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.
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
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.
