IMPROVED CONTINUOUS AMBULATORY PERITONEAL DIALYSIS SYSTEM

Abstract: The system has a catheter (1) permanently implanted in the peritoneal cavity. A fluid junction (12) allows connection to a dialysis fluid bag (13), and a fluid switch (11) controls flow to or from the bag (13). The epidermal and peritoneal interfaces of the catheter (1) are sealed by cuffs (8) formed of a material which allows viable tissue ingrowth to minimise tunnel infection. The material is a composite of activated charcoal impregnated with uncrosslinked phenolic resin.

Description: IMPROVED CONTINUOUS AMBULATORY PERITONEAL DIALYSIS SYSTEM DESCRIPTION The present invention relates to a dialysis system and particulalry, but not exclusively, to continuous peritoneal dialysis systems for ambulatory use. Continuous ambulatory peritoneal dialysis (CAPD) is a procedure which a patient with chronic renal failure can carry out, without hospitalisation, for example in their own home. CAPD comprises a closed loop system connecting the patient's peritoneal cavity via an indwelling catheter to a "giving set" attached to a dialyεate fluid bag. At the start of the treatment, pre-warmed peritoneal dialysis (PD) fluid is transferred from the bag into the peritoneum where it remains approximately for four hours before being drained back into the same bag. The PD- fluid bag is then changed using an aseptic technique which forms the basis of CAPD patient training. When the bag is connected, the new PD-fluid is transferred into the peritoneum by gravity flow. This is achieved by positioning the bag higher than the patient. Conversely in order to drain the peritoneum the bag is then placed below the level of the patient (peritoneum) . The whole procedure then is repeated 4-5 times daily, seven days a week. Despite an increased demand for peritoneal dialysis and related technological advances in recent years peritonitis remains the major limiting complication for CAPD therapy. The sources of infection leading to peritonitis arise principally through the lumen of the dialysis catheter and its junctions (transluminally) and along the outside of the dialysis catheter and implanted subcutaneous prosthesis (extraluminally) , either producing exit-side or tunnel infections. In addition, the present procedure is cumbersome OMPI S N T ' I and time-consuming; gravity PD-fluid transfer can lead to drainage (outflow) and inflow problems, junction sterilisation by fluid, such as Betadine, can be messy and time consuming; PD-fluid warming is frequently impractical, and outflow obstruction by omental wrap is also frequent. In addition, although the dacron felt cuffs and the silicone rubber presently used are satisfactory biocompatible materials, they cannot provide an adequate skin-air interface. An object of the present invention is to obviate or mitigate the abovesaid disadvantages. According to the present invention there is provided a peritoneal dialysis system comprising a catheter having a portion insertable into the peritoneum, the catheter being connectible to a dialysis fluid chamber by a single connection, means for controlling the flow of dialysis fluid from said chamber, and catheter securing means connected to said catheter for connecting said catheter to tissue. Preferably said catheter securing means comprises two cuff portions, one cuff portion for securing the catheter to the skin surface, the other cuff portion for securing the catheter to the fascia. Alternatively, said catheter securing means may extend continuously along the catheter from the skin surface to the fascia. Preferably also, the catheter has a curved portion, the curved portion having a plurality of apertures therein. Preferably also the means for controlling the flow is a non-fluid contacting pump, said pump being manually actua ' table by the patient. Preferably also, the means for controlling the flow of dialysis fluid includes a fluid switch located on-line in the catheter. Preferably also, the catheter securing means is OMPI made of uncrosslinked phenolic resin impregnated activated charcoal, the uncrosslinked resin within the charcoal composite being heated to a temperature just below the onset of carbonisation. Preferably also, the heat treatment is conducted in nitrogen, the temperature being cycled between ambient and 350 C at a constant rate. Preferably the constant rate is 0.1°C/min. An embodiment of the present invention will now be described by way of example with reference to the accompanying drawings in which:- Fig. 1 is a schematic diagram of a catheter in accordance with the invention located in the peritoneum; .Fig. 2 is a diagram of the attachment of the catheter to the permanent "giving set"; Fig. 3 shows a complete continuous ambulatory peritoneal dialysis system in accordance with the pres¬ ent invention. Referring now to Fig. 1, the catheter has three well defined sections; intraperitoneal 2, subcutaneous 3, and external 4. It has an overall diameter of 5mm and a bore size of 3rmτt, providing 34% greater free volume flow than conventional catheters. The intraperitoneal section 2 of the PD catheter 1 is about 160mm long and is perforated for about 100mm of its length with 48 spaced 0.6mm holes 5. The tip La of the catheter 1 is rounded off to avoid intraperiton¬ eal irritation. The full length of section 2 lies in a curved form in the peritoneal cavity in such a way as to minimise omentum or bowel wrapping. The subcutaneous section 3 is about 90mm long and starts just outside of the peritoneum and extending up to the epidermis 6 (5 - 10)mm below the skin surface 7. Outside of this section soft porous carbon cuffs 8 or alternatively a full length sleeve (not shown) are glued on with medical grade silastic E SHEEf adhesive. The carbon cuff is fabricated from activated charcoal tubing impregnated with phenolic resin (about 10-15% by volume) . One suitable resin is Type J20/ 317A produced by B.P. Chemicals. Any suitable conven¬ tional activated charcoal tubing may be used, but preferably the weave should be fairly open. The uncrosslinked polymer within the porous charcoal composite is heated to a temperature below that of onset of carbonisation. In this way the flexibility of the base material can be maintained where the excess volatile constituents are eliminated. The heat treatment is conducted in an inert nitrogen atmosphere and involves a controlled temperature cycle between ambient and 350 C at a rate of 0.1 C/ min. The upper limit of temperature is about 750 C about which the charcoal carbonises and becomes inflex¬ ible and the upper rate is about 0.5 C/min above which the quality of the composite is degraded by 'bubbling' for example. If the cycling rate is too fast the solvent cannot escape and retention of the solvent alters the * mechanical properties of the composite and makes it less flexible and brittle. The flexible carbon subcutaneous tissue interface due to its porous structure and inherent biocompatibility encourages viable tissue ingrowth and thus minimises tunnel infection. It also provides better physiological and mechanical sealing at the peritoneum- interface 9 and at the epidermis interface 10. The extra-abdominal section 4 of the catheter 1 has a continuous length of 2m. It is made up of two parts, one is the external section of the implanted catheter 4a_ and the other is a permanent "giving set" 4b. After 48 hours of implantation the two sections are permanently glued together with overlaying silicone rubber sleeving and adhesive as illustrated in Fig. 2. This two part arrangement facilitates implantation and also if it becomes necessary, repositioning of the catheter in the event of clinical complications. The use of a permanently extended catheter eliminates the need to change the giving set and provides a single junction closed loop CAPD systemand is also more cost effective. This design firstly minimises the number of contamination sites for possible infection and also contributes to a reduction in running cost for CAPD therapy. The extra-abdominal silicone rubber tubing also has an on-line fluid switch 11 and durable polycarbonate- stainless steel (PS) junction 12 (Fig. 3). This single .PS junction connects the catheter 1 to the flexible PD bag 13. A roller pump 14 receives the catheter 1, the catheter being located round the roller 15. The catheter is held in place by flanges 16. The pump 15 is driven by a small d.c. electric motor (not shown), the speed of which may be varied. The motor is powered by rechargeable batteries which may be recharged from the same 12v d.c. supply used to heat the dialysis fluid. This unit is small, portable and there is no contact between the dialysis fluid and the roller 15 which reduces the possibility of contamination. The whole assembly is sterilisable, for example by autoclaving and may be used as a permanent fixture by the patient. Polycarbonate may be replaced by any other suitable sterilisable material. The PS junction 12 is a double helix luer-type design which permits a single twist-on, twist-off connection to the PD fluid bag 13. This ensures a secure leakproof union during fluid transfer. The outside stainless steel body has a functional grip section and inside a polycarbonate luer-type cone which cannot be touch contaminated Thus the system consists of an extended long silicone rubber catheter which has a carbon subcutaneous SUBSTITUTE SHEET section and a single. PS junction connection between the peritoneum and the PD fluid bag. Advantages of the system are that: The roller pump system enables the patient to * perform dialysis at any location without the requirement of being restricted to finding suitable positions for the dialysis bag, this also means that the patient may be mobile during dialysing. When using the roller pump it is convenient to measure the electrical conductivity of the fluid inflow and outflow at the fluid junction which will provide a rapid indication of the effectiveness of the dialysis. It also uses as a permanent accessory an on-line fluid switch for safety and convenience and the resin impregnated carbon cuffs provide a good biocompatible interface between the skin and air; and the use of a soft carbon tissue interface coupled with a single junction design considerably lowers the probability of the rate of infection and of peritonitis episodes. $OREA OMPI

Claims: CLAIMS 1. A peritoneal dialysis system comprising a catheter having a portion insertable into the peritoneum, the catheter being connectible to a dialysis fluid* chamber by a single connection, means for controlling the flow of dialysis fluid from said chamber, and catheter securing means connected to said catheter for connecting said catheter to tissue. 2. The system of claim 1, in which said catheter securing means comprises two cuff portions, one cuff portion for securing the catheter to the skin surface, the other cuff portion for securing the catheter to the fascia. 3. The system of claim 1, in which said catheter securing means is a sleeve.extending continuously along the catheter a length equivalent to the distance between the skin surface and the fascia. 4. The system of any preceding claim, in which the catheter has a curved portion, the curved portion having a plurality of apertures therein. 5. The system of any preceding claim, in which the means for controlling the flow is a non-fluid contacting pump, said pump being manually actuatable by the patient. 6. The system of any preceding claim, in which • the means for controlling the flow of dialysis fluid includes a fluid switch located on-line in the catheter. 7. The system of any preceding claim, in which the catheter securing means is composed of activated charcoal impregnated with uncrosslinked phenolic resin. 8. The system of claim 7, in which the charcoal- res ' in composite has been heat-treated to a temperature below the onset of carbonisation. 9. The system of claim 8, in which the heat-treatment is conducted in a nitrogen atmosphere, the temperature being cycled between ambient and 350 C at a constant rate. OMPI £tfNAT 10. The system of claim 9, in which said rate is 0.1° C/min. 11. A peritoneal dialysis system substantially as herein described with reference to the drawings.

Inventors: JUHASZ LAZSLO, JUHASZ, LAZSLO
Applicants: UNIV STRATHCLYDE, UNIVERSITY OF STRATHCLYDE
Application year: 1982
Main classification: A61M1
IPC codes: A61M1, A61M25