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

Question 5

Equation of anion gap

Answer 5

Na + K - Cl - bicarb

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)

i.e. causes of hypokalaemia

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

Question 8

Complications of hypo and hyper kalaemia

Answer 8

Hypokalaemia - VF

Hyper - Asystole

Question 9

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

Answer 9

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

Question 10

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

Answer 10

Ectopic ACTH

Question 11

Causes of ectopic ACTH

Answer 11

Cancers

Question 12

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

Answer 12

Diuresis can lead to dehydration and hypotension

Question 13

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

Answer 13

Renal biopsy

Question 14

How might ATN due to dehydration be treated?

Answer 14

3 weeks of dialysis

Question 15

What treatment might diabetic glomerular kidney disease require?

Answer 15

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

Question 16

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

Answer 16

Brain metastases