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July 7, 1975

Hypomagnesemia as a Cause Of Persistent Hypokalemia

Author Affiliations

University of New Mexico School of Medicine Albuquerque

JAMA. 1975;233(1):23-24. doi:10.1001/jama.1975.03260010025012

To the Editor.—  We wish to call to the attention of your readers the documented but little-appreciated importance of hypomagnesemia as a cause of persistent hypokalemia.

Report of a Case.—  A 40-year-old healthy woman was admitted to our burn and trauma unit after sustaining 65% total body burns. She was treated in the conventional manner but progressive dehydration and hypokalemia developed during four weeks of hospitalization. A medical consultation was requested when her serum electrolyte values were as follows: Na+, 180 mEq/liter; K+, 2.0 mEq/liter; Cl-, 128 mEq/liter; and CO2, 26 mEq/liter. A diagnosis of secondary hyperaldosteronism was made and intravenous fluids were increased to obtain a positive free water balance. During the next four days, serum Na+ value gradually fell to 147 mEq/liter, but serum K+ remained at 2.0 mEq/liter in spite of massive supplementation of potassium chloride (25 to 40 mEq/hr intravenously). Urinary K+ values demonstrated that