ChemPath: Diabetes CPC

Question 1

Define diabetes based on:

1. Fasting plasma glucose
2. 2-hour oral glucose tolerance test
3. HbA1c

Answer 1

1. Fasting plasma glucose
   
   • > 7 mmol/L
2. 2-hour oral glucose tolerance test
   
   • > 11.1 mmol/L
3. HbA1c
   
   • More than 48 mmol/mo (6.5%)

Question 2

List some causes of metabolic alkalosis.

Answer 2

• H+ loss (e.g. vomiting)
• Hypokalaemia
• Ingestion of bicarbonate

Question 3

Why is respiratory compensation for alkalosis usually quite poor?

Answer 3

Metabolic alkalosis inhibits ventilation but ventilation must remain sufficient to maintain good oxygen levels

Question 4

State the equation for plasma osmolality.

Answer 4

Osmolality = 2(Na + K) + Urea + Glucose

charged + unchargd molecules

Question 5

How do you work out the anion gap?

Answer 5

Need to know chloride to calculate anion gap
(ketones + lactate raise anion gap)

Question 6

List some causes of hypokalaemic alkalosis.

Answer 6

• Intestinal loss (diarrhoea, vomiting, fistula)
• Renal loss (minerlocorticoid excess, diuretics, renal tubular disease, osmotic diuresis, increased sodium delivery to distal nephron)
• Redistribution (insulin, alkalosis, beta-agonists)
• Rare (renal tubular acidosis type 1 and 2, hypomagnesaemia)

Question 7

Outline the relationship between hypokalaemia and alkalosis.

Answer 7

• Low K⁺ leads to a shift of H⁺ into cells
• This causes alkalosis
• Similarly, low H⁺ will result in a shift of K⁺ into cells

different mechanism depending on which came first

Question 8

How can ectopic ACTH be distinguished from other causes of Cushing’s syndrome?

Answer 8

Ectopic ACTH cannot be suppressed by high-dose dexamethasone suppression test

Question 9

Which cause of Cushing’s syndrome is most commonly associated with hypokalaemia?

Answer 9

Ectopic ACTH

very high ACTH = Very high cortsiol = binds to aldosterone receptors

Question 10

Why might a patient with Cushing’s syndrome be hypotensive?

Answer 10

Diuresis can lead to dehydration and hypotension

Question 11

What is the only definitive way of distinguishing acute renal failure from chronic renal failure?

Answer 11

Renal biopsy

Question 12

How might ATN due to dehydration be treated?

Answer 12

3 weeks of dialysis

Question 13

What treatment might diabetic glomerular kidney disease require?

Answer 13

This can result in end-stage renal failure requiring dialysis.

Question 14

What does slow-onset upper motor neurone lesions in a cancer patient suggest?

Answer 14

Brain metastases