David F Keane1, Elizabeth Lindley. 1. Departments of Medical Physics and Renal Medicine, Leeds Teaching Hospitals NHS Trust, Leeds, UK.
Abstract
BACKGROUND: The body composition monitor (BCM) provides an objective assessment of fluid status, which has been shown to improve outcomes in patients undergoing haemodialysis. The models used by the BCM were developed and validated using standard wrist-to-ankle bioimpedance measurements, made between electrodes on the hand and foot. However, in patients with inaccessible or amputated feet it is not possible to use standard electrode configurations. OBJECTIVE: To compare hydration measurements made with 'hand-to-hand' (H-H) and 'hand-to-foot' (H-F) electrode configurations in patients with accessible feet or no amputations. METHODS: One hundred and one consecutive patients referred for a BCM measurement were recruited to have H-H measurements at the same time as the usual H-F measurement using the same height and weight. Patients with obvious localised oedema were excluded. RESULTS: Compared with H-F, H-H measurements showed a bias of -0.1 L. For 61% of patients the difference between the readings was within 0.5 L; for 81% it was within 1.0 L. CONCLUSION: The agreement between H-H and H-F measurements was close enough to encourage us to use H-H measurements in patients with inaccessible or amputated feet. Prior to amputation, height and weight are recorded. Target weight (TW) reductions are made gradually when close to normal hydration. Clinically, changes based on H-H measurements appear to be as appropriate as those using H-F. The desired hydration at TW can be established and then TW adjusted to maintain this hydration as the flesh weight fluctuates.
BACKGROUND: The body composition monitor (BCM) provides an objective assessment of fluid status, which has been shown to improve outcomes in patients undergoing haemodialysis. The models used by the BCM were developed and validated using standard wrist-to-ankle bioimpedance measurements, made between electrodes on the hand and foot. However, in patients with inaccessible or amputated feet it is not possible to use standard electrode configurations. OBJECTIVE: To compare hydration measurements made with 'hand-to-hand' (H-H) and 'hand-to-foot' (H-F) electrode configurations in patients with accessible feet or no amputations. METHODS: One hundred and one consecutive patients referred for a BCM measurement were recruited to have H-H measurements at the same time as the usual H-F measurement using the same height and weight. Patients with obvious localised oedema were excluded. RESULTS: Compared with H-F, H-H measurements showed a bias of -0.1 L. For 61% of patients the difference between the readings was within 0.5 L; for 81% it was within 1.0 L. CONCLUSION: The agreement between H-H and H-F measurements was close enough to encourage us to use H-H measurements in patients with inaccessible or amputated feet. Prior to amputation, height and weight are recorded. Target weight (TW) reductions are made gradually when close to normal hydration. Clinically, changes based on H-H measurements appear to be as appropriate as those using H-F. The desired hydration at TW can be established and then TW adjusted to maintain this hydration as the flesh weight fluctuates.