Aetiology of hyponatraemia after hip fracture

Abstract

In this study, we report the prevalence and aetiology of hyponatraemia after surgery for hip fracture. We conducted a retrospective analysis of 144 consecutive patients who underwent surgery after sustaining a hip fracture. Data were collected from medical case records, operative notes and electrolyte results. Univariate and logistic regression analysis was conducted in order to identify significant independent risk factors for the development of hyponatraemia. Mild hyponatraemia was relatively common affecting 19 % (28/144) of patients pre-operatively and 28 % (40/144) post-operatively. However, moderate/severe hyponatraemia (plasma sodium concentration <130 mmol/l) was uncommon, affecting 1 % (2/144) of patients at the time of admission and 6 % (9/144) of patients post-operatively. Univariate analysis identified: female gender, pre-operative hyponatraemia, hypotonic fluid administration and thiazide diuretic use as being associated with the development of post-operative hyponatraemia. Age had no statistically significant association. Logistic regression analysis identified female gender, pre-operative hyponatraemia and hypotonic fluid administration being significant, independent risk factors for the development of hyponatraemia. Age and thiazide diuretics both had positive risk associations; however, these were not statistically significant. Mild hyponatraemia is a common finding in hip fracture patients; however, more severe cases are relatively rare. Pre-operative hyponatraemia and hypotonic fluid administration were the only modifiable risk factors identified.