Pediatric Metabolic Alkalosis Workup

Updated: Oct 19, 2017
  • Author: Lennox H Huang, MD, FAAP; Chief Editor: Timothy E Corden, MD  more...
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Workup

Blood Gas, Serum Electrolytes, and Spot Urine Chloride Measurements

Measurements of blood gas and serum electrolyte levels, including calcium, are the essential laboratory studies necessary for the initial evaluation of metabolic alkalosis. An algorithm for metabolic alkalosis is shown in the image below.

Algorithm for metabolic alkalosis. Algorithm for metabolic alkalosis.

Blood gas measurement typically shows elevated pH with a high bicarbonate (HCO3) level. With compensation, the partial pressure of carbon dioxide (PCO2) may also be near the reference range or elevated.

Serum electrolyte levels may show evidence of hypokalemia, hypercalcemia, hypochloremia, or hyponatremia.

A urine chloride level below 20 mEq/L indicates chloride-responsive metabolic alkalosis. A urine chloride level over 20 mEq/L indicates chloride-resistant metabolic alkalosis.

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Diagnostic Indicators for Specific Disease States

Consider the following:

  • Patients with primary aldosteronism have metabolic alkalosis, hypokalemia, a urine chloride level above 20 mEq/L, and persistently elevated aldosterone levels despite a controlled sodium chloride (NaCl) intake of 12-15 g daily for 5 days.
  • Cushing syndrome is marked by hypersecretion of cortisol.
  • Primary reninism usually results from renovascular disease with hypertension.
  • Bartter syndrome manifests as hypokalemic metabolic alkalosis with secondary hyperaldosteronism and with renal potassium and chloride wasting.
  • Milk-alkali syndrome results from excessive oral intake of calcium, vitamin D metabolites, and absorbable alkali. Metabolic alkalosis in affected patients is usually accompanied by hypercalcemia.
  • Pyloric stenosis causes marked hypochloremia (due to loss of hydrochloric acid in gastric contents) and metabolic alkalosis. It is generally observed in male infants aged approximately 6-12 weeks. These patients present with protracted vomiting and frequently have significant dehydration and cachexia.
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