The brief of this Canadian Society of Nephrology (CSN) work group pertains to "adequacy of peritoneal dialysis [PD]." The aim was to update the previous set of guidelines published in 1999 (1). This update is required because of the publication, since 1999, of a significant number of important new studies advancing knowledge about adequacy in PD.
The general sentiment of the work group, even more so than was the case when the previous guidelines were drawn up, is that the term "adequacy" must be much more broadly defined. It should not be considered to apply to clearances alone, even though the term has been loosely used that way in the past. For present purposes, the group considered that adequate dialysis requires attention to volume status and nutrition as well as to clearances. Because volume status is critically related to blood pressure and other cardiovascular (CV) risk factors, it was felt to be important to address those topics also. Indeed, given the high cardiac mortality rates of dialysis patients, no area in their care is more worthy of focus than CV risk reduction. Clearances, volume, and nutrition are all profoundly influenced by residual renal function (RRF), and so a section on preservation of RRF has been given a prominent position. Glycemic control and the broader issue of the consequences of exposure to hypertonic glucose are also addressed.
Obviously, other areas of clinical care are also critical to provision of "adequate dialysis" (for example, maintenance of a good access, prevention of infection, calcium and phosphate management), but it was not felt appropriate to include those topics, given that they have been well addressed in other guideline documents.
As is customary in contemporary guideline documents, we have distinguished "clinical practice guidelines," which are based on strong published evidence, from "clinical practice recommendations," which are based on weaker evidence combined with the opinions of the work group. Not surprisingly and quite appropriately, the group generated many more recommendations than guidelines.
In most cases, evidence only from studies in PD patients was considered. However, in circumstances in which such studies were lacking, consideration was given to high-quality studies addressing relevant issues in other populations. Such studies included patients on hemodialysis (HD), patients with earlier stages of chronic kidney disease (CKD), and patients with CV disease. The risks of extrapolating such data to the PD population are recognized, but the therapeutic issues, especially in the area of CV disease, are so important and immediate that, pending the performance of analogous studies in PD patients, there is no reasonable alternative to this approach. Such extrapolations are, however, designated as recommendations, rather than as guidelines.
As the Reference section indicates, the work group has drawn liberally on the clinical practice guidelines of other expert bodies, both nephrologic and cardiologic, but at all times, it has attempted to apply them in the context of the Canadian PD population.
The work group included 8 nephrologists from around the country who are very involved in the clinical care of PD patients. Another nephrologist (RS), although not involved regularly with such patients, was included because she has expertise in epidemiology and evaluation of the medical literature and so took the role of ensuring objectivity. Finally, the Chair of the CSN Guidelines Committee (MT) is an ex officio member of the work group.
The guidelines that follow are intended to reflect the available evidence and the human and financial resources in Canada at the time of publication. While most proven therapies are currently funded in Canada, there may be only limited evidence, or evidence measured only by nonclinical endpoints, for the effectiveness with regard to clinical outcome of many therapies. Such therapies are either not funded or funded only for select groups of patients. Health care professionals are often uncomfortable taking resource constraints and medication costs into account when making therapeutic decisions. However, in health care systems with constrained budgets, directing excessive resources toward expensive, marginally effective therapies limits the resources available to be used for other effective therapies. Because physicians are often in a good position to compare the benefits and risks of specific therapies, they should take an active role in deciding which therapies should be made available, by reimbursement, to Canadian patients. Thus, resource implications have been considered for each guideline presented in this document, although only after a thorough consideration of the safety and effectiveness of the therapy or test in question.