Optical dialysis adequacy sensor: contribution of chromophores to the ultra violet absorbance in the spent dialysate

Several on-line methods have been developed to standardize the assessment of dialysis adequacy. Earlier studies have demonstrated that on-line monitoring of total ultra violet (UV) absorbance in spent dialysate can be utilized to follow continuously a single hemodialysis session. The aim of this study was to investigate the contribution of different compounds, acting as chromophores, to the UV-absorbance in the spent dialysate in order to explain origin of the cumulative and integrated UV-absorbance measured by the optical dialysis adequacy sensor. Four uremic patients, during 12 hemodialysis treatments, were followed by the optical dialysis adequacy sensor using the wavelength of 280 mn. The dialysate samples were taken and analyzed using reversed phase high performance liquid chromatography (HPLC). The total number of detected peaks from the HPLC gradient separation profiles measured at the wavelength 280 nm for the samples collected 10 mm after the start of hemodialysis (MeanplusmnSD) was 38plusmn6. The relative contribution from the area of 10 main peaks to the total area of all detected peaks in percentage was 91.01plusmn2.52 %. The optical dialysis adequacy sensor provides continuous, on-line hemodialysis measurements and may immediately identify and alert to any deviations in the dialysis. Our study indicates that there exists a number of prevalent compounds that are the main cause of the cumulative and integrated UV- absorbance