Week 5 - Acid Base Balance

Question 1

What range must plasma pH be between?

Answer 1

7.35 - 7.45

Question 2

What is it called if plasma pH is greater than 7.45?

Answer 2

Alkalaemia

Question 3

What is it called if plasma pH is less than 7.35?

Answer 3

Acidaemia

Question 4

What are the effects of alkalaemia?

Answer 4

Lowers free calcium by causing Ca2+ ions to come out of solution which increases neuronal excitability, this leads to paraesthesia and tetany

Question 5

What are the affects of acidaemia?

Answer 5

Increases plasma potassium ion concentration which effects excitability especially in cardiac muscle which can cause arrhythmia
increases H+ concentrations which denatures proteins - effects muscles, muscle contractility, glycolysis, hepatic function

Question 6

How is plasma pH determined?

Answer 6

Ratio of bicarbonate concentration to pCO2

Question 7

What is the Henderson Hasslebalch equation to calculate pH?

Answer 7

CO2 + H2O H+ + HCO3-

Question 8

What is the Henderson Hasselbalch calculation?

Answer 8

pH = pK + Log([HCO3-]/(pCO2 X 0.23))

Question 9

What is pK?

Answer 9

Its a constant

6.1 at 37 degrees

Question 10

What is the pCO2 of plasma determined by?

Answer 10

Respiration - controlled by chemoreceptors, disturbed by respiratory disease

Question 11

What is the concentration of bicarbonate in plasma determined by?

Answer 11

Controlled by kidneys

Disturbed by metabolic and renal disease

Question 12

How does hypoventilation affect the acid base balance?

Answer 12

Causes hypercapnia (high pCO2)
This causes fall in plasma pH
And results in respiratory acidaemia

Question 13

How does hyperventilation affect acid base balance?

Answer 13

Causes hypocapnia (low pCO2)
This causes increase in plasma pH
Which results in respiratory acidaemia