Acid/Base Physiology Flashcards
What is the henderson hasselbalch equation?
pH = pKa + log ( [A-] / [HA] )
Are the end products of metabolism generally acids or bases?
Acids
What is pKa?
This is the pH at which the concentration of acid and its conjugate base are equal in a buffering system.
pH = pKa + log ( [A-] / [HA] )
When [A-] = [Ha], pH = pKa
What makes an optimal buffer system?
A buffer system in which the pKa is as close as possible as your target pH
Name 3 intracellular buffer systems
- Organic phosphates
- Proteins
- Hemoglobin
Name 4 extracellular buffer systems
- Proteins
- Albumin
- Phosphate
- Bicarbonate
What is the bicarbonate buffering system and what enzyme participates?
This is the bicarbonate buffering system. Notice that ventilation can get rid of CO2 and can drive the reaction towards the left.
Why is it okay to substitute CO2 as the conjugate acid for bicarbonate (HCO3-)?
H2CO3 is rapidly converted by carbonic anhydrase so CO2 can be substituted as bicarbonate’s conjugate acid in equations.
What is the Henderson–Hasselbalch equation for the bicarbonate buffering system?
pH = 6.1 + log ( [HCO3-] / 0.03PaCO2)
What is a typical [HCO3-]?
24 meq/L
What is a typical PaCO2?
40 torr
Plug in typical values to the bicarbonate Henderson–Hasselbalch equation. What do you get for the pH?
pH = 6.1 + log (24/ 0.03(40))
= 7.4
What is the pH of a typical arterial blood sample?
7.4
What is normal arterial blood pH range? how about for venous blood?
Arterial: 7.38-7.43
Venous: 7.34-7.37
Is blood pH typically higher or lower than normal in Denver?
A little higher because at higher altitudes you tend to blow down more CO2.
Is venous pH higher or lower than arterial pH? Why?
Venous pH is more acidic because metabolic end products are acidic.
What is the buffer that keeps venous pH only slightly lower and venous PCO2 only slightly higher despite the amount of CO2 being carried?
Deoxyhemoglobin
What is acidemia?
More acid in the blood than normal, resulting in a lower pH (less than 7.40)
What is alkalemia?
More base (or less acid) in the blood than normal resulting in a higher pH (greater than 7.40)