Peritoneal Dialysis Capacity, PDC^TM

A constant biochemical environment of our cells is a prerequisite for life. The kidneys have a key role in maintaining this constant "milieu intérieur" as denoted by Claude Bernard (in Introduction à la médecine expérimentale, 1865). It is therefore not surprising that renal diseases are associated by a wide spectrum of more or less nonspecific symptoms. Today there are several renal replacement therapies for the growing number of people suffering from severe renal failure. The main three alternative treatments are hemodialysis, peritoneal dialysis and renal transplantation. Many patients find peritoneal dialysis, PD, to be the most attractive dialysis alternative. There are several forms of PD: Continuous ambulatory PD (CAPD) requires manual exchanges of 2 (1½-2½) liters, 4 (-5) times per day. Automatic PD (APD) requires a machine that assists with the exchanges often during the night and exists in several forms (CCPD, TPD, NIPD). 

Over the last years there have been growing interests in quantitating dialysis, both HD and PD. Recently, the minimum target required for adequate peritoneal dialysis was increased by a group of experts in the field (1996). Thus, peritoneal dialysis is dependent on a living membrane with unknown and dynamic properties, which makes standardized measurements of PD functions at least as important as for HD. There are several ways of measuring how effective the dialysis is. One may use clearance for a solute like creatinine or fractional clearance for urea, also denoted Kt/V for urea. Moreover, there are a few computer programs available that facilitates the calculations. 

PDC™ is the only software that estimates the peritoneal transport characteristics for the individual patients and uses modern capillary physiology to simulate PD exchange with any modality. It then presents the results graphically in a user-friendly environment, see below, allowing for interactions between patient, nurse and physician. Hereby, patient compliance may be improved and PDC can be used as a pedagogical tool. Haraldsson has clinically validated the program in 100 adult patients on CAPD and there are ongoing clinical trials in several hospitals. Presently (Nov. 1996) the program is in use in more than 120 hospitals in 20 countries. 

The central core in the program is displayed below. To the left, the PD-regime can be selected and changed. In the example a CCPD regime with 7 cycles of 2100ml and one day-time exchange is selected. The effects in terms of PD clearance and fluid removal are displayed to the right (middle panel) immediately after recalculation. In this middle panel, blue bars represent effects of PD alone and the effects of PD+renal are shown in yellow. Effects on the diet of the chosen PD-regime are given in the bottom panel to the right (yellow denotes the effects of PD per se). Finally, the right top panel shows the peritoneal dialysis transport characteristics (PDC) parameters of Mr. Richard Jones. The parameters are presented in percent of normal values for 100 adult patients. The "Area" is really the unrestricted pore area over diffusion distance, "Absorption" is the final reabsorption rate when the glucose gradient has dissipated and "Plasma loss" is the flow of protein rich fluid through the large pores. 

There are however several other panels that can be displayed, see below:

Or as the following graph shows 
In order for these modified three pore model equations to successful in describing reality the input data must be adequate. Therefore, a standardized PDC protocol has been developed with information based on 5 exchanges during a CAPD day, see below.
Or for CCPD: How well does it describe reality. Well, it depends on the quality of the measurements and can be displayed for each patient 
Questions or comments? Please contact me.

Best wishes

Börje Haraldsson

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