TOWARD TARGETS FOR INITIATION OF CHRONIC DIALYSIS

Objectives: To better define the targets for initiation of chronic dia lysis, we compared the relationship between the normalized protein equ ivalent of nitrogen appearance (nPNA, g/kg standard weight/day) and we ekly urea clearance (Kt) normalized to total body water (V) in predial ysis chronic renal failure (CRF) patients and in patients on continuou s ambulatory peritoneal dialysis (CAPD) and hemodialysis (HD). We also studied the relationships of other nutritional parameters to weekly K t/V-urea in CRF patients. Design: This cross-sectional study was a pro spective observational design meant to study each patient once. Settin g: The University Hospital and Clinics and Harry S. Truman VA Medical Center, Columbia, Missouri. Patients: Forty-five consecutive predialys is CRF patients were enrolled and the results compared with patients o n CAPD and HD. Results: In CRF, the nPNA calculated from urea appearan ce correlated with the weekly Kt/V-urea (r = 0.57, p < 0.0001) and, us ing exponential best-fit, nPNA = 1.217 x (1 - e(-0.769Kt/V)). This exp onential relationship was similar to that for CAPD and both were diffe rent from that in patients on HD. Likewise, nPNAs, calculated from Kje ldahl nitrogen output, and weekly Kt/V-urea were correlated (r = 0.37, p = 0.014) and, using exponential best-fit, nPNA = 1.102(1 - e(-0.867 Kt/V)), similar to the relationship in patients on CAPD. Evidence is p resented that these relationships are not explained only by mathematic al coupling. There was a significant correlation between the weekly Kt /V-urea and 24-hour urinary creatinine excretion. Conclusions: The fin dings suggest that in CRF, as in CAPD, a weekly Kt/V-urea less than 2. 0 is likely to be associated with a nPNA less than 0.9 g/kg standard w eight. In CRF patients, initiation of chronic dialysis should be consi dered if weekly renal Kt/V-urea falls below 2.0 and a nPNA greater tha n 0.8 is desired.