Diabetes CPC

Question 1

In someone with HHS, what is the CAUSE of coma?

Answer 1

it’s hypotension- as the brain is not being perfused

Question 2

pH: 7.65 alkalosis

PCO2: 6.1kPa (N: 4.7-6.0) high

PO2= 15kPa

What is the metabolic abnormality?

Answer 2

metabolic alkalosis

Question 3

causes of metabolic alkalosis

Answer 3

1. vomiting: H+ loss
2. hypokalaemia-Conn’s syndrome/refeeding syndrome
3. ingestion of bicarbonate

Question 4

what is compensation?

Answer 4

making the pH better but co2 worse

Question 5

calculation of osmoality

Answer 5

2(Na+K) + urea + glucose

i.e. cations + anions + uncharged molecules

Question 6

formula for anion gap

Answer 6

cations - anions

i.e.

Na + K - Cl - bicarb

Question 7

what electrolyte abnormality is associated with alkalosis?

Answer 7

HYPOKALAEMIA!!!

hypokalaemia causes increase in HCO3-

Question 8

causes of longstanding hypokalaemia

Answer 8

thiazide diuretics

Question 9

explain the link between hypokalaemia and alkalosis

Answer 9

both can cause each other

Question 10

if you did high dose dx suppression test (nB not done anymore but hypothetically) which cause of cushing’s syndrome would fail to suppress vs ssuppress?

Answer 10

1. cushing’s disease: some suppression with high dose dex
2. ectopic acth: no suppression

disease causes suppression

Question 11

how does cushing’s syndrome cause hypokalaemia?

Answer 11

excess cortisol starts to behave like mineralocorticoid

therefore hypernatraemia and hypokalaemia

• Because VERY high levels of cortisol bind to the aldosterone receptor (MR)
• GCs are promiscuous for MRs, so it causes a longstanding hypokalaemic effect
• Ectopic ACTH causes hypokalaemia more often than other causes of Cushing’s

Question 12

what is the only way to distinguish between acuute renal failure and chronic renal issues?

which is a “better” outcome?

Answer 12

renal biopsy

(acute- dehydration, chronic- diabetes)

ATN is a better outcome because this is reversible with dialysis

(diabetic chronic kidney disease is treated with LIFE LONG DIALYSIS- chronic and irreversible​

Question 13

***conclusion:

woman had lung cancer producing ectopic acth –> cushing’s syndrome with longstanding hypolkalaemia

a) HHS (acute presentation) + ATN –> treated with fluids–>resolved
b) diabetes–>MI–>treated
c) eventually the lung cancer metastasised to the brain –> focal neurological signs
d) eventually died from acute coronary ischaemia

Question 14

diff between death from acute coronary ischaemia vs arrythmia

Answer 14

sometimes before the heart muscle has time to die, the patient can get VF and die due to arrythmia

in this case you wouldn’t see any necrosis of tissue in the post-mortem

*if you saw death of tissue+scarring –> cause of death is ischaemia not arrythmia*

Question 15

How can anion gap assist in diagnosis of DKA?

Answer 15

Ketones are anions
Therefore, in DKA anion gap will be large

Question 16

How can pituitary-dependent Cushing’s and ectopic ACTH be distinguished?

Answer 16

Pituitary petrosal sinus sampling

Question 17

What metabolic imbalance is caused by metformin?

Answer 17

Lactic acidosis

overdose of metformin (or metofrmin in those with kidney failure) will impair heptatic gluconeogenesis so lactate accumualtes wihtout being coverted to glucose >> lactic acidosis

(These are anions so will cause high anion gap, but urine will be negative for ketones)

Question 18

How can hypoglycaemia lead to a respiratory alkalosis?

Answer 18

Can cause significant anxiety –> hyperventilation

Question 19

What are the 3 biochemical definitions of diabetes?

Answer 19

Fasting PLASMA glucose >7.0mM (nb. this value does not apply to fingerprick whole blood test)

HbA1c > 6.5% (equivalent >48mmol/mol)

2 hour plasma glucose in Glucose Tolerance Test of >11.1mM

Question 20

What HbA1c values count as ‘impaired glucose tolerance’?

Answer 20

42-48mmol/mol

Question 21

how does Hypokalaemia Leads to Alkalosis (Cells)

Answer 21

• The K+ swaps for Na+
• This results in a local hypokalaemia which leads to a shift of H+ into the cell
• This leads to an alkalosis and low K+
• In the kidneys, H+ ions are lost into the urine
• K+ is taken up into the cell

Question 22

causes of Hypokalaemia/ Hypokalaemic Alkalosis

Answer 22

1. decreased intake (Rare)
2. intestinal loss - diarrhoea, vomiting, fistulae
3. renal loss-

• Hyperaldosteronism, excess cortisol
• Increased sodium delivery into the distal nephron
• Osmotic diuresis

4. redistribution into cells
   - insulin - drives potassium into cells so plasma K+ is low

Insulin, b-agonists, alkalosis

RARE CASES: Renal tubular acidosis type 1 + 2, hypomagnesaemia

Question 23

NOTE: Treatment for HyperK+

Answer 23

• Insulin
• Salbutamol
• Can use HCO3 too

Question 24

What are the Possible Causes of cushing’s

Answer 24

• Pituitary
• Ectopic ACTH
• Adrenal tumour

Question 25

• ACTH: 250 = very high
• Cortisol: 3210nM = very high
• Dexamethasone FAILED to suppress
• Low dose dex: Cortisol- 3100nM
• High dose dex: Cortisol – 2990nM (totally failed to suppress)

what is the diagnosis

Answer 25

ectopic release of ACTH

if it was an adrenal source, the ACTH would be low. Pituitary Cushing’s may cause a suppression on high dose dexamethasone test.

Note high dose not used in practice anymore

Question 26

causes of ectopic ACTH + what tests should be done

Answer 26

• Lung cancer- small cell lung cancer
• Other cancers

Respiratory examination

Question 27

IV K+ can cause what problem

Answer 27

IV K+ can cause asystole so it needs to be given very slowly