Chempath 14: Diabetes Cases

Question 1

What is the formula for working out osmolarity ?

Answer 1

Osmolarity= 2(Na + k) + urea + glucose

Question 2

How do you calculate anion gap ?

Answer 2

Anion gap = (Na + K) - (Cl + HC03)

Anion gap calculates how many ‘other” anions there are. E.g PO4
Normally in the body there are some because we are not electrically charged so all anions + all cations should balance.

Question 3

Which metabolic disturbance is caused by metformin overdose ?

Answer 3

Lactic acidosis

Metformin inhibits gluconeogenesis in the liver by blocking a step in the Cori cycle where lactate is converted back to glucose. This causes excess lactate

Question 4

Name 2 tests that can be used to diagnose Diabetes or Impaired glucose tolerance ?

Answer 4

Fasting plasma glucose: >7mM = Diabeted
Oral glucose tolerance test: >11.1mM at 2 hours = diabetes
oral glucose tolerance test 7.8-11.1mM at 2 hours = Impaired glucose tolerance

Question 5

What result defines impaired glucose tolerance ?

Answer 5

Oral glucose tolerance test >7.8 but < 11.1 mM at 2 hours

Question 6

What result defines impaired fasting glucose ?

Answer 6

Fasting glucose >6.1 but <7.1

Question 7

What is HHS ?

Answer 7

• Hyperosmolar hyperglycaemic state
• More common in Type 2 DM
• No ketones (because still have insulin)
• very high plasma glucose >30mM
• High osmolarity >320mOsm
• Develops over days

Question 8

What is DKA?

Answer 8

• Diabetic ketoacidosis
• Ketones in the blood and urine
• more common in type 1 DM
• caused by very low insulin levels
• Hyperglycaemic >11 mM