Acidosis and Alkalosis (PK7) Flashcards
1
Q
Why is the denominator PCO2 used instead of H2CO3 for [HA] in the Henderson-Hasselbach equation?
A
- H2CO3 only exists in very small concentrations that are hard to measure clinically
- PCO2 can be used instead when multiplied by constant
2
Q
Why is solubility constant 0.23 in Henderson-Hasselbach equation instead of 5.2
A
- Different units (mmol L-1 kPa-1, not ml L-1 kPa-1)
- PV = nRT used to convert
3
Q
What does pK’ mean instead of pK?
A
Units used to convert H2CO3 to PCO2 mean pK’ is ‘apparent’ pK of the system
4
Q
How many molecules are there of HCO3- per CO2 in normal plasma, and what does this imply?
A
- 20
- As long as this ratio doesn’t change, pH will remain the same (7.4)
5
Q
What does a ratio of HCO3- : CO2 > 20 mean?
A
Alkalosis
6
Q
What does a ratio of HCO3- : CO2 < 20 mean?
A
Acidosis
7
Q
Which system will compensate for an acidosis/alkalosis
A
The unaffected system (eg. respiratory disturbance counteracted by kidneys + vice versa)
