A 55-year-old lady was admitted with sudden onset headache, diplopia, photophobia and confusion. CT brain showed SAH with hydrocephalus. Coiling of the aneurysm with EVD insertion was done on the same day. On day 5 post-operatively she developed hyponatremia and dropped her GCS to 10/15.
On examination she was volume depleted with dry mucous membranes and loss of skin turgor. Urine output over the previous 4 days had been 2.54 l/day, urinary sodium was elevated at 195 mmol/l with low serum sodium of 123 mmol/l. In view of the high urine output and clinical signs of hypovolaemia, cerebral salt wasting syndrome (CSWS) was felt to be the most likely diagnosis.
She was treated with i.v. 0.9% saline (200 ml/h), and CVP monitoring was instituted. After 2 h, her serum Na had dropped to 117 mmol/l, and therefore 0.9% saline was changed to hypertonic saline (1.8%).
By the following day GCS (14/15) and serum Na (129 mmol/l) had improved. However, on switching to 0.9% saline the serum Na dropped to 123 mmol/l and therefore hypertonic saline was recommenced. By day 9 serum Na had stabilised at 127 mmol/l and she was switched to normal saline.
The next day her serum Na dropped again to 119 mmol/l with persistently elevated urinary sodium (225 mmol/l) and high urine output. She was therefore changed back to hypertonic saline and this was continued until her urinary sodium level was <150 mmol/l.
By day 15, her serum Na was stable at 134 mmol/l, urinary sodium was 100 mmol/l, and GCS had improved to 15. Normal saline was recommenced with no drop in serum Na, and she was gradually weaned off i.v. fluids.
Treatment of CSWS requires replacement of excreted sodium, which can usually be achieved with i.v. normal saline. If sodium losses are very large then hypertonic saline may be required.