Routine Kt/V and Normalized Protein Nitrogen Appearance Rate Determined From Conductivity Access Clearance With Infrequent Postdialysis Serum Urea Nitrogen Measurements.

Conventional monitoring of hemodialysis dose is implemented using urea kinetic modeling based on single-pool Kt/V, which requires both pre- and postdialysis serum urea nitrogen (SUN) measurements. We compared this conventional approach to one in which Kt/V is calculated using conductivity clearance, thereby reducing the need for regular postdialysis SUN measurements. Comparative study of 2 diagnostic tests. Prevalent patients receiving maintenance hemodialysis for at least 2 years for whom both urea reduction ratio (URR) and average conductivity clearance (Kecn) were measured. During the initial 8 months (baseline interval), average Kecn and URR were used to calculate a median patient-specific, modeled, calibration solute distribution volume (Vcal). During months 9 to 16 (period 1) and 17 to 24 (period 2), Kt/V was conventionally computed using URR and also by a new method using Vcal and Kecn without postdialysis SUN values. We examined the percentage error between these 2 methods of calculating Kt/V. Concordance between the 2 methods of calculating Kt/V. Among 1,093 patients, mean individual-level median single-pool Kt/V values derived using the conventional method during the baseline interval, period 1, and period 2 were 1.62±0.24 (SD), 1.66±0.24, and 1.67±0.24, respectively. During periods 1 and 2, patient-level median Kt/V values derived using Kecn were 1.64±0.24 and 1.65±0.24, respectively. Percent differences between patient-level median values of Kt/V (conductivity minus conventional URR methods) were-0.63%±7.7% and-0.75%±8.4% for periods 1 and 2. Normalized protein nitrogen appearance were comparable between the 2 methods. Data were collected over 2 years. Study was limited to in-center hemodialysis patients dialyzed 3 times per week. Dialysis session length was not adjusted for treatment interruptions. A new method of calculating Kt/V based on Kecn that requires fewer postdialysis SUN measurements provided diagnostic data comparable to those from conventional use of URR and has the potential to avoid errors related to postdialysis blood sampling and measurement.

Raimann JG ，Ye X ，Kotanko P ，Daugirdas JT ... -  《-》

Eliminating the need for routine monthly postdialysis serum urea nitrogen measurement: A method for monitoring Kt/V and normalized protein catabolic rate using conductivity determined dialyzer clearance.

Many dialysis machines can compute dialyzer sodium clearances at multiple time points during a dialysis treatment using conductivity. For a given treatment, the average dialyzer sodium clearance (K), when combined with treatment time (t), and the estimated urea distribution volume (V, usually based on either anthropometry or bioimpedance), can be used to estimate Kt/V, an important measure of hemodialysis adequacy. While this conductivity-derived value for Kt/V correlates moderately with Kt/V calculated from predialysis and postdialysis serum urea nitrogen (SUN) values (urea reduction ratio, URR), the ultrafiltration volume, and session length it is, unfortunately, not sufficiently accurate to replace URR-based Kt/V. Here we underline the potential utility of an alternative method to estimate Kt/V (a variant of a technique originally proposed by Gotch and Levin and their colleagues) using conductivity-derived sodium clearance (K) that does not require routine measurement of the postdialysis SUN but which should closely track Kt/V computed in the usual fashion. The increased accuracy with the new method is explained by the use of a patient-specific value of V, which is an average value calculated from several dialysis sessions where both conductivity dialyzer clearance and predialysis and postdialysis SUN have been measured. Once this patient-specific conductivity/URR-based value for V has been determined, it can be used to calculate Kt/V for subsequent treatments in which conductivity-based dialyzer clearances are measured, but around which predialysis and postdialysis SUN values have not been obtained. (If the predialysis SUN values for such a subsequent treatment are also measured, then a normalized protein catabolic rate that closely tracks the value from conventional urea modeling, can also be determined.) By reducing the number of postdialysis SUN measurements needed to monitor hemodialysis adequacy this new method of estimating Kt/V by conductivity should save staff time and laboratory costs, increase patient and staff safety, and decrease error rates associated with improper postdialysis blood sampling technique.

Daugirdas JT 《-》

Effects of postdialysis urea rebound on the quantification of pediatric hemodialysis.

Urea rebound (UR) causes single pool urea kinetic modeling (UKM), which is based on end-dialysis urea instead of its equilibrated value (Ceq), to erroneously quantify hemodialysis (HD) treatment. We estimated the impact of postdialysis UR on the results of formal variable volume single pool (VVSP) UKM [Kt/V, urea distribution volume (V), urea generation rate (G), normalized protein catabolic rate (nPCR), and urea reduction ratio (URR)] in children on chronic HD. Thirty-eight standard pediatric HD sessions in 15 stable patients (9 female, 6 male) aged 14.5 +/- (SD) 3.28 years were investigated. The HD sessions lasted 3.75 +/- 0.43 h. The single pool urea clearance was 4.84 +/- 1.25 ml/min/kg. All HD sessions were evaluated by VVSP and URR (%) with postdialysis urea taken at the end of HD and with Ceq taken 60 min after the end of HD, incorporating double pool effects and representing true double pool values. The anthropometric V was calculated by Cheek and Mellits formulae for children. VVSP significantly overestimated Kt/V by 0.26 +/- 0.18 U (1.68 +/- 0.36 vs. 1.42 +/- 0.30, p < 0.0001), i.e., 19. 05 +/- 13.07%, G/V (0.20 +/- 0.04 vs. 0.18 +/- 0.04, p < 0.0001), nPCR (1.26 +/- 0.23 vs. 1.18 +/- 0.22 g/kg/day, p < 0.0001), and URR (73.92 +/- 6.49 vs. 69.22 +/- 7.06, p < 0.0001). VVSP significantly underestimated kinetic V in comparison to anthropometric V (18.74 +/- 4.04 vs. 20.76 +/- 4.43 liters or expressed as V/body weight: 58 +/- 8 vs. 65 +/- 9%, p < 0.05), while double pool kinetic V was more accurate (21.45 +/- 4.34 liters, V/body weight: 64 +/- 6%, p > 0.05). We conclude that UR has a significant effect on all results of UKM even after standard pediatric HD, and the degree of this efffect is documented. We suggest an increase of the minimum required prescribed single pool Kt/V in children and reduction of any delivered single pool Kt/V by approxiamtely 0.26 Kt/V U. Overestimation of nPCR by approximately 0.08 g/kg/day and underestimation of V by 8.5% should be kept in mind.

Marsenić O ，Pavlicić D ，Bigović G ，Peco-Antić A ，Jovanović O ... -  《NEPHRON》

Variation in blood sample collection for determination of hemodialysis adequacy. Council on Renal Nutrition National Research Question Collaborative Study Group.

Beto JA ，Bansal VK ，Ing TS ，Daugirdas JT ... -  《-》

Postdialysis urea rebound: determinants and influence on dialysis delivery in chronic hemodialysis patients.

Leblanc M ，Charbonneau R ，Lalumière G ，Cartier P ，Déziel C ... -  《AMERICAN JOURNAL OF KIDNEY DISEASES》