Department for Vascular Surgery, Stadtklinik Baden-Baden, Baden-Baden, Germany
Keywords: catheter-associated bacteraemia; central venous catheters; complications; haemodialysis; haemofiltration; review
Introduction
Large-bore central venous catheters (CVC) play an important role in the treatment of acute renal insufficiency [1]. They represent the only means for immediate vascular access in cases of urgently needed renal replacement therapy (RRT). Bedside implantation is possible even in the emergency room and during cardiopulmonary resuscitation.
Cuffed tunnelled catheters are used for RRT of intermediate duration and even for chronic haemodialysis in patients where peripheral arteriovenous access is felt to be problematic or impossible. Recently, subcutaneous port devices have been developed, suggesting that in the near future central venous access might become an acceptable and reliable alternative to a functioning arteriovenous fistula.
Thus, it seems worthwhile to update the literature with respect to what we know and do not know about acute and chronic central venous access for haemodialysis.
Which catheter material and design?
A variety of plastic materials including polyvinyl chloride, polyethylene, polyurethane, and silicone is used in the production of CVC for haemodialysis. In animal experiments, silicone was shown to be less thrombogenic than other materials [2,3]. Trials systematically comparing CVC made from different materials to assess their respective rates of infection or thrombosis in haemodialysis patients have not been published.
The design of commercially available catheters varies greatly as far as the configuration of holes at the catheter tip is concerned. Some have end-holes only and some have end- and side-holes. Side-holes can be in linear or in spiral array. Arterial inlet and venous outlet holes in different double-lumen catheters have different distances between. These variables in design have never been investigated systematically to assess their influence on catheter function, recirculation, and occlusion rates [4].
Tunnelled or non-tunnelled catheter?
When acute RRT is needed, transcutaneous implantation of a non-tunnelled large-bore CVC provides the easiest and quickest access to the patient's bloodstream. Its use should be restricted to the first 1 or 2 weeks of haemodialysis or haemofiltration. Prolonged residence times are associated with a high risk of catheter-associated bacteraemia and central venous obstruction (later possibly complicating peripheral arteriovenous access) [5,6].
A tunnelled catheter is believed to be less prone to infectious complications than a non-tunnelled one [7,8], although this has never been systematically investigated. There are also some reports of surprisingly low rates of catheter-associated bacteraemia, even in non-tunnelled catheters [9]. A DacronTM cuff placed in the subcutaneous tissue near the insertion site of a tunnelled catheter allows for complete fibrous sealing of its skin entry, thus providing an efficient barrier against tunnel infections. Therefore, implantation of a cuffed, tunnelled catheter is recommended as soon as it becomes clear that prolonged RRT (more than 2 weeks of haemodialysis or haemofiltration) is needed. However, local infection of the insertion site and bacterial invasion along the catheter hub remain major problems in cuffed, tunnelled catheters (Table 1).
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Single- or double-lumen catheters, or twin catheters?
Recirculating blood reduces the efficiency of RRT. Double-lumen CVC are widely believed to reduce recirculation rates when compared to single-lumen CVC [10]. Reliable data, however, are again lacking [4]. The trade-off for such hypothetical benefit is greater acute trauma during implantation and greater chronic trauma due to enhanced catheter stiffness. It is questionable whether simultaneous implantation of two (twin) catheters [11] reduces surgical trauma and complication rates [12,13]. Recirculation rates of twin catheters equal those of double-lumen catheters (Table 2).
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Which central vein?
Subclavian vein
Subclavian-vein cannulation is burdened with a 10% rate of severe acute complications such as arterial puncture with haemothorax and pneumothorax [14]. Moreover, when a large-bore haemodialysis catheter remains in place for more than 2 or 3 weeks, there is a 4050% risk of subclavian-vein stenosis or occlusion [5,1517]. Chronic obstruction of a subclavian vein, of course, will complicate later construction of a peripheral arteriovenous access on that arm. After occlusion of both subclavian veins, major reconstructive surgery or a thigh access will be necessary. Therefore, a subclavian haemodialysis access should not be selected as long as other central veins can be punctured [18].
Internal jugular vein
The right internal jugular is seen as the ideal vein for haemodialysis access. It runs straight down to the superior vena cava, which obviously reduces the risk of malposition of the catheter [14], and possibly also of central venous obstruction [1517]. There is, however, a great variability of the vein's calibre and its position in relation to the common carotid artery [19,20]. Ultrasound guidance is therefore strongly recommended to reduce the 710% risk of carotid puncture to virtually zero [21,22]. The surgical implantation of a tunnelled catheter seems to be a safe alternative. It can easily be performed under local anaesthesia after exposure of the internal jugular vein through a short incision [18,23].
A left internal jugular-vein catheter has to overcome two right angles to make its way down to the superior vena cava. This will occasionally cause problems during implantation. Moreover, with every movement of head and neck, a left internal jugular vein catheter will rub on the endothelium of the left subclavian and innominate veins. Wall-adherent thrombi with subsequent central-venous stenosis or occlusion and a high frequency of catheter dysfunction are the consequences [13].
External jugular vein
Because of its superficial course, cannulation of the external jugular vein is possible in most patients without ultrasound guidance. On both sides it opens into the subclavian vein almost at a right angle. This occasionally complicates implantation of stiff, large-bore CVC [18], and of course in the long run will provoke subclavian-vein stenosis and thrombosis.
Common femoral vein
Venous access in the thigh avoids the potential risks of pneumothorax, haemothorax, cardiac arrhythmia, and pericardial tamponade. It can easily be achieved during cardiopulmonary resuscitation and in dyspnoeic patients who are not able to lie flat. Especially in adipose individuals, ultrasound guidance will help to reduce the frequency of inadvertent arterial puncture [21]. In comparison to mediastinal-vein cannulation, the frequency of catheter-associated bacteraemia is obviously higher (Table 1), even when tunnelled catheters are used [24,25]. For haemodynamic reasons, high rates of recirculation are encountered when the catheter tip is located in the iliac vein. This problem can be solved with long catheters (20 cm or longer, Table 3
) and ultrasound or X-ray control of the catheter tip, which should be located in the inferior vena cava [2527].
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Percutaneous or surgical implantation?
Most large-bore CVC for haemodialysis come with a complete implantation set including a Seldinger guide-wire, an over-the-wire dilator and a peel-away tool for catheter insertion. With ultrasound-guided cannulation of the vein and X-ray control of the course of the guide wire and later the position of the catheter tip (in the right atrium), percutaneous implantation can be performed safely and quickly, as long as any forcible manipulation is avoided [28]. Surgical implantation should be considered after multiple previous cannulations or after neck surgery (thyroid resection, carotid artery reconstruction, etc.), or when ultrasound guidance is impossible or has failed [18,23].
Complications
Catheter dysfunction and occlusion
Primary malposition or later dislocation of the catheter tip will result in inadequate flow due to intermittent adherence of the arterial opening(s) to the vein wall. This problem can be overcome by exchanging inflow and outflow lines (Table 2), but with the consequence of unpredictably high and sometimes excessive recirculation rates [4,2931]. Interventional repositioning of the catheter tip or catheter exchange are necessary to allow for an efficient haemodialysis [32,33].
Depending on the time of implantation, partial or complete catheter occlusion occurs in 3060% of CVC for haemodialysis [34]. A thrombus in the catheter hub can often be dissolved by local thrombolysis [35]. A thrombus at the tip of the catheter or a fibrin sheath around it may resist local thrombolysis if it is not reached by sufficient concentrations of the drug. One can try to strip off the thrombus using a transfemoral approach and a Dormia basket [36]. If this manoeuvre fails, catheter exchange is necessary.
Catheter-associated bacteraemia
The micro-organisms most frequently isolated during catheter-associated bacteraemia are Staphylococcus aureus and Staphylococcus epidermidis [37,38]. They reach the patients bloodstream via the catheter tunnel or via the catheter hub. The biofilm regularly found on the inner and outer surfaces of the catheters serves as culture medium [39]. Femoral-vein catheters have a higher risk of infection (and cause catheter-associated bacteraemia earlier) than subclavian or internal jugular-vein catheters [8,9,40]. Multiple-lumen catheters have a higher risk than single-lumen catheters [41]. Non-cuffed catheters probably have a higher risk than cuffed ones [7,8].
Silver coating of CVC for haemodialysis fails to reduce catheter-associated bacteraemia rates [42]. Impregnation of the catheter surface with heparin, antiseptics, or antibiotics has not been investigated in haemodialysis patients. Nasal mupirocin ointment obviously lowers the frequency of catheter-associated bacteraemia when applied to both patients and nurses [43]. Mupirocin also reduces infectious episodes when applied to the catheter insertion site of non-tunnelled catheters [44]. For cuffed catheters, bacterial cultures of the catheters contents at regular intervals have been recommended, together with consequent application of urokinase (to dissolve the biofilm), and antibiotics after evidence of bacterial growth, even before signs and symptoms of infection [45].
In the majority of patients manifest catheter-associated bacteraemia will not be cured by antibiotics alone [46]. In two recent studies, guide-wire exchange of infected tunnelled catheters together with 3 weeks of antibiotics was shown to be successful only in selected patients with mild symptoms of local or systemic infection [47,48]. Infected non-cuffed catheters and cuffed catheters with severe, recurring, or treatment-resistant infection must be removed.
Central-venous obstructions
The frequency of catheter-associated central-venous stenosis and occlusion is as high as 4050% after cannulation of the subclavian vein [5,15,16], and may reach 75% once the subclavian catheter has been infected [6]. Most of these obstructions do not cause symptoms because they develop slowly and venous collaterals have time to develop. However, when an arteriovenous access is created at a site distal to the obstruction, the collateral transport capacity will be overloaded and the arm will swell. Puncture will then be difficult and the risk of bleeding, haematoma, and infection will be enhanced. Several treatment options exist for venous hypertension. Percutaneous dilatation of the stenosis (with or without stent implantation) is often successful and provides satisfying mid-term results [49,50]. When interventional treatment failed or was impossible, venovenous bypass surgery can be considered [51]. In patients unfit for major surgery, access ligation and construction of a new one on the other arm or in the thigh should be preferred.
Long-term renal-replacement therapy
Arteriovenous or central-venous access?
Infection is a major cause of death in end-stage renal disease (ESRD) patients. Central venous access has been shown to be the most important independent risk factor for infection in patients on long-term RRT. The relative risk of bacteraemia is more than sevenfold higher in CVC patients than in fistula patients [52], and catheter-associated bacteraemia is burdened with a 2238% rate of metastatic complications or death [38,46]. In relation to fistula patients, mortality is increased by 50% in diabetic and by 70% in non-diabetic CVC patients [53]. The relative risk of infection-related death is twofold higher in patients with a chronic central venous access. Even the risk of death from cardiac causes is significantly enhanced when compared to ESRD patients with arteriovenous fistulae [53].
Furthermore a peripheral arteriovenous access has been shown to be more reliable than CVC in terms of recirculation, flow rates achieved, and Kt/V delivered [54]. Unassisted 1-year survival of tunnelled, cuffed catheters has rarely been reported but may be as low as 9% [34]. Secondary 1-year survival rates were reported to vary between 25 and 93% [11,55]. In summary, the classical arteriovenous (BresciaCiminoAppel) fistula remains the gold standard for vascular access in chronic haemodialysis. Neither its favourable primary and assisted patency rates nor its low complication rates have ever been reached by any other type of access.
There are, however, some patients in whom the surgical creation of an arteriovenous fistula is felt to be impossible or at least seems to entail significant risks. This is especially true for patients with severe cardiac insufficiency at the initiation of RRT. After some weeks of haemodialysis via a tunnelled CVC, cardiac function should be re-evaluated to identify those patients with improved cardiac state who may then be fit for a peripheral arteriovenous fistula. In patients with severe peripheral arterial disease, it may be impossible to create an arteriovenous fistula. In some of these patients, however, more central arteriovenous bridge grafts can be implanted without the risk of peripheral steal syndrome. Central arteriovenous grafts also are a good option for patients with multiple previous operations and exhausted superficial veins, or for patients with repeat occlusions of peripheral access due to severe hypotension or hypercoagulation.
Port device for long-term RRT?
Today, there are two different completely implantable central venous access devices on the market for use in chronic RRT [56,57]. Both devices are extremely expensive. The published information on function and complication rates is limited (Table 1). Despite special prophylactic techniques to control infection, the reported bacteraemia rates are no lower than those of cuffed catheters [56,58,59]. Comparative studies have so far not been performed.
Conclusion
Non-tunnelled CVC allow for immediate and effective vascular access in patients in urgent need of RRT. The high frequency of early and late complications, however, should be sufficient reason for the exercise of great care with respect to indication, implantation, and surveillance. Unfortunately it is not at all clear which catheter material and design is best suited for haemodialysis access. It is also uncertain whether impregnation of the catheter with antiseptics or antibiotics might help reduce complication rates.
In case of emergency, the femoral vein should be preferred. Whenever possible, the right internal jugular vein should be preserved for early implantation of a tunnelled, cuffed catheter, which should be considered as soon as it becomes clear that RRT will be necessary for more than 1 or 2 weeks. In patients with terminal renal failure requiring long-term RRT, a peripheral arteriovenous access should be created at the time when a tunnelled catheter is inserted. All other catheter patients need regular re-evaluation of their renal function to identify in time those in need of a permanent access.
From the aspect of catheter and patient survival, permanent catheter is a contradiction in terms. Haemodialysis via CVC is less effective and reliable than via an arteriovenous access. A CVC reduces the success rates of later arteriovenous access procedures, enhances the risk of infection, and as a result of these complications reduces the patient's life expectancy. The same has to be suspected for totally implantable devices as long as prospective studies have not shown any significant advantage over tunnelled, cuffed catheters.
Notes
Correspondence and offprint requests to: Dr Volker Mickley, Department for Vascular Surgery, Stadtklinik Baden-Baden, Balger Str. 50, D-76532 Baden-Baden, Germany. Email: V.Mickley{at}Stadtklinik\|[hyphen]\|Baden.de
References