Does the fibrin coat around a central venous catheter influence catheter-related sepsis?

Biomedical Silicones: Leveraging Additive Strategies to Propel Modern Utility

Silicones have a long history of use in biomedical devices, with unique properties stemming from the siloxane (Si-O-Si) backbone that feature a high degree of flexibility and chemical stability. However, surface, rheological, mechanical, and electrical properties of silicones can limit their utility. Successful modification of silicones to address these limitations could lead to superior and new biomedical devices. Toward improving such properties, recent additive strategies have been leveraged to modify biomedical silicones and are highlighted herein.

Nonconformity of biofilm formation in vivo and in vitro based on Staphylococcus aureus accessory gene regulator status

Staphylococcus aureus is an opportunistic, pathogenic bacteria that causes significant morbidity and mortality. As antibiotic resistance by S. aureus continues to be a serious concern, developing novel drug therapies to combat these infections is vital. Quorum sensing inhibitors (QSI) dampen S. aureus virulence and facilitate clearance by the host immune system by blocking quorum sensing signaling that promotes upregulation of virulence genes controlled by the accessory gene regulator (agr) operon. While QSIs have shown therapeutic promise in mouse models of S. aureus skin infection, their further development has been hampered by the suggestion that agr inhibition promotes biofilm formation. In these studies, we investigated the relationship between agr function and biofilm growth across various S. aureus strains and experimental conditions, including in a mouse model of implant-associated infection. We found that agr deletion was associated with the presence of increased biofilm only under narrow in vitro conditions and, crucially, was not associated with enhanced biofilm development or enhanced morbidity in vivo.

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.

Thromboresistance of Polyurethanes Modified with PEO-Silane Amphiphiles

Surface-induced thrombosis is problematic in blood-contacting devices composed of silicones or polyurethanes (PUs). Poly(ethylene oxide)-silane amphiphiles (PEO-SA) are previously shown effective as surface modifying additives (SMAs) in silicones for enhanced thromboresistance. This study investigates PEO-SAs as SMAs in a PU at various concentrations: 5, 10, 25, 50, and 100 µmol g^-1 PU. PEO-SA modified PUs are evaluated for their mechanical properties, water-driven surface restructuring, and adhesion resistance against a human fibrinogen (HF) solution as well as whole human blood. Stability is assessed by monitoring hydrophilicity, water uptake, and mass loss following air- or aqueous-conditioning. PEO-SA modified PUs do not demonstrate plasticization, as evidenced by minimal changes in glass transition temperature, modulus, tensile strength, and percent strain at break. These also show a concentration-dependent increase in hydrophilicity that is sustained following air- and aqueous-conditioning for concentrations ≥25 µmol g^-1 . Additionally, water uptake and mass loss are minimal at all concentrations. Although protein resistance is not enhanced versus an HF solution, PEO-SA modified PUs have significantly reduced protein adsorption and platelet adhesion from human blood at concentrations ≥10 µmol g^-1 . Overall, this study demonstrates the versatility of PEO-SAs as SMAs in PU, which leads to enhanced and sustained hydrophilicity as well as thromboresistance.

A polymer-based anti-quorum catheter coating to challenge MDR Staphylococcus aureus: in vivo and in vitro approaches

BACKGROUND

MDR Staphylococcus aureus is a major aetiological agent of catheter-associated infections. A quorum sensing targeted drug development approach proves to be an effective alternative strategy to combat such infections.

METHODS

Intravenous catheters were coated with polymethacrylate copolymers loaded with the antivirulent compound 2-[(methylamino)methyl]phenol (2MAMP). The in vitro drug release profile and kinetics were established. The anti-biofilm effect of the coated catheters was tested against clinical isolates of MDR S. aureus. The in vivo studies were carried out using adult male Wistar rats by implanting coated catheters in subcutaneous pockets. Histopathological analysis was done to understand the immunological reactions induced by 2MAMP.

RESULTS

A uniform catheter coating of thickness 0.1 mm was achieved with linear sustained release of 2MAMP for 6 h. The coating formulation was cytocompatible. The in vitro and in vivo anti-adherence studies showed reduced bacterial accumulation in coated catheters after 48 h. The histopathological results confirmed that the coated catheter did not bring about any adverse inflammatory response.

CONCLUSIONS

The developed anti-quorum-coated catheter that is non-toxic and biocompatible has the potential to be used in other medical devices, thereby preventing catheter-associated infections.

Fibrin sheath of a peripherally inserted central catheter undepicted with gray-scale (real-time B-mode) ultrasonography: A case report

An 11-year-old male was admitted to our hospital with the acute exacerbation of chronic heart failure. A peripherally inserted central catheter (PICC) was inserted from the left forearm. Ten days after its insertion, the withdrawal of PICC was attempted because of occlusion. However, it was not possible to remove PICC because a fibrin sheath had attached around its tip. A color Doppler and probe compression technique revealed the presence of a fibrin sheath, which could not be detected by gray-scale (real-time B-mode) ultrasonography. This case demonstrated that the color Doppler and probe compression technique is useful for detecting a fibrin sheath.

Protein Resistant Polymeric Biomaterials

Toward improving implantable medical devices as well as diagnostic performance, the development of polymeric biomaterials having resistance to proteins remains a priority. Herein, we highlight key strategies reported in the recent literature that have relied upon improvement of surface hydrophilicity via direct surface modification methods or with bulk modification using surface modifying additives (SMAs). These approaches have utilized a variety of techniques to incorporate the surface hydrophilization agent, including physisorption, hydrogel network formation, surface grafting, layer-by-layer (LbL) assembly and blending base polymers with SMAs. While poly(ethylene glycol) (PEG) remains the gold standard, new alternatives have emerged such as polyglycidols, poly(2-oxazoline)s (POx), polyzwitterions, and amphiphilic block copolymers. While these new strategies provide encouraging results, the need for improved correlation between in vitro and in vivo protein resistance is critical. This may be achieved by employing complex protein solutions as well as strides to enhance the sensitivity of protein adsorption measurements.

Antifouling silicones based on surface-modifying additive amphiphiles

Surface modifying additives (SMAs), which may be readily blended into silicones to improve anti-fouling behavior, must have excellent surface migration potential and must not leach into the aqueous environment. In this work, we evaluated the efficacy of a series of poly(ethylene oxide) (PEO)-based SMA amphiphiles which varied in terms of crosslinkability, siloxane tether length (m) and diblock versus triblock architectures. Specifically, crosslinkable, diblock PEO-silane amphiphiles with two oligodimethylsiloxane (ODMS) tether lengths [(EtO)3Si-(CH2)3-ODMS m -PEO8, m = 13 and 30] were compared to analogous non-crosslinkable, diblock (H-Si-ODMS m -PEO8) and triblock (PEO8-ODMS m -PEO8) SMAs. Prior to water conditioning, while all modified silicone coatings exhibited a high degree of water-driven surface restructuring, that prepared with the non-crosslinkable diblock SMA (m = 13) was the most hydrophilic. After conditioning, all modified silicone coatings were similarly hydrophilic and remained highly protein resistant, with the exception of PEO8-ODMS 30 -PEO8. Notably, despite twice the PEO content, triblock SMAs were not superior to diblock SMAs. For diblock SMAs, it was shown that water uptake and leaching were also similar whether or not the SMA was crosslinkable.

In Vitro and In Vivo Effectiveness of an Innovative Silver-Copper Nanoparticle Coating of Catheters To Prevent Methicillin-Resistant Staphylococcus aureus Infection

In this study, silver/copper (Ag/Cu)-coated catheters were investigated for their efficacy in preventing methicillin-resistant Staphylococcus aureus (MRSA) infection in vitro and in vivo Ag and Cu were sputtered (67/33% atomic ratio) on polyurethane catheters by direct-current magnetron sputtering. In vitro, Ag/Cu-coated and uncoated catheters were immersed in phosphate-buffered saline (PBS) or rat plasma and exposed to MRSA ATCC 43300 at 10(4) to 10(8) CFU/ml. In vivo, Ag/Cu-coated and uncoated catheters were placed in the jugular vein of rats. Directly after, MRSA (10(7) CFU/ml) was inoculated in the tail vein. Catheters were removed 48 h later and cultured. In vitro, Ag/Cu-coated catheters preincubated in PBS and exposed to 10(4) to 10(7) CFU/ml prevented the adherence of MRSA (0 to 12% colonization) compared to uncoated catheters (50 to 100% colonization; P < 0.005) and Ag/Cu-coated catheters retained their activity (0 to 20% colonization) when preincubated in rat plasma, whereas colonization of uncoated catheters increased (83 to 100%; P < 0.005). Ag/Cu-coating protection diminished with 10(8) CFU/ml in both PBS and plasma (50 to 100% colonization). In vivo, Ag/Cu-coated catheters reduced the incidence of catheter infection compared to uncoated catheters (57% versus 79%, respectively; P = 0.16) and bacteremia (31% versus 68%, respectively; P < 0.05). Scanning electron microscopy of explanted catheters suggests that the suboptimal activity of Ag/Cu catheters in vivo was due to the formation of a dense fibrin sheath over their surface. Ag/Cu-coated catheters thus may be able to prevent MRSA infections. Their activity might be improved by limiting plasma protein adsorption on their surfaces.

Infective Endovascular Fibrin Sheath Vegetations—A New Cause of Bacteremia Detected by Transesophageal Echocardiogram

BACKGROUND/PURPOSE

A fibrin sheath is a circumferential sleeve of endothelium that forms around the surface of implanted central venous catheters and frequently remains intact within the lumen of the vein after removal of the catheters. We describe a new entity of infective endovascular fibrin sheath vegetations.

METHODS

Records of patients hospitalized and found to have echocardiographically identified infective endovascular fibrin sheath vegetations at our institution, Cedars Sinai Medical Center, from 2010 to 2014 were reviewed for clinical variables of interest. Collected data included medical history, physical examination findings, laboratory, microbiology, imaging, a prior history of presence of a central venous catheter, treatment, and outcomes.

RESULTS

Eleven patients (20-77 years old; 6 women, 5 men) were found by transesophageal echocardiogram to have fibrin sheaths. All of the infective endovascular fibrin sheath vegetations were identified by transesophageal echocardiography, while none were seen with transthoracic echocardiography. Eight of 11 patients were critically ill, septic, and admitted to the Intensive Care Unit. Six patients were intubated and required vasopressor therapy. All cases were treated with long-term antibiotics, 5 were treated with anticoagulation, and 2 were treated with mechanical thrombectomy. Mortality was 36%, with death ranging from 44 to 251 days after diagnosis. The 90-day hospital readmission rate was 55%.

CONCLUSION

Infective endovascular fibrin sheath vegetations are not seen with transthoracic echocardiogram. They may be overlooked and not seen by transesophageal echocardiogram unless the vena cava is adequately imaged. Moreover, fibrin sheath vegetations are associated with a high morbidity and mortality. They should be treated as a serious endovascular infection and managed with aggressive medical or interventional therapies, or both.

Enhancing the protein resistance of silicone via surface-restructuring PEO-silane amphiphiles with variable PEO length

Silicones with superior protein resistance were produced by bulk-modification with poly(ethylene oxide) (PEO)-silane amphiphiles that demonstrated a higher capacity to restructure to the surface-water interface versus conventional non-amphiphilic PEO-silanes. The PEO-silane amphiphiles were prepared with a single siloxane tether length but variable PEO segment lengths: α-(EtO)3Si(CH2)2-oligodimethylsiloxane13-block-poly(ethylene oxide) n -OCH3 (n = 3, 8, and 16). Conventional PEO-silane analogues (n = 3, 8 and 16) as well as a siloxane tether-silane (i.e. no PEO segment) were prepared as controls. When surface-grafted onto silicon wafer, PEO-silane amphiphiles produced surfaces that were more hydrophobic and thus more adherent towards fibrinogen versus the corresponding PEO-silane. However, when blended into a silicone, PEO-silane amphiphiles exhibited rapid restructuring to the surface-water interface and excellent protein resistance whereas the PEO-silanes did not. Silicones modified with PEO-silane amphiphiles of PEO segment lengths n = 8 and 16 achieved the highest protein resistance.

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.

In vivo quantitative assessment of catheter patency in rats

Formation of fibrin sleeves around catheter tips is a central factor in catheter failure during chronic implantation, and such tissue growth can occur despite administration of anticoagulants. We developed a novel method for monitoring catheter patency. This method recognizes the progressive nature of catheter occlusion, and tracks this process over time through measurement of changes in catheter resistance to a standardized 1 mL bolus infusion from a pressurized reservoir. Two indirect measures of catheter patency were used: (a) reservoir residual pressure and (b) reservoir discharge time. This method was applied to the study of catheter patency in rats comparing the effect of catheter material (silastic, polyurethane, Microrenathanetrade mark), lock solution (heparin, heparin/dexamethasone) and two different cannulation sites (superior vena cava via the external jugular vein, inferior vena cava via the femoral vein). Our findings reveal that application of flexible smaller-size silastic catheters and a dexamethasone lock solution resulted in prolonged catheter patency. Patency could be maintained over nine weeks with the femoral vein catheters, compared with five weeks with the external jugular vein catheters. The current method for measuring catheter patency provides a useful index for the assessment of tissue growth around the catheter tip. The method also provides an objective and quantitative way of comparing changes in catheter patency for different surgical methods and catheter types. Our method improves on the conventional method of assessing catheter occlusion by judging the ability to aspirate from the catheter.

Impact of short-term hemodialysis catheters on the central veins: a catheter venographic study

OBJECTIVE

To determine the incidence of pericatheter sleeve formation, thrombus formation, and stenosis of the central veins in hemodialysis patients with temporary catheters.

METHODS AND MATERIAL

In this prospective study, 57 patients (40 males, 17 females) with temporary dialysis catheters had catheter venography by pulling back the catheter just before removal. Patient's age range was 25-87 years (mean age, 51 years). The venographic studies were evaluated for pericatheter sleeve formation, thrombus formation, and stenosis of the brachiocephalic vein (BCV) and the superior vena cava (SVC). The IJV could only be evaluated if there was adequate filling during contrast administration. In a subgroup of patients who had had only right IJV or only right SCV catheters, impact of these catheters on the central veins was compared.

RESULTS

The catheter location was right internal jugular vein (IJV) in 26 cases, right subclavian vein (SCV) in 27 cases, left IJV in 1 case, and left SCV in 3 cases. Thirty-two patients (56%) had had only one temporary catheter and the rest had had more than one inserted. The mean dwell time for the catheters was 21 days (range 7-59 days). A pericatheter sleeve was detected on venography in 32 (56%) patients and thrombus formation was noted in 16 patients (28%). A total of 41 patients (72%) exhibited pericatheter sleeve and/or thrombus formation. While 19 of the 32 patients (59%) without previous catheterization had a sleeve around the catheter, only 13 (52%) of 25 patients who had had multiple catheters inserted had a sleeve (P > 0.005). Of the eight patients (14%) with BCV stenosis, two had >50% stenosis. Only one patient (2%) had mild stenosis of the SVC. Three patients out of 15 (20%) who had diagnostic venography for the IJV had severe stenosis of the vein. Pericatheter sleeve formation was more frequent in women (P < 0.005). However, there were no statistical differences with respect to pericatheter sleeve formation, luminal filling defect and BCV stenosis when patients were grouped according to age, dwell time of the catheter, number of catheters inserted, and diameter of the SVC. Forty-two of the fifty-seven patients had had only right IJV (n =16) or right SCV (n = 26) catheters. There were no differences between these groups with respect to rates of pericatheter sleeve formation, thrombus formation, or BCV stenosis.

CONCLUSION

This study showed that even short-term catheters result in significantly high rates of pericatheter sleeve and thrombus formation which are two of the important causes of catheter malfunction. The IJV route is known to be much safer than the SCV route with respect to stenosis formation in the vein in which the catheter is inserted; however, the result showed no differences between the two routes with respect to frequencies of pericatheter sleeve formation, thrombus formation, and BCV stenosis. These findings remind us again that we should avoid unnecessary catheter insertion even for short-term in these chronically ill patients.

Catheter materials affect the incidence of late blood-borne catheter infection

BACKGROUND

Adherence of bacteria and subsequent catheter-related infections (CRI) are greatly enhanced by the fibrin sheath that develops on indwelling catheters. Since the infection rate of catheters without fibrin sheaths is low and the fibrin sheath mediates bacterial adherence, catheter material is not thought to affect the incidence of late catheter-related infection.

METHODS

A total of 276 rats had catheters placed in the right jugular vein with the proximal end buried subcutaneously to eliminate exit site infection. Rats were divided into two groups: silastic catheters (SC; n = 133) and polyurethane catheters (PC; n = 143). Injections of 1 x 10(8) CFU/mL of Staphylococcus epidermidis were given via the tail vein on either the day of surgery, day 0 (n = 53 SC, n = 51 PC), or on postoperative day 10 (n = 50 SC, n = 62 PC). Thirty animals from each group (SC, PC) received sterile saline injections on day 10 and served as controls. Animals were sacrificed on postinjection day 3. Catheters were removed via the chest and placed into trypticase soy broth. Broth was incubated at 37 degrees C for 48 h. Microscopy for the fibrin sheath was done on 20 randomly selected catheters (10/group). Data were compared using Fisher's exact test, with p < 0.05 considered significant.

RESULTS

Incidence of CRI was equal prior to the formation of the fibrin sheath, while CRI was significantly higher in silastic catheters in the presence of a fibrin sheath. Without a fibrin sheath (day 0), 8/53 silastic catheters and 3/51 polyurethane catheters were infected (p = NS). With a fibrin sheath (day 10), 31/50 silastic catheters were infected versus 20/62 polyurethane catheters (p < 0.05). Control catheters were all culture negative (30/group). With light microscopy, 20/20 catheters had fibrin sheaths at day 10 with no visible difference between silastic and polyurethane catheters.

CONCLUSION

Catheter material does affect the incidence of catheter-related infection even when catheters are coated with a fibrin sheath. This difference may relate to a difference in the fibrin sheath itself as it forms on different catheter materials.

Fibrin sheath enhances central venous catheter infection

OBJECTIVE

To determine whether fibrin-coated central venous catheters have a higher infection rate, and spawn more septic emboli, than uncoated catheters after exposure to bacteremia.

DESIGN

Animal study comparing catheter infection and blood cultures of fibrin-coated and uncoated catheters exposed to bacteremia.

SETTING

Animal laboratory.

SUBJECTS

Adult male Sprague-Dawley rats.

INTERVENTIONS

A total of 210 rats had catheters placed with the proximal end buried subcutaneously. Rats were divided into three groups: tail vein bacterial injection on day 0 (no fibrin group) or on day 10 (fibrin group), or no injection/saline injection (control, n = 40). Bacterial injections were 1 x 108 colony forming units of either Staphylococcus epidermidis (n = 100) or Enterobacter cloacae (n = 60). Animals were killed 3 days after injection. Blood cultures were obtained via cardiac puncture, and catheters were removed via the chest. Half of the catheter was rolled onto agar and the other half was placed in trypticase soy broth. Plates and broth were incubated at 37 degrees C for 48 hrs. The presence of >15 colonies on roll plates, or growth in broth, was accepted as a positive sign of infection. Microscopy was performed on day 20-10 catheters. Thirty animals without catheters had bacterial injections and underwent blood culture 3 days after injection.

MEASUREMENTS AND MAIN RESULTS

Catheter infection with S. epidermidis occurred in 32% of roll plates and 80% of broth from the fibrin group vs. 4% and 20% from the no fibrin group (p <.01 for each). Catheter infection with E. cloacae occurred in 50% of roll plates and 80% of broth from the fibrin group vs. 0% and 12% from the no fibrin group (p <.01 for each). Positive blood cultures occurred in 47 of 68 animals from the fibrin group vs. 8 of 68 from the no fibrin group (p <.01). Microscopy showed a fibrin sheath on 20 of 20 catheters. Without catheters, 30 of 30 blood cultures were negative.

CONCLUSION

The fibrin sheath significantly enhanced catheter-related infection and persistent bacteremia.

Reducing catheter-associated infections with silver-impregnated catheters in long-term therapy of children

Central venous long-term catheters offer reliable, large-lumen vascular access with high flow rates for delivery of nutrition or for cell-containing infusions and perfusions. Catheter-associated infections (CAI) pose the greatest threat to such vascular access, despite existing preventive measures. In this article one prospective and one retrospective study of CAI in pediatric therapy are presented. Study I: A retrospective investigation from 1990 through 1995 of 60 conventional long-term catheters in 50 patients. The total number of days in which the catheters were in place was 11,818. The calculated CAI incidence was 1 per 1,000 days of catheter insertion. Bacteriologically demonstrated CAI (identical isolate on the catheter tip and in a blood culture) occurred in three instances (5%). Five cases (8.3%) were diagnosed with a therapy-resistant, septic clinical picture. Study II: A prospective, randomized comparison of long-term silver-impregnated (Erlanger silver catheters) and control catheters (Quinton Instrument Co.) was made with 41 patients (20 with a silver catheter, 21 with a Quinton catheter). To date, the silver catheters have been distinguished by sterile bacteriological findings, whereas three cases of CAI have been demonstrated with the comparative catheters. One patient recently underwent intensive care after becoming unstable with signs of septic shock and demonstrable Pseudomonas aeruginosa, and two other patients manifested coagulase-negative staphylococci on the catheter tips. In three of nine control catheters an incidence of 1.18 per 1,000 days of indwelling catheters was found, whereas no CAI has occurred with the eight microbiologically tested silver catheters.

Intravenous glutamine or short-chain fatty acids reduce central venous catheter infection in a model of total parenteral nutrition

BACKGROUND/PURPOSE

In children receiving total parenteral nutrition (TPN) translocated enteric organisms are a possible cause of central venous catheter infection. The aim of this study was to determine the relationship between gut mucosal atrophy, bacterial translocation, and catheter sepsis in rats receiving TPN alone or supplemented with intravenous short chain fatty acids (SCFA) or glutamine.

METHODS

Mature Wistar rats were studied. Groups 2 to 5 had a central venous catheter inserted. Group 1 (n = 12) had enteral feeds only, group 2 (n = 14) had enteral feeds and intravenous saline, group 3 (n = 15) had TPN only, group 4 (n = 13) had TPN with SCFA, and group 5 (n = 15) had TPN with glutamine. At 1 week, blood, tissue, and catheter specimens were obtained for culture and mucosal morphometry.

RESULTS

Villus height and crypt depth were reduced significantly in group 3 compared with group 1 (P < .05). Glutamine and SCFA significantly ameliorated the mucosal atrophy. Significant bacterial translocation and catheter infection occurred in group 3. Reduced translocation with SCFA was not significant, but catheter infection was (P < .05). Glutamine significantly reduced translocation and catheter infection.

CONCLUSIONS

There is an association between bacterial translocation and central venous catheter infection. The risk of catheter infection is reduced by supplementing TPN with SCFA or glutamine.

Composition and formation of the sleeve enveloping a central venous catheter

PURPOSE

After catheterization, 42% to 100% of central venous catheters are surrounded by a "fibrin sleeve." This sleeve has been considered the cause of catheter-related infections, withdrawal occlusion, and pulmonary embolism. The reactions between the vein wall and the catheter were studied.

METHODS

A silicone catheter was placed in the anterior caval vein of 123 rats. After in situ fixation at scheduled intervals, the pathologic changes were studied on semi-serial histologic sections by means of light microscopy, transmission electron microscopy, and scanning electron microscopy (SEM). In 36 rats, the catheter was withdrawn immediately; in 72 rats, it was left in situ up to 6 months; and in 15 rats, the study was performed up to 10 months after withdrawal of a catheter that had remained in situ for 6 months.

RESULTS

In the group in which the catheter was withdrawn immediately, mural thrombi disappeared by day 7. In the group in which the catheter remained in situ, thrombi remained around the proximal portion of the catheter. This pericatheter thrombosis (PCT) was invaded by migrating and proliferating smooth muscle cells (SMCs), originating from an injured vein wall, and transformed from day 7 into a tissue composed predominantly of SMCs and collagen and covered by endothelial cells. Later, the number of cells decreased, and the relative amount of collagen increased. Up to 10 months after withdrawal of the catheter, the collapsed sleeve was still present within the vein.

CONCLUSION

The sleeve around a central venous catheter is not a fibrin sleeve, but a stable cellular-collagen tissue covered by endothelium. It is mainly formed by smooth muscle cells migrating from the injured vein wall into the early pericatheter thrombus.

Biological reactions to cerebrospinal fluid shunt devices: a review of the cellular pathology

OBJECTIVE

To understand the interaction between cerebrospinal fluid shunt components and the brain and other tissues.

METHODS

A systematic review of the medical literature directly pertaining to shunt complications, and that dealing with tissues' reactions to implants in general, was conducted.

RESULTS

Vascularized pedicles of glial tissue or choroid plexus grow into ventricular catheters, primarily as a mechanical phenomenon. Cellular debris or blood can cause dysfunction of valve components. Chronic inflammation, which is nonspecific, might contribute to degradation of the components.

CONCLUSION

Care must be taken to prevent early entry of debris or blood into the shunt system. Ventricular collapse onto the shunt must be avoided. Refinement of manufacturing methods or modification of shunt materials could reduce the susceptibility of shunts to infection and improve longevity of the apparatus.

Transvenous removal of fibrin sheaths from tunneled hemodialysis catheters

PURPOSE

Long-term hemodialysis catheters are prone to significant dysfunction due to fibrin accumulation around their tips. The authors assessed the efficacy of transvenous snare removal of fibrin to prolong function of these catheters.

PATIENTS AND METHODS

Twenty-four procedures were performed in 20 patients with tunneled hemodialysis central venous catheters. Technical success was gauged by venography and the ability to infuse and aspirate catheters. Durable efficacy was assessed by improvement in hemodialysis.

RESULTS

Twenty-two of 24 procedures were performed successfully. In two cases residual material remained despite repeated stripping. Mean preprocedure hemodialysis blood-liters processed per hour increased from 15.1 to 19.1 L/h in the first dialysis session after stripping, and blood flow rates of 300 mL/min or greater were restored. By the fifth dialysis session after stripping, the blood-liters processed per hour dropped to 15.9 L/h as catheter flow rates returned to unacceptable levels.

CONCLUSIONS

Percutaneous fibrin removal with a loop snare provides no durable benefit in improving function of failing hemodialysis catheters.

Histologic development of the sheath that forms around long-term implanted central venous catheters

BACKGROUND

Chronically implanted catheters often become covered with a thin, white adherent covering of tissue that has been referred to as a fibrin sheath. This tissue often interferes with catheter function.

METHODS

To chronicle the development of this sheath, rats were implanted with silicone rubber central venous catheters. Five rats were euthanized at 3,7, and 60 days postimplantation so that gross necropsy and histology could be performed on the catheterized vessels.

RESULTS

The coating that developed around the external portion of the catheter started as a dark red thrombus containing fibrin and progressed into vascularized, fibrous connective tissue.

CONCLUSIONS

The translucent to white sheath that forms around chronically implanted catheters is not composed of fibrin and is therefore not likely to be dissolved by fibrinolytic agents such as urokinase, streptokinase, or tissue plasminogen activator.

A prospective randomized double-blind trial of bolus urokinase in the treatment of established Hickman catheter sepsis in children

BACKGROUND

The incidence of Hickman catheter sepsis is 10% to 40%, with resultant catheter loss in one third of infections. Urokinase causes dissolution of colonized intracatheter fibrin thrombi and may improve salvage.

STUDY AIMS

To evaluate the efficacy of 12-hour-interval slow-push urokinase infusion in addition to standard antibiotic therapy in the treatment of catheter sepsis in a pediatric oncology population.

METHODS

A two-arm randomized double-blind trial was undertaken, with catheter salvage rate as the end point. Patients with Hickman catheter sepsis were randomized after culture data confirmed the diagnosis. The study drug was administered by a slow intravenous push and given at 12-hour intervals for a total of four doses. The catheters were aspirated after 1 hour.

RESULTS AND CONCLUSIONS

The trial was stopped after 41 patients were entered into the study; 18 patients received a placebo, and 23 received the urokinase. In the placebo group, six catheters were lost; in the urokinase group, eight were lost. The rate of bacterial clearance was equivalent for both. After administration of the study drug, each group had three episodes of fever and chills; two of these resulted in hypotension (one in each group). The authors conclude that slow-push urokinase infusion during established Hickman catheter sepsis does not result in improved catheter salvage or bacterial clearance. Slow intravenous push infusions in this setting may provoke hemodynamic instability even after initiation of antibiotics.