MO662EFFECT OF ARTERIOVENOUS VASCULAR ACCESS ON BIOIMPEDANCE MEASUREMENTS IN HEMODIALYSIS PATIENTS

Abstract

Abstract Background and Aims Fluid management remains a major problem in hemodialysis (HD) patients, partly because of the lack of objective assessment methods. Many methods have been proposed to estimate the fluid status in HD patients and bioimpedance has established as one of the most popular clinical tools. Resistance to alternate current was found to be lower in the arteriovenous (AV) access-bearing side compared with the non-access side in post-HD bioimpedance measurements. We hypothesized this difference between access and non-access sides can be seen in both pre- and post-HD measurements of arms and whole body. The aim of the study was to investigate whether this variation between access and non-access sides could affect single-side whole body measurements. Method Pre- and post-HD bioimpedance measurements with two 8-point devices (InBody 770 and Seca mBCA 514) were performed in 11 HD patients with functioning AV access in the arm (8 male, pre-HD 75.4 ± 13.6 kg, post-HD 72.8 ± 13.5 kg). Values of resistance at 5 kHz (R5) in the arm and whole body (R5 of arm + trunk + leg on the same side) were extracted. Whole-body extracellular water (ECW) was calculated using whole-body R5 by the Xitron equation* to evaluate how measuring only one side of the body can affect the fluid volume calculation. Results The R5 of the arm on the access side was lower compared with the non-access side both pre- and post-HD (P < 0.01), measured by InBody. The same was seen with the Seca but did not reach statistical significance (Table 1). The estimated whole-body ECW was higher on the access side for InBody (P < 0.01). With Seca, the same trend was seen but remained non-significant. While the difference in ECW between both arms reported by InBody was small, the impact on calculated whole-body ECW was much larger with a difference between sides of 0.50 ± 0.82 L pre HD and 0.55 ± 0.81 L post HD. Conclusion InBody appears to pick up the difference in fluid status between the access and non-access side with greater precision than Seca. The large contribution of the arm to whole-body resistance amplifies the impact of the presence of an AV access on whole-body ECW estimations based on single-side wrist-to-ankle bioimpedance measurements. Eight-point bioimpedance devices (like the tested InBody and Seca) measure both sides of the body, so, choice of measurement side does not enter the picture.