Endocrine Abstracts

Hyponatraemia is associated with adverse outcomes including increased mortality and risk of falls. It is not previously known whether hyponatraemia, on discharge from hospital, is associated with an increased risk of readmission.

We conducted a retrospective cohort study identifying all patients admitted to a UK teaching hospital as emergency general medical admissions over a 2-month period. We identified all readmissions within 28 days of discharge and collected data on diagnosis, drug treatment, admission, nadir and discharge serum sodium. Hyponatraemia was defined as [Na] <135 mmol/l. Patients who died during the initial admission or who remained in hospital were excluded from the study.

Results: 1527 patients were included in the dataset. 26% (397/1527) of patients demonstrated hyponatraemia at some point during their admission and 9% (141/1527) were hyponatraemic at discharge. 238 (16%) patients were readmitted within 28 days. Hyponatraemia at discharge (Na<135 mmol/l) was associated with an increased risk of re-admission, odds ratio 1.7 (P=0.0155). Moderate or severe hyponatraemia (Na<130 mmol/l) showed a stronger association with readmission: odds ratio 3.4 (P=0.007). The prevalence of congestive cardiac failure and the use of anticonvulsant medication were both significantly higher in the re-admitted group (16 vs 6% and 22 vs 11% respectively).

Conclusion: This study identified hyponatraemia on discharge from hospital as a significant and potentially avoidable risk factor for readmission within 28 days.