Jürgen Arund

Do Only Small Uremic Toxins, Chromophores, Contribute to the Online Dialysis Dose Monitoring by UV Absorbance?

The aim of this work was to evaluate the contributions of the main chromophores to the total UV absorbance of the spent dialysate and to assess removal dynamics of these solutes during optical on-line dialysis dose monitoring. High performance chromatography was used to separate and quantify UV-absorbing solutes in the spent dialysate sampled at the start and at the end of dialysis sessions. Chromatograms were monitored at 210, 254 and 280 nm routinely and full absorption spectra were registered between 200 and 400 nm. Nearly 95% of UV absorbance originates from solutes with high removal ratio, such as uric acid. The contributions of different solute groups vary at different wavelengths and there are dynamical changes in contributions during the single dialysis session. However, large standard deviation of the average contribution values within a series of sessions indicates remarkable differences between individual treatments. A noteworthy contribution of Paracetamol and its metabolites to the total UV absorbance was determined at all three wavelengths. Contribution of slowly dialyzed uremic solutes, such as indoxyl sulfate, was negligible.

Quantification of Indoxyl Sulphate in the Spent Dialysate Using Fluorescence Spectra

The aim of this study was to investigate the possibility to determine the amount of Indoxyl Sulphate (IS) in the spent dialysate using fluorescence spectra.

Beta2-microglobulin Measurements in the Spent Dialysate Using Fluorescence Spectra

The aim of this study was to measure the concentration of beta2-microglobulin (B2M) in the spent dialysate using optical method utilizing fluorescence spectra of the spent dialysate.

Is Fluorescence Valid to Monitor Removal of Protein Bound Uremic Solutes in Dialysis

The aim of this study was to evaluate the contribution and removal dynamics of the main fluorophores during dialysis by analyzing the spent dialysate samples to prove the hypothesis whether the fluorescence of spent dialysate can be utilized for monitoring removal of any of the protein bound uremic solute. A high performance liquid chromatography system was used to separate and quantify fluorophoric solutes in the spent dialysate sampled at the start and the end of 99 dialysis sessions, including 57 hemodialysis and 42 hemodiafiltration treatments. Fluorescence was acquired at excitation 280 nm and emission 360 nm. The main fluorophores found in samples were identified as indole derivatives: tryptophan, indoxyl glucuronide, indoxyl sulfate, 5-hydroxy-indoleacetic acid, indoleacetyl glutamine, and indoleacetic acid. The highest contribution (35 ± 11%) was found to arise from indoxyl sulfate. Strong correlation between contribution values at the start and end of dialysis (R2 = 0.90) indicated to the stable contribution during the course of the dialysis. The reduction ratio of indoxyl sulfate was very close to the decrease of the total fluorescence signal of the spent dialysate (49 ± 14% vs 51 ± 13% respectively, P = 0.30, N = 99) and there was strong correlation between these reduction ratio values (R2 = 0.86). On-line fluorescence measurements were carried out to illustrate the technological possibility for real-time dialysis fluorescence monitoring reflecting the removal of the main fluorophores from blood into spent dialysate. In summary, since a predominant part of the fluorescence signal at excitation 280 nm and emission 360 nm in the spent dialysate originates from protein bound derivatives of indoles, metabolites of tryptophan and indole, the fluorescence signal at this wavelength region has high potential to be utilized for monitoring the removal of slowly dialyzed uremic toxin indoxyl sulfate.

Estimation of removed uremic toxin indoxyl sulphate during hemodialysis by using optical data of the spent dialysate

The aim of this study was to explore the possibility to determine the amount of total removed Indoxyl Sulphate (TR_IS) during dialysis session, an optical method utilizing absorbance and fluorescence spectral data of the spent dialysate was used. Eight uremic patients from Linköping, Sweden and 10 from Tallinn, Estonia, were studied during dialysis treatments. Dialysate samples were taken during each treatment and analyzed at a laboratory. Fluorescence and absorbance spectra of the spent dialysate were measured with spectrofluorophotometer and spectrophotometer. The spectral values were transformed into IS concentration using multiple linear regression model from the total material noted as optical method (Opt). IS concentration was estimated using high-performance liquid chromatography (HPLC) method as a reference. TR_IS values were calculated. Achieved results were compared regarding mean values and SD and collated with the amount of total removed urea value (TR_Urea) for the same dialysis procedures. Mean TR value±SD (mg) for urea was 28 947±9 241; TR for IS was 151.4±87.3 estimated by HPLC and 149.4±84.9 estimated by Opt. The TR_IS values were not significantly different (p≤0.05). This study indicates, that it is possible to estimate TR_IS using only spectral values of the spent dialysate and the parameter can be used for quantifying the elimination of protein bound uremic toxins during the dialysis procedure.

New Optical Method for Estimation of Protein Bound Uremic Toxins Elimination

The aim of this study was to investigate the possibility to determine the amount of removed Indoxyl Sulphate (IS) during dialysis session. An optical method using fluorescence spectra was used.

Paracetamol Interference in Uric Acid Levels in Uremic Patients Revealed by Monitoring Spent Dialysate

The aim of this study was to assess removal dynamics of paracetamol (PAR), as an extraordinary chromophore in spent dialysate, upon the optical monitoring of dialysis of end-stage renal disease patients with inflammation complications. Seven dialysis sessions of different patients were followed to whom PAR was used as a pain reliever or antipyretic. Spent dialysate was sampled hourly and analyzed using HPLC with MS/MS and UV detection. Quantitative calculations were made on the basis of the peak areas on the chromatograms at 280 nm for uric acid (UA) and 254 nm for PAR and its metabolites (PAR-M). Peaks of UA, PAR, PAR-glucuronide, and PAR-sulphate were identified on the basis of specific mass spectra. Removal of PAR was found to be proportional to that of uric acid if intake of the drug by patient occurred half a day before dialysis. But disturbances of the UV-absorbance curves at 280 nm were observed related to rise of UA concentration in spent dialysate when PAR was taken by patients in the course of dialysis. The mechanism of such relation remains unknown. It was concluded that possible benefits and risks of treatment of uremic patients with paracetamol-containing drugs may need to be reassessed.

Removal Estimation of Uremic CVD Marker Phosphate in Dialysis Using Spectrophoto-and Fluorimetrical Signals

The high phosphate (P) level is considered a key player in the genesis and progression of vascular calcification in chronic kidney disease. Therefore, it is necessary to assure the sufficient removal of this uremic retention solute during dialysis. The aim of this study was to develop models on the basis of optical signals of a particular biofluid - the spent dialysate, a waste product of kidney replacement therapy, to estimate concentrations and removal of phosphate. Eleven uremic patients from Tallinn, Estonia, were studied during altogether 42 hemodialysis treatments. Dialysate samples were collected during each treatment and analyzed at a laboratory. Ultraviolet absorbance and fluorescence spectra of the spent dialysate samples were measured. The spectral values were transformed into phosphate concentration using multiple linear regression models. Three different models were created, one used UV- absorbance values, second fluorescence values and third combined both signals. Mean phosphate concentration (mmol/L) measured in the lab was 0.299±0.141, and 0.298±0.114, 0.296±0.115, and 0.296±0.118 estimated by UV, fluorescence and combined model, respectively.

Optical measurement of 4-pyridoxic acid in the spent dialysate: Algorithm Development

The aim of this study was to develop an algorithm suitable for the estimation of 4-pyridoxic acid (4PA) concentration removed during dialysis through fluorescence measurements in spent dialysate. 4PA is the major urinary catabolite of vitamin B-6 (B6), that is regularly injected to dialysis patients. 4PA could be used to estimate B6 nutritional status of the patients. For the study 10 hemodialysis patients during 40 dialysis sessions were studied. Full fluorescence spectra of spent dialysates were recorded with the spectrofluorophotometer RF-5301 by Shimadzu (Kyoto, Japan) and 4-pyridoxic acid concentrations were measured with HPLC system. Two single wavelength models were developed were correlation coefficients for Ex/Em 320/430 nm were 0.931 and 0.853 and for Ex/Em 310/460 nm were 0.944 and 0.931 for calibration and validation set, respectively. In summary, 4PA concentration can be estimated through fluorescence measurements from spent dialysate.

4-Pyridoxic Acid in the Spent Dialysate: Contribution to Fluorescence and Optical Monitoring.

Aim In this work we estimated the contribution of the fluorescence of 4-pyridoxic acid (4-PA) to the total fluorescence of spent dialysate with the aim of evaluating the on-line monitoring of removal of this vitamin B-6 metabolite from the blood of patients with end-stage renal disease (ESRD). Methods Spectrofluorometric analysis of spent dialysate, collected from hemodialysis and hemodiafiltration sessions of 10 patients receiving regularly pyridoxine injections after dialysis treatment, was performed in the range of Ex/Em 220–500 nm. 4-PA in dialysate samples was identified and quantified using HPLC with fluorescent and MS/MS detection. Results Averaged HPLC chromatogram of spent dialysate had many peaks in the wavelength region of Ex320/Em430 nm where 4-PA was the highest peak with contribution of 42.2±17.0% at the beginning and 47.7±18.0% in the end of the dialysis. High correlation (R = 0.88–0.95) between 4-PA concentration and fluorescence intensity of spent dialysate was found in the region of Ex310-330/Em415-500 nm, respectively. Conclusion 4-PA elimination from the blood of ESRD patients can be potentially followed using monitoring of the fluorescence of the spent dialysate during dialysis treatments.