Line infection

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Intravascular lines and infection

Definitions

Controversial

Most commonly accepted definitions are:

- catheter related infection: bacteraemia attributable exclusively related to catheter. Requires isolation of same organism from blood and catheter. Need not necessarily be associated with signs of sepsis

- catheter related bloodstream infection: bacteraemia, signs of sepsis, same organism isolated from catheter or puncture site, negative culture of infusate

- catheter related sepsis: signs of sepsis plus colonization of catheter

Microbiology

- common organisms: coagulase negative staph. (predominantly Staph. epidermidis) and Staph. aureus. Gram negatives (Klebsiella, Pseudomonas, Serratia, Acinetobacter, Stenotrophomonas maltophilia and other enterobacteria) and fungi isolated more frequently in recent years.

-catheter colonization results from exogenous contamination of patient’s skin, hubs or whole system. Occurs at time of insertion or re-insertion. Skin insertion site most common source of colonization and infection for catheters <10 days old. From the skin insertion site organisms migrate down the external surface of the catheter to colonize the distal tip and produce bloodstream infection. Hub contamination is more common in long term catheters and results in colonization of the lumenal surface of the catheter. Haematogenous colonization and contaminated infusates are the other routes of colonization.

Risk factors

- type and material of catheter: polyethylene catheters associated with highest risk of colonization, PVC intermediate and silicon least. Antibiotic bonded catheters associated with lower incidence of colonization but not infection. Triple lumen catheters associated with higher risk but this may simply reflect different uses

- site and mode of catheterization: higher incidence of colonization with internal jugular lines than subclavian. Also higher incidence if multiple attempts at cannulation required or if surgical cut-down required. Guidewire exchange of catheters is associated with a non-significant trend toward a higher rate of catheter exit site infection and catheter-related bacteraemia but fewer non-infective complications

- dressing: not clear whether transparent semi-occlusive dressing best or sterile dry gauze dressing

- duration of catheterization: significant increase in risk of catheter-related infection after 4^th day but no benefit from routine changes of lines has been demonstrated

- patient factors: immunosuppression, infection, malignancy, tracheostomy, TPN, chronic haemodialysis

- strict use of barrier precautions (sterile gowns, gloves, masks etc) decreases infection risk

Diagnosis

- may be difficult. Certain features point toward a vascular catheter as source of infection:

bacteraemia or fungaemia in an immunocompetent paitent without underlying diseases
no identifiable local infection
presence of an intravascular device at the onset of fever
inflammation or purulence at the catheter insertion site or along the tunnel

abrupt onset of infection that is associated with fulminant shock
multiple blood cultures positive for organisms usually considered to be contaminants eg staphylococci (especially coagulase negative), Corynebacterium jeikeium, Bacillus species, Candida species, Malassezia species

- semi-quantitative culture of catheter tip and a 5 cm section of catheter taken from the part of the catheter distal to the insertion point is useful. The presence of >15 colonies is associated with high risk of infection. Roll plate method of culture less useful for detecting colonization of long term silicone catheters where lumenal colonization is more common. In these patients it may be more useful to take simultaneous cultures from central line and peripheral site. Presence of 5-10 times more colonies in culture of blood taken through the central line compared with peripheral blood diagnostic of catheter related infection. When PA catheter tips are cultured the introducer should be cultured as well.
- any pus expressed from catheter site should be gram stained and cultured

Prevention

Tunnelling

- there is some data which suggest that this reduces the incidence of infection particularly with internal jugular catheters

Ionic silver cuff

- silver impregnated subcutaneous collagen cuffs have been shown to decrease the rate of infection in critically ill patients with central venous catheters placed for between 5.6 and 9.1 days. Does not prevent infection of long term catheters. Provides a physical barrier to migration of micro-organisms and the silver ions have an antimicrobial effect

Antimicrobial hub

- does not prevent migration from skin insertion site down the external surface of the catheter.

Antimicrobial coating

- catheters coated with chlorhexidine and silver sulphadiazine have been found to be nearly 50% less likely to be colonized and at least 4 times less likely to produce infection than uncoated catheters. Catheters coated with minocycline and rifampicin were associated with a 3-fold reduction in catheter colonization and prevented catheter-related septicaemia compared with uncoated catheters. No antibiotic resistant organisms were recovered from patients managed with coated central lines.

Heparin-bonded or addition of heparin to infusion

- associated with a significant reduction in bacterial colonization and strong but non-significant trend toward decreased catheter-related bloodstream infection

Treatment

- simple removal of line may be sufficient but if signs of sepsis do not resolve antibiotic therapy should be started. Antibiotic therapy is recommended for catheter-related bloodstream infection.

- coagulase negative Staph.: 7 day course probably adequate if patient responds in 48-72 h

- Staph. aureus: in the absence of cardiac valvular disease and if patient responds within 3 days continue antibiotics for at least 2 weeks. Otherwise give 4 weeks.

- Candida: fluconazole for at least 14 days. Amphotericin for resistant Candida

- Gram +ve bacilli: vancomycin

- Gram –ve: usually non-aeruginosa Pseudomonas species or Stentrophomonas maltophilia. Give 1 week course

Central vein septic phlebitis

- unusual
- most often seen in patients with catheter-related infections that go unrecognized. This allows the proliferation of organisms to high levels within intravascular thrombi
– results in overwhelming sepsis with high-grade bacteraemia or fungaemia and/or septic emboli
– bacteraemia/fungaemia usually persists after removal of catheter