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Equation of Koch et al for Estimating Ionized Magnesium Levels from the Total Magnesium Concentration

Purpose: To estimate the ionized magnesium level for a patient in the ICU from the total magnesium concentration using the equation of Koch et al.

Description

Koch et al studied total and ionized magnesium levels in patients in the intensive care unit (ICU). They determined that the ionized magnesium could be estimated based on the total magnesium serum level. The authors are from the University of Texas in Houston.


ionized magnesium in mmol/L =

= (0.66 * (total magnesium in mmol/L)) + 0.039

 

This can be reversed to estimate the total magnesium if the ionized level is known:

 

total magnesium in mmol/L =

= ((ionized magnesium in mmol/L) - 0.039) / 0.66 =

= (1.515 * (ionized magnesium)) - 0.059

 

Limitation:

• The authors tested the relationship over a range near the normal range (total magnesium from 0.57 to 1.08 mmol/L). Whether the relationship exists at very low or high values is undetermined.


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Specialty

Objective

ICD-10