Hemodialysis Access: Catheters and Ports



Hemodialysis Access


Catheters and Ports


Hyeon Yu, Kyung Rae Kim and Charles T. Burke



Introduction


In the United States, the number of patients with end-stage renal disease (ESRD) has been rising each year (often by > 10%), and more than 300,000 individuals undergo hemodialysis treatment.1 Each of these patients needs some form of vascular access to allow sufficient blood flow to the dialyzer for adequate hemodialysis, which is administered three times weekly. Maintaining vascular access patency and function for these patients is an essential component of their care.


The Clinical Practice Guidelines and Recommendations of the National Kidney Foundation Kidney Disease Outcomes Quality Initiative (NKF KDOQI) state that an ideal vascular access should have the following characteristics: optimum flow rate for adequate hemodialysis, long use-life, and low rate of complications (e.g., infection, stenosis, thrombosis, aneurysm, and limb ischemia).2 Although no currently available vascular access can perfectly meet these criteria, the surgically created native arteriovenous fistula (AVF) has been reported to have the best patency rates, require the fewest interventions, and have the best results following interventions compared to other types of vascular access.35


Despite the NKF KDOQI Vascular Access Guidelines that recommend increased placement of AVFs and decreased use of hemodialysis catheters, 10% of total vascular accesses, the patient population with ESRD receiving hemodialysis via catheters has steadily increased from 13% to 25%. This increase of hemodialysis catheters may be partly attributed to advanced patient age, comorbid conditions such as peripheral vascular disease and diabetes, and late referral for creation of an AVF.6 Hemodialysis catheters still play an important role, not only as a temporary access for patients with acute renal failure but also as a bridge until a more definitive form of vascular access is established.


Currently, there are three different types of hemodialysis catheters available: tunneled cuffed catheters, nontunneled catheters, and ports. This chapter reviews the use of these different types of catheters, techniques of initial placement, and interventional procedures for managing complications associated with hemodialysis catheters.



Indications


According to the guidelines and recommendations developed by the NKF KDOQI Vascular Access Work Group, one of the goals to improve patients’ survival and quality of life is to increase the placement of AVFs. Recently, the target for fistula creation has been reset at 65%.2


For patients in whom an AVF cannot be created because of anatomic or technical limitations, an AV graft is the next best option. Typically, a fistula requires approximately 3 months for maturation, and a graft 6 weeks to mature before use. Before fistula or graft creation and during maturation periods, patients may require placement of a dialysis catheter or port.


Patients awaiting renal transplantation or creation of peritoneal access for peritoneal dialysis also have an indication for placement of a hemodialysis catheter or port. Patients who undergo continuous ambulatory peritoneal dialysis may need temporary hemodialysis access via a catheter or port while their peritoneal dialysis access heals or during episodes of peritonitis.


Hemodialysis catheters or ports are also indicated in patients who are not candidates for surgical access. These include patients with anatomic issues such as venous or arterial stenosis or occlusion and patients with severe comorbid conditions that could make the presence of an AV shunt dangerous.


Despite NKF KDOQI recommendations, decreased durability, and a higher rate of complications with catheters, some patients may nonetheless prefer them to AVFs and grafts.7 One significant difference for the patient is the necessity for needle access to the fistula or graft at two separate skin sites during each dialysis session, versus painless direct connection of the dialysis catheter to the dialysis machine.



Contraindications


The use of hemodialysis catheters as primary vascular access should be minimized because of the high risk for infection and high malfunction rate. The NKF KDOQI Vascular Access Work Group strongly recommends that catheters be used in less than 10% of hemodialysis patients as their permanent chronic hemodialysis access.2


Prolonged presence of a catheter that traverses the central veins may result in central venous stenosis or occlusion. Because the likelihood of this problem increases with the duration of indwelling central access, long-term use of catheters is generally contraindicated in patients with other potential access options.


The preferred site of catheter placement is the right internal jugular (RIJ) vein because of its more direct route to the right atrium than the left-sided venous approach. Catheter placement in the left internal jugular (LIJ) vein may potentially limit permanent access options on the left arm by inducing stenosis or occlusion of the left brachiocephalic vein. It has been reported that catheter placement in the LIJ vein may be associated with decreased blood flow rates and increased risk for stenosis and thrombosis.8,9


Catheter placement in the subclavian vein on either side should be avoided because of the risk for stenosis,10,11 which can significantly reduce the possibility of future upper extremity permanent AVF or graft.


Catheters should not be placed in the vein on the same side as a slowly maturing permanent access. Central venous stenosis due to catheter placement is closely linked to the site of insertion,12,13 number and duration of catheter uses, and occurrence of infection.12,14


Although the common femoral vein may be used for nontunneled temporary access, longer-term access with tunneled catheters and ports is suboptimal and relatively contraindicated because of the higher rate of infection at this site.15


In general, active infection or bacteremia are contraindications to placement of a tunneled catheter or port, owing to the high risk for infection in the subcutaneous tunnel or port site. Underlying causes of infection should be managed prior to the procedure. To avoid bleeding complications, patients with coagulopathy or thrombocytopenia should be corrected to an international normalized ratio (INR) of less than 1.5 and platelet count over 50,000/mm3. A nontunneled hemodialysis catheter can be temporarily used until the patient’s condition improves.



Equipment


A variety of different types of hemodialysis catheters are produced by a number of manufacturers. Although there may be slight differences between them, they are all based on the same principle and are used in the same way.


According to the duration of use, hemodialysis catheters can be divided into acute short-term nontunneled catheters and long-term tunneled cuffed catheters. Tunneled cuffed catheters and ports are considered as vascular accesses for hemodialysis over weeks to months.2



Nontunneled Catheter


Nontunneled catheters are designed for temporary hemodialysis access, especially in patients who need acute renal replacement therapy (Fig. e121-1). Although these catheters are ready for immediate use, they have a limited use-life and therefore should not be placed until they are absolutely needed. It is recommended that IJ nontunneled catheters should not be used for more than 1 week because of an infection risk.1618 These catheters directly enter a central vein, with no intervening tunnel beyond the skin entry site, so infection is a greater risk over the long term. After 1 week, the infection rate increases exponentially.19




The catheters are most commonly placed via the IJ vein under ultrasound and fluoroscopic guidance. Although they can be placed at the bedside, ultrasound-guided venous access is still strongly recommended to prevent placement-related complications. After bedside placement of the catheter, a chest radiograph is essential to confirm the position of the tip in the right atrium.


The femoral vein may occasionally provide an alternative access route when necessary, but it should be used for no more than 5 days because of the increased risk for infection.15 The tip of the femoral nontunneled catheter should be positioned in the inferior vena cava to reduce recirculation.20


A patient with a nontunneled hemodialysis catheter should not be discharged while awaiting the next hemodialysis, owing to the risk for infection, inadvertent dislodgement, hemorrhage, air embolism, and discomfort. Before discharge, a short-term nontunneled catheter should be exchanged for a tunneled cuffed catheter unless there is active infection.21



Tunneled Cuffed Catheter


Tunneled cuffed hemodialysis catheters are designed to function as more permanent access devices and can remain in place for several months or, in some patients, even years at a time. These catheters are preferably and most commonly placed via the RIJ vein under ultrasound and fluoroscopic guidance. Tunneled catheters generally take a curved course along a path that extends first upward from several centimeters below the clavicle through the subcutaneous tunnel to the RIJ vein entry site on the lower part of the neck and then downward into the central veins and right atrium.


Tunneled catheters have a Dacron cuff around a portion of the catheter that will sit within the subcutaneous tunnel. Ingrowth of subcutaneous tissue into the cuff makes it adherent to the tunnel and “seals” the tunnel. This is thought to help prevent migration of bacteria from the skin surface along the catheter and into the bloodstream, thereby guarding against infection.22 The cuff also helps retain the catheter and thus prevents dislodgement and malpositioning (Fig. e121-2).




Most hemodialysis catheters have two separate channels or lumina. The arterial lumen allows blood to be collected from the patient so it may pass through the hemodialysis machine. The venous lumen allows dialyzed blood to be returned to the patient. Both lumina extend the entire length of catheter, and although they are separate from each other externally, they join at the hub to form a single catheter with two channels running inside it.


Unlike infusion catheters, to be effective, hemodialysis catheters must have two different locations where the two lumina communicate with the bloodstream. In this way, blood can be collected upstream and then returned after passage through the hemodialysis machine in a relatively downstream location. This prevents the catheter from recollecting blood that has just passed through the dialysis machine and reentered the patient, an undesirable mixing phenomenon known as recirculation, which will decrease the efficiency of hemodialysis.23


Some catheters communicate with the bloodstream via multiple side holes at different distances from the catheter tip for each lumen. Others have two lumina of different lengths that allow one to end above the other, known as the step-tip design (PermCath [Covidien, Mansfield, Mass.]). Sometimes two single-lumen catheters can be inserted separately. There is at least one commercially available system that uses two completely separate and separately tunneled catheters (Tesio twin dialysis catheter system [Medcomp, Harleysville, Pa.]).


Catheters vary somewhat in their diameter, with most falling between 11F and 16F. Differences in diameter and end-hole/sidehole arrangement may have some influence on flow rates catheters are capable of achieving. Catheters should be able to deliver a consistent flow greater than 350 mL/min to the hemodialysis machine at prepump pressures of −200 to −250 mmHg. The choice for the best device should be made based on comparison of flow data, local experiences, goals for use, and cost.2


Fibrin sheath formation around the distal portions of hemodialysis catheters has been associated with catheter malfunction and poor flow. In an effort to reduce this problem, some catheter systems have been designed with a split tip (Ash-Split catheter [Medcomp]). In other words, the distal portion of the catheter splits into two separate lumina, just as the proximal external portion of the catheter is divided into two separate lumina. It has been suggested that motion of the two lumina within the bloodstream during the cardiac cycle, including motion of one lumen against the other, will help inhibit the formation of fibrin sheaths.24 Catheters with a split-tip design may also minimize recirculation effect.25,26



Port


Subcutaneous implantable port systems have been developed in an effort to reduce the rate of infectious complications.27-30


Two port systems have been used: (1) the LifeSite Hemodialysis Access System (Vasca Inc., Tewksbury, Mass.), which has U.S. Food and Drug Administration (FDA) approval for implantation in the United States, and (2) the Dialock Access Port (Biolink Corp., Middleboro, Mass.), which is in clinical use in Europe.


The LifeSite hemodialysis port consists of two individual metallic subcutaneous reservoirs, each of which attaches to a 12F catheter with multiple side holes. They are accessed with standard 14-gauge access needles of the type that would be used to access a fistula or graft. The ports automatically lock the needles in place when they are turned.31


The Dialock Access Port is a rectangular septumless device with a titanium shell and two internal valves. On the anterior and inferior portion of the device, there is a shelf with two grooves that are used for two 15-gauge access needles into the tubular chambers. The access needle is locked after passing the valve in the device. Each chamber is connected to an 11F silicone catheter with notched distal end hole.30


Complete subcutaneous location of both port systems may potentially reduce the risk of infection, owing to the natural skin barrier against bacterial introduction. In addition, especially when compared to conventional tunneled catheters, there is a potential for improving patients’ quality of life and reducing lifestyle restrictions. However, exchange of a port system may be more difficult than that of a nontunneled or tunneled hemodialysis catheter.



Technique


Anatomy and Approach


Vascular anatomy is more completely covered elsewhere in the book, so the following will serve only as a brief overview.


The most important approach for all types of hemodialysis catheters and ports is the IJ vein. Accessing the IJ vein at the lowest possible point above the clavicle will help prevent kinking of tunneled catheters. The IJ vein joins with the ipsilateral subclavian vein to form the brachiocephalic vein, which joins with the contralateral brachiocephalic vein to form the superior vena cava (SVC), which conveys blood to the right atrium.


When the IJ vein approach is not available, the external jugular vein may be useful. The external jugular vein sits more lateral and posterior in the neck in relation to the IJ vein and typically empties into the central portion of the ipsilateral subclavian vein.


The subclavian venous approach is rarely used, but one exception is in patients who may no longer have usable arm veins for creation of more permanent access and who also have occlusion of the jugular vein ipsilateral to this arm. In such patients, the ipsilateral subclavian vein may be used if available, because stenosis or occlusion of this vein should not jeopardize the possibility of creation of a future AVF or graft.


Less frequently used approaches include the femoral vein, hepatic vein, translumbar inferior vena cava (IVC), recanalized or collateral veins, and direct approach to the SVC. This is discussed in more detail in the Unconventional Hemodialysis Access section of this chapter.



Technical Aspects




The patient’s history and any available relevant prior imaging studies should be thoroughly reviewed to identify any evidence of central venous stenosis or occlusion before planning the procedure. Informed consent for the procedure must be obtained in advance and should include discussion of its risks, benefits, and alternatives. The patient should be allowed to ask questions if desired.


Before sterile preparation, the patient should be examined thoroughly. Frequently, physical examination will reveal important clues about venous anatomy. The presence of chest wall venous collaterals or arm or neck and facial swelling may be a sign of venous occlusion.


Limited ultrasound examination of the planned access site is very useful for quick assessment of the feasibility of an approach. Strict sterile technique should be used, including sterile preparation and draping of the patient. Currently in most institutions, skin is prepared using 2% chlorhexidine gluconate in 70% isopropyl alcohol (Chloraprep).32 The skin surface should be shaved before sterile preparation if hair is visible. For tunneled catheters placed via the IJ access site, preparation should extend from the upper mid-neck area to the nipple. Full surgical scrubbing is a necessity for all operators, as is the use of surgical caps, masks, and sterile gowns and gloves. Sterile probe covers should be used for ultrasound probes.


For the large majority of patients, a combination of local anesthesia and moderate sedation is well tolerated. Lidocaine 1% with epinephrine is commonly used for local anesthesia, and moderate sedation generally consists of a fast-acting and relatively short-lived benzodiazepine and narcotic combination, such as midazolam and fentanyl. During the entire procedure, the patient should be continuously monitored using electrocardiogram and pulse oximetry by a member of the nursing staff.


Preprocedure antibiotic administration is not required,33,34 with multiple studies demonstrating low infection rates that are comparable or lower than those documented for surgical placement.35


Because the IJ vein is the preferred hemodialysis catheter placement site, discussion will focus on this approach. Real-time ultrasound guidance should be used for IJ venous puncture because it will help guard against complications. The IJ vein should be accessed in the inferior aspect of the neck as close to the superior border of the clavicle as possible. A low puncture will aid in preventing kinking of the catheter as it curves from the subcutaneous tunnel to the venotomy site. After ultrasound is used to select the access site, local anesthesia should be administered. A small, shallow incision or “skin nick” should be made over the access site with a #11 blade (Fig. e121-3image). Use of a hemostat to spread the underlying fascia will facilitate subsequent passage of the peel-away sheath and also aid in preventing catheter kinking at the venotomy site. Through the skin incision, the IJ vein is accessed using a 21-gauge needle connected to a 20-mL syringe by a short connecting tubing under ultrasound guidance. Placement of the needle tip within the vein is confirmed by ultrasound and aspiration of blood through the 20-mL syringe (Fig. 121-1). Under fluoroscopic guidance, a 0.018-inch guidewire is advanced through the needle and subsequently exchanged for a Cope transition dilator (Cook Medical, Bloomington, Ind. [Fig. 121-2]). Some operators prefer an 18-gauge needle for venous access to skip the transition from 0.018-inch to 0.035-inch systems. Others prefer a micropuncture set (Cook Medical) to make the transition to a 0.035-inch system.






Fluoroscopy is used to position the wire tip in the upper to mid–right atrium. The wire is then measured to determine the appropriate catheter length for the patient. Two methods of measurement are commonly used, depending on the preference of the operator. One involves marking the wire at the point where it exits the transition dilator (Fig. 121-3). Then the intravenous portion of the wire can be measured by subtracting the length of the exposed transition dilator from the length of the wire between the tip and the marking. This is the best way to measure the appropriate length for a nontunneled catheter, and many operators also use this measurement to determine the length of a tunneled catheter. However, when placing tunneled catheters, some operators prefer to bend the wire in a curved pathway that simulates the course of the catheter through the tunnel, and mark the wire at a reproducible point intended to be at or near the exit site of the tunnel, such as three fingerbreadths below the clavicle (Fig. e121-4image). The distance from this mark to the tip of the wire is the length from the tunnel exit site to the tip of the intravenous portion of the catheter. The wire is subsequently removed from the transition dilator.

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Dec 23, 2015 | Posted by in INTERVENTIONAL RADIOLOGY | Comments Off on Hemodialysis Access: Catheters and Ports
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