Poster Presentation The Joint Annual Scientific Meetings of the Endocrine Society of Australia and the Society for Reproductive Biology 2017

Investigation and management of inpatient hyponatraemia. (#199)

Kathryn Berkman 1 , Warrick Inder 1 , Anthony Russell 1 , Ling Li 1 , Kate Haigh 1
  1. Queensland Health, Brisbane, QLD, Australia

Background: Hyponatraemia is the most common electrolyte disturbance amongst hospitalised patients at a rate of 15-30%. In general, the investigation of hyponatraemia is suboptimal and treatment remains unstandardised.

Methods: A retrospective audit was conducted of inpatients with a serum sodium (Na) concentration ≤125 mmol/L, admitted over a 3 month period March-May 2016 (n=152). Outcomes measured: demographic characteristics, investigations, accuracy of diagnosis, change in serum Na and patient outcomes.

Results: The patients were clinically assessed as euvolaemic in 46.1%, hypervolaemic in 23%, hypovolaemic in 16.4% and not documented in 14.5%. Urine Na and osmolality were performed in 72 of 152 patients (47.4%) and in 43 of 70 of euvolaemic patients (61.4%). Thyroid function tests (67.1%) and morning cortisol (45.7%) were underutilized in the euvolaemic group. On review of all data, the diagnosis was considered accurate in only 37.5% of cases. Fluid restriction resulted in a 2.5 ± 4.3 mmol/L and 1.7 ± 2.1 mmol/L increase in Na on days 1 and 3 respectively. No treatment resulted in a -2 ± 1.7 mmol/L and 0.33 ± 2.9 mmol/L change in Na on days 1 and 3 respectively. Oral urea was utilized in 5 patients whose serum Na had failed to increase with fluid restriction alone. This resulted in a 3.6 ± 2.9 mmol/L and 3.8 ± 3.4 mmol/L increase in Na on days 1 and 3 respectively. There were no cases of osmotic demyelination. The average length of stay was 15.1 days (IQR: 48). Mortality was 11.2% (17 pts). There was a significant association between nadir serum Na and mortality (p = 0.031).

Conclusions: Inpatient hyponatraemia is often inadequately investigated, leading to diagnostic errors and treatment inconsistencies. Treatment is heterogeneous and often inappropriate. In cases with hyponatraemia refractory to fluid restriction, oral urea presents an effective alternative treatment.

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