5: Diabetes Cases Flashcards
How do we diagnose diabetes
Symptoms + 1 diabetes test result
No symptoms + 2 diabetes test results
OGTT = 75g of glucose, measure glucose in 2 hours
What is the ABG result
- pH 6.85 pCO2 2.3kPa (4-5)
- PO2 = 15kPa
METABOLIC ACIDOSIS = unconscious, brain enzymes cannot function at low pH
How do we measure osmolality? (275 - 295 mOsmol/kg)
osmolality = 2(Na+K) + U + G
osmolality when:
- Na: 145, K: 5.0, U: 10, glucose: 25
- Osmolality = 2(145+5) + 10 + 25 = 335
What is the osmolar gap?
measured osmolarity - calculated osmolarity
- Measured = frozen plasma
- calculated = not frozen
Normal result: <10 mm
- >10mM = other unaccounted ions
- If ions are charged (i.e. anion gap is large), ketones might be to blame
What is the anion gap?
Na + K - CI - bicarb
Normal AG = <20 mEq/L
ANYTHING HIGHER → extra KETONES are to blame or ETHYLENE GLYCOL POISONING
ranges
19 y/o T1DM presents unconscious, ABG is
- pH 7.65 pCO2 = 2.8kPa Bicarb = 24mM (normal) pO2 = 15kPa
- Na = 140 K = 4.0 Cl = 100 Glucose = 1.3mM
Respiratory alkalosis = anxiety caused by hypoglycaemia (as AG is normal) → primary hyperventilation
Anion gap = 140 + 4 - 100 - 24 = 20mM (normal)
How is alkalosis, decreased calcium, tetany and hyperventilation related?
When pH increases, plasma proteins start to stick to calcium more than usual → plasma calcium will appear normal, however, there will be less free ionised calcium → fall in free ionised calcium will result in tetany (which can make patients hyperventilate more)
60 y/o man unconscious with hx of polyuria and polydipsia
- Na = 160 K = 6.0 U = 50 pH = 7.30 Glucose = 60
Osmolality = 2(160+6) + 50 + 60 = 442 mosm/kg (HIGH OSMOLALITY, dehydrated)
Hypersomolar hyperglycaemic state (HHS) from uncontrolled T2DM → unconscious as brain is very dehydrated
NOT DKA as pH is reasonable
How do we treat HHS?
- 0.9% saline (500-1,000mL/hour) slowly
- Lots of fluid quickly → cerebral oedema and death
- Do not give insulin immediately (as insulin will pull glucose into cells and dehydrate them even more)
HHS summary
59yo T2DM on a good diet and metformin, presents unconscious, urine -ve for ketones
ABG test results:
- Na = 140 K = 4.0 U = 4.0 pH = 7.10 Glucose = 4.0
- PCO2 = 1.3kPa Cl = 90 Bicarb = 4.0mM
Metabolic acidosis
osmolality = 2(140+4) + 4 + 4 = 296
Anion gap = 140 + 4 - 4 - 90 = 50 (HIGH ANION GAP = methanol, ethanol, lactate, ketone dip negative, metformin)
METFORMIN OVERDOSE → lactate/lactic acidosis (? suicide attempt)
The Cori Cycle (explains lactic acidosis)
The metabolic pathway by which lactate is produced by anaerobic glycolysis in the muscles
This moves to the liver to be converted to glucose, which returns to muscles and is metabolised to lactate
Metformin can cause lactic acidosis because it inhibits hepatic gluconeogenesis
Normally, excess lactate will be cleared by the kidneys, but in patients with renal failure, the kidneys cannot handle the excess lactic acid
Definition of T2DM
Fasting Blood Glucose > 7.0 mM
OGTT (75g glucose given at time 0)
- diabetes = plasma glycose >11.1 mM at 2 hours
- Impaired glucose tolerance = plasma glucose 7.8 - 11.1 mM at 2 hours
COPD and chronic respiratory acidosis
- In acute respiratory acidosis, the pH will rise rapidly and may be because you have stopped breathing entirely
More commonly, COPD, which leads to the development of chronic respiratory acidosis can cause this
- In COPD, your lungs will slowly fail and your pCO2 will drift upwards → become very breathless because CO2 is a potent respiratory stimulus
- Pink puffers are very breathless because they are still sensitive to this raised CO2 → eventually come a point when your brain has had enough of puffing and will stop being responsive to CO2 → the CO2 is no longer a potent driver to breathe
- This makes you a nice, calm blue bloater – you are not breathless, but your CO2 will continue to rise
- The kidneys will try to compensate by retaining HCO3-
T1DM vs t2DM
Mx of T1DM
Conservative (lifestyle advice, alcohol, diet)
Medical:
- Insulin – basal bolus, insulin pump
- Metformin (BMI >25)
Surgical → SPK (Single pancreas kidney transplant)
Mx of T2DM
Mx of DKA
Mx of DKA
