Pseudohyponatremia

Excerpt

Pseudohyponatremia is a rare laboratory abnormality characterized by a serum sodium concentration below 135 mEq/L in the setting of a normal serum osmolality (280 to 300 mOsm/kg). Conversely, true hyponatremia is associated with low serum osmolality and necessitates prompt evaluation for additional abnormal solutes affecting the laboratory assessment. Pseudohyponatremia is an artifact resulting from blood sample processing for sodium measurement, and failure to promptly recognize this can lead to severe complications.

Osmotically active solutes such as mannitol or hyperglycemia can contribute to pseudohyponatremia, but a severe elevation of cholesterol stands out as the primary cause. Identifying pseudohyponatremia based on false laboratory analysis is preferred. Due to the hyperosmolality and resultant fluid shifts invoked by the presence of osmotically active solutes, the serum sodium, as reported by laboratory assessment in some cases, is truly low. For this reason, one should not include hyperosmolar hyponatremia as a potential classification of pseudohyponatremia. Accurate interpretation of serum sodium values is essential for distinguishing pseudohyponatremia from other forms of hyponatremia, such as hyponatremia and hyperosmolar hyponatremia. Management primarily involves accurately interpreting serum sodium values and addressing the underlying condition responsible for elevated cholesterol levels, which may necessitate consultation with a nephrologist for proper differentiation.