Venous blood Gases

Question 1

what can cause metabolic alkalosis?

Answer 1

GI losses

• diarrhoea
• vomiting

renal losses

• primary hyperaldosteronism
• tubular transporter defects
• diuretics

intracellular shift
- hypokalaemia

Question 2

what does a high anion gap indicate?

Answer 2

acidosis due to increased acid

due to
- lactic acidosis = anaerobic exercise, sepsis, organ ischaemia

• ketoacidosis = diabetic, alcohol abuse, starvation
• toxins e.g aspirin, methanol, salicylate
• renal failure

Question 3

what does a normal ion gap indicate?

Answer 3

acidosis due to a reduced alkali

• GI losses of HCO3 e.g vomiting and diarrhoea
• renal losses of HCO e.g renal tubular acidosis, Addison’s (mineralocorticoid deficiency)
• toxins e.g ammonium chloride

Question 4

how is anion gap calculated?

Answer 4

Sodium concentration - (chloride + bicarbonate)