Endocrine Abstracts

Introduction: Hypotonic hyponatremia is frequently observed after pituitary surgery. In this context, use of vasopressin V2-receptor antagonists is not standardized. The aim of this retrospective study is to explore the role of Tolvaptan in the management of acute hyponatraemia after pituitary surgery.

Methods: We collected clinical, safety and efficacy data of patients treated with Tolvaptan after pituitary surgeryin our Centre between April 2011 and February 2019.

Results: In 12 patients (8 women, median age 57.5 years) treated with Tolvaptan, hyponatraemia occurred in the 4th–7th post-operative day and was preceded by diabetes insipidusin 9 cases. In 5 patients the first line of treatment was 24 hours fluid restriction (range 6–36 hours), however the procedure was ineffective (median variation in sodium levels: –3, range: –8 to –1 mEq/l).

Tolvaptan was administered in a single dose in 8 patients and in 2 doses in 4 [initial dosage: 7.5 mg (n = 5), 15 mg (n = 6), 30 mg (n = 1)]. Median pre-Tolvaptan sodium was 125 mEq/l (range 112–129). One patient was mildly symptomatic, two patients had moderate symptoms and one severe. All patients were euvolemics. Twenty-four hours after the last administration of Tolvaptan, sodium was normalized in 9 out of 12 patients. Overcorrection (151 mEq/l) was observed in one patient, whereas mild hyponatremia persisted in 2. In two patients treated with a single dose of Tolvaptan, initial normalization of natremia was followed by further reduction in sodium levels (after 48 and 72 hours, respectively). No patient developed any side effects during Tolvaptan treatment. Correction rate was 12.5 (5 – 26) mEq/l/24 h after the first dose of Tolvaptan, and 11.5 (8 – 16) mEq/l/24 h after the second dose, with an absolute variation of natremia of +15.5 (7 – 26) mEq/l. No correlation between different doses provided and rate of correction was observed. Instead, overall variation of natremia was inversely proportional to the pre-treatment sodium levels (P = 0.02). Overall, median length of hyponatraemia was 2 days (1.5 – 6).

Conclusions: Even at low doses, Tolvaptan is an effective and safe treatment for transient acute hyponatraemia in patients who underwent pituitary surgery, when fluid restriction is unable to determine an increase in sodium levels. In some patients, a single administration of Tolvaptan may not be sufficient and repeated administrations should be considered until hyponatraemia is resolved.