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Year 5 Chemical Pathology > 5: Diabetes Cases > Flashcards

5: Diabetes Cases Flashcards

1
Q

How do we diagnose diabetes

A

Symptoms + 1 diabetes test result

No symptoms + 2 diabetes test results

OGTT = 75g of glucose, measure glucose in 2 hours

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2
Q

What is the ABG result

  • pH 6.85 pCO2 2.3kPa (4-5)
  • PO2 = 15kPa
A

METABOLIC ACIDOSIS = unconscious, brain enzymes cannot function at low pH

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3
Q

How do we measure osmolality? (275 - 295 mOsmol/kg)

A

osmolality = 2(Na+K) + U + G

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4
Q

osmolality when:

  • Na: 145, K: 5.0, U: 10, glucose: 25
A
  • Osmolality = 2(145+5) + 10 + 25 = 335
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5
Q

What is the osmolar gap?

A

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
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6
Q

What is the anion gap?

A

Na + K - CI - bicarb

Normal AG = <20 mEq/L

ANYTHING HIGHER → extra KETONES are to blame or ETHYLENE GLYCOL POISONING

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7
Q

ranges

A
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8
Q

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
A

Respiratory alkalosis = anxiety caused by hypoglycaemia (as AG is normal) → primary hyperventilation

Anion gap = 140 + 4 - 100 - 24 = 20mM (normal)

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9
Q

How is alkalosis, decreased calcium, tetany and hyperventilation related?

A

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)

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10
Q

60 y/o man unconscious with hx of polyuria and polydipsia

  • Na = 160 K = 6.0 U = 50 pH = 7.30 Glucose = 60
A

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

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11
Q

How do we treat HHS?

A
  • 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)
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12
Q

HHS summary

A
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13
Q

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
A

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)

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14
Q

The Cori Cycle (explains lactic acidosis)

A

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

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15
Q

Definition of T2DM

A

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
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16
Q

COPD and chronic respiratory acidosis

A
  • 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-
17
Q

T1DM vs t2DM

A
18
Q

Mx of T1DM

A

Conservative (lifestyle advice, alcohol, diet)

Medical:

  • Insulin – basal bolus, insulin pump
  • Metformin (BMI >25)

Surgical → SPK (Single pancreas kidney transplant)

19
Q

Mx of T2DM

A
20
Q

Mx of DKA

A
21
Q

Mx of DKA

A

Year 5 Chemical Pathology (18 decks)

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