Solute solver 'what if' module for modeling urea kinetics.

The publicly available Solute Solver module allows calculation of a variety of two-pool urea kinetic measures of dialysis adequacy using pre- and postdialysis plasma urea and estimated dialyzer clearance or estimated urea distribution volumes as inputs. However, the existing program does not have a 'what if' module, which would estimate the plasma urea values as well as commonly used measures of hemodialysis adequacy for a patient with a given urea distribution volume and urea nitrogen generation rate dialyzed according to a particular dialysis schedule. Conventional variable extracellular volume 2-pool urea kinetic equations were used. A javascript-HTML Web form was created that can be used on any personal computer equipped with internet browsing software, to compute commonly used Kt/V-based measures of hemodialysis adequacy for patients with differing amounts of residual kidney function and following a variety of treatment schedules. The completed Web form calculator may be particularly useful in computing equivalent continuous clearances for incremental hemodialysis strategies.

Daugirdas JT 《-》

Solute-solver: a web-based tool for modeling urea kinetics for a broad range of hemodialysis schedules in multiple patients.

Daugirdas JT ，Depner TA ，Greene T ，Silisteanu P ... -  《-》

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 《-》

What volume to choose to assess online Kt/V?

Casino FG ，Mancini E ，Santarsia G ，Mostacci SD ，D'Elia F ，Di Carlo M ，Iannuzzella F ，Rossi L ，Vernaglione L ，Grimaldi D ，Rapanà R ，Basile C ... -  《-》

Urea kinetics during sustained low-efficiency dialysis in critically ill patients requiring renal replacement therapy.

Continuous renal replacement therapies have practical and theoretical advantages compared with conventional intermittent hemodialysis in hemodynamically unstable or severely catabolic patients with acute renal failure (ARF). Sustained low-efficiency dialysis (SLED) is a hybrid modality introduced July 1998 at the University of Arkansas for Medical Sciences that involves the application of a conventional hemodialysis machine with reduced dialysate and blood flow rates for 12-hour nocturnal treatments. Nine critically ill patients with ARF were studied during a single SLED treatment to determine delivered dialysis dose and the most appropriate model for the description of urea kinetics during treatment. Five patients were men, mean Acute Physiology and Chronic Health Evaluation (APACHE) II score was 28.9 and mean weight was 92.5 kg. Kt/V was determined by the reference method of direct dialysate quantification (DDQ) combined with an equilibrated postdialysis plasma water urea nitrogen (PUN) concentration and four other methods that were either blood or dialysate based, single or double pool, or model independent (whole-body kinetic method). Solute removal indices (SRIs) were determined from net urea removal and urea distribution volume supplied from DDQ (reference method) and by mass balance using variables supplied from blood-based formal variable-volume single-pool (VVSP) urea kinetic modeling. Equivalent renal urea clearances (EKRs) were calculated from urea generation rates and time-averaged concentrations for PUN based on weekly mass balance with kinetic variables supplied by either DDQ (reference method) or formal blood-based VVSP modeling. Mean Kt/V determined by the reference method was 1.40 and not significantly different when determined by formal VVSP modeling, DDQ using an immediate postdialysis PUN, or the whole-body kinetic method. Correction of single-pool Kt/V by a Daugirdas rate equation did not yield plausible results. Mean SRI and EKR by the reference methods were 0.61 and 24.8 mL/min, respectively, and not significantly different when determined by blood-based methods. A single-pool urea kinetic model adequately described intradialytic PUN profiles, indicating that SLED was associated with minimal urea disequilibrium. This was supported by the parity between hemodialyzer and whole-body urea clearances, and the mean postdialytic urea rebound of 4.1% (P = 0.13 versus zero). Additional prospective studies are needed in this setting to define the optimal method for dialysis quantification, targets for azotemic control, and optimal modality of renal replacement therapy. In conclusion, SLED delivers a high dose of dialysis with minimal associated urea disequilibrium and can be quantified by Kt/V, SRI, and EKR from blood-based methods using single-pool urea kinetic models.

Marshall MR ，Golper TA ，Shaver MJ ，Alam MG ，Chatoth DK ... -  《-》