Hyponatremia is a low serum sodium concentration.
Classification of hyponatremia
| Category | Causes | Nota bene |
|---|---|---|
| Hypovolemic hyponatremia | Gastrointestinal losses – diarrhoea and vomiting; renal losses – diuretic overuse and mineralocorticoid deficiency; cutaneous losses – burns and sweating; third spacing of fluid | Signs of dehydration are present |
| Euvolaemic hyponatremia (dilutional hyponatremia) | SIADH, hypothyroidism, glucocorticoid deficiency, potomania | There may be no signs of dehydration or fluid overload |
| Hypervolaemic hyponatremia | Congestive heart failure, liver cirrhosis, nephrotic syndrome, renal failure | Signs of fluid overload are present |
- Artefactual causes of hyponatremia
- Blood sample from the drip arm
- High serum lipid or protein content
- Hyperglycaemia
- Add 4.3 mmol/L to plasma Na+ for every 10 mmol/l rise in glucose above normal
- Signs and symptoms
- Treatment
- Exclude a spurious result
- Review medications that may cause hyponatremia
- 0.9% normal saline for hypovolemic hyponatremia
- Serum sodium should be corrected
- If serum sodium does not correct, SIADH is likely
- Fluid restriction, demeclocycline, or vaptans for euvolemic hyponatremia (SIADH)
- Fluid restriction, loop diuretics, or vaptans for hypervolemic hyponatremia
- Hypertonic saline +/- furosemide and ICU/HDU care for severe hyponatremia (coma, seizures, or sodium < 120)
- Complications
- Osmotic demyelination syndrome can occur due to overcorrection of severe hyponatremia