Recirculation peritoneal dialysis with sorbent Redy cartridge

Evidence on continuous flow peritoneal dialysis: A review

Clinical application of continuous flow peritoneal dialysis (CFPD) has been explored since the 1960s, but despite anticipated clinical benefits, CFPD has failed to gain a foothold in clinical practice, among others due to the typical use of two catheters (or a dual-lumen catheter) and large dialysate volumes required per treatment. Novel systems applying CFPD via the existing single-lumen catheter using rapid dialysate cycling may solve one of these hurdles. Novel on-demand peritoneal dialysate generation systems and sorbent-based peritoneal dialysate regeneration systems may considerably reduce the storage space for peritoneal dialysate and/or the required dialysate volume. This review provides an overview of current evidence on CFPD in vivo. The available (pre)clinical evidence on CFPD is limited to case reports/series with inherently nonuniform study procedures, or studies with a small sample size, short follow-up, and no hard endpoints. Small solute clearance appears to be higher in CFPD compared to conventional PD, in particular at dialysate flows ≥100 mL/min using two single-lumen catheters or a double-lumen catheter. Results of CFPD using rapid cycling via a single-lumen catheter are too preliminary to draw any conclusions. Continuous addition of glucose to dialysate with CFPD appears to be effective in reducing the maximum intraperitoneal glucose concentration while increasing ultrafiltration efficiency (mL/g absorbed glucose). Patient tolerance may be an issue since abdominal discomfort and sterile peritonitis were reported with continuous circulation of the peritoneal dialysate. Thus, well-designed clinical trials of longer duration and larger sample size, in particular applying CFPD via the existing catheter, are urgently required.

Continuous Flow Peritoneal Dialysis: Assessment of Fluid and Solute Removal in a High-Flow Model of “Fresh Dialysate Single Pass”

♦ Background

Growing concern over the limited capacity of the peritoneal dialysis (PD) system has revived interest in continuous flow peritoneal dialysis (CFPD), a modality in which continuous circulation of PD fluid is maintained at a high flow rate using two separate catheters or one dual-lumen catheter. The CFPD regimen contrasts the “inflow/outflow” regimen, which requires specific times devoted to filling and draining the peritoneum via a single-lumen catheter. Historical data established CFPD capabilities in providing higher solute clearance and ultrafiltration rate (UFR) using either an open loop system with a single pass of fresh PD fluid, or various external purifications of the spent dialysate.

♦ Objective

To compare, in patients with various peritoneal transport patterns, fluid and solute removal achieved during a standardized program of CFPD versus two control schedules: nightly intermittent peritoneal dialysis (NIPD) and nightly tidal peritoneal dialysis (NTPD). This study focused on small solute clearances and UFR using only isotonic PD solution (Dianeal PD1 1.36%; Baxter Healthcare, Castlebar, Ireland). The model of fresh dialysate, single pass, was used to optimize solute gradients and to characterize the impact of a continuous flow regimen on peritoneal transport characteristics.

♦ Methods

In a crossover trial, 4-hour CFPD sessions were performed at a fixed dialysate flow rate (100 mL/minute) in 5 patients being treated with automated PD. A hemofiltration monitor (BM25; Baxter Healthcare, Brussels, Belgium) was adapted to the CFPD technique. The peritoneal cavity was filled through a temporary second catheter and simultaneously drained using the permanent peritoneal access. Fluid and solute removal were compared to data obtained from a control period based on 8-hour sessions of NIPD or NTPD using 13 L of isotonic dialysate.

♦ Results

High-flow CFPD enhanced the diffusive transport coefficient compared with the alternative flow regimen in patients ranging from low to high transporters. Weekly creatinine clearance increased from 36.9 L (22.3 – 49.6 L) and 37.3 L (27.5 – 45.0 L) with NIPD and NTPD respectively, to 74.9 L (42.3–107.5 L) with CFPD. Mean UFR was 2.44 mL/min with CFPD versus 0.92 and 0.89 mL/min with NIPD and NTPD respectively. The mass transfer area coefficient (MTAC) of creatinine with CFPD was 2.5-fold that obtained from the peritoneal equilibration test data.

♦ Conclusion

Our results confirm that CFPD is highly effective in increasing fluid and solute removal. Furthermore, consistent with historical data, our findings indicate that the enhanced solute transfer is not due only to steeper solute gradients, but also depends on increased MTAC in a wide range of peritoneum transport characteristics.

Inflammatory Response to Sorbent Hemodialysis

Inflammation is common and associated with morbidity and mortality in hemodialysis (HD) patients. Exposure to endotoxin contained in the dialysate may trigger inflammation. Dialysate volume is substantially reduced in sorbent HD compared with standard single-pass dialysis. In this prospective study (Clinicaltrials.gov, number: NCT00788905), we compared the inflammatory response to single-pass and sorbent HD. Patients receiving single-pass HD were studied during 1 week of sorbent HD (Allient system; Renal Solutions, Warrendale, PA) and 1 week of single-pass HD. Patients were dialyzed using high-flux polysulfone dialyzers. Midweek pre- and post-HD serum levels of high-sensitivity C-reactive protein, interleukin (IL)-1β, IL-6, IL-10, interferon gamma, tumor necrosis factor alpha (TNF-α), and eotaxin were determined and their intradialytic change corrected for hemoconcentration during single-pass HD and sorbent HD compared by paired t-test. We enrolled 18 patients, nine completed the study. Although TNF-α decreased during both single-pass and sorbent HD (p < 0.001), none of the other biomarkers changed significantly during HD. We observed no difference between single-pass and sorbent HD. For the markers investigated in this study, there was no difference in the acute intradialytic inflammatory response to single-pass or sorbent HD.

Continuous flow peritoneal dialysis: first experience in children with acute renal failure

BACKGROUND AND OBJECTIVES

Acute renal failure can be treated with different dialysis modalities, depending on patient characteristics and hospital resources. Peritoneal dialysis (PD) can be first choice in situations like hypotension, disturbed coagulation, or difficult venous access. The main disadvantage of PD is the relatively limited efficacy. The aim of this study was to investigate whether continuous flow peritoneal dialysis (CFPD) is a more effective treatment than conventional PD in acute renal failure.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

A pilot study was performed at The Red Cross University Hospital in Cape Town in six patients. Patients were treated with both CFPD and conventional PD for 8 to 16 hours. CFPD was performed with two bedside-placed catheters. After initial filling, dialysate flow rate (100 ml/1.73 m2 per minute) was maintained with an adapted continuous venovenous hemofiltration machine. Ultrafiltration flow rate was set at 2.5 ml/1.73 m2 per minute.

RESULTS

Mean ultrafiltration was 0.20 ml/1.73 m2 per minute with conventional PD versus 1.8 ml/1.73 m2 per minute with CFPD. Mean clearances of urea and creatinine were 5.0 and 7.6 ml/1.73 m2 per minute with conventional PD versus 15.0 and 28.8 ml/1.73 m2 per minute with CFPD, respectively. No complications occurred.

CONCLUSIONS

In this first report of CFPD in six pediatric patients with acute renal failure, CFPD was on average three to five times more effective for urea and creatinine clearance and ultrafiltration than conventional PD, without any complications observed. CFPD has the ability to improve therapy for acute renal failure.

Continuous flow peritoneal dialysis: principles and applications

Continuous flow peritoneal dialysis (CFPD) is a technique of renal replacement therapy (RRT) dating back to the 1960s. Its essential features are a fixed intraperitoneal volume and rapid, continuous movement of dialysis solution into and out of the peritoneal cavity. Inlet and outlet catheters and a means of generating a large volume of sterile dialysate are required. External regeneration of dialysate via conventional hemodialysis (HD) equipment or sorbent technology mitigates the need for large volumes of sterile fluid and makes the technique feasible. Clearance depends on the peritoneal mass transfer coefficient, rate of dialysate flow, and efficiency of external regeneration. Studies to date all demonstrate small solute clearances three to eight times greater than conventional automated peritoneal dialysis (PD). Catheter design is crucial to the clinical success of the technique and will be discussed. Potential applications include daily home dialysis, treatment of acute renal failure in the intensive care unit (ICU), and ultrafiltration of ascites. Clinical experience with the latter will be presented in detail.

Clinical experience with continuous flow and flow-through peritoneal dialysis

Concern over the inherent inefficiency of solute removal by conventional peritoneal dialysis (PD) has led to renewed interest in continuous flow PD (CFPD). We present clinical data from two experiences with CFPD. In the first, two catheters were used to recirculate a fixed intraperitoneal volume through an external circuit comprised of a standard hemodialysis system. The second patient had a dual-lumen PD catheter and was studied during two sessions of flow-through PD (FTPD) using sterile PD solution. Urea clearances with both techniques were around 30 ml/min, which is consistent with data reported in the literature. Significant streaming of dialysate from port to port within the peritoneal cavity limited clearances. CFPD offers a potentially safe and effective alternative to daily or nightly home hemodialysis.

Hybrid dialysis: recirculation peritoneal dialysis revisited

In a crossover trial, eight patients were studied during one treatment each of automated peritoneal dialysis (APD) and hybrid dialysis (HyD). During HyD, a fixed quantity of peritoneal dialysis fluid (PDF) was continuously removed at a flow rate of 141.3 +/- 23. 7 mL/min, dialyzed against the secondary dialysate (250 +/- 53.5 mL/min) generated by the hemodialysis delivery system with single-needle dialysis capability, and the regenerated PDF (PDF(HyD)) was reinfused into the peritoneal cavity. Despite using a smaller volume (6,195 +/- 737 versus 13,321 +/- 1,201 mL; P < 0. 0001) of PDF(HyD) with a lower glucose concentration (729 +/- 562 versus 1,659 +/- 373 mg/dL; P < 0.0001) and osmolality (331 +/- 79 versus 387 +/- 184 mOsm/kg; P < 0.001) during HyD compared with APD (PDF(APD)), weight loss was similar with both treatments (1.4 +/- 1. 0 versus 1.6 +/- 1.2 kg). Lactate levels were lower (3.2 +/- 2.5 versus 11.4 +/- 5.4 mEq/L), but pH (7.5 +/- 1.3 versus 5.6 +/- 0.9; P < 0.001) and bicarbonate concentration (22.6 +/- 8.0 versus 11.9 +/- 7.9 mEq/L; P < 0.0001) were greater in PDF(HyD) than PDF(APD). Although the mean dialysate calcium level was lower (6.0 +/- 0.5 versus 6.9 +/- 1.1 mg/dL; P < 0.001) in PDF(HyD), it was more stable throughout the dialysis compared with PDF(APD). A steeper concentration gradient between the blood and dialysate resulted in greater clearance of urea (26.5 +/- 9.1 versus 11.0 +/- 4.7 mL/min; P = 0.04), creatinine (24.1 +/- 11.4 versus 12.0 +/- 7.9 mL/min; P = 0.03), phosphate (19.2 +/- 4.3 versus 9.8 +/- 7.2 mL/min; P = 0.01), and uric acid (15.6 +/- 6.9 versus 9.1 +/- 2.7 mL/min; P = 0.04) and a greater percentage of reduction in values for blood urea nitrogen (20.7% +/- 7.7% versus 11.6% +/- 5.5%; P = 0.02), serum creatinine (16.1% +/- 5.3% versus 6.6% +/- 3.0%; P < 0.001), phosphate (22.7% +/- 8.9% versus 9.8% +/- 4.5%; P = 0.004), and uric acid (15.8% +/- 2.9% versus 6.3% +/- 3.4%; P < 0.001) during HyD than APD. To conclude, HyD is a novel dialytic technique that uses biocompatible bicarbonate-based dialysate to achieve excellent clearance of uremic toxins and ultrafiltration with minimal glucose load.

Pharmacokinetic problems in peritoneal drug administration: tissue penetration and surface exposure

Both theory and clinical studies demonstrate that drug concentrations in the peritoneal cavity can greatly exceed concentrations in the plasma following intraperitoneal administration. This regional advantage has been associated with clinical activity, including surgically documented complete responses in ovarian cancer patients with persistent or recurrent disease following systemic therapy, and has produced a survival advantage in a recent phase III trial. Two pharmacokinetic problems appear to limit the effectiveness of intraperitoneal therapy: poor tumor penetration by the drug and incomplete irrigation of serosal surfaces by the drug-containing solution. We have examined these problems in the context of a very simple, spatially distributed model. If D is the diffusivity of the drug in a tissue adjacent to the peritoneal cavity and k is the rate constant for removal of the drug from the tissue by capillary blood, the model predicts that (for slowly reacting drugs) the characteristic penetration distance is (D/k)1/2 and the apparent permeability of the surface of a peritoneal structure is (Dk)1/2. The permeability-area product used in classical pharmacokinetic calculations for the peritoneal cavity as a whole is the sum of the products of the tissue-specific permeabilities and the relevant superficial surface areas. Since the model is mechanistic, it provides insight into the expected effect of procedures such as pharmacologic manipulation or physical mixing. We observe that large changes in tissue penetration may be difficult to achieve but that we have very little information on the transport characteristics within tumors in this setting or their response to vasoactive drugs. Enhanced mixing is likely to offer significant potential for improved therapy; however, procedures easily applicable to the clinical setting have not been adequately investigated and should be given high priority. Clinical studies indicate that an increase in irrigated area may be achieved in many patients by individualizing the dialysate volume and consideration of patient position.

Sorbent regeneration of peritoneal dialysate: an approach to ambulatory dialysis

Sorbent regeneration of peritoneal dialysate has been shown to be feasible in experimental and preliminary clinical studies and provides a realistic basis for the optimization of dialysis therapy and the potential development of an ambulatory dialysis system. Peritoneal dialysis efficiency can be significantly enhanced by continuous dialysate flow techniques and the mass transfer of uremic solutes can be theoretically augmented by the increased dialysis time made possible by a wearable design. Further optimization of end stage renal failure therapy may be achieved by the combined use of various methods for blood purification.