Question 4

Acidosis

Answer 4

Circumstances that will increase [H+] and decrease pH

Question 5

Acid

Answer 5

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

Question 6

Why do we need to strictly maintain pH between 7.35 and 7.45?

Answer 6

Changes will alter the 3D structure of proteins (enzymes, hormones, protein channels)

Question 7

pH equation

Answer 7

-log[H+]

Question 8

How do lungs affect pH?

Answer 8

Can remove/ retain CO2

Question 9

How do kidneys affect pH?

Answer 9

Can excrete more or less H+

Can make more/ less HCO3-

Question 10

What is the equilibrium equation of acids and bases in blood?

Answer 10

H2O + CO2 -> H2CO3 -> H+ + HCO3-

Question 11

What did the Pitt and Swan experiment demonstrate?

Answer 11

Blood has an ENORMOUS buffering capacity that can react almost IMMEDIATELY to imbalances

Question 12

2 sources of acid in the body

Answer 12

Respiratory: CO2 (Majority, has main effect on blood pH)
Metabolic: Pyruvic acid, Lactic acid, HCl

Question 13

Base excess

Answer 13

Amount of bicarbonate measured compared to amount of bicarbonate expected because of pCO2
How much excess alkaline is there?
Can be positive or negative

Question 14

Positive base excess

Answer 14

too much alkali

need to add acid

Question 15

Negative base excess

Answer 15

Not enough alkali

need to remove acid

Question 16

What acronym can be used to interpret an ABG and determine whether the cause is metabolic or respiratory?

Answer 16

ROME
Respiratory
Opposite
Metabolic
Equal

Question 17

What is meant by “respiratory opposite” in ROME?

Answer 17

If cause of acidosis/ alkalosis is respiratory, direction of pH is opposite to the direction of CO2
E.g. respiratory acidosis= low pH, high PaCO2

Question 18

What is meant by “metabolic equal” in ROME?

Answer 18

pH goes in same direction as bicarbonate

If gain lots of bicarbonate, mop up more H+ so pH increases

Question 19

Which gives a faster compensatory response, the lungs or the kidneys?

Answer 19

LUNGS

Question 20

What does an acidosis need to correct it?

Answer 20

An alkalosis

Question 21

What does an alkalosis need to correct it?

Answer 21

An acidosis

Question 22

How to interpret an ABG

Answer 22

Type of imbalance: Acidaemia/ Alkalaemia
Aetiology of imbalance: Respiratory/ Metabolic/ Mixed/ Normal
Any homeostatic compensation: Uncompensated/ Partial/ Fully compensated
Oxygenation: Hypoxaemia/ Normoxaemia/ Hyperoxaemia

Question 23

If the aetiology is respiratory, what compensatory mechanism is used?

Answer 23

Metabolic

Question 24

If the aetiology is metabolic, what compensatory mechanism is used?

Answer 24

Respiratory

Question 25

Hyperventilation

Answer 25

Causes respiratory alkalosis

Question 26

Diarrhoea

Answer 26

Causes metabolic acidosis

Question 27

Vomiting

Answer 27

Causes metabolic alkalosis

Losing HCl

Question 28

Hypoxia

Answer 28

Low O2

Question 29

pO2 ranges in hypoxia (kPa)

Answer 29

> 10: normal
8-10: mild hypoxaemia
6-8: moderate hypoxaemia
<6: severe hypoxaemia

Question 30

Type 1 respiratory failure

Answer 30

1 thing wrong (low O2)
Normally acute, sudden
E.g. Pulmonary embolism or foreign body causing VQ mismatch

Question 31

Type 2 respiratory failure

Answer 31

2 things wrong (low O2 and high CO2)
Chronic, long term,
e.g. COPD, alveoli not ventilated well enough, don’t get enough O2 and cant get rid of enough CO2 (causes chest to expand “barrel chest”)