Chem path 5 - Diabetes cases Flashcards
What is the diagnostic criteria for diabetes in an asymptomatic and symptomatic person?
Asymptomatic - 2 diabetes test results
Symptomatic - Symptoms + 1 diabetes test result
What are the glucose thresholds for diabetes diagnosis? (Fasting, OGTT, random)
Fasting: >/=7.0mmol/l
Random/OGTT (75g glulcose given at time 0): >/=11.1
What is the threshold for IGT?
7.8-11.1
What is the threshold for impaired fasting glucose?
6.1-7.0
What is the Hba1c cut off?
> 6.5%/>48mmol/mol
Why are patients with DKA often unconscious?
Because the brain enzymes cannot function at a low pH which is caused by the metabolic acidosis
What is the equation for osmolality?
2(Na+K) + U + G
What are the units for osmolality?
mosmol/kg
What is normal osmolality?
275-295 mOsmol/kg
What is the normal osmolar gap?
<10mM
How is osmolar gap calculated?
measured osmolality (frozen plasma) - calculated osmolality (not frozen)
How do you measure the anion gap?
Na + K - Cl - Bicarb
What is the normal anion gap?
18mM
Which things could a high anion gap suggest?
Ketones, ethylene glycol poisoning (Anti freeze), lactate, methanol, ethanol, metformin
• 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
20 (144 - 124)
What could the cause of this respiratory alkalosis be
Primary hyperventilation due to anxiety caused by hypoglycaemia
What happens to the plasma proteins and calcium as pH increased?
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)
• 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?
Hyperosmolar hyperglycaemic state
Why is this not DKA?
Because the pH is reasonable
How do you treat someone with HHS?
You need to rehydrate them slowly to avoid risk of cerebral oedema. 0.9% NaCl (500ml-1,000ml)
Why do you not give someone with HHS insulin immediately?
It will draw glucose in to cells and dehydrate them even more
• 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?
Metformin overdose –> lactic acidosis (?suicide attempty)
What is the cori cycle?
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
How does metformin interfere with the cori cycle?
It prevents hepaitc gluconeogenesis so you get a backlog of lactic acid
