Hyponatraemia

Published on 23/05/2015 by admin

Last modified 22/04/2025

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Hyponatraemia

The normal serum sodium level is 135–145 mmol/L. Hyponatraemia refers to serum sodium levels of<135 mmol/L, and serum sodium of<120 mmol/L is considered severe.

Causes

Hypovolaemic

• Gastrointestinal losses

• Diarrhoea

• Vomiting

• Fistula

• Small bowel obstruction

• Paralytic ileus

• Renal sodium losses

• Diuretics

• Osmotic diuresis (e.g. hyperglycaemia)

• Renal failure

• Other sodium losses

• Burns

• Ascites

• Crush injuries

• Peritonitis

Euvolaemic

• Endocrine

• Severe hypothyroidism

• Addison’s disease

• Water load

• Intravenous infusions

• Water drinking (excessive)

• TURP (transurethral resection of prostate) syndrome

• SIADH

• Pulmonary disease (e.g. pneumonia, lung cancer)

• Drugs (e.g. carbamazepine)

• Intracranial disease (e.g. tumour, head injuries)

Oedematous

• Cardiac failure

• Nephrotic syndrome

Symptoms and Signs

Symptoms of hyponatraemia are related to how low the serum sodium is, and how rapidly it has developed. They can range from asymptomatic to mild nausea, vomiting, headache, malaise to diminished reflexes, seizures, stupor or coma.