Cerebral salt wasting syndrome: a case report.

A case of hyponatraemia associated with subarachnoid haemorrhage is presented. The provisional diagnosis of an inappropriate antidiuresis was made and treatment with fluid restriction was instituted. However the patient continued to deteriorate as the diuresis continued and the hyponatraemia worsened, resulting in hypovolaema. The salt wasting syndrome was subsequently diagnosed and saline and fludrocortisone (0.2 mg/day) was initiated, reducing the renal salt loss, increasing the plasma sodium and improving the neurological status of the patient. Cerebral salt wasting syndrome is an important and under-recognised cause of hyponatraemia in neurosurgical patients, particularly in patients with subarachnoid hemorrhage. It is essential to differentiate it from the syndrome of inappropriate antidiuretic hormone secretion to avoid complications of hypovolaemia and reduced cerebral perfusion as illustrated by this case. Brain natriuretic peptide may be responsible for this syndrome although this requires further investigation.