Hyponatremia

Question 1

What is the first step in managing hyponatremia?

Answer 1

Exclude pseudohyponatremia by measuring serum osmolarity - if it is normal then pseudo

Question 2

How do you determine what type of hyponatremia a patient has?

Answer 2

Assess voleaemic status (BP and postural drop, urine output, JVP, oedema)

Question 3

What are the causes, clinical features and treatment of hypervolemic hyponatremia?

Answer 3

Causes: Heart failure, renal failure, cirrhosis, nephrotic syndrome
Clinical features: Oedema, high BP, increased urine output
Treatment: Salt and fluid restriction, diuretics

Question 4

What are the causes, clinical features and treatment of hypovolaemic hyponatremia?

Answer 4

Causes: Diarrhoea, vomiting, burns, excess diuretics,
Clinical features: Decreased urine output, loss of consciousness, postural drop in BP
Treatment: Isotonic saline

Question 5

How would you determine the cause of euvolaemic hyponatremia?

Answer 5

• Thyroid function tests checking for hypothyroidism
• Short synatchen test to check for adrenal insufficency

—> If neither, SIADH

Question 6

How is SIADH (Syndrome of Inappropriate Antidiuretic Hormone secretion) diagnosed?

Answer 6

Diagnosis of exclusion

• Normal renal function
• Normal thyroid function
• Normal adrenal function
• No diuretics

High urine osmolality

Question 7

What drugs are commonly associated with SIADH?

Answer 7

Amitriptyline (+ other cyclic antidepressants) fluoxetine

Question 8

What is the treatment of SIADH?

Answer 8

Free water restriction