KT Measurements Using Ionic Dialysance are Independent of Monitor

Abstract

In their excellent paper,1Maduell F. Vera M. Arias M. et al.Influence of the ionic dialysance monitor on Kt measurement in hemodialysis.Am J Kidney Dis. 2008; 52: 85-92Abstract Full Text Full Text PDF PubMed Scopus (22) Google Scholar Maduell et al conclude that Kt measured by ionic dialysance is a valid parameter for delivered dialysis dose, but a correction is needed to compare data from different dialysis monitors. With treatment parameters seemingly equal, the authors found a close to 10% difference in Kt and about an 8-mL/min difference in ionic dialysance between monitors used in Fresenius Medical Care (Bad Homburg, Germany) and Gambro (Stockholm, Sweden) machines. We agree that ionic dialysance is useful for dose evaluation, and believe that the differences found mainly relate to different philosophies of adjusting machine settings to prevailing conditions. First, we believe that the actual blood flows may have differed. While Fresenius machines may operate at a corrected blood flow rate, ie, a set blood flow rate adjusted for the negative pressure before the blood pump, the Gambro philosophy is to work on the operator setting and display the estimated effective blood flow rate. For the fairly high blood flow rates used in this study, the difference in actual flow rate can be 5% to 10%, corresponding to a 2% to 4% difference in clearance. This agrees with measured ionic dialysance. Second, as indicated by the authors, we think there is a difference in actual treatment time. On Fresenius machines, the remaining treatment time is not decreased during fluid bypass periods. On Gambro machines, the set treatment time is kept so that staff and patients can predict when the treatment will end, while the nondiffusive time is displayed. Data given on Kt and ionic dialysance indicate treatment times of about 264 and 247 minutes for the 2 machine types, a difference of about 6%. In conclusion, we believe that we have found probable causes for the differences in Kt measured by Maduell et al. Ionic dialysance can therefore be used for dose evaluations without any corrections for monitor, provided that all the actual treatment parameters are the same. Maduell et al also attempt to correct the measured ionic Kt values for differences in treatment dose as measured by blood-based Kt/V. However, due to pool effects in the body, single-pool Kt/V increases quickly during the first half hour and then more slowly. This means that increased treatment time (or increased clearance) will increase single-pool Kt/V less than proportionally. On the contrary, with K constant, Kt based on ionic dialysance will increase linearly with time. Therefore such a correction cannot be completely effective. Financial Disclosure: Both authors are employees of Gambro Lundia AB. Influence of the Ionic Dialysance Monitor on Kt Measurement in HemodialysisAmerican Journal of Kidney DiseasesVol. 52Issue 1PreviewIonic dialysance can provide accurate monitoring of dialysis dose during each hemodialysis session. Increasingly, hemodialysis machines incorporate devices that measure ionic dialysance, allowing the dialysis dose to be determined noninvasively in real time and in each session. Because Kt product was proposed as a measure of hemodialysis dose to avoid the reverse J-shaped curve between urea reduction ratio or Kt/V and mortality, we investigated whether ionic dialysance values and Kt measurements are affected by different ionic dialysance monitors (Diascan and online clearance monitoring [OCM]) and dialysis machines. Full-Text PDF In Reply to ‘KT Measurements Using Ionic Dialysance Are Independent Of Monitor’American Journal of Kidney DiseasesVol. 52Issue 5PreviewWe thank Nilsson and Sternby for their comments.1 In our comparative study, we reported that measurement of ionic dialysance and Kt were affected by different dialysis machines.2 The Diascan (Hospal, Medolla, Italy) device showed Kt values lower than those obtained using online clearance monitoring. This difference was partly due to a real diminished dialysis dose and partly to intermethod differences. Full-Text PDF