Assessment of low-intake dehydration in hospitalised older people and the role of Bioelectrical Impedance Spectroscopy

Abstract

Background: Older people are susceptible to low-intake dehydration, which is often not recognised and can result in significant morbidity through falls, constipation, delirium, respiratory and urinary tract disorders, and even death. Identifying low-intake dehydration at hospital admissions is challenging, leading to treatment delays and poor outcomes.

Aims: To examine the factors underlying the identification of low-intake dehydration in older people admitted to Medicine for Older People (MOP) wards at University Hospital Southampton NHS Trust and to explore the feasibility of performing a study whereby bioelectrical impedance analysis (BIA) might be used alongside existing hydration risk screening tools in identifying low-intake dehydration in older people admitted to hospital.

Methodology: A narrative review of the role of water in the body and the consequences of dehydration was carried out. This was followed by a sequential explanatory mixed-methods study involving quantitative service evaluation of recognition of dehydration in MOP wards and qualitative staff interviews to determine barriers and facilitators of hydration care and examine the factors influencing the routine assessment and diagnosis of dehydration in MOP wards. This led to a systematic review of the literature on the role of BIA in detecting low-intake dehydration. Finally, a study was conducted to examine the feasibility of conducting measurements of hydration status in hospitalised older patients using the existing hospital screening tool for dehydration and BIA measurements.

Results: Most older patients admitted were at moderate to severe risk of developing dehydration. The service evaluation of hydration care provision showed good compliance with completing the initial hydration assessment. However, follow-up of patients at severe risk via 24-hour fluid balance charts needed improvement. Nursing and medical staff were aware of the importance of assessing hydration status but faced challenges in the diagnosis and management of dehydration. The proposed design for a study exploring the concurrent validity of the current screening tools and bedside measurements of BIA, its implementation and conduct was shown to be both feasible and acceptable to patients and staff and generated high-quality impedance measurements at the bedside alongside routine clinical care. Clinical demographics and directly measured impedance values of resistance, reactance, phase angle and impedance ratio were obtained in 25 patients reflected both age and hydration state but did not significantly correlate with risk categorisation of dehydration based on the established screening tools.

Conclusion: Identifying older people admitted to hospitals who are at risk of or have low-intake dehydration requires continued vigilance, adherence to screening and assessment, and continued oversight within ordered systems and processes. Continued service improvement and staff training are needed, together with objective measures of hydration status, such as bioelectrical impedance, which may be used to improve clinical decision-making and care. Further studies are required to determine the reliability and validity of BIA in detecting low-intake dehydration compared with pre-existing objective measures such as serum osmolality, as well as its cost-effectiveness and evaluability in clinical practice.