Chem path 5 - Diabetes cases

Question 1

What is the diagnostic criteria for diabetes in an asymptomatic and symptomatic person?

Answer 1

Asymptomatic - 2 diabetes test results

Symptomatic - Symptoms + 1 diabetes test result

Question 2

What are the glucose thresholds for diabetes diagnosis? (Fasting, OGTT, random)

Answer 2

Fasting: >/=7.0mmol/l

Random/OGTT (75g glulcose given at time 0): >/=11.1

Question 3

What is the threshold for IGT?

Answer 3

7.8-11.1

Question 4

What is the threshold for impaired fasting glucose?

Answer 4

6.1-7.0

Question 5

What is the Hba1c cut off?

Answer 5

> 6.5%/>48mmol/mol

Question 6

Why are patients with DKA often unconscious?

Answer 6

Because the brain enzymes cannot function at a low pH which is caused by the metabolic acidosis

Question 7

What is the equation for osmolality?

Answer 7

2(Na+K) + U + G

Question 8

What are the units for osmolality?

Answer 8

mosmol/kg

Question 9

What is normal osmolality?

Answer 9

275-295 mOsmol/kg

Question 10

What is the normal osmolar gap?

Answer 10

<10mM

Question 11

How is osmolar gap calculated?

Answer 11

measured osmolality (frozen plasma) - calculated osmolality (not frozen)

Question 12

How do you measure the anion gap?

Answer 12

Na + K - Cl - Bicarb

Question 13

What is the normal anion gap?

Answer 13

18mM

Question 14

Which things could a high anion gap suggest?

Answer 14

Ketones, ethylene glycol poisoning (Anti freeze), lactate, methanol, ethanol, metformin

Question 15

• 19yo T1DM presents unconscious
• ABG blood test results:
o pH 7.65 pCO2 = 2.8kPa Bicarb = 24mM (normal) pO2 = 15kPa
o Respiratory alkalosis
o Na = 140 K = 4.0 Cl = 100 Glucose = 1.3mM

Calculate the anion gap

Answer 15

20 (144 - 124)

Question 16

What could the cause of this respiratory alkalosis be

Answer 16

Primary hyperventilation due to anxiety caused by hypoglycaemia

Question 17

What happens to the plasma proteins and calcium as pH increased?

Answer 17

The plasma proteins start to stick to the calcium so although plasma calcium will appear normal, there will be less free ionised calcium which will result in tetany (can make pts hyperventilate more)

Question 18

• 60yo man presents unconscious with a history of polyuria and polydipsia
• ABG test results:
o Na = 160 K = 6.0 U = 50 pH = 7.30 Glucose = 60
o Osmolality = 2(160+6) + 50 + 60 = 442mosm/kg (high osmolality – dehydrated)

What is this a diagnosis of?

Answer 18

Hyperosmolar hyperglycaemic state

Question 19

Why is this not DKA?

Answer 19

Because the pH is reasonable

Question 20

How do you treat someone with HHS?

Answer 20

You need to rehydrate them slowly to avoid risk of cerebral oedema. 0.9% NaCl (500ml-1,000ml)

Question 21

Why do you not give someone with HHS insulin immediately?

Answer 21

It will draw glucose in to cells and dehydrate them even more

Question 22

• 59yo T2DM on a good diet and metformin, presents unconscious, urine -ve for ketones
• ABG test results:
o Na = 140 K = 4.0 U = 4.0 pH = 7.10 Glucose = 4.0
o PCO2 = 1.3kPa Cl = 90 Bicarb = 4.0mM
o Metabolic acidosis

o Osmolality = 2(140+4) + 4 + 4 = 296
o Anion gap = 140 + 4 – 4 – 90 = 50

What could the cause of this presentation be?

Answer 22

Metformin overdose –> lactic acidosis (?suicide attempty)

Question 23

What is the cori cycle?

Answer 23

The metabolic pathway by which lactate is produced by anaerobic glycolysis in the muscles and moves to the liver to be converted to glucose, which then returns to the muscles and is metabolised to lactate

Question 24

How does metformin interfere with the cori cycle?

Answer 24

It prevents hepaitc gluconeogenesis so you get a backlog of lactic acid

Question 25

How is excess lactate normally cleared and why is this not always the case in diabetic patients?

Answer 25

Excess lactate is usually cleared by the kidneys but this is impaired in patients with renal failiure

Question 26

What blood gas picture do patients with COPD have”?

Answer 26

Chronic resp acidosis

Question 27

What does CO2 do the respiratory system?

Answer 27

It is a potent respiratory stimulant

Question 28

What are pink puffers?

Answer 28

Pink puffers: They are still sensitive to the increased CO2 and its respiratory stimulus so they are breathless. Eventually there will come a point where your brain will stop being responsive to CO2 –> the CO2 is no longer a potent driver to breathe

Question 29

What are features of blue bloaters?

Answer 29

Unresponsive to CO2 resp stimulus so NOT breathless but their CO2 will continue to rise

Question 30

What metabolic picture does aspirin overdose give you?

Answer 30

Respiratory alkalosis and metabolic acidosis

Question 31

What are some genetic associations of T1DM

Answer 31

HLA DR-3 and HLA DR-4

Question 32

What is a common SE of sulphonylureas?

Answer 32

Hypoglycaemia

Question 33

what is the speed of onset of HHS?

Answer 33

Over a few days

Question 34

What are the diagnostic features of HHS?

Answer 34

Ph >7.3, Osmolarity >320mosm, bM >30mmol/L (non-ketotic hyperglycaemia)