In light of the recent peritoneal solution shortage crisis (see our Viewpoint in this issue), it seems prudent to revisit the concept of incremental peritoneal dialysis (PD), in which solution use is efficiently minimized. A working definition of incremental dialysis is adding dialysis in specific doses over time to achieve adequate correction of uremia. This combines the use of residual kidney function (RKF) plus artificial kidney function (i.e. dialysis). While this can be performed with any form of dialysis, this commentary will focus exclusively on incremental PD.
While the concept of incremental dialysis has been described for decades, 1, 2 advocates for its use in PD appeared after the initial Dialysis Outcome Quality Initiative (DOQI) deliberations, as articulated in the 1997 Peritoneal Dialysis Adequacy Guidelines 3 and further described by Work Group members. 4-8 Subsequent experiences have been reported worldwide. 9-14
While both incident (new starts) and prevalent patients may utilize incremental dialysis, most prevalent patients performing incremental dialysis have substantial and sustained RKF, making incremental PD feasible. Most PD patients performing incremental PD initiate with incremental and add PD doses to supplement their progressive loss of RKF. This distinction is important because successful incremental PD requires an understanding by the physician, nurse, and patient that increases in dialysis dose are inevitable as RKF declines over time.
In prevalent patients, incremental PD is often used as a transition to another form of kidney replacement therapy, usually hemodialysis. However, there may be psychological, social and/or economic reasons to perform incremental dialysis in prevalent patients. For example, a patient living alone far from a hemodialysis unit may have a helper who can only assist with an automated PD regimen (APD) several nights per week. Another example is the current PD dialysis solution shortage.
This commentary will describe the use of incremental PD in incident patients who have RKF and whose care team understands and accepts that PD doses will increase over time as RKF declines.
Candidates for incremental PD
While each patient has his/her individual response to kidney failure, we know that in general a weekly Kt/V of > 1.7 supports a reasonable quality of life. For simplicity’s sake we will use this as minimal doses to achieve adequacy, by combined PD and RKF. Residual kidney urea clearance is simply added to PD urea clearance, using such a measurement to assure that adequate PD doses are utilized. However, in the end, carefully assessed clinical evaluation is extremely valuable and is the major determinant of “adequacy.” A patient truly thriving or improving on an incremental regimen is adequately treated. In particular, maintaining or gaining non-edema weight is extremely informative and utilizing tools such as subjective global assessment may be helpful but are not absolutely necessary.
In incremental PD, numerous regimens are utilized. Therefore, adapting the regimen to life style and RKF is not difficult. For example, an incident patient who is very active during the day may be suited to being empty or having a low fill volume during the daytime. More dialysis could be done after the active period using a cycler or not. Most patients tolerate larger fill volumes when supine.
Patients may not get a Peritoneal Equilibration Test (PET), but training nurses to get an impression of ultrafiltration potential is a good first step, and they can usually determine low versus high transporter. Even low transporters are likely to saturate dialysate at 6 hours, so incremental PD using exchanges exceeding 6 hours probably are not clearing small molecules better than exchanges less than 6 hours. Larger molecule clearance continues even after 6 hours due to their slower transport.
If lifestyle suggests exchanges longer than 6 hours, then other exchanges or RKF must compensate. Diffusive solute clearance in each of two 12-hour icodextrin or 4.25% dextrose exchanges will end much earlier than when they are eventually drained, yet might continue to allow solute clearance throughout the dwell via continued convection, right up until drainage. Other exchange regimens exceeding 6 hours could be three symmetric exchanges of approximately 8 hours. As suggested above, two exchanges of 6 or 7 hours each can improve symptoms in patients with residual GFRs of 6-10 mL/min. Diuretics can be employed to maintain proper volume status despite longer dwell times with potentially lower ultrafiltration rates. 15
APD cyclers easily accommodate incremental PD. Regimens of 3-4 exchanges over 8 to 10 hours with dry days have been applied 3 to 7 times per week. The dry period has the advantage of allowing more aggressive physical activity (exercising, playing sports) as well as peritoneal membrane resting, where the membrane recovers from being exposed to PD solutions. Host defenses are enhanced by dry periods. So utilizing APD for incremental PD makes sense on several levels. One 6-liter bag can be used for two 3-liter exchanges or for three 2-liter exchanges and only one bag (one prong) is opened for that APD session.
A cost-effective, efficient, and risk-adverse method to improve PD clearance is to increase the fill volume. Again, being in the supine position or during less aggressive physical activity is the best period for this larger fill volume approach. Three exchanges per day of 2.5 or 3 liters can markedly supplement RKF and reduce the patient’s time commitment for exchanges (about 30 minutes/exchange) and probably decreases the risk of infection from possible technique breaks.
Incremental PD mandates some RKF to deliver adequate kidney replacement therapy. Lacking supplementary RKF, full dose PD should be administered.
Understanding how the therapy works
Incremental PD should be avoided where the patient and his/her family do not understand or appreciate that PD dose must be increased over time and such acceptance is not assured. If the dialysis staff do not understand the concept, do not attempt incremental PD. Dialysis organizations, ESRD Networks, managed care organizations and insurers can be educated to understand incremental dialysis.
An integrated end-stage kidney disease program can best serve its patients understanding the value of this incremental approach. Incremental PD is a worthwhile under many circumstances, but in this period of a PD solution shortage, it may be even more important. The North American Chapter of the International Society of Peritoneal Dialysis supports this concept.
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