Catheter-related bloodstream infections (CRBI) are nosocomial infectious complications associated with the use of intravascular catheters. Clinically manifested by local inflammatory changes (swelling, soreness, hyperemia in the catheter area) or generalized infection (febrile fever, chills, bacteremia). For laboratory confirmation of CRBI, blood is seeded for hemoculture and microbiological examination of the vascular catheter. At the first signs of CRBI, the catheter is removed, antibacterial, infusion therapy is prescribed.
Catheter-related bloodstream infections (angiogenic, “catheter” infections) are a group of nosocomial infections that develop as a result of vascular catheterization. The incidence of angiogenic infections in ICU departments ranges from 3 to 7 cases per 1000 catheter days. In Europe and the USA, more than 500 thousand such complications are registered annually. 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 for various medical fields.
The installation of an intravascular device (IVD) is an invasive manipulation associated with a violation of the integrity of the skin and vascular wall, the introduction and abandonment of a foreign object in the lumen of the vessel. Catheter infections of the bloodstream in most cases are associated with the installation of a central venous catheter (CVC), an infusion port system, and a peripheral venous cannula. More often, catheter-related bloodstream infections develop during catheterization of the femoral vein, less often – subclavian and internal jugular.
The development of angiogenic infections is preceded by contamination of the vascular device by pathogenic or conditionally pathogenic microorganisms. The sources and causes of contamination may be:
- skin infections in the area of vascular prosthesis (pyoderma);
- non-compliance with the requirements of asepsis when manipulating CVC (improper treatment of the operating field, doctor’s hands);
- inadequate choice of access, size, type and material of the catheter;
- frequent punctures of the vascular bed;
- poor care of the vascular prosthesis.
Among the etiological agents that cause catheter-related bloodstream infections, pathogens that are the most common cause of VBI predominate: Staphylococci (47%, including Staphylococcus aureus ‒ 25%), Enterobacteria (27%), Acinetobacteria (13%), Pseudomonas aeruginosa (9%), Candida (5%), enterococci (3%) and others . The term of catheterization plays an important role in the occurrence of intravascular infections: according to published data, after 7 days of the catheter in the vein, CRBI develops in 5% of patients, after 1 month or more – in 36%.
Infection of intravenous catheters is facilitated by concomitant conditions: diabetes mellitus, immunodeficiency and immunosuppression, hypoalbuminemia. The group at increased risk for the development of catheter-associated bloodstream infections includes patients with a significant catheterization load (prolonged and repeated puncture of central veins):
- those on hemodialysis;
- receiving massive infusion-transfusion therapy;
- undergoing chemotherapy;
- requiring efferent detoxification methods;
- those in need of parenteral nutrition.
The mechanism of CRBI development is implemented in three main ways. Most often, the infection enters the bloodstream from the seeded skin along the outer surface of the catheter (extraluminally). This way is most relevant in the early stages after catheter placement (the first 10-15 days). Subsequently, the proportion of intraluminal infection increases when the infection spreads along the inside of the prosthesis through contaminated infusion media, cannulas of syringes and transfusion systems. Hematogenic infection is also possible, in which pathogens settle on the catheter, spreading with the blood flow from other sources (with pneumonia, pancreatitis, etc.).
The intravascular device is a foreign body, therefore, in response to its introduction, the body produces various protein substances that separate it from its own tissues. Among them are fibrin and fibronectin, to which coagulase is easily attached – an enzyme produced by many pathogens, in particular, Staphylococcus aureus and candida.
As a result of this adhesion, a biofilm is formed inside the vascular prosthesis, protecting microbial colonies from the effects of antibiotics and immune system cells. This contributes to the transition of the infection into a persistent chronic form. Microbial biofilms are formed on the inner surface of implantable devices in 40% of cases.
The presence of biofilm reduces the sensitivity of pathogens to antibiotics by hundreds of times, contributes to an increase in the share of antibiotic-resistant strains resistant to almost all known antimicrobial drugs in the structure of the BBI. The growth of colonies of microorganisms is accompanied by fragmentation of the biofilm and the entry of pathogens into the bloodstream, which leads to the development of bacteremia and sepsis.
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 catheter-related bloodstream infections are distinguished:
- Colonization of the catheter, confirmed by microbiological examination, in the absence of any clinical manifestations.
- Phlebitis: erythema, thickening, tenderness of the catheterized vein during palpation.
- Limited infection at the catheter installation site: infiltration, tissue soreness, hyperemia, presence of purulent discharge, focus no more than 2 cm.
- Infection of the subcutaneous pocket containing the installed port system: hyperemia and necrosis of the skin above the implantable device, purulent discharge in the subcutaneous pocket.
- Tunnel infection: signs of inflammation spreading along the catheter more than 2 cm from the place of its installation.
- Bloodstream infections: bacteremia, fungemia, sepsis, in which the same pathogen is seeded from the bloodstream and from the removed IVD.
- CRBI associated with the infusion medium: contaminated solutions, hemocomponents.
Catheter-associated bloodstream infections can be local (37%) and generalized (63%). The first of them are limited to the place of installation of the vascular prosthesis, the second are characterized by bacteremia and systemic lesion. Local infections are represented by infiltrates, abscesses, phlebitis, directly related to the installed intravascular device. Generalized CRBI is manifested by sepsis.
A high probability of CRBI is indicated by the appearance of signs of inflammation around the vascular catheter: thickening and redness of the skin, pain, separation of purulent exudate, violation of the patency of the prosthesis. Common symptoms of the infectious process ‒ fever with chills ‒ usually occur 20 minutes to 1.5 hours after using the boat (blood collection, infusion of solutions). In severe cases, the fever becomes febrile and almost constant, blood pressure decreases, signs of intoxication increase. Catheter-associated angiogenic sepsis develops.
Prolonged presence of the catheter in the vascular lumen increases the risk of thrombophlebitis, deep vein thrombosis. CRBI can be complicated by septicopyemia ‒ the formation of metastatic purulent screenings of various localization. Among them are bacterial endocarditis, abscessing pneumonia, septic arthritis, hematogenous osteomyelitis, etc. The cause of death of patients is septic shock, multiple organ disorders, fatal thromboembolism.
The clinical criterion of CRBI is the appearance of symptoms of a bloodstream infection in a patient 48 hours or more after the installation of CVC in the absence of 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, paired sowing is performed:
- blood from the peripheral vein and the distal end of the intravascular catheter (or flushing from it). CRBI is considered reliable with simultaneous isolation of the same hemoculture from peripheral blood and vascular probe (>15 CFU semi-quantitatively and >102 CFU quantitatively);
- blood from the vascular prosthesis and vein. The CRBI is indicated by a more than 3-fold excess of the number of colonies in the blood sample from the catheter compared to the venous sample.
Blood sampling must be performed twice, before the start of antibiotic therapy, at the height of fever. Instrumental studies are carried out to clarify complications. If purulent thrombophlebitis is suspected, vascular ultrasound and phlebography are performed. Transthoracic EchOX helps to exclude or confirm septic endocarditis. Methods of diagnosis of purulent processes of the osteoarticular system are X-rays, ultrasound of the joints.
Angiogenic infections differentiate with bacteremia associated with other primary sources: pneumonia, purulent wounds, intraabdominal abscesses, etc.
In the absence of a local infection, an attempt is made to sanitize the catheter using the “antibacterial lock” method ‒ an antibiotic solution is injected into the lumen of the CVC and left for several hours. In the presence of pronounced signs of local inflammation, immediate removal of the infected intravascular device is necessary. With local forms of CRBI, it may be necessary to apply antiseptic and ointment dressings, open abscesses and purulent swelling, followed by the management of a purulent wound according to the accepted protocol.
Systemic antibiotic therapy is started without waiting for the results of back-sowing, if necessary, it is further adjusted taking into account the selected flora and sensitivity. Penicillins, cephalosporins, glycopeptides, aminoglycosides with a duration of at least 14 days are usually used. For the treatment of fungal infection, amphotericin B and fluconazole are prescribed. With the phenomena of thrombophlebitis, the introduction of anticoagulants, fibrinolytics is indicated. With regard to phlegmon, purulent arthritis, osteomyelitis, abscesses of various localization, appropriate surgical tactics are used.
Catheter-associated bloodstream infections are a serious challenge to modern medicine due to their prevalence and antibiotic resistance. They lengthen the time of hospitalization, aggravate the outcome of the underlying disease, and require significant financial costs for treatment. Uncomplicated angiogenic infections are usually resolved within a few days. CRBI, complicated by a local suppurative process or bacteremia, have a serious prognosis and high mortality.
Modern protocols clearly regulate the rules of installation and maintenance of the IVD. The greatest attention is paid to compliance with the norms of asepsis and antiseptics (disinfection of the operating field and hands of personnel, storage of catheter caps in chlorhexidine solution, skin treatment and changing of bandages around the IVD). It is necessary to correctly choose an intravascular device and a place for catheterization, limit the service life of intravenous probes as much as possible, use heparin and antibacterial locks.