What are the recommended management strategies for acute versus chronic hyponatraemia?

Management of Acute Hyponatraemia:

• Admit immediately if onset is less than 48 hours or if serum sodium is less than 125 mmol/L, or if symptomatic or hypovolaemic.
• For acute hyponatraemia with moderate or severe symptoms, administer hypertonic saline to safely raise serum sodium and reduce cerebral oedema risk.
• In acute hyponatraemia with mild or no symptoms, stop non-essential parenteral fluids and medications that provoke hyponatraemia, and treat the underlying cause.

Management of Chronic Hyponatraemia:

• For chronic hyponatraemia without moderate or severe symptoms, stop non-essential supplementary fluids and medications that provoke hyponatraemia, and treat the underlying cause.
• In hypervolaemic patients, fluid restriction is recommended to prevent further fluid overload.
• In hypovolaemic patients, restore extracellular volume with 0.9% saline infusion.
• For syndrome of inappropriate antidiuretic hormone secretion (SIADH), fluid restriction is advised; if no clear cause is found, further imaging may be needed, and specialist treatment such as tolvaptan may be considered under supervision.