UTILITY OF EXPRESSING SERUM SODIUM PER UNIT OF WATER IN ASSESSING HYPONTREMIA

Total protein and total lipid are the major components of the total solids of serum and they displace the water and sodium of serum. To differentiate the spurious hyponatremias, caused by hyperproteinemia and hyperlipidemia, from the true hyponatremias, a knowledge of whether or not the percentage of water in serum is essentially normal is required. To determine serum water concentration indirectly, a simple modification of a standard formula is proposed, utilizing both total serum protein and total serum lipid measurements. This can be used to relate or correct serum sodium concentration in mEq./liter of serum to mEq./liter of serum water. Generally available chemical methods to determine total serum protein and total serum lipid concentrations can be used to estimate serum water content by a general formula. Refractive index and specific gravity methods to determine serum protein and water content may be invalid in hyperlipidemia. © 1969.