The New England Journal of MedicineThe Syndrome of Inappropriate Antidiuresis

During a yearly check-up, it was discovered that an 85-year-old man had a serum sodium concentration of 128 mmol per liter. He reported experiencing a decline in mental speed and unsteadiness in his walk.

In the realm of medical science, the understanding and management of hyponatremia and Syndrome of Inappropriate Antidiuresis (SIAD) continue to evolve. This article provides a vignette of a patient, a comprehensive overview of SIAD, its causes, symptoms, diagnosis, and treatment strategies, along with areas of uncertainty and future research directions.

Key Points

• SIAD is a condition characterized by excessive release of antidiuretic hormone (ADH), leading to water retention by the kidneys and an excess of water relative to sodium and potassium content.
• Symptoms can range from mild and nonspecific to severe and life-threatening.
• SIAD can be caused by various factors including cancer, certain medications, pulmonary conditions, disorders of the central nervous system, postoperative state, severe nausea, and stress.
• Treatment for SIAD depends on its cause and severity. For severely symptomatic SIAD, emergency treatment with 3% sodium chloride may be necessary.
• There are several areas of uncertainty in the understanding and management of hyponatremia and SIAD. More research is needed to confirm causal relationships between chronic hyponatremia and adverse outcomes, determine whether reversing hyponatremia results in improved long-term outcomes, assess emergency management strategies for hyponatremia, and evaluate the efficacy and safety of smaller starting doses of tolvaptan.

According to the authors, hyponatremia is present in about 35% of hospitalized patients.

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