The percentages of patients undergoing dialysis with vascular catheters have been increasingly high in Europe, ranging from 15% (Germany) to 50% (Great Britain) of all haemodialysed patients. In the United States, up to 60% of patients start therapy with haemodialysis central venous catheters (HCVCs) [1]. Over the last decade, the number of patients starting HCVC therapy doubled [2]. According to the Dialysis Outcomes and Practice Patterns Study, 18% of patients with end-stage renal failure in the United States and 24% of those in Great Britain have been dialysed with such catheters [3]. Nevertheless, the provision of an adequate vascular access for haemodialysis remains one of the major challenges.  To achieve the optimal vascular access for the procedure in question, each case should be managed individually.

Haemodialysis requires secure vascular access with an adequate rate of blood flow. In chronic cases, such accesses are ensured by arteriovenous fistulae or synthetic grafts made of polytetrafluoroethylene. Recently, haemodialysis central venous catheters have been commonly used. They are essential when urgent or even emergent vascular access is needed; they are also increasingly popular in patients with end-stage renal failure. Their disadvantages include: high incidence of complications, impermanence compared with other vascular accesses, and lower blood flows [4, 5].

There are two main categories of HCVCs: temporary, usually non-tunnelled, and long-term tunnelled catheters. Their popularity is associated with the fact that they can be used in any patient immediately after the introduction into the vein [6, 7, 8, 9, 10].

An ideal HCVC is biologically neutral and does not induce venous or catheter lumen thrombosis; its surface is coated with an agent, which prevents migration and multiplication of bacteria. It should enable continuous dialysis with the blood flow through the catheter > 350-400 mL min-1. Moreover, it ought to be atraumatic, soft, easy to insert, mechanically durable, bending-resistant, comfortable for the patient and inexpensive. 

The indications for HCVC insertion depend on its type [11, 12, 13]. Temporary catheters (non-tunnelled) are emergently implanted in acute renal failure cases, intoxications requiring haemodialysis, plasmapheresis and during healing of an arteriovenous fistula (about 3 weeks). Long-term catheters (tunnelled) are used in similar cases when more than 3 weeks of dialysis is needed. The latter ones are also used in patients awaiting renal transplants during the preparation of access for peritoneal dialysis, those with sudden dysfunction of an arteriovenous fistula, after access removal due to infection.

TEMPORARY CATHETERS IMPLANTED EMERGENTLY

To ensure continuous, independent blood flow, catheters are double–lumen. The distal part has two separate openings; one collecting the patient`s blood − “arterial”, located 2-3 cm from the catheter end and the second one pumping the blood to the patient − “venous”, placed at its end (Fig.1). Temporary catheters are made of stiff materials: polyurethane or polyvinyl, and thus are easier to introduce along the guide and the haemostasis valve is not needed. The sharp distal tip facilitates the insertion through the subcutaneous tissues. Compared to soft catheters, they are more resistant to bending in the vessel. At body temperature, after contact with the bloodstream, they become plastic, which reduces the risk of vessel damage. Temporary HCVCs have no cuffs, the so-called dacron muffs, do not require tunnelization, thus fast access to the circulatory system can be provided. They vary in length, therefore the proper choice is easier depending the puncture site and availability of a central vessel. They may be used for several days or weeks. Their main asset is easy insertion into the vessel using the Seldinger technique, easy replacement not requiring expensive accessory devices, which may not be always available, e.g. fluoroscopy or ultrasound. Generally, the blood flow through temporary HCVCs is limited to 200-250 mL min-1; nevertheless, continuous haemodialysis is feasible.

The newer catheters are made of silicone and their internal diameter is bigger, which ensures the blood flow of 400 mL min-1 (or even higher); some of them are tunnelled. Silicone used makes them softer than traditional ones yet they have to be inserted using a dilator and peel-away sheath. The position of soft HCVCs should be confirmed by fluoroscopy. If long-term dialysis is needed, tunnelled catheters should be emergently implanted.

LONG-TERM TUNNELLED CATHETERS

Tunnelled HCVCs with cuffs are made of silicone, silastic or carbothane elastomer, polyurethane co-polymer and polycarbonate − the materials softer and more plastic than those used in temporary catheters [10, 14, 15]. Therefore, they are usually inserted using the Seldinger technique via peel-away sheath. Subcutaneous tunnelization and a cuff are to stabilize the catheter and prevent the spread of infections. The soft silastic elastomer enables the placement of the distal catheter tip in the right atrium, which should be fluoroscopically confirmed. Bigger internal diameters (thicker catheters) provide better blood flows, which cannot be achieved with thinner temporary catheters. A thicker catheter requires, however, the use of a wider dilator, thus the opening in the vein must be bigger.

The first model of a tunnelled catheter (Fig. 2) was PermCath, the thik oval catheter with two circular canals. The next model designed was VacCath, oval with the internal septum dividing the internal lumen into two parts. The oval transverse section of the catheter facilitated its insertion through the peel-away sheath. The third popular option was the introduction of two catheters with a single lumen – Tesio. One collected the blood through the opening in the superior vena cava and the other one supplied blood through the opening in the right atrium. At present, the modified Tesio catheters are popular, i.e. two catheters joined by external surfaces along some of their length. Irrespective of the type (non-tunnelled, or tunnelled) or design (straight or with formed shape), their use is likely to be associated with complications [16, 17, 18].

The newest catheters implanted surgically are equipped with the port implantable subcutaneously [16, 17, 18, 19], which prevents percutaneous device-related complications. In most cases, the port consists of a chamber with the silicone membrane and an attachable catheter, e.g. LifeSite port (Fig. 3). The port chamber is made of titanium, ceramics or other neutral plastic materials. The silicone membrane enables repeated penetrations (about 1000-2000), depending on the product and size of a puncture needle. The entire system is placed under the skin, which prevents infections or accidental opening. There are several configurations of the catheter and port chamber. The simplest one involves one catheter and one-chamber port. In such cases, haemodialysis is performed by inserting two 12 F catheters into the internal jugular vein connected with two separate ports, placed to the pocket created between the skin and thoracic fascia: one is used as an arterial access, the other one as a venous access. Another option is a double-lumen catheter connected to a two-chamber port. Still another possibility is the connection of two catheters to a two-chamber port (Fig. 4).

The vascular port implantation is based on the same principles as those for central venous access. The first stage is the puncture of the vena cava and insertion of the haemodialysis catheter, which is followed by creation of the subcutaneous pocket for the port chamber. The final stage is subcutaneous tunnelization of the haemodialysis catheter from the central vein injection to the site of port chamber implantation and connection of the system. The port can be punctured with normal haemodialysis needles or needles with special cut. In the latter case, the angle of the needle head is smaller thus its penetration through the membrane is more difficult; on the other hand, it does not cut an opening in the membrane. The main reason of low popularity of haemodialysis ports is their relatively high cost.

SITE OF CENTRAL VEIN PUNCTURE FOR HAEMODIALYSIS

Depending on the site of catheter insertion, its suitable length should be chosen. The length of catheter introduced from neck or thoracic access should enable its distal end to reach the right atrium, when a soft catheter is used (Fig. 5) or be placed in the superior or inferior vena cava when a catheter is stiff. The soft catheter, if not located properly in the vein (at some angle to its wall), will not function adequately and will be quickly occluded. It is recommended to place HCVCs under US guidance and a fluoroscopic lamp to avoid trauma; the distal part of catheter should be placed in the optimal vascular position [24, 25, 26].

The first choice for catheterization is the right internal jugular vein, followed by the right external jugular vein, left internal jugular vein, left external jugular vein, and finally femoral veins or external iliac veins (Fig. 6) [27, 28]. If these vessels are not accessible, the subclavian vein opposite the dominating side should be used, i.e. the right subclavian vein in the left-handed and the left subclavian vein in the right-handed patients. The subclavian vein should not be catheterized on the side of the unhealed arteriovenous fistula. Whenever none of these typical central accesses is available, alternative methods may be used: catheterization of the inferior vena cava, or hepatic, renal, intercostal and mediastinal veins.

ACCESSES THROUGH INTERNAL JUGULAR VEINS AND EXTERNAL JUGULAR VEINS

The preferred place of HCVC insertion should be the right internal jugular vein due to its course along the axis of the vena cava and shorter distance from the puncture site to the right atrium, thanks to which the number of complications is lower. The mean time of long-term catheter use introduced in the way described above is over 600 days; if inserted through the left internal jugular vein – over 400 days [19]. The external jugular veins are less frequently used due to the problems associated with insertion of the catheter to the superior vena cava [29, 30]. They are, however, a good alternative of haemodialysis vascular access, particularly in patients with the impaired clotting system when abnormalities cannot be corrected before the procedure.

ACCESSES THROUGH FEMORAL AND EXTERNAL ILIAC VEINS

Such accesses for HCVC insertion are recommended in bed-ridden patients; therefore, they are used in ITUs, particularly in patients requiring artificial lung ventilation, after head and neck trauma with numerous catheters and drains of the neck and thorax as well as those with tracheostomy [31, 32]. 

The risk of bacteraemia during tunnelization of HCVC inserted through the femoral vein is comparable to that in catheters placed through the internal jugular vein. Extremely meticulous hygiene of the puncture site is required. The patency period from the insertion to removal is markedly shorter in HCVCs inserted from femoral vein access – about 60 days compared to catheters inserted through the internal jugular vein – over 300 days [27]. The insertion through the femoral vein is not recommended in patients qualified for renal transplantations as it may cause constriction or thrombosis of the iliac veins into which renal veins of the transplanted kidney are implanted. To reduce the blood re-circulation, catheters inserted through femoral and iliac veins should be adequately long (27-50 cm). However, it should be remembered that the longer the catheter the higher the blood flow resistance.

ACCESS THROUGH SUBCLAVIAN VEINS

The subclavian vein should not be the first choice for cannulation. The maintenance of HCVC in the subclavian vein results in its constriction or thrombosis in 42-50% of cases [33, 34, 35], whereas in cases of the internal jugular vein only in 0-10%. Such complications are often asymptomatic, which, in the future, makes the creation of the arteriovenous fistula impossible.

CATHETERIZATION-RELATED COMPLICATIONS

The main factors determining the development of complications during insertion of HCVCs are experience of the operator and use of real time imaging techniques or otherwise [36]. Even in skilled hands, the catheter insertion based only on topographic anatomy is associated with the incidence of complications reaching 5.9% [20, 21]. The complications include cardiac arrhythmia, pneumothorax, pleural or mediastinal haemotoma, air embolism, thoracic tract injury, damage to nervous structures within the neck and thoracic region, puncture of the cardiac cavities, or cardiac arrest [33, 34, 35].

The use of ultrasound guidance during central venous catheterization reduces the number of procedure-related complications to 0.8% [28]. The meta-analysis concerning this issue demonstrated that US-guided catheterization limited the incidence of failures related to catheter insertion into the vein as well as of complications and necessity of multiple punctures of a vessel [26]. The US-guided evaluation of veins in the group of 104 patients showed that in 27% of cases the course of the internal jugular vein was atypical, which could cause difficulties during catheterization based exclusively on the knowledge of anatomy [24]. In the population of patients with chronic renal failure undergoing ultrasound examinations, 18% of those referred to internal jugular vein catheterization had the thrombus constricting or completely occluding its lumen or the vein was lacking. Even for those experienced in central venous catheterization, the US confirmation of the vein presence, determination of its course and patency see
m essential.

Remote complications are equally important. The commonest one is constriction of the subclavian vein. Thrombotic complications and infections are also relevant. To reduce their number, the internal surface of catheters is often coated with heparin. Coating or impregnation of catheters with silver salts and antibiotics reduces the colonization of bacteria.

CONCLUSION

HCVCs are commonly used in patients with renal failure requiring dialysis once other vascular options have been exhausted. Long-term catheters should be inserted using the Seldinger technique with a dilator and haemostasis valve [37, 38, 39, 40]. Such catheters are preferred for dialyses longer than 3 weeks; the key asset is their possible use immediately after radiological control of the intravascular position. It is recommended to insert them under US- and fluoroscopy-guidance. Tunnelled catheters with cuffs may be used both temporarily and permanently. The subcutaneous tunnel and cuff ensure stabilization of their position while fibroblasts growing into the cuff limit the migration of microorganisms on its external surface and reduce the risk of infections.

It is worth emphasizing that a well-functioning arteriovenous fistula is the best vascular access inducing the lowest number of complications.

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address:

*Jacek Wadełek
Oddział Anestezjologii i Intensywnej Terapii
Szpital Wolski im. dr Anny Gostyńskiej SPZOZ
w Warszawie
ul. Kasprzaka 17, 01-211 Warszawa
tel.: 22 38 94 733
e-mail: WAD_jack@poczta.fm

received: 22.04.2010
accepted: 15.07.2010