Online Conductivity Monitoring of Dialysis Adequacy Versus Kt/V Derived from Urea Reduction Ratio: A Prospective Study from a Saudi Center

Abstract

Introduction. Adequate delivered dose of solute removal (as assessed by urea reduction and calculation of Kt/V) is an important determinant of clinical outcome in chronic hemodialysis (HD) patients. This requires both prescription of an adequate dose of HD and regular assessment that the delivered treatments are also adequate. Online conductivity monitoring (OCM) using sodium flux as a surrogate for urea allows for the repeated non-invasive measurement of Kt/V on each HD treatment. Methods. We prospectively studied 17 (9 males, 8 females) established chronic HD patients over an eight-week period (408 treatments). A preand post-dialyzer measurement of the conductivity is performed by two mutually independent temperature-compensated conductivity cells equipped with Fresenius 4008 S ® dialysis machines. Urea reduction was measured once a week by a single-pool calculation using immediate post-treatment sampling. No changes were made to any of the dialysis prescriptions over the study period. Values of calculated Kt/V and simultaneously obtained online Kt/V were compared. Results. There was a statistically significant difference between calculated Kt/V and online Kt/V over the study period. The mean calculated Kt/V was 1.37 ± 0.09, and mean online Kt/V 1.02 ± 0.15 (p = 0.000). Calculated Kt/V ≥ 1.2 was achieved in all our patients, while online Kt/V ≥ 1.2 was achieved in only 17.64%. Yet there was moderate correlation between calculated Kt/V and online Kt/V (r 2 = 0.48). Conclusions. Online conductivity monitoring (OCM) results underestimates dialysis efficiency compared to calculated Kt/V readings. This difference has to be considered when applying Kt/V to clinical practice.

Correlation between Dt/V derived from ionic dialysance and blood-driven Kt/V of urea in African-American hemodialysis patients, based on body weight and ultrafiltration volume

“…We found an overall moderate correlation between the Kt/V of urea and Dt/V ( r = 0.602), which was similar to some [ 10 , 12 , 13 , 23–25 ] but not all [ 9 , 11 , 27 ] previous studies. This observed discordance among different studies is due to differences in the methodology used to estimate the V and/or variability in the measurement protocol of the Kt/V-urea.…”

“…In the whole study group we report a moderate degree of correlation between the Dt/V and the Kt/V-urea with a mean Dt/V less than the mean Kt/V. This has already been well-demonstrated in numerous studies over the past two decades, [ 8 , 11 , 23–25 ]. This is possibly explained by the overestimation of V using the Watson’s formula [ 8 , 13 , 16 , 19 ], as well as underestimation of K by D most likely caused by recirculation [ 26 ].…”

“…While studies that used DDQ [ 9 ] or delayed post-dialysis blood urea sampling [ 11 ] for the measurement of Kt/V had better correlations with the Dt/V, it will be difficult to implement this into routine clinical practice due to their cumbersome nature and associated patient inconvenience. Previous studies that employed methods similar to ours (Watson’s anthropological estimation of V to compute the Dt/V and second-generation Daugirdas formula to assess the SPVV Kt/V) reported similar [ 10 , 12 , 13 ] or lower [ 23–25 ] correlation rates. This observed tendency toward better correlation in our study compared with previous studies using similar methodology can be explained by the less remarkable overestimation of V observed in African-Americans compared with Caucasians when the Watson formula is used [ 17 ].…”

Online Kt/V Monitoring in Haemodialysis by UV Absorbance: Variations during Intra-Dialytic Meals

“…OCM uses short pulsed variations in solute concentration to estimate sodium flux along the dialyser as a surrogate for urea clearance [13]. These conductivity-derived values are used together with the patient's urea distribution volume to calculate Kt/V [2].…”

Assessment of hemodialysis adequacy: Correlation between online clearance monitoring and single pool Kt/V.

“…28 The studies that had poor correlation, suggested that there may have been an erroneous V calculation. 29,30 In a paper evaluating various studies, Aslam et al 31 concluded that the various online methods available for dialysis adequacy provide a reliable and safe technique while providing excellent correlation with Kt/V.…”