Endocrine Abstracts

Introduction: Hyponatraemia is a relatively common complication following pituitary surgery. However, there is sparse data about its optimal management and impact on clinical outcomes.

Aims: To review the treatment and patient outcomes of hyponatraemia following pituitary surgery.

Methods: A retrospective single-centre study included all inpatients who developed serum sodium (sNa) ≤ 132 mmol/l following pituitary surgery from January 2016 to December 2019.

Results: Amongst 765 patients who underwent pituitary surgery over a 4-year period, 80 (10.4%) developed sNa ≤ 132 mmol/l including 42% males with a median age of 58 years. The commonest type of pituitary lesion was non--functioning pituitary adenoma (53%), followed by Cushing’s disease (11%), acromegaly (10%), craniopharyngioma (9%), and prolactinoma (5%). The mean baseline preoperative sNa level was 139 mmol/l. Postoperatively, the mean sNa was 137, 134 and 132 mmol/l on day 3, 5 and 7 respectively. The mean nadir sNa was 126 mmol/l and occurred on average 6.7 days after surgery, with 31 patients (38%) having nadir Na ≤ 125 mmol/l. The proportion of hyponatraemic patients who developed postoperative CSF leak and required lumber drainage was 16.2%, much higher than 5% amongst normonatraemic patients.

The commonest cause of hyponatraemia was SIADH (77.5%), followed by hypocortisolism (6.2%) and overzealous DDAVP administration for diabetes insipidus (6.2%), while no cases of cerebral salt wasting were documented. Treatment was fluid restriction in the majority of patients (80%), ranging from 500–1500 ml/day, while 6 patients (7.5%) were administered hypertonic saline and one patient (1.3%) received tolvaptan.

Post therapy initiation, mean sNa was 128, 129, 129, and 134 mmol/l on day 1, 2, 3 and 5 respectively. The mean time to achieve Na > 5 mmol/l in SIADH group was 4.2 days. The mean Na on discharge was 137 mmol/l, while the readmission rate was 10% and the mean length of hospital stay was 11.5 days.

Conclusion: Hyponatraemia can occur 5–7 days following pituitary surgery, primarily caused by SIADH. Postoperative CSF leak is an independent risk factor for development of hyponatraemia after pituitary surgery.

The effectiveness of fluid restriction was limited, as evidenced by slow Na correction with mean time of 4.2 days to achieve Na > 5 mmol/l, contributing to increased length of hospital stay. This study highlights the need to study the efficacy and safety of agents, such as vaptans and urea, for the management of hyponatraemia after pituitary surgery.