Characteristics, Management and Outcomes of Patients with Hyponatraemia Presenting to an Irish Tertiary Hospital

Objective: Hyponatraemia is the most common electrolyte abnormality in clinical practice and is associated with increased in-hospital mortality and length of stay (LOS). The aims of this study were to evaluate the prevalence of hyponatraemia in adult medical inpatients; compliance with consensus guidelines regarding evaluation and management of hyponatraemia; and LOS and mortality.

Design: This was a retrospective single-centre observational study conducted in a tertiary-level Irish hospital.

Methods: Adult patients admitted under the medical services over a two-month period with a serum sodium (sNa) <135mmol/L were included. Patients were classified according to nadir sNa during their admission; mild, moderate and severe hyponatraemia defined as a sNa between 130-134mmol/L, 125-129mmol/L and <125mmol/L respectively. Clinical information was gathered retrospectively.

Results: 486 patient episodes of hyponatraemia were included. The prevalence of hyponatraemia was 32.9%.The median age was 78 (min-max:16-100) years and 239 (49.0%) were female. The median nadir sNa was 132 (min-max:105-143)mmol/L. Eighty-seven (17.9%) and 48 (9.9%) patients had moderate and severe hyponatraemia. In cases of moderate and severe hyponatraemia, the most common cause of hyponatraemia was hypovolaemia (n=33, 24.4%). Ninety-one patients (67.4%) with moderate and severe hyponatraemia had active treatment of hyponatraemia and 33 (24.4%) had input from a specialist service. The mean LOS was 15.0 (±22.5), 19.3 (±21.7) and 21.2 (±45.5) (p=0.01) days in mild, moderate and severe hyponatraemia respectively. Overall inpatient mortality was 7.0% (n=34).

Conclusions: Hyponatraemia is often incompletely investigated, suboptimally managed with insufficient input from specialist services sought in a large tertiary hospital. Hyponatraemia therefore represents a potential intervention target to reduce inpatient morbidity, mortality and healthcare costs.