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  • 1
    ISSN: 1433-8580
    Keywords: Heparin ; Defibrase ; Extracorporeal circulation ; Membrane oxygenator ; Respiratory assistance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Complications arising from difficulty controlled bleeding and thrombus formation during procedures which require extracorporeal circulation with heparin as anticoagulant motivate the search for better hemostasis and anticoagulant technology. An enzyme (Defibrase), having a specific interaction with fibrinopeptide A such as to cause fibrin depletion in a soluble form, has been proposed as an alternative to heparin. Defibrase, in contrast to heparin, does not affect blood platelet function. Heparin and Defibrase as anticoagulants were compared in 8 h perfusion studies using arterio-venous extracorporeal blood circuits in dogs; the circuitry included pumps, membrane oxygenators and filters serially. Thrombus formation, in the filters and the oxygenators as well as pathology of the perfused animal were investigated. The results suggest that defibrase-like enzymes have potential for enhanced control of hemorrhagic and thrombotic phenomena. Although impeded by a latency of several hours before the full anticoagulant properties are developed in vivo, it appears that enzymatically mediated defibrinogenation of blood may be a valuable alternative to heparinization in extracorporeal circulation procedures.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1433-8580
    Keywords: Vascular surgery ; Graft ; Suture ; Vascular clamp ; Needle-holder
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Scanning electron microscopy was used to diagnose incidents of trauma and the pattern of healing following surgical implantation of microporous blood vessel substitutes. Vascular reconstruction procedures using autogenous or synthetic prosthetic material inflict damage to the adjacent tissues as well as the prosthesis. This affects the thrombotic behavior and healing pattern of the area. The prognosis for long-term success are, as a consequence, directly influenced. Various vessel-occluding devices were evaluated in canine models with respect to their ability to damage blood vessels at the clamped site. The impact of suture needles on tissues and prosthetic materials was also considered. Of the various vessel-clamping devices which are commercially available, those which have elastomeric shields on the clamping components were found to be most satisfactory. The development of less traumatical surgical devices is discussed with the aim of further reducing surgical trauma.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Surgical endoscopy and other interventional techniques 8 (1994), S. 1324-1328 
    ISSN: 1432-2218
    Keywords: Abdominal wall defect ; Bursting strength ; Polypropylene mesh ; Endoscopic staples ; Mesh incorporation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The strength conferred to a mesh by fixing it with laparoscopic staples and the effects of tissue incorporation have never been quantified. Eighteen dogs were divided into three groups sacrificed at 2 days (5 dogs), 2 weeks (6 dogs), and 2 months (7 dogs). One 3.5- by 5-cm piece of abdominal wall was removed from each side through a median laparotomy, leaving the skin intact. A polypropylene mesh (5 by 7 cm) was fixed over one defect with four Endopath EMS staples (Ethicon Endo-surgery) and over the other with 16 EMS staples. At sacrifice, bursting strength (BS) was measured with an Instron tester and specimens were studied histologically. One-way analysis of variance and the Newmann-Keuls multiple-comparison test were used. BS tests showed that for each period studied, the strength of the repair performed with 16 staples was significantly higher than that obtained when four staples were applied. They also showed that tensile strength increased significantly in both groups as time elapsed. Light microscopy supported the conclusion that the initial strength of the repair was related to the number of clips and was significantly increased by cellular infiltration at 2 weeks and significantly more by collagen deposition at 2 months. At 2 months, BS was significantly higher in the 16-staples group, suggesting that initial fixation still plays a significant role.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 7 (1996), S. 40-45 
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Lipid uptake in 104 ePTFE microporous vascular prostheses implanted in humans was investigated using Fourier transform infrared (FTIR) spectroscopy. The assignment of the infrared features observed in the spectra of explanted ePTFE microporous vascular prostheses shows unambiguously the presence of fatty acids in the structure of the arterial prosthesis wall. In addition, higher lipid concentration is found on the external side of the prostheses before 500 days of implantation, after which this behaviour is reversed. Finally, it seems that a greater amount of lipids are present on the surfaces of prostheses implanted in extra-anatomical sites as compared to those implanted in anatomical sites.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 18 (1984), S. 895-909 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: An alternative to the usual technique of preclotting porous textile vascular prostheses prior to surgical implantation is to render them impermeable to blood by impregnation with a cross-linked albumin filler matrix. This material subsequently becomes the foundation for cellular development. The compatibility of such impregnated fabrics with newly formed endothelial cells has been evaluated by an in vitro organotypic culture method. This technique enables the characterization and numeration of cells that develop on blood contact surfaces and enables determination of their rate of development. Woven, knitted, and velour fabrics were evaluated folllowing coating with albumin and either storage in Tyrode solution or 40% ethanol or desiccation by critical point drying. Preclotted cardiovascular repair fabrics prepared according to conventional surgical protocol served as controls. The identification of the newly formed cells was confirmed histologically. The most extensive and rapid cellular development was observed on the woven fabric and is believed may have resulted from the smoother surface topography of this substrate. Good cellular development was noted particularly on fabrics which had been stored in Tyrode solution. Ethanol had a deleterious effect on the apparent compatibility.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: In an attempt to find an alternative procedure to the preclotting of porous textile vascular prostheses, the feasibility of an albumin coating and ethanol preservation technique has been evaluated by implanting albuminated polyester prostheses as substitutes in the thoracic aorta of dogs. Nine different grafts representing woven, knitted, and velour constructions were implanted for periods ranging from 4 h to 6 months. At the sacrifice, the grafts were excized for measurement of the thrombogenicity of the flow surface, for pathological examination by light microscopy and SEM, and for quantifying the changes in the textile structure during implantation. Also the kidneys were removed and examined for infarcts caused by trapped circulating emboli. The healing characteristics of the nine different grafts proved similar and followed the same sequence of events as preclotted control grafts. The albumin coating and ethanol preservation resulted in a somewhat slower rate of healing. Yet, given sufficient time, a more completely healed graft was achieved as evidenced by the presence of endothelial-like cells throughout the length of the graft. In addition, the albumin is believed to reinforce the textile structure by reducing the tendency to stretch and dilate in vivo.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Morphological, histological, and scanning electron microscopy examinations were performed on 90 surgically excised human umbilical vein grafts. Most of the explanted grafts were removed because of thrombosis or infection and were removed typically from a patient in the mid 60s and after an average duration of implantation of 11 months. Multiple structural defects were found including deep folds, breaks on the luminal surface, and delamination. These areas as well as anastomotic sites represented potential areas for thrombotic accumulation. A higher incidence of infection was observed in grafts composed of 2 or 3 segments. Bacteria were often found in folds and could be seen invading the wall of the prosthesis. In addition, bacteremic colonization was often seen in noninfected grafts. The late aneurysmal formations were also of particular concern. The biodegradation of the wall and the disruption of the polyester mesh were the probable causes. The second generation Dardik Biograft aimed at reducing these formations. The success of this new processing remains to be evaluated.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Using canine models, a representative selection of polyester or Dacron vascular prostheses, including woven, knitted, and velour types, were evaluated for their relative healing characteristics and for their structural changes during implantation. Following residence periods ranging from 4 h to 6 months at the site of the thoracic aorta, the dogs were sacrified, and the grafts were excized for measurement of the thrombogenicity of the flow surface and for pathological examination by light microscopy and SEM. The kidneys were also removed and examined for infarcts caused by any trapped circulating emboli. The extent of healing, the presence of embolizing nuclei, and the thrombogenicity and morphology of the lumen surface were also assessed. The healing characteristics of each type of device proved similar. Velour fabrics exhibited more extensive encapsulation, but frequently their internal capsules failed to incorporate all the fibers. In all cases, cellular development on the lumen was limited to areas contiguous to the anastomoses. The initial porosity of the devices as measured by water permeability did not appear to influence the healing sequence to a significant extent. The grafts did exhibit differences in structural stability depending on whether they were of a knitted or woven construction. We suggest that users consider these different mechanical and structural properties when making their choice of a graft. Despite these differences, we believe that the healing process is far more host dependent than graft dependent.
    Additional Material: 21 Ill.
    Type of Medium: Electronic Resource
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