Rationale for Guideline Kt/V urea Targets for Peritoneal Dialysis
Peritoneal Dialysis Adequacy Targets
Contribution from the Caring for Australians with Renal Impairment (CARI)Guidelines Committee
The 2005 CARI Dialysis Adequacy (PD) Guideline recommends:
- For CAPD and APD the weekly Kt/V urea target should be > 1.6/week. The minimum weekly CCr target should be 60L/week in high and high average transporters and 50L/week in low and low average transporters.
And offers as a “clinical suggestion”:
- Guidelines to be modified with patients of low or high BMI. For patients with a BMI > 27.5kg/m2, normalised clearance values may be difficult to achieve. Adequacy needs to be interpreted in the context of body size.
Rationale: There are several key aspects upon which the CARI guidelines differ from other guidelines:
- Kt/V target: The minimum weekly Kt/V target recommended by CARI is 1.6, whilst the updated KDOQI and EBPG guidelines recommend 1.7. The rationale for the CARI target is based on the Ademex trial (Paniagua et al 2002) in which no clear survival advantage was seen between the control group (mean achieved peritoneal Kt/V 1.62) versus the intervention group (mean peritoneal Kt/V 2.13). Similarly, in a study of 320 incident Chinese CAPD patients (Lo et al) randomised to 3 different weekly total Kt/V targets (1.5-1.7, 1.7-2.0 and >2.0), no difference was observed in the primary outcome measure of survival. As with the KDOQI and EBP guidelines, the CARI guidelines do permit total Kt/V to be calculated by summing peritoneal and residual Kt/V for the purposes of determining whether minimum targets are reached (even though the two parameters are not mathematically equivalent). CARI also emphasises that there are many other aspects of dialysis adequacy to consider apart from small solute clearance (including ultrafiltration, bone mineral metabolism, anaemia management, and clinical assessment of well-being and consideration of the impact of treatment on the patient’s life).
- Creatinine clearance target: CARI has decided to continue with recommending a minimum creatinine clearance target, even though this has been abandoned by the latest iteration of the KDOQI guidelines. The rationale for CARI’s position is that the key intervention in the Ademex study was a modified prescription to achieve a peritoneal clearance of greater than or equal to 60 L/week/1.73 m2. Since the intervention was not based on achieving a Kt/V target, it seems incongruent with the literature to specify a minimum Kt/V target only. There is also insufficient evidence to determine whether achieving a Kt/V target is more important that achieving a creatinine clearance target or vice versa.
- Ultrafiltration targets: Although the EBPG recommends a minimum peritoneal ultrafiltration of 1 L/day, the CARI guidelines (like the KDOQI guidelines) do not specify a particular ultrafiltration target. This is because there are no randomised controlled trials on the subject.
- Levels of evidence: The CARI guidelines use the Australian National Health and Medical Research Council classification system for evidence levels and derives guidelines with only Level I or II evidence (meta-analysis or well designed randomised controlled studies). Where lower levels of evidence only are available, it is used to derive ‘Suggestions for Clinical Care’.
- Frequency of monitoring of dialysis adequacy: No guideline recommendations are made as there is no level I or II evidence in this area (hence, they appear as ‘Suggestions for Clinical Care’).
Prepared on behalf of CARI by David Johnson, Convenor of CARI Dialysis Adequacy (PD) Working Group
