• James Edward Rudge and Daniel Kim.
• City Hospital, Sandwell and West Birmingham Hospitals NHS Trust - Postgraduate Centre, Birmingham, UK.
• Age Ageing. 2014 Nov 1; 43 (6): 821-6.

Backgroundhyponatraemia in orthopaedic patients is common but has been poorly investigated following surgery for traumatic hip fracture. The aims of this study were to define the incidence of new-onset post-operative hyponatraemia and to investigate associations between hyponatraemia and patient demographics, medication use and duration of hospital stay.Methodsall patients admitted to the Orthopaedic Unit for hip surgery following trauma in 2012 were retrospectively reviewed. Patients who developed post-operative hyponatraemia within 10 days of surgery were compared with patients who remained normonatraemic pre- and post-operatively.Resultsa total of 254 patients were included. Overall, this study identified a significant (P =< 0.001) mean post-operative drop in serum sodium of 1.8 mmol/l (95% CI: 1.3-2.3%) compared with pre-operative levels. The incidence of moderate (<135 mmol/l) and severe (<130 mmol/l) post-operative hyponatraemia was 27% (95% CI: 21.7-32.5%) and 9% (95% CI: 5.7-12.8%), respectively. Statistical analysis revealed significant associations between the development of post-operative hyponatraemia and: (i) proton pump inhibitor use, (ii) selective serotonin re-uptake inhibitor use and (iii) increasing number of medications. Length of hospital stay was significantly increased in patients with moderate post-operative hyponatraemia compared with normonatraemic patients (30 versus 21 days; P =< 0.001). The incidence of new-onset post-operative hyponatraemia was not significantly increased by ethnicity, gender, fracture type, functional status or operative procedure.Conclusionhyponatraemia after surgery for hip fracture is common and results in longer hospital stay. This study provides evidence that an average post-operative drop in serum sodium concentration should be expected in this patient group. Moreover, patients taking SSRI or PPI medications may be at increased risk of post-operative hyponatraemia.© The Author 2014. Published by Oxford University Press on behalf of the British Geriatrics Society. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

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