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At least 1,135 records · Page 63Linked to original sources

PubMed1989

Elastic properties and strength of a novel small-diameter, compliant polyurethane vascular graft.

Tensile properties and pressure-diameter-axial force relations of a newly developed small-diameter arterial graft were determined and compared to those of commercially available grafts and natural arteries. The material was synthesized from 4,4'-diphenylmethane diisocyanate, polytetramethylene glycol, and polyethylene oxide, chain-extended with ethylene glycol. Porous conduits (3-mm internal diameter) were fabricated of this material by means of a phase separation technique, and their outer surfaces were covered with woolly polyester net in order to prevent excessive dilation. Mechanical tests indicated that the polyurethane graft has distensibility and strength similar to that of natural arteries, and has been proved to be useful for the arterial reconstruction, particularly for the replacement of small-diameter blood vessels.

Blood Vessel Prosthesis↗

PubMed1989

Biostability of polyurethanes.

Aside from the medical requirements a material has to fulfill to qualify as biocompatible, for the bioengineer, who is involved in the design, construction and fabrication of prosthetic devices, the mechanical, physical and chemical properties of the material as well as its possible manufacturing procedures and, last but not least, its biostability are of the same importance. In the very aggressive biological environment, the material should behave inertly, showing no surface erosions, molecular chain disruptions, uptake of low molecular weight biological materials, local chemical imbalances, tendency to calcification or negative changes of mechanical properties. With regard to this aspect, different polyurethanes have been evaluated in-vitro and in-vivo as basic materials and already fabricated devices (blood pumps and heart valves). The comparison of the results stresses the necessity of further efforts to achieve a standardized test protocol for the prove of the biostability of polymers, containing appropriate, well-defined in-vitro and in-vivo test methods to establish the necessary data basa for the materials' clinical approval.

Animals↗

PubMed1989

[The incidence of neurotoxic complications in polyurethane production].

40 labour employed with the production of polyurethan had been subject to a subtile, clinical, neurological, psychological and neuropsychological examination. Troubles of the respiratory and the gastrointestinal tracts had been predominantly, neurasthenic symptoms had been registered in 22.5%. It is recommended to perform in all the exposed labour a neurological basis examination and to utilize the psychological-neurological inquiry (PNF).

Adult↗

PubMedDate not supplied

Epidemiological measurement of bronchial responsiveness in polyurethane workers.

A shortened protocol was developed for the epidemiological measurement of bronchial responsiveness to methacholine without compromising sensitivity, power, precision or safety, and without distorting the numerical value of the PD20.FEV1 (the cumulative dose from a doubling incremental sequence which provokes a 20% decrement in FEV1). It was used in a survey of 254 polyurethane workers (83% of the eligible workforce) exposed occupationally to toluene diisocyanate. The mean duration of each test proved to be 38 min, it was well tolerated and 64 workers (25%) proved to be reactors. PD20.FEV1 appeared to be distributed unimodally. It was significantly correlated with questionnaire records of shortness of breath, chest tightness, and wheeze; and with pre-shift FEV1 and FEF25-75. Even the reactors requiring the highest dose of 640 cumulative inhalation units (1 unit = one 8.9 microliters inhalation of methacholine 1 mg.ml-1) to generate a PD20 measurement reported significantly more wheeze than the non-reactors. This indicates that the test had clinical meaning throughout its dose range of 0.3-640 units. No correlation was found between PD20 and individual changes in ventilatory function across the working shift, but mean shift changes were negligible and not statistically significant. PD20 was also found to be unrelated to age, sex, race, smoking, cough and atopy.

Asthma↗

PubMed1987

Accelerated healing of carbon dioxide laser burns in rats treated with composite polyurethane dressings.

Healing time, infection rate, and residual scar formation were compared in carbon dioxide laser burns in rats treated in four ways: Spandra composite dressing, OpSite composite dressing, Petrolatum Gauze (USP), and no treatment. There were no infections and no differences in scar formation among the treatment groups. The mean healing times were ten days for the polyurethane dressings (Spandra and OpSite), 13 days for Petrolatum Gauze, and 16 days for the untreated group. Spandra was easier to apply and handle than OpSite. These findings suggest that synthetic gas-permeable dressings promote healing after cutaneous carbon dioxide laser surgery more effectively than conventional treatments of ointment-impregnated gauze or leaving the wound exposed to the air.

Animals↗

PubMed1987

Evaluation of dressing regimens for prevention of infection with peripheral intravenous catheters. Gauze, a transparent polyurethane dressing, and an iodophor-transparent dressing.

Four dressing regimens for peripheral venous catheters were studied in a prospective randomized clinical trial with 2088 Teflon catheters: (1) sterile gauze, replaced every other day, and three dressings left on for the lifetime of the catheter; (2) gauze; (3) a transparent polyurethane dressing; and (4) an iodophor-transparent dressing. The four dressings provided comparable coverage, except moisture accumulated more frequently under the transparent dressings (26% to 28% vs 20% to 21%). Cutaneous colonization under the dressing was low level and comparable with all four dressings (range, 10(0.58) to 10(0.70) colony-forming units). The rate of local catheter-related infection (greater than or equal to 15 colony-forming units) was also low and did not differ significantly (range, 4.6% to 5.9%); no catheter caused bacteremia. Stepwise logistic multivariate analysis showed cutaneous colonization of the insertion site (relative risk [RR] of infection, 3.86), contamination of the catheter hub (RR, 3.78), moisture under the dressing (RR, 2.48), and prolonged catheterization (RR, 1.75) to be significant risk factors for catheter-related infection. These data indicate that it is not cost-effective to redress peripheral venous catheters at periodic intervals; for most patients, either sterile gauze or a transparent dressing can be used and left on until the catheter is removed.

Bandages↗

PubMedDate not supplied

Suppression mechanisms for thrombus formation on heparin-immobilized segmented polyurethane-ureas.

Heparin-immobilized segmented polyurethane-ureas (Biomer, Ethicon Co., Somerville, NJ) containing long poly(ethylene oxide) spacers (Mn = 4,000) have shown excellent nonthrombogenic properties through enhanced heparin bioactivity in vitro. In this study, three different surfaces, Biomer (B), PEO-grafted Biomer (B-PEO) and heparin-immobilized Biomer with PEO spacers (B-PEO-Hep), were investigated, using a rabbit A-A shunt model. Occlusion times, at various flow rates (2.5, 5.0, 7.5, and 15.0 ml/min) were measured using surface modified tubings (1.5 mm ID, 30 cm length) inserted into rabbit carotid arteries. Platelet count, aggregability, and activated partial thromboplastin time (aPTT) were measured with whole blood to observe systemic effects in ex vivo experiments. For Biomer and B-PEO, occlusion times were prolonged with an increasing flow rate, while platelet count and aggregability decreased. B-PEO showed prominent prolongation of occlusion time at flow rates over 5.0 ml/min with decreased platelet count and aggregability, indicating surface-induced platelet activation and systemic thromboembolization possibly caused by the presence of PEO. In contrast, B-PEO-Hep surfaces showed the longest and relatively flow-rate-independent occlusion times without detectable platelet activation. We concluded that the improved ex vivo blood compatibility of B-PEO-Hep, compared with Biomer and B-PEO, is due to the prevention of fibrin net formation by immobilized heparin, resulting in a reduction in fibrin related platelet aggregation and subsequent thrombus formation.

Animals↗

PubMed1988

A 5-year experience with polyurethane-covered mammary prostheses for treatment of capsular contracture, primary augmentation mammoplasty, and breast reconstruction.

This paper reviews a 5-year experience using polyurethane-covered mammary prostheses in the treatment of capsular contracture following placement of smooth-walled devices, primary augmentation mammoplasty, and breast reconstruction after mastectomy. The rate of occurrence of clinically significant capsular contracture has been reduced in all patient groups. Results in terms of aesthetic and functional improvement have been excellent. Major complications have been rare.

Breast↗

PubMed1988

A comparison of the behaviour of autologous and homologous platelets in microporous polyurethane grafts. An experimental study in sheep.

In experimental studies in sheep the behaviour of autologous and homologous platelets in microporous polyurethane grafts was compared at a flow rate of 25 ml/min. The grafts were interposed to replace segments of resected carotid arteries. The deposition of 32P-labelled platelets on the graft wall was recorded, as were graft patency, thrombus weight and thrombus-free surface. Compared to autologous platelets, homologous platelets accumulated over longer periods of time and in greater numbers, leading to deposition of larger amounts of thrombus material and reduced patency.

Animals↗

PubMedDate not supplied

Complete translocation of the aortic root and coronary bypass grafting with a microporous polyurethane (Mitrathane) composite valved graft in the treatment of recurrent prosthetic valve endocarditis.

The case of a 20-year-old male patient, with a history of addiction to parenteral heroin and recurrent prosthetic valve endocarditis, is presented. In this case the final procedure consisted of a complete translocation of the aortic root and coronary bypass grafting with a composite graft made from a microporous polyurethane (Mitrathane) cardiac patch, a prosthetic valve and two Mitrathane vascular grafts for the coronaries. This is a complex operation, only indicated in cases of extensive destruction of the aortic root due to recurrent endocarditis. To our knowledge, it is the first case of this type performed using Mitrathane.

Adult↗

PubMed1987

[Clinical experience using polyurethane ureter endoprostheses and studies of the incrustation tendency].

The advantages of internal urinary drainage by using ureteral splints have often been discussed during the last years. Using this technique in our clinic for 17 years nearly 2000 ureteral splints have been applied in 650 patients. Since 1978, in 164 patients ureteral splints made of polyurethane (PUR) were used. The indications are listed. The complication-rate is very low. Ureteral splints which had been removed after varying periods were examined by scanning electron microscopy. Results of these studies are shown.

Humans↗

PubMed1987

Intravenous cannula fixing and dressing--comparison between the use of transparent polyurethane dressing and conventional technique.

A sterile, disposable, polyurethane intravenous catheter dressing (OpSite; Smith & Nephew), was compared with a conventional dressing for both convenience and cost. Despite lack of familiarity, the use of OpSite proved as easy and acceptable as the traditional non-sterile control method. OpSite was also as durable and would appear, on calculation, to be cheaper when intravenous therapy lasts longer than a day. OpSite is therefore recommended as the intravenous dressing of choice. Its use, or that of a similar sterile disposable product, should be considered mandatory for paediatric and other patients in whom sterility is vital, and in situations where intravenous infusion will continue for more than 24 hours.

Antisepsis↗

PubMedDate not supplied

Cell seeding on microporous and solid polyurethane.

Cell coating with human embryonal fibroblasts was examined on solid (Plathurane UM 8300) and microporous (Tecoflex 80 A) polyurethane. Using measurements of cellular growth kinetics and adhesion strength it was found that the onset of cellular growth on the microporous material was delayed but that the vitality and adhesion strength of the cells were better than for the solid material.

Cell Adhesion↗

PubMed1986

Experimental meniscal lesions reconstructed with a carbon fiber-polyurethane-poly(L-lactide) graft.

Reconstructive procedures were investigated in meniscal lesions in 14 dogs. Large wedge-shaped lesions were repaired with a graft containing carbon fibers and an organic polymer, prepared from physical mixtures of poly(L-lactide) and a segmented polyurethane. Four and eight weeks postoperation, arthroscopy was performed and the implants were excised. In ten dogs, the reconstructed area appeared to be invaded almost completely by fibrous tissue and, occasionally, by repair-simulating hyaline cartilage. There were no signs of infection.

Animals↗

PubMed1985

The use of transparent semipermeable polyurethane membrane for percutaneous drainage of the biliary tract.

Transparent semipermeable polyurethane membrane was used in maintaining percutaneous biliary tract drains in nine patients. The average length of biliary tract drainage was 59.4 +/- 45.3 days. The membrane was found to be useful and the complications associated with biliary tract drains were reduced. This technique has been well accepted by patients and the medical and nursing staff.

Adhesives↗

PubMed1985

[Testing of polyurethane as an implant for its biological compatibility].

A simple biological method is described for testing the biological compatibility of plastics without histological investigation. This is the implantation into the anterior chamber of the rabbit eye. The test material is polyurethane soft foam (SYSpur). It can be observed as biologically compatible. This result agreed with expert opinions on toxicity and histocompatibility.

Animals↗

PubMed1983

Implant experience with unipolar polyurethane pacing leads.

A total of 905 unipolar polyurethane pacing leads have been implanted by the first author's group, between April 1978 and February 1982, with a mean implant of 1.4 years. Twelve leads were explanted and analyzed. Eleven of the explanted leads exhibited some degree of surface damage or "frosting." Of the 11, five atrial (Medtronic 6991 U) and one ventricular (Medtronic 6971) lead suffered complete insulation failure. One lead was completely free from surface damage. Clinically, insulation failure presented as muscle stimulation and/or battery depletion. Surface damage appears to be due to an environmental stress cracking (ESC) mechanism. ESC requires both a surface active agent from the hostile biological environment, and stress in excess of a threshold value. The minor surface damage or "frosting" of the eleven explanted leads was typically 10 to 15 microns deep on leads implanted about one year, although one device (15 months) had 30 micron cracks. No lead failures in this series were attributed to this shallow cracking mechanism. The severe cracking of the six Medtronic leads leading to insulin failure was thought to be due to the unusually high tensile stresses imposed by manufacturing processes and ligatures. The incidence of failure was 7% (5/74) for the Medtronic 6991 U and 0.2% (1/454) for the Medtronic 6971. Medtronic lead manufacturing processes have been modified to reduce the high residual tensile stresses and a fixation sleeve has been added to reduce ligature stress.

Arrhythmias, Cardiac↗

PubMedDate not supplied

[Activity of proteolytic enzymes in the kidney and blood serum of rabbits during implantation of different polyurethanes].

It is shown that the activity of neutral proteinase both in homogenate and in blood serum increases by the 14th day the D-1 sample being implanted. In the subsequent periods after implantation the enzyme activity in homogenate is the same. Three and six months after implantation the neutral proteinase activity in blood serum decreases as compared to the norm. The activity of acid proteinase in rabbit kidney homogenates lowers by the 90th day after implantation both for the D-1 and for A-10 samples. For the D-1 sample the enzyme activation in blood serum is observed by the 30th day after implantation, three months later it falls to reach the normal level in 6-12 months and inhibition activity on the 30th day after implantation on the A-10 sample. Such changes in the activity of enzymes in homogenates and blood serum may reflect certain stages of polyurethane biodestruction participation of various enzymic systems of the organism in these processes.

Animals↗