PERITONEAL CATHETERS AND EXIT-SITE PRACTICES TOWARD OPTIMUM PERITONEAL ACCESS: 1998 UPDATE
(Official Report from the International Society for Peritoneal Dialysis)
Reviews and Original Articles
PERITONEAL CATHETERS AND EXIT-SITE PRACTICES TOWARD
OPTIMUM PERITONEAL ACCESS: 1998 UPDATE
(Official Report from the International Society for Peritoneal Dialysis)
Manchester Royal Infirmary,1, Manchester, U.K.;
Stanford University Medical Centre,2,
Stanford, HemoCleanse,3, West Lafayette, Indiana, U.S.A.;
Veterans General Hospital,4, Taipei, Taiwan;
Karolinska Institute,5, Huddinge, Sweden;
Baxter Healthcare,6, McGaw Park, Illinois, U.S.A.; Holbæk County Hospital,7 Holbæk, Denmark;
Moncrief Dialysis Center,8 Austin, Texas, University of Missouri,9 Columbia, Missouri;
University of Pittsburgh Medical Centre,10 Pittsburgh, Pennsylvania, U.S.A.;
Hôpital Lapeyronie,11 Montpellier, France;
University Hospital,12 Umeå, Sweden;
Toronto Western Hospital,13 Toronto, Ontario, Canada
The key to successful chronic peritoneal dialysis
(PD) is permanent and safe access to the peritoneal cavity. Despite improvements in catheter survival over the last few years, catheter-related complications still occur, causing significant morbidity and often forcing the removal of the catheter. Catheter-related problems are a cause of permanent transfer to hemodialysis (HD) in up to 20% of all patients who need such therapy changes; many more require temporary periods on HD. Since the incidence of peritonitis is declining following the introduction of new connectology, catheter-related complications during PD have become a major concern.
A panel of experts, who are co-authors of this report, recently met to discuss catheter-related problems with a view to establishing guidelines toward optimal peritoneal access. Some of the members of this group also participated in previous reports (Oreopoulos in 1987; Gokal et al. in 1993). Wherever possible, the guidelines are evidence-based (e.g., randomized controlled trials); where scientific evidence is not available, recommendations are based on a consensus opinion. It is our hope that these guidelines for peritoneal catheter management will help to improve catheter care and, therefore, patient outcomes. An Appendix gives guidelines for pediatric catheter practices where they differ from the adult practices.
The ideal catheter provides reliable, rapid dialysate flow rates without leaks or infections. Despite many newer catheter designs, the Tenckhoff catheter is still most often used (USRDS 1992; Lupo et al., 1994). Variations of the peritoneal catheter include the number of cuffs (one versus two), the design of the subcutaneous pathway (permanently bent vs straight), and the intra-abdominal portion (straight vs coiled).
Types of Catheters (Figures 1 and 2)
The chronic peritoneal catheter comprises an intra- and an extraperitoneal portion; the latter consists of a subcutaneous part that has a means to anchor the catheter (e.g., cuffs), and the external portion beyond the exit site (the latter is the same for all catheters). The standard, two-cuff, straight Tenckhoff catheter is still the most widely used access device, because it satisfies the needs of most patients and there is no conclusive evidence that any other catheter is superior (USRDS 1992; Piraino, 1995; Lupo et al., 1994). There are, however, many catheter variations designed to minimize complications of pain, inadequate flow, and infections (Figures 1 and 2). Catheters that are commonly used to gain peritoneal access are shown in Figure 1. These are the standard one- or two-cuff, straight or coiled Tenckhoff catheters, the Swan neck catheters, and the Toronto–Western Hospital (TWH) catheter. Figure 2 shows the currently available chronic catheters, illustrating the intraperitoneal (IP) and extraperitoneal (EP) designs. It is possible to combine EP and IP designs as shown.
Intraperitoneal Segment — for Improving Outflow:The catheter should always allow easy inflow and outflow of fluid; the latter can be more variable and difficult, especially during the last part of drainage.
Straight: The straight catheter, which can be utilized in combination with almost all extraperitoneal designs (Figure 2), is the most common design and the one that was originally used when the catheter was introduced in the 1960s by Tenckhoff. It comprises side holes to enhance flow in and out of the peritoneal cavity.
Coiled: The coiled catheter design, which can be utilized in combination with most extraperitoneal designs (Figure 2), provides an increased bulk of tubing to separate the parietal and visceral layers of the peritoneum. Flow in and out of the tip of the catheter is more protected and there are more side holes for outflow. It is believed that this design allows for better flow, less inflow pain, less propensity for catheter migration and omental wrapping, and is less traumatic to viscera than the tip of a straight catheter; however, conclusive evidence for this is lacking.
Silicone Discs: Silicone discs perpendicular to the catheter (as in the TWH catheter, Figures 1 and 2) hold the omentum and bowel away from the exit holes. These are also designed to maintain their position in the pelvis and thus minimize catheter tip migration. Disadvantages include more difficult surgical implantation and removal than standard Tenckhoff catheters.
T-Fluted: This design is shaped like a “T.” The intraperitoneal portion lies against the parietal peritoneum. Instead of side holes, the intraperitoneal portion has eight, 1 mm wide longitudinal “flutes” or grooves. This design allows better flow and prevents migration (Ash and Janle, 1993).
Subcutaneous Tract: Straight: This original design has been used with single- or double-cuff catheters or the beaded TWH catheter. The subcutaneous segment may be implanted in an arcuate tunnel, to enable the catheter exit to be caudally or laterally directed. Implantation of the straight catheter in an arcuate tunnel may increase catheter tip migration or external cuff extrusion as the catheter tends to “straighten” because of its resilience or “shape memory”; however, good results with straight catheters can be achieved (Favazza et al., 1995).
Permanent Bend: This design has a preformed bend, eliminating the resilience force or “shape memory” of straight catheters. It must be implanted in a tunnel that exactly reflects this shape. There are several varieties available:
1. The Swan neck catheter. Investigators at the University of Missouri (Twardowski et al, 1992) have advocated catheters with an inverted U-shaped arc (170 – 180 degrees) between the deep and superficial cuffs. The U-shaped, (arcuate) bend allows the catheter to exit the skin pointing downward and yet enter the peritoneum pointing toward the pelvis, in an unstressed condition as Tenckhoff originally suggested. The bead-and-disc cuff is incorporated into the design. The Swan neck Tenckhoff differs from the double-cuff Tenckhoff only by the 170 – 180 degree bend between the cuffs.
2. The Moncrief–Popovich catheter (Moncrief et al., 1996). This catheter is very similar to the standard Swan neck Tenckhoff catheter except that the external skin cuff is elongated to 2.5 cm and is tapered at the ends of the cuff.
3. The Swan neck Missouri (see below).
4. Pail-handle (Cruz) catheter (Cruz, 1992). This catheter has two right-angle bends: one to direct the intraperitoneal portion parallel to the parietal peritoneum, and one to direct the subcutaneous portion downward toward the skin exit site. The cuffs are small, permitting peritoneoscopic insertion. The catheter is available only in polyurethane. The clinical benefits of this catheter include more rapid inflow and outflow than standard silicone catheters because of the larger inner diameter.
5. Swan neck presternal catheter. This catheter is a modified Swan neck Missouri coil catheter. The major difference from the standard Swan neck Missouri catheter is in the length of the subcutaneous tunnel. The catheter is composed of two silicone rubber tubes that are to be connected end-to-end at the time of implantation (Twardowski et al., 1996). The implanted lower (abdominal) tube constitutes the intraperitoneal catheter segment and a part of the intramural segment. The upper, or chest, tube constitutes the remaining part of the intramural segment and the external catheter segment. This upper part has two cuffs, one on either side of the bent segment. This catheter is useful in extremely obese patients and those with ostomies (Twardowski et al. 1996).
Outcome in Relation to Exit Direction: A downward-directed exit site was associated with lower peritonitis rates in a report from pediatric centers in North America (Warady et al., 1996). In addition, the Network 9 study found that directing the subcutaneous portion of the catheter downward decreased the risk of peritonitis associated with exit-site and/or tunnel infection by 38%, while an upward-directed catheter had a 50% increased risk of catheter-related peritonitis, compared to horizontally-directed tunnels (Golper et al., 1996). The United States Renal Data System (USRDS) reported that the relative risk of peritonitis was essentially identical for straight and bent catheters; however, when the analysis was repeated with adjustment for possible center effect, the peritonitis rate was significantly lower with permanent bent catheters.
Swan neck catheters were designed to diminish cuff extrusions and catheter-tip migration associated with straight catheters implanted in arcuate tunnels. Although several studies have shown no advantage of bent catheters over straight catheters (Nebel et al., 1991; Bonzel et al., 1993), other studies have shown significantly better results (Hwang and Huang, 1994; Tielens et al., 1993). Randomized studies comparing a Swan neck catheter to the straight Tenckhoff catheter without a preformed bend showed a lower probability for a first exit infection with the Swan neck catheter, but the survival was not different (Eklund et al., 1994; Eklund et al., 1995). Cuff extrusions and catheter migration were seen only in the Tenckhoff catheters. In another randomized study, there was a significantly lower rate of exit-site infections with Swan neck catheters (Lye et al., 1996).
Anchorage: Dacron Cuffs: These are either one or two in number and are made of polyester fiber. The usual distance between the two cuffs is 5 cms. For obese patients this may be inappropriately short. A single cuff can function (flow and stability) as well as a double cuff when the single cuff is in the deep position.
The Bead-and-Flange at the Deep Cuff: This feature is utilized to strengthen the anchorage of the catheter into the abdominal wall. During implantation, the ball is located intraperitoneally and the flange is positioned flat above the peritoneum on the posterior rectus sheath. A purse-string suture between the bead and the flange decreases the risk of early leakage. The flange increases the mass of tissue ingrowth into the cuff/flange structure, which decreases the risk of leakage.
1. The TWH catheter has the flange and bead affixed perpendicular to the tubing.
2. The Swan neck Missouri catheter has the bead and flange affixed to the tubing at a 45 degree angle, so that, with placement, the intraperitoneal part naturally tends to angle downwards with less tendency to migrate into the upper abdomen. The slanted flange-and-bead, and bent tunnel segment require that the Swan neck Missouri catheters for right and left tunnels be mirror images of each other. A radiopaque stripe on the front of the catheter facilitates recognition of the right and left Missouri catheters and proper implantation.
Outcome in Relation to Number of Cuffs: The single-cuff catheter is associated with a shorter time to the first peritonitis episode (USRDS 1992; Warady et al., 1996; Honda et al., 1996). In addition, the single-cuff catheter (Lindblad et al., 1988; Favazza et al., 1995) has more exit-site complications and shorter survival times than the double-cuff catheter. Therefore, convincing data exist to indicate that double-cuff rather than single-cuff catheters should be used for chronic PD.
Silicone: The most frequently used material for permanent catheters over the last 30 years has been smooth silicone rubber (Silastic). The standard PD catheter is still made of silicone rubber and provided with up to two polyester cuffs. The silicone rubber is a polymer of methyl-silicate, the higher molecular weights being gums from which silicone rubber is made. The biocompatibility of silicone rubber is satisfactory because it is inert, atraumatic to the surrounding tissues, soft, flexible through a wide range of temperatures, and contains no clinically harmful, leachable plasticizers.
Polyurethane: To overcome the problem of catheter wall strength, polyurethane has been used. This has allowed thinner-walled catheters with larger lumens, thus allowing for quicker flows. It is also more pliable with increasing temperature. There does appear to be hydrolysis of the polyurethane surface and there have been reports of cracking of the material with constant use, especially when polyethylene glycol or alcohol is applied. The experiences of only one center are available (Cruz, 1992).
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