The Effects of Heparin Administration in an Animal Model of Chronic Peritoneal Dialysate Exposure

Diverse modes of heparin administration have been used in animal models of chronic peritoneal dialysate exposure to maintain catheter patency and prevent fibrinous adhesions. Heparin has biological actions independent of its well-known anticoagulant activity, including the ability to modulate extracellular matrix synthesis, cellular proliferation, angiogenesis, and inflammation. These actions may interfere with peritoneal membrane homeostasis. The present study evaluated the influence of the mode of heparin administration on technique survival and infection rate in a rat model of chronic dialysate exposure. Further, the incorporation of heparin in the peritoneal membrane was examined.

A 3.86% glucose dialysate was injected twice daily into Wistar rats with a heparin-coated catheter (group A1), or with a standard catheter with heparin injections during the entire exposure time (group A2) or only during 1 week (group A3). Sham manipulations were performed in a fourth group and a fifth group was left untreated. Technique survival was 80% in group A1, 60% in group A2, and 40% in group A3. The rate of infection was highest in group A1 and lowest in group A2. Intraperitoneally administered heparin accumulated in the peritoneal membrane, whereas dextran, with a molecular weight similar to that of heparin, was not incorporated in the peritoneum.

In conclusion, intraperitoneal heparin reduced the incidence of infection in an animal model of chronic dialysate exposure. The best technique survival was, however, obtained using a heparin-coated catheter. Heparin is incorporated in the peritoneal membrane, where it may exert diverse biological actions and thus bias study results. The use of a heparin-coated catheter in combination with antibiotics may be the optimal approach to obtaining peritoneal access in animal models of chronic dialysate exposure.

Non Anticoagulant Effects of Heparin: Implications for Animal Models of Peritoneal Dialysis

Heparin is a glycosaminoglycan with well-known anticoagulant activity. That property is used in animal models of peritoneal dialysis to maintain catheter patency and to prevent the development of peritoneal adhesions. However, heparin has a host of biologic actions beyond its role as an anticoagulant.

Heparin modulates the activity of various inflammatory cells, affects the synthesis of extracellular matrix, has antiproliferative effects on several cell types, and influences neoangiogenesis. By virtue of those actions, intraperitoneally administered heparin may interfere with peritoneal membrane homeostasis. The potential side effects of heparin use in animal models of peritoneal dialysis should be recognized to permit correct interpretation of experimental studies conducted in those models.

Peritoneal Membrane Preservation

Peritoneal dialysis (PD) is a successfully used method for renal replacement therapy. However, long-term PD may be associated with peritoneal fibrosis and ultrafiltration failure. The key factors linked to their appearance are repeated episodes of inflammation associated with peritonitis and long-term exposure to bioincompatible PD fluids. Different strategies have been proposed to preserve the peritoneal membrane. This article reviews the functional and structural alterations related to PD and strategies whereby we may prevent them to preserve the peritoneal membrane. The use of new, more biocompatible, PD solutions is promising, although further morphologic studies in patients using these solutions are needed. Blockade of the renin-angiotensin-aldosterone system appears to be efficacious and strongly should be considered. Other agents have been proven in experimental studies, but most of them have not yet been tested appropriately in human beings.

Encapsulating peritoneal sclerosis

Since the first peritoneal dialysis (PD) patients with encapsulating peritoneal sclerosis (EPS) were reported in 1980, EPS has been considered primarily a fatal complication. The incidence of EPS in PD patients has been reported to be from 0.7% to 7.3%, and the rate appears to be higher in patients receiving long-term treatment. Most data from Japan has shown an overall incidence of 2.5% with an evident negative effect of increasing duration of PD, which also augments mortality. Since EPS occurred after withdrawal from PD in more than half of the patients, strict monitoring is necessary when a long-term PD patient is withdrawn from PD. Maintaining patients on standard PD for more than 8 years using conventional solutions is associated with a substantial risk for development of EPS. Appropriate treatment according to the disease stage is most important in EPS treatment. Therefore, when examining a PD patient complaining of gastrointestinal symptoms, the possibility of EPS has to be kept in mind. Basic therapeutic tactics for EPS include appropriate use of steroids. If the state of bowel obstruction persists, laparotomy and enterolysis should be performed to obtain a complete cure. It is now recognized that EPS is not a fatal complication of PD.

The pathogenesis and therapeutic option of encapsulating peritoneal sclerosis

Since the first peritoneal dialysis (PD) patients with encapsulating peritoneal sclerosis (EPS) were reported in 1980, EPS has been considered primarily a fatal complication. The incidence of EPS in PD patients has been reported to be from 0.7% to 7.3%, and the rate appears to be higher in patients receiving long-term treatment. Most data from Japan has shown an overall incidence of 2.5% with an evident negative effect of increasing duration of PD, which also augments mortality. Since EPS occurred after withdrawal from PD in more than half of the patients, strict monitoring is necessary when a long-term PD patient is withdrawn from PD. Maintaining patients on standard PD for more than 8 years using conventional solutions is associated with a substantial risk for development of EPS. Appropriate treatment according to the disease stage is most important in EPS treatment. Therefore, when examining a PD patient complaining of gastrointestinal symptoms, the possibility of EPS has to be kept in mind. Basic therapeutic tactics for EPS include an appropriate use of steroids. If the state of bowel obstruction persists, laparotomy and enterolysis should be performed to obtain complete cure. It is now recognized that EPS is not a fatal complication of PD.

Intraperitoneal heparin reduces peritoneal permeability and increases ultrafiltration in peritoneal dialysis patients

BACKGROUND

Patients on long-term treatment with peritoneal dialysis (PD) suffer from increasing peritoneal permeability and loss of ultrafiltration as a result of persistent inflammation, which may be triggered by bioincompatible dialysis fluids. Heparins have anti-inflammatory and anticoagulant properties. We have examined the effect of intraperitoneal (IP) low-molecular weight heparin (tinzaparin) on peritoneal permeability and ultrafiltration in PD patients.

METHODS

By means of a double-blinded cross-over design, 21 PD patients were randomized to receive either placebo or tinzaparin intraperitoneally once a day for two treatment periods of 3 months, separated by a wash-out period. The effect of heparin on peritoneal permeability and ultrafiltration was assessed using the 4 h standard peritoneal equilibration test.

RESULTS

IP tinzaparin reduced significantly the dialysate-to-plasma ratios (D/P) of creatinine (P < 0.01), urea (P < 0.01) and albumin (P<0.05). In addition, the ratio of glucose concentration in dialysate at 4 h dwell to that of 0 h dwell (D(4)/D(0)) was increased (P<0.05) along with an increase in ultrafiltration volume (P<0.05).

CONCLUSIONS

IP tinzaparin reduces peritoneal permeability to small solutes and increases ultrafiltration in PD patients.