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(Radiology. 2000;215:651-658.)
© RSNA, 2000

State of the Art

Hemodialysis Catheter Placement and Management1

Scott O. Trerotola, MD

1 From the Department of Radiology, University Hospital Room 0279, 550 N University Blvd, Indianapolis, IN 46202-5253. Received June 18, 1999; revision requested August 2; revision received August 30; accepted September 21. Supported in part by a grant from Medcomp, Harleysville, Pa, and Bard Access Systems, Salt Lake City, Utah. Address correspondence to the author (e-mail: streroto@iupui.edu).

Abstract

Hemodialysis catheters are an integral part of the delivery of hemodialysis. While catheters play an important role in the patient undergoing hemodialysis, catheters should be considered a bridge to more permanent forms of dialysis access in most patients. Recent advances in catheter technology, access techniques, and choice of access sites have improved outcomes associated with hemodialysis catheters. The placement and management of hemodialysis catheters by interventional radiologists have played an important role in these advances, and interventional radiologists are taking an increasingly active role in the research and development of catheters and catheter insertion techniques. The present status of hemodialysis catheters is reviewed.

Index terms: Catheters and catheterization, 907.1269, 946.1269 • Catheters and catheterization, central venous access, 907.1269, 946.1269 • Catheters and catheterization, complications, 907.29, 907.442, 946.29, 946.442 • Catheters and catheterization, technology • Dialysis • State of the Art

More than 200,000 patients undergo hemodialysis in the United States at present (1). Each of these patients needs some form of vascular access to allow sufficient blood flow for hemodialysis, which is administered three times weekly. Currently, the three forms of long-term access most commonly used are the native (Brescia-Cimino) fistula, synthetic graft, and tunneled catheter. Although the Dialysis Outcomes Quality Initiative (DOQI) Vascular Access Guidelines recommend that no more than 10% of permanent access be in the form of catheters (2), in many centers, the percentage is still far higher. Further, tunneled catheters serve an important ancillary role during the maturation of grafts (usually about 1 month) and fistulas (up to 3 months or more) and serve an important role in patients undergoing continuous ambulatory peritoneal dialysis while their catheter heals or during episodes of peritonitis. For these applications, the role of the tunneled catheter is best described as a bridge that allows hemodialysis until the more definitive form of dialysis begins (or resumes). The result is that more than 250,000 tunneled hemodialysis catheters are inserted annually in the United States (Madison T, written communication, 1999).

Interventional radiologists have adopted an increasingly prominent role in the placement and management of hemodialysis catheters, as well as in the research and development of new and better catheters. The following is not meant to be an exhaustive review of hemodialysis catheters; for this, the reader is referred to a recent review (3). Rather, this article will highlight relatively recent developments in this area, concentrating on current problems with these catheters and potential solutions.

PROBLEMS

While current tunneled catheters, particularly those with the latest designs, possess many of the characteristics of the ideal catheter, the long-term problems of infection and thrombosis have not been conquered to date. Infection occurs in up to 54% of catheters, and despite new approaches to the prevention and treatment of infection, up to two-thirds of infected catheters will need to be removed (4–17). Catheter infection may be life-threatening: Fourteen percent of deaths in the population undergoing dialysis in 1996 was due to infection; the majority of these deaths were related to access (1).

Although not all access-related deaths are related to catheters, catheter-related problems account for the majority. Multiple strategies for the reduction of infection have been tried; some are, at least, partially successful (discussed in Infection). Most of these strategies have paralleled those used in infusion catheters in patients with cancer; thus, it is not surprising that the latest approach in this area is the development of subcutaneous ports for hemodialysis (discussed later). Infection, particularly late infection, is inexorably tied to thrombosis because bacteria do not adhere well to the smooth surface of catheters but readily attach to fibrin sheaths (18–20). Thus, conquering infection may require conquering thrombosis, the other principal long-term problem hemodialysis catheters face.

Catheter thrombosis, either in the form of venous thrombosis or in the formation of a fibrin sheath, accounts for up to 40% of catheter failures (7,12,13,16,21); if only unanticipated catheter removals are considered, the percentage is even higher (16). Venous thrombosis may be disastrous, as it may preclude use of the ipsilateral extremity for more permanent forms of dialysis access. The treatment of fibrin sheaths not only interrupts tight dialysis schedules but also results in the use of often costly measures. Further, a small fibrin sheath may make even the best catheter deliver suboptimal flow rates, eliminating the benefit of the great strides recently made in the flow rates achievable with catheters.

Central venous stenosis is an insidious and potentially devastating complication of the use of dialysis catheters because, typically, it is silent until a graft or fistula is placed into the ipsilateral arm. The high flow rate from the graft or fistula then unmasks the stenosis, usually resulting in painful and disfiguring arm swelling. While percutaneous treatments such as angioplasty and stent placement may temporarily relieve the stenosis, the long-term durability of these techniques is fair at best, and there are, essentially, no viable surgical options.

For many years, inadequate delivery of blood flow for dialysis has been a consistent complaint from nephrologists. Inadequate blood flow can be divided into acute and chronic phases: Acutely diminished flow may be due to catheter malpositioning or other mechanical problems, while diminished flow occurring later may be due to thrombosis or formation of a fibrin sheath in addition to mechanical problems. Until recently, blood flow rates below 200 mL/min were generally considered inadequate, however, the DOQI guidelines raised the standard for blood flow rates by suggesting a minimum flow rate of 300 mL/min (2). This change reflects the increasing need on the part of nephrologists to deliver timely dialysis with a limited number of dialysis machines available.

Other problems catheters face include insertion-related complications such as hemothorax, pneumothorax, and air embolus.

SOLUTIONS: PRESENT RESEARCH

Blood Flow
One of the most promising developments in dialysis catheter technology has been the recent introduction of high-flow catheters capable of delivering flow rates much higher than the DOQI-recommended rate of 300 mL/min. Many different catheter designs are in use; the description of all of these is beyond the scope of this discussion. Until the past few years, most catheters were similar, varying slightly in construction and diameter but uniformly having step-tip or staggered-tip configuration. Most older catheters, when properly positioned, can deliver flow rates of 300 mL/min, but subtle malpositioning and the formation of fibrin sheaths could easily result in poor flow rates. In fact, in one recent series of step-tip conventional dialysis catheters (16), flow-related problems accounted for 53% of unanticipated catheter removals.

One approach to the improvement of the flow rate was the introduction of twin silicone catheters (Schon, AngioDynamics, Queensbury, NY and Tesio, Medcomp, Harleysville, Pa); each catheter was 10 F in diameter and was introduced through one or two venipunctures with separate subcutaneous tunnels. Early reports of the twin catheters (11,22) indicated an excellent catheter survival rate that was surprisingly higher than that of existing step-tip catheters. This finding prompted speculation that the catheters were somehow self-cleaning by virtue of their motion against each other in the superior vena cava and right atrium.

Subsequent reports (23,24) have not borne out these initial results, and while it appears that twin catheters can deliver slightly higher flow rates than can conventional catheters, the rate of fibrin sheath formation appears to be similar, and the rate of infection may actually be higher than that of conventional catheters. For example, we reported overall infection rates of 0.16 per 100 catheter days (infection requiring removal, 0.08 per 100 catheter days) in one series (16) and 0.11 requiring removal and 0.15 overall per 100 catheter days in another (17). Caridi et al (23) recently reported, using the same definitions, an overall infection rate for Tesio catheters of 0.46 per 100 catheter days. These findings make sense, since there are two tunnels instead of one. The catheters are more difficult to insert and have had difficulties with hub breakage, which, at one point, prompted a recall. Further, the catheters cannot be used immediately after insertion but must be cured with urokinase for 24 hours before use. Since access for dialysis is often required immediately, this delay may interfere with patient care. The cost of twin catheters ($285) is similar to that of other catheters, including the newer thin-walled catheters.

More recently, thin-walled large-bore polyurethane catheters have been introduced in an effort to provide higher flow rates (Fig 1). Two designs are currently available—a step-tip design (Opti-Flow; Bard Access Systems, Salt Lake City, Utah) and a split-tip design (Ash Split; Medcomp). The latter catheter theoretically offers the advantages of twin catheters while maintaining the ease of insertion of a single catheter.



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  		Figure 1. Photograph depicts high-flow dialysis catheters. Note the differences in tip configuration in the polyurethane catheters (Ash Split, Opti-Flow). The Tesio system requires two tunnels, while the others require a single tunnel.

 
We recently completed a prospective randomized trial in which we compared the Ash Split catheter (25) with a conventional silicone catheter, the 13.5-F Hickman catheter (Bard Access Systems); the Hickman catheter was our standard dialysis catheter and had previously been shown to consistently deliver flow rates of 300 mL/min (16). In that trial, we used the ultrasonic dilution technique (Transonic Systems, Ithaca, NY) that has become the standard method of determining the effective blood flow rate, or QbEff, in dialysis access circuits at various pump speed settings. The ultrasonic dilution technique allows investigators to measure the actual flow rate rather than the measured (prescribed) pump speed; the former is consistently lower than the latter. We found that both catheters could deliver an effective blood flow rate of 300 mL/min, which complies with DOQI guidelines, but that the split-tip catheter could deliver a much higher effective blood flow rate if needed (Table) (25).


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  		Effective Flow Rates at Various Pump Speeds
 
This finding rapidly led to requests from referring nephrologists for the higher-flow catheter; in turn, they began increasing the prescribed flow rates in patients with these catheters, allowing more efficient dialysis. We are currently comparing the Ash Split catheter with the step-tip Opti-Flow catheter in a randomized trial. This trial should allow us to determine whether there is any long-term advantage to the use of a split-tip catheter versus a step-tip catheter, since the catheters are similar in every other respect (14.5-F, double D configuration). On the basis of the findings from our short-term study (25), we believed that the added cost of the high-flow catheters ($260–$398 vs $110–$160 for older conventional catheters) was justified by their higher flow rates, and we now exclusively use high-flow polyurethane catheters for dialysis in our practice. Given the excellent blood flow rate provided by these catheters, it seems doubtful that the additional risk and difficulty of insertion associated with twin-catheter (eg, Tesio) designs are justified.

Central Venous Stenosis
Another important advance in the use of hemodialysis catheters was the recognition of the association between central venous stenosis and subclavian dialysis catheters. Thus, the key to the management of central venous stenosis is prevention, but it was not until two landmark studies (26,27) were published earlier this decade that the clear benefits of the use of internal jugular catheters rather than subclavian catheters were widely recognized. The authors of these studies demonstrated, using nontunneled catheters, an incidence of central venous thrombosis and/or stenosis of 40%–50% with the subclavian route versus an incidence of 0%–10% with the right internal jugular route. We have demonstrated a 4% incidence of central venous abnormality following the placement of tunneled right internal jugular catheters; none of the patients with abnormalities were symptomatic (17).

The DOQI guidelines strongly recommend avoidance of the subclavian vein unless no other option exists or unless the ipsilateral extremity can no longer be used for permanent dialysis access (2). Despite the statistics and the existence of national guidelines to the contrary, many practitioners, who may feel uncomfortable with the internal jugular route because they were trained by using the subclavian venous route, continue to use the subclavian vein for the placement of tunneled and nontunneled catheters. Fortunately, nearly all interventional radiologists who place dialysis catheters have at their disposal the tools to place internal jugular catheters with confidence—ultrasonography (US) and fluoroscopy. The use of US guidance for venous puncture and fluoroscopy for catheter placement and positioning dramatically reduces the rate of complications associated with catheter placement (16,17,23) and increases the rate of success. The DOQI document mandates fluoroscopic guidance and strongly suggests the use of US for catheter placement. The results of the transition to imaging-guided placement are a reduction in the rate of initial catheter malfunction from as high as 14% (12,15,28) to near zero (16,17,23) and a reduction in the rate of major complications from as high as 5.9% (5,6,12–15,22,29–32) to near zero (16,17,23).

Thrombosis
As noted previously, thrombosis occurs in two distinct forms in hemodialysis catheters; each form is treated quite differently. The formation of fibrin sheaths probably represents the natural tendency of the body to try to exclude a foreign body from the circulation. By using this somewhat simplistic but nonetheless accurate description, it is tantalizing to think of strategies for the prevention of fibrin sheaths that might somehow make the catheter immunologically invisible ("stealth" catheter). Indeed, I view this concept as the "Holy Grail" of dialysis catheter research and believe that if one could develop a "stealth" catheter, it might revolutionize the use of catheter-based hemodialysis. Unfortunately, to date, the achievement of this lofty goal is nowhere in sight.

Most strategies aimed at fibrin sheaths have been in the form of treatment after the sheath has occurred rather than prevention, although at least one group (33) has reported success with the prophylactic administration of urokinase in tunneled infusion catheters; this finding might apply to dialysis catheters as well. Hydrophilic coating of catheters is a new addition in the infusion catheter arena; this approach will undoubtedly be applied to dialysis catheters as well. But until prospective randomized trials demonstrate a benefit to this approach, it remains essentially hypothetical.

Surface treatments designed to prevent infection (discussed later) might also be expected to prevent thrombosis because of the thrombosis-infection interrelationship. However, in a prospective randomized trial (17), we demonstrated that treatment of a catheter with silver did not reduce the thrombosis rate. Bonding of catheter surfaces with thrombolytic agents, heparin, or other agents represents another possible approach to this problem. It has been theorized that twin or split-tip catheters (see Blood Flow) might somehow be self-cleaning by virtue of their continuous motion against each other; this theory has been proposed as an explanation of the better longevity reported with twin catheters (11,22), but this concept has not been validated in a prospective randomized fashion.

Findings from intriguing new work in animals has also suggest that fibrin sheaths are not simply composed of fibrin but that they may mature into neointimal hyperplasia (34,35). If confirmed in humans, these findings would, at least, raise the possibility that drugs currently being tested for the reduction of restenosis might also be valuable in the prevention of fibrin sheaths in dialysis catheters; this possibility will require further study.

Multiple approaches to the treatment of existing fibrin sheaths include fibrin sheath stripping (4,28,36,37), thrombolytic infusion (7,16,38,39), and catheter exchange (40). It is beyond the scope of this review to describe these in detail. Briefly, fibrin sheath stripping is performed transfemorally under fluoroscopic guidance by using a snare to pull the sheath off the catheter to allow it to embolize to the lungs. This obviously requires femoral venous puncture with its (albeit small) attendant risks (2% deep venous thrombosis in Crain et al's series [28]), as well as recovery after the procedure. Infusion, on the other hand, can be performed in the treatment area of the dialysis unit in a manner similar to the infusion of any other medication. Catheter exchange requires fluoroscopic guidance, but it can generally be performed through the same tunnel over one or more guide wires (40); thus, it does not require an additional venous puncture or any recovery period.

The DOQI guidelines, which reflect the state of the art in 1997, do not recommend one of these approaches more than the others. However, findings from a recently completed randomized study (39) have shown that stripping and urokinase infusion are equivalent in immediate patency (approximately 90%) and midterm patency (at 45 days; stripping, 33% and urokinase, 37%). Since stripping is costlier than infusion, the findings of this study would appear to indicate that thrombolytic infusion is the treatment of choice for fibrin sheaths on hemodialysis catheters. This preference is reflected in the flow diagram (Fig 2), which represents an algorithm that we have used for a decade with good results. The only change during that time was a reduction in the overall infusion time to 4 hours (previously it was 6 hours at a lower dose; Gray et al [39] used 4 hours) and an increase in the rate of infusion to 30,000 U per lumen per hour, which can be performed safely with little or no bleeding complications. This approach has a reported success rate of 55%–95% (7,16,39); the range is probably due, in large part, to differences in definitions. Using careful catheter injection (so as not to disrupt the sheath and render the infusion less effective) and the previously mentioned infusion rate, Gray et al (39) reported the best results.



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  		Figure 2. Flow diagram depicts the treatment of fibrin sheaths in tunneled hemodialysis catheters. CXR = chest radiograph, IR = interventional radiology.

 
Another consideration is that while urokinase infusion may disrupt the dialysis schedule, even if only briefly, the use of urokinase during dialysis, as described by Twardowski (38), does not; it also yields excellent results (up to 90% after repeated administration). One current consideration is the lack of availability of urokinase, which has prompted an evaluation of the use of other thrombolytic agents such as recombinant tissue plasminogen activator (r-tPA) (Activase; Genentech, South San Francisco, Calif). While the use of low-dose r-tPA has been described in the treatment of intraluminal thrombus in dialysis catheters with good results (41), to my knowledge, no study of the use of r-tPA infusion for the treatment of fibrin sheaths in tunneled hemodialysis catheters has been published.

When this low-dose dwell fails, our institution currently uses a 5-mg infusion of r-tPA over a 2.5-hour period as an alternative to urokinase. It is my belief that if infusion fails, catheter exchange is more cost-effective than stripping, but this has yet to be studied in a randomized fashion. A caveat is that if the use of dialysis ports gains widespread acceptance (discussed later), ports that develop fibrin sheaths and fail thrombolytic infusion treatment might benefit from stripping, since exchange may be more difficult. Again, this awaits further study.

Venous thrombosis associated with hemodialysis catheters is, fortunately, rare (<5%) when the internal jugular approach is used (17,42). The approach to iatrogenic thrombosis in this situation depends largely on the patient's symptoms. While it is recognized that catheter-directed thrombolysis can be used to successfully treat thrombosed veins in this setting, this approach is costly ($3,400 per access site salvaged in 1987 [43], probably substantially higher now), and thrombosis has a high recurrence rate. Thus, catheter-directed lysis in this setting should be reserved for patients who are symptomatic and who fail to respond to heparin therapy alone.

Asymptomatic thrombosis is clinically relevant only if it compromises the outflow of an anticipated permanent form of access in the ipsilateral limb or if few veins remain for catheter placement. This issue must be taken into consideration when the decision to remove an infected catheter or to attempt salvage with exchange with a course of antibiotics is made (discussed later). In general, physicians at Indiana University make every attempt to leave a catheter in place in a thrombosed vessel, provided that the above conditions do not exist. The reason for this practice is that it is possible, with repeated catheter exchanges, to maintain this access indefinitely, whereas if the catheter were removed and placed into another vessel, the access site that was thrombosed may be permanently lost, and a new vessel is placed at risk. Again, this is particularly important in patients with limited access.

Although a low-dose anticoagulation regimen has been shown to reduce catheter-related venous thrombosis in the patients with cancer (44), to my knowledge, there are currently no data that support the use of anticoagulation either at minidose or at therapeutic levels in the prevention of catheter-related venous thrombosis in patients undergoing dialysis. A limited study performed at Indiana University, Indianapolis (45), with Bern et al's (44) low-dose regimen did not show any benefit.

Infection
As noted previously, infection is probably the most substantial impediment to more widespread long-term use of catheters for dialysis. Prevention of infection with a variety of strategies has not been proved to be effective to date. The prophylactic use of antibiotics at the time of catheter placement cannot be supported by the findings in literature, and, in fact, several randomized trials of patients with cancer have shown no benefit to this practice (46,47). The treatment of catheter surfaces with minocycline and the use of rifampin-impregnated (48) or silver sulfadiazine–coated (49,50) nontunneled catheters are beginning to emerge, with substantial reductions in infection rates in humans and animals.

However, just because these treatments are effective in animal models and short-term catheters does not mean that they are necessarily effective in tunneled catheters. This is borne out by what is, to my knowledge, the only randomized study of surface treatment to prevent infection in tunneled catheters to date (17). In this study of 91 catheters, not only did the silver surface treatment fail to reduce the infection rate (in fact, there was a trend, though not a significant one, for the treatment to increase the infection rate), but also, two patients in the treatment arm developed cutaneous reactions that left permanent scars. These findings underscore the need to study new surface treatments carefully in the specific application for which they are proposed rather than extrapolating the findings from other applications.

Another example of this need for further study is the silver-impregnated collagen cuff (VitaPhore; Integra Life Sciences, Plainsboro, NJ), which has been shown to prevent infection in nontunneled catheters (51–53) and which is widely distributed on tunneled catheters. However, to my knowledge, no study has ever demonstrated a benefit from the use of this device in tunneled dialysis catheters, and a randomized study in tunneled infusion catheters showed no benefit (54). Further, our group has shown that this particular device, when placed too close to the Dacron cuff on the catheter, may impede catheter fixation by killing fibroblasts (55), which may predispose the catheters to dislodgment.

There has been some progress in the treatment of infected dialysis catheters. Until recently, it was believed that any catheter that caused bacteremia should be immediately removed and not replaced until the results of blood cultures normalize. However, several new strategies have begun to emerge. In 1997, Marr et al (8) published findings from a series of 38 patients in whom bacteremia was medically treated while the catheter remained in place. Unfortunately, only 32% of the catheters were successfully salvaged by using this approach. Further, another group from the same institution reported a clustering of epidural abscesses that occurred in patients undergoing dialysis during the study period; this finding suggested that the medical approach alone may not only be ineffective but risky as well (9).

A logical extension of this approach is an exchange of the catheter during or after a course of treatment with antibiotics, which, hopefully, sterilizes the access site. Shaffer (56) reported good initial results with this approach in 10 patients; three patients required a second exchange to eradicate the infection. Robinson et al (57) (from the same institution as Marr et al [8]) reported findings from a series of 23 patients with bacteremia that was treated with catheter exchange and 3 weeks of treatment with antibiotics. Catheter sites with tunnel infections were excluded. This approach yielded eradication of the infection in 82% of access sites at 90-day follow-up.

Building on this technique, Beathard (10) recently published findings from a series in which patients with infected catheters were stratified into three groups as follows: those with bacteremia and minimal symptoms, those with tunnel or exit-site involvement and bacteremia, and those with severe clinical symptoms. In the first group (n = 49), the catheters were exchanged over a wire, and antibiotic therapy was instituted for 3 weeks with a method similar to Robinson et al's (57). The success rate was 88% at 45 days. The second group (n = 28), patients with tunnel or exit site involvement, was treated with catheter exchange, creation of a new tunnel, and antibiotics, with a 75% success rate. Notably, in the third group (n = 37), in whom the catheter was removed, antibiotic therapy was instituted until bacteremia cleared, and a new catheter was placed, the success rate was only 87% at 45 days. To summarize the findings from these recent series, catheter sepsis remains an indication for immediate catheter removal, whereas mildly symptomatic bacteremia may be treated with catheter exchange and antibiotics.

The nephrologists at my institution, however, have remained somewhat skeptical of the practice of guide-wire exchange for infection, but we do apply it in patients with limited remaining access sites in whom the parent vein has become thrombosed around the catheter (as described previously). In these patients, catheter removal would mean abandoning the access site, and, thus, catheter exchange is used with a course of treatment with antibiotics in an effort to salvage the site. We have several patients with translumbar catheters and no other available access site in whom this approach has yielded preservation of the access site for 5 years or more. However, if a patient has other available access sites or if the parent vein has not been occluded around the catheter, we remove the infected catheter, treat the bacteremia, and place a new catheter once the blood culture results are negative.

The recent introduction of dialysis ports represents yet another approach to controlling the problem of infection in patients with long-term catheters. Two devices are in clinical trials in the United States and elsewhere. Both borrow, albeit at increased cost, the concept of subcutaneous ports from the treatment of patients with cancer in whom ports have infection rates that are lower than those of tunneled catheters with external hubs (58). The devices consist of one or two subcutaneous ports connected to one or two silicone catheters that are placed via the internal jugular vein and accessed percutaneously.

Clinical experience with these devices is limited to small series. One device, Dialock (Biolink, Middleboro, Mass), consists of a titanium port with two individual needle passages (Fig 3) that are connected to two 11-F catheters with spiral side holes at their tips. The device is percutaneously accessed by using a proprietary needle-sheath combination and has a valve that holds the sheaths in place during dialysis. Published reports of two small clinical series (10 patients each) describe good results with this device, with mean flow rates of just over 300 mL/min. The early reported infection rates, however, do not appear to show a reduction: Levin et al (59) reported 0.23 bacteremic episode per 100 catheter days, and Canaud et al (60), 0.17 episode per 100 catheter days.



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  		Figure 3. Photograph depicts the Dialock device, which is implanted subcutaneously and accessed with specially designed needle sheaths for dialysis. The two catheters enter the venous system via the jugular vein, similar to standard tunneled dialysis catheters.

 
Recent improvements in catheter design may allow improved flow rates, but no results from the use of the newer catheters have been published yet. The other device, LifeSite (Vasca, Tewksbury, Mass), consists of two individual titanium ports attached to 12-F silicone catheters with circumferential side holes at the tip (Fig 4). The ports are accessed with a standard 14-gauge dialysis needle; when turned, the ports lock the needle in place. While, to my knowledge, no results from use of this device have been published yet, preliminary data have indicated a prescribed flow rate of approximately 380 mL/min and have indicated rates of infection that require catheter removal of 0.13 episode per 100 catheter days; overall infection was not reported (61). Neither of these devices has received U.S. Food and Drug Administration approval yet.



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  		Figure 4. Photograph depicts the LifeSite device. Two such devices are implanted subcutaneously; their catheters pass into the bloodstream via the jugular vein. The port is accessed with standard hemodialysis needles.

 
At present, it is not clear what role these devices will play. They are unlikely to be cost-effective as bridges to permanent access; the cost of the LifeSite device is expected to be $1,750 each ($3,500 per set), compared with approximately $250 for a high-flow tunneled catheter. Patient acceptance has been good, but if the principal goal is to reduce infection, it does not appear, on the basis of these early reports, that these devices will achieve that goal. In fact, the reported infection rates are, if anything, higher than those achieved in recent series in which interventional radiologists placed tunneled catheters (7,16,17). Hopefully, further trials will elucidate the role of these devices in the dialysis access armamentarium.

IDEAL DIALYSIS CATHETER

It is highly doubtful that anyone familiar with hemodialysis catheters would assert that the ideal catheter has been developed. This is underscored by the DOQI recommendations that the use of dialysis catheters should be avoided for long-term access. As described previously, challenges associated with hemodialysis catheters include the delivery of adequate flow, prevention of infection, prevention of venous stenosis and thrombosis, and prevention of the ubiquitous fibrin sheaths that interfere with flow. Only recently have any of these challenges been addressed to anyone's satisfaction. However, were it possible to design the ideal catheter, it might include the features listed in Figure 5.



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  		Figure 5. Characteristics of the ideal dialysis catheter.

 
While the ideal catheter does not yet exist, from the patient's standpoint, catheters may seem to be preferable to other forms of access, at least at first glance. Patients with catheters do not have to undergo venipuncture with two large-bore (14–15-gauge) needles three times weekly; instead, the catheter is simply hooked directly to the dialysis pump tubing. Percutaneously placed catheters cause relatively little cosmetic disfigurement, especially when compared with the disfigurement caused by grafts and native fistulas, which result in multiple scars and/or dilated tortuous veins on the arms and/or thighs. However, it should be clear from the foregoing that these seemingly patient-friendly aspects of catheters belie their true long-term risks of thrombosis and infection.

CONCLUSION

Although great strides have been made in dialysis catheter technology in the past decade, we are far from having the ideal dialysis catheter at our disposal. It is my belief that the next quantum leap in catheter technology will be the development of biologically invisible catheters; judging from advances made in other areas of medicine involving permanent implants, I believe this "Holy Grail" may not be far away. As new technologies and catheter designs emerge, however, it continues to be incumbent upon all users of dialysis catheters to urge the performance of prospective randomized trials before accepting claims associated with new catheter technology. Interventional radiologists are now ideally positioned to be leaders in the performance of such trials.

Acknowledgments

The author thanks Biolink, Middleboro, Mass; Medcomp, Harleysville, Pa; Bard Access Systems, Salt Lake City, Utah; AngioDynamics, Queensbury, NY; and Vasca, Tewksbury, Mass, for supplying information regarding their products. Thanks to Kathie Pedersen, MA, for secretarial support and to my partners, who have helped generate much of the published data described herein.

Footnotes

Abbreviations: DOQI = Dialysis Outcomes Quality Initiative, r-tPA = recombinant tissue plasminogen activator

References

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