Catheter-Associated Infections

Chronic indwelling catheters are commonly placed in cancer patients, as they permit frequent, long-term vascular access for drug and blood product administration, hyperalimentation, and blood drawing.

Hickman and Broviac catheters have an exit site on the skin surface, are anchored with a subcutaneous Dacron felt cuff, and have a subcutaneous tunnel entering the venous system (via the subclavian, external jugular, internal jugular, cephalic, saphenous, or femoral veins), where they lead into the superior or inferior vena cava or right atrium. These catheters can have single, double, or triple lumens. Another type of catheter has a totally implanted port (Port-A-Cath) that is accessed percutaneously. Use of peripherally inserted central catheters (PICCs) is becoming more common.

There are four types of catheter-associated infections: exit-site infections, tunnel infections, catheter-associated bacteremia/fungemia, and septic thrombophlebitis.

There are approximately 0.4 infections per 100 catheter-days and 0.26 bacteremias per 100 catheter-days.

Etiology

It is assumed that catheter-associated infections are caused by tracking of organisms from the skin along the catheter, contamination of the lumen during manipulation, or direct seeding during bacteremia/fungemia.

By far, the most common microorganisms associated with catheter-associated infections are coagulase-negative staphylococci. The next most common pathogen is coagulase-positive S aureus.

Less common pathogens include gram-negative bacilli, gram-positive bacilli (such as Corynebacterium JK and Bacillus species), fungi (especially Candida species), and rapidly growing mycobacteria.

Signs and Symptoms

Exit-site infections may be manifested by local erythema, warmth, and tenderness. Purulent drainage may be present.

Tunnel infections are characterized by tenderness along the subcutaneous track.

Catheter-associated bacteremia/fungemia usually displays no local findings. A fever may be the only sign, but other signs and symptoms of sepsis or even full-blown septic shock syndrome may be present.

Likewise, septic thrombophlebitis may have no findings, except those associated with sepsis or venous thrombosis (edema).

Diagnosis

In any cancer patient with a central venous catheter who becomes febrile or is shown to be bacteremic or fungemic, a catheter-associated infection should be suspected. Without the signs or symptoms of an exit-site or tunnel infection, however, a diagnosis may be difficult.

Cultures

Two blood cultures should be drawn: one from the catheter(s) and one from a peripheral vein. There are two methods that may be helpful in making a diagnosis of right atrial catheter infection. Both depend upon drawing both (catheter and peripheral vein) blood cultures simultaneously. In the first method, quantitative colony counts are determined from both cultures. If the catheter colony counts are three-fold higher than the colony count from the peripheral vein, it suggests a catheter-associated infection. The second method, differential time to positivity (DTP), requires an automated continuously monitored blood culture system, which determines the time at which a blood culture turns positive. If the catheter culture turns positive at least 2 hours before the peripheral vein culture, it suggests a catheter-associated infection. A catheter infection should be assumed when the organism isolated is a coagulase-negative Staphylococcus, Corynebacterium, Bacillus, or Candida species or a mycobacterium.

If signs are consistent with an exit-site or tunnel infection, an attempt should be made to culture any exit-site drainage.

Treatment

Catheter removal

Although it was once believed that all catheters had to be removed to eradicate infection, it is now clear that many catheters can be salvaged. An exception to this guideline would be if the organism isolated is Corynebacterium JK, a Bacillus species, a Candida organism, or a rapidly growing mycobacterium. Some physicians would add to this list S aureus, VRE, P aeruginosa, polymicrobial bacteremia, and Fusarium species. The catheter also should be removed in patients with sepsis with hemodynamic instability, septic thrombophlebitis, or evidence of septic emboli. A tunnel infection or pocket-space abscess should prompt catheter removal as well. Finally, fever or bacteremia that persists (72 hours or longer) after therapy has been initiated necessitates removal of the catheter if there is no other source of infection.

Antibiotic therapy

Empiric therapy. If a catheter-associated infection is suspected, vancomycin should be initiated empirically. For institutions that have high rates of MRSA with vancomycin MIC (minimum inhibitory concentration) values > 2 µg/mL, alternative agents should be used, such as linezolid or daptomycin (Cubicin) (do not use daptomycin in respiratory infections; this agent is inactivated by surfactant in the lungs). If the patient is known to be colonized with VRE, then empiric therapy with quinupristin/dalfopristin (for Enterococcus faecium only), linezolid, or daptomycin should be considered.

Specific therapy. When a microorganism has been isolated and tested for sensitivity, specific antimicrobial therapy should be adjusted accordingly. If the catheter is left in place, a minimum of 14 days of parenteral (not oral) therapy should be administered through the catheter (rotating through each port), and follow-up cultures should be obtained.

For documented catheter-related infections caused by coagulase-negative staphylococci, the catheter may be retained using systemic therapy with or without antibiotic-lock therapy.

Prolonged treatment (4 to 6 weeks) is recommended for complicated catheter-related infections, defined as the presence of deep tissue infection, endocarditis, septic thrombosis, or persistent bacteremia or fungemia occurring > 72 hours after catheter removal in a patient who has received appropriate antimicrobials.

Search for infectious metastasis

Whether or not the catheter is removed, if the patient remains febrile, a search for sources of metastatic infection (lungs, liver, spleen, brain, heart valves) should be initiated.

Fibrinolytics and anticoagulants

The use of fibrinolytics and anticoagulation is controversial. Anticoagulation is indicated in cases of septic thrombophlebitis when the deep venous system is involved.

Hand hygeine, maximal sterile barrier precautions, and cutaneous antisepsis with chlorhexidine during central venous catheter insertion are recommended.