Acid base

Question 1

Normal bicarbonate

Answer 1

22-30

Question 2

Normal pCO2

Answer 2

4.7-6

Question 3

Normal pH

Answer 3

7.35-7.45

Question 4

Causes of metabolic acidosis

Answer 4

Increased acid in system (elevated anion gap)
Reduced bicarbonate loss (intestinal fistula)
Reduced acid excretion (renal tubular acidosis)

Question 5

What is the anion gap?

Answer 5

(Na + K) - (Cl + HCO3)
Should be 14-18 - if it isn’t another anion is present
Used in metabolic acidosis - will be elevated in certain conditions

Question 6

What are the steps to determining cause of MA?

Answer 6

1. Calculate anion gap - elevated with ketones (DKA, starvation), uraemia (CKD), lactate (infection), toxins (ethylene glycol, salicylates, methanol)
2. Calculate osmolar gap - will be elevated with toxins

Question 7

How is osmolar gap calculated?

Answer 7

Osmolality - Osmolarity

Question 8

Metabolic acidosis

Raised anion gap

Answer 8

Ketones (DKA, starvation)
Uraemia (CKD)
Lactate (infection)
Toxins (ethylene glycol, salicylates, methanol)

Question 9

Metabolic acidosis
Raised anion gap
Raised osmolar gap

Answer 9

Toxins (ethylene glycol,, salicylates, methanol)

Question 10

Causes of metabolic alkalosis

Answer 10

Increased acid excretion (e.g. pyloric stenosis)
Increased bicarbonate intake
Hypokalaemia

Question 11

Causes of respiratory acidosis

Answer 11

Lung injury (COPD, pneumonia)
Decreased ventilation (morphine OD)

Question 12

Causes of respiratory alkalosis

Answer 12

Mechanical ventilation (e.g. CPAP)
Anxiety / panic attack
Stimulants of respiratory centre