Use of Foot Veins to Monitor Hydration in the Elderly

Abstract

To the Editor: Dehydration is a common problem in extended care facilities. The accepted signs of dehydration may be absent or misinterpreted because of the effects of normal aging. Often dehydration does not become apparent until the patient presents with another concomitant illness, such as urinary tract infection or pneumonia.1, 2 To complicate the evidence further, serum sodium, blood urea nitrogen/creatinine ratios, and serum osmolality are highly variable between elderly subjects. Unless frequent baseline measurements are obtained, these values are difficult to evaluate.3 An age-appropriate assessment of dehydration is desperately needed to help caregivers identify dehydration early. Bioelectrical impedance analysis (BIA) may be useful in monitoring fluid balance. BIA is based on the principle that fat-free mass, which contains more water, has a much greater conductivity than fat. BIA has been validated and its usefulness in relation to monitoring change over time confirmed.4 Recently, BIA was compared with the criterion standard of isotopic tracers for total body water (TBW) and extracellular water (ECW) in 169 subjects with wide ranges of hydration. BIA measurements were within 3% of actual amounts of TBW and ECW.5 Rate and degree of filling of small veins in the foot has been suggested as a physical measure of hydration. Using this measure, a dorsal foot vein is occluded by finger pressure at a distal point and emptied by stroking proximally. The pressure is then released, and rate and degree of return of blood is observed and rated.6, 7 This measure has not been validated. A study was conducted with 51 nursing home residents (mean age 83.4) to examine the change in physical assessment signs and the change in bedside BIA measurements of TBW during a program designed to improve hydration in elderly residents of a nursing home. The hydration program consisted of the following components: a caregiver knowledgeable in techniques for administration of fluids, an individualized plan of care incorporating the most-effective techniques to administer fluids, a colorful beverage cart with colorful pitchers and glasses to enhance interest in drinking, and at least four different choices, with beverages varied daily. Research has indicated that average daily fluid intake for nursing home residents is only 1,000 mL.1 A goal was set for residents to consume an additional 8 ounces of a beverage of their choice mid-morning and mid-afternoon. With this approach, their fluid intake should be approximately 1,500 mL. Data collection occurred weekly for 9 weeks: 2 weeks prehydration, 5 weeks hydration, and 2 weeks posthydration. Each week, BIA measurements and physical assessment measurements were obtained. Physical assessment measurements included weight, pulse, appearance of eyes, tongue dryness, number of tongue furrows, dryness of mucus membranes, skin turgor on the forehead, and degree of vein filling of the foot. Vein filling was rated as follows: 0=blood returned instantly (vein filled); 1=direction of blood flow easily observed (vein filled); 2=blood returned slowly, vein requires 3 seconds to fill; and 3=vein visible initially, remained collapsed after emptying. Mean prehydration, mean hydration, and mean posthydration scores were analyzed using repeated measures analysis of variance. There was a significant increase in TBW with the provision of two additional 8-oz glasses of fluid (Table 1) and a significant decline in TBW after the hydration program was stopped. Degree of vein filling was the only measure that followed the same pattern as the BIA measurements, with improvement in degree of vein filling (as reflected in a lower rating and a lower mean) during the hydration period. Results indicated that most physical assessment indicators commonly used to track change in hydration were not useful in this group of nursing home residents. BIA measurements and degree of vein filling were the only useful measurements. Physiologically, it seems reasonable that observance of rapidity and degree of filling of veins would reflect volume of fluid in elders. By far the greatest portion of ECW is contained in systemic veins (64%). Veins basically serve as the reservoir for body fluid, and their condition should reflect the state of TBW.7 It is a simple measure that can be performed in any setting. Further investigation is needed to validate this measure. Various medical conditions may affect the measurement. If more evidence supports the use of foot veins to monitor level of hydration, caregivers in any setting could easily and quickly identify those who need increased fluid intake.