Effect of extrusion process melt temperature on polyurethane catheter surfaces

Determination of optimum process melt temperature of medical-grade polyurethane (PU) is an indispensable challenge witnessed during the catheter manufacturing process. This resin does not contain a uniform crystal structure but exists in an amorphous state. The lower shore hardness PU material, used in catheter manufacture, has just a “melt temperature range” instead of a definite melt temperature. This temperature plays a significant role in shaping the catheter surfaces, which directly interact with human tissues and cause health-care-associated issues. The objective of this work is to evaluate the effects of variations in the melt temperature during the extrusion process of medical catheters on their outer surfaces. Medical PU, Pellethane, was used for this study and 12 Fr (4.0?mm) catheters were manufactured with optimal validated parameters, excluding melt temperature. The manufactured catheters were examined under Optical Microscopy and Atomic Force Microscopy (AFM) for surface topography studies. Wettability studies were carried out using a Goniometer for evaluating the water contact angles. The effects of melt temperature on the surface roughness (R_a) and wettability of the catheter surfaces were analyzed through analysis of variance (ANOVA). The conclusion was that the process melt temperature variations have a significant effect on catheter R_a and its wettability characteristics.     

Catheter tip malposition after percutaneous placement of tunneled hemodialysis catheters

The percutaneous catheterization of central veins is increasingly used in nephrological practice as a temporary or permanent vascular access. The aim of our study was to present and to analyze episodes of catheter tip malposition during percutaneous tunneled hemodialysis catheter insertion in the large, unselected group of patients. All patients who underwent the procedure of catheter insertion in our department during year 2012 were analyzed retrospectively. One hundred four tunneled hemodialysis catheters were inserted in 101 patients. In 58 patients, the catheter was inserted at the initiation of hemodialysis therapy as the first access and in 46 the catheter was placed because of the failure of the existing one. In 68 patients, the catheter was inserted into the right internal jugular vein and in 20 patients into the left internal jugular vein (LIJV). Subclavian veins were used in five cases and femoral veins in 11 cases. Malposition of the catheter tips occurred in six patients. In all cases, the LIJV was cannulated. In two cases, the catheter tip malposition was in the right innominate vein and in four cases in the azygos vein. Our data demonstrate that with the blind insertion of tunneled hemodialysis catheters, the risk of catheter tip malposition is significantly higher with the left side insertion. As catheter insertion through the LIJV holds very high (30%) risk of the tip malposition, it should always be performed under the fluoroscopic control.     

Adhesion of two uropathogens to silicone and lubricious catheters: influence of pH,urea and creatinine

The adhesion of a hydrophilic Escherichia coli and a hydrophobic Staphylococcus epidermidis was significantly higher to silicone-coated latex than to a hydrophilic lubricious-coated catheter after 24 h incubation. Time-course studies showed a steady increase in viable E. coli adhesion to the hydrophilic catheter over 24 h. However, in contrast to thermodynamic modelling predictions, S. epidermidis adhered well to the hydrophilic catheter within 30–60 min. By 18 h the adherent S. epidermidis were non-viable, apparently demonstrating the presence of an unidentified antibacterial factor on this catheter. A range of creatinine concentrations had some effect on the adhesion. Bacterial binding was significantly higher in low urea concentrations (<200 mm) and was significantly affected by variation of pH from 3 to 9. There was some correlation between the suspending fluid surface tension, F ^Adh, and the experimental adhesion.     

Catheter‐related fungal endocarditis caused by Candida parapsilosis in a hemodialysis patient

Fungal endocarditis (FE) is commonly regarded as a rare but fatal disease. The incidence of infective endocarditis (IE) in hemodialysis (HD) patients is thought to be obviously higher than that in the general population. Moreover, IE occurs more likely in HD patients with catheters. With the increase of HD population and extensive use of catheters in HD patients, FE, as a special form of IE, may increase and bring new challenges to clinicians. We reported a case of FE associated with catheter infection in a 44‐year‐old woman on HD. The risk factors and treatment strategies of FE in HD patients were discussed.     

Three-dimensional converging-diverging Gaussian beam diffraction by a volume grating

The diffraction characteristics of a volume grating (VG) illuminated by a three-dimensional (3-D) converging-diverging Gaussian beam at conical incidence are investigated by applying 3-D finite-beam (FB) rigorous coupled-wave analysis (RCWA) based on the conventional 3-D RCWA in conjunction with two-dimensional plane-wave decomposition. The Gaussian beam is assumed to have an arbitrary incidence angle, an arbitrary azimuthal angle, and any linear polarization. The two cases with linear polarizations of the central beam of the Gaussian (E perpendicular K and H perpendicular K) are investigated. The diffraction efficiencies and the diffracted beam profiles for both unslanted VGs and slanted VGs (designed for substrate-mode optical interconnects) are presented. In general, the diffraction efficiencies of a converging-diverging spherical Gaussian beam diffracted by both unslanted VGs and slanted VGs increase and approach the central-beam results as the refractive-index modulation increases.     

Efficacy of Tissue Plasminogen Activator for Thrombolysis in Central Venous Dialysis Catheters

Background:  Low blood flow is a frequent complication of central‐vein (CV) dialysis catheters. Since thrombotic occlusion accounts for many cases of reduced blood flow, it is common practice to administer empiric thrombolytic therapy in an attempt to restore catheter patency and improve function.
Methods:  We prepared tissue plasminogen activator (tPA) from 50 mg lyophilized powder, which was diluted (1 mg/mL) in sterile water for injection. A volume of 1 mL was frozen in 3 cc polystyrene syringes at −20 °C and thawed at room temperature when needed. tPA was then administered into the arterial and venous ports of the central venous catheter in a volume equal to the manufacturer's stated luminal volume and was allowed to dwell for 30 minutes.
Results:  tPA was administered 62 times in 25 patients with 30 catheters (11 Tesio, 17 PermCath, 2 Shiley) for treatment of low blood flow (pump speed < 250 mL/min). Complete restoration of patency was achieved in 23 episodes (mean blood flow pre‐tPA 130 mL/min; post‐tPA 320 mL/min); partial restoration of patency was achieved in 20 episodes (mean blood flow pre‐tPA 69 mL/min; post‐tPA 233 mL/min). tPA was just as likely to be effective in patients with complete catheter occlusion (i.e., no blood flow) as it was when some initial blood flow was present. Nineteen episodes failed to respond to tPA. These episodes occurred in 13 catheters, 12 of which ultimately underwent radiologic evaluation; an extraluminal cause for low blood flow was found in all 12 catheters (6 malpositioned, 6 fibrin sheaths).
Conclusions:  tPA at a dose of 1 mg/mL is effective for restoring patency in CV dialysis catheters. Failure to respond to tPA strongly suggests an extraluminal cause of catheter malfunction.     

A rare cause of abdominal pain: Catheter in the middle hepatic vein

Hemodialysis catheters are vital for chronic renal failure patients. Permanent tunneled dialysis catheters may be inserted through the jugular, subclavian, and femoral veins. In this paper, we aimed to present the computed tomography findings of a chronic renal failure patient who had referred our clinic with abdominal pain and dyspnea symptoms. This patient had a formerly inserted hemodialysis catheter for chronic renal failure and her catheter was found to be extending towards the middle hepatic vein with the tip leaning onto the parenchyma. Hemodialysis catheters can provide instant vascular access and can also be used for the consecutive procedures. Permanent hemodialysis catheters are ideal for long‐term use when placing an arteriovenous fistula is contraindicated or is no longer possible under conditions like advanced heart failure, peripheral artery disease or short life expectancy. The internal jugular, subclavian, the femoral veins, and the inferior vena cava can be used for catheter insertion. The tip of the catheters inserted in the neck or the thorax must extend to the vena cava superior. Catheter malposition may both lead to fatal outcomes and ineffective dialysis. It is important to obtain chest X‐rays after the procedure, particularly to detect catheter malposition.     

Air-Bubble Method of Locking Central-Vein Catheters for Prevention of Hub Colonization: A Pilot Study

Background: The major source of catheter‐associated bacteremia is contamination of the catheter hub during connection–disconnection procedures. A new method of catheter locking has been developed wherein anticoagulant is injected first, followed by a 0.1‐mL air bubble and 0.9 mL of bactericidal solution. The anticoagulant is then located at the catheter tip and the bactericidal solution is located at the catheter hub. The air bubble prevents mixing of the two solutions. The bactericidal solution was acidified concentrated saline (ACS). The 27% saline solution has a pH of 2.0. ACS was chosen because it is theoretically harmless if injected in the amount used to lock the catheter lumens. The goals of this pilot study were to determine whether the new method of catheter locking is easy to perform with available syringes and whether eventual injection of the experimental solution is well tolerated. Methods: Ten patients were randomly assigned, either to heparin lock (5 patients, 62 treatments) or air‐bubble method (5 patients, 56 treatments). In the control group, the catheters were locked with heparin, 5000 U/mL. In the experimental group, the catheters were locked with heparin, air bubble, and ACS. Altogether, the lumens were overfilled by 0.2 mL. Results: Compared to the routine method, the experimental method required a 1‐ to 2‐min‐longer procedure time. There were no errors in proper sequence of injections into the lumina. There were no episodes of bacteremia related to hub contamination in either group. In the air‐bubble group, there was one case of bacteremia associated with purulent drainage from the exit and the same organism in both cultures. In three instances in each group, the locking solution could not be aspirated and was injected without any subjective symptoms or objective signs. Conclusion: We conclude that the air‐bubble method of locking central‐vein catheters is easy to perform. In three instances of air‐bubble and ACS injection, there were no adverse effects. A full‐scale prospective randomized study is feasible and warranted.     

Outbreak of nonfermentative Gram‐negative bacteria (Ralstonia pickettii and Stenotrophomonas maltophilia) in a hemodialysis center

We report a case series of seven patients with nonfermentative Gram‐negative bacteria infections in a single dialysis center; four patients with Ralstonia pickettii and three patients with Stenotrophomonas maltophilia. Two of the seven patients were admitted to hospital for intravenous antibiotic treatment, while the rest were treated with oral antibiotics at home. Both the admitted patients had temporary vascular catheter infections from the aforementioned pathogens. We conclude that the outbreak is due to colonization of treated reverse osmosis water, presumably through contamination via polluted filters and compounded by the usage of reprocessed dialysers in the dialysis center. This is especially relevant because contaminated treated water is directly introduced into the blood compartment of the dialysers during reprocessing. In addition, there seems to be a propensity for both organisms to cause prolonged febrile reactions in patients with temporary vascular catheters, likely through the early development of biofilm. Intensification of general sterilization procedures, servicing and replacement of old decrepit components of the water treatment system and temporary cessation of dialyser reuse practice seem to have halted the outbreak. Due to the virulent nature and difficult resistant profile of nonfermentative Gram‐negative bacteria, we strongly recommend meticulous vigilance in the surveillance of culture isolates in routine microbiological specimens from dialysis centers, especially if there is a senescent water treatment system and a practice of reprocessing dialysers.     

Chronic hepatitis C infection: Prevalance and effect on clinical status of hemodialysis patients in our center

Purpose:  Contamination of catheter hub connectors is known to cause catheter‐related blood stream infections in patients undergoing hemodialysis via central venous catheters (CVC). The effectiveness of cleansing the hub with an antimicrobial agent was assessed by culturing the surface of the hub following sanitation. Methods:  The CVC hub connectors of 24 patients were sanitized using the standard hospital protocol of aseptically swabbing the connectors with a solution of bleach or Betadine, and then bathing the hub in sterile gauze soaked with the antimicrobial solution for 5 minutes. The exterior surface of the hub was then cultured for a broad spectrum of microorganisms. Patients were monitored for exit site infection, tunnel infection, and septicemia. In the laboratory, sterile hubs were inoculated with E. coli , staph. aureus neg ., and yeast. Hubs were then immersed in Betadine for 5, 10, or 30 min. and cultures were taken. Results:  Positive cultures were obtained from the hubs of 17 of the 24 patients. Seven (7) of the patients with positive results developed bacteremia from the cultured organism within 7 weeks. Positive cultures were obtained from 50% of inoculated lab samples after 5 min, 10% after 15 min, and 0% after 30 min. of immersion sanitation. Conclusions:  The techniques for cleansing CVC hubs should be revisited.     

Tissue plasminogen activator as a hemodialysis catheter locking solution

Tunneled hemodialysis catheters require a "locking solution" between treatments to prevent catheter thrombosis. Heparin locks can be unsafe in patients with life-threatening bleeding diathesis because of unintentional anticoagulation. This study was designed to define the hematologic consequences of using tissue plasminogen activator (t-PA) as an alternative locking solution after heparin-free hemodialysis (HF-HD). Following HF-HD, t-PA 2 mg was instilled into each lumen of the dialysis catheter in 10 patients. Euglobulin clot lysis time (ECLT), fibrinogen, D-dimer, and fibrin degradation products were measured during the last hour of dialysis, and repeated 15 and 30 minutes after catheter locking. Dialysis catheter performance was reassessed at the time of the next hemodialysis. Fibrinogen, D-dimer, and fibrin degradation products were elevated at all time points, but did not change after t-PA. ECLT decreased significantly from baseline 15 minutes after catheter locking (217+/-64 vs. 132+/-75 min, p=0.016). ECLT values had returned to baseline (202+/-56 minutes) by 30 minutes. No episodes of bleeding or catheter thrombosis occurred, and catheter performance did not deteriorate. A 2 mg t-PA locking solution preserved dialysis catheter performance. ECLT decreased at 15 minutes, but normalized by 30 minutes, and did not enter the range in which bleeding would be likely. No clinical events were seen during this transient increase in systemic fibrinolysis.     

Prevention of Damage to Cuffed Catheters

Cuffed catheters, although not ideal for long-term use, are now used more frequently due to an increase in the aging population, in whom the vessels are not suitable for either arteriovenous fistulas or polytetrafluoroethylene (PTFE) grafts. Infections and thrombosis remain the major causes for removal or change of catheters. We recently identified eight catheter defects that required replacement of catheters. Of these, two were due to patient negligence: one catheter was accidentally severed while the patient was shaving; the other was snipped during a haircut. One was believed to have a manufacturing defect. One catheter sustained needle-prick damage near the hub while irrigating the catheter. Two catheters were lost due to needle pricks during skin closure, and one catheter sustained similar damage while fixing the suture wing to the skin. The other two were damaged by suture material slicing through the lumen of the catheter as it expanded due to increased blood flow during repeated dialyses. Importantly, several of these injuries to the catheters were not immediately obvious and were detected only after repeated use of the catheters. Delayed bleeding of cuffed catheters necessitating change or removal has not been reported. Such bleeding may be due to manufacturing defects, patient carelessness, or iatrogenic causes. Avoiding the use of sutures can minimize the latter. Skin closure strips and a double transparent dressing may serve the same purposes, such as securing the catheter and aiding wound healing. In addition, these dressings have the added advantage of being waterproof, bacteria-proof, and cost effective.     

Low dose heparin lock (1000 U/mL) maintains tunnelled hemodialysis catheter patency when compared with high dose heparin (5000 U/mL): A randomised controlled trial

Introduction Heparin is commonly used after hemodialysis treatments as a locking solution to prevent catheter thrombosis. The comparative efficacy and safety of different heparin concentrations to maintain catheter patency has been previously reported in retrospective studies. We conducted a prospective, randomised, controlled study of 1000 U/mL heparin (low dose) versus 5000 U/mL heparin (high dose) locking solution to maintain patency of tunnelled catheters. Methods One hundred patients receiving chronic, unit‐based hemodialysis with newly placed tunnelled hemodialysis catheters (less than 1 week) were randomly assigned to either a low dose (n = 48) or high dose heparin (n=52). The primary intention‐to‐treat analysis examined time to malfunction in both groups over a 90 day period. A secondary analysis compared baseline patient characteristics in relation to catheter malfunction. Findings Overall rate of catheter patency loss was 32% of catheters by 90 days. There was no significant difference in time to malfunction of catheters locked with low dose or high dose heparin (P = 0.5770). Time to catheter malfunction was not associated with diabetic, hypertensive or smoking status. There was no difference in mean delivered blood flow rate, venous and arterial pressure, and dialysis adequacy between low dose and high dose groups. No patient suffered a hemorrhagic complication requiring hospitalisation during the study period. Discussion Low dose heparin is adequate to maintain tunnelled hemodialysis catheter patency when compared with high dose heparin. The study also suggests that there is no relationship between catheter malfunction and diabetic, hypertensive or smoking status.     

Efficacy of preventing hemodialysis catheter infections with citrate lock

Prevalent use of tunneled dialysis catheters can reach 30%. Infection remains the most serious catheter‐related problem. Catheter locks are increasingly used for prevention, but are not yet recommended either by the Food and Drug Association or European Medicines Agency, on the basis of increasing bacterial resistance or lock toxicity. The aim was to test safety and effectiveness of citrate. A prospective, interventional study was conducted to assess the safety and efficacy of a 30% citrate lock in preventing catheter‐related bacteremia (CRB). A total of 157 prevalent tunneled catheters were locked with citrate and prospectively followed during a 1‐year period. The primary endpoint was first CRB diagnosed according to two of the diagnostic criteria for Catheter Infection of Centers for Disease Control and Prevention (CDC), namely definite and probable infection. The CDC criterion of possible but not proved infection was not considered. This citrate lock cohort (n = 157) had 10 episodes of CRB. We observed 0.49 CRB episodes/1000 patient‐days and the mean infection‐free catheter day was 130.6 ± 100.9. No clinically relevant adverse events were observed. No proved tunnel or exit site infection was observed and no patients died because of CRB. Catheter obstruction episodes were reported on 69 occasions out of 14 catheters. These results were compared with an historical cohort from a previous study of catheter locking with low‐dose gentamicin and did not show significant difference in efficacy. Citrate lock is effective in preventing CRB. No toxicity was observed. The use of citrate lock may have advantages over antibiotic locks: No reported bacterial resistance, lower industrial cost, and less manipulation.     

A new titanium fiber mesh-cuffed peritoneal dialysis catheter: An experimental animal study

CAPD catheters are associated with infectious complications. To solve this problem, we developed a new catheter. In our design, sintered titanium fiber mesh material replaced the Dacron cuffs, as used in standard Tenckhoff catheters. The purpose of the current study was to compare the tissue response to new titanium-cuffed vs. Dacron-cuffed catheters. Experimental and standard Tenckhoff catheters were inserted intraperiotoneally in 12 goats, using a so-called two-stage surgical technique. In the first surgical session, the catheters were implanted. However, the percutaneous part of the catheter was buried subcutaneous. After 3-5 weeks, the percutaneous part of the catheter was exteriorized. After 14 weeks of implantation, all implants with surrounding tissue were retrieved and prepared for histological evaluation. Subsequently, we quantified: the characteristics of the fibrous tissue capsule surrounding the cuffs, the tissue inside the cuff porosity, and the epidermal downgrowth. Histologic and histomorphometric evaluation showed that titanium mesh evoked a lesser inflammatory response inside the cuff porosity compared with Dacron cuffs. Besides, the fibrous tissue capsule surrounding the titanium cuffs was significantly thinner. Supported by the obtained results, we conclude that the use of titanium fiber mesh has a great potential for application in percutaneous devices.     

Angular sensitivities of volume gratings for substrate-mode optical interconnects

The angular sensitivities of slanted volume gratings (VGs) illuminated by three-dimensional (3-D) converging-diverging spherical Gaussian beams for substrate-mode optical interconnects in microelectronics are analyzed by application of 3-D finite-beam rigorous coupled-wave analysis. Angular misalignments about the z, y, and x axes that correspond to yaw, pitch, and roll misalignments resulting from manufacturing tolerances of chips are investigated. Two cases of linear polarization of the central beam of the Gaussian are considered: E perpendicular K and H perpendicular K, where K is the grating vector. From worst-case manufacturing tolerances, the ranges of yaw, pitch, and roll misalignment angles are alpha = +/-1.17 degrees, beta= +/-3.04 degrees, and gamma = +/-3.04 degrees, respectively. Based on these ranges of misalignment angles, the decreases of diffraction efficiencies for slanted VGs that are due to both the yaw and the roll misalignments are relatively small. However, the efficiency of substrate-mode optical interconnects achieved by slanted VGs could be reduced by 61.04% for E perpendicular K polarization and by 58.63% for H perpendicular K polarization because of the pitch misalignment. Thus the performance of a VG optical interconnect is most sensitive to pitch misalignment.     

Hemothorax caused by replacement of hemodialysis catheter: A case report

Central venous catheters (CVC) are widely used in clinics to gain vascular access, but the risk and prevalence of catheter‐related complications remains a serious issue. We report a long‐term dialysis catheter accidentally inserted into the mediastinum via the right jugular vein in a hemodialysis patient. We also review complications associated with vascular catheterization and propose immediate therapeutic interventions for such cases.     

Antibacterial coatings on haemodialysis catheters by photochemical deposition of silver nanoparticles

Antibacterial coatings on catheters for acute dialysis were obtained by an innovative and patented silver deposition technique based on the photo-reduction of the silver solution on the surface of catheter, with consequent formation of antibacterial silver nanoparticles. Aim of this work is the structural and morphological characterization of these medical devices in order to analyze the distribution and the size of clusters on the polymeric surface, and to verify the antibacterial capability of the devices treated by this technique against bacterial proliferation. The structure and morphology of the silver nanoparticles were investigated by using scanning and transmission electron microscopy. The antimicrobial capability of the catheters after silver deposition was confirmed by antibacterial tests with Escherichia coli. Both scanning electron microscopy analysis and antibacterial tests were performed also after washing catheters for 30 days in deionized water at 37°C, relating these data to thermogravimetric analysis and to energy dispersive spectroscopy, in order to check the resistance of coating and its antimicrobial capability after the maximum time of life of these devices.     

Comparison of side hole versus non side hole high flow hemodialysis catheters

Current literature suggests that side holes may be detrimental to dialysis catheter performance. Today, these catheters are primarily available with side holes. The purpose of this study was to compare flow rates, infection rate, and survival of side hole vs. non side hole hemodialysis catheters. Over a 16-month period patients were arbitrarily assigned to either a 14.5 F MAHURKAR MAXID cuffed dual lumen tunneled catheter with side holes or a 14.5 F MAHURKAR MAXID cuffed dual lumen tunneled catheter without side holes ("non side hole catheters"). We performed a retrospective analysis of catheter flow rates, patency, catheter survival, and catheter-related infections. Information was gathered for the life of the catheter or up to 28 weeks. A total of 54 patients were enrolled in the study. Thirty-seven of 54 (68%) patients received a catheter with side holes for a total of 3,930 catheter days and 17/54 (32%) received a similar catheter without side holes for a total of 2,188 catheter days. Catheter infection necessitating removal of the catheter occurred in 10/37 catheters with side holes and 1/17 without side holes. Infection rates per 1,000 catheter days were 2.545 with side holes and 0.254 without side holes (p<0.001). Slightly improved catheter survival (p<0.05) was recorded with the non side hole catheters. No insertion complication (e.g., air embolization, bleeding, or kinking) occurred with either catheter. One catheter without side holes had to be repositioned 5 days after insertion because of poor flows. No significant difference was recorded in mean blood flow rates between the catheters. Results indicate reduced catheter infection rate in hemodialysis patients with the use of non side hole dual lumen tunneled cuffed catheters.