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
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