Naomi P. O'Grady
Procedures, Vascular Access and Conscious Sedation Service, National Institutes of Health, Bethesda, Maryland
Treatment for patients with cancer frequently requires the placement of a vascular access device (VAD) for administering chemotherapy, total parenteral nutrition, analgesics, or antibiotics, or for frequent blood sampling. In some cases, vascular access may require only a peripheral intravenous (i.v.) catheter (i.e., the tip of the catheter remains within the peripheral circulation). Increasingly, however, there is a need for access to the central venous circulation with a central VAD [i.e., the tip of the catheter is positioned in a large central vessel such as the superior vena cava (SVC)]. A VAD that is inserted into a peripheral vein but that is long enough for its tip to be positioned in a central vessel is termed a peripherally inserted central venous catheter (PICC). Indications for a central VAD are shown in Table 45.1.
TABLE 45.1. Indications for Central Venous Access Devices
Several different types of central VADs are available for use in patients with cancer (1,2,3,4,5,6). Individual circumstances will determine the type of VAD that is best for a particular patient. Placing and maintaining any central VAD is more complex, however, than is the case with a simple peripheral i.v. catheter. It is very important to recognize and minimize the potential for mechanical complications and infections associated with the use of central VADs.
CLASSIFICATION AND APPLICATION OF DIFFERENT CENTRAL VASCULAR ACCESS DEVICES
The classification of central VADs is based, in large part, on the following parameters: the characteristics of each catheter's composition (e.g., polyurethane or silicone), its location (i.e., central or peripheral), and the method of insertion (i.e., percutaneous, tunneled, or implanted). These parameters are associated with both advantages and disadvantages, which are outlined in Table 45.2. A percutaneous catheter is inserted directly through the skin into the vessel. In tunneled placement, a part of a catheter is placed in the subcutaneous tissue between the sites of insertion at the skin (usually midway between the nipple and sternum on the anterior chest) and the vein (subclavian or internal jugular). A Dacron cuff positioned several
inches above the exit site promotes fibrous ingrowth, better securing the tunneled catheter and possibly decreasing bacterial colonization of the catheter below the cuff. Implanted VADs have a stainless steel, titanium, or plastic port at their proximal end, which includes a Silastic self-sealing septum. Once the catheter is inserted, the port is placed in a subcutaneous pocket that is sutured. The Silastic septum of the port can be accessed by a needle introduced through the skin and septum, into the port chamber itself. This is frequently done with a Huber needle, which has been designed with a side hole to minimize damage (coring) to the Silastic septum. Port housings are designed to provide minimal distortion artifact on magnetic resonance imaging (MRI) or computerized tomography (CT) scans.
TABLE 45.2. Advantages and Disadvantages of Different Catheter Compositions, Locations, and Methods of Insertion
The parameters outlined in Table 45.2 determine, in large part, the applicability of a particular type of catheter for a particular patient. Polyurethane percutaneous catheters, although relatively easy to place at either central or peripheral sites, are generally not suitable for long-term use, given the greater risk of infection and vascular trauma associated with their use. Tunneled and implanted Silastic catheters, however, although more difficult to place, may be associated with lower risk of infection and vascular injury and can be used over longer periods. The ease of care and limited restrictions associated with implanted catheters make their use most desirable in patients who will require frequent catheter use over prolonged periods. The optimal duration of use for percutaneous or Silastic catheters located centrally or peripherally has not been adequately defined. With care and prompt removal when clinically indicated, these catheters may be maintained in some patients for several months.
Other characteristics of central VADs may make one type of catheter more applicable for an individual patient than another. For example, catheters located centrally are usually larger
in gauge (4 to 12 Fr) than those placed peripherally (2 to 6 Fr) and permit higher flow rates and easier drawing of blood. Larger-gauge catheters can also be constructed with more lumens. Although most central VADs are open at the end or tip, the Groshong catheter (Bard Access Systems) has a closed end with a three-way slit valve to reduce the potential backflow of blood into the catheter. Figure 45.1 shows an algorithm for determining the type of catheter most appropriate for a particular patient. Table 45.3 shows examples of the different catheter types frequently used at the National Institutes of Health (NIH) Warren G. Magnuson Clinical Center.
TABLE 45.3. Examples of Frequently Inserted Vascular Access Devices at the National Institutes of Health Warren G. Magnuson Clinical Center
FIG. 45.1. Algorithm for determining the appropriate type of catheter.
COMPLICATIONS WITH INSERTION
Insertion of any central VAD, whether at the bedside, in radiology, or in surgery, is associated with the risk of mechanical complications or infection (1,2,3,5,6). Mechanical complications most commonly arise when catheter placement results in injury to central vascular structures (e.g., venous or arterial perforation) or to the lungs (e.g., pneumo-, hemo-, or hydrothorax). The occurrence of these types of complications or their sequelae can be reduced by ensuring: first, that abnormalities of anatomy related to previous therapy (e.g., surgery, radiation, or earlier VADs) or disease (e.g., tumor) are recognized before VAD placement; second, that the patient's coagulation profile has been optimized (i.e., platelet count brought to >50,000 per mL and prothrombin and partial thromboplastin times corrected); and third, that careful attention is given to identification of complications that may become apparent only several hours after VAD placement (e.g., pneumo-, hemo-, or hydrothorax). In some patients, in whom complete correction of the coagulation profile is not possible, VAD placement may still be done while
the appropriate replacement products are infused through an additional catheter. Because of the difficulties associated with compressing subclavian vascular structures, percutaneous or tunneled catheter insertions should generally not be performed at this site unless an adequate coagulation profile can be achieved. Complications arising from infection from insertion can be reduced by ensuring that the operators use a strict sterile technique and full barrier precautions.
CARE AND MAINTENANCE
Once the central VADs have been inserted, their care and maintenance include regular flushing with a saline and heparin solution and changing of dressings (i.e., gauze or transparent) and catheter injection caps. No clear standard has been established with respect to the volume, dose, and frequency of heparin flushing; the type and frequency of dressing changes; or the frequency of cap changes. However, general guidelines do exist, and successful maintenance of a central VAD is the result of an established care routine (7,8,9). Most central VADs are flushed daily with a quantity of saline (5 to 10 mL) and heparin (1 to 5 mL of a 10 to 1,000 U per mL) solution equivalent to two times the volume of the catheter and any additional infusion devices in series with the catheter. Implanted VADs are flushed monthly with saline and heparin when not accessed. Groshong catheters are flushed weekly, or after each use, with saline only. Gauze and transparent dressings are changed every 2 days and 7 days, respectively. Catheter caps are changed after wiping with cleansing solution at least every 7 days, or whenever they are damaged or contain residual blood. A 2% chlorhexidine-based preparation is recommended for catheter site care. Alternatively, if the patient cannot tolerate chlorhexidine, povidone–iodine (10%), alcohol (70% to 92%) solutions, and hydrogen peroxide can be used.
Whenever a central VAD is accessed, precautions must be taken to prevent the entry of air into the catheter and thereby into the circulation (i.e., air embolus). The central VAD should be clamped between the point of access and the patient. If a catheter does have to remain open for short periods, such as during initial wire removal at insertion, the patient should be in the Trendelenburg position.
COMPLICATIONS AFTER INSERTION
Maintaining a central VAD for any period is associated with the risk of infection, thrombotic or nonthrombotic catheter obstruction, vascular injury, or failure of the VAD itself. These complications may occur at any time.
The reported incidence of infection relating to central VADs ranges from 3% to 60% but is usually less than 10% (1,2,3,4,5,9,10,11,12). This incidence may be higher in patients with cancer who have neutropenia related to therapy or disease. Infections with central VADs can occur locally (i.e., exit site or tunnel or pocket infections) or systemically [i.e., catheter-related bloodstream infections (CR-BSIs)]. Definitions developed by the Centers for Disease Control and Prevention (CDC) are shown in Table 45.4 (9). Different types of infections with VADs will be managed differently (1,3,4,5,6,10,11,12,13). Exit-site infections, most frequently related to Staphylococcus epidermidis, can be treated initially with local wound care and oral antibiotics without removing the catheter. However, exit-site infections resulting in bacteremia may require catheter removal, especially in cases of infections with Staphylococcus aureus. Tunnel or pocket infections are most frequently related to S. epidermidis or S. aureus and almost always require systemic antibiotic treatment and catheter removal, with surgical drainage of the infected site. A definitive diagnosis of CR-BSI, although not always possible,
requires that the same pathogen be cultured in the blood drawn from both the central VAD and another site. Documented or suspected CR-BSI should always be treated with systemic antibiotics. These infections, most frequently related to S. epidermidis and S. aureus, may also be caused by either the gram-negative bacteria or fungal species to which immunosuppressed patients with cancer are susceptible. The initiation of empiric antibiotic coverage in such patients must take these other organisms into account. CR-BSI can sometimes be treated with systemic antibiotics alone, but evidence of worsening infection or the presence of S. aureus or candidal infection calls for prompt removal of the catheter. Some central VADs are impregnated with antimicrobial agents [chlorhexidine and silver sulfadiazine (Arrowguard Blue; Arrow International) or minocycline and rifampin (Cook Spectrum; Cook Critical Care)] or have an attached antimicrobial cuff [silver ion (Vita Cuff; Vitaphore)]. The overall effectiveness of such agents in preventing infection over the lifetime of a central VAD continues to be studied (13,14,15,16,17,18). At present, data support the use of antiseptic-impregnated catheters. The effectiveness of antimicrobial cuffs is not yet clear.
TABLE 45.4. Centers for Disease Control and Prevention (CDC) Clinical and Surveillance Definitions for Catheter-related Infections
Obstruction of a VAD can be related to thrombotic or nonthrombotic causes (10,19,20,21,22). Thrombotic obstructions can be classified as those present within (intraluminal) or around the outside of (fibrin sheath) the catheter itself and those in association with the vessel wall (mural thrombus). A catheter may sometimes become encased in a mural thrombus. Nonthrombotic obstruction of a central VAD can be a result of malpositioning of a catheter tip against a vessel wall, catheter kinking, luminal occlusion caused by drug precipitation, or fracture of the catheter. These types of obstruction may require either repositioning or removal of the catheter. When diagnosing the cause of an obstruction, it is helpful to first determine whether the obstruction interferes with withdrawal or with infusion or both. An algorithm to aid in the diagnosis and treatment of catheter obstruction is shown in Fig. 45.2.
FIG. 45.2. Algorithm to aid in the diagnosis and treatment of catheter obstruction.
†Jugular vein distention, evidence of collateral circulation, unilateral arm swelling.
‡Chemical occlusion therapy:
•Alcohol for lipid precipitates
•0.1 Hydrochloric acid for nonlipid precipitates.
Vascular injury resulting in actual perforation of a vessel wall is not commonly found with the flexible central VADs now in use. Nevertheless, catheter tips should not be positioned perpendicular to an adjacent vessel, such as in the innominate vein at its junction with the SVC. Because of the smaller diameters of the basilic and cephalic veins, mechanical phlebitis can sometimes occur after PICC insertion. This usually manifests itself within 1 to 7 days of insertion with erythema, tenderness, induration, and a palpable venous cord along the vessel tract. Treatment is with moist heat, arm elevation, mild range-of-motion exercises, and an antiinflammatory agent. Mechanical phlebitis should respond to treatment within 24 to 48 hours. If such a response is not noted, the catheter should be removed, local treatment should be continued, and consideration should be given to a course of antibiotic therapy.
With use, VADs may themselves fail. In percutaneous catheters, the sutures or anchoring device may loosen, and the catheter may be pulled out partially or completely. Any catheter that has been partially pulled out should not be readvanced. If a chest radiograph does not show the catheter tip in the SVC, the catheter should be removed. The external parts of a catheter that are frequently manipulated may break. Some catheters have repair kits available from the manufacturers and can be safely repaired. If no repair kits are available, the catheter should be removed. In rare instances, an internal part of a VAD may break and embolize. This problem, which may be recognized only when the catheter is removed, should be addressed immediately with interventional radiology.
REMOVAL OF CENTRAL VASCULAR ACCESS DEVICES
VADs that are neither tunneled nor implanted can be removed at the bedside. Whenever resistance is encountered during removal, care should be taken to avoid severing the catheter. A radiograph or fluoroscopy should be used to determine whether the catheter has become kinked or knotted. In some cases, especially with PICC VADs, thrombosis may develop, preventing catheter removal. When a VAD has been in place for a prolonged period, especially in the case of centrally placed polyurethane catheters, a fistula, large enough to permit air entry after catheter removal, may develop. After VAD removal, the site should be dressed to prevent this from happening.
Tunneled Silastic catheters can also be removed at the bedside. However, if a tunneled catheter has a cuff (or cuffs) associated with it, any resultant adhesions may necessitate incision and dissection for catheter removal. Implanted catheters require surgical removal.