From the Guidelines
Pseudohypernatremia is a laboratory artifact that should be suspected when serum sodium levels are elevated without corresponding clinical symptoms, and its diagnosis and management should focus on identifying and treating the underlying cause, such as severe hyperlipidemia or hyperproteinemia, rather than correcting sodium levels. When considering the management of pseudohypernatremia, it's essential to understand that it is not a condition that requires direct treatment of sodium levels, but rather the treatment of the underlying condition that is causing the laboratory artifact. The provided evidence, although focused on hyperkalaemia, highlights the importance of considering laboratory artifacts in the interpretation of electrolyte imbalances, as seen in the discussion on pseudo-hyperkalaemia 1. Key points to consider in the diagnosis of pseudohypernatremia include:
- Severe hyperlipidemia or hyperproteinemia as common causes
- Lack of symptoms of sodium excess, such as thirst or neurological disturbances
- The need for direct ion-selective electrode methods for accurate sodium measurement
- Treatment focusing on the underlying condition rather than sodium correction. In clinical practice, pseudohypernatremia can be encountered in various scenarios, including uncontrolled diabetes, alcoholism, multiple myeloma, and intravenous immunoglobulin therapy, where hyperlipidemia or hyperproteinemia can lead to falsely elevated serum sodium levels 1. Given the potential for laboratory artifacts to mislead clinical decision-making, it is crucial to approach electrolyte imbalances with a critical consideration of the patient's clinical presentation and underlying conditions, rather than relying solely on laboratory values.
From the Research
Pseudohypernatremia
- Pseudohypernatremia is a condition where the serum sodium concentration is falsely elevated due to an increased mass of nonaqueous components of serum, such as lipids and proteins 2.
- This condition can occur when the serum sample is measured using indirect potentiometry, which requires dilution of the sample prior to measurement 3, 4.
- The flame photometry method can also give false results, as it measures sodium concentration in whole plasma, rather than in serum water 3.
- A sodium-selective electrode can give the true, physiologically pertinent sodium concentration, as it measures sodium activity in serum water 3.
Mechanisms and Diagnosis
- Pseudohypernatremia can be caused by a decrease in the serum water concentration, resulting in a reciprocal depression in serum sodium values 4.
- The condition can also be caused by an increase in the measured sample's water concentration post-dilution, which can lower the sodium concentration in the sample 4.
- Serum hyperviscosity can also reduce serum delivery to the device that apportions serum and diluent, leading to pseudohypernatremia 4.
- Diagnosis of pseudohypernatremia can be made by measuring the serum sodium concentration using a direct ion-specific electrode (ISE) or by correcting the indirect ISE measurement for non-water bias 2.
Clinical Associations and Management
- Pseudohypernatremia is often associated with conditions such as hypoproteinemia, which can have a decreased plasma solids content 4.
- Patients with pseudohypernatremia do not develop water movement across cell membranes and clinical manifestations of hypertonic hypernatremia 4.
- Pseudohypernatremia does not require treatment to address the serum sodium concentration, and any inadvertent correction treatment can be potentially detrimental 4, 5.