Early identification of hypovolemia using total body resistance measurements in long-term care facility residents.

BACKGROUND: Clinical management of fluid imbalance continues to be a major challenge in the long-term care industry. A proactive method of recognizing hypovolemia (reduced total body fluid) in its early stages is greatly needed. OBJECTIVES: The goals of this research were 3-fold: (1) to determine the mean total body resistance(TBR) of an unmatched population of long-term care facility (LTCF) residents and correlate increased levels of TBR with evidence of fluid imbalance; (2) to identify patients at risk for hypovolemia by using TBR measurements as an objective guide; and (3) to suggest nursing practices designed to increase hydration in LTCF residents. METHODS: Two pairs of electrocardiograph-type electrodes were placed on the right humeral-carpal junction and at the level of the right lateral malleolus of each patient. A 50-kHz signal was introduced to the outer electrode of each pair; the inner electrode detected variation of the resistance to the signal as a function of ionic conduction through the electrolyte content of body fluids. Resistance, reactance, and phase angle were measured. RESULTS: The medical records of patients in 26 LTCFs (17 urban, 9 rural) in north-central and east Texas were reviewed during 2001. The mean age of the 1225 study patients (754 women, 471 men) was 76 years; mean height was 165.8 cm, and mean body weight was 71.9 kg. The mean TBR (right wrist-right ankle) for men and women was 504.81 ohms. Based on this measurement and a measurement of 629 ohms in residents judged to be hypovolemic on the basis of abnormal clinical laboratory data, patients with a wrist-ankle resistance >550 ohms were considered at risk for hypovolemia and possibly clinically significant dehydration. Subsequent measurements of TBR revealed a reduction consistent with levels in the normal range. CONCLUSIONS: In these studies, TBR measurements correlated inversely with total body water and fluid compartments. Extracellular fluid compartments were found to be larger in females than in males, reflecting larger cellular mass in males. Total body resistivity was found to be higher in females than in males, which may have implications for body composition metrics. TBR provides a reference for comparison with both clinical and laboratory findings. The ability to identify LTCF residents at risk for hypovolemia, using noninvasive bedside measurements, may offer a definitive guideline for management of adequate fluid balance.