Nick Russell^1
1Austin Health

Hyponatraemia is the most common electrolyte disorder managed in hospital inpatients. The most common cause is Syndrome of Inappropriate Antidiuresis (SIAD). Severe hyponatraemia (defined by symptoms) is a medical emergency, best managed with bolus hypertonic saline. Non-severe hyponatraemia due to SIAD is often managed with fluid restriction and close biochemical monitoring to prevent over-correction which risks the rare but severe complication of osmotic demyelination syndrome. Fluid restriction often fails as a treatment for hyponatraemia (or is predicted to fail based on biochemical parameters) and alternative therapies such as oral urea or tolvaptan may be given.