Know how to diagnose and treatmetabolic alkalosis

Know how to diagnose and treatmetabolic alkalosis: Excerpt from Avoiding Common Pediatric Errors

Author: Megha Shah Fitzpatrick, MD

What to Do - Make a Decision

Alkalosis is a pathologic process that results in a decrease in the overall hydrogen ion concentration in the body. A metabolic alkalosis is the result of an elevated serum bicarbonate concentration. The normal serum bicarbonate level is 23 to 28 mEq/L. Therefore, a metabolic alkalosis is a serum bicarbonate level >28 mEq/L. The most common causes of metabolic alkalosis in children are emesis and diuretic use. The etiologies of metabolic alkalosis are divided into two categories based on the urine chloride level. A metabolic alkalosis can be thought of as a failure of the kidney to eliminate bicarbonate at a normal capacity.

Iftheurinechlorideis<15mEq/L,themetabolicalkalosisisconsidered to bechloride-responsive.Thistypeofmetabolicalkalosisusuallyexistswith a concurrent potassium deficiency to decrease the glomerular filtration rate or enhance proximal fractional bicarbonate reabsorption or both. This combinationofdisordersevokessecondaryhyperreninemichyperaldosteronism. The alkalosis may be improved by correcting the chloride deficit through the administration of a chloride salt, either sodium chloride or potassium chloride. Common causes of chloride responsive metabolic alkalosis include gastric losses due to emesis or nasogastric suction, loop or thiazide diuretics, chloride-losing diarrhea, chloride-deficient formula, cystic fibrosis, and posthypercapnic states.

Iftheurinechlorideis>20mEq/L,themetabolicalkalosisisconsidered to be chloride-resistant and is generally secondary to hypermineralocorticoidism and hypokalemia. In this case, the alkalosis can be corrected by removing the excess mineralocorticoid. This type of metabolic alkalosis in children is then further divided into two groups based on normal and abnormal blood pressure. The etiology ofchloride-resistantmetabolicalkalosis with normal blood pressure in children includes adrenal adenoma or hyperplasia, renovascular disease, rennin-secreting tumors, Cushing syndrome, 17 β-hydroxylase deficiency, 11 β-hydroxylase deficiency, and Liddle syndrome,andanautosomaldominantdisordermimickinghyperaldosteronism. In children with normal blood pressures and chloride resistant metabolic alkalosis, common causes include Gitelman syndrome, Bartter syndrome (both renal tubular salt wasting disorders), and exogenous base administration. The most useful diagnostic test to help determine the etiology of a metabolic acidosis in children is a spot urine chloride test. After the etiology of the alkalosis is determined, the treatment can be instituted by replacing chloride or removing the excess mineralocorticoid.

Suggested Readings

Behrman RE, Kleigman RM, Jenson HB, eds. Nelson Textbook of Pediatrics. 17th ed. Philadelphia: Saunders; 2004. Brenner BM, Levine SA, eds. Brenner and Rector's The Kidney. 7th ed. Philadelphia: WB Saunders; 2004.

Book Source Details

• Book Title: Avoiding Common Pediatric Errors
• Author(s): Anthony D Slonim MD, DrPH; Lisa Marcucci MD
• Year of Publication: 2008
• Copyright Details: Avoiding Common Pediatric Errors, Copyright © 2008 Lippincott Williams & Wilkins.

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Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.

More About This Book: Title: Avoiding Common Pediatric Errors Authors: Anthony D Slonim MD, DrPH; Lisa Marcucci MD Publisher: Lippincott Williams & Wilkins Copyright: 2008 ISBN: 0-7817-7489-6

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