Asian Journal of Pediatric Nephrology

: 2019  |  Volume : 2  |  Issue : 1  |  Page : 54--55

Targeting dry weight of children on maintenance dialysis by bio-impedance analysis

Arpana Aprameya Iyengar, Anil Vasudevan 
 Department of Pediatric Nephrology, St John's Medical College Hospital, Bengaluru, Karnataka, India

Correspondence Address:
Arpana Aprameya Iyengar
Department of Pediatric Nephrology, St John's Medical College Hospital, Bengaluru - 560 034, Karnataka

How to cite this article:
Iyengar AA, Vasudevan A. Targeting dry weight of children on maintenance dialysis by bio-impedance analysis.Asian J Pediatr Nephrol 2019;2:54-55

How to cite this URL:
Iyengar AA, Vasudevan A. Targeting dry weight of children on maintenance dialysis by bio-impedance analysis. Asian J Pediatr Nephrol [serial online] 2019 [cited 2020 Aug 14 ];2:54-55
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Achieving dry weight in children on maintenance dialysis helps reduce cardiovascular morbidity and provides good assessment of nutritional status. In comparison to weight-based prescriptions for ultrafiltration which usually provide a rough estimate, bio-impedance analysis (BIA)-based prescriptions show fewer episodes of intradialytic hypotension and better quality of sessions on hemodialysis.[1],[2]

Bio-impedance vector analysis (BIVA), which is based on the length of the impedance vector and phase angle, has been used to assess both hydration and nutritional status. The vector is created using resistance (R = the opposition to flow of an alternating current through intra- and extra-cellular ionic solutions) and reactance (Xc = the capacitance produced by tissue interfaces and cell membranes) graphs that together constitute impedance (Z) and is independent of age-specific reference data.[1],[3] The longer the vector, the lower the water quantity and greater the resistance. Reference data of BIVA for healthy Indian adults have been created and compared with that of end-stage renal disease patients, with vector displacement indicating inadequate ultrafiltration and malnutrition.[4] In a study on 26 adults undergoing hemodialysis, displacement of vectors on the ellipses corresponded to adjustments made in the rate of ultrafiltration.[5]

We report a study on BIVA undertaken in children on maintenance dialysis to guide fluid removal. Following institutional ethical committee approval and after obtaining informed consent, we recruited 20 healthy children, including 11 boys, with mean ± standard deviation age of 9.6 ± 3.4 years and median (interquartile range) weight of 25.9 (22.2–31.0) kg and height of 130 (120–140) cm, to create normative data for vector analysis. A multifrequency BIA was performed with Bodystat Quadscan 4000 (version 5/12, Bodystat Ltd., Douglas, British Isles). Children were made to remain at rest in supine position for at least 10 min prior to the test. The values of Xc and R indexed to height(Ht) [R/Ht and Xc/Ht] were plotted on X axis and Y axis, respectively. The RXc plot representing BIVA was then constructed using R programming software (R core team, GNUGPLv2, The vector has three ellipses that denote the 50th, 75th, and 95th centiles (inner to outer ellipse) for readings of Xc and R among healthy controls indexed to height. Sixteen children on dialysis (14 boys), with age 12.1 ± 3.5 years, height 130 (110–140) cm, predialysis weight 21.5 (17.3–38.0) kg, and postdialysis weight 19.8 (16.9–36.3) kg, were recruited for the study. BIA was performed 30 min prior to and after terminating a hemodialysis session or within 2 h of completing 24-hr peritoneal dialysis session. Parameters of Xc and R in children prior to and after dialysis were plotted on the graph [Figure 1]. We observed shifts in vector plots of individual patients based on the amount of fluid removal. With an intent to reach values as close to the center of the normative reference ellipse, using BIVA, without hemodynamic instability, we were able to remove 0.5 (0.3–0.9) L of fluid per patient per se ssion of hemodialysis in addition to a weight-based ultrafiltration rate prescription of 1.3 (0.5–2.0) L.{Figure 1}

We conclude that creation of BIVA for children on dialysis, based on reference ellipses of healthy controls, can be a noninvasive bedside tool to prescribe ultrafiltration and achieve dry weight.

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