Hyponatraemia

Aetiology

Hypovolaemic   Renal   Diuretics Diabetic ketoacidosis Osmotic diuresis Extrarenal   Vomitting Diarrhoea Bowel obstruction Sweating Burns Hypervolaemic / Euvolaemic   Renal   Renal failure Extrarenal   Iatrogenic - post surgery Cardiac failure Nephrotic syndrome Syndrome of inappropriate ADH (SIADH) Cirrhosis with ascites

Investigations

Determine volume status   U&E   Hyponatraemia Serum osmolarity MSU - electrolytes   Hypo/Hyper natraemia Urine osmolarity FBE   Haematocrit Serum Lipids   Hyperlipidaemia - causes a relative (false) hyponatraemia (pseudohyponatraemia) BSL   Hyperglycaemia - causes a relative (false) hyponatraemia

Treatment

Fluid management Hypovolaemic   Isotonic saline Elevate serum Na+ at a rate of 2mmol / L / Hr, to prevent risk of osmotic demyelination (Central Pontine Myelinosis) Hypervolaemic   Fluid restriction Salt restriction