[Diagnosis and management of hyponatremia]

Hyponatremia affects more than 30 % of hospitalized patients in Switzerland, increasing morbidity, mortality, and healthcare costs. Defined by a plasma sodium concentration <135 mmol/l, it is often due to a relative excess of water, leading to a decrease in plasma osmolality. Diagnosis relies primarily on the measurement of plasma and urine osmolality and urine sodium level to determine which additional tests are needed to identify the etiology. Management begins with clinical assessment. In cases of severe symptoms, administration of 150 ml hypertonic saline with close monitoring of serum sodium is required. Once symptoms have been stabilized, an etiological treatment is recommended while ensuring that the correction rate is controlled.