Screening and identification of dehydration in older people admitted to a geriatric and rehabilitation unit

The diagnosis of dehydration in the older person admitted to hospital has been associated with increased morbidity and mortality. In spite of the high US hospital mortality and morbidity rates associated with dehydration (although presumably not the only contributing factor), no standardised or validated approach to assess or easily screen for dehydration in the hospital setting is reported in the international literature. Therefore, a series of studies was undertaken to assess the extent of this, and to identify other gaps in the current literature. The first study estimated the dehydration prevalence amongst older people upon admission to geriatric and rehabilitation unit in the Australian setting to estimate the morbidity burden in the Australian context. The second study assessed the application of dilution and bio-electrical impedance (BIA) techniques as alternative means to assess dehydration in the clinical setting. The third study undertook to validate against total body water the parameters required to confirm dehydration and to identify those that contribute little to discrimination. The final study integrated the information from the first two studies to identify a clinically practical, sensitive and specific screen suitable for the identification of those at risk of dehydration in a geriatric and rehabilitation unit. Older people aged 60 years or over admitted to the Geriatric and Rehabilitation Unit (GARU) of a tertiary teaching hospital in Brisbane. Australia, were eligible for participation in the study. Individuals were excluded if: involuntarily admitted, informed consent was not obtained, younger than 60 years or fitted with a pacemaker (due to contraindication with the use of BIA). Of 82 GARU participants approached, 43 fulfilled the inclusion criteria and consented, 21 declined and 18 were ineligible. Thirty-five (35) of the 43 were able to be involved in the assessment of prevalence. The studies in this thesis provide original insights into dehydration including prevalence, body water contents, useful clinical assessment and screening parameters. Results showed that dehydration prevalence amongst older people is substantially underreported in the Australian geriatric and rehabilitation unit setting (17.1%) when compared to the reported through coding from the medical record (5.3%). The presence of dehydration has frequently been measured in healthy populations by assessing total body water loss through short-term weight change. Gold standard dilution and bio-electrical impedance techniques were used to assess body water as the assessment of dehydration by weight change has practical and ethical limitations in the clinical setting for either research or assessment applications. Gold standard dilution studies and the bio-electrical impedance technique were not confirmed to be either practical or valid alternates to assess dehydration in the clinical setting. Weight and body mass index (BMI) confounded the association between body water and dehydration. Good agreement (78-87%) of global clinical dehydration assessment (clinical assessment) was confirmed between the study's medical officer and the consultants of the Geriatric and Rehabilitation Unit (GARU) and thus become the alternate dependant variable. Although the optimal combination of parameters for clinical dehydration assessment was unable to be elucidated, clinically significant changes upon mild dehydration were more apparent with physical as opposed to biochemical parameters. BMI confounded the association between dehydration and some physical measurements, such as the drop in systolic blood pressure on standing and skin turgor. Of all the clinical assessment and screening variables explored, tongue dryness was validated and represents a practical, sensitive (64%) and specific (62%) dehydration screen suitable for use with all older people in a geriatric and rehabilitation unit setting. Dehydration was established to be more prevalent amongst older Australians admitted to hospital than previously acknowledged or identified by hospitals. The finding identifies dehydration as a significant clinical issue considering the ageing Australian population, limited health resources and the association of dehydration with increased morbidity and mortality. The validation of the simple dehydration screen will contribute to the identification and treatment of dehydration. Although the highest sensitivity and specificity is always desired for screening, it is not always achieved. Moderate sensitivity results in more people being identified at risk by the screen than confirmed to be dehydrated through clinical assessment. Moderate specificity results in the screen's failure to identify those who would be clinically assessed with dehydration. Moderate sensitivity and specificity necessitates the assessment of more people than those with the condition and results in other people with the condition of interest not being identified. Each situation is reduced with increasing levels of sensitivity and specificity. A valid and simple dehydration screen provides future opportunities to confirm improved clinical (prevent adverse events, improve or stabilise disease), cost (reduce intensity of care, hospital stay) and client (death, disability) outcomes as a result of improved identification and timely and appropriate treatment. New insights are provided into individual clinical assessment measures as well as valid and reliable screening. A number of recommendations and future dehydration studies are discussed. The key recommendation for future studies is to discern between intracellular and intravascular volume depletion to enable investigation of an homogenous sample. Further studies are needed to also establish optimal dehydration prevention methods (e.g. awareness and positioning of fluids, beverage carts) and provide evidence that hydration support enhances primary (e.g. morbidity and mortality) and secondary (e.g. cognitive or functional measures, quality of life) health outcomes. Through responsive systems in health delivery, dehydration amongst older hospitalised people can be identified, better managed if present, and avoided with suitable treatment.