Characteristics and outcomes of patients with profound hyponatraemia due to primary polydipsia.

Abstract

Hyponatraemia due to excessive fluid intake (ie primary polydipsia [PP]) is common. It may culminate in profound hyponatraemia-carrying considerable risk of morbidity. However, data on patients with PP leading to hyponatraemia are lacking. Herein, we describe the characteristics of polydiptic patients hospitalized with profound hyponatraemia and assess 1-year outcomes. Substudy of the prospective observational Co-MED Study. Patients with an episode of profound hyponatraemia (≤125mmol/L) due to PP in the medical emergency were eligible and classified into psychogenic polydipsia (PsyP), dipsogenic polydipsia (DiP) and beer potomania (BP). Symptoms, laboratory findings and factors contributing to hyponatraemia (comorbidities, medication and liquid intake) were assessed. A 1-year follow-up was performed to evaluate recurrence of hyponatraemia, readmission rate and mortality. Twenty-three patients were included (median age 56years [IQR 50-65], 74% female), seven had PsyP, eight had DiP and eight had BP. Median serum sodium of all patients was 121mmol/L (IQR 114-123), median urine osmolality 167mmol/L (IQR 105-184) and median copeptin 3.6mmol/L (IQR 1.9-5.5). Psychiatric diagnoses, particularly dependency disorder (43%) and depression (35%), were highly prevalent. Factors provoking hyponatraemia were found in all patients (eg acute water load, medication, stress). During the follow-up period, 67% of patients were readmitted, 52% of these with rehyponatraemia, and three patients (38%) with BP died. Patients with PP are more likely to be female and to have addictive and affective disorders. Given the high recurrence, rehospitalization and mortality rate, careful monitoring and long-term follow-up including controls of serum sodium, education and behavioural therapy are needed.