18 Renal Acid Base Balance
Renal Physiology
PART
THREE
Renal Acid-Base
Balance
1
Acid
•
•
•
•
An acid is when hydrogen ions accumulate in a solution.
It becomes more acidic
[H+] increases = more acidity
CO2 is an example of an acid.
HCl
2
H+
H+
ClH+
H+
ClH+
7
ClpH
ClCl-
As concentration of hydrogen ions increases, pH drops
Base
• A base is chemical that will remove hydrogen ions from the solution
• Bicarbonate is an example of a base.
NaOH
Na+ OH- H +
ClH+
ClNa+ OHH+
ClH+
Cl- Na+ OHH+
ClNa+ OH-
2
7
pH
Acids and basis neutralize eachother
A change of 1 pH unit corresponds to a 10-fold change in hydrogen ion concentration 2
Na+
ClNa+
H+
Na+
7
ClH2O
OH-
Na+
Cl-
Cl-
pH
Acids are being created constantly through metabolism
• Anaerobic respiration of glucose produces lactic acid
• Fat metabolism yields organic acids and ketone bodies
• Carbon dioxide is also an acid.
Acids must be buffered, transported away from cells, and eliminated from the body
Phosphate: important renal tubular buffer
HPO4- + H+
H2PO 4
Ammonia: important renal tubular buffer
NH3 + H+
NH4+
Proteins: important intracellular and plasma buffers
H+ + Hb
HHb
Bicarbonate: most important Extracellular buffer
H2O + CO2 H2CO3
H+ + HCO3 -
Buffering is good, but it is a temporary solution. Excess acids and bases must be eliminated from the body gas H2O + CO2 H2CO3
aqueous
H+ + HCO3 Kidneys can remove excess non-gas acids and bases
Lungs eliminate carbon dioxide
Excessive Acids and Bases can cause pH changes---denature proteins
• Normal pH of body fluids is 7.40
• Alkalosis (alkalemia) – arterial blood pH rises above 7.45
• Acidosis (acidemia) – arterial pH drops below 7.35
• Acidosis:
– too much acid
– Too little base
• Alkalosis
– Too much base
– Too little acid
Compensation for deviation
• Lungs (only if not a respiratory problem)
– If too much acid (low pH)—respiratory system will ventilate more (remove CO2) and this will raise pH back toward set point
– If too little acid (high
PART
THREE
Renal Acid-Base
Balance
1
Acid
•
•
•
•
An acid is when hydrogen ions accumulate in a solution.
It becomes more acidic
[H+] increases = more acidity
CO2 is an example of an acid.
HCl
2
H+
H+
ClH+
H+
ClH+
7
ClpH
ClCl-
As concentration of hydrogen ions increases, pH drops
Base
• A base is chemical that will remove hydrogen ions from the solution
• Bicarbonate is an example of a base.
NaOH
Na+ OH- H +
ClH+
ClNa+ OHH+
ClH+
Cl- Na+ OHH+
ClNa+ OH-
2
7
pH
Acids and basis neutralize eachother
A change of 1 pH unit corresponds to a 10-fold change in hydrogen ion concentration 2
Na+
ClNa+
H+
Na+
7
ClH2O
OH-
Na+
Cl-
Cl-
pH
Acids are being created constantly through metabolism
• Anaerobic respiration of glucose produces lactic acid
• Fat metabolism yields organic acids and ketone bodies
• Carbon dioxide is also an acid.
Acids must be buffered, transported away from cells, and eliminated from the body
Phosphate: important renal tubular buffer
HPO4- + H+
H2PO 4
Ammonia: important renal tubular buffer
NH3 + H+
NH4+
Proteins: important intracellular and plasma buffers
H+ + Hb
HHb
Bicarbonate: most important Extracellular buffer
H2O + CO2 H2CO3
H+ + HCO3 -
Buffering is good, but it is a temporary solution. Excess acids and bases must be eliminated from the body gas H2O + CO2 H2CO3
aqueous
H+ + HCO3 Kidneys can remove excess non-gas acids and bases
Lungs eliminate carbon dioxide
Excessive Acids and Bases can cause pH changes---denature proteins
• Normal pH of body fluids is 7.40
• Alkalosis (alkalemia) – arterial blood pH rises above 7.45
• Acidosis (acidemia) – arterial pH drops below 7.35
• Acidosis:
– too much acid
– Too little base
• Alkalosis
– Too much base
– Too little acid
Compensation for deviation
• Lungs (only if not a respiratory problem)
– If too much acid (low pH)—respiratory system will ventilate more (remove CO2) and this will raise pH back toward set point
– If too little acid (high