pseudohyponatrémia

Pseudohyponatremia is a clinical syndrome characterized by low serum sodium levels (hyponatremia) that do not correlate with an increase in total body water or extracellular fluid volume. This condition is distinct from true hyponatremia, where the low sodium levels are due to an excess of total body water or extracellular fluid volume. Pseudohyponatremia is often seen in patients with certain medical conditions, such as syndrome of inappropriate antidiuretic hormone secretion (SIADH), liver cirrhosis, and heart failure.

The primary cause of pseudohyponatremia is the presence of proteins or other non-electrolytes in the bloodstream, which can dilute the measured sodium levels. These proteins can be endogenous, such as those produced by the liver in conditions like cirrhosis, or exogenous, such as those from intravenous fluids or medications. The dilution effect can lead to a falsely low sodium reading, even when the patient's total body water and extracellular fluid volume are normal.

Diagnosis of pseudohyponatremia typically involves a thorough clinical evaluation and laboratory tests. A detailed medical history, physical examination, and additional blood tests, such as osmolality and urine analysis, may be necessary to differentiate pseudohyponatremia from true hyponatremia. Treatment focuses on addressing the underlying cause, such as managing SIADH with fluid restriction or treating liver cirrhosis with appropriate medications. In some cases, the use of specific sodium measurement techniques, like ion-specific electrodes, can help distinguish between pseudohyponatremia and true hyponatremia.