Determination of haemodialysis adequacy by ionic dialysance: clinical application and limitations

Background and aim of study: Morbidity and mortality in hem dialysis patients are closely related to dialysis adequacy. Recently, ionic dialysance is becoming more popular as a method to assess the delivered Kt/V of dialysis treatment. The aim of this study was to assess the correlation between Kt/V measured by ionic dialysance (Kt/Vocm) and Kt/V calculated with Daugirdas formula (Kt/V D) taking into account different estimates of urea distribution volume(V) and to assess the variability of treatment dose delivered to individual patients.  Methods: Our prospective study was conducted for 4 weeks period on 40 patients(22 males,18 females) with ESRD on regular hemodialysis. Hemodialysis treatments for the studied patients were performed using a Fresenius 5008 machine equipped with online clearance monitor (ocm). Ionic dialysance was measured by conductivity monitoring for the studied patients per session. The second generation Daugirdas formula was used to calculate the Kt/V (Kt/V D) per week. Values of V to allow comparison between Kt/Vocm and blood-based Kt/V were determined using Watson formula (Vw) and bioimpedance spectroscopy (Vimp). Results: There was a significant correlation between Kt/V measured by ionic dialysance with using Watson formula to determine urea volume distribution (Kt/Vw.ocm) and Kt/V calculated by Daugirdas formula (Kt/V.D) in both single and double pool. However, Kt/Vw.ocm underestimated Kt/V.Dsp by 9.0% (−0.139 ± 0.2673 and the Kt/VD. eq by 6.7%(−0.1080 ± 0.2082) The correlation between Kt/Vocm when V values estimated using Vimp and Kt/V.Dsp or Kt/V.Deq became stronger. Kt/Vocm varied greatly within individual patients, but there was no statistically significant difference between the coefficient of variations (CVs), from either method. Conclusion: Kt/V measured by ionic dialysance appears to be of good clinical interest and adequacy. Accurate estimation of V is required for Kt/V calculated from ocm to be consistent with the blood-based methods. Bioimpedance spectroscopy(Vimp) used for estimating V ensure better correlation between ocm and blood-based Kt/V.Substantial variation in Kt/V implies repeated measures are necessary to gain a true picture of the mean treatment dose being delivered to patients.