Introduction: Hyponatraemia (serum sodium < 135mMol/L) is the commonest electrolyte imbalance encountered in clinical practice. It is associated with multiple poor clinical outcomes including increased mortality, longer hospital stay, falls and fractures. Management of hyponatraemia depends crucially on accurate determination of volaemic (hydration) status but this is notoriously challenging to measure, especially in older people. Bioelectrical impedance analysis (BIA) provides a quick, validated and inexpensive means of determining total body water (TBW), but its' clinical utility in determining volaemic status in hyponatraemia has never been tested. The aim of this study was to assess the utility of BIA in the clinical management of hyponatraemia in elderly patients with fragility fractures (EPFF), a group at especially high risk of hyponatraemia.
Methods: A service evaluation was conducted in patients >65 years, admitted to Aberdeen Royal Infirmary with fragility fractures, with capacity to consent to participation. BIA and standard clinical examination procedures (JVP, skin turgor, mouth and axillary moistness, peripheral oedema, capillary refill time and overall impression) were performed daily throughout each participant's hospital stay. In cases of hyponatraemia, volaemic status was determined by an expert panel using clinical data (history, examination, nursing observations and laboratory tests) blinded to TBW readings. Cohen's kappa was calculated to assess the level of agreement between the expert panel and both BIA and standard clinical examination measures in determining the volaemic state of hyponatraemia.
Results: 26/33 cases of hyponatraemia had sufficient clinical information to allow determination of volaemic status by BIA. There was moderate level of agreement between BIA and the expert panel, kappa 0.52 (p < 0.001). All kappa values for standard clinical assessments of volaemic status neared zero, indicating nil to slight agreement.
Conclusion: BIA outperformed all aspects of the standard clinical examination in determining the volaemic status of hyponatraemic EPFF, suggesting it may be useful in clinical practice.