Enoxaparin inhibits fibrin sheath formation and decreases central venous catheter colonization following bacteremic challenge

Transient bacteremia promotes catheter-related central venous thrombosis through neutrophil extracellular traps

Formation of intravenous catheter-related thrombosis leads to central venous stenosis in patients requiring renal replacement therapy or chemotherapy infusion, yet the triggering or mechanisms remain unclear, especially in patients without symptoms of infection. In this study, we found that neutrophil extracellular traps (NETs) could be detected in the fibrin sheaths from dialysis patients without clinical manifestations of infection. Confocal microscopy revealed bacteria imbedded in NETs in the fibrin sheaths. Thirty-nine of 50 (78%) fibrin sheath specimens contained bacteria detectable by 16S ribosomal RNA genome typing with a predominance of Staphylococcus aureus (69%). In rat models, transient bacteremia of S. aureus induced NETs in enlarged fibrin sheaths, and treatment with DNase I alone significantly reduced both NET and fibrin sheath formation surrounding the catheter. Therefore, transient bacteremia could be a silent trigger that induces NET-related immunothrombosis enhancing catheter-related central venous stenosis.

The fibroblastic sleeve, the neglected complication of venous access devices: A narrative review

The presence of a vascular access device (or of any intravascular foreign body) inside the bloodstream is often associated with the formation of a connective tissue sleeve around the catheter (often named-erroneously-"fibrin sleeve"). Such sleeve is usually a physiological phenomenon with little or no clinical relevance, but its pathogenesis is still unclear, so that it is frequently confused with venous thrombosis; also, its relationship with other major catheter-related complications, such as venous thrombosis and bloodstream infection, is uncertain. This narrative review tries to convey in a systematic form the current knowledge about pathogenesis, incidence, clinical manifestations, diagnosis, and management of this phenomenon.

Central venous access device-related sheaths: a predictor of infective and thrombotic incidence?

Central vascular access device (CVAD)-related sheaths, sometimes described as ‘fibrin sheaths’, may result in minor or significant sequelae, from persistent withdrawal occlusion (PWO) to infective sheaths associated with increased morbidity and mortality. The authors studied 179 patients who underwent isotope scans, where isotope was infused via the CVAD. Isotope was found to bind to the sheaths around the catheters of some patients. The amount of uptake was taken to be an extent to which a sheath had developed around the CVAD. The degree of uptake of isotope was categorised into three groups: low uptake, moderate uptake and high uptake. Patients were then followed up from the date the CVAD was inserted to 12 months after the date of the isotope scan, until the device was removed or to the date the patient died, to identify incidence of infection, thrombosis and PWO. PWO incidence in all levels of uptake was around 5–7%. Bloodstream infection (BSI) incidence for low uptake was 7% (9/130), moderate uptake 10% (3/30) and for patients with significant uptake 16% (3/19). Thrombosis for no uptake was less than 1% (1/130), moderate uptake 7% (2/30), and significant uptake had no incidence of thrombosis. Total complications: no uptake 15%, moderate uptake 23% and significant uptake 21%. This single-centre study showed that patients with isotope-highlighted sheaths experienced higher incidence of infective, thrombotic and total complications.

Fibrin sheath-associated endovascular infection of the heart: the Trojan horse of indwelling central venous catheters

Chronic indwelling central venous catheters can result in formation of fibrin sheaths increasing risk of occlusion, thrombosis and infection. Endovascular infection of right-sided heart structures induced by such sheaths is very rare. A 48-year-old woman with end-stage renal disease initially treated for diabetic ketoacidosis developed persistent Staphylococcus epidermidis bacteraemia without an identifiable source. Although transthoracic echocardiography was unremarkable, transoesophageal echocardiography revealed a fibrin sheath and vegetations in superior vena cava-right atrium junction, which was the site of the tip of a central catheter that had been removed 2 months prior, consistent with fibrin sheath-associated endovascular infection. The bacteraemia cleared and clinical improvement was seen with prolonged intravenous vancomycin. In patients with unexplained bacteraemia and history of a central catheter, rare causes of endovascular infections of right-sided heart structures like fibrin sheaths should be considered. These can persist months after catheter removal. Transoesophageal echocardiogram should be used for earlier detection.

An engineered micropattern to reduce bacterial colonization, platelet adhesion and fibrin sheath formation for improved biocompatibility of central venous catheters

Background

Catheter-related bloodstream infections (CRBSIs) and catheter-related thrombosis (CRT) are common complications of central venous catheters (CVC), which are used to monitor patient health and deliver medications. CVCs are subject to protein adsorption and platelet adhesion as well as colonization by the natural skin flora (i.e. Staphylococcus aureus and Staphylococcus epidermidis). Antimicrobial and antithrombotic drugs can prevent infections and thrombosis-related complications, but have associated resistance and safety risks. Surface topographies have shown promise in limiting platelet and bacterial adhesion, so it was hypothesized that an engineered Sharklet micropattern, inspired by shark-skin, may provide a combined approach as it has wide reaching anti-fouling capabilities. To assess the feasibility for this micropattern to improve CVC-related healthcare outcomes, bacterial colonization and platelet interactions were analyzed in vitro on a material common for vascular access devices.

Methods

To evaluate bacterial inhibition after simulated vascular exposure, micropatterned thermoplastic polyurethane surfaces were preconditioned with blood proteins in vitro then subjected to a bacterial challenge for 1 and 18 h. Platelet adhesion was assessed with fluorescent microscopy after incubation of the surfaces with platelet-rich plasma (PRP) supplemented with calcium. Platelet activation was further assessed by monitoring fibrin formation with fluorescent microscopy after exposure of the surfaces to platelet-rich plasma (PRP) supplemented with calcium in a flow-cell. Results are reported as percent reductions and significance is based on t-tests and ANOVA models of log reductions. All experiments were replicated at least three times.

Results

Blood and serum conditioned micropatterned surfaces reduced 18 h S. aureus and S. epidermidis colonization by 70% (p ≤ 0.05) and 71% (p < 0.01), respectively, when compared to preconditioned unpatterned controls. Additionally, platelet adhesion and fibrin sheath formation were reduced by 86% and 80% (p < 0.05), respectively, on the micropattern, when compared to controls.

Conclusions

The Sharklet micropattern, in a CVC-relevant thermoplastic polyurethane, significantly reduced bacterial colonization and relevant platelet interactions after simulated vascular exposure. These results suggest that the incorporation of the Sharklet micropattern on the surface of a CVC may inhibit the initial events that lead to CRBSI and CRT.

Accumulation-associated protein enhances Staphylococcus epidermidis biofilm formation under dynamic conditions and is required for infection in a rat catheter model

Biofilm formation is the primary virulence factor of Staphylococcus epidermidis. S. epidermidis biofilms preferentially form on abiotic surfaces and may contain multiple matrix components, including proteins such as accumulation-associated protein (Aap). Following proteolytic cleavage of the A domain, which has been shown to enhance binding to host cells, B domain homotypic interactions support cell accumulation and biofilm formation. To further define the contribution of Aap to biofilm formation and infection, we constructed an aap allelic replacement mutant and an icaADBC aap double mutant. When subjected to fluid shear, strains deficient in Aap production produced significantly less biofilm than Aap-positive strains. To examine the in vivo relevance of our findings, we modified our previously described rat jugular catheter model and validated the importance of immunosuppression and the presence of a foreign body to the establishment of infection. The use of our allelic replacement mutants in the model revealed a significant decrease in bacterial recovery from the catheter and the blood in the absence of Aap, regardless of the production of polysaccharide intercellular adhesin (PIA), a well-characterized, robust matrix molecule. Complementation of the aap mutant with full-length Aap (containing the A domain), but not the B domain alone, increased initial attachment to microtiter plates, as did in trans expression of the A domain in adhesion-deficient Staphylococcus carnosus. These results demonstrate Aap contributes to S. epidermidis infection, which may in part be due to A domain-mediated attachment to abiotic surfaces.

The role of tissue plasminogen activator use and systemic hypercoagulability in central line-associated bloodstream infections

BACKGROUND

Central line-associated bloodstream infections (CLABSIs) impact patient outcomes and increase cost of hospitalization. In situ thrombus is known to promote microbial adhesion and colonization and potentially lead to CLABSI. Clinical validation of this theory, adjusting for presence of systemic hypercoagulability, is needed.

METHODS

This study is a retrospective review of all adult and pediatric patients with peripherally inserted central catheter placement over a 4-year period at our tertiary care center. Tissue plasminogen activator (TPA) use was utilized as indicator for line site thrombus. CLABSIs rates were compared in patients with or without TPA use, adjusting for the presence of hypercoagulable conditions, age, and severity of illness.

RESULTS

A total of 3,723 patients with peripherally inserted central catheter lines was evaluated, 40% of whom received TPA. The adjusted odds of developing a CLABSI was 3.59 times greater in those patients who received TPA compared with those who did not (95% confidence interval [CI]: 1.86-6.94). Neither severity of illness (odds ratio [OR], 1.00; 95% CI: 0.51-1.96) nor primary (OR, 3.41; 95% CI: 0.43-26.7) or secondary hypercoagulability (OR, 0.91; 95% CI: 0.44-1.88) were statistically associated with a higher risk of infection.

CONCLUSION

The use of TPA, as a possible indicator in situ thrombus, was associated with a higher risk of developing CLABSI. Neither primary nor secondary hypercoagulability was correlated with risk of developing CLABSI.

Rat jugular catheter model of biofilm-mediated infection

Staphylococcus epidermidis is now recognized as the primary cause of nosocomial catheter-mediated infections. Bacteria may be introduced exogenously via contamination of the catheter hub or insertion site and endogenously from sepsis. The in vivo model described in this chapter examines the infection resulting from hematogenous seeding of jugular vein catheters.

Fibrin sheath angioplasty: a technique to prevent superior vena cava stenosis secondary to dialysis catheters

Fibrin sheaths are a heterogeneous matrix of cells and debris that form around catheters and are a known cause of central venous stenosis and catheter failure. A total of 50 cases of central venous catheter fibrin sheath angioplasty (FSA) after catheter removal or exchange are presented. A retrospective review of an outpatient office database identified 70 eligible patients over a 19-month period. After informed consent was obtained, the dialysis catheter exiting the skin was clamped, amputated, and a wire was inserted. The catheter was then removed and a 9-French sheath was inserted into the superior vena cava, a venogram was performed. If a fibrin sheath was present, angioplasty was performed using an 8 × 4 or 10 × 4 balloon along the entire length of the fibrin sheath. A completion venogram was performed to document obliteration of the sheath. During the study, 50 patients were diagnosed with a fibrin sheath, and 43 had no pre-existing central venous stenosis. After FSA, 39 of the 43 patient's (91%) central systems remained patent without the need for subsequent interventions; 3 patients (7%) developed subclavian stenoses requiring repeat angioplasty and stenting; 1 patent (2.3%) developed an occlusion requiring a reintervention. Seven patients with prior central stenosis required multiple angioplasties; five required stenting of their central lesions. Every patient had follow-up fistulograms to document long-term patency. We propose that FSA is a prudent and safe procedure that may help reduce the risk of central venous stenosis from fibrin sheaths due to central venous catheters.

Alteplase use for malfunctioning central venous catheters correlates with catheter-associated bloodstream infections

OBJECTIVES

A catheter thrombosis and the presence of a catheter-associated bloodstream infection (CBSI) often occur simultaneously, but it is unclear if or to what degree the two complications relate. Several animal and adult studies indicate a relationship between fibrin sheaths and thrombi in the development of CBSIs. To date, there has been limited human investigation in the pediatric population to determine a clear link between the presence of a thrombus and bacteremia. The use of alteplase for malfunctioning central venous catheter may indicate the formation of intraluminal thrombus or fibrin sheath. A catheter that requires alteplase is at higher risk of a CBSI.

DESIGN

A retrospective chart review from July 2008 to December 2010.

SETTING

PICU.

PATIENTS

All patients with central catheters admitted to the PICU.

INTERVENTIONS

No interventions performed with the retrospective study.

MEASUREMENTS

Number of total central venous catheters, number of central venous catheters that received treatment with alteplase, and number of CBSIs.

MAIN RESULTS

Preliminary data during the study period identified 3,289 central venous catheters. Twelve percent of these catheters required at least one dose of alteplase. There were 40 CBSIs during this same time period of which 28% received alteplase during the 5 days preceding the positive blood culture. The odds ratio for getting a CBSI when alteplase is administered is 2.87 (confidence interval 1.42-5.80; p = 0.002). The average age of the central venous catheters at time of infection was not statistically different, 16.1 days in the alteplase catheters compared with 25.6 days for the catheters that did not receive alteplase (p = 0.6).

CONCLUSIONS

There is a positive correlation between the use of alteplase for malfunctioning central venous catheters and the development of a CASBI. This is likely associated with the presence of an intraluminal fibrin sheath or thrombus. This study adds evidence linking thrombus formation to CBSI.

New materials and devices for preventing catheter-related infections

Catheters are the leading source of bloodstream infections for patients in the intensive care unit (ICU). Comprehensive unit-based programs have proven to be effective in decreasing catheter-related bloodstream infections (CR-BSIs). ICU rates of CR-BSI higher than 2 per 1,000 catheter-days are no longer acceptable. The locally adapted list of preventive measures should include skin antisepsis with an alcoholic preparation, maximal barrier precautions, a strict catheter maintenance policy, and removal of unnecessary catheters. The development of new technologies capable of further decreasing the now low CR-BSI rate is a major challenge. Recently, new materials that decrease the risk of skin-to-vein bacterial migration, such as new antiseptic dressings, were extensively tested. Antimicrobial-coated catheters can prevent CR-BSI but have a theoretical risk of selecting resistant bacteria. An antimicrobial or antiseptic lock may prevent bacterial migration from the hub to the bloodstream. This review discusses the available knowledge about these new technologies.

Diagnosis and prevention of catheter-related infections

PURPOSE OF REVIEW

To highlight the major advances in diagnosing and preventing catheter-related infections published in research articles published between March 2004 and May 2007.

RECENT FINDINGS

The challenge remains to make the diagnosis of catheter-related infection with good accuracy without catheter removal. The differential time to obtain positive qualitative blood culture appeared to be the most accurate available technique. Many catheter-related bloodstream infections are preventable. Simple interventions are often useful and multimodal programs are very efficacious, particularly in the intensive care setting. For long-term catheter-related bloodstream infection prevention, patient education appeared promising. Interesting evidence suggested that anticoagulant, by decreasing the biofilm formation, could decrease the risk of infection. For short-term central venous catheter-related infections research is ongoing on antiseptic dressings. Antiseptic lock appeared promising for preventing long-term central venous catheter bloodstream infections.

SUMMARY

Nowadays, multimodal programs of catheter infection prevention are efficacious. Levels of catheter-related bloodstream infection of more than one or two per 1000 catheter-days are usually only found in the intensive care unit. It is a prerequisite to evaluate the cost-effectiveness of new techniques of prevention. As catheter-related bloodstream infections become rarer, strategies limiting unnecessary removal of catheters need to be developed and tested.