Simulating inadequate dialysis and its correction using an individualized patient-derived nomogram

Abstract

Computerized kinetic modeling is a valuable automated peritoneal dialysis (APD) prescription tool for optimizing dialysis adequacy. However, non-compliance results in failure to achieve adequacy targets. The aim of this study was to determine if a nomogram could estimate dialysis compensations for shortfalls in simulated non-compliant patients, such that total weekly urea clearance (Kt/V(urea)) targets are met. Individualized nomograms comprising a series of curves were derived from PD Adequest (ver. 2.0)-predicted Kt/V(urea) data (r (2 ) > 0.99) for different APD prescriptions. The nomogram was then used to estimate the (Nomogram-computed) average of the daily Kt/V(urea) in 14 patients. The study comprised three 1-month phases. Patients were compliant to dialysis in phase I, where Adequest-predicted Kt/V(urea) showed good agreement with both measured (r (I) = 0.72), and Nomogram-computed values (r (I) > 0.99) (p < 0.001). Conversely, in non-compliant phase II, Nomogram-computed values were lower than Adequest-predicted values (p< 0.002). In phase III, the nomogram estimated prescription adjustments required to compensate for shortfalls, such that there was significantly less difference between Nomogram-computed and Adequest-predicted Kt/V(urea) than in phase II (p = 0.005). Thus, despite non-compliance, predicted Kt/V(urea) targets were attained using the nomogram to adjust the daily APD prescriptions. This concept is potentially useful for patients desiring to compensate for inadvertent shortfalls, rather than for 'truly non-compliant' patients.

Simulating inadequate dialysis and its correction using an individualized patient-derived nomogram

“…In the paper by Lee et al [1], the authors make use of data from peritoneal equilibration tests (PET) from a cohort of children and young adults on automated peritoneal dialysis (APD) in order to address the issue of nonadherence to the prescribed dialysis regimen. Whereas nonadherence is clearly the main thrust of paper, the concepts from this study can be extended to circumstances where for any reason one might have a run of inadequate dialysis nights, and therefore, other important lessons can be taken from this work.…”

“…But to use a hemodialysis concept as an analogy, Lee et al have extended the predictive power of their PD modeling software (PD Adequest® 2.0 in this case [4]) to produce the PD membrane equivalent of the hemodialysis (HD) dialyzer KoA curve. Whereas in HD one chooses to vary the blood or dialysate flow rates to achieve particular clearances of a given molecule for a given dialyzer, Lee et al [1] model a variety of PD conditions, cycle number, and bag strength in their study and then use these results to predict the clearance of small molecules that would be expected for those given parameters and that individual's kidney or peritoneal membrane. With this series of theoretical dialysis runs in hand and the presumption that deficient or nonadherent dialysis nights that are "replaced" with one or more "corrective nights" are beneficial, the authors use a limited set of these patient-derived prescriptions to improve the Kt/V delivered on nights following the periods of nonadherence to the scripted routine.…”

“…With this series of theoretical dialysis runs in hand and the presumption that deficient or nonadherent dialysis nights that are "replaced" with one or more "corrective nights" are beneficial, the authors use a limited set of these patient-derived prescriptions to improve the Kt/V delivered on nights following the periods of nonadherence to the scripted routine. The novel aspect of this work is that unlike the majority of such corrective prescription changes that are made based on general principles applicable to all patients on any given modality or with particular membrane characteristics, Lee and colleagues [1] use the individual's own PET modeling data to choose the best available alternate or enhanced prescription to: (a) achieve the required Kt/V to balance that lost due to prior nonadherence, (b) do the corrections as the month progresses, that is, not waiting till the monthly clinic visit.…”

“…But what Lee's study [1] demonstrates is that even before the newer technology is brought to bear we could make better use of what is currently available by creating their PD "KoA curves" for each of our patients. With this information in hand we would be able to send families home with sets of labeled and pre-programmed USB or memory cards with specific programs individually designed to achieve certain goals, e.g.…”

“…The paper by Lee et al [1] does have a number of limitations, including the very nature of the simulation wherein they chose to use their most dedicated patients to model nonadherent ones, and where the dialysis nonadherence was scripted and ordered by the nephrologist to ensure the patients were not put at risk. The authors also freely admit that this study does not demonstrate that this approach would allow for correction of either vastly nonadherent patients nor would it adequately address fluid overload as opposed to inadequate delivery of Kt/V.…”