Metabolic alkalosis is always characterized by a chloride deficit, except in the possible case of mild hypochloremia associated with fluid excess. Chloride depletion is typically associated with blood volume and potassium depletion, so that chloride is best administered as sodium chloride and potassium chloride solutions. The blood volume deficit is variable, and large amounts of sodium chloride should be given until blood volume and natremia are corrected (as shown by an increase in urinary sodium excretion if renal function is normal). The potassium deficit can reach 1000 mmol, and potassium urinary wasting will persist until the alkalosis is corrected. Potassium chloride should be infused at a rate of 150 to 300 mmol/day to restore and maintain the serum potassium concentration above 4 mmol/l. Rectal administration of calcium chloride has been proposed, owing to the chloride reabsorption ability of the colonic mucosa, but this route only allows limited amounts of fluids. When given in sufficient amounts, sodium chloride and/or potassium chloride solutions generally reverse the alkalosis within a few days. Although mineralocorticoid excess should be identified as a maintenance factor when present, its correction is less important in critically ill patients because it causes only mild metabolic alkalosis by itself. If reversal of maintenance factors is ineffective or is not possible (e.g. in renal or cardiac failure), or if severe clinical complications require rapid correction, more specific approaches can be considered.
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