Metabolic Acidosis
Definition
Acid-Base physiology
Anion gap
Differential diagnosis of metabolic acidosis with high anion gap
Lactic acidosis
Oxidative phosphorylation
Types of Lactic acidosis
Treatment of Lactic Acidosis
Metabolic Acidosis
(primary fall in serum bicarbonate)
A condition that causes a primary fall in serum bicarbonate level
a fall in HCO3- will result from:
Addition of H+ (shift right: in HCO3- )
Loss of bicarbonate (shift left: in H+)
Increase in H+ occurs in both situations
Increase in H+:
H+ is accompanied by an anion in order to maintain electrical neutrality
The anion may be Cl- (HCl administration)
The anion may be LACTATE, a KETONE, PHOSPHATE, SULPHATE, or an ingested anion
The Anion Gap:
In the body
cations = anions
Not all of the anions are measured in routine laboratory analysis
[Na+] – ([Cl-] + [HCO3-]) = 12
The usual unmeasured anions that account for the “gap” are:
Albumin
Phosphates
Sulphates
anion gap in the presence of [H+] is a marker for the presence of anions that accompany H+ but are not routinely measured
High Anion Gap Acidosis:
Type Anion:
Lactic lactate
Diabetic ketones
Uremia sulphate/phosphate
ASA salicylate
Methanol formate
E. Glycol oxalate
Lactic Acidosis
Why do we need oxygen?
For oxidative phosphorylation
What is oxidative phosphorylation?
ADP + Pi = ATP (requires energy)
The formation of ATP
What does the oxygen do?
The bulk of ATP is generated in the electron transport chain (ETC) in the mitochondrion
The energy for creating the high-energy phosphate bond is generated at several points in the ETC. So are hydrogen ions
Type A: failure of oxidative phosphorylation (PyruvateLactate)
Type B: lactate production overwhelms lactate metabolism
Type A (more severe)
Failure of ETC:
Decreased Oxygen delivery
Shock of any type
Severe hypoxemia
Severe Anemia
Inhibitors (CO, CN)
Type B (less severe)
Lactate production overwhelms lactate metabolism (not anaerobic)
Malignancies (after chemotherapy)
Hepatic failure
Drugs (biguanides, AZT, INH)
Lactic Acidosis: Treatment
Treat the underlying cause
Lower the H+ concentration
Underlying cause in this case:
Profound rapid blood loss
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