Bioelectrical impedance analysis is more accurate than clinical examination in determining the volaemic status of elderly patients with fragility fracture and hyponatraemia.

OBJECTIVES: Management of hyponatraemia depends crucially on accurate determination of volaemic (hydration) status but this is notoriously challenging to measure in older people. Bioelectrical impedance analysis (BIA) provides a validated means of determining total body water (TBW), but its clinical utility in determining volaemic status in hyponatraemia has never been tested. This study assessed the utility of BIA in the clinical management of hyponatraemia in elderly patients with fragility fractures (EPFF), a group at high risk of hyponatraemia. DESIGN: Prospective observational study of consenting patients ≥65 years with fragility fractures (N=127). SETTING: University teaching hospital in Scotland. PARTICIPANTS: Patients ≥665 years with fragility fractures with capacity to consent to participation. MEASUREMENTS: BIA and standard clinical examination procedures (jugular venous distension, skin turgor, mouth and axillary moistness, peripheral oedema, capillary refill time, overall impression) were performed daily throughout each participant's hospital stay. Volaemic status of hyponatraemia 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 (79%) 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<.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.

Volaemic assessment of the elderly hyponatraemic patient: reliability of clinical assessment and validation of bioelectrical impedance analysis.

BACKGROUND: Hyponatraemia is the commonest electrolyte disturbance of hospital inpatients. Assessment of volaemic status is an important part of diagnosis and management. AIM: To determine reliability of clinical assessment of volaemic state by assessing inter-observer variability of clinical measures of volaemic state. To assess validity of bioelectrical impedance analysis as a tool to measure total body water in elderly hyponatraemic patients. DESIGN: Observational study conducted in a Department of Medicine for the Elderly. METHODS: Hospital inpatients >65 years old (n=22) with serum sodium concentration <130 mmol/l were included. Two assessors determined volaemic state on two occasions 72 h apart. Level of agreement between observers was determined on each occasion. Total body water estimation was undertaken with bioelectrical impedance analysis and measurement of dilution of deuterium oxide. Correlation between these two measures was then analysed. RESULTS: Cohen's κ for agreement between two observers for overall assessment of volaemic state was 0.59 (P<0.01). Values for agreement between individual clinical markers of volaemic state ranged between 0.16 and 0.45. Pearson correlation coefficient (r) for correlation between estimation of total body water undertaken by bioelectrical impedance analysis and by measurement of dilution of deuterium oxide was 0.69 (P<0.001). CONCLUSION: There was moderate inter-observer agreement of overall clinical volaemic assessment of elderly hyponatraemic patients. Total body water estimation by bioelectrical impedance analysis correlates well with estimation by measurement of dilution of deuterium oxide, providing a potentially useful tool to improve the management of the elderly hyponatraemic patient.