Urea Rebound Assessment Based on UV Absorbance in Spent Dialysate

Abstract

The aim of the study was to examine the possibility of post-dialysis urea rebound assessment using UV-absorbance measurements in spent dialysate. Twenty-six patients on chronic three-times-a-week hemodialysis (HD) were studied in two separate studies. Double-beam spectrophotometer was used for the determination of UV absorbance in the collected spent dialysate samples. Also, on-line UV absorbance was monitored. The equilibrium concentration (C-eq) of urea at the end of the rebound phase was calculated based on urea concentration in blood and dialysate and UV absorbance in spent dialysate. Based on C-eq, urea rebound was expressed relative to urea concentration at the end of HD (R-1) and relative to the decrease in urea concentration during HD (R-2). Estimates based on UV-absorbance values in spent dialysate (R-1_a, R-2_a) slightly over assess postdialysis rebound compared with results based on the blood sample drawn 30 min after HD (R-1_30post, R-2_30post), but R-1_a and R-2_a presented greater consistency and accuracy compared with the estimates based on the intradialytic blood sample (R-1_b, R-2_b). In summary, the results show that it is possible to assess postdialysis urea rebound in blood based on UV-absorbance measurements in spent dialysate.</p