Preservation of residual renal function in dialysis patients: Effects of dialysis-technique-related factors

Objectives: Residual renal function (RRF) is of paramount importance to dia lysis adequacy, morbidity, and mortality, particularly for long-term contin uous ambulatory peritoneal dialysis (CAPD) patients. Residual renal functio n seems to be better preserved in patients on CAPD than in hemodialysis (HD ) patients. We analyzed RRF in 45 patients with end-stage renal disease (ES RD), commencing either CAPD or HD, to prospectively define the time course of the decline in RRF and to evaluate dialysis-technique-related factors su ch as cardiovascular stability and bioincompatibility. Study Design: Single-center prospective investigation in parallel design wi th matched pairs. Materials: Fifteen patients starting CARD and 15 matched pairs of patients commencing HD were matched according to cause of renal failure and RRF. Hem odialysis patients were assigned to two dialyzer membranes differing marked ly in their potential to activate complement and cells (bioincompatibility) . Fifteen patients were treated exclusively with the cuprophane membrane (b ioincompatible) and the other 15 patients received HD with the high-flux po lysulfone membrane (biocompatible). Measurements: Residual renal function was determined at initiation of dialy tic therapy and after 6, 12, and 24 months. Dry weight (by chest x ray and diameter of the vena cava) was closely recorded throughout the study, and t he number of hypotensive episodes counted. Results: Residual renal function declined in both CARD and HD patients, alt hough this decline was faster in HD patients (2.8 mL/minute after 6 months and 3.7 mL/min after 12 months) than in CAPD patients (0.6 mL/min and 1.4 m L/min after 6 and 12 months respectively). It declined faster in patients w ith bioincompatible than with biocompatible HD membranes (3.6 mL/min vs 1.9 mL/min after 6 months). Eleven percent of the HD sessions were complicated by clinically relevant blood pressure reductions, but there were no differ ences between the two dialyzer membrane groups. None of the CAPD patients h ad documented hypotensive episodes. None of the study patients suffered sev ere illness or received nephrotoxic antibiotics or radiocontrast media. Conclusions:The better preservation of RRF in stable CARD patients correspo nded with greater cardiovascular stability compared to HD patients, indepen dently of the membrane used. Furthermore, there was a significantly higher preservation of RRF in HD patients on polysulfone versus cuprophane membran es, indicating an additional effect of biocompatibility, such as less gener ation of nephrotoxic substances by the membrane. Thus, starting ESRD patien ts on HD prior to elective CARD should be avoided for better preservation o f RRF.