UNRESOLVED ISSUES IN DIALYSIS: Revisiting the Peritoneal Dialysis Dose

The question of the minimum dose for adequate peritoneal dialysis has been settled following the publication of two randomized controlled studies and a number of nonrandomized studies. This review summarizes these studies, concluding that these studies support a weekly total Kt/V of 1.7 as the minimum dose, with careful observation for symptoms or signs of uremia and adjustment of the clearance as indicated.

Peritoneal dialysis adequacy and risk of death

The debate on the relationship between small solute clearance and patient outcome on peritoneal dialysis has intensified in the past year with the publication or presentation of a number of important new studies. Previous studies had found a correlation between clearances and subsequent patient survival. However, this effect was all accounted for by residual renal clearance. The failure to detect an independent effect of peritoneal clearance on outcomes had been attributed to a lack of well-done studies with sufficient variation in peritoneal clearance to detect such an effect. New prospective and randomized studies suggest, however, that the relationship between peritoneal clearance and outcome is weak or absent within the usual dose ranges delivered in clinical practice. Existing clearance targets may need to be reviewed.

Multicenter cross-sectional study for dialysis dose and physician's subjective judgment in Japanese peritoneal dialysis patients. Group for the Water and Electrocyte Balance Study in CAPD

The purpose of this study was to investigate the state of dialysis and nutrition among Japanese peritoneal dialysis (PD) patients. Two hundred thirty-nine Japanese PD patients from 21 centers, 79 female and 160 male, were evaluated to determine their status of dialysis and nutrition. Mean age of the patients was 50 years; mean duration on PD, 4.2 years; mean body weight, 58 kg; and body surface area (BSA), 1.61 m(2). Sixty-three percent of the patients had no residual renal function. Mean daily delivered volume was 6.9 L for female continuous ambulatory peritoneal dialysis (CAPD), 8.1 L for male CAPD, 10.5 L for female automated peritoneal dialysis (APD), and 10.7 L for male APD. Total (dialysis and kidney) mean weekly values for creatinine clearance (Ccr), Kt/V, and beta2 microglobulin (beta2MG) clearance were 56 L/1.75 m(2), 1.80, and 11 L/1.73 m(2), respectively. Fifty percent of the patients who had no residual renal function (RRF) and 17% of the patients with RRF did not achieve 50 L/wk/1.73 m(2) of Ccr. With regard to nutritional parameters, mean values for plasma total protein, serum albumin, and normalized protein catabolic rate (nPCR) were 6.5 g/dL, 3.6 g/dL, and 0.97 g/kg BW/d. Mean daily protein loss was 5.8 g. Although a significant number of patients did not achieve 50 or 60 L/wk/1.73 m(2) of Ccr, the physicians determined that 72% of the patients received adequate dialysis and 71% were well nourished according to clinical and laboratory features. In conclusion, the daily prescribed volume and the delivered dialysis dose were lower than expected. The discrepancy between the actual delivered dialysis dose and the physicians' evaluation should be explored in the future.

Morbidity and mortality in redefining adequacy of peritoneal dialysis: a step beyond the National Kidney Foundation Dialysis Outcomes Quality Initiative

The National Kidney Foundation Dialysis Outcomes Quality Initiative (NKF-DOQI) Peritoneal Dialysis (PD) Adequacy Work Group intentionally limited the scope of its work to address adequacy in terms of small-solute removal. This decision was based on the need for rigorous evidence and that mortality is the most objective parameter in the literature. This review attempts to more broadly redefine the concept of the adequacy of PD, particularly as it relates to the most common general medical problems that PD patients experience; namely, cardiovascular disease and malnutrition. Whereas we are sensitive to the developmental process of the NKF-DOQI, we are critical that the definition of adequacy may be too narrow, leading clinicians to overlook other important morbidities. We have reiterated the evidence that suggests a weekly solute clearance (Kt/Vurea) of 1.7 or greater is associated with better patient survival. The arguments to target a greater Kt/Vurea of 2.0 are challenged, yet the concept is ultimately supported. Because cardiovascular disease is the cause of death in half of all patients with end-stage renal disease, dialysis adequacy must be defined, in part, by the potential of that therapy to diminish cardiovascular maladies. Blood pressure, volume, left ventricular hypertrophy, and dyslipidemias are discussed in this context. Lastly, assumptions that increasing total solute clearance leads to improved nutrition in PD patients are challenged. We have attempted to expand on what the NKF-DOQI did not include, and we urge the dialysis community to seek the answers to the many controversies that remain. We need to redefine the adequacy of PD in a holistic manner and find outcome parameters that are not as final as death.