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 2^nd generation formula from blood samples (Kt/V_sp 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/V_sp 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 2^nd generation formula (Kt/V_DC_D(60)-C_D(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/V_sp Daugirdas values equilibrated according to Daugirdas rate formula, and Kt/V_DC_D(60)-C_D(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.