Estimating dialysis adequacy using ionic dialysance

The aim of this study was to determine the efficacy and feasibility of estimating dialysis adequacy using ionic dialysance (ID). We retrospectively reviewed the medical records of patients receiving thrice weekly dialysis for an eight-month period at a single-center Veterans Affairs hospital. Dialysis adequacy was determined monthly using pre- and post-treatment BUN measurements to calculate the single pool Kt/V (spKt/V) with the formula set forth by Daugirdas. On the same treatment day, K(ID)t was determined by multiplying the average ID times the time (t) of the treatment. A surrogate volume, V(ID), was estimated by dividing K(ID)t by spKt/V using data from the first six months. During the subsequent two months, we compared dialysis adequacy estimated by urea-based spKt/V to ionic dialysance based K(ID)t/V(ID) utilizing V(ID). In the first month, K(ID)t/V(ID) estimations and the simultaneous spKt/V determinations averaged 1.55 +/- 0.36 and 1.59 +/- 0.42, respectively. In the second month, K(ID)t/V(ID) and spKt/V averaged 1.52 +/- 0.33 and 1.54 +/- 0.35, respectively. K(ID)t/V(ID) correlated well with spKt/V, as the slope was 0.85 (r = 0.95, p < 0.001). There was considerable intra-patient variability of K(ID), time, and K(ID)t/V(ID) with coefficient of variations (CV) of 8.4 +/- 4.3, 9.0 +/- 5.3, and 15.8 +/- 9.2, respectively. However, the CV for K(ID)t/V(ID) was similar to the CV for spKt/V (15.3 +/- 7.4). These results suggest that it is possible to estimate dialysis adequacy during every treatment using K(ID)t/V(ID). Furthermore, there is considerable variability in the delivered dialysis adequacy, suggesting that many sessions result in sub-optimal dialysis.