Acid-base regulation

Question 1

Blood gas abbreviations:
BE, meaning? depends on?
tHb
sO2
fO2Hb
fCOHb
FMetHb
FIO2
pAtm

Answer 1

Base Excess- amount of bicarbonate that is measured compared with amount of bicarbonate that is expected because of the PCO2, depends on HCO3- and PCO2
Total Hb
Saturation of O2
How much Hb is bound to O2
How much Hb is bound to CO
How much Hb is MetHb
Fraction of inspired O2 (how much O2 was in the air)
Atmospheric pressure

Question 2

Alkalaemia

Answer 2

Higher than normal pH of blood

Takes an alkalosis to create an alkalaemia

Question 3

Acidaemia

Answer 3

Lower than normal pH of blood

Question 4

Alkalosis

Answer 4

Circumstance that will decrease H+ and increase pH

Takes an alkalosis to create an alkalaemia

Question 5

Acidosis

Answer 5

Circumstance that will increase H+ and decrease pH

Question 6

pH equation

Answer 6

pH= -log10[H+]
[H+]= 10^-pH

Question 7

Types of acid (examples?)

What is produced in more concentration?

Answer 7

Respiratory acid, CO2

Metabolic acid, Pyruvic/ Lactic/ Stomach (everything else)

Respiratory acid> Metabolic acid (100x more)

Question 8

Sørensen equation
Henderson equation
Henderson-Hasselbalch equation

Answer 8

Sørensen - To calculate pH from proton concentration (vv.)
𝑝𝐻=−log_10 [𝐻+]

Henderson- To calculate dissociation constant (Ka)
𝐾=([𝐻+][𝐻𝐶𝑂3−])/([𝐶𝑂2][H2O])

Henderson-Hasselbalch- Combines above equations
𝑝𝐻=𝑝𝐾+ (𝑙𝑜𝑔_10 x [𝐻𝐶𝑂3-]/ [𝐶𝑂2])

Question 9

Interpreting a blood gas

Answer 9

Type of imbalance?
Acidosis/ Acidaemia/ Alkalosis/ Alkalaemia/ Normal?

Aetiology of imbalance?
Respiratory (acidosis or alkalaemia) / Metabolic (acidosis or alkalosis) / Mixed (respiratory and metabolic) / Normal
Is the PaCO2 normal, high or low? (assessing respiratory component)
Is the BE excess high or low? (assessing metabolic component)

Any homeostatic compensation?
Uncompensated / Partially compensated / Fully compensated

Oxygenation?
Hypoxaemia / Normoxaemia / Hyperoxaemia
Mild/moderate/severe

Question 10

Basic guidelines for PaO2

Answer 10

> 10 kPa is normal
8-10 kPa is mild hypoxaemia
6-8 is moderate hypoxaemia
<6 kPa is severe hypoxaemia

Question 11

Compensatory mechanisms for CO2
Rapid?
Slow?

Answer 11

Rapid= Changes in ventilation= alters pH

Slow= Changes in HCO3- and H+ retention/secretion in the kidneys alters pH

Question 12

Acidosis needs what to correct it?

Answer 12

Alkalosis

Question 13

Alkalosis needs what to correct it?

Answer 13

Acidosis

Question 14

Implications of
Hypoventilation
Hyperventilation
Diarrhoea
Vomiting
(see handout printed)
(slide 18, lecture 9)
Hypo+ hyperventilation= how are they compensated?
Diarrhoea/ Vomiting involves?

Answer 14

Left two: respiratory problem= kidney compensation

Right two: changing amount of acid/ base in the body

Question 15

Table for interpreting blood gas measurement
(slide 22, lecture 9)
+ practise ABGs
(slide 23, lecture 9)

Answer 15

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