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

Formula to calculate the anion gap

Answer 5

Na+K-Cl-bicarb

Question 6

What would the anion gap be in DKA?

Answer 6

high anion gap as ketones are anions

Question 7

List some causes of hypokalaemic alkalosis.

Answer 7

• 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 8

Outline the relationship between hypokalaemia and alkalosis.

Answer 8

• 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 9

Causes of hypokalaemia

Answer 9

GI loss:

diarrhoea, vomiting

Renal loss:

hyperaldosteronism, excess cortisol

increased sodium delivery to distal nephron

osmotic diuresis

Redistribution into cells:

insulin, beta-agonists, alkalosis

Question 10

Causes of excess cortisol/ Cushing’s

Answer 10

Pituitary: Cushing’s disease

ectopic ACTH

adrenal tumour

Question 11

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

Answer 11

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

Question 12

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

Answer 12

Ectopic ACTH

Question 13

Causes of ectopic ACTH

Answer 13

lung cancer

benign tumours

Question 14

What do these examination results suggest?

Reduced expansion on R side

Percussion dull on R side

Vocal resonance increased on R side

Answer 14

Collapse and consolidation

Question 15

Why does ectopic ACTH lead to hypokalaemia

Answer 15

cortisol binds to MR receptors

Question 16

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

Answer 16

Diuresis can lead to dehydration and hypotension

Question 17

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

Answer 17

Renal biopsy

Question 18

How might ATN due to dehydration be treated?

Answer 18

3 weeks of dialysis

Question 19

What treatment might diabetic glomerular kidney disease require?

Answer 19

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

Question 20

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

Answer 20

Brain metastases

Question 21

Causes of excess cortisol/ Cushing’s

Answer 21

Pituitary: Cushing’s disease

ectopic ACTH

adrenal tumour