Measurement of fluid shift in CAPD patients using segmental bioelectrical impedance analysis

Abstract

Objective: To determine, using segmental bioelectrical impedance analysis (BIA), the characteristics of fluid shift of each body segment in continuous ambulatory peritoneal dialysis (CAPD) patients during and after peritoneal dialysis (PD) solution exchange. Design: Observational study with repeated measurements of bioelectrical impedance, which is inversely related to tissue fluid content. Patients: Thirteen clinically stable CAPD patients. Methods: Bioelectrical impedance was measured at frequencies of 5, 50, 250, and 500 kHz in each body segment four times: (1) before and (2) after drainage of dialysate, and (3) at 1 hour and (4) at 2 hours after exchange of new 1.5% dextrose PD solution. Results: Impedance of both arms was significantly increased at 1 hour post exchange at all frequencies. In the trunk, impedance at all frequencies increased significantly after drainage, decreased significantly at 1 hour post exchange, and then increased again for the next hour without significance. Impedance of both legs showed a decreasing tendency at all frequencies during and after exchange. Net calculated water volume changes between the time before drainage and 2 hours post exchange were -0.5 L in the trunk, -0.25 L in both arms, +0.47 L in both legs, -0.28 L in total. The change in body weight between the time before drainage and 2 hours post exchange was -0.21 kg, on average, and significantly correlated with total net calculated water volume change (p = 0.009). Conclusions: Each body segment of the CAPD patient has its own characteristic pattern of fluid shift in response to PD solution exchange or dwell. Segmental BIA may be a useful tool for understanding the physiological changes in fluid shift in CAPD patients.