Endocrine Abstracts

Introduction: Hyponatraemia is the most common electrolyte abnormality encountered in hospitalised patients.

Methods: This retrospective study included all inpatients with serum sodium ≤128 mmol/l at any point during their hospital stay between 1st March 2013 and 31st May 2013. Full review of medical case notes and laboratory results was undertaken in order to determine the comorbidities, drug history and aetiology of inpatients with hyponatraemia.

Results: 139 patients (69 males and 70 females) with a mean age (±S.D.) of 70.2±16.1 years were identified over this 3-month period. Most patients (77.0%) were under the care of medical specialities, with the specialities most frequently represented being geriatrics (16.5%), hepatology (14.4%), general medicine (13.7%), oncology (8.6%), cardiology (5.8%), neurology (5%) and renal (5%).

The most common comorbidities were hypertension (50.4%), lung disease (28.8%), diabetes (25.2%), arrhythmia (25.2%), liver disease (25.2%), active malignancy (24.5%), heart failure (21.6%), and chronic kidney disease (21.6%). The most frequently prescribed drugs were proton pump inhibitors (49.6%), opioids (28.8%), loop diuretics (27.3%), ACE-inhibitors (26.6%), K-sparing diuretics (13.7%), thyroxine (12.2%).

Only 41.7% of patients had the aetiology of hyponatraemia recorded in the medical notes. Among these patients, the largest proportion (46.6%) had hypovolaemic hyponatraemia (24.1% due to diuretics, 13.9% due to gastrointestinal Na losses, 8.6% due to poor oral intake). 34.5% had euvolaemic hyponatraemia, in particular 10.3% had SIADH due to pneumonia, 8.7% SIADH due to miscellaneous causes, 8.6% SIADH of unknown cause and 6.9% malignant SIADH. Finally, 18.9% had hypervolaemic hyponatraemia, either due to cirrhosis (10.3%) or due to heart failure (8.6%).

Discussion: Most inpatients with hyponatraemia had multiple comorbidities and did not have their aetiology of hyponatraemia recorded. Taking into account their variety of aetiologies and the wide distribution into various specialities, different models of care delivery incorporating expert input may be necessary to improve hyponatraemic patients’ care.