Two Spent Dialysate Samples are Sufficient for Hemodialysis Efficacy Assessment

Abstract

Introduction The measure of dialysis efficacy is expressed as Kt/V value (calculated from predialysis and postdialysis blood urea concentration). The aim of this study was to assess the possibility of direct calculation of Kt/V value from two spent dialysate samples by using the regular blood-based Kt/V calculation formula with dialysate samples used as surrogates for blood samples, and to detect the most appropriate couple of dialysate samples for Kt/V estimation. Patients and Methods Fifty-two single hemodialysis treatments in 34 anuric patients on chronic bicarbonate low-flux hemodialysis were observed. Kt/V values according to Daugirdas formula from two blood samples and from two dialysate samples were calculated. Results Kt/V values calculated according to Daugirdas 2nd generation formula from blood samples (Kt/Vsp Daugirdas) were in significant correlation with all Kt/V values obtained from two spent dialysate samples. The highest correlation coefficient (r = 0.74, p & 0.001) and the least standard error of mean of the differences were found between Kt/Vsp Daugirdas and value obtained with substitution of urea concentration from dialysate samples taken 60 minutes after dialysis start and at the end of the dialysis into Daugirdas 2nd generation formula (Kt/VDCD(60)-CD(e)), which can be expressed as a equation of linear regression y = 0.47 + 0.86x. The highest correlation coefficient (r = 0.74, p & 0.001) was found between Kt/Vsp Daugirdas values equilibrated according to Daugirdas rate formula, and Kt/VDCD(60)-CD(e) value, which can also be expressed as an equation of linear regression y = 0.43 + 0.73x. Conclusion The results of this study clearly show the sufficiency of only two spent dialysate samples for direct estimation of the Kt/V values, with no blood sample required.