Rationale for Guideline Kt/V urea Targets for Peritoneal Dialysis

Peritoneal Dialysis Adequacy Targets

Contribution from Canadian Society of Nephrology Clinical Practice Guidelines Committee

CSN Guidelines Statement extracted from the PD CPGs 2004 edition (online, CSN website):

Peritoneal Kt/V should be maintained at a minimum of 1.7 per week in all patients on chronic PD (CAPD and APD) once residual renal GFR is less than 4 mls/min (renal creatinine clearance < 40 liters/week or renal Kt/V < 1.0 per week). Peritoneal Kt/V may be maintained at lower values (between 1.0 and 1.7 per week) in patients with a recently measured GFR greater than 4 mls/minute (renal creatinine clearance > 40 liters per week or renal Kt/V greater than 1.0 per week) provided there is ongoing monitoring at 2 month intervals of residual GFR.

Rationale:

A well done, randomized controlled trial showed no outcome benefit for patients receiving a mean, weekly peritoneal Kt/V (pKt/V) of 2.12 as compared to 1.62 (1)
Another randomized controlled trial showed outcome benefits for a total weekly Kt/V of 1.7 to 2.0 as compared to total weekly Kt/V greater than 2.0 but did show a possible benefit for 1.7 to 2.0 over 1.5 to 1.7 (2)
Prospective cohort and retrospective analyses show no survival benefit for higher pKt/V levels within the usual therapeutic range (3,4,5)
The survival implications of pKt/V and residual renal Kt/V (rKt/V) are very different and the former cannot replace the latter on a one-to-one basis in its effect on outcomes
Residual renal clearance by any method of measurement [including glomerular filtration rate (GFR) as estimated by a mean of renal urea and creatinine clearance] is a strong predictor of patient survival on PD (1,3,4,5,6)
Increases in peritoneal clearance have economic and lifestyle costs, and may be associated with greater mechanical discomfort (1,2,7)
There is no high grade clinical evidence supporting higher clearance targets for automated PD (APD) compared to continuous ambulatory PD (CAPD)
A modest safety margin should be added on to any evidence based peritoneal clearance target in order to protect patients from the risk of “underdialysis”

References:

Paniagua R, Amato D, Vonesh E, et al. Effects of Increased peritoneal clearances on Mortality rates in Peritoneal Dialysis: ADEMEX, a Prospective, Randomized, Controlled Trial. J Am Soc Nephrol 2002;13:1307-1320.
Lo WK, Ho YW, Li CS et al. Effect of Kt/V on survival and clinical outcome in a randomized prospective study. Kidney Int 2003 64:649-56.
Canada-USA (CANUSA) Peritoneal Dialysis Study Group: Adequacy of Dialysis in Nutrition in Continuous Peritoneal Dialysis: Association with Clinical Outcomes. J Am Soc Nephrol 1996; 7:198-207.
Diaz-Buxo JA, Lowrie EG, Lew NL, Zhang SM, Zhu X, Lazarus JM. Associates of mortality among peritoneal dialysis patients with special reference to peritoneal transport states and solute clearance. Am J Kidney Dis 1999; 33:523-534.
Rocco M, Souci JM, Pastan S, McClellan WM. Peritoneal dialysis adequacy and risk of death. Kidney Int. 2000; 58:446-457.
Bargman JM, Thorpe KE, Churchill DN, et al. Relative Contribution of Residual Renal Function and Peritoneal Clearance to Adequacy of Dialysis: A Reanalysis of the CANUSA study. J Am Soc Nephrol 2001, 12:2158-2162.
Blake PG, Floyd J, Spanner E, Peters K. How much extra does “adequate” peritoneal dialysis cost? Perit Dial Int 1996;16 (Suppl 1):S171-5.