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:

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 (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