About half of nosocomial bloodstream infections occur in intensive care units, and the majority of them are associated with intravascular device. Central-venous-catheter-related bloodstream infections (CRBSIs) are an important cause of healthcare-associated infections.
Central venous catheters (CVCs) are integral to the modern clinical practices and are inserted in critically-ill patients for the administration of fluids, blood products, medication, nutritional solutions, and for hemodynamic monitoring. They are the main source of bacteremia in hospitalized patients and therefore should be used only if they are really necessary.
Risk factors for CRBSI include patient-, catheter-, and operator-related factors. Several factors have been proposed to participate in the pathogenesis of CRBSI.
Hospitalized patients with neutropenia are at high risk. However other host risk factors also include immune deficiencies in general, chronic illness, and malnutrition.
The catheter itself can be involved in 4 different pathogenic pathways:
- colonization of the catheter by microorganisms from the patient’s skin and occasionally the hands of healthcare workers,
- intraluminal or hub contamination,
- secondary seeding from a bloodstream infection, and, rarely,
- administration of contaminated infusate or additives
The diagnosis of CRBSI is often suspected clinically in a patient using a CVC who presents with fever or chills, unexplained hypotension, and no other localizing sign.
Diagnosis of CRBSI requires establishing the presence of bloodstream infection and demonstrating that the infection is related to the catheter.
Blood cultures should not be drawn solely from the catheter port as these are frequently colonized with skin contaminants, thereby increasing the likelihood of a false-positive blood culture
According to IDSA guidelines a definitive diagnosis of CRBSI requires culture of the same organism from both the catheter tip and at least one percutaneous blood culture. Alternatively culture of the same organism from at least two blood samples (one from a catheter hub and the other from a peripheral vein or second lumen) meeting criteria for quantitative blood cultures or differential time to positivity. Most laboratories do not perform quantitative blood cultures, but many laboratories are able to determine differential time to positivity. Quantitative blood cultures demonstrating a colony count from the catheter hub sample ≥3-fold higher than the colony count from the peripheral vein sample (or a second lumen) supports a diagnosis of CRBSI. Differential time to positivity (DTP) refers to growth detected from the catheter hub sample at least two hours before growth detected from the peripheral vein sample.
The CVC and arterial catheter, if present, should be removed and cultured if the patient has unexplained sepsis or erythema overlying the catheter insertion site or purulence at the catheter insertion site.
Antibiotic therapy for catheter-related infection is often initiated empirically. The initial choice of antibiotics will depend on the severity of the patient’s clinical disease, the risk factors for infection, and the likely pathogens associated with the specific intravascular device. Resistance to antibiotic therapy due to biofilm formation also has an important role in the management of bacteremia. In fact the nature of biofilm structure makes micro-organisms difficult to eradicate and confer an inherent resistance to antibiotics.
CRBSIs can be reduced by a range of interventions including closed infusion systems, aseptic technique during insertion and management of the central venous line, early removal of central venous lines and appropriate site selection.
Different measures have been implemented to reduce the risk for CRBSI, including use of maximal barrier, precautions during catheter insertion, effective cutaneous anti-sepsis, and preventive strategies based on inhibiting micro-organisms originating from the skin or catheter hub from adhering to the catheter.
Simultaneous application of multiple recommended best practices to manage CVCs has been associated with significant declines in the rates of CRBSI.
Education, and training of health care workers, and adherence to standardized protocols for insertion and maintenance of intravascular catheters significantly reduced the incidence of catheter-related infections and represent the most important preventive measures.