Diabetes
Clinical cases
CID please…
Chemical Pathology: Y5
Karim Meeran
+
H + HCO
3
= CO2 + H2O
pH [H+]
6.92 120
7.0
100
7.1
80
7.22
60
7.40
7.52
7.70
7.80
40
20
Metabolic acidosis
respiratory acidosis
Draw this on
your IPAD
Metabolic alkalosis
respiratory alkalosis
0
1
2
3
4
5
pCO2
6
7
8
9
Case 1:
•16 year old unconscious.
•Acutely unwell a few days.
•Vomiting
•Breathless.
Case 1: data
•pH 6.85
•PCO2 = 2.3 kPa (N 4-5)
•PO2 = 15 kPa
What is the acid/base
abnormality?
pH 6.85
PCO2 = 2.3 kPa (N 4-5)
PO2 = 15 kPa
A. Respiratory acidosis
B. Metabolic acidosis
C. Respiratory alkalosis
D. Metabolic alkalosis
What is the acid/base
abnormality?
•Low pH = acidosis
•ie: excess H+ ions
•HCO3- + H+ = CO2 + H20
•Low CO2 = low bicarbonate
What is the acid/base
abnormality?
•Draw the following graph, which will
always tell you the answer:
Type in your CID now
+
H + HCO
3
= CO2 + H2O
pH [H+]
6.92 120
7.0
100
7.1
80
7.22
60
7.40
7.52
7.70
7.80
40
20
Metabolic acidosis
respiratory acidosis
Metabolic alkalosis
respiratory alkalosis
0
1
2
3
4
5
pCO2
6
7
8
9
What is the acid/base
abnormality?
•Low pH = acidosis
•Low CO2 = low bicarbonate
•Metabolic acidosis
Case 1: more data.
•Na: 145,
K: 5.0, U 10, pH 6.85, Glucose 25.
•Why is he unconscious ?
•What is the osmolality ?
Case 1: more data.
•Na: 145,
K: 5.0, U 10, pH 6.85, Glucose 25.
•Why is he unconscious ? Because brain
enzymes cannot function at a very acid pH
•What is the osmolality ?
Case 1: osmolality : derivation*
•Na: 145, K: 5.0, U 10, pH 6.85, Glucose 25.
•Osmolality = charged molecules + uncharged
=cations
•(Na, K)
+
anions +
(Cl, HCO3)
Also PO4, SO4, etc
urea + glucose
•Since cations = anions, this can be reduced to:
•Osmolality = 2(Na+K) + U + G
Case 1: osmolality : derivation*
•Na: 145, K: 5.0, U 10, pH 6.85, Glucose 25.
•Osmolality = charged molecules + uncharged
=cations
•(Na, K)
+ anions +
(Cl, HCO3)
urea + glucose
Also PO4, SO4, etc
•Since cations = anions, this can be reduced to:
•Osmolality = 2(Na+K) + U + G
•What is the osmolality?
Case 1: osmolality
•Na: 145,
K: 5.0, U 10, Glucose 25.
Case 1: anion gap*
•Cations (Na/K) = Anions (Cl, Bicarb, others)
•“Others” known as “anion gap”.
•Anion gap = Na + K – Cl – bicarb
Case 1: anion gap*
•Cations (Na/K) = Anions (Cl, Bicarb, others)
•“Others” known as “anion gap”.
•Anion gap = Na + K – Cl – bicarb
Case 1: anion gap*
•Cations (Na/K) = Anions (Cl, Bicarb, others)
•“Others” known as “anion gap”.
•Anion gap = Na + K – Cl – bicarb
•Normal AG =140+4.0 – 102 – 24 = 18 mM
Case 1: anion gap*
•Anion gap = Na + K – Cl – bicarb
•Normal AG =140+4.0 – 102 – 24 = 18 mM
•In this patient:
Case 1: anion gap*
•Anion gap = Na + K – Cl – bicarb
•Normal AG =140+4.0 – 102 – 24 = 18 mM
•In this patient calculate the anion gap now:
•145 + 5.0 – 96 – 4.0
Case 1: anion gap*
•Anion gap = Na + K – Cl – bicarb
•Normal AG =140+4.0 – 102 – 24 = 18 mM
•In this patient:
•145 + 5.0 – 96 - 4
•=
(high)
•Suggests extra anions (Ketones)
Case 2:
•A 19 year old known to have type 1 diabetes
for several years presents unconscious.
•Results: pH 7.65
•PCO2 = 2.8 kPa
•Bicarb = 24 mM (normal)
•PO2 = 15 kPa
What is the acid-base abnormality ?
Case 2: What is the acid/base
abnormality?
pH 7.65
PCO2 = 2.8 kPa
Bicarb = 24 mM (normal)
PO2 = 15 kPa
A. Respiratory acidosis
B. Metabolic acidosis
C. Respiratory alkalosis
D. Metabolic alkalosis
What is the acid/base
abnormality?
•High pH = alkalosis
•Low CO2 = respiratory
+
H + HCO
3
= CO2 + H2O
pH [H+]
6.92 120
7.0
100
7.1
80
7.22
7.40
7.52
7.70
7.80
Metabolic acidosis
respiratory acidosis
Slows down
spontaneously
60
Primary
40 hyperventilation
20
Metabolic alkalosis
respiratory alkalosis
0
1
2
3
4
5
pCO2
6
7
8
9
What is the acid/base
abnormality?
•High pH = alkalosis
•Respiratory alkalosis
Further results:
•Na = 140, K=4.0,
•Glucose 1.3 mM
bicarb=24, Cl=100
•What is the anion gap?
•What is the diagnosis ?
Further results:
•Na = 140, K=4.0,
•Glucose 1.3 mM
bicarb=24, Cl=100
•What is the anion gap?
•What is the diagnosis ?
(normal)
Further results:
•Na = 140, K=4.0,
•Glucose 1.3 mM
bicarb=24, Cl=100
•What is the anion gap?
(normal)
•What is the diagnosis ? Anxiety caused
by hypoglycaemia.
Case 3.
•60 year old man presents unconscious to
casualty, with a history of polyuria and
polydipsia. Investigations reveal:
•Na: 160,
K: 6.0, U 50, pH 7.30, Glucose 60.
•What is the osmolality ?
•Why is he unconscious ?
Case 3.
•60 year old man presents unconscious to
casualty, with a history of polyuria and
polydipsia. Investigations reveal:
•Na: 160,
K: 6.0, U 50, pH 7.30, Glucose 60.
•What is the osmolality :
•Why is he unconscious ?
mosm/kg
Case 3.
•60 year old man presents unconscious to
casualty, with a history of polyuria and
polydipsia. Investigations reveal:
•Na: 160,
K: 6.0, U 50, pH 7.30, Glucose 60.
•What is the osmolality :
mosm/kg
•Why is he unconscious : because the brain is
VERY dehydrated.
Case 4.
•59 year old man known to have type 2 diabetes,
on a good diet and metformin presents to
casualty unconscious:
•Urine is negative for ketones.
•Na: 140, K: 4.0, U 4.0, pH 7.10, Glucose 4.0
•PCO2=1.3 kPa. Cl = 90. Bicarb = 4.0 mM
•What is the osmolality :
•What is the anion gap:
•What is the acid-base disturbance
•Why is he unconscious :
Case 4.
•59 year old man known to have type 2 diabetes,
on a good diet and metformin presents to
casualty unconscious:
•Urine is negative for ketones.
•Na: 140, K: 4.0, U 4.0, pH 7.10, Glucose 4.0
•PCO2=1.3 kPa. Cl = 90. Bicarb = 4.0 mM
•What is the osmolality :
•What is the anion gap:
•What is the acid-base disturbance
•Why is he unconscious :
Case 4.
•What is the osmolality :
•Na: 140, K: 4.0, U 4.0, pH 7.10, Glucose 4.0
•PCO2=1.3 kPa. Cl = 90. Bicarb = 4.0 mM
•Osmo=2(Na+K) + U + G
Case 4.
•What is the anion gap:
•Na: 140, K: 4.0, U 4, pH 7.10, Glucose 4.0
•PCO2=1.3 kPa. Cl = 90. Bicarb = 4.0 mM
•Urine is negative for ketones.
•Anion Gap = (Na+K)
•
- bic - chloride
Case 4.
•What is the anion gap:
•Na: 140, K: 4.0, U 4, pH 7.10, Glucose 4.0
•PCO2=1.3 kPa. Cl = 90. Bicarb = 4.0 mM
•Urine is negative for ketones.
•Anion Gap = (Na+K)
•
- bic - chloride
Case 4.
•What is the anion gap:
•Na: 140, K: 4.0, U 4, pH 7.10, Glucose 4.0
•PCO2=1.3 kPa. Cl = 90. Bicarb = 4.0 mM
•Urine is negative for ketones.
•Anion Gap = (Na+K)
•
- bic - chloride
•ie: there are an excess of anions
What is the acid/base
abnormality?
pH 7.10
PCO2 = 1.3 kPa (N 4-5)
PO2 = 15 kPa
A. Respiratory acidosis
B. Metabolic acidosis
C. Respiratory alkalosis
D. Metabolic alkalosis
Case 4.
•What is the acid-base disturbance?
•pH 7.10 (acidosis)
•pCO2 = 1.3 kPa (very low)
Case 4.
•What is the acid-base disturbance?
•pH 7.10 (acidosis)
•pCO2 = 1.3 kPa (very low)
•Metabolic acidosis
Case 4.
•ie: there are an excess of anions
•Not ketones
•What else ?
•Methanol, ethanol, lactate
•Metformin in overdose can cause a
lactic acidosis
•Lactate = 10 mM (N<2.0)
The Cori cycle:
•Glucose (muscle)
Lactate
circulation
•Glucose
Inhibited by metformin
Lactate
liver
Case 4.
•Why is he unconscious?
•pH 7.10 (acidosis)
•The brain cannot function in such an
acidic pH.
Definition (type 2 diabetes)
•Fasting glucose > 7.0 mM
•Glucose tolerance test (75 grams glucose
given at time 0)
•Plasma glucose > 11.1 mM at 2 hours
•(2h value 7.8 – 11.1 = impaired glucose
tolerance).
Acid base graph: CID