Hyponatraemia

Question 1

What are the signs and symptoms of hyponatraemia?

Answer 1

Anorexia
Nausea
Malaise
Headache
Irritability
Confusion
Weakness
Decreased GCS and seizures

Question 2

What are the causes of hyponatraemia if the pt is dehydrated and urinary Na >20mmol/l?

Answer 2

Renal Na+ loss:

• Addison’s
• Renal failure
• Diuretic excess
• Osmolar diuresis

Question 3

What are the causes of hyponatraemia if the pt is dehydrated and urinary Na <20mmol/l?

Answer 3

Loss from elsewhere:

• D&V
• Fistulae
• Burns
• Small bowel obstruction
• Trauma
• CF
• Heat exposure

Question 4

What are the causes of hyponatraemia if the pt is NOT dehydrated and they are oedematous?

Answer 4

Nephrotic syndrome
Cardiac failure
Cirrhosis
Renal failure

Question 5

What are the causes of hyponatraemia if the pt is NOT dehydrated and they are NOT oedematous AND Urine osmolality >500mmol/kg?

Answer 5

Inappropriate ADH

Question 6

What are the causes of hyponatraemia if the pt is NOT dehydrated and they are NOT oedematous AND Urine osmolality <500mmol/kg?

Answer 6

Water overload
Severe hypothyroidism
Glucocorticoid insufficiency

Question 7

What are the potential artificial causes of hyponatraemia ?

Answer 7

Blood smaple from a drip arm
High serum lipid/protein content
Hyperglycaemia

Question 8

What are the iatrogenic causes of hyponatraemia ?

Answer 8

5% glucose infused constantly with no 0.9% saline

Question 9

What is the management of hyponatraemia ?

Answer 9

Correct underlying cause

Replace Na+ and water at same rate lost

Question 10

What is the management of hyponatraemia in a patient that is asymptomatic/chronic?

Answer 10

Fluid restriction - often enough
Demeclocycline may be needed
Max rise of 15mmol/l/day

Question 11

What is the management of hyponatraemia in apt that is symptomatic/dehydrated/acute ?

Answer 11

Cautious rehydration with 0.9% saline
Consider furosemide when not hypovolaemic to avoid overload
Max rise of 1mmol/l/day

Question 12

What is the role of vasopressor receptor antagonists (vaptans) in hyponatraemia?

Answer 12

Treating hyper/eu-volaemic cases

Promotes water excretion without loss of electrolytes

Question 13

What is the emergency management of hyponatraemia?

Answer 13

Seek expert help
Hypertonic saline at 70mmol/h +/- furosemide
Aim for gradual increase
Beware HF and central pontine myelinolysis