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H + HCO3 = CO2 + H2O
20
40
60
80
100
120
0 1 2 3 4 5 6 7 8 9
respiratory acidosis
respiratory alkalosis
Metabolic acidosis
Metabolic alkalosis
+ -
pCO2
pH [H+]6.92
7.0
7.1
7.22
7.407.527.707.80
Draw this on your IPAD
What is the acid/base abnormality?
A. Respiratory acidosisB. Metabolic acidosisC. Respiratory alkalosisD. Metabolic alkalosis
pH 6.85PCO2 = 2.3 kPa (N 4-5)PO2 = 15 kPa
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:
H + HCO3 = CO2 + H2O
20
40
60
80
100
120
0 1 2 3 4 5 6 7 8 9
respiratory acidosis
respiratory alkalosis
Metabolic acidosis
Metabolic alkalosis
+ -
pCO2
pH [H+]6.92
7.0
7.1
7.22
7.407.527.707.80
Type in your CID now
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 + anions + urea + glucose
•(Na, K) (Cl, HCO3)
•Since cations = anions, this can be reduced to:•Osmolality = 2(Na+K) + U + G
Also PO4, SO4, etc
Case 1: osmolality : derivation*
•Na: 145, K: 5.0, U 10, pH 6.85, Glucose 25.
•Osmolality = charged molecules + uncharged =cations + anions + urea + glucose
•(Na, K) (Cl, HCO3)
•Since cations = anions, this can be reduced to:•Osmolality = 2(Na+K) + U + G•What is the osmolality?
Also PO4, SO4, etc
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?
A. Respiratory acidosisB. Metabolic acidosisC. Respiratory alkalosisD. Metabolic alkalosis
pH 7.65PCO2 = 2.8 kPaBicarb = 24 mM (normal)PO2 = 15 kPa
H + HCO3 = CO2 + H2O
20
40
60
80
100
120
0 1 2 3 4 5 6 7 8 9
respiratory acidosis
respiratory alkalosis
Metabolic acidosis
Metabolic alkalosis
+ -
pCO2
pH [H+]6.92
7.0
7.1
7.22
7.407.527.707.80
Primary hyperventilation
Slows down spontaneously
Further results:
•Na = 140, K=4.0, bicarb=24, Cl=100•Glucose 1.3 mM
•What is the anion gap?
•What is the diagnosis ?
Further results:
•Na = 140, K=4.0, bicarb=24, Cl=100•Glucose 1.3 mM
•What is the anion gap? (normal)
•What is the diagnosis ?
Further results:
•Na = 140, K=4.0, bicarb=24, Cl=100•Glucose 1.3 mM
•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 : mosm/kg
•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 : 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?
A. Respiratory acidosisB. Metabolic acidosisC. Respiratory alkalosisD. Metabolic alkalosis
pH 7.10PCO2 = 1.3 kPa (N 4-5)PO2 = 15 kPa
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)
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).