Metabolic Acidosis

Metabolic Acidosis

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:

 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 (PyruvateLactate)
 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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