Patients with increased concentrations of lipid or protein in the blood will have proportionately less water present in a given volume. This means that electrolytes and other compounds distributed in water will appear to be at a lower concentration than they are physiologically. While this classically presents as pseudohyponatremia, it may mask hypernatremia (pseudonormonatremia).


The normal serum or plasma water content is about 93%.


With marked elevations in lipids or proteins the water content is reduced.


estimated sodium concentration at a water content of 93% =

= (measured concentration in mmol/L) * 93 / (percent water content)



• The water content is a whole number from 0 to 100.

• 93 corresponds to 93%.

• Methods for measuring water content are given in Chapter 2. For the implementation I am using the method of Waugh.


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