ReviewUnderstanding Clinical Dehydration and Its Treatment
Section snippets
The Regulation of Water Metabolism
Water plays a key role in maintaining multiple physiological functions (Table 1). Water comprises 55% to 65% of body mass. Two thirds of the water in the body is intracellular, predominantly in lean tissue. Of the remaining one third of body water that is extracellular, only 25% is intravascular, representing a mere 8% of total body water. With aging, there is a decline in total body water, in both the extracellular and intracellular fluid volume.3, 4 This decline in total body water and the
Definition
Classically, the medical literature has distinguished 2 forms of total body water fluid loss: (1) dehydration, which refers to a loss of body water mainly from the intracellular compartments, and (2) volume depletion, referring to a loss of extracellular fluid clinically affecting the vascular tree and interstitial compartment.17, 18 While physiologically this makes eminent sense, most clinicians tend to use the term dehydration for any loss of total body water. For this reason, we believe it
Epidemiology
The studies examining the presence of dehydration are confounded by imprecise diagnoses and varying study methodologies. Miller et al21 in a study of older African Americans (mean age 79.7 years) living in the community found an elevated BUN/creatinine ratio in 10% and an elevated sodium level in only 1%. They identified persons who were depressed and those who had impaired function as having increased risk for dehydration. Dehydrated individuals performed poorly on timed tests, one leg stand,
Dehydration and Delirium
Recently, it has been suggested that the assessment of mental status should be the sixth vital sign.37 It is well accepted that dehydration commonly precipitates delirium.38, 39 Persons in nursing homes with agitated or aggressive behavior are more likely to have anorexia, weight loss, and dehydration.40 Dehydration and infections are major causes of acute confusion in nursing homes.41
A general schema of the progressive effects of variable degrees of dehydration on behavior has been suggested:
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Identifying Dehydration
Clinical symptoms and signs of dehydration generally have poor sensitivity and specificity.44 This requires a high index of suspicion to make the diagnosis. Chassagne et al30 identified orthostasis, decreased skin turgor (subclavian and forearm), tachycardia, dry oral mucosa, and recent change in consciousness (delirium) as factors associated with dehydration in the nursing home. However, none of these factors were diagnostic. Skin turgor is not reliable because of the loss of subcutaneous
Management of Dehydration
Recognizing the difficulty of diagnosing dehydration, that it is typically due to underlying disease processes (or to excessive diuresis), and that it can develop very rapidly, it is essential that facilities are routinely vigilant about fluid maintenance. This requires increasing the role of certified nursing assistants in risk assessment and making dehydration part of nursing's daily checklist. Such vigilance includes increased awareness of risk factors for dehydration, eg, fever, hot
Subcutaneous Infusion
Recently, for persons with mild to moderate dehydration, hypodermoclysis has reemerged as an option for hydrating persons in the nursing home and at home.
Candidates for subcutaneous infusion include persons with signs of mild to moderate dehydration. Subcutaneous infusion is not appropriate for persons who have severe dehydration requiring hospitalization, manifest or imminent shock or hypotension, need for administration of a parenteral pharmacological agent, severe heart failure, acute
Conclusion
Dehydration is common in older persons and is associated with poor outcomes including increased mortality and an adverse effect on quality of life. Dehydration occurs because physiological changes associated with aging interact with a variety of disease processes. Dehydration is rarely due to neglect. Older persons fail to recognize the need to drink more in response to fluid loss. Older persons have an increased risk of dehydration, despite the availability of fluids, because of impaired
Acknowledgments
The formation of The Dehydration Council was funded by an unrestricted educational grant from Baxter, Inc. to Boomer Educational Consultants. The process included a review of the literature and an original 2-day meeting at which the major themes were developed. The manuscript was then developed and circulated electronically to all Council members and multiple changes were made based on suggestions of the members. A final manuscript was then circulated and a Web conference was held to reach
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