Anion Gap + Metabolic acidosis

Question 1

how to calculate the anion gap

Answer 1

(sodium + potassium) - (bicarbonate + chloride)

Question 2

normal anion gap

Answer 2

8-14

Question 3

In patients with a metabolic acidosis, what could cause them to have a normal anion gap?

Answer 3

• GI bicarbonate loss: diarrhoea, ureterosigmoidostomy, fistula
• renal tubular acidosis
• drugs: e.g. acetazolamide
• Addison’s disease

Question 4

In patient’s with a metabolic acidosis, what could cause a raised anion gap?

Answer 4

• high lactate (shock, hypoxia)
• high ketones (DKA, alcohol)
• high urate (renal failure)
• acid poisoning (salicylates, methanol)
• 5-oxoproline: chronic paracetamol use

Question 5

Two main types of lactic acidosis which can go on to cause metabolic acidosis

Answer 5

Type A - sepsis, shock, hypoxia, burns
Type B - metformin