Figure 417

Evaluation in suspected magnesium (Mg) deficiency. Serum Mg levels may not always indicate total body stores. More refined tools used to assess the status of Mg in erythrocytes, muscle, lymphocytes, bone, isotope studies, and indicators of intracellular Mg, are not routinely available. Screening for Mg deficiency relies on the fact that urinary Mg decreases rapidly in the face of Mg depletion in the presence of normal renal function [2,6,8-15,18]. (Adapted from Al-Ghamdi and coworkers [11].)

MAGNESIUM (Mg) TOLERANCE TEST FOR PATIENTS WITH NORMAL SERUM MAGNESIUM

Time

Action

0-24 h End

Urine (spot or timed) for molar Mg:Cr ratio IV infusion of 2.4 mg (0.1 mmol) of Mg/kg lean body wt in 50 mL of 50% dextrose Collect urine (staring with Mg infusion) for Mg and Cr Calculate % Mg retained (%M)

(24-h urine Mg) - ([Preinfusion urine Mg:Cr] X [24-h urine Cr]) ^

Total Mg infused

0 0

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