Endocrine Abstracts

Background: Hyponatraemia is a common electrolyte abnormality that is associated with significant morbidity and mortality in patients admitted to hospital. Fluid restriction is the recommended treatment option for syndrome of inappropriate antidiuretic hormone secretion (SIADH), a common cause of hyponatraemia with limited evidence for alternative treatment options. The aim of our study was to share the experience of our hospital in the successful management of SIADH where we also use oral sodium chloride and urea salts in addition to fluid restriction.

Methods: We collected data for patients with severe hyponatraemia (Serum Na⁺ <125 mmol/l) identified by our biochemistry lab from all samples they received. Suitable patients were identified over a two-week period. We included all those patients who were admitted to our hospital for any diagnosis and excluded those who were discharged from the emergency department or for tests completed as out-patients. Relevant data was collected from medical paper notes and drug charts with laboratory data available from patients’ electronic patient records. The treatment protocol for SIADH is set out by the hospital guidelines with fluid restriction as first line followed by addition of oral sodium chloride and/or urea salts as second line treatment options. Successful treatment is defined as improvement in serum sodium to >125 mmol/l.

Results: Thirty-eight patients with a mean age of 77 years were identified. The most common reason for admission was confusion and falls (24% and 18% respectively). Approximately one-third of the cases of hyponatraemia was due to SIADH (n=14). For patients with SIADH, successful treatment with fluid restriction alone was required in 43% of cases, combined with oral sodium chloride in another 43% of cases and only 7% required triple treatment combination of fluid restriction, oral sodium chloride and urea salts.

Conclusion: SIADH is a common cause of hyponatraemia in patients with acute hospital admissions. Fluid restriction alone is an effective treatment strategy in many of these patients. Additional solute intake is thought to increase renal free water clearance and increase electrolyte diuresis. The study demonstrates that additional solute intake in the form of oral sodium chloride or urea salts are potential additional treatment options in those resistant to fluid restriction alone to correct hyponatraemia and their potential role in management of complex cases where strict fluid restriction is contraindicated.