BOF: 44
A 60-year-old male is being investigated for cough. He is
a heavy smoker.
On examination there is tar staining of his fingers but
no other physical signs. Investigations:
Sodium 119 mmol/L
Potassium 3.6 mmol /L
Urea 4.5 mmol/L
Glucose 5.1 mmol/L
Urinary sodium 56 mmol/L
Urine osmolality 456 mOsm/kg
In this patient which one of the following interventions
would you implement?
a)
Fluid restriction
b)
Saline infusion
c)
Treat with prednisolone
d)
Treat with fludrocortisone
e)
Treat with a loop diuretic
Answer: a)
The patient has hyponatraemia. The calculated osmolality
is 2(Na+K) + urea + glucose which is 254.8
With this low osmolality one would expect the kidneys to
excrete dilute urine and conserve sodium
Failure to do so would suggest the patient has SIADH
Hence management would be fluid restriction
Revision Tip
Revise SIADH KEYS to SUCCESS in
Medicine page 20-22
