INTRODUCTION — Hemodialysis requires access to blood vessels capable of providing rapid extracorporeal blood flow of 300 to 425 mL/min for three to four hours, three times a week.

When there is an acute (immediate or emergency) need for hemodialysis (eg, acute kidney injury, thrombosed hemodialysis arteriovenous [AV] access, poisoning) in the inpatient setting, a large-bore, nontunneled, double-lumen catheter is most often used. If the duration of hemodialysis with a catheter is likely to be for more than one to two weeks or in a chronic outpatient setting, a tunneled hemodialysis catheter should be used instead. Compared with nontunneled catheters, tunneled hemodialysis catheters are designed to be inserted into the skin several centimeters from the vein entry site. A polyester cuff on the tunneled hemodialysis catheter provides a point for tissue ingrowth inside the resulting subcutaneous tunnel. This can effectively seal the intravascular portion of the catheter from the skin, providing a point of fixation and also reduced infection rates.

Ideally, when permanent hemodialysis access is required, an AV access is placed. Once the fistula or graft can be used reliably, usually three consecutive uncomplicated dialysis sessions, the hemodialysis catheter is removed. A tunneled hemodialysis catheter is a reasonable option for long-term use in some patients, such as those with multiple failed AV access with no available options, limited life expectancy, or anatomic issues that prevent appropriate combinations of inflow artery and outflow veins [1]. (See "Approach to the adult patient needing vascular access for chronic hemodialysis", section on 'Catheter appropriateness'.)

The basic principles governing the use of catheters for hemodialysis and the general features of nontunneled and tunneled catheters are reviewed. An overview of central venous access and placement is discussed separately. (See "Overview of central venous access in adults" and "Central venous access devices and approach to device and site selection in adults", section on 'Benefits/risk for specific sites'.)

DIALYSIS CATHETERS — The broad categories of catheters used for hemodialysis vascular access are nontunneled catheters and tunneled catheters (figure 1). (See "Central venous access devices and approach to device and site selection in adults", section on 'Types of central venous catheters' and "Overview of central venous access in adults", section on 'Central venous access devices'.)

While many types of hemodialysis catheters are available, few trials have systematically compared the various catheters to assess the performance of different materials and catheter tip configurations on delivered dialyzer blood flow rates and rates of infection or thrombosis [2-5]. A document is available proposing standardized definitions for central venous catheters endpoints (catheter-related bloodstream infections, catheter dysfunction, and central vein obstruction) that was developed by a multidisciplinary panel of experts to help guide product development and clinical trials on hemodialysis catheters [6].

Basic principles — Hemodialysis catheters usually have two main lumens attached to two ports (blue and red colored). A third lumen may be present for blood draws and drug delivery. Single-lumen hemodialysis catheters are no longer commonly in use.

By convention, the red port identifies the "arterial" lumen that draws blood from the body (ie, from opening[s] further from the heart) and the blue port identifies the "venous" lumen for return of blood from the dialysis machine to the patient (ie, to opening[s] closer to the heart). This direction of flow may occasionally be reversed on dialysis if blood flow is limited in the conventional direction, though at the risk of increased recirculation, reduced clearance, and possibly inadequate dialysis depending on the configuration of the catheter tip [7-9]. The continuous blood path made possible by the dual-lumen design allows rapid blood flows and a hemodialysis technique that does not require heparin.

Compared with a typical catheter used for central venous access, the hemodialysis catheter is larger (11.5 to 15.5 French [Fr]) to provide a high rate of flow, which requires a corresponding 12 Fr to 16 Fr introducer. As such, the resulting venotomy is about 4 to 5 mm in diameter. The flow rate that a catheter can deliver is determined by Poiseuille's Law, which states that resistance to flow in a tube is proportional to the length of the tube and inversely proportional to the fourth power of the radius. Higher viscosity (in this case increasing hematocrit) also increases resistance. For the same negative inflow pressure, lower hemoglobin (hematocrit) levels produce higher blood flows. At a given negative pre-pump pressure, blood flows are consistently higher with right-sided internal jugular vein catheters compared with left-sided catheters, due in part to additional resistance to flow from the two necessary bends and longer length of the catheter for left-sided access [2]. (See 'Access site considerations' below.)

Nontunneled catheters — Nontunneled hemodialysis catheters are designed for short-term use (<2 weeks) and are the preferred catheter for acute (immediate or emergency) hemodialysis vascular access in the inpatient setting. These catheters should not be used for chronic, long-term, or outpatient hemodialysis. Patients should not leave the hospital with a nontunneled catheter; they must not be used in the home or outpatient setting due to high infection risks and the potential for catheter dislodgement [1].

Many different nontunneled catheters are available and are composed of materials such as polyurethane, polyethylene, polyvinyl chloride, and medical-grade silicone. Nontunneled catheters are supplied in several shaft sizes, configurations (straight or curved), and lengths (9 to 30 cm). The outer shaft diameter ranges from 8 to 13.5 Fr and provides pump flow rates of 300 to 400 mL/minute.

The selection of the appropriate catheter type is at the discretion of the practitioner. The operator should consider the need, requirements, and duration for the catheter, as well as access site location.

To determine the appropriate length, the practitioner should consider the height of the patient and the location from where the catheter is being inserted. Inadequate catheter length can be an issue for taller patients, even when using an internal jugular approach. Catheters inserted from the left side need to be longer, as they have a greater distance to traverse. Catheters inserted from the groin are also longer to reach the inferior vena cava.

Nontunneled catheters are straightforward to insert, though they tend to have a larger caliber than most central venous catheters used purely for venous access. Ultrasound guidance is recommended during catheter insertion. (See "Overview of central venous access in adults", section on 'General technique' and "Principles of ultrasound-guided venous access".)

Most nontunneled hemodialysis catheters have a conically pointed tip and are relatively rigid at room temperature to facilitate insertion, but the catheter generally softens at body temperature to minimize the potential for vessel trauma. Because of the more rigid material, nontunneled catheters can perforate through the great veins or heart, and thus, verification of correct catheter tip positioning is essential. Fluoroscopy or a chest film should be obtained immediately following insertion of the catheter, but prior to its use, to verify the catheter tip position and identify other immediate complications, such as a pneumothorax or air embolism [10]. (See 'Catheter positioning' below.)

Duration of use — The use-life of nontunneled catheters varies with insertion site.

Mechanical malfunction and infectious complications are the principle reasons for limiting the duration of use of nontunneled hemodialysis catheters. The infection rate increases for both the femoral and internal jugular access sites over time. In a study of 318 new hemodialysis catheter insertions, at the end of one, two, three, and four weeks, the incidences of bacteremia for femoral vein catheters were 3, 11, 18, and 29 percent, respectively, and for internal jugular catheters, the incidences were 2, 5, 5, and 10 percent, respectively [11]. Lower rates of catheter-related bacteremia have been reported with the use of various exit-site protocols and locking solutions.

As a result, it is our practice and recommendation to use nontunneled catheters for hemodialysis for less than two weeks, even for patients with acute kidney injury, because of the increased risk for infection compared with tunneled hemodialysis catheters. While recovery from acute kidney injury with the need for hemodialysis is very difficult to predict, only a minority of the patients who require dialysis recover renal function in less than one week [12]. Thus, unless the patient is too unstable for transport to the procedure room, or other contraindications to insertion exist, we place a tunneled catheter.

Femoral catheter use is generally limited to a single dialysis session in ambulatory hospitalized patients, and up to two weeks in bed-bound (eg, intensive care unit) patients [13-16]. Femoral catheters in ambulatory patients are removed after each dialysis session because of difficulty maintaining the catheters in this location, which are prone to malposition and kinking, and resulting issues of safety. If a temporary access is needed for dialysis, a tunneled catheter is preferable to a nontunneled catheter (even in the intensive care unit setting) when the catheter is expected to stay in place for more than two weeks.

Tunneled catheters — Tunneled dialysis catheters are generally double-lumen catheters with a polyester cuff positioned 1 to 2 cm from the skin exit site. Catheters are composed of silicone and other polymers, like thin polyurethane, which are less thrombogenic than the materials used in nontunneled catheters. These catheters are blunt, soft, and more flexible than nontunneled catheters. (See "Central venous access devices and approach to device and site selection in adults", section on 'Tunneled catheters'.)

Tunneled hemodialysis catheters are associated with lower rates of infectious complications compared with nontunneled catheters [14,17]. The hemodialysis catheter is generally placed such that the cuff is positioned subcutaneously 1 to 2 cm from the skin exit site. Tissue ingrowth into the cuff seals off the catheter tunnel to reduce the risk of infection. Tunneled hemodialysis catheters are primarily used for intermediate- or long-term hemodialysis vascular access [18]. Although chronic hemodialysis using an arteriovenous (AV) access is preferred, some patients are poor candidates for AV access creation and will require a hemodialysis catheter long term [1,19]. For critically ill patients, other comorbidities and confounding factors need to be considered [20]. Placement of a tunneled catheter, rather than a nontunneled catheter, is advised for patients with acute kidney injury when it is known that dialysis is likely to be for more than one week (or permanent) [12]. (See "Approach to the adult patient needing vascular access for chronic hemodialysis".)

A wide variety of hemodialysis catheters are available from multiple manufacturers. Tunneled catheters are available in a larger size (15.5 or 16 Fr) that allows for greater blood flow rates (>300 mL/minute) compared with nontunneled catheters (largest 13.5 Fr). Catheters are available in a variety of configurations and tip designs, including double D, coaxial, shotgun, step tip, symmetric, and split tip, among others. The differing designs are claimed to increase blood flow, minimize recirculation, and prevent catheter tip obstruction. Separation of the tips of the catheter can be achieved with a staggered tip design, use of a septum extruding beyond the openings, or splitting the catheter lumens distally. Some catheters are self-centering with a built-in curvature designed to push the tip of the catheter away from the wall of the vessel or heart chamber [8,21]. Despite the wide variety of designs of tunneled hemodialysis catheters, each with its theoretical advantages and disadvantages, the few available randomized trials have failed to show the superiority of one catheter over another, particularly when the endpoint is long-term functional survival of the catheter [2-5,21].

Surface-coated catheters — A variety of surface coatings (eg, heparin, silver, chlorhexidine, rifampin, minocycline) have been used to prevent hemodialysis catheter thrombosis and hemodialysis catheter-related infection [22]. While nonhemodialysis catheters with antithrombotic or antimicrobial coatings have demonstrated some efficacy, few studies are available for hemodialysis catheters, and those that are available provide only short-term outcomes. (See "Central venous access devices and approach to device and site selection in adults", section on 'Coated and impregnated catheters'.)

In early studies, antimicrobial- and antithrombogenic-coated hemodialysis catheters appeared to be effective in preventing intravascular catheter infections in the dialysis setting [23-32]. However, in a systematic review that evaluated 29 trials with 2886 patients and 3005 hemodialysis catheters, the incidence of catheter-related bacteremia and exit-site infections was similar for antimicrobial-coated hemodialysis catheters compared with noncoated catheters [30]. (See "Central venous access devices and approach to device and site selection in adults", section on 'Antimicrobial-impregnated catheters'.)

Heparin-coated catheters have also been used to decrease the incidence of catheter-related thrombosis. In observational studies, the frequency of catheter malfunction and overall catheter survival was similar [32,33]. While the incidence of catheter-related bacteremia was significantly less frequent for heparin-coated catheters compared with noncoated catheters (34 versus 60 percent), infection-free catheter survival was no different [32]. It is important to remember that hemodialysis catheters remain in the patient for several months, which is a critical factor when determining the efficacy of a coating. Randomized trials are needed to demonstrate the longevity of any bonded protection, which ideally should approximate the length of the intended catheter placement. Also, it is important to establish whether any effect remains in settings in which infection preventive care is established and adhered to [32-35]. In the absence of reliable data demonstrating long-term efficacy, the additional cost for these catheters may not be justified [36]. (See "Central venous access devices and approach to device and site selection in adults", section on 'Heparin bonding'.)

Catheter life — The overall survival of tunneled hemodialysis catheters is highly variable. Unassisted one-year use-life (ie, no intervention) of tunneled hemodialysis catheters appears to be as low as 9 percent, but reports are not consistent [37]. Assisted one-year use rates range between 25 and 93 percent [38-42]. One study reported a 74 percent one-year and a 43 percent two-year catheter survival [40]. A larger study of 623 Tesio catheters reported the one-year and three-year postplacement use-life of 78 and 44 percent, respectively [41]. In another study, assisted one-year patency was 50 percent when the catheter was used as a permanent access [42]. Almost all catheter losses were due to bacteremia [43].

CATHETER PLACEMENT — Catheters for dialysis access are placed in a manner like central venous catheter placement for other conditions. An overview of central venous access and the principles of ultrasound-guided access is presented elsewhere. (See "Overview of central venous access in adults" and "Principles of ultrasound-guided venous access".)

Local anesthesia and ultrasound guidance should be used for nontunneled hemodialysis catheters and can be placed at the bedside or in a procedure room. Confirmation of the catheter tip position must be documented using fluoroscopy or chest film prior to use of the catheter. Tunneled catheters are placed with ultrasound and fluoroscopic guidance using local anesthesia, with or without sedation, in an angiographic suite or appropriately equipped operating room due to their larger caliber and the need to tailor the catheter for proper positioning. Catheter malposition is a common problem (25 to 40 percent) when fluoroscopy is not used for guidance; accurate catheter positioning can be achieved in 95 to 100 percent of cases with fluoroscopy [44]. Fluoroscopy also allows direct imaging of the wires and dilators to minimize the potential for injury. (See 'Technique' below.)

Access site considerations — As with any central venous catheter, hemodialysis catheters can be inserted into any of the central veins [45,46]. The choice of the vascular access site and catheter should be guided by the urgency of dialysis, type of dialysis, history of prior access, and the overall medical condition of the patient.

The right internal jugular vein is the preferred vein for hemodialysis access (nontunneled and tunneled hemodialysis catheters) because the vein takes a straight path directly into the superior vena cava (figure 2). Placement of catheters into the left internal jugular vein requires that the catheter make two right angles prior to reaching the superior vena cava, which can cause difficulties during insertion, and there is a higher incidence of catheter dysfunction, particularly with nontunneled hemodialysis catheters (image 1). In a retrospective review of 532 catheters, left-sided internal jugular vein catheters also had higher rates of infection (0.50 versus 0.27) and dysfunction (0.25 versus 0.11) compared with those inserted from the right [47].

Common femoral vein hemodialysis catheter insertion may be needed, particularly in the setting of bilateral occlusion of the central thoracic veins [48,49]. Venous access at the common femoral vein avoids many of the complications associated with thoracic central venous access (eg, pneumothorax, air embolism). In a French trial of 750 intensive care unit patients requiring acute renal replacement therapy, there was no significant difference in infection rates between jugular and femoral access, but there was a higher rate of hematoma in the jugular group [50].

A longer catheter is needed when hemodialysis access is placed into the common femoral vein. A catheter length greater than 24 cm (tip to hub) is adequate for most average-sized adults to position the tip of the catheter in the inferior vena cava. Short hemodialysis catheters (less than 15 cm long) have higher recirculation rates when the tip of the catheter is positioned in the iliac vein [51].

The subclavian vein, although not a preferred site, can also be used for tunneled catheters if the jugular veins are occluded and the common femoral vein is not a good option. However, this site has a high incidence (15 to 50 percent) of subclavian vein stenosis and subclavian vein thrombosis, and in general, subclavian vein insertion sites should be avoided [52]. Subclavian stenosis/thrombosis also compromises the placement of permanent ipsilateral upper extremity arteriovenous (AV) hemodialysis access [53]. (See "Central vein obstruction associated with upper extremity hemodialysis access".)

In cases of complete occlusion or obliteration of femoral and central (neck/thoracic) veins, the femoral artery can be used if immediate access is required [1]. In cases where central venous obstruction prevents use of typical access sites, other AV access techniques (eg, sharp needle recanalization) can be used [54]. Advanced percutaneous approaches for catheter placement (eg, translumbar, transhepatic) are possible if no alternative form of AV access is possible [54-56]. Advanced surgical approaches used can place a catheter directly into the right atrium, superior vena cava, inferior vena cava, or azygos vein. More complicated approaches are associated with increased technical difficulty and morbidity.

Technique — After obtaining appropriate informed consent, hemodialysis catheters are inserted percutaneously using a modified Seldinger guidewire technique. Catheter placement using ultrasound guidance is recommended and is the accepted standard for internal jugular and femoral catheter placement. Technical success and reduced rates of access-related complications correlate with experience and the use of ultrasound guidance. Specific techniques to facilitate placement of central catheters at the jugular, femoral, and subclavian access sites are discussed in detail elsewhere. (See "Principles of ultrasound-guided venous access" and "Placement of jugular venous catheters" and "Placement of femoral venous catheters" and "Placement of subclavian venous catheters".)

Preventing infection related to hemodialysis catheters requires adherence to strict technique and optimal catheter management [18,57]. Measures to minimize hemodialysis catheter infection, including the use of antimicrobial agents at the exit site, antibiotic lock solutions, and eradicating nasal carriage, are discussed elsewhere. (See 'Maintenance in the dialysis unit and at home' below and "Overview of central venous access in adults", section on 'Site preparation' and "Overview of central venous access in adults", section on 'Sterile technique'.)

For tunneled catheters, the insertion technique varies depending upon the type of catheter. In general, tunneling the catheter follows venous puncture and guidewire placement. Because of the large diameter of hemodialysis catheters, a valved introducer peel-away sheath is needed to deliver the catheter into the vessel after dilation of the overlying soft tissues. The dilators and sheaths are stiff and should be imaged during their placement using fluoroscopy to ensure that the tip of the dilator is not taking an aberrant path, deforming the wire, or pushing through the vessel. This is particularly important in patients who have been hemodialysis dependent for an extended period and who may have central venous occlusive pathology as a result. Specific techniques for placing tunneled catheters are discussed in detail elsewhere. (See "Overview of central venous access in adults", section on 'Tunneled catheters'.)

Ultrasound guidance — Real-time ultrasound guidance is recommended for venous access during the placement of central venous catheters. Appropriate training is required to effectively use ultrasound devices. (See "Principles of ultrasound-guided venous access" and "Overview of central venous access in adults", section on 'Use of ultrasound'.)

Ultrasound is used to assess vein size and patency prior to venous puncture. In a study of 143 hemodialysis patients with a history of prior hemodialysis catheter placement, 25.9 percent had jugular vein thrombus and 62 percent of these occluded [58]. Ultrasound guidance during venipuncture minimizes the incidence of venous access-related complications, decreases procedure time, and increases the rate of initial technical success [59]. Ultrasound-guided venous access also decreases the likelihood of arterial puncture or pneumothorax in patients undergoing hemodialysis catheter placement [59-63]. In a meta-analysis, ultrasound guidance significantly decreased the risks of hemodialysis catheter placement failure (relative risk [RR] 0.12, 95% CI 0.04-0.37), failure to place catheter on first attempt (RR 0.40; 95% CI 0.29-0.56), arterial puncture (RR 0.22, 95% CI 0.06-0.81), and access site hematoma (RR 0.27, 95% CI 0.08-0.88) [64]. Another advantage of an ultrasound-guided technique in placing internal jugular hemodialysis catheters is that it allows the vein to be punctured more caudally (closer to the clavicle), which may reduce kinking; even a minimal degree of kinking can severely diminish flow rates.

Catheter positioning — Prior to the use of a central catheter for hemodialysis, the positioning of the tip of the catheter needs to be verified, typically using fluoroscopy or plain radiography. (See "Overview of central venous access in adults", section on 'Confirmation of catheter tip position'.)

Ideal positioning of hemodialysis access catheters is as follows:

●The tip of nontunneled jugular hemodialysis catheters should be positioned in the distal superior vena cava. Because of the stiffness of short-term access catheters and risk for complications, atrial placement should be avoided [10].

●When placed with the patient supine, the tip of tunneled hemodialysis catheters should be positioned within the right upper atrium. As the patient transitions to the upright position, the catheter will tend to retract 2 to 4 cm. Retraction of the catheter is greater for left-sided placement. If the catheter is placed too shallow, it may end up positioned in the superior vena cava or brachiocephalic vein (particularly in obese patients or large-breasted women), which can lead to a catheter malfunction [65]. In a retrospective review of 532 internal jugular hemodialysis catheters, left-sided catheters terminating in the superior vena cava or peri-cavoatrial junction had significantly more episodes of catheter dysfunction or infection compared with left-sided catheters terminating in the mid- to deep right atrium (0.84 versus 0.35), whereas no significant difference was identified for right-sided catheters based on tip position [47].

●The tip of femoral hemodialysis catheters (nontunneled or tunneled) should be placed in the inferior vena cava proximal to any stenotic lesions to minimize recirculation. Iliac vein positioning must be avoided. Since many nontunneled catheters are relatively short, placement of a tunneled catheter may be necessary to obtain appropriate length to enable adequate hemodialysis.

Catheter dressing — After catheter placement and after each use, the catheter should first be flushed with saline to evacuate any residual blood. Each lumen of the catheter is then filled with a lock solution. (See 'Maintenance in the dialysis unit and at home' below.)

The exit site of the catheter is redressed with a sterile bandage and antimicrobial ointment applied for at least the first two to three weeks following insertion. A variety of other agents have been used at the exit site to prevent infection. (See 'Exit-site antimicrobial agents' below.)

MAINTENANCE IN THE DIALYSIS UNIT AND AT HOME — The tunneled catheter insertion and exit sites will take approximately two to three weeks to heal. Most centers will recommend that, in addition to sutures used to secure the catheter initially when it was placed, the catheter is "anchored" to the skin with tape to keep it stable while the site is healing and to help ensure ingrowth into the polyester cuff of the catheter.

Initiating hemodialysis — To initiate hemodialysis using a hemodialysis catheter, the lock solution should first be aspirated from each port, and each lumen of the catheter should then be vigorously flushed with normal saline.

After disinfecting with chlorhexidine or a similar agent, the catheter hubs should then be immediately connected to the dialysis machine to avoid prolonged exposure to air. The connectors are covered with a sterile gauze.

Catheter flushing and locking after dialysis — At the end of the dialysis treatment, the staff disconnects the catheters from the dialysis machine, injects 10 mL of saline into each lumen, and then fills the lumen with a lock solution. Proper flushing and the instillation of a locking solution may decrease, but does not eliminate, the risk of hemodialysis catheter thrombosis [66-69]. The usual rinse with saline at the end of dialysis is important to clear blood from the blood lines and dialyzer, but it is not very efficient in completely clearing all blood from the catheter or dislodging any small thrombi that might be present. Thus, there is consensus that a "flush" of the catheter with normal saline is mandatory after it has been rinsed. The "flush" is the manual injection of normal saline for the purpose of cleaning the inner lumen of the catheter to maintain patency. A handheld 10 mL syringe is recommended to prevent pressure damage to the catheter. A push and pause method is used to create turbulence inside the catheter. Following the catheter flush, the "lock" is the intraluminal injection of a limited volume of fluid for the purpose of preventing lumen occlusion and/or bacterial colonization. The optimal "lock" solution is still controversial.

The 2019 National Kidney Foundation Kidney Disease Outcomes Quality Initiative (KDOQI) Clinical Practice Guideline for Vascular Access Update reviewed the use of intraluminal agents to prevent central venous catheter thrombosis. KDOQI considers it reasonable that the choice to use citrate or heparin as a central venous catheter locking solution should be based on the clinician discretion and best clinical judgment. KDOQI stipulates that there is inconclusive evidence to demonstrate a difference in catheter survival or complication rates between these locking solutions [1]. (See 'Prophylactic antimicrobial catheter locking solutions and caps' below and 'Prophylactic antithrombotic catheter locking' below.)

Prior to flushing the catheter, the clinician needs to determine:

●The type and concentration of locking solution (eg, heparin, citrate, normal saline, tissue plasminogen activator [tPA], hypertonic saline, and taurolidine) to be used (see 'Prophylactic antimicrobial catheter locking solutions and caps' below and 'Prophylactic antithrombotic catheter locking' below)

●The volume of locking solution (see 'Catheter locking volume and instillation' below)

Once the type, concentration, and appropriate volume of locking solution have been determined, the lock solution is administered in a stepwise fashion (eg, draw up solution, disconnect hemodialysis lines, flush ports with saline, followed by instillation of the locking agent), using protocols established within the particular dialysis unit.

There is no consensus on the best agent for catheter locking (normal saline, antimicrobial, antithrombotic) [70-74]. Data supporting the best technique, agent, volumes, and regimens are lacking. Clinical studies with a strong methodological design and a focus on flushing and locking in relation to catheter malfunction are needed; in these, uniform malfunction definitions, terminology, and measurements should be used. Some antimicrobial agents have also demonstrated reductions in catheter-related thrombosis. (See 'Prophylactic antimicrobial catheter locking solutions and caps' below.)

Prophylactic antithrombotic catheter locking — Lumen occlusion is a serious concern in a central venous catheter. The process of catheter occlusion and dysfunction is complex; it is not simply based on blood clotting but more likely due to interaction of blood with bacteria-derived biofilm and bacterial debris. To prevent catheter dysfunction, a wide variety of solutions are used to fill or "lock" tunneled hemodialysis catheters. These include saline (normal, hypertonic), heparin (most widely used, but in varying concentrations [100 to 5000 units/mL]), as well as alternative agents such as citrate, tPA [75], and sodium bicarbonate [76]. Among the agents used as alternatives to normal saline or heparin, citrate has been the most studied [77]. In the United States, the locking regimens of outpatient dialysis providers differ; most use 1000 units/mL heparin as its standard, while another frequently uses a heterogenous variety of heparin concentrations or normal saline.

A systematic review identified 27 trials [66,78-100] assessing alternative anticoagulant locking solutions or systemic agents for the prevention of catheter malfunction (defined as a catheter blood flow of ≤200 mL/minute, or as defined by the study authors) or for the occurrence of bacteremia [77]. In a meta-analysis of 16 of these, the incidence of catheter malfunction was not significantly different for alternative anticoagulant locking solutions, systemic agents, or low- or no-dose heparin compared with conventional care, which predominantly consisted of instilling a heparin solution into each catheter port.

A later prospective cohort study compared sodium bicarbonate to normal saline as a lock solution with the underlying premise that sodium bicarbonate has both antimicrobial and antithrombotic properties [76]. The results were encouraging, with reduced rates of catheter loss due to thrombus and bacteremia in the sodium bicarbonate group.

Heparin — Heparin remains the traditional and most-used lock solution to minimize catheter dysfunction. This is primarily related to its ease of use, availability, and relatively low cost. When using heparin lock, there are several pharmacological and clinical issues to be considered. Heparin by itself is not thrombolytic and does not lyse intraluminal clot, rather it merely prevents further clot formation. While heparin lock has been used for decades with relative safety, it has other undesired effects such as drug hypersensitivity, drug incompatibilities, and potential for heparin-induced thrombocytopenia (HIT). HIT can occur even with low-dose heparin (eg, 100 units/mL). The incidence is 0.2 to 0.76 percent in all heparin-exposed patients [77,101]. In the hemodialysis population, the reported incidence is significantly higher (3.9 to 17.9 percent of patients) [102]. The potential side effects of heparin from repeated exposure, including HIT, may be avoided by using normal saline or sodium citrate as a lock solution. (See "Clinical presentation and diagnosis of heparin-induced thrombocytopenia".)

When heparin is selected as the lock solution, there are no studies defining the best concentration to use. The American Society of Diagnostic and Interventional Nephrology position paper recommends a heparin lock concentration of 1000 units/mL [69]. A lower heparin concentration (100 units/mL) is effective for preventing catheter thrombosis and costs less [103]. In past practice, more concentrated heparin was used but was associated with inadvertent systemic anticoagulation and clinical episodes of bleeding, due to leaching of the anticoagulant into the patient, particularly if the catheter lumen was overfilled [69,104,105]. With high heparin concentrations, overfilling the catheter lumen by as little as 0.1 cc could result in a heparin bolus of 500 to 1000 units; thus, high concentrations of heparin have largely been abandoned. (See 'Catheter locking volume and instillation' below.)

Insufficient aspiration of heparin locked into the catheter, inaccuracy of the internal volume indicated on the catheter, human error, and leaching (ie, diffusion of the solution out of the catheter) of heparin into the patient during the intradialytic period have also been noted as possible reasons for hemorrhagic complications after heparin locking of a hemodialysis catheter [106].

Citrate — Citrate avoids heparin-associated bleeding complications, improves reliability of international normalized ratio (INR) assays, provides an effective alternative for patients with suspected or confirmed heparin-induced thrombocytopenia, and is economical. Citrate also has the advantage of having antimicrobial activity when used in a sufficient concentration [107-109]. Catheter locking solutions can inhibit or promote biofilm formation, which can contribute to the development of bacteremia. Heparin promotes biofilm, while citrate inhibits its development at levels above 0.5%. Below this concentration, citrate also stimulates biofilm formation [110].

The safety of the use of higher concentrations came into question, prompting removal from the market. The main concern regarding the use of these high concentrations of citrate (30% and 47%) is that, if it is inadvertently injected or leaked out of the catheter, it can cause serious hypocalcemia, cardiac dysrhythmias, and death [111]. As such, 4% citrate has primarily been used, and guidelines have found some evidence to support its use to prevent catheter-related bloodstream infections [1,82].

rt-PA — Randomized trials suggest that the instillation of alteplase (rt-PA), rather than heparin, may improve catheter blood flow and decrease the incidence of catheter clotting [96,97,112-115]. In one of these studies, 225 patients were randomly assigned to a catheter locking regimen of rt-PA or heparin [97]. Significantly lower rates of catheter malfunction (20 versus 35 percent) and catheter-related bacteremia (4.5 versus 13 percent) were seen in those who received rt-PA. In a crossover trial of 12 patients, the administration of rt-PA (2 mg injected into each lumen) was associated with significantly higher blood flow rates and better arterial and venous pressures compared with heparin [113]. No episodes of catheter thrombosis occurred with rt-PA, compared with 20 percent of the patients using heparin. In part due to these findings, guidelines suggest that rt-PA be used prophylactically once per week [1]. However, rt-PA is expensive, may not be routinely stocked, and, when used, may not be reimbursed as a separate treatment.

Catheter locking volume and instillation — At the completion of the dialysis session, each lumen of the catheter is filled with the exact amount specified by the manufacturer on the port. Overfilling must be avoided. Catheter manufacturers specify the fill volume for each catheter lumen [116]. The instillation volumes are the same in each lumen of a symmetric tip catheter. For step-tip and split-type catheters, the venous volume is generally 0.1 to 0.2 cc greater than the arterial volume. Typical volumes are 1.2 to 1.8 mL for short nontunneled catheters and 1.9 to 3.1 mL for larger tunneled catheters.

It is commonly assumed that injection of this precise filling volume is safe and efficient. However, it has been shown that this may not be the case. Locking solution leaching begins immediately after instillation of the solution and continues over a 30-minute period, especially in nontunneled catheters. The excess leakage volume has been measured to be up to 1.43 mL [117,118]. When higher concentrations of heparin were used, increases in the activated partial thromboplastin time (aPTT) were seen, even at the lock volume specified by the manufacturer [119,120].

In a study designed to compare leakage for different brands of double-lumen dialysis catheters, five different double-lumen dialysis catheters were tested using three different lock volumes: the stated lock volume and both 20 percent over and under that volume [121]. All of the catheters tested were conically shaped and had side holes. All had a substantial amount of leakage. When the catheter's stated lock volume was used, all catheters leaked volumes that ranged from 18 to 30 percent of the injected volume, depending upon the size and manufacturer of the catheter. The leak ratio increased significantly, with 20 percent overfill. There was some leakage even when using 20 percent less than the lock volume.

Earlier in vitro work using a long-term tunneled catheter without side holes showed that instillation of the catheter filling volume results in an overspill of 17 to 20 percent [122].

The phenomenon that results in this anomaly of leakage is shear stress as it relates to laminar flow in the catheter lumen. The stated fill volume for a catheter is measured under static conditions and incorrectly assumes that the advancing wave of introduced fluid moves as a vertical wall. Instead, the dynamics of shear stress dictate that there is a significant difference in velocity between the center of the column of advancing fluid and the boundary layer in contact with the wall where it is zero. Thus, the introduced fluid (heparin in this instance) moves down the catheter with a hyperbolic advancing edge. This results in leakage, although less than the amount of the lock volume.

In addition, the locking solution may spill into the blood stream under the influence of gravity [122]. As a result of the fluid dynamics that are occurring, the concentration of the locking solution at the catheter tip is much reduced. This is affected appreciably by the catheter's side holes. Much of the locking solution beyond the most proximal side hole is lost. It has been estimated that the mean concentration at the catheter tip is reduced to approximately 90 percent. It appears that slow administration of the locking solution has negligible influence upon the dynamics of the loss [123]. However, in vitro experimental studies have shown that a small air bubble trapped in the Luer connection during connection reduces the spillage volume to 10 to 15 percent [124].

Insufficient aspiration of heparin locked into the catheter, inaccuracy of the internal volume indicated on the catheter, human error, and "leaching" of heparin into the patient during the intradialytic period have also been noted as possible reasons for hemorrhagic complications after heparin locking of a dialysis catheter [106].

No role for routine systemic anticoagulation — The available data from randomized trials and observational studies do not support routine systemic antithrombotic prophylaxis for hemodialysis catheters to prevent catheter dysfunction, due to increased risks of harm and unclear benefit with respect to patency [1,77,125,126]. The 2019 KDOQI Clinical Practice Guideline for Vascular Access: 2019 Update recommends against the use of systemic anticoagulants for the sole purpose of maintaining central venous catheter patency [1].

A systematic review that included five trials evaluating the effects of warfarin anticoagulation on catheter dysfunction found no overall benefit compared with placebo [77,83,90,127-129]. Individually, no benefit was seen for the two studies that used low-dose warfarin (1 mg/day) [90,127]. The remaining three studies used differing therapeutic targets with studies using an INR of 1.5 to 1.9 [129], 1.5 to 2.0 [128], and 1.8 to 2.5 [83]. For the study for which prophylactic warfarin dosing was adjusted to the highest INR, the risk for hemodialysis catheter thrombosis was significantly reduced (relative risk [RR] 0.23, 95% CI 0.13-0.44) [83].

Measures to prevent infection — Efforts to minimize the incidence of infection associated with hemodialysis catheters involve first and foremost avoiding catheter usage whenever not specifically indicated, preferentially using an arteriovenous access for hemodialysis. For patients who require a central catheter, strict adherence to sterile technique when handling the catheter is the main measure to prevent infection. While we do not routinely use antimicrobial locking agents or antimicrobial-coated catheters, selected patients may benefit from these practices [130]. (See 'Surface-coated catheters' above and 'Exit-site antimicrobial agents' below.)

Dressing changes — Initial dressing site management is discussed above. Subsequently, hemodialysis catheters should be handled according to a protocol describing proper techniques for handling or manipulating vascular access catheters. All personnel should be adequately trained in these techniques and about the importance of routine hand hygiene before and after patient contact. (See 'Catheter dressing' above.)

At the end of the dialysis session, both the staff and patient should wear masks and use proper hand hygiene. The individual who removes the bandage should then don nonsterile gloves. Any dressing covering the catheter site is removed and properly disposed of. The nonsterile gloves should then be removed, and performance of hand hygiene repeated. Then, using sterile gloves, the catheter, connectors and exit site should be inspected and disinfected with a chlorhexidine solution. The skin should be allowed to dry. The exit site of the catheter is redressed using a sterile bandage and antimicrobial ointment for at least the first two to three weeks following insertion. Most facilities continue this practice until the catheter is removed, but some abandon the dressing once the polyester cuff of the catheter is well incorporated with the subcutaneous tissue [131].

Nurses or technicians should routinely use hand hygiene and wear nonsterile gloves and a mask when hemodialysis catheters are accessed. The patient should also wear a mask during hookup and disconnection of the catheter and the hemodialysis tubing. Hand hygiene is necessary before gloves are donned, as glove contamination may occur. Moreover, hand hygiene must also follow removal of gloves, as hand contamination routinely occurs when contaminated gloves are removed. In addition, we monitor rates of hemodialysis-associated infections to detect and understand local trends in types of pathogens, incidence, and antimicrobial resistance in a manner similar to that described by others [132].

Exit-site antimicrobial agents — The use of exit-site antimicrobial agents, such as topical povidone-iodine, Polysporin, mupirocin, and/or other agents, was initially thought to be a good strategy to help prevent hemodialysis catheter-induced bacteremia [30,133-138]. Topical antibiotic use appeared to decrease the rate of bacteremia significantly. This was best shown in a meta-analysis, which found that topical antibiotics compared with no antibiotic therapy lowered the rates of bacteremia (RR 0.22, 95% CI 0.12-0.40), exit-site infection (RR 0.17, 95% CI 0.08-0.38), requirement for catheter removal, and hospitalization for infection [136].

However, two significant problems evolved with this approach:

●A substantial percentage of health care-associated staphylococcal infections are now due to community-acquired strains of methicillin-resistant Staphylococcus aureus (MRSA), in which nasal colonization is uncommon. (See "Methicillin-resistant Staphylococcus aureus (MRSA) in adults: Epidemiology".)

●The emergence of either low- or high-level resistance to topical or intraluminal antimicrobial agents is a definite and predictable risk of such therapies. Emergence of resistance to mupirocin, for example, is an increasing problem in the United States [139,140]. Data suggest that widespread use of mupirocin in Canada is associated with the emergence of a plasmid-encoded gene (mupA) that resulted in high-level resistance to this agent [141]. One study, in which topical mupirocin was used routinely to prevent S. aureus exit-site infections in patients on chronic peritoneal dialysis, reported that 15 percent of S. aureus isolates became resistant to mupirocin at the end of the four-year study period (these isolates were identified in 3 percent of all patients) [142].

Despite these risks, the use of povidone-iodine antiseptic ointment or triple antibiotic (bacitracin/gramicidin/polymyxin B) ointment at the exit site after catheter insertion and at the end of each hemodialysis session is recommended by a joint working group led by the Society of Critical Care Medicine and the Infectious Diseases Society of America, provided the ointment does not adversely interact with the catheter material according to manufacturer recommendations [143]. The adoption of these and other Centers for Disease Control and Prevention recommendations for catheter care resulted in a 20 percent reduction in bloodstream infections and antibiotic starts associated with a decrease in sepsis-related hospitalization in one quality-improvement initiative [144]. Gramicidin-containing ointment is not available in the United States.

Prophylactic antimicrobial catheter locking solutions and caps — We agree with guidelines that suggest not routinely using antimicrobial lock solutions in all patients for the purpose of preventing catheter-associated bacteremia [1]. We agree with the suggestion that selective (limited) use of antimicrobial and antibiotic lock solutions can be considered in select patients in need of long-term tunneled catheters who are at high risk for recurrent catheter-related bloodstream infections and in facilities with high rates of infection (>3.5/1000 days) [145].

The goal for using antimicrobial lock solutions is to prevent bacterial colonization, biofilm formation, and catheter dysfunction. The ideal antimicrobial lock solution would have a broad spectrum of activity to prevent catheter-related bloodstream infection while preventing selective resistant organisms. It would also prevent catheter thrombosis and dysfunction.

While beneficial outcomes have been reported, most studies are of short duration and do not address the issue of antibiotic resistance [146]. In later studies of longer duration and using lower doses of antibiotics and antimicrobials, some data have shown efficacy and minimal or no bacterial resistance [145,147].

Various antimicrobial agents, alone and in combination, have been evaluated to target the intraluminal route of organism entry that causes catheter-related bloodstream infections [30,84,91,93,108,145,147-155]. These have included hypertonic sodium citrate, hypertonic saline, ethanol (30 to 100 percent), methylene blue, ethylene diamine tetra-acetic acid (EDTA), antibiotics like gentamicin alone or with other agents (cefazolin or vancomycin), cotrimoxazole (TMP-SMX), and minocycline, as well as a novel antimicrobial cap. Some antithrombotic agents have also demonstrated reductions in catheter-related bacteremia. (See 'Prophylactic antithrombotic catheter locking' above.)

●In a 2009 systematic review that included 29 trials involving 2886 patients and 3005 catheters, antimicrobial lock solutions were associated with decreased risk of catheter-related bacteremia (RR 0.33, 95% CI 0.24-0.45) [30]. A later meta-analysis that included 13 trials and 1770 patients concluded that citrate-containing lock solutions were not superior to heparin alone [156]. However, when the analysis was expanded to include citrate plus one of a variety of antimicrobial agents, there was a significant benefit for the inclusion of citrate in the lock solution. However, citrate and many of the antimicrobial agents included in these studies are not available in the United States. A review that included 1350 hemodialysis catheters showed that use of a gentamicin-heparin lock was associated with a significantly reduced risk of all-cause mortality compared with standard heparin locks (hazard ratio 0.36, 95% CI 0.22-0.58), as well as a significantly decreased rate of gentamicin-resistant organisms (0.40 versus 0.22/1000 person-years) [157].

●In a systematic review assessing alternative anticoagulant locking solutions compared with conventional care (typically heparin) for the prevention of hemodialysis catheter complications, the risk for catheter-related bacteremia was significantly reduced overall for alternative anticoagulant locking solutions (RR 0.46, 95% CI 0.32-0.66), but not for systemic agents (RR 2.41, 95% CI 0.89-6.55) [77,158]. In subgroup analysis, this result was predominantly due to the effect of using antibiotics (RR 0.27, 95% CI 0.11-0.70) [81] or recombinant tissue plasminogen (RR 0.35, 95% CI 0.13-0.93) [96].

●Two large, multicenter randomized studies have shown a benefit of a novel antibacterial barrier cap device that contains a rod coated with chlorhexidine versus standard best-use practices/policies for central venous catheters [159,160]. The two studies were carried out in multiple dialysis units at the two largest dialysis providers in the United States. In both studies, there was a significant decrease in the rate of catheter-related bloodstream infections and hospitalizations for the barrier cap device. There was no reported improvement in other complications or dysfunctions such as thrombosis rates.

Despite these findings, a number of issues remain concerning antimicrobials for prevention of catheter-related infections [161]:

●Prolonged use of any antimicrobial agent (eg, greater than 6 to 12 months) is likely to result in the development of antibiotic-resistant organisms [155]. In one observational study in which gentamicin was routinely instilled at the end of dialysis, although the total catheter-related infection rate decreased, gentamicin-resistant infections increased, beginning six months after initiation of the protocol, resulting in four deaths, two cases of septic shock, and four cases of endocarditis [146].

In two other longer-term studies, both of which used a lower concentration of gentamicin antimicrobial lock (AML; 0.32 mg/mL) with 4% citrate, no gentamicin resistance was observed. The first was a randomized trial of 303 patients with a seven-year follow-up period [91]. The second was a prospective observational cohort study comparing different time periods (heparin lock versus gentamicin/citrate AML) in 555 patients [157]. Low-dose gentamicin-citrate AML was associated with significant reduction in catheter-related bloodstream infection. A significant decline in gentamicin resistance (from 0.40 to 0.22/1000 person-years) in the antibiotic lock group over a two-year period.

●Systemic toxicity may result from leakage of these solutions. In particular, gentamicin locks have been associated with ototoxicity in 10 percent of patients in one study [84]. Concentrated citrate locks can potentially cause life-threatening hypocalcemia and intolerable side effects (such as metallic taste or facial or digital paresthesias) [95]. High concentrations of ethanol (>70 percent) have been reported to be associated with headache, nausea, dizziness, fatigue, hepatotoxicity, and structural changes in the catheter [85].

●In the United States, reimbursement schemes do not provide payment for these agents, thereby placing a financial burden on dialysis units. In addition, many of these combinations are available in Europe, but such agents (citrate 7%/methylene blue/methylparabens/propylparaben) are not yet approved by the Food and Drug Administration for this indication.

Problems associated with the development of antibiotic-resistant organisms may be addressed in part by using antibiotics that are not commonly used to treat serious infections. As an example, one randomized, open-label trial that included 204 incident tunneled and nontunneled catheters demonstrated a reduction in overall catheter-related bacteremia associated with the use of a lock solution that contained minocycline and EDTA compared with heparin (4.3 versus 1.1 per 1000 catheter-days) [81]. However, among 52 tunneled catheters that were included in the trial, fewer episodes of bacteremia occurred in catheters instilled with minocycline-EDTA compared with heparin (1.8 versus 4.8 per 1000 catheter-days, respectively), although this difference was not significant.

PREVENTION OF COMPLICATIONS — The best prophylaxis against complications remains avoidance of using central venous catheters for hemodialysis unless necessary. When hemodialysis catheter placement is necessary, the use of ultrasound guidance can prevent complications related to central venous access. (See "Overview of complications of central venous catheters and their prevention in adults", section on 'Preventing complications'.)

Once the catheter is placed, there should be a plan to remove the catheter as soon as is feasible. Meticulous hygiene, education, and infection control measures by the staff as well as educating the patient on proper catheter care are mandatory to minimize the complications from central venous catheters.

The role of the various interventions for preventing complications, including catheter locking, prophylactic antithrombotic locking agents, prophylactic antimicrobial locking agents, and systemic anticoagulation, is discussed above. (See 'Prophylactic antithrombotic catheter locking' above and 'Prophylactic antimicrobial catheter locking solutions and caps' above and 'No role for routine systemic anticoagulation' above.)

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Venous access" and "Society guideline links: Dialysis" and "Society guideline links: Hemodialysis vascular access".)

INFORMATION FOR PATIENTS — UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." The Basics patient education pieces are written in plain language, at the 5^th to 6^th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10^th to 12^th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.

Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient info" and the keyword(s) of interest.)

●Beyond the Basics topics (see "Patient education: Dialysis or kidney transplantation — which is right for me? (Beyond the Basics)" and "Patient education: Hemodialysis (Beyond the Basics)")

SUMMARY AND RECOMMENDATIONS

●There are two main types of hemodialysis catheters: nontunneled and tunneled. Nontunneled catheters are shorter in length and are relatively stiff, which facilitates insertion. Tunneled hemodialysis catheters are made of soft polymer and have a cuff to promote tissue ingrowth, which minimizes the risk of catheter infection by limiting migration of bacteria along the catheter from the exit site. Blood flow rates are higher during dialysis for tunneled, compared with nontunneled, catheters because of their larger luminal diameter. (See 'Nontunneled catheters' above and 'Tunneled catheters' above.)

●Nontunneled hemodialysis catheters are preferred for acute (immediate or emergency) hemodialysis vascular access in the hospital setting. Nontunneled hemodialysis catheters should not be used for chronic, long-term, or outpatient hemodialysis. Due to the increased risk of infection over time, the duration of use for nontunneled catheters is limited to less than two weeks for internal jugular catheters. For femoral catheters, the duration of use is generally limited to a single treatment in ambulatory patients, but in bed-bound hospitalized patients, the catheter may remain in place for up to two weeks. If the catheter is expected to be in use for more than two weeks, a tunneled hemodialysis catheter is preferable to a nontunneled catheter, even in the intensive care unit setting. (See 'Duration of use' above and 'Catheter life' above.)

●Although arteriovenous (AV) access is preferred for chronic hemodialysis, in some situations, such as in those with multiple failed AV access with no available options or limited life expectancy, using a tunneled hemodialysis catheter long-term is justified. (See 'Basic principles' above and "Approach to the adult patient needing vascular access for chronic hemodialysis", section on 'Catheter appropriateness'.)

●Hemodialysis catheters are inserted using a modified Seldinger guidewire technique, typically into the jugular or femoral vein. We avoid placement of hemodialysis catheters in the subclavian vein, unless no other option is available. Subclavian vein access is associated with a high incidence of subclavian vein stenosis and thrombosis, which impairs the function of the catheter and compromises subsequent permanent hemodialysis AV dialysis access. (See 'Access site considerations' above and "Central vein obstruction associated with upper extremity hemodialysis access".)

●Proper use and maintenance of hemodialysis catheters help prevent complications. These include adherence to sterile technique when connecting and disconnecting from the dialysis machine and adherence to flushing, locking, and access site dressing protocols. (See 'Maintenance in the dialysis unit and at home' above.)

ACKNOWLEDGMENTS — The editorial staff at UpToDate acknowledges Steve J Schwab, MD, Karen Woo, MD, and Steven J Bander, MD, who contributed to an earlier version of this topic review.