Endocrine Abstracts

Hyponatremia is an electrolye disorder which is relatively common in hospitalised patients. Usually it is asymptomatic and mild but in severe cases has been associated with confusion and increased risk of morbidity and death. The aim of this study was to compare outcomes following fractured neck of femur (FNOF) in patients with and without hyponatremia and was facilitated by the population health datasets in Tayside obtained from the Health Informatics Centre, University of Dundee. Length of stay, readmissions and deaths were the main variables of interest. Also examined were the time from admission to surgery, the length of hospitalisation for recuperation/convalescence and the proportion of patients for whom normal serum was attained at discharge.

Patients were included in this study if between 1/1/2000 and 28/6/2011, they were admitted to hospital in Tayside, Scotland with FNOF. Individuals were diagnosed as having hyponatremia if, at the time of admission, there was a specific diagnosis of the condition or the first serum sodium recorded following admission was less than 125 mEq/l. Electronic databases containing primary and secondary care information were linked using a unique identifier for each patient. χ² methods, independent t-tests and non-parametric methods were used to compare baseline characteristics. Cox regression was used to estimate the unadjusted and adjusted hazard ratio (HR) of readmission and death associated with hyponatremia. Binary logistic regression was used to determine the effect size (odds ratio) of hyponatremia and other independent variables on binary outcomes.

Hyponatremia was associated with longer hospitalisation at index admission (30 vs 17 days, P=0.003) and increased risk of readmission for any reason (adjusted HR 1.60 (1.22, 2.11), P=0.001). There was some evidence of an increased risk of readmission for FNOF (adjusted HR 1.68 (0.99, 2.83), P=0.052) but no increased risk of death (adjusted HR 0.95 (0.75, 1.21), P=0.661).

Hyponatremia in patients with FNOF is a marker of longer hospitalisation and increased risk of readmission.

Declaration of funding: This work was supported by funding from Otsuka Pharmaceuticals UK Ltd.