Medical Catheter Research Articles

In vivo solid-phase microextraction for monitoring intravenous concentrations of drugs and metabolites

This protocol for in vivo solid-phase microextraction (SPME) can be used to monitor and quantify intravenous concentrations of drugs and metabolites without the need to withdraw a blood sample for analysis. The SPME probe is inserted directly into a peripheral vein of a living animal through a standard medical catheter, and extraction occurs typically over 2-5 min. After extraction, the analytes are removed from the sorbent and analyzed by, for example, liquid chromatography-tandem mass spectrometry. It has been validated in comparison with conventional blood analysis, and we describe here the in vitro experiments typically conducted during method development. The new-generation biocompatible SPME probes are designed specifically for extraction of semi-volatiles and nonvolatiles directly from aqueous samples and can be steam sterilized. Sorbents are coated on fine-gauge surgical steel wire (200-μm diameter), which is more rugged and biocompatible than conventional fibers (100-μm fused silica fiber). They incorporate a binding agent that resists fouling by the biological matrix and does not cause an immune response in the experimental animal. The sorbents used (coating thickness of ∼50 μm) are selected for their affinity for the types of small molecules of interest. The procedure is illustrated by the analysis of benzodiazepines with polypyrrole-coated wires inserted into peripheral blood vessels of beagles, although it can be adapted for use in smaller animals. The in vivo sampling can require as little as 1 min, in which case the entire procedure from sampling to instrumental analysis can take as little as 30 min.

Life at the Frontier

Life at the Frontier

Infection prevention in the intensive care unit: Review of the recent literature on the management of invasive devices

Over the last 5 y, clinical trials investigating products, procedures, and treatments aimed at preventing infections in the intensive care unit have been described. The findings of these studies appear to confirm the effectiveness of certain preventive procedures. With regard to ventilator-associated pneumonia, the efficacies of decontamination of the oral cavity, continuous suction of subglottic secretions, positioning of the patient, selective decontamination of the digestive tract, and (for higher-risk patients) endotracheal tubes coated with silver, have been demonstrated. Medicated catheters and chlorhexidine-based dressings have been found useful for catheter-related bloodstream infections, and medical catheters have also been shown to be efficacious against urinary tract infections. All these procedures can be incorporated into departmental protocols for the prevention of nosocomial infections in the intensive care unit.

The development of an antimicrobial EVD catheter to protect against multi-resistant hospital “superbugs”

Background External Ventricular Drainage (EVD) infections are a serious complication, and the period of risk extends until the device is removed. The causative bacteria of EVD and shunt infections are similar but there are more multi – resistant strains such as MRSA and gram negative bacteria in EVD infections, particularly when the patient is in intensive care. To counter this, we have development an antimicrobial EVD catheter with a broad spectrum to protect against these multi-resistant bacteria. Thus, the aim of this study was to evaluate the antimicrobial activity of this catheter against multiresistant Staphylococcus epidermidis, MRSA, and gram negatives using clinically predictive in vitro tests. Materials and methods Medical grade silicone catheter tubing (Codman) was impregnated with antimicrobials: 1% triclosan, 1% trimethoprim and 0.2% rifampicin respectively. Three methods were used to evaluate the antimicrobial activity of the catheter. The Serial Plate Transfer Test (SPTT) is a screening test for duration of antimicrobial activity and to monitor resistance. Impregnated catheter segments were placed onto agar plates seeded with bacteria and incubated. Segments were removed daily and placed on fresh plates and reincubated. The inhibition zone was measured across the short axis. This was repeated until no inhibition zones were seen. The time taken to kill 100% of bacteria attached to catheter segments (tK100), was determined by first coating the catheter segments with a protein conditioning film, then allowing the bacteria to adhere to plain and antimicrobial catheter segments and incubating them. Samples were retrieved daily, sonicated to remove the adherent bacteria, and the sonicate cultured quantitatively to detect bacterial growth. Thirdly, a simulated in vitro model was used to determine the ability of the antimicrobial catheter to resist successive bacterial challenges every 14 days under constant perfusion, designed to mimic the CSF flow. Results

A Physicochemical Approach to Render Antibacterial Surfaces on Plasma‐Treated Medical‐Grade PVC: Irgasan Coating

AbstractA multistep physicochemical approach was adopted to develop a novel surface active antibacterial medical‐grade polyvinyl chloride (PVC). This was accomplished through surface activation via diffuse coplanar surface barrier discharge plasma in air at ambient temperature and pressure, followed by radical graft copolymerization of acrylic acid onto the surface via grafting‐from pathway to yield a well‐defined high density brush. Irgasan as a potent biocide was then coated onto the functionalized surface to impart antimicrobial properties. Contact angle measurements showed an improved hydrophilicity upon multistep modifications. Alterations in surface free energy values were tracked through various known models. The equilibrium water absorption test corroborated the contact angle analysis. Scanning electron microscopy revealed etched features on the plasma treated sample as well as a brush‐like pattern on the graft copolymerized surface. Surface chemistry was explored by Attenuated Total Reflectance Fourier Transform Infrared (ATR‐FTIR) and X‐ray Photoelectron Spectroscopy (XPS), which confirmed the presence of irgasan non‐covalently anchored onto the surface. An excellent bacteriostatic performance was exhibited by the irgasan coated sample using the agar diffusion test method against two potentially pathogenic gram‐negative and particularly gram‐positive bacterial strains implying a facile release of the antibacterial agent. However, in vitro bacterial adhesion and biofilm formation assays indicated incapability of irgasan in hindering the adherence after 24 h incubation. Nevertheless, the plasma treated and graft copolymerized samples were appreciably effective to diminish the adherence of gram‐negative strain. Wettability and surface configuration of the substrate, besides bacteria structural characteristics, were established to be crucial factors in the adhesion phenomenon. The irgasan coated medical‐grade PVC was suggested to be suited for use in disposable medical catheters of dependable antimicrobial performance.magnified image

Abstract No. 325: Use of the Elcam Medical catheter tip locator system (the CatFinder) to determine catheter tip location in 131 patients

Abstract No. 325: Use of the Elcam Medical catheter tip locator system (the CatFinder) to determine catheter tip location in 131 patients

Preparation and in-vitro Antibacterial Evaluation of Electroless Silver Coated Polymers.

Long-term use of indwelling medical catheters has often been hindered by catheter-associated nosocomial infections. In this study the effectiveness of silver coating of polystyrene and polyethylene polymers was investigated. Polymer pieces of 2 cm(2) each were coated with a thin layer of silver using electroless plating technique. Silver-coated polymers were challenged with cultures of four different microorganisms known for their involvement in nosocomial infections in both solid and broth media. The tested bacteria included Staphylococcus aureus, Staphylococcus epidermidis, Escherichia coli and Pseudomonas aeruginosa. Silver release from the coated polymers was 2-5 μg/cm(2) which was confirmed by chemical and biological methods. The silver coating thickness ranged between 20-450 nm. P. aeruginosa and S. aureus were the most adherent bacteria to polystyrene sheets while E. coli showed minimum adherence effect. The survival rate of different bacteria after 80 min in a time course experiment tended to dominate E. coli as the most sensitive bacteria to the effect of silver with zero survival rate while around 4% of P. aeruginosa were detected after same period. Silver coating of indwelling polymers by electroless technique seems promising in combating nosocomial infections due to long-term catheterization.

Parenteral Lipid Emulsion Induces Germination ofCandida albicansand Increases Biofilm Formation on Medical Catheter Surfaces

The administration of parenteral nutrition, including lipid emulsion (LE), to patients via medical catheters is an unexplained risk factor for the development of candidemia. Germination and biofilm formation are recognized virulence determinants of Candida albicans. No studies have addressed the effect of LE on candidal biofilm production. In this study, we investigated the effect of LE on candidal germination and its ability to form biofilm on medical catheter material. C. albicans strain SC-5314 was grown in standard growth medium in the presence or absence a commercially available LE. Biofilms grown on silicone-elastomer catheter discs in these media were compared for mass by dry weight measurements. Biofilm morphology was analyzed by scanning electron microscopy and confocal laser microscopy. The effect of LE on C. albicans germination and growth was evaluated microscopically and by determination of colony-forming units, respectively. Addition of LE to standard growth medium increased C. albicans biofilm production and resulted in observed changes in biofilm morphology and architecture. Furthermore, LE induced germination and supported the growth of C. albicans. LE-inducible candidal virulence determinants, such as germination and enhanced biofilm production, may help to explain the increased risk of candidemia in patients receiving LE via medical catheters.

Impact of wastewater fouling on contact angle

Capillary dependent systems are highly influenced by surface fouling and may degrade as material surface properties change. In anticipation of a spacecraft microgravity fluids management system exposed to highly variable wetting conditions, the impact of urine wastewater fouling on capillary contact angle was examined. The results indicate that, in general, surface fouling can decrease the contact angle when crystalline structures or biofilms form. Small crystalline growth on the order of 10 μm can lower advancing contact angles θadv by approximately 30°, while biofilm growth can lower it by approximately 15°. Vacuum drying of fouled surfaces increased θadv by about 8°, and defects greater in height than 5% of the capillary length increased θadv by approximately 30°. These trends may indicate that promotion of wastewater fouling may improve the performance of capillary dependent fluids management systems. These results may also influence terrestrial technologies, including medical catheters and sustainable wastewater treatment systems exposed to wastewater fouling.

Improving Maneuverability and Tactile Feedback in Medical Catheters by Optimizing the Valve Toward Minimal Friction

A new extended hemostasis valve for sheaths is presented, with minimized stick-slip behavior to be used in (heart) catheterization procedures during long interventions (3–6 h). The invented extension to this existing sheath bypasses the silicone rubber sealing (hemostasis valve) and replaces it with a dedicated seal with the two functions separated: (1) sealing around the catheter being used and (2) closing the sheath when the catheter is removed (valve function). Measurements have been performed on the current and the invented seals, showing that the axial friction force is reduced, with a factor of 6.4, from 1.4 N to 0.22 N.

Bending Fatigue Properties of a Superelastic Thin Tube and a High-Elastic Thin Wire of TiNi Alloy

Experiments were conducted to investigate the deformation behaviors and fatigue properties of a superelastic thin tube (SE-tube) and a high-elastic thin wire (HE-wire) of TiNi alloy under conditions of pulsating-plane, alternating-plane and rotating bending. The main results obtained are summarized as follows. (1) The stress-strain curve of the SE-tube in tension describes a superelastic hysteresis loop with an elastic modulus of 35 GPa. It is thus suited for use as a medical catheter tube with flexibility and shape recovery. The stress-strain curve of the HE-wire stays close to a straight line up to a strain of 4% and a stress of 1500 MPa with an elastic modulus of 50 GPa, and is suited for use as a medical guide wire with flexibility, high pushability and a good torque transmission performance. (2) With respect to fatigue, the SE-tube and the HE-wire in air both have a longer life in pulsating-plane than in alternating-plane and rotating bending, whereas the difference in fatigue life between alternating-plane and rotating bending is small. The relationship between the maximum bending strain and the number of cycles to failure in the region of low-cycle fatigue can be expressed by a power function for each kind of bending fatigue. The fatigue life in the body is longer than that obtained in air. (3) The maximum bending strain at the fatigue limit of the SE-tube is 0.8%–1.0% which is close to the starting strain of the stress-induced martensitic transformation. The maximum bending strain at the fatigue limit of the HE-wire is 0.7%–0.8%.

An Adaptive Meshless Method for Analyzing Large Mechanical Deformation and Contacts

Design for manufacturing of equipment (that handles deformable objects) and disposable medical devices (such as medical needles, optic fibers, and catheters for inserting into the human body) involves solving mechanical contact problems. Unlike rigid component manufacturing, which has been relatively well established, the handling of deformable bodies remains a challenging research. This paper offers an adaptive meshless method (MLM) for solving mechanical contact problems, which automatically insert additional nodes into large error regions identified in terms of mechanical stresses. This adaptive MLM employs a sliding line algorithm with penalty method to handle contact constraints. The method does not rely on small displacement assumptions; thus, it can solve nonlinear contact problems with large deformation. We validate the method by comparing results against those computed by using a commercial FEM software and analytical solution for two different situations, namely, large deformation and contact. Four practical applications are illustrated: large deflection of a compliant finger, mechanical contact, snap-fit assembly, and surgical needle insertion.

Numerical evaluation method for catheter prototypes using photo‐elastic stress analysis on patient‐specific vascular model

To date, no quantitative analysis has been developed to evaluate catheter performance inside the vascular lumen. An evaluation system for endovascular tools was built with a polyurethane elastomer vascular model inside a polariscope and a catheter driving system. This robotic system reproduced a catheter insertion trajectory inside the vascular model, using a surgical catheter and three catheter prototypes used for motion capture on endovascular surgery simulation. Birefringence is produced by photo-elastic characteristics of the polyurethane elastomer when the material is submitted external stress. The birefringence produced by the catheter on the vascular model wall was recorded and represented numerically by the correlation between consecutive frames of the registered video. Correlation values between frames showed that the performance of the prototypes was lower than that of the medical use catheter. The performance of prototypes was reduced by microcoils on their tips. This methodology opens new options to evaluate medical catheters and physicians skills. opyright

Analysis of deformations and stresses in flat rolling of wire

Flat rolling of wire is an industrial process used to manufacture electrical flat wire, medical catheters, springs and piston segments, among other products. This paper presents a 3D numerical analysis of the contact stress distributions prevailing in the roll-wire contact zone, as well as of residual stresses in the resulting flat wire, as a function of the deformation inhomogeneity induced in the material. Three different patterns in the contact pressure are clearly distinguished and discussed. As in slab-rolling process, a generalized parameter H* is proposed to quantify the deformation inhomogeneity in wire rolling. This parameter allows the characterization and prediction of the morphology of the contact and residual stress distributions.

Fabrication of a spiral type magnetic micromachine for trailing a wire

A magnetic micromachine capable of trailing a wire was fabricated. The micromachine was constructed of a permanent magnet, a copper tube, and a spiral shape made of a tungsten wire. The magnet was magnetized to the diametrical direction. When a rotational magnetic field was applied, the machine rotated and moved in a silicone oil. It was experimentally found that the blade angle of the machine that produced the largest thrust force was 45/spl deg/ . The micromachine was able to trail a wire in a narrow waterway simulating a blood vessel. These results show that the magnetic micromachine has great potential for navigating medical catheters.

Biocidal nanosol coatings

The inclusion of biocidal compounds into modified silica matrices using the sol-gel technique offers new interesting prospects for antimicrobial coatings with controlled release effects. The coatings are well suited for the functionalisation of flexible supports such as paper, textiles and polymer foils as they exhibit good adhesion and improved mechanical properties. It is possible to combine and coimmobilise different biocidal components to expand the antimicrobial efficiency. In the simplest case, modified silica coatings with immobilised boric acid can be used for the protection of wood against biological degradation. Moreover, silica coatings with embedded nanoparticular silver combined with organic biocidal compounds efficiently decrease the survival rate of different bacteria on textiles and medical catheters. Finally, novel types of antimicrobial nanosol coatings with volatile biocidal compounds (VBCs) are presented.

Miniaturization of a biomedical gas sensor

In a previous study, we concluded that a conductivity based PCO2 sensor is an attractive solution for early detection of ischemia and presented two design geometries. For organ surface measurements, the planar design was suitable but it was difficult to insert the sensor into the tissue. A cylindrical design solution was favored for insertion due to the large membrane contact area and easy placement in a medical catheter. Since the previous cylindrical prototype was large and could damage the tissue, a more miniaturized sensor was needed. In the current paper, we present a miniaturized sensor with an outer diameter of 1 mm. The applied technology for manufacturing the sensor was a combination of mechanical turning, excimer laser drilling and conventional molding technique. The materials applied were PEEK (polyetherether ketone), PI (polyimide) with gold layers and polysiloxane. The membrane had to be gas permeable while acting as a barrier for ion transport, and was made of polysiloxane and had a thickness of 100–150 µm. The miniaturized sensor was tested for calibration, response time, drifting and pressure sensitivity. The results show that the miniaturized PCO2 sensor is capable of rapid and stable measurements both in vitro and ex vivo. The result from this study will be applied for the industrial manufacturing of such a biomedical sensor as a clinical product.

Non-contact ultrasonic inspection of medical catheters for polymeric bond defects

A non-contact, laser-optic based laser ultrasonic technique referred to as the thermo-acousto-photonic non-destructive evaluation (TAP-NDE) was employed to investigate bond integrity and localized stiffening due to an attached wire stent on small diameter polymeric catheters. Laser-generated interrogating ultrasonic dispersive waves in the catheter were acquired using a fiber-tip interferometer (FTI) running on a HeNe laser. The basic notions of zero-crossing rate and artificial neural network (ANN) were applied to digitized tubular guided-waves to uniquely identify each of the following three bond defects: tensile pull, needle puncture, and crease. These induced flaws represent possible manufacturing defects such as de-bond, potential leak sources, and geometry irregularities. Zero-crossing rates were also found to uniquely identify localized stiffening due to an attached wire stent proving that this technique can unambiguously identify propagation modes from among non-propagation modes or vibrations. The 100% success rate reported in the paper renders the utility of TAP-NDE, along with ANN based classification scheme using zero-crossing rates, a viable quantitative measure for inspecting small-diameter polymeric medical tubing for sub-mm defects in real-time.

Medical diagnostic ultrasound catheter and method for position determination

A catheter and method for determining a position of the catheter within the cardiovascular system is provided. Local bending and twisting is measured at multiple locations along the catheter. By integrating the measurements, the position and orientation of the catheter is determined. Based on the catheter position information, the location and orientation of an ultrasound transducer array connected with the catheter is known. The imaging array position and orientation information may be used to assist a physician in determining the tissue structure or fluid being scanned and/or assist in the accurate generation of three-dimensional representations.

F07-(3) スマート化への材料・デバイス研究

High performance and multi-functional sensor/actuator materials is essential key technology developing smart/intelligent devices and systems. Fine fiber and foil-type sensor/actuator material elements of thermoslastic, ferromagnetic and magnetoelastic alloys were developed by using the originally designet rapid solidification (RS) melt-spinning apparatus. Those RS had strong crystalline texture with fine columnar grains that were uniquely formed during rapid-solidification process. These sensor/actuator material elements become useful to develop the high performance micro-electronic mechanical systems and intelligent/smart composite materials and structures. Several potential designs for faster composite actuator, medical catheter gripper and smart composites board for structural health-monitoring are shown as preliminary application proposals based on this study.