Accuracy of using 30-minute post-dialysis BUN to determine equilibrated Kt/V

The equilibrated Kt/V (eKt/V), a clinical index of hemodialysis adequacy, can be calculated by several means. The commonly used methods are second generation of natural logarithm by Daugirdas and rate adjustment methods. However these two methods used immediate post-dialysis blood urea nitrogen (BUN) (C0). The authors investigated the accuracy of 30-minute post-dialysis BUN (C30), equilibrated BUN at the end of urea rebound time, to determine the eKt/V MATERIAL AND METHOD: We measured 7 values of eKt/V in 30 hemodialysis sessions by using the 5 following methods: 1). Empirical method (Emp) 2). Smye method (Sm) 3). Daugirdas method using C0 and C30 (Dau0, Dau30) 4). Rate adjustment method using C0 and C30 (Rate0, Rate30) 5). Double Pool urea kinetic model (DP), and compared with the gold standard values calculated by the modified Direct Dialysate Quantitative method (mDDQ).

All patients had adequate hemodialysis with eKt/V (mDDQ) = 1.80 + 0.22. Compared with mDDQ, the median of absolute difference of eKt/V were Rate30 (0.10); Dau30 (0.11), Rate0 (0.11), Sm (0.11); Emp (0.13); DP (0.15); Dau0 (0.35) while the correlation coefficient (r2) were 0.926, 0.948, 0.785, 0.629, 0.551, 0.833,and 0.806 respectively.

By using 30-minute post-dialysis BUN to calculate, the values of eKt/V by Daugirdas and rate adjustment methods were associated with better accuracy and correlation than immediate post-dialysis BUN. In the demand of the accurate eKt/V measurement, the Dau30 and Rate30 may be the suitable method to determine the eKt/V in clinical hemodialysis.