27. Acidosis/Alkalosis

Question 1

What are 3 methods of maintaining blood pH?

Answer 1

Chemical buffering
Renal compensation
Respiratory compensation

Question 2

What chemical buffers are used in the ECF?

Answer 2

Bicarbonate
Inorganic phosphate
Plasma proteins

Question 3

What buffering reaction does inorganic phosphate undergo?

Answer 3

H+ + HPO4^2- = H2PO4-

Question 4

What chemical buffers are used in the ICF?

Answer 4

Cell proteins
Organic phosphate (RBCs)
Bicarbonate

Question 5

What chemical buffers are used in bone?

Answer 5

Mineral phosphates

Mineral carbonates

Question 6

What is the optimal conc of H+?

Answer 6

40 mmol

Question 7

What is the optimal partial pressure of CO2?

Answer 7

40

Question 8

What is the optimal conc of HCO3-?

Answer 8

24

Question 9

What is the pK of HCO3-?

Answer 9

6.1

Question 10

What is the definition of acidosis?

Answer 10

pH<7.35

[H+]> 45

Question 11

What is respiratory acidosis?

Answer 11

Lungs are not blowing off CO2 as quickly as it’s being produced
Increase in pCO2

Question 12

What are the causes of respiratory acidosis?

Answer 12

Depression of respiratory centre
Alveolar hypoventilation
Lung damage
Reduced CO2 diffusion

Question 13

What is the body’s response to respiratory acidosis?

Answer 13

Increased pCO2 in renal tubular cells
Increase H+ secretion
Increase synthesis of HCO3-
Increase rate of HCO3- reabsorption

Question 14

What is metabolic acidosis?

Answer 14

Gain of acid or loss of HCO3-

Characterised by low HCO3- and high anion gap

Question 15

What are the causes of metabolic acidosis?

Answer 15

Increased ketone bodies in diabetes
Ingestion of acidifying agents
Lactic acidosis
Severe diarrhoea
Renal failure

Question 16

What is the body’s response to metabolic acidosis?

Answer 16

Increase rate of breathing

Decrease pCO2 levels below normal

Question 17

What are the consequences of acidosis?

Answer 17

Change in nerve and muscle excitability (more K+ is reabsorbed)
CNS depression (disorientation, coma)
Osteomalacia (bone releases buffers)

Question 18

What is alkalosis?

Answer 18

pH>7.45

[H+]<35

Question 19

What is respiratory alkalosis?

Answer 19

Too much CO2 lost

Decrease in HCO3- and H+

Question 20

What are the causes of respiratory alkalosis?

Answer 20

Alveolar hyperventilation
Voluntary effort
Direct stimulation of medullary respiratory centre
Hypoxia due to anaemia or altitude
Certain NTs and hormones

Question 21

What is the body’s response to respiratory alkalosis?

Answer 21

Decreased pCO2 in alveolar cells

1. Decrease H+ secretion and HCO3- reabsorption
2. Decrease rate of HCO3- synthesis

Question 22

What is metabolic alkalosis?

Answer 22

Gain of a strong base
Loss of acid
Increased HCO3-

Question 23

What are the causes of metabolic alkalosis?

Answer 23

Antacids
Increased renal H+ loss (hyperaldosteronism, hypokalaemia)
Vomiting

Question 24

What is the body’s response to metabolic alkalosis?

Answer 24

Decrease breathing rate

Question 25

What are the consequences of alkalosis?

Answer 25

Hyperexcitability of the nervous system

• Tingling sensations
• Muscle spasm
• Irritability and confusion
• Hypocalcaemic tetany
• Impairment of respiratory muscles
• Death

Question 26

How is the anion gap calculated?

Answer 26

[Na+]-([Cl-]+[HCO3-])

Question 27

What is a healthy anion gap?

Answer 27

8-14mEq/L

Question 28

Why is the anion gap increased in metabolic acidosis?

Answer 28

Decrease of [HCO3-] and increased anions associated with a new acid eg. lactic acid