Endocrine Abstracts

Introduction: Hyponatremia is the most common electrolyte disorder in hospitalized patients. SIADH is characterized by euvolemic hyponatremia with sodium and urine osmolality inappropriately high. The selective antagonist of the vasopressin V2 receptor (tolvaptan) helps to eliminate water free of solute (aquaresis), being effective in treating this condition.

Objetive: Evaluate the efficacy and safety of tolvaptan in the treatment of SIADH.

Subjects and methods: Prospective observational study, sequential sampling of 9 patients with SIADH treated with tolvaptan. We evaluated causes associated with SIADH, clinical manifestations of hyponatremia, changes in plasma sodium during use of tolvaptan. Descriptive statistics, median (P25–P75) (SPSS 11.0).

Results: Age 65 (53–78) years, 33% male, 33% asymptomatic. Main symptoms: somnolence (50%), nausea (37%), disorientation (37%), headache (37%), lethargy (25%), visual hallucinations (12%). Causes associated with SIADH: cancer (3), hip surgery (1), brain pathology: subarachnoid hemorrhage (1), basilar artery acute thrombosis (1), pituitary surgery (1), meningioma surgery (1), transverse myelitis (1). Center protocol: indication of tolvaptan in patients with SIADH that do not improve with fluid restriction and sodium intake (i.v./oral), analytical control at 8 and 24 h, if rise >8 mEq (8 h) and >12 mEq (24 h) did not repeat new dose, indicated monitoring. Starting dose was 15 mg, increased to 30 mg in four patients and 45 mg in two. The duration of treatment was 17 (5–40) days, except for two patients who continues to this day. Plasma sodium value for initiation of tolvaptan 127 (122–127) mEq/l. Changes in sodium: 131 (122–132) (n=7) in the first 8 h, 132 (127–135) (n=9) at 24 h and 131 (130–133) (n=8) in the 48 h. One patient gained 15 mEq/l at 12 h and another reached 14 mEq/l in 24 h, in the last two patients discontinued treatment had to be reset by further decline. One patient was administered a single dose.

Conclusion: Treatment with tolvaptan in patients with SIADH is a safe and effective treatment, determining a progressive slow-rising serum sodium.

Declaration of interest: The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project.

Funding: This research did not receive any specific grant from any funding agency in the public, commercial or not-for-profit sector.