Sodium abnormalities: acute hyponatraemia

Question 1

In a lot of hospital patients, hyponatraemia is mild and chronic. However, what do we class as SEVERE hyponatraemia (i.e. fall in serum sodium that leads to life threatening neurological features?)

Answer 1

Either acute (develops within 48 hours)
Or
Profound ( <125mmol/L)

Question 2

What are the symptoms and signs of acute severe hyponatraemia caused by?

Answer 2

Cerebral oedema and raised intracranial pressure

So headache, Nausea and vomiting, confusion, drowsiness, seizures, coma/reduced Glasgow coma score and encelopathy.

Question 3

Describe the management of a patient with acute severe hyponatraemia.

Answer 3

Transfer patient to a high dependancy monitored environment
Consult senior endocrinologist

Use hypertonic saline, with careful monitoring of clinical and biochemical status.

Question 4

How is hypertonic saline given to treat acute hyponatraemia

Answer 4

Give initially as 150mL of 3% saline IV over 20min

Check Na conc after 20min

Repeat 150mL infusion for another 20min

Aim for increase serum sodium of 5 mmol/L

If patient improves - stop infusion, look for cause
If no improvement - continue to give hypertonic saline

Serum Na levels must be checked for both patients at 6, 12, 24 and 48 hours.

Question 5

What is osmotic demyelination syndrome?

Answer 5

Occurs when rate of correction of serum sodium occurs too quickly. (so correct to max 10mmol/L in 24h and 8 mmol/L in next 24h)

High risk patients - extremes of age, malnourishment, existing neurological disease (so correct to max 8mmol in 24h and 14mmol/L in 48h)