Comparison of volume overload with cycler-assisted versus continuous ambulatory peritoneal dialysis

BACKGROUND AND OBJECTIVES

Cycler-assisted peritoneal dialysis (CCPD) has been associated with decreased sodium removal compared with continuous ambulatory peritoneal dialysis (CAPD) as a result of peritoneal sodium sieving during the short dwells that are associated with CCPD. This may have adverse consequences for management of extracellular fluid volume (ECFV). This study compared ECFV in patients who received CAPD or CCPD; CCPD dwell times were maximized by limiting the number of exchanges, and the use of icodextrin for the long daytime dwells was widespread.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

This was an observational, cross-sectional study of 158 prevalent patients (90 CAPD, 68 CCPD). Demographic data, blood work, and 24-h dialysate and urine samples were collected from all participants between January 2004 and July 2006. They subsequently underwent assessment of ECFV by multifrequency bioimpedance spectroscopy analysis. Multivariate analysis was used to determine the relationship between peritoneal dialysis modality and ECFV. Potential cofounders including age, comorbidity, time on dialysis, residual renal function, and icodextrin use were identified a priori.

RESULTS

There were no differences in BP, use of antihypertensive medications, or the presence of peripheral edema between CAPD and CCPD patients. Similarly, there was no difference in the ratio of ECFV to total body water between CAPD (51.8%) and CCPD (51.9%) patients (P = 0.929).

CONCLUSIONS

There is no difference in BP, sodium removal, or volume control in patients who use a contemporary approach to CCPD that uses fewer night cycles and liberalizes the use of icodextrin when compared with CAPD.

Treatment time, chronic inflammation, and hemodynamic stability: the overlooked parameters in hemodialysis quantification

Decades after the introduction of chronic maintenance hemodialysis, the optimal means of quantifying dialysis dose remains controversial. Differences of opinion in the international dialysis community lead to substantial diversity in everyday clinical practice. Several studies suggest that the well-recognized international mortality differences in hemodialysis populations may result from these divergent approaches to dialysis care. One of the main areas of divergence is the different degree of reliance on dialysis clearance when prescribing dialysis. The "clearance approach" implies that treatment quality is primarily dependent on efficient removal of uremic toxins as estimated by dialytic urea clearance. Urea can be rapidly removed by high efficiency dialysis in a relatively short time. The main alternative to this strategy is the "time approach" based on the recognition that longer or more frequent dialysis provides benefits beyond increasing urea removal. Some of the putative benefits are more effective volume and blood pressure control, better maintenance of hemodynamic stability because of slower ultrafiltration and removal of uremic toxins that do not behave like urea. Recently, chronic inflammation has been proposed to be an important predictor of outcome in dialysis patients. Inflammatory markers are commonly elevated in chronic renal failure and levels of these seem to correlate with malnutrition, maintenance of residual renal function, and volume control. The relationships between dialysis clearance, treatment time, chronic inflammation, volume control, and hemodynamic stability are explored in this review. We propose that a better understanding of these complex relationships may provide opportunities for improving outcomes of maintenance hemodialysis patients.

Dry weight: sine qua non of adequate dialysis

Attainment of dry weight remains a major clinical problem and challenge in current-day dialysis therapies. The vicious cycle of fluid overload and inadequate intradialytic fluid removal with hypotensive episodes, and subsequent poor clinical outcomes, is reinforced by excessive salt accumulation orally as well as during dialysis. Negligence in recognizing the importance of fluid status in dialysis prescriptions with shortened times has contributed to the prevalence of overhydration. The treatment of this problem is exacerbated by the lack of adequate methods to diagnose and manage it. The recent findings of improved fluid status and prognosis with salt restriction, individualized dialysate sodium concentrations, and prolonged hemodialysis times when necessary with well-tolerated fluid removal rates show the path to prolonging survival of dialysis populations. The ongoing development of techniques permitting accurate assessment of hydration status, including those based on bioimpedance analysis, will provide an efficient tool in these efforts.