From the Research
Pathophysiology of Pseudohyponatremia
Pseudohyponatremia, or false low sodium levels, can occur in the setting of hyperglycemia (elevated blood glucose) due to several mechanisms:
- The electrolyte exclusion effect, where elevated concentrations of serum solids (such as proteins or lipids) displace serum water, resulting in a reciprocal depression in serum sodium values 1
- An increase in the measured sample's water concentration post-dilution, which can lower the sodium concentration in the sample 1
- Serum hyperviscosity, which can reduce serum delivery to the device that apportions serum and diluent, leading to inaccurate sodium measurements 1
Laboratory Methods and Pseudohyponatremia
The occurrence of pseudohyponatremia is influenced by the laboratory method used to measure serum sodium levels:
- Indirect ion-specific electrode (ISE) methods, which require pre-measurement sample dilution, can produce spuriously low sodium values in the presence of elevated serum solids 1, 2, 3
- Direct ISE methods, which do not require sample dilution, are less susceptible to pseudohyponatremia 1, 3
Clinical Implications
Pseudohyponatremia can lead to mismanagement of sodium levels in clinical practice, highlighting the importance of understanding and differentiating it from true hyponatremia:
- Patients with pseudohyponatremia do not develop water movement across cell membranes and clinical manifestations of hypotonic hyponatremia 1
- Inadvertent correction treatment for pseudohyponatremia can be potentially detrimental 1
- Careful clinical correlation is needed to avoid mismanagement of sodium levels in patients with hyperglycemia and pseudohyponatremia 4