Effects of reducing the lactate and glucose content of PD solutions on the peritoneum. Is the future GLAD?

Regimen-related Mortality Risk in Patients Undergoing Peritoneal Dialysis Using Hypertonic Glucose Solution: A Retrospective Cohort Study

OBJECTIVES

The main purpose of this study was to quantify the risk of mortality linked to various regimens of hypertonic peritoneal dialysis (PD) solution.

METHODS

A retrospective cohort study of patients using home-based PD was carried out. The prescribed regimen of glucose-based PD solution for all patients, determined on the basis of their individual conditions, was extracted from their medical chart records. The primary outcome was death. The treatment regimens were categorized into 3 groups according to the type of PD solution used: original PD (1.5% glucose), shuffle PD (1.5 and 2.5% glucose), and serialized PD (2.5 and 4.5% glucose). Multivariate analysis (using the Weibull model) was applied to comprehensively examine survival probabilities related to the explanatory variable, while adjusting for other potential confounders.

RESULTS

Of 300 consecutive patients, 38% died over a median follow-up time of 30 months (interquartile range: 15-46 months). Multivariate analysis showed that a treatment regimen with continued higher-strength PD solution (serialized PD) resulted in a lower survival rate than when the conventional strength solution was used (adjusted hazard ratio, 2.6; 95% confidence interval, 1.6 to 4.6, p<0.01). Five interrelated risk factors (age, length of time on PD, hemoglobin levels, albumin levels, and oliguria) were significant predictors contributing to the outcome.

CONCLUSIONS

Frequent exposure to high levels of glucose PD solution significantly contributed to a 2-fold higher rate of death, especially when hypertonic glucose was prescribed continuously.

New Insights into the Effects of Chronic Kidney Failure and Dialysate Exposure on the Peritoneum

♦ INTRODUCTION: Chronic uremia and the exposure to dialysis solutions during peritoneal dialysis (PD) induce peritoneal alterations. Using a long-term peritoneal exposure model, we compared the effects of chronic kidney failure (CKD) itself and exposure to either a 'conventional' or a 'biocompatible' dialysis solution on peritoneal morphology and function. ♦ METHODS: Wistar rats (Harlan, Zeist, the Netherlands) were grouped into: normal kidney function (NKF), CKD induced by 70% nephrectomy, CKD receiving daily peritoneal infusions with 3.86% glucose Dianeal (CKDD), or Physioneal (both solutions from Baxter Healthcare, Castlebar, Ireland) (CKDP). At 16 weeks, a peritoneal function test was performed, and histology, ultrastructure, and hydroxyproline content of peritoneal tissue were assessed. ♦ RESULTS: Comparing CKD with NKF, peritoneal transport rates were higher, mesothelial cells (MC) displayed increased number of microvilli, blood and lymph vasculature expanded, vascular basal lamina appeared thicker, with limited areas of duplication, and fibrosis had developed. All alterations, except lymphangiogenesis, were enhanced by exposure to both dialysis fluids. Distinct MC alterations were observed in CKDD and CKDP, the latter displaying prominent basolateral protrusions. In addition, CKDP was associated with a trend towards less fibrosis compared to CKDD. ♦ CONCLUSIONS: Chronic kidney failure itself induced peritoneal alterations, which were in part augmented by exposure to glucose-based dialysis solutions. Overall, the conventional and biocompatible solutions had similar long-term effects on the peritoneum. Importantly, the latter may attenuate the development of fibrosis.

The Association of Effluent Ca125 with Peritoneal Dialysis Technique Failure

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BACKGROUND AND OBJECTIVES

Cancer antigen 125 (CA125) reflects the mesothelial cell mass lining the peritoneal membrane in individual patients. A decline or absence of mesothelial cells can be observed with duration of peritoneal dialysis (PD) therapy. Technique failure due to peritoneal membrane malfunction becomes of greater importance after 2 years of PD therapy in comparison to the initial period. In this study, we aimed to investigate the association between effluent CA125 and technique survival in incident PD patients with a PD therapy period of at least 2 years. ♦

METHODS

Within the Netherlands Cooperative Study on the Adequacy of Dialysis (NECOSAD), a Dutch multicenter cohort including 2,000 incident dialysis patients, we identified all PD patients who developed technique failure after 2 years of PD therapy and randomly selected a number of them as cases in a nested case-control study. Controls were PD patients matched on follow-up time without technique failure. Cases and controls were included if they had a dialysate specimen available within 24 ± 6 months of PD therapy for retrospective CA125 determinations. Odds ratios for technique failure related to CA125 were estimated. We used a prospective cohort with incident PD patients from the Academic Medical Center-University of Amsterdam (AMC) for replication of effect estimates. In these patients, absolute risk of technique failure was estimated and related to effluent CA125 levels. ♦

RESULTS

A total of 38 PD patients were selected from the NECOSAD cohort. From the AMC cohort as replication cohort, 91 PD patients were included. Incidence rates of PD technique failure per 100 patient-years were 16.3 in the NECOSAD cohort and 12.9 in the AMC cohort. In both study populations CA125 levels below 12 - 14 kU/L were associated with an increased risk for technique failure. Technique survival rates in the AMC were 87% in patients with levels of CA125 above 12.1 kU/L and 65% for those with CA125 levels below this threshold after a maximum 5-year follow-up. ♦

CONCLUSIONS

Patients with high CA125 levels after at least 2 years of PD therapy tend to have better technique survival than patients with low CA125 levels. These results support the importance of effluent CA125 as a risk factor for dropout in long-term PD therapy.

Peritoneal dialysis: from bench to bedside

Peritoneal dialysis was first employed in patients with acute renal failure in the 1940s and since the 1960s for those with end-stage renal disease. Its popularity increased enormously after the introduction of continuous ambulatory peritoneal dialysis in the end of 1970s. This stimulated both clinical and basic research. In an ideal situation, this should lead to cross-fertilization between the two. The present review describes two examples of interactions: one where it worked out very well and another where basic science missed the link with clinical findings. Those on fluid transport are examples of how old physiological findings on absorption of saline and glucose solutions were adopted in peritoneal dialysis by the use of glucose as an osmotic agent. The mechanism behind this in patients was first solved mathematically by the assumption of ultrasmall intracellular pores allowing water transport only. At the same time, basic science discovered the water channel aquaporin-1 (AQP-1), and a few years later, studies in transgenic mice confirmed that AQP-1 was the ultrasmall pore. In clinical medicine, this led to its assessment in patients and the notion of its impairment. Drugs for treatment have been developed. Research on biocompatibility is not a success story. Basic science has focussed on dialysis solutions with a low pH and lactate, and effects of glucose degradation products, although the first is irrelevant in patients and effects of continuous exposure to high glucose concentrations were largely neglected. Industry believed the bench more than the bedside, resulting in 'biocompatible' dialysis solutions. These solutions have some beneficial effects, but are evidently not the final answer.

Can effluent matrix metalloproteinase 2 and plasminogen activator inhibitor 1 be used as biomarkers of peritoneal membrane alterations in peritoneal dialysis patients?

BACKGROUND

Peritoneal effluent contains clinically relevant substances derived from intraperitoneal production or transperitoneal transport, or both. The glycoproteinase matrix metalloproteinase 2 (MMP-2) cleaves denatured collagen and complements other collagenases in the degradation of fibrillar collagens. Elevated intraperitoneal levels of plasminogen activator inhibitor 1 (PAI-1) have been demonstrated to be present in patients with intra-abdominal adhesions. The aim of the present study was therefore to investigate the potential for effluent MMP-2 and PAI-1 to be used as markers of the development of peritoneal alterations. In addition, MMP-2 was analyzed in previously frozen effluent samples from a uremic rat model, in which data concerning the severity of peritoneal fibrosis were available.

METHODS

This prospective, single-center cohort study included 86 incident peritoneal dialysis (PD) patients. All patients were treated solely with biocompatible dialysis solutions and underwent a standard peritoneal permeability analysis (SPA). The presence of local MMP-2 and PAI-1 production and the relationships between those markers and peritoneal transport parameters were analyzed. Furthermore, effluent interleukin 6 was analyzed as a marker of local inflammation.

RESULTS

Median effluent levels of 21.4 ng/mL for MMP-2 and 0.9 ng/mL for PAI-1 were found. The median dialysate appearance rates were 218.8 ng/min for MMP-2 and 9.6 ng/min for PAI-1. Local peritoneal production averaged 90% of effluent MMP-2 concentration and 74% of effluent PAI-1 concentration. Furthermore, correlations between peritoneal transport parameters and MMP-2 and PAI-1 were observed. Longitudinal follow-up showed no change for MMP-2 (p = 0.37), but a tendency for PAI-1 to increase with the duration of PD (p < 0.001). In rats, a significant relationship was present between the extent of peritoneal fibrosis and the appearance rate of MMP-2 (r = 0.64, p = 0.03).

CONCLUSIONS

The foregoing data illustrate the potential of effluent MMP-2 and PAI-1 as biomarkers of peritoneal modifications, especially fibrosis; however, the components of peritoneal transport and local production should be clearly distinguished in every patient.

Peritoneal changes in patients on long-term peritoneal dialysis

Long-term peritoneal dialysis can lead to morphological and functional changes in the peritoneum. Although the range of morphological alterations is known for the peritoneal dialysis population as a whole, these changes will not occur in every patient in the same sequence and to the same extent. Longitudinal studies are therefore required to help identify which patients might develop the changes. Although longitudinal studies using peritoneal biopsies are not possible, analyses of peritoneal effluent biomarkers that represent morphological alterations could provide insight. Longitudinal studies on peritoneal transport have been performed, but follow-up has often been too short and an insufficient number of parameters have been investigated. This Review will firstly describe peritoneal morphology and structure and will then focus on peritoneal effluent biomarkers and their changes over time. Net ultrafiltration will also be discussed together with the transport of small solutes. Data on the peritoneal transport of serum proteins show that serum protein levels do not increase to the same extent as levels of small solutes with long-term peritoneal dialysis. Early alterations in peritoneal transport must be distinguished from alterations that only develop with long-term peritoneal dialysis. Early alterations are related to vasoactive mediators, whereas later alterations are related to neoangiogenesis and fibrosis. Modern peritoneal dialysis should focus on the early detection of long-term membrane alterations by biomarkers--such as cancer antigen 125, interleukin-6 and plasminogen activator inhibitor 1--and the improved assessment of peritoneal transport.

Neutral solution low in glucose degradation products is associated with less peritoneal fibrosis and vascular sclerosis in patients receiving peritoneal dialysis

BACKGROUND

The effects of novel biocompatible peritoneal dialysis (PD) solutions on human peritoneal membrane pathology have yet to be determined. Quantitative evaluation of human peritoneal biopsy specimens may reveal the effects of the new solutions on peritoneal membrane pathology. ♢

METHODS

Peritoneal specimens from 24 PD patients being treated with either acidic solution containing high-glucose degradation products [GDPs (n = 12)] or neutral solution with low GDPs (n = 12) were investigated at the end of PD. As controls, pre-PD peritoneal specimens, obtained from 13 patients at PD catheter insertion, were also investigated. The extent of peritoneal fibrosis, vascular sclerosis, and advanced glycation end-product (AGE) accumulation were evaluated by quantitative or semi-quantitative methods. The average densities of CD31-positive vessels and podoplanin-positive lymphatic vessels were also determined. ♢

RESULTS

Peritoneal membrane fibrosis, vascular sclerosis, and AGE accumulation were significantly suppressed in the neutral group compared with the acidic group. The neutral group also showed lower peritoneal equilibration test scores and preserved ultrafiltration volume. The density of blood capillaries, but not of lymphatic capillaries, was significantly increased in the neutral group compared with the acidic and pre-PD groups. ♢

CONCLUSIONS

Neutral solutions with low GDPs are associated with less peritoneal membrane fibrosis and vascular sclerosis through suppression of AGE accumulation. However, contrary to expectation, blood capillary density was increased in the neutral group. The altered contents of the new PD solutions modified peritoneal membrane morphology and function in patients undergoing PD.

Renal replacement therapy in ICU

Diagnosing and managing critically ill patients with renal dysfunction is a part of the daily routine of an intensivist. Acute kidney insufficiency substantially contributes to the morbidity and mortality of critically ill patients. Renal replacement therapy (RRT) not only does play a significant role in the treatment of patients with renal failure, acute as well as chronic, but also has spread its domains to the treatment of many other disease conditions such as myaesthenia gravis, septic shock and acute on chronic liver failure. This article briefly outlines the role of renal replacement therapy in ICU.

Future technologies and techniques in peritoneal dialysis-opportunities and challenges ahead

In the last 5 years, we have started to witness the emergence of new technologies and techniques that offer the potential for improved patient outcomes but which often still lack clinical demonstration and/or confirmation in well-designed, multicentre studies. These include biocompatible solutions, glucose sparing regimens, low-sodium solutions, bimodal solution formulations and continuous flow peritoneal dialysis (CFPD). This review discusses the potential benefits ascribable to each of these technologies and an analysis of the challenges that have to be surmounted before anyone of these candidate technologies can be declared as established. The demonstration of either hard clinical endpoints or validated surrogate endpoints is very feasible in terms of sample size requirements for some outcome measures, such as preservation of RRF, but will be much more challenging for other endpoints such as preservation of UF capacity.