CHEMPATH: Diabetes cases Flashcards
Describe the diagram for acid-base.
What is the normal range for
- HCO3
- Cl-
- AG
Normal HCO3- = 23-30 mEq/L
Normal Cl- = 96-106 mEq/L
Normal AG = ≤20 mEq/L
What are the normal ranges for ?
- pH
- bicarb
- O2
- CO2
Why do we double Na and K?
anions = cations
So you just double the cations instead of adding cations and anions separately
What is the osmolality equation?
What is the anion gap equation?
What is the acid-base abnormality?
- pH 7.65
- pCO2 = 2.8kPa
- Bicarb = 24mM (normal)
- pO2 = 15kPa
Respiratory alkalosis
What happens with Ca when pH increases?
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)
What is the anion gap here?
- Na = 140
- K = 4.0
- Cl = 100
- Bicarb = 24mM (normal)
- Glucose = 1.3mM
Anion gap = Na + K - Cl - bicarb
Anion gap = 140 + 4.0 – 100 – 24 = 20mM (normal)
Could be anxiety caused by hypoglycaemia as the AG is normal, causing primary hyperventilation.
What is the osmolality here?
60yo man presents unconscious with a history of polyuria and polydipsia:
- Na = 160
- K = 6.0
- U = 50
- pH = 7.30
- Glucose = 60
Osmolality = 2(160+6) + 50 + 60 = 442mosm/kg (high osmolality – dehydrated)
What is the diagnosis in this patient?
60yo man presents unconscious with a history of polyuria and polydipsia:
- Na = 160
- K = 6.0
- U = 50
- pH = 7.30
- Glucose = 60
- This is hyperosmolar hyperglycaemic state (HHS) from T2DM uncontrolled –> unconscious as brain is very dehydrated
- Not DKA because the pH is reasonable
What is the management of HHS?
- Treatment:
- 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)
What is the osmolality?
- 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
- 296 mosm/kg
What is the anion gap? What is the acid-base abnormality?
- 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
Anion gap = 140 + 4 - 90 - 4 = 50
59yo T2DM on a good diet and metformin, presents unconscious, urine -ve for ketones. If the anion gap is 50, what could be the cause?
Metabolic acidosis here is caused by lactate due to metformin excess, due to renal impairment.
NB: in sepsis, lactate also causes metabolic acidosis.
What is the name for the metabolic pathway by which lactate is produced by anaerobic glycolysis in the muscles?
Cori cycle
Describe the Cori cycle.
- 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
What is the definition of type 2 diabetes?
Fasting PLASMA glucose >7 mM (and so don’t need OGTT)
OR
OGTT (after 75g glucose) plasma glucose >11.1 mM at 2 hours
HbA1c >48mmol/mol (>6.5%) = T2DM
What is impaired glucose tolerance?
Random or OGTT at 2hr is 7.8-11.1 mM
HbA1c 42mmol/mol
What is impaired fasting glucose?
6.1-7.0 mmol/L at fasting
Describe this diagram.
- Normal (white)
- Acute respiratory acidosis = the pH will rise rapidly and may be because you have stopped breathing entirely
- COPD = chronic respiratory acidosis have renal metabolic compensation by retaining HCO3-. Lungs slowly fail and pCO2 rises (green). In COPD, your lungs will slowly fail and your pCO2 will drift upwards à become very breathless because CO2 is a potent respiratory stimulus but in pink puffers they eventually stop responding to the CO2 respiratory stumulus and become blue bloaters with rising CO2 but not breathlessness.
What is the normal osmolality range?
275-295
- What is the acid base abnormality? What is the osmolality? What is the anion gap? What is the cause?
- 16yo, unconscious, acutely unwell a few days; vomiting and breathless
- ABG results:
- pH 6.85
- pCO2 2.3kPa (4-5)
- PO2 = 15kPa
- Na: 145, K: 5.0, U: 10, glucose: 25
Metabolic acidosis
Osmolality = 2(145+5) + 10 + 25 = 335
AG = 145 + 5.0 – 96 – 4.0 = 50mM (high) = ?extra KETONES
What can cause a deranged anion gap?
- High anion gap = methanol, ethanol, lactate, ketones (ketone dip negative), metformin
