Endocrine Abstracts

Introduction: Hyponatraemia is associated with increased inpatient mortality, but there is debate about whether hyponatraemia per se contributes to mortality or is merely an epiphenomenon of severe illness.

Methods: This retrospective review of medical records included all inpatients with serum sodium (sNa)≤128 mmol/l who died at a teaching hospital over a 3-month period. The aim of this study was to examine the clinical course and the potential contribution of hyponatraemia to death.

Results: Among 139 hyponatraemic patients, 24 patients (17.3%), 13 males, 11 females, with a mean age (±S.D.) of 72.9 (±14.2) years died during hospitalisation. Nine patients had hypovolaemic hyponatraemia, eight had SIADH, three had hypervolaemic hyponatraemia, and four had hyponatraemia of unknown type. Fatal cases had a median length of hospitalisation of 21.5 days with a median exposure to sNa levels≤128 mmol/l of 4 days. On admission, nine patients had sNa≤128 mmol/l, seven had sNa 129–134 mmol/l, and eight were normonatraemic. The median sNa on admission was 132 mmol/l, at the lowest point during hospitalisation 124 mmol/l and at the time of death 135.5 mmol/l. At the time of death, seven patients (29.1%) had sNa≤128 mmol/l, three (12.5%) had sNa 129–134 mmol/l, 11 (45.8%) were normonatraemic, and three (12.5%) were hypernatraemic. The primary causes of death were: pneumonia (six cases), malignancy (five cases), cirrhosis (four case), heart failure (three cases), visceral perforation (two cases), myocardial infarction (one case), acute kidney injury (one case), stroke (one case), and cerebral vasculitis (one case). The case notes review did not identify any cases of direct contribution of hyponatraemia to death.

Discussion: This study did not identify any cases where recognised complications of hyponatraemia contributed to death, but it cannot exclude a causal link through unknown physiological effects.