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At least 973 records · Page 54Linked to original sources
PubMed1984

Material thrombogenicity in central venous catheterization III. A comparison between soft polyvinylchloride and soft polyurethane elastomer, long, antebrachial catheters.

Soft venous catheters, 36 made of polyurethane (PU) and 37 made of polyvinylchloride (PVC), were inserted in 73 patients via basilic and cephalic veins punctured at the cubital fossa, and compared regarding their thrombogenicity. The mean duration of catheterization was 12.5 days. Two patients with PU- and six patients with PVC-catheters developed clinical thrombophlebitis 4-36 days after insertion. The radiological thrombi were rather small with both PU- and PVC-catheters in both peripheral and central veins with no significant difference between the catheters. Also, the incidence of thrombosis and the rate of catheter occlusions were similar. The surface topography of the PVC-catheters was relatively smoother, but less uniform than that of the PU-catheters. Platelet adhesion in vitro to the catheter surfaces, expressed as ATP-concentration in relation to catheter area after contact with human blood, was relatively low with both catheters. The results suggest that soft PU- and PVC-catheters have a similar thrombogenicity.

Adolescent↗
PubMed1989

Cannula thrombophlebitis: a study in volunteers comparing polytetrafluoroethylene, polyurethane, and polyamide-ether-elastomer cannulae.

Cannulae made of polytetrafluoroethylene (PTFE: n = 11), thermoplastic polyether-urethane (TPEU: n = 11), and a new test material, polyamide-ether-elastomer (XLON: n = 10) were inserted into the veins of the dorsum of the hand in 32 healthy volunteers (10 women and 22 men), 21-50 years old. The cannulae were intended to be left in place for 5 days. No infusion was given and the dressings were not exchanged. The resulting thrombophlebitis, defined as two or more of the symptoms pain, redness, oedema and hardness, was estimated on a scale which took into account the incidence, location, intensity, and duration of the symptoms. Except for one volunteer in the XLON group, all the volunteers developed thrombophlebitis, generally observed on the third day of cannulation, and being more frequent and intense over the cannulae (P less than 0.001) and at the tip (P less than 0.01) than at the insertion sites. Pain and oedema were, on the whole, the most frequent and severe symptoms during the period of indwelling. After withdrawal, hardness was the most intense, and together with pain, the most long-lasting (up to 10 days) symptom. The differences between the materials in thrombophlebitis incidence and intensity were statistically significant only when each symptom was analysed separately. Thus, the PTFE cannulae caused more pain and hardness (probably because of greater platelet adhesion and a relatively greater stiffness), while the TPEU and XLON cannulae produced more periphlebitis (redness and oedema), probably because of potentially irritant and antigenic substances leaking from them (polyurethane oligomers and polyamide/polyethyleneglycol oligomers).

Adult↗
PubMed1991

Penetration forces in cannulation of the dorsal veins of the hand: I. A comparison between polyurethane (Insyte) and polytetrafluoroethylene (Venflon) cannulae. Results of a study in volunteers compared with those from an in vitro study.

UNLABELLED: The functional tip tapering design of peripheral venous cannulae (introducer steel needle + catheter) made of polyurethane (PUR-Instye) and polytetrafluoroethylene (PTFE-Venflon) was studied with 3 techniques: A) Scanning electron microscopy (SEM). B) Measurement of penetration forces in vitro through latex membranes and lamb skins with a tensile-compression apparatus (Instron-1122) at 1) the introducer steel-needle point, 2) the needle heel (the spot marking the passage from the point of the needle to its shaft). 3) the catheter top (i.e. the beginning of the plastic sheath), 4) the catheter tip, i.e. the beginning of the largest diameter of the plastic sheath, and 5) between the catheter tip and its hub (catheter friction). C) Two cannulae (one of each type for every subject were inserted at random into the dorsal veins of the left and right hand in 37 volunteers, and the penetration forces were measured with a force transducer. RESULTS: A) The PUR-cannulae had a lancet-like appearance and a smoother transition at the catheter top, whilst the PTFE cannulae were arrow-like, cut back and had a less accentuated conical design. B) Penetration forces in vitro through latex membranes were 9-41 times lower (P less than 0.0001) than those through the large skins. The highest forces (mean +/- s.d.) registered in vitro (lamb skins) were 4.1 +/- 0.2 Newtons (N) with PUR-cannulae at the catheter tip, and 3.4 +/- 0.6 with the PTFE-cannulae at the catheter top (P less than 0.05). C).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed2005

Fit and seal characteristics of a new paediatric tracheal tube with high volume-low pressure polyurethane cuff.

BACKGROUND: To evaluate a new paediatric tracheal tube (Microcuff, Weinheim, Germany) with an ultrathin high volume-low pressure polyurethane cuff. METHODS: With approval of the Hospital Ethics Committee tracheas of children undergoing general anaesthesia were intubated using a Microcuff tube. Tube sizes were selected according to: internal diameter (mm) = age/4 + 3.5 in children aged > or = 2 years. In newborns (> or = 3 kg) < or = 1 year, ID 3.0-mm tubes, and in children from 1 to 2 years, internal diameter 3.5-mm tubes were used. Tubes were classified too large if no air leakage was obtained at an airway pressure of 20 cm H2O with the cuff not inflated. Sealing pressure was assessed by auscultation. Post-extubation croup requiring therapy was noted. RESULTS: Five-hundred children were studied. In eight children the tubes were too large. Sealing pressure was 9.7 +/- 2.5 cm H2O (4-20). In two patients postextubation croup required singular short-term therapy. CONCLUSIONS: Microcuff paediatric tracheal tubes provided tracheal sealing with cuff pressures considerably lower than usually accepted. The rate of tube exchange was very low (1.6%), as was the rate of airway morbidity (croup requiring therapy; 0.4%).

Adolescent↗
PubMed1996

Australian multicentre evaluation of a new polyurethane vascular access graft.

BACKGROUND: A new three-layered cast polyurethane vascular access graft (Thoratec VAG) is the most recent addition to the list of materials used in the search for the perfect prosthetic graft material for haemodialysis vascular access. Despite its use in 23 countries, a clinical assessment has not been published. METHODS: An independent retrospective evaluation by questionnaire was obtained for 145 implantation procedures performed by 30 surgeons. RESULTS: Ninety-two per cent of procedures were performed for an acute need for vascular access and 73% had prior failed vascular access surgery. Patients were hospitalized for a median of 4 days and the graft was initially used at a median of 3 days. Median follow-up was 306 days. Thoratec VAG had a problem-free (primary) patency of 44.9% and a functional (secondary) patency 64.5% at 1 year. Major causes of graft loss were thrombosis (17%) and infection (11%). Intra-operative thrombosis was the only significant risk factor for subsequent thrombosis (P = 0.013). Infection was less in patients with antibiotic prophylaxis that included vancomycin (P = 0.02). CONCLUSION: The ability to use the graft soon after surgery is a major advance for patients who urgently need reliable medium to long-term haemodialysis access.

Arteriovenous Fistula↗
PubMed1993

Compression stockings and non-continuous use of polyurethane foam dressings for the treatment of venous ulceration. A pilot study.

BACKGROUND: Venous ulceration is usually treated with Unna's boot. Recently another product, Ulcer-care, has been developed to treat these ulcers. OBJECTIVE: To evaluate the therapeutic value of Ulcer-care. METHODS: Over 24 months, 20 ambulatory patients with 30 lower extremity stasis ulcers were treated with a product consisting of: 1) a hydrophilic polyurethane sponge covered by a hydrophobic membrane changed daily or every other day; 2) an inner liner stocking that applies 10 mmHg pressure and is worn 24 hours a day; and 3) a surgical stocking with a posterior zipper that applies 30 mmHg graduated pressure and is removed at night. RESULTS: All ulcers healed after 2 to 30 weeks (mean 8.3 weeks) including 15 previously treated by Unna's boot or hydrocolloid dressings and 3 infected ulcers. CONCLUSION: The Ulcer care treatment for stasis ulcers is highly successful, easy to use, and well accepted by patients.

Ankle↗
PubMed1989

Endothelial cell seeding on different polyurethanes.

Six polyurethanes (PUs) were tested with respect to their cytocompatibility. Initial adhesion, initial spreading, and the proliferation of endothelial cells were investigated. All smooth PUs showed similar initial adhesion. Initial spreading was faster on rough PUs. Collagen coating resulted in faster initial adhesion but not better proliferation of endothelial cells.

Animals↗
PubMed1989

Isoelastic polyurethane prosthesis for segmental trachea replacement in beagle dogs.

Porous polyurethane (nonwoven) was used for the development of tracheal prosthesis, which--in a special testing design--was adapted to shape and biomechanic properties of the natural organ. This prosthesis was implanted into 19 beagle dogs using inverted, everted, and end-to-end anastomosis. Insufficiency of the anastomosis or infection was observed in the everted and end-to-end anastomosis, whereas the inverted anastomosis showed complete incorporation into surrounding tissue of the porous prosthesis but was complicated by airway obstruction due to anastomosis granuloma.

Anastomosis, Surgical↗
PubMed1995

Clinical trial of new polyurethane vascular grafts for hemodialysis: compared with expanded polytetrafluoroethylene grafts.

We developed a new polyurethane vascular access graft coated with gelatin and reinforced with knitted polyester fibers (PE-PEUG). Advantages over expanded-polytetrafluoroethylene graft (E-PTFEG) were previously reported in experimental studies. Between May 1990 and August 1992, 39 PE-PEUGs including 34 loop and 5 straight and 18 E-PTFEGs including 18 loop were implanted to create arteriovenous (AV) fistulas in a total of 52 adult patients on maintenance hemodialysis (HD). They were followed up until October 1994. Hemostasis on the suture line was achieved within 3 min in all patients implanted with PE-PEUGs. Bleeding from the needle holes of PE-PEUG stopped within 10 min with gentle finger pressure. Minimal local edema developed in only a few patients implanted with PE-PEUG while most patients implanted with E-PTFEG developed moderate local edema. One seroma formation was found in an E-PTFE case. Aneurysmal dilatations were observed twice in a PE-PEUG patient 9 and 17 months after the implantation and once in a E-PTFEG patient 2 years after the implantation. The cumulative patency rate at 1 year in the PE-PEUG and E-PTFEG groups were 53.2 and 70.8%, respectively. Our clinical study showed that the PE-PEUG had several advantages over E-PTFEG: prompt hemostasis, no persistent edema and no formation of seroma, no change in elasticity, and sufficient mechanical strength. However, the cumulative patency rate was inferior to that with E-PTFEG implanted in our series. Further modifications are therefore necessary to improve the patency rate.

Adult↗
PubMed2003

Improved retention of endothelial cells seeded on polyurethane small-diameter vascular grafts modified by a recombinant RGD-containing protein.

Sponge-type small-diameter vascular grafts were fabricated from a medical-grade polyurethane, Pellethane 2363-80A, by utilization of a salt casting technique. The grafts were compliance matched with a storage modulus of 0.53 +/- 0.08 MPa. The luminal surface of grafts was modified with a thin layer ( approximately 40 micro m) of gelatin crosslinked by epoxide. Then a special Arg-Gly-Asp (RGD)-containing recombinant protein, named CBD-RGD (cellulose binding domain RGD-containing protein), was coated onto the gelatin layer. The platelet adhesion and activation on such a gelatin/CBD-RGD modified surface was significantly reduced. Human umbilical vein endothelial cells were seeded more efficiently onto the modified grafts. There was also a substantial reduction in the subsequent loss of cells from the graft surface following perfusion in vitro. The cell number retained on the modified graft was enhanced by three times after 1 h of perfusion, and by eight times after 3 h of perfusion (retention rate approximately 63%). The retention after 3 h of perfusion could be further increased to nearly 100% if the lined endothelium on gelatin/CBD-RGD modified graft was cultured for another week before perfusion. The modified surface was also shown to help canine external jugular vein endothelial cells to maintain the round cell morphology in vitro.

Animals↗
PubMed2006

In vivo biocompatibility of sulfonated PEO-grafted polyurethanes for polymer heart valve and vascular graft.

Sulfonated poly(ethylene oxide) (PEO)-grafted polyurethane (PU) (PU-PEO-SO(3)) prepared by bulk modification was used to coat both PU heart valves and vascular grafts, and their in vivo biocompatibility was evaluated using a canine shunt method. The two devices were implanted for up to 39 days and retrieved at specific time points for the analysis of blood compatibility, biostability, and calcium deposition. When the surface of the retrieved specimens was examined using scanning electron microscopy, platelet adhesion and thrombus formation appeared to be significantly lesser formed on the PU-PEO-SO(3)-coated implants, compared with the untreated PUs. While molecular weights of untreated PUs were found by gel permeation chromatography to be decreased after 39 days from implantation, the same remained barely changed with the PU-PEO-SO(3)-coated ones. The inductively coupled plasma study indicated that the amount of deposited calcium was significantly reduced in the surface-modified PU implants. The efficacy of PU-PEO-SO(3)-coated implants in terms of blood compatibility, biostability, and calcification resistance may render them as a promising biomedical material in the application for blood/tissue-contacting tissues and organs.

Animals↗
PubMed1983

False inhibition of an atrial demand pacemaker caused by an insulation defect in a polyurethane lead.

A patient who had an atrial demand pacemaker (AAI) presented with irregular pacing at a routine examination 5 months after implantation. When a magnet was applied over the pulse generator regular fixed rate pacing was obtained, thus proving oversensing in the system. Reprogramming the input sensitivity level to 2.5 and 5.0 mV did not solve the problem. Programming the pulse generator to the triggered mode (AAT) showed acceleration of the stimulation rate but also inhibition of the system. An S-S interval of 1260 ms was measured at a programmed interval of 857 ms (70 bpm). The pulse generator was disconnected and the intra-atrial electrogram was recorded. This showed different spurious signals varying in morphology and amplitude. Fortunately we were able to remove the lead (Medtronic 6991-U) from the atrial appendage. Subsequently a Helifix 12 mm AT lead was successfully implanted in the right atrial appendage and the same pulse generator was connected to the newly implanted lead. When the removed lead was examined by the manufacturer, a small tear in the insulation of the wire was detected. The dimensions of the tear were 0.1 X 0.7 mm. The tear was caused by stress corrosion cracking in the polyurethane tubing of the lead.

Bradycardia↗
PubMed1983

Comparison of lead complications with polyurethane tined, silicone rubber tined, and wedge tip leads: clinical experience with 822 ventricular endocardial lads.

Lead-related complications have been prospectively studied for 602 unipolar tined endocardial ventricular pacemaker leads implanted over a five-year period. No differences were noted in overall complication rates between 238 polyurethane insulated leads (4.2%) and 364 silicone rubber insulated leads (3.6%). Comparing the total series of 602 tined leads to a retrospective survey of 220 wedge tip leads, a marked reduction in dislodgements (0.3% vs. 7.7%, P less than 0.001) and reoperations (2.0% vs 15.0%, P less than 0.001) was found using tined leads. We conclude that tined ventricular leads are far superior to wedge tip leads with respect to lead complications.

Arrhythmias, Cardiac↗
PubMed1984

Insulation failure with bipolar polyurethane pacing leads.

Between October, 1981, and April, 1983, 200 pacemakers were inserted at Rhode Island Hospital. Forty-five bipolar polyurethane leads (Medtronic 6972) were positioned in the right ventricle. Three (6.6%) of these leads presented 15 to 18 months post-implant with insulation failure. The manifestation was inappropriate inhibition of the pacemaker. No obvious cracking was visible on X-ray or during surgery. All the leads had low impedance, indicative of insulation failure.

Equipment Failure↗
PubMed1985

Examination of explanted polyurethane pacemaker leads using the scanning electron microscope.

Since 1978, 2,365 polyurethane (PU) insulated cardiac pacing leads were implanted transvenously at our institution. To date, there have been no insulation failures in those leads. Thirty-seven PU leads were explanted, mainly for exit block, and 28 of these were investigated using the scanning electron microscope. We found a homogeneous distribution of surface changes in all lead segments in 56% of the 28 examined. These changes were more pronounced at the ligature site; severe surface cracking was noticed in 21%, with the deepest crack being 40 micron (average range of 10-15 micron). There appeared to be no time-dependency of the surface changes as indicated by regression analysis (r = 0.32, p greater than 0.05). The ultimate severity and outcome of this degradation process in the leads reported in this study will only be known in the future after longer use. We conclude that excess stress must be avoided during the implantation procedure and that careful surveillance is necessary.

Equipment Failure↗