Catheter-associated bloodstream infections (CRBSI)

Definition

Catheter-associated bloodstream infections (CRBSI) are nosocomial infectious complications associated with using intravascular catheters. They are clinically manifested by local inflammatory changes (swelling, soreness, and hyperemia in the catheter area) or generalized infection (febrile fever, chills, and bacteremia). For laboratory confirmation of CRBSI, blood culture and microbiologic examination of the vascular catheter are performed. The catheter is removed at the first signs of CRBSI, and antibacterial and infusion therapy is prescribed. 

General information

Catheter-associated bloodstream infections (angiogenic, “catheter” infections) are a group of hospital-acquired infections that develop due to vascular catheterization. The incidence of angiogenic infections in ORIT departments ranges from 3 to 7 cases per 1000 catheter-days. More than 500 thousand such complications are registered annually in Europe and the USA. The need for central vascular access is high in intensive care units, hemodialysis, oncology, hematology, etc., which makes catheter-associated infections a multidisciplinary problem relevant to various medical fields.

Causes

Placement of an intravascular device is an invasive manipulation involving violation of the integrity of the skin and vascular wall, as well as insertion and retention of a foreign object in the vessel lumen. Catheter-related bloodstream infections are primarily associated with the insertion of a central venous catheter (CVC), infusion port system, or peripheral venous cannula. More often, CRBSIs develop during femoral vein catheterization, and less often – subclavian and internal jugular.

The development of angiogenic infections is preceded by contamination of the vascular device with pathogenic or opportunistic microorganisms. Sources and causes of contamination can be:

• skin infections in the area of the vascular prosthesis (pyoderma);
• non-compliance with aseptic requirements during manipulations with CVCs (improper treatment of the operating field, doctor’s hands);
• inadequate choice of catheter access, size, type, and material;
• frequent punctures of the vascular bed;
• poor care of the vascular prosthesis.

Among the etiologic agents causing CRBSI, the pathogens that are the most frequent cause of IBI prevail: staphylococci (47%, including Staphylococcus aureus – 25%), Enterobacteriaceae (27%), Acinetobacter (13%), Pseudomonas bacillus (9%), candida (5%), enterococci (3%) and others. The duration of catheterization plays a major role in the occurrence of intravascular infections: according to published data, after seven days of catheter placement in the vein, CRBSI develops in 5% of patients and after 1 month or more – in 36%.

Risk factors

Concomitant conditions contribute to the infection of intravenous catheters: diabetes mellitus, immunodeficiencies, immunosuppression, and hypoalbuminemia. The group of increased risk for the development of catheter-associated bloodstream infections includes patients who have a significant catheterization load (prolonged and repeated puncture of central veins):

• hemodialysis;
• massive infusion and transfusion therapy;
• undergoing chemotherapy;
• requiring efferent methods of detoxification;
• parenteral nutrition.

Classification

Currently, the classification of catheter-associated bloodstream infections recommended by the Hospital Infection Control Committee (USA) is used in medical circles. According to it, the following forms of CRBSI are distinguished:

1. Catheter colonization was confirmed by microbiological examination without any clinical manifestations.
2. Phlebitis: erythema, thickening, soreness of the catheterized vein on palpation.
3. Limited infection at the site of catheter placement: infiltrate painful tissue, hyperemia, and purulent discharge. The focus is 2 cm at maximum.
4. Infection of the subcutaneous pocket containing the installed port system: hyperemia and necrosis of the skin over the implanted device, purulent discharge in the subcutaneous pocket.
5. Tunnel infection: signs of inflammation extending along the catheter’s course more than 2 cm from the catheter site.
6. Bloodstream infections include bacteremia, fungemia, and sepsis, in which the same pathogen and distant catheters are isolated from the bloodstream.

Symptoms of CRBSI

Catheter-associated bloodstream infections can be localized (37%) or generalized (63%). The former is limited to the site of vascular prosthesis insertion, while the latter is characterized by bacteremia and systemic involvement. Local infections are represented by infiltrates, abscesses, and phlebitis directly related to the installed intravascular device. Generalized CRBSI is manifested by sepsis.

Signs of inflammation around the vascular catheter indicate a high probability of CRBSI: thickening and redness of the skin, pain, separation of purulent exudate, and impaired patency of the prosthesis. General symptoms of the infectious process—fever with chills—usually occur 20 minutes to 1.5 hours after using the catheter (blood collection, infusion of solutions). In severe cases, fever becomes febrile and almost constant, BP decreases, and signs of intoxication increase. Catheter-associated angiogenic sepsis develops.

Complications

The prolonged presence of the catheter in the vascular lumen increases the risk of thrombophlebitis and deep vein thrombosis. CRBSI can be complicated by septicopyemia—the formation of metastatic purulent effusions in variouslocalizations, such as bacterial endocarditis, abscessed pneumonia, septic arthritis, hematogenous osteomyelitis, etc. Patients die of septic shock, multi-organ disorders, and fatal thromboembolism.

Diagnosis

The clinical criterion for CRBSI is the appearance of symptoms of bloodstream infection 48 hours or more after CVC placement without other sources of infection. However, due to the low specificity of clinical data, the diagnosis of catheter-associated infection requires mandatory laboratory confirmation. For this purpose, a paired culture is performed:

• blood from the peripheral vein and the distal end of the intravascular catheter (or flush from the catheter). CRBSI is considered reliable when the same hemoculture is isolated simultaneously from peripheral blood and the vascular;
• blood from the vascular prosthesis and vein. CRBSI is indicated by a more than 3-fold excess of colony counts in the blood sample from the catheter compared to the venous sample.

Blood sampling should be done twice, before the start of antibiotic therapy, at the height of fever. To clarify complications, instrumental studies are performed. If purulent thrombophlebitis is suspected, an ultrasound examination of vessels and phlebography are performed. Excluding or confirming septic endocarditis helps with transthoracic echocardiography. Methods of diagnosis of purulent processes of the bone and joint system are X-ray and ultrasound of joints.

Angiogenic infections are differentiated from bacteremia associated with other primary sources, such as pneumonia, purulent wounds, and intra-abdominal abscesses.

Treatment of catheter-associated bloodstream infections

In the absence of local infection, an attempt is made to sanitize the catheter by the method of “antibacterial lock” – the antibiotic solution is injected into the lumen of the CVC and left for several hours. In the presence of marked signs of local inflammation, removing the infected intravascular device is necessary immediately. Localized forms of CRBSI may require the application of antiseptic and ointment dressings, opening abscesses, and purulent congestion with subsequent management of purulent wounds according to the accepted protocol.

Systemic antibiotic therapy is started without waiting for the results of bacterial examination; if necessary, it is further adjusted, considering the isolated flora and sensitivity. Penicillins, cephalosporins, glycopeptides, and aminoglycosides are usually used for at least 14 days. Amphotericin B and fluconazole are prescribed for the therapy of fungal infection. The phenomenon of thrombophlebitis is the introduction of anticoagulants and fibrinolytics. With regard to phlegmon, purulent arthritis, osteomyelitis, abscesses of various localizations, appropriate surgical tactics are applied.

All these treatment options are available in more than 200 hospitals worldwide (https://doctor.global/results/diseases/catheter-related-bloodstream-infection-crbsi). For example, Replacement of central venous catheter can be done in 12 clinics across Germany for an approximate price of $3,3K (https://doctor.global/results/europe/germany/all-cities/all-specializations/procedures/replacement-of-central-venous-catheter). 

Prognosis

Due to their prevalence and antibiotic resistance, catheter-associated bloodstream infections (CRBSI) are a severe challenge to modern medicine. They prolong hospitalization, worsen the outcome of the underlying disease, and require significant financial outlays for treatment. Uncomplicated angiogenic infections usually resolve within a few days. CRBSI, complicated by local suppurative processes or bacteremia, has a severe prognosis and high mortality.

Prevention

Modern protocols regulate the rules of catheter insertion and care. The greatest attention is paid to compliance with the norms of asepsis and antisepsis (disinfection of the operating field and the hands of personnel, storage of catheter caps in chlorhexidine solution, skin treatment, and change of dressings around catheters). It is necessary to properly select an intravascular device and place it for catheterization, to limit the life of intravenous probes as much as possible, and to use heparin and antibacterial locks.