Objective: Delayed hyponatremia is an under-recognized complication of surgery for pituitary adenomas. We document the incidence, temporal profile and management of this complication.
Methods: This was a retrospective study of 222 patients who underwent transsphenoidal excision of pituitary macro adenomas between 2007 and 2016. Delayed hyponatremia was defined as serum sodium < 135 mmol/L after the 3rd postoperative day.
Results: 40 patients (18%) developed delayed hyponatremia. The median time of occurrence of delayed hyponatremia was the 7th postoperative day (range, 5-12 days). Most patients (29) were asymptomatic, the others presented with vomiting (5), seizures (3), weakness (1), paralytic ileus (1) and fever (1). In 4 patients the hyponatremia was preceded by Diabetes Insipidus on the 2nd post-operative day. Fourteen patients developed hyponatremia in spite of being on adequate steroid replacement. Thirteen patients had cortisol levels < 10 µg/dL, this included 8 with cortisol levels < 5 µg/dL.
All patients received intravenous (0.9%) saline and 12 grams oral salt. Those with serum sodium < 125 mmol/L were given3% saline. Three patients with suspected SIADH responded to fluid restriction. Steroid replacement was with intravenous hydrocortisone 50mg Q6H. One patient received prednisolone 10mg OD. Two patients received fludrocortisone 100 mcg OD. Twenty one patients normalized their serum sodium within 48 hours. Others took 3-7 days to respond. The cause for delayed hyponatremia was either the syndrome of inappropriate anti-diuretic hormone (SIADH) or cerebral salt wasting (CSW) in patients in whom hypocortisolemia was excluded.
Conclusions: Delayed hyponatremia occurred in 18% of patients after transsphenoidal surgery for pituitary macroadenomas. It usually occurs around the 7th post-operative day. We suggest routine testing for serum sodium one week after surgery. In half the patients hyponatremia gets corrected within 48 hours.
KEY WORDS: Delayed hyponatremia, Syndrome of Inappropriate Anti Diuretic Hormone (SIADH), Cerebral Salt Wasting (CSW).