Rationale for Guideline Kt/V urea Targets for Peritoneal Dialysis

Peritoneal Dialysis Adequacy Targets

Kt/V urea Targets for Peritoneal Dialysis

Contribution from UK Renal Association Clinical Practice Guidelines Committee

Source: The 3rd edition of the Renal Association “Standards” states:

A total weekly creatinine clearance (dialysis + residual renal function) of greater than 50 l/week/1.73 m2 and/or a weekly dialysis Kt/V urea of greater than 1.7, checked eight weeks after beginning dialysis, are minima. Higher targets are desirable especially for high average and high transporters and APD patients. (Evidence level B)

In the updated 4th edition (now called the Renal Association Clinical Practice Guidelines) this statement has been only slightly modified and the evidence level upgraded:

A combined urinary and peritoneal Kt/Vurea of 1.7/week or a creatinine clearance of 50L/week/1.73m2 should be considered as minimal treatment doses. The dose should be increased in patients experiencing uraemic symptoms (Evidence level A).

Rationale: Two randomised controlled trials (ADEMEX and Hong Kong) have evaluated the impact of peritoneal solute clearances on clinical endpoints [1, 2]. Neither found that an increase of peritoneal Kt/Vurea >1.7 was associated with an improvement in survival. Only one of these studies (ADEMEX) measured creatinine clearance, patients in the control group achieved an average peritoneal creatinine clearance of 46L/1.73m2/week and a total (urine plus renal) of 54L/1.73m2/week. In setting a recommendation for minimal peritoneal clearances, to be achieved in anuric patients, the previous Renal Association guideline of Kt/V > 1.7 and creatinine clearance >50L/1.73m2/week is supported by both the randomised and observational data and the evidence rating has therefore been upgraded. In the Hong Kong study, patients randomised to a Kt/V <1.7 had a significantly higher drop out rate, more clinical complications and more severe anaemia although their mortality was no different. Drop out due to uraemia or death associated with hyperkalaemia and acidosis was significantly more common in the control patients in the ADEMEX study [1]. One observational longitudinal study demonstrated that patients develop malnutrition once the Kt/V falls below 1.7 with a three-fold increase in the death rate [3]. The vast majority of PD patients will be able to reach these clearance targets, especially if APD is employed [4].

These guidelines must however be viewed as recommendations for minimal overall clearance. In patients with residual renal function, renal clearance can be subtracted from the peritoneal clearance with confidence that the value of equivalent renal clearances is greater. Equally, in patients achieving these clearances but experiencing uraemic symptoms, or failing to achieve adequate acid base balance then the dialysis dose should be increased.

References:

1. Paniagua R, Amato D, Vonesh E, Correa-Rotter R, Ramos A, Moran J, Mujais S: Effects of Increased Peritoneal Clearances on Mortality Rates in Peritoneal Dialysis: ADEMEX, a Prospective, Randomized, Controlled Trial. J Am Soc Nephrol 13:1307-1320., 2002
2. Lo WK, Ho YW, Li CS, Wong KS, Chan TM, Yu AW, Ng FS, Cheng IK: Effect of Kt/V on survival and clinical outcome in CAPD patients in a randomized prospective study. Kidney Int 64:649-656., 2003
3. Davies SJ, Phillips L, Russell L, Naish PF, Russell GI: An analysis of the effects of increasing delivered dialysis treatment to malnourished peritoneal dialysis patients. Kidney Int 57:1743-1754, 2000
4. Brown EA, Davies SJ, Heimburger O, Meeus F, Mellotte G, Rosman J, Rutherford P, Van Bree M: Adequacy targets can be met in anuric patients by automated peritoneal dialysis: baseline data from EAPOS. Perit Dial Int 21:S133-137., 2001

Prepared on behalf of the UK Renal Association Clinical Practice Guidelines Committee by Simon Davies and David Wheeler (Chairman).