Acid Base Balance

Question 1

Normal range for pH?

Answer 1

7.37 - 7.43

Question 2

Normal range for pCO₂?

Answer 2

36 - 44 mmHg

Question 3

Normal range for [HCO₃⁻]?

Answer 3

22 - 26 mmol/L

Question 4

Acute causes of respiratory acidosis?

Answer 4

Obstruction

Drugs depressing medullary respiratory centres e.g. barbiturates and opiates

Question 5

Chronic causes of respiratory acidosis?

Answer 5

Lung diseases (bronchitis/emphysema/asthma)

Question 6

Acute causes of respiratory alkalosis?

Answer 6

Voluntary hyperventilation
Aspirin
First ascent to altitude

Question 7

Chronic causes of respiratory alkalosis?

Answer 7

Long term residence at altitude

Decreased pO₂ to less than 60 mmHg stimulates peripheral chemoreceptors to increase ventilation

Question 8

Causes of metabolic acidosis?

Answer 8

Increased H⁺ production (e.g. ketoacidosis, lactic acidosis)
Failure to excrete normal dietary H⁺ (e.g. renal failure)
Loss of HCO₃⁻ (e.g. diarrhoea: failure to reabsorb intestinal HCO₃⁻)

Question 9

Causes of metabolic alkalosis?

Answer 9

Increased H⁺ ion loss (vomiting)
Increased renal loss of H⁺ (ALDR excess)
Excess administration of HCO₃⁻ (especially in renal impairment)
Massive blood transfusion, bank blood contains citrate (would need about 8 units though)

Question 10

What could be the cause of raised pCO₂ and HCO₃⁻?

Answer 10

Respiratory acidosis if the pH has decreased

Metabolic alkalosis if the pH is also raised

Question 11

What could be the cause of decreased pCO₂ and HCO₃⁻?

Answer 11

Respiratory alkalosis if the pH is raised

Metabolic acidosis if the pH has also decreased