Effects of dialysis modality on blood loss, bleeding complications and transfusion requirements in critically ill patients with dialysis-dependent acute renal failure.

Blood loss and bleeding complications may often be observed in critically ill patients on renal replacement therapies (RRT). Here we investigate procedural (i.e. RRT-related) and non-procedural blood loss as well as transfusion requirements in regard to the chosen mode of dialysis (i.e. intermittent haemodialysis [IHD] versus continuous veno-venous haemofiltration [CVVH]). Two hundred and fifty-two patients (122 CVVH, 159 male; aged 61.5±13.9 years) with dialysis-dependent acute renal failure were analysed in a sub-analysis of the prospective randomised controlled clinical trial-CONVINT-comparing IHD and CVVH. Bleeding complications including severity of bleeding and RRT-related blood loss were assessed. We observed that 3.6% of patients died related to severe bleeding episodes (between group P=0.94). Major all-cause bleeding complications were observed in 23% IHD versus 26% of CVVH group patients (P=0.95). Under CVVH, the rate of RRT-related blood loss events (57.4% versus 30.4%, P=0.01) and mean total blood volume lost was increased (222.3±291.9 versus 112.5±222.7 ml per patient, P <0.001). Overall, transfusion rates did not differ between the study groups. In patients with sepsis, transfusion rates of all blood products were significantly higher when compared to cardiogenic shock (all P <0.01) or other conditions. In conclusion, procedural and non-procedural blood loss may often be observed in critically ill patients on RRT. In CVVH-treated patients, procedural blood loss was increased but overall transfusion rates remained unchanged. Our data show that IHD and CVVH may be regarded as equivalent approaches in critically ill patients with dialysis-dependent acute renal failure in this regard.

PD and loss of peritoneal function.

During long-term treatment with peritoneal dialysis both peritoneal membrane structure and function undergo significant changes that not only correlate with the time under treatment, but also with the frequency and severity of infections. In addition, peritoneal dialysis fluid bio-incompatibility may constitute a hazard for the longevity of the peritoneum as the dialysis membrane. In particular, the presence of glucose degradation products may lead to impaired peritoneal cell function as well as to increased protein glycation and peritoneal AGE deposition. Results from recent prospective randomised studies suggest that treatment with new GDP-depleted PD fluids may lead to a significant improvement of clinical outcomes in PD patients.

Correlation between HSP-72 expression and IL-8 secretion in human mesothelial cells.

BACKGROUND: Cytotoxicity of peritoneal dialysis fluid (PDF) and peritoneal inflammation are currently regarded as the two major culprits for chronic mesothelial injury and peritoneal membrane failure. In this study, we correlated induction of HSP-72, as a marker of the cellular stress response, to secretion of IL-8, as a marker for pro-inflammatory cytokines, in mesothelial cells upon sublethal PDF exposure. METHODS: Primary omental cell cultures of human mesothelial cells were subjected to sublethal PDF exposure times (CAPD2, Fresenius, Germany). At the end of a 24 hour recovery period, induction of HSP-72 in the cell homogenate and IL-8 secretion in the supernatant was assessed by immunodensitometry and ELISA, respectively. RESULTS: PDF exposure times from 15 min to 60 min resulted in progressively increased HSP-72 expression levels (267 vs 320 vs 419% of controls, p<0.05 vs controls) as well as increased IL-8 secretion (323 vs 528 vs 549% of controls, p<0.05 vs controls) with full cell viability (MTT unchanged to control). HSP-72 expression was statistically significantly correlated with IL-8 secretion. CONCLUSIONS: The significant correlation between HSP-72 expression and IL-8 secretion suggests that the regulation of pro-inflammatory pathways in mesothelial cells exposed to PDF may represent an integral part of their stress response. Future studies to investigate the cellular regulatory mechanism involved are warranted.

Comparison of icodextrin- and glucose-based peritoneal dialysis fluids in their acute and chronic effects on human peritoneal mesothelial cells.

BACKGROUND: Icodextrin-based peritoneal dialysis fluids (PDFs) display several features that may potentially improve their biocompatibility compared to conventional glucose-containing solutions. So far, however, the studies assessing the biocompatibility profile of icodextrin toward human peritoneal mesothelial cells (HPMC) has produced mixed results. The present study was performed to examine the acute and chronic impact of icodextrin on HPMC in vitro in comparison with standard glucose-based PDF. METHODS: Omentum-derived HPMC were either acutely pre-exposed to or incubated chronically (for up to 10 days) in the presence of icodextrin-PDF. Parallel cultures were treated with conventional PDFs containing either 1.5% or 4.25% glucose. All fluids were tested at neutral pH. HPMC were assessed for viability, proliferation, IL-6 secretion and generation of reactive oxygen species (ROS). RESULTS: Incubation in the presence of icodextrin-PDF significantly reduced HPMC proliferation in a manner similar to that of 1.5% glucose-PDF. In addition, exposure to icodextrin-PDF impaired viability and IL-6 release from HPMC. This effect occurred both after the short pre-treatment with neat icodextrin-PDF for 1-4 hours and after prolonged incubation (up to 10 days) in media supplemented with icodextrin-PDF (1:1). The dysfunction of icodextrin-treated HPMC was of the magnitude that was between the effects exerted by 1.5%- and 4.25%-glucose PDF. Furthermore, exposure of HPMC to icodextrin-PDF induced a dose-dependent increase in ROS generation which was comparable to that produced by 1.5%-glucose PDF. CONCLUSION: Exposure to icodextrin-PDF may impair viability and function of HPMC. The detrimental effects of icodextrin-PDF are at least as serious as those produced by conventional heat-sterilized low glucose-based PDF.

Peritoneal dialysate fluid composition determines heat shock protein expression patterns in human mesothelial cells.

BACKGROUND: Low biocompatibility of peritoneal dialysis fluids (PDF) contributes to mesothelial injury. We investigated whether the heat shock proteins (HSP)-27, HSP-72, and HSP-90 are differentially induced upon exposure of mesothelial cells to PDF and whether this was affected by selective modulation of the physicochemical properties of PDF. METHODS: Human mesothelial cells (Met5A and primary human mesothelial cells) were exposed to acidic lactate and glucose-monomer based PDF (CAPD2 and CAPD3), to control culture media, or to a neutral lactate and glucose-monomer-based PDF with reduced levels of glucose degradation products (BALANCE). Expression of HSP-27, HSP-72, and HSP-90 and cellular distribution of HSP-72 were assessed by Western blotting and immunocytochemistry. RESULTS: Mesothelial cells exhibited strong constitutive expression of HSP-27 and to a lesser extent HSP-72 and HSP-90. Exposure of the cells to CAPD2 and CAPD3 resulted in strong up-regulation of HSP-72. HSP-27 levels were slightly increased, but HSP-90 levels were unchanged upon exposure to CAPD2 or CAPD3. In contrast, exposure of the cells to BALANCE did not affect HSP-27 or HSP-72 expression. The acidic pH and glucose degradation products were found to be principal in mediating increased HSP-72 expression upon exposure to PDF. CONCLUSIONS: Analysis of HSP expression represents a novel tool to assess biocompatibility of PDF. Among the HSP investigated, HSP-72 is the most predictive and accurate parameter to assess mesothelial cell injury in the early phase of exposure to PDF.

Glucose degradation products and peritoneal membrane function.

BACKGROUND: The bioincompatibility of peritoneal dialysis fluids (PDF) in current use has been partially attributed to the presence of glucose degradation products (GDPs), which are generated during heat sterilization of PDF. Several of the GDPs have been identified and we have recently demonstrated that these GDPs per se may impair the viability and function of human peritoneal mesothelial cells (HPMC) in vitro. It is also possible that GDP-related toxicity is further exacerbated by the milieu of PDF. We review the current literature on GDP and present the results of experiments comparing the impact of heat- and filter-sterilized PDF on the viability and function of HPMC. METHODS: Peritoneal dialysis fluids with low (1.5%) and high (4.25%) glucose concentrations were laboratory prepared according to the standard formula and sterilized either by heat (H-PDF; 121 degrees C, 0.2 MPa, 20 minutes) or filtration (F-PDF; 0.2 microns). The buildup of GDP was confirmed by UV absorbance at 284 nm. Confluent HPMC monolayers were exposed to these solutions mixed 1:1 with standard M199 culture medium. After 24 hours, cell viability was assessed with the MTT assay, and interleukin-1beta-stimulated monocyte chemotactic protein-1 (MCP-1) release with specific immunoassay. RESULTS: Exposure of HPMC to H-PDF resulted in a significant decrease in cell viability, with solutions containing 4.25% glucose being more toxic than 1.5% glucose-based PDF (27.4% +/- 3.4% and 53.4% +/- 11.0% of control values, respectively). In contrast, viability of HPMC exposed to F-PDF was not different from that of control cells. Moreover, treatment with H-PDF impaired the release of MCP-1 from HPMC to a significantly greater degree compared to F-PDF (17.4% and 24.9% difference for low and high glucose PDF, respectively). CONCLUSIONS: Exposure of HPMC to H-PDF significantly impairs cell viability and the capacity for generating MCP-1 compared to F-PDF. This effect is likely to be mediated by GDPs present in H-PDF but not in F-PDF.

Synthesis of C-X-C and C-C chemokines by human peritoneal fibroblasts: induction by macrophage-derived cytokines.

Leukocyte accumulation during peritonitis is believed to be controlled by chemotactic factors released by resident peritoneal macrophages or mesothelial cells. Recent data indicate, however, that in many tissues fibroblasts play a key role in mediating leukocyte recruitment. We have therefore examined human peritoneal fibroblasts (HPFBs) for the expression and regulation of C-X-C and C-C chemokines. Quiescent HPFBs secreted monocyte chemoattractant protein (MCP)-1 and interleukin (IL)-8 constitutively. This release could be dose-dependently augmented with the pro-inflammatory cytokines IL-1beta and tumor necrosis factor-alpha. Stimulated IL-8 production reached a plateau within 48 hours while MCP-1 continued to accumulate throughout 96 hours. Induction of IL-8 and MCP-1 synthesis by HPFBs was also triggered by peritoneal macrophage-conditioned medium. This effect was partly related to the presence of IL-1beta as demonstrated by IL-1 receptor antagonist inhibition. Pretreatment of HPFBs with actinomycin D or puromycin dose-dependently reduced cytokine-stimulated IL-8 and MCP-1 secretion, which suggested de novo chemokine synthesis. Indeed, exposure of HPFBs to IL-1beta and tumor necrosis factor-alpha produced a significant up-regulation of IL-8 and MCP-1 mRNA. This effect was associated with the rapid induction of nuclear factor-kappaB binding activity mediated through p65 and p50 subunits, and with a transient increase in the mRNA expression for RelB and inhibitory protein kappaB-alpha proteins. These data indicate that peritoneal fibroblasts are capable of generating large quantities of chemokines under a tight control of nuclear factor-kappaB/Rel transcription factors. Thus, peritoneal fibroblast-derived chemokines may contribute to the intraperitoneal recruitment of leukocytes during peritonitis.

Glucose degradation products and the peritoneal mesothelium.

Conventional heat-sterilized, glucose-based peritoneal dialysis (PD) fluids contain significant amounts of glucose degradation products (GDPs) such as aldehydes and dicarbonyl compounds (glyoxal, methylglyoxal). These GDPs have been shown to impair cell functions in various in vitro experimental models. In peritoneal mesothelial cells, GDPs dose-dependently inhibit cell proliferation and mediator synthesis. In addition, some GDPs potently promote generation of advanced glycation end-products (AGEs). Immunohistochemistry finds AGEs in the peritoneal membrane of chronic continuous ambulatory peritoneal dialysis (CAPD) patients, suggesting that peritoneal AGE accumulation may be involved in chronic peritoneal fibrosis. The formation of GDPs might be prevented by filter-sterilization of PD fluids. Another option is to separate the glucose and the buffer system in dual-chambered or multi-chambered containers. In these systems, the glucose is kept in a separate compartment at high concentration and very low pH-both conditions being known to minimize the degree of glucose decomposition during autoclaving. Initial experimental evidence suggests that these novel, multi-chambered fluids significantly improve in vitro biocompatibility; however, the clinical relevance of these results remains to be established in clinical trials.

Biocompatibility and buffers: effect of bicarbonate-buffered peritoneal dialysis fluids on peritoneal cell function.

BACKGROUND: Conventional peritoneal dialysis fluids (PDF) have been shown to compromise the function of both leukocytes and human peritoneal mesothelial cells (HPMC). Various in vitro studies have identified the low initial pH in combination with high lactate content, as well as the hyperosmolality and high glucose concentration present in currently used solutions as the primary determinants of their bioincompatibility. Bicarbonate buffered PDF (at neutral pH) display improved in vitro biocompatibility as compared to conventional, lactate buffered PDF. However, little information is currently available regarding the potential impact of PDF on the function of human peritoneal fibroblasts (HPFB), the major cell population present in peritoneal interstitium. METHODS: The current study compares the effect of bicarbonate and lactate buffered PDF in a model system of resting peritoneal mesothelial cells and fibroblasts cultured from human omentum. Interleukin-1 beta-stimulated IL-6 release from HPMC and HPFB was used as the cell functional parameter. RESULTS: While short (30 min) pre-exposure to lactate buffered PDF significantly reduced the IL-1 beta-stimulated IL-6 release from HPMC during a subsequent recovery period (24 hr), a significant decrease in HPMC IL-6 secretion with bicarbonate buffered PDF was only observed after prolonged (> or = 60 min) exposure. In contrast, no significant IL-6 inhibition was detected with HPFB pre-exposed to PDF for up to 90 minutes. A significant suppression of HPFB IL-6 secretion was only observed in coincubation experiments (24 hr) with dilutions of both types of PDF. CONCLUSIONS: These results indicate that (i) bicarbonate buffered PDF are less inhibitory to peritoneal cell function as compared to conventional, lactate buffered PDF; and (ii) HPFB may be more resistant than HPMC to bioincompatible PDF.