Relationships between dialysis quantification and normalized protein catabolic rate in peritoneal dialysis

Normalized protein catabolic rates (NPCR) and urea clearances (Kt/V urea) correlate significantly in peritoneal dialysis suggesting that the adequacy of dietary protein intake and dialysis dose are interrelated. However, both of these calculated parameters are mathematical functions of the normalized urea appearance rate (GN). NPCR, GN, Kt/V urea, total creatinine clearance, residual renal clearance, and peritoneal urea and creatinine clearances were determined in 29 stable peritoneal dialysis patients with no history of recent peritonitis or other catabolic illness. Multiple linear regression analysis showed that NPCR correlated closely with both GN (r = 0.96; p < 0.0001) and Kt/V urea (r = 0.77; p < 0.0001), whereas GN also correlated with Kt/V urea (r = 0.66; p < 0.0001). Total weekly creatinine clearances rather than Kt/V urea should be utilized in peritoneal dialysis to permit independent estimations of dialysis dose and NPCR, since both Kt/V and NPCR are related closely to GN. Total weekly creatinine clearances correlated with NPCR (r = 0.59; p < 0.0002), which supports the hypothesis that dietary protein intake is dependent on the delivered dialysis dose.