Characteristics and Outcomes of Patients with Profound Hyponatremia due to Primary Polydipsia

Abstract

Objective

Hyponatremia due to excessive fluid intake (i.e. primary polydipsia (PP)) is common. It may culminate in profound hyponatremia—carrying considerable risk of morbidity. However, data on patients with PP leading to hyponatremia is lacking. Herein, we describe the characteristics of polydiptic patients hospitalised with profound hyponatremia, and assess one-year outcomes.

Design

Substudy of the prospective observational Co-MED Study.

Patients

Patients with an episode of profound hyponatremia (≤125mmol/l) due to PP in the medical emergency were eligible and classified into psychogenic polydipsia (PsyP), dipsogenic polydipsia (DiP), and beer potomania (BP).

Measurements

Symptoms, laboratory findings, and factors contributing to hyponatremia (comorbidities, medication, and liquid intake) were assessed. A one-year follow-up was performed to evaluate recurrence of hyponatremia, re-admission rate, and mortality.

Results

23 patients were included (median age 56 years [IQR 50-65], 74% female), 7 had PsyP, 8 DiP, and 8 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 diagnosis, particularly dependency disorder (43%) and depression (35%), were highly prevalent. Factors provoking hyponatremia were found in all patients (e.g. acute water load, medication, stress).

During the follow-up period, 67% of patients were readmitted, 52% of these with re-hyponatremia, and 3 patients (38%) with BP died.

Conclusion

Patients with PP are more likely to be female, and have addictive and affective disorders. Given the high recurrence, re-hospitalisation, and mortality rate, careful monitoring and long-term follow-up including controls of serum sodium, education and behavioural therapy is needed.

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