metabolic alkalosis

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

Reference:

• Do C et al. Metabolic Alkalosis Pathogenesis, Diagnosis, and Treatment: Core Curriculum 2022. AJKD May 2022 DOI:https://doi.org/10.1053/j.ajkd.2021.12.016