HYPONATRAEMIA AND OUTCOME FOLLOWING HIP FRACTURE

Abstract

It has been recently suggested that hyponatraemia may be a cause of significant iatrogenic harm in orthopaedic patients. In an attempt to test this theory, this observational study was done to establish the incidence of post-operative hyponatraemia following hip fracture and evaluate its correlation with outcome.

An observational study was carried out on 213 consecutive hip fracture patients. 201 patients completed the requirements of the study (Male-45, Female-156). Mean age was 80 years. Serum sodium concentrations were recorded during the first week of admission. Hyponatraemia defined as significant (Na < 130mmol/L) was identified in 9% at admission and 18% during first week of stay. Incidence of severe hyponatraemia was 3%. There were no acute complications of hyponatraemia in these patients. 78% of hyponatraemia patients had received 5% Dextrose infusion during the postoperative period as their main intravenous fluid. All hyponatraemic patients had their sodium levels restored to normal during their stay.

Long term outcome measures used were mortality, change in residential status, walking ability and use of walking aids at 4 months following fracture. There was 20% mortality at 4 months in the hyponatraemic group and it was 30% in the normal serum sodium group. However this difference was not statistically significant. Hyponatraemia did not significantly influence deterioration in residential status (p< 0. 05), walking independence (p< 0. 05) or increase of walking aids (p< 0. 05).

In hip fracture patients, hyponatraemia whilst common was not associated with a poor outcome and at the same time we did not find any evidence of lapse in the recognition and treatment of hyponatraemia in a general orthopaedic ward. However emphasis should be made to junior medical staff to avoid iatrogenic hyponatraemia by following a proper postoperative fluid regime.