Metabolic acidosis

See also: Acidosis

Metabolic acidosis refers to an abnormal chemical compositional state of the body that clinicians characterize as abnormally increased acidity — measured as pH reduction or hydrogen ion concentration [H⁺ increase — accompanied by abnormally reduced bicarbonate (HCO₃^-) concentration in the extracellular fluid (ECF) compartment of the body, acknowledging that in most cases similar compositional abnormalities exist in the intracellular compartment (ICF) as well.

Common examples of metabolic acidosis include:

• Diabetic ketoacidosis, caused by abnormally high rates of liver production of ketoacids, ultimately due to severe insulin deficiency;
• Lactic acidosis, caused by abnormally high rates of lactic acid production due to reduced oxygen delivery to body tissues; prolonged exercise; liver failure;
• Renal acidosis, caused by diseased kidneys that fail to deliver sufficient bicarbonate to the body in the circumstances of bicarbonate losses due to:
  • titration of bicarbonate by noncarbonic acids produced during metabolism foods from diets that consist of more acid-producing than base producing foods;
  • down-setting of the plasma bicarbonate concentration threshold at which the kidneys return to the body all the bicarbonate filtered by the kidneys from the blood.

Clinicians distinguish between metabolic acidosis and respiratory acidosis. In the latter, the acid, carbonic acid, or H₂CO₃, deriving from the hydration reaction with the metabolic waste product, carbon dioxide(CO₂ — CO₂ + H₂0 = H₂CO₃ = H⁺ + HCO₃^– — accumulates in body fluids due to insufficient rates of excretion into the atmosphere through exhalation by the lungs. Abnormally increased acidity results from dissociation of carbonic acid, yielding hydrogen ions, but the bicarbonate concentration increases to abnormally increased levels as the dissociation of carbonic acid also yields bicarbonate. Abnormally increased acidity characterizes both metabolic acidosis and respiratory acidosis, but an abnormally reduced bicarbonate concentration characterizes only metabolic acidosis. Metabolic acidosis involves only noncarbonic acids, of which numerous such acids can underlie the condition.