Chem Path: Acid base handling

Question 1

What is the most important equation to remember in acid base handling?

Answer 1

H + HCO3 = H2CO3 = CO2 + H2O

Question 2

What is the main way of buffering H+ ions in the RBCs

Answer 2

CO2 that is absorbed by the RBCs are added to water

CO2 + H2O = H + HCO3

The H+ is added to Hb to make HHb

Question 3

What are the 3 reasons you can have high H+ and give examples of associated diseases

Answer 3

Increase H+ production - DKA or lactic acidosis
Decreased H+ excretion - Renal tubular acidosis
Decreased bicarbonate. - Intestinal fistula

Question 4

What is metabolic acidosis and how is it compensated for?

Answer 4

You have an excess of H+ ions, so it get rid of it you convert it:

H + HCO3 = H2CO3 = CO2 + H20

You then get rid of the CO2 by hyperventilating. So you CO2 falls and you pH goes back to normal (compensated)

Question 5

What happens in acute respiratory acidosis?

Answer 5

There is an increase in CO2. This means the equation shifts to the left and there is an increase in H+ ions. There may also be an increase in HCO3 ions.

Question 6

Why can there be an increase in CO2?

Answer 6

Decreased ventilation 
Poor lung function
Impaired gas exchange 
PE
Emphysema

Question 7

What happens in chronic respiratory acidosis

Answer 7

The metabolic compensation of respiratory acidosis is not as fast as respiratory compensation of metabolic acidosis. The kidneys takes longer to excrete H= ions and produced HCO3 to buffer H+. So in chronic respiratory acidosis, there is an increase in HCO3 to compensate for the increase in CO2, which is still elevated due to poor gas exchange

Question 8

What happens in metabolic alkalosis?

Answer 8

Reduction of H+ and/or increase in HCO3

Question 9

What can cause metabolic alkalosis

Answer 9

Hypokalaemia - You will have low H+ with this
Any reasons for H+ loss - D and V / Pyloric stenosis
Ingestion of bicarbonates

Question 10

How is metabolic alkalosis compensated?

Answer 10

Increase in CO2 so that the equation can be shifted left to increase H+ ions concentration. However not very effective as increase in CO2 can stimulate the respiratory drive to breathe off the excess CO2

Question 11

What happens in acute respiratory alkalosis?

Answer 11

There is low CO2, so you will compensate by driving the equation right. Therefore there will be s decrease in H+ ions and HCO3.

Question 12

Why will Co2 be low?

Answer 12

Hyperventilation - Panic attack
Artificial ventilation
Stimulation of respiratory centre by certain drugs

Question 13

What happens in chronic respiratory alkalosis?

Answer 13

Kidneys will try and reduce H+ excretion to compensate. H+ ions may recover but bicarbonate and CO2 remain low.

Question 14

How does aspirin overdose present

Answer 14

Metabolic acidosis and respiratory alkalosis

H+ ion may be normal

Aspirin can cause hyperventilation and H+ ion excretion in kidneys