alkalosis (metabolic)

Last edited 06/2022 and last reviewed 06/2022

Serum pH is normal or elevated. The main disturbance is a markedly increased serum bicarbonate; pCO2 may be slightly elevated.

Metabolic alkalosis is a widespread acid-base disturbance, especially in hospitalized patients

  • pathogenesis of metabolic alkalosis involves either a loss of fixed acid or a net accumulation of bicarbonate within the extracellular fluid
  • loss of acid may be via the gastrointestinal tract or the kidney, whereas the sources of excess alkali may be via oral or parenteral alkali intake
  • severe metabolic alkalosis in critically ill patients - arterial blood pH of 7.55 or higher - is associated with significantly increased mortality rate (1)

The principal causes are:

  • gain of alkali, for example ingestion of sodium bicarbonate, milk-alkali syndrome, or iatrogenic during cardiac arrest
  • renal loss of acid:
    • severe potassium depletion
    • hyperaldosteronism
    • Cushing's syndrome
    • Bartter's syndrome, or pseudobartter's syndrome in cystic fibrosis
    • thiazide diuretics
  • gastrointestinal loss of acid:
    • vomiting of gastric acid, classically in pyloric stenosis in infants
    • villous adenoma
    • an ileal conduit may cause a metabolic alkalosis
  • early sepsis
  • compensatory:
    • post hypercapnic acidosis
  • poisoning with ethylene glycol