Ultrafiltration Efficiency During Automated Peritoneal ...

1 Advances in Peritoneal dialysis , Vol. 24, 2008 Ultrafiltration EfficiencyDuring AutomatedPeritoneal dialysis UsingGlucose-Based SolutionsThe Ultrafiltration (UF) Efficiency of Peritoneal di-alysis (PD) solutions , defined as the net UF dividedby the amount of carbohydrate absorbed per dwell,has been shown to be higher During long dwells icodextrin solution (Extraneal: BaxterHealthcare corporation , Deerfield, IL, ) thanduring those with glucose-based solution ( Dianeal: baxter healthcare corporation ),prompting a better understanding of UF used the three-pore kinetic model of PD trans-port to investigate UF Efficiency for single long dwellsand various combinations of multiple short glucose-based dwells During Automated PD (APD).

2 To dem-onstrate a practical consequence of the effect of dwelltime, we simulated two hypothetical APD prescrip-tions (A and B) in which fluid with a high glucoseconcentration was used During either the long daydwell (A: ; B: ) or the short night dwells(A: 3 + 1 ; B: 4 ).Computer simulations showed that higher glucose concentrations and shorter dwelltimes increase the UF Efficiency of a single dwell,and UF Efficiency depends on patient 24-hour APD therapy was simulated for alow-average transporter, the net UF did not differconsiderably (A: 1132 mL; B: 1154 mL), but totalcarbohydrate absorption was higher when solutionwith a high glucose concentration was used duringthe single long dwell (A: 146 g; B: 137 g), resultingin lower UF Efficiency (A: mL/g; B: mL/g).

3 Alp Akonur, Clifford J. Holmes, John K. LeypoldtFrom: Renal Division, baxter healthcare corporation ,McGaw Park, Illinois, conclude that the UF Efficiency of the entireregimen should be considered in prescribing PDtherapy. When available, Extraneal provides the bestUF Efficiency During long dwells. Our simulationssuggest that raising the glucose concentration in theshort dwells and lowering it in the long dwell is theoptimal strategy to maximize UF Efficiency duringAPD when Extraneal is not wordsUltrafiltration, Ultrafiltration Efficiency , glucose absorp-tion, Automated Peritoneal dialysisIntroductionContinuous ambulatory and Automated Peritoneal di-alysis (PD) patients are dialyzed primarily with solu-tions that use glucose as the osmotic agent.

4 However,evidence is growing that use of glucose-based PDsolutions is accompanied by undesirable amounts ofsystemic glucose absorption (1) and changes in peri-toneal membrane physiology caused by exposure tohigh concentrations of glucose, glucose degradationproducts, and advanced glycosylated end-products(2). Several studies have shown that continual expo-sure to hypertonic solutions ( glucose) resultsin irreversible changes in Peritoneal membrane struc-ture, possibly leading to higher-than-normal small-solute permeability of the membrane (1,3) andeventually Ultrafiltration failure (1 3).

5 Extraneal ( baxter healthcare corporation , Deerfield,IL, ), a icodextrin solution, is advantageousfor single long-dwell exchanges of 8 16 hours, be-cause it maintains sustained Ultrafiltration (UF) for theentire dwell with a lower amount of carbohydrate (CHO)absorption. These combined benefits can be summa-rized in a single parameter, UF Efficiency , defined asthe net UF divided by the amount of CHO compared with either or dextrose70 Akonur et , Extraneal has a UF Efficiency superior to thatof either glucose-based solution for long dwells (4).In the present study, we examined the concept ofUF Efficiency in the treatment of Automated PD (APD)patients using only glucose-based solutions usingcomputer simulations of the theoretic three-pore modelof PD transport.

6 This work shows that the APD pre-scription can alter UF Efficiency when calculated overa 24-hour and methodsPatient dataThe patient parameters used in this study were ob-tained from data submitted to the baxter HealthcareRenal Division in 1999 by centers around the UnitedStates and Canada participating in a national adequacyinitiative program (TARGET: baxter healthcare Cor-poration). The data were grouped in categories ac-cording to Peritoneal transport status: high, highaverage, low average, and low. Relevant kinetic trans-port parameters such as solute mass transfer area co-efficient [MTAC (mL/min)], Ultrafiltration coefficient[LPA (mL min 1 mmHg 1)], and transport surface area[A0/dX (cm)] were estimated using PD Adequest (5).

7 Four typical patients were then created as repre-sentatives of each category. Tables I and II show thetypical physiologic characteristics and kinetic param-eters for each patient transport model and verificationIn our study, the goal was to use the set of averagepatient parameters already mentioned to provide a bet-ter understanding of the factors influencing the UFefficiency of glucose-based PD solutions . The UF andthe dialysate solute concentrations were simulated,based on a modified three-pore membrane model (5 7). A formal validation for small-solute removal and UFhad previously been performed for PD Adequest (5), which also constitutes the basis of the three-poremodel used here.

8 The Matlab software program ( : The Mathworks, Natick, MA, ) wasused to solve fluid and solute transport equations byapplying numeric the fundamental Peritoneal transportformalism does not differ from that for PD , we made certain changes. It was therefore neces-sary to compare simulation results with clinical dataas a means of informal verification. To do that, weobtained permission from Dr. P. Freida to reprint re-cently published UF and Na removal data (8).Figure 1 compares measured (8) net UF and Naremoval and model simulations. The patients reportedby Dr. Freida were high-transport patients.

9 It is clearthat there is large variability in UF and Na measure-ments alike. To make the comparison, we simulatedboth high transport and high-average transport pa-tients as noted in the figure. It is evident that themodel simulations are in reasonable agreement withthe clinical efficiencyThe UF Efficiency , defined as the net UF divided bythe amount of total CHO absorbed,UF Efficiency = net UF (mL) /total CHO absorbed (g), [1]has previously been suggested as a new metric toguide the design of optimal therapy regimens and newsolution development (4).In the clinical setting, UF and total CHO absorp-tion are measured only at the end of a patient s a result, that measurement yields a single UF effi-ciency value associated with a particular solution andtherapy.

10 In the present work, we show that UF effi-ciency is not solely associated with a solution ortherapy regimen, but should be considered depen-dent on a variety of factors, including dwell time, con-centration of the osmotic agent, transport status (asmeasured by a Peritoneal equilibration test). We illus-trate these principles by examining the general depen-dency of UF Efficiency on these parameters forTABLE I Patient characteristics by Peritoneal transportcategory as assessed in a Peritoneal equilibration test(PET)PETAgeWeightHeightBSATBW category(years)(kg)(cm)(m2)(L) = body surface area; TBW = total body water; H =high; HA = high average; LA = low average; L = Efficiency During APD with Glucose Solution71glucose-based solutions .