INTRODUCTION: Urea Kt/V and urea reduction ratio are the most commonly exploited parameters of dialysis adequacy. Plenty of other uremic retention solutes with a deleterious effect on morbidity and mortality of uremic patients accumulate in ESKD patients [1]. Commonly, the uremic solutes are divided into three physicochemical types [2] with the representative markers urea, indoxyl sulfate (IS), and β2-Microglobulin (B2M). Optical monitoring of the uremic marker molecules has been speculated [3]. A compact and robust optical on-line dialysis monitoring device is a step closer to automatic assessment of removal of uremic toxins in dialysis.
The aim of this study was to evaluate intradialytic on-line multicomponent reduction ratio (RR) monitoring in the spent dialysate by a novel miniaturized optical sensor during hemodialysis (HD) and hemodiafiltration (HDF) with different settings.
METHODS: Ten ESKD patients (6 male and 4 female, 60.2±16.8 years) on chronic HDF were enrolled into the study (fistula N=9, graft N=1). For each patient 5 midweek dialysis sessions (length 240min, HD: N=1, Qb=200ml/min, Qd=300ml/min, FX60; HDF: N=4, Qb≥300ml/min, Qd≥500ml/min, Vsubst≥15l, FX800 and FX1000) were included. Spent dialysate from the drain was monitored on-line by a miniaturized sensor prototype (Optofluid Technologies OÜ, Estonia). For the reference, the samples from the spent dialysate drain tube of the HD machine were taken as 7, 60, 120 and 180min after the start and at the end of the session (240min). The concentrations of urea and B2M in dialysate were determined in the clinical laboratory. Concentration of IS was determined utilizing the HPLC. RR values in relative to 7 min sample were calculated. t-test was used to determine significant differences (P≤0.05).
RESULTS: The laboratory RR values ranged from 30.7±6.9% to 66.1±8.0% for urea, from 44.6±6.7% to 79.3±7.0% for B2M, and from 16.6±9.3% to 51.2±12.3% for IS, corresponding to the time moments 60 and 240min, respectively (Fig. 1). The RR values were statistically different for all uremic solutes at different sampling times. The reason for the larger difference at the beginning of the treatment between laboratory and sensor values was relative starting point for RR calculation (7 min sample for lab and 0 min for on-line).
CONCLUSIONS: Removal rates were different for the observed uremic solutes urea, B2M and IS. Novel miniaturized optical sensor successfully carried out intradialytic on-line multicomponent RR monitoring in the spent dialysate.
[1] http://eutoxdb.odeesoft.com; [2] Duranton et al 2012; [3] Arund et al 2016
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