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PubMed1994

A prospective, randomized trial of gauze and two polyurethane dressings for site care of pulmonary artery catheters: implications for catheter management.

OBJECTIVES: To compare the safety of a conventional polyurethane transparent dressing and a novel highly permeable polyurethane dressing, as compared with standard gauze and tape, as site dressings for pulmonary artery catheters; and to rigorously determine the sources of bloodstream infections deriving from these catheters. DESIGN: Prospective, randomized, clinical trial. SETTING: General adult intensive care units (ICUs) in a university hospital. PATIENTS: A total of 442 adult patients with pulmonary artery catheters were studied. Two thirds of the catheters had been inserted in the operating room and one third had been inserted in an ICU. INTERVENTIONS: Patients were randomized at the time of pulmonary artery catheter insertion to have one of three dressing regimens: a) sterile gauze and tape (control), replaced every 2 days; b) a conventional polyurethane dressing, replaced every 5 days; or c) a highly permeable polyurethane dressing, also replaced every 5 days. MEASUREMENTS AND MAIN RESULTS: The origin of each catheter-associated bloodstream infection was sought by quantitatively culturing the skin of the insertion site and all potential sources on the catheter, including the hub and infusate from each lumen of the introducer sheath and the pulmonary artery catheter, and intravascular segments of the introducer sheath and pulmonary artery catheter. Bloodstream infection was confirmed by demonstrating concordance between isolates from the device and blood cultures by pulsed-field electrophoresis of genomic DNA, digested with low-frequency-cleavage, restriction endonucleases. One hundred thirty catheters were randomized to be dressed with sterile gauze and tape (control), 127 with the conventional polyurethane dressing, and 185 with the highly permeable polyurethane dressing. Patients and catheters in the three dressing groups were very comparable. Ninety-six (21.7%) of the 442 catheters studied showed colonization of the introducer sheath or the pulmonary artery catheter, and five (1.1%) catheters caused bloodstream infection. Catheter-related bloodstream infections were associated with concordant cutaneous colonization of the insertion site (n = 2), a contaminated catheter hub or infusate (n = 3), contamination of the extravascular segment of a repositioned catheter beneath the external protective plastic sleeve (n = 1), or hematogenous colonization of the catheter (n = 1). All pulmonary artery catheter-related bloodstream infections occurred with catheters (introducers) in place for > or = 5 days (p < .001). Cutaneous colonization under the dressing at catheter removal was lowest with gauze (10(1.3) colony-forming units), intermediate with the new highly permeable polyurethane dressing (10(1.8) colony-forming units; p < .01), and highest with the conventional polyurethane dressing (10(2.0) colony-forming units; p < .001). There were no significant differences in catheter colonization (20.0 to 25.2 cases per 100 catheters) or catheter-related bloodstream infection (0.8 to 1.6 cases per 100 catheters) between the three groups. CONCLUSIONS: The incidence of pulmonary artery catheter-related bloodstream infection has decreased over the past 5 yrs. Pulmonary artery catheter-related bloodstream infections originate from multiple sources, indicating that measures to prevent bacteremic infections of these devices must focus both on reducing cutaneous colonization at the insertion site and averting contamination of infusate and catheter hubs. Efforts should be made to limit the duration of catheterization with pulmonary artery catheters (including the introducer) to no longer than 4 days. The polyurethane dressings studied appear to be safe for use with pulmonary artery catheters and may be left on for up to 5 days between dressing changes.

Aged↗

PubMed1997

A comparison of transparent polyurethane and dry gauze dressings for peripheral i.v. catheter sites: rates of phlebitis, infiltration, and dislodgment by patients.

BACKGROUND: Before a meta-analysis by Hoffman et al was published, polyurethane dressings were used at insertion sites for peripheral i.v. catheters at our institution. On the basis of the results of the meta-analysis, we began to use gauze dressings. The change from polyurethane dressings to gauze dressings limited direct observation of the i.v. insertion site, and i.v. catheters were anecdotally reported not to be anchored as securely as before. OBJECTIVES: The purpose of this study was to compare the effects of the use of transparent polyurethane dressings and gauze dressings at insertion sites for peripheral i.v. catheters on the frequency of phlebitis, infiltration, and catheter dislodgment by patients. METHODS: Two hundred twenty-nine patients were randomized to receive either gauze (n = 121) or transparent polyurethane (n = 108) dressings, and observations were recorded. RESULTS: The frequency of catheter dislodgment by the patient was significantly higher (P < .05) in patients with the gauze dressing (15%) than in patients with the transparent polyurethane dressing (6%). A trend toward lower frequencies of phlebitis (1.8% vs 3.3%) and infiltration (17.6% vs 20.7%) was noted in the patients with the transparent polyurethane dressings. DISCUSSION: The clinical advantages of the transparent polyurethane dressings lie in the ease of direct visualization of the i.v. insertion site and the securement of the i.v. catheter. CONCLUSION: At our institution, given the decreased disruption of the i.v. therapy with the transparent polyurethane dressings and the lack of differences in the rates of phlebitis or infiltration with the two types of dressings, we prefer to use transparent polyurethane rather than gauze dressings at insertion sites for peripheral i.v. catheters.

Catheterization, Peripheral↗

PubMed1978

Evaluation of sunlight stability of polyurethane elastomers for maxillofacial use. I.

The evaluation of the efficiency of polymer additives with special emphasis on uv absorbers and antioxidants in polyurethane elastomers has been completed. Aliphatic polyurethanes were chosen for this study because their properties closely relate to the requirements of maxillofacial prosthesis. The polyurethane elastomers were either synthesized by ourselves or formulated according to the manufacturer's recommendation. Eleven different types of uv absorbes, coupled with one antioxidant, were incorporated into the polyurethane systems. The Atlas twin-lamp carbon arc Weatherometer was used as the source of uv. The samples were periodically withdrawn for examination of yellowing and tackiness. It was found that, although the incorporation of uv stabilizers enhanced the uv resistance of polyurethanes, the problem of tackiness resulting from uv aging was not solved satisfactorily. The phenomenon of yellowing, however, was significantly improved, mainly due to the aliphatic structure of polyurethanes. The most promising uv absorbers are Tinuvin 770 and the combination of Tinuvin 328, ZnO, and an antioxidant. Their effectiveness in other polyurethane systems is not known and further research is underway to explore this field. Hopefully, these findings will greatly assist the successful application polyurethane elastomers in maxillofacial prosthesis.

Biocompatible Materials↗

PubMed2005

Biostability and macrophage-mediated foreign body reaction of silicone-modified polyurethanes.

In this study, the effect of soft segment chemistry on the phase morphology and in vivo response of commercial-grade poly(ether urethane) (PEU), silicone-modified PEU (PEU-S), poly(carbonate urethane) (PCU), and silicone-modified PCU (PCU-S) elastomers were examined. Silicone-modified polyurethanes were developed to combine the biostability of silicone with the mechanical properties of PEUs. Results from the infrared spectroscopy confirmed the presence of silicone at the surface of the PEU-S and PCU-S films. Atomic force microscopy phase imaging indicated that the overall two-phase morphology of PEUs, necessary for its thermoplastic elastomeric properties, was not disrupted by the silicone modification. After material characterization, the in vivo foreign body response and biostability of the polyurethanes were studied using a subcutaneous cage implant protocol. The results from the cage implant study indicated that monocytes adhere, differentiate to macrophages which fuse to form foreign body giant cells on all of the polyurethanes. However, the silicone-modified surfaces promoted apoptosis of adherent macrophages at 4 days and high levels of macrophage fusion after 21 days. These results confirm that the surface of a biomaterial may influence the induction of apoptosis of adherent macrophages in vivo and are consistent with previous cell culture studies of these materials. This study validates the use of our standard cell culture protocol to predict in vivo behavior and further supports the hypothesis that interleukin-4 is the primary mediator of macrophage fusion and foreign body giant cell formation in vivo. The impact of these findings on the biostability of polyurethanes is the subject of current investigations. Attenuated total reflectance-Fourier transform infrared analysis of explanted specimens provided evidence of chain scission and crosslinking at the surface of all of the polyurethanes. The silicone modification did not fully inhibit the oxidative biodegradation of the polyether or polycarbonate soft segments; however, the rate of chain scission of PEU-S and PCU-S seemed to be slower than the control polyurethanes. To verify this finding and to quantify the rate of chain scission in order to predict long-term biostability, an in vitro environment that simulated the microenvironment at the adherent cell-material interface was used to accelerate the biodegradation of the polyurethanes. Polyurethane films were treated in vitro for up to 36 days in 20% hydrogen peroxide/0.1M cobalt chloride solution at 37 degrees Celsius. Characterization with attenuated total reflectance-Fourier transform infrared and scanning electron microscopy showed soft segment and hard segment degradation consistent with the chemical changes observed after long-term in vivo treatment. The biostability ranking of these four materials based on rate of chain scission and surface pitting was as follows: PEU < PEU-S PCU < PCU-S. The silicone modification increased the biostability of the PEU and PCU elastomers while maintaining the thermoplastic elastomeric properties.

Biocompatible Materials↗

PubMed2003

Contraceptive effectiveness of a polyurethane condom and a latex condom: a randomized controlled trial.

OBJECTIVE: To compare the contraceptive effectivenesses of a polyurethane condom and a standard latex condom. Secondary outcomes of interest were safety, functionality, discontinuation, and acceptability. METHODS: We randomized 901 couples to use either the polyurethane condom or a standard latex condom as their only form of contraception. We tested for pregnancy at enrollment and at every scheduled follow-up visit (weeks 4, 10, 16, 22, and 30). RESULTS: The 6-month typical-use pregnancy probabilities were 9.0% (95% confidence interval [CI] 5.9, 12.2) for the polyurethane group and 5.4% (95% CI 2.9, 7.8) for the latex group; the hazard ratio was 1.7 (95% CI 1.1, 2.7), and we failed to reject the null hypothesis of our test of noninferiority. Females in the polyurethane group reported fewer genital irritations (hazard ratio 0.6; 95% CI 0.5, 0.8; P <.01), whereas males in both groups reported the same number of genital irritations (hazard ratio 1.0; 95% CI 0.7, 1.5; P =.94). Total clinical failures (breakage and slippage) were 8.4% for the polyurethane condom and 3.2% for the latex condom (difference 5.3%, 90% CI 2.8, 7.7). The risk of discontinuation did not differ between groups. Participants judged both condoms favorably in terms of the four primary acceptability outcomes (willingness to purchase, willingness to recommend, confidence in method, and general comfort). CONCLUSION: The polyurethane condom was not shown to be as effective as the latex comparator condom for pregnancy prevention. However, the risk of pregnancy in the polyurethane group falls in the range of other barrier methods. For people with latex sensitivity or who find latex condoms unacceptable, this polyurethane condom represents one of several synthetic male condom alternatives currently available on the US market.

Adolescent↗

PubMed2000

A randomized trial of polyurethane and silicone percutaneous endoscopic gastrostomy catheters.

BACKGROUND: No data are available on differences in complication rate and long-term functioning between polyurethane and silicone percutaneous endoscopic gastrostomy (PEG) catheters. METHODS: We randomized patients who qualified for PEG placement to receive either a polyurethane or silicone PEG catheter. Patients were prospectively monitored for 28 days after placement for the occurrence of complications. Data on long-term PEG survival were obtained retrospectively from the Hospital and general practitioner's medical records. RESULTS: One hundred and six patients were randomized (polyurethane 50, silicone 56). During the first four weeks of follow-up, major complications occurred twice with both polyurethane and silicone PEGs (relative risk 1.1, 95% confidence interval: 0.11-11). Overall complications occurred four times with polyurethane and 17 times with silicone PEGs (relative risk 3.8, 95% confidence interval: 1.37-10.5). Long-term follow-up was available in 96 patients. Seven polyurethane PEGs and 10 silicone PEGs were removed because of PEG malfunctioning, the remainder functioned well until death or the reinstitution of oral feeding. The median complication-free survival was 916 days for the polyurethane PEG and 354 days for the silicone PEG (Log rank test: P=0.24). CONCLUSION: Polyurethane PEG catheters were associated with less short-term complications than silicone catheters, but major complications and long-term function were comparable.

Adolescent↗

PubMed2004

Dwell time and functional failure in percutaneous endoscopic gastrostomy tubes: a prospective randomized-controlled comparison between silicon polymer and polyurethane percutaneous endoscopic gastrostomy tubes.

BACKGROUND: Silicone percutaneous endoscopic gastros-tomy (PEG) tubes are associated with more short-term complications and possibly fail sooner than those made of polyurethane. Understanding the deterioration and long-term complications leading to tube failure has important clinical and cost implications. AIM: To compare dwell time and patterns of failure ofsilicone polymer and polyurethane PEG tubes. METHODS: Participants randomized to receive a siliconepolymer (n = 76) or polyurethane (n = 62) PEG werevisited monthly for 540 days, until death or tube removal. Tube and exit site characteristics and reasons for removal were recorded. RESULTS: Tube failure occurred in 25% of silicone PEGs and 12.9% of polyurethane PEGs. Mean tube survival for silicone PEGs was 377.2 days (CI: 326-428) and for polyurethane 436.8 days (CI: 383-490; P = 0.13). A greater proportion of silicone PEGs developed intralumenal colonization and altered tube integrity than polyurethane (P < 0.001). Silicone PEGs blocked more frequently (P < 0.005) and were removed because of irreversible blockage more often than polyurethane PEGs (P < 0.05). Silicone PEGs with reversible blockage and tube integrity changes had a significantly greater probability of failure than silicone tubes without these changes (P < 0.005 and P < 0.05, respectively). CONCLUSIONS: Observations over time indicate that sili-cone PEGs are more susceptible than polyurethane PEGs to tube deterioration, resulting in substantially increased management demands to sustain patients' feeding and medication schedules.

Adult↗

PubMed1983

The significance of surface changes on explanted polyurethane pacemaker leads.

Although over 140,000 polyurethane leads have been implanted in humans, a controversy has recently arisen dealing with the significance of frequently detected irregularities on explanted insulator surfaces by scanning electron microscopy (SEM), and their relationship with lead failure. We therefore implanted ten, 6 Fr atrial polyurethane leads and an equal number of 4 Fr ventricular leads in dogs for a mean 26 +/- 2 and 29 +/- 2 weeks, respectively. Fourteen leads were removed utilizing metered force. The remaining leads were removed surgically without force at the termination of the study. Specimens were stored in saline prior to physical testing (tensile strength and elongation) of intravascular and extravascular lead segments. Similarly stored samples were prepared for SEM analysis. The polyurethane insulator disconnected from the electrode on forcible removal in three atrial and two ventricular leads (concordant connected from the electrode on forcible removal in three atrial and two ventricular leads (concordant for two pairs). There was no significant relationship between the results of physical testing and extraction force, lead size, integrity on removal, sample location or SEM scores. Chemical analysis of surface changes employing both x-ray and electron emission spectroscopy failed to reveal evidence of protein adsorption or liquid impregnation. Samples soaked in sodium hydroxide displayed the same SEM irregularities. The combined effects of fissuring and fluid absorption by polyurethane did not affect chronic anodal or cathodal thresholds. In conclusion, a clear relationship between chronic surface irregularities and the insulator function of polyurethane, its relationship between chronic surface irregularities and the insulator function of polyurethane, its integrity in situ, or its strength at explant has not been established by this relatively short-term study. On the other hand, a potential time-dependent impact of these changes on lead performance has not been excluded. Moreover, only a single species of medical grade polyurethane has been clinically evaluated. Thus, the ultimate place of polyurethane leads in pacing systems has yet to be determined.

Animals↗

PubMed2004

Effect on gait and socket comfort in unilateral trans-tibial amputees after exchange to a polyurethane concept.

UNLABELLED: Trans-tibial amputees with different indications for amputation often have stump problems. Many active amputees have limits in daily life and sports activities because of pressure ulcers, friction, allergic dermatitis or volume changes. Many methods and materials have been tried to make a well-fitted socket. A new polyurethane concept had been designed with a shock absorbing effect. The purpose of this prospective study was to compare a conventional suspension with a polyurethane concept with regard to the amputees' satisfaction, socket comfort, physical capacity and to analyse the long-term effect. The total material includes 29 unilateral trans-tibial amputees. They answered a questionnaire after 2 months use of the polyurethane concept and were interviewed after 3 and 5 years. After 3 years 22 amputees and after 5 years 20 amputees used the polyurethane concept. Gait was registered in 7 amputees. Speed and symmetry index (SI) for temporal, stride and kinematics variables were used to evaluate gait. The amputees reported that the polyurethane concept was better or much better in physical capacity in 117 (67%) and socket comfort was better or much better in 119 (82%) compared with the conventional suspension. There was no obvious symmetry difference in gait variables in speed, step length, step time or single support or in kinematics knee variables. The amputees tended to walk faster, decrease in symmetry in temporal and stride variables and increase in symmetry in kinematics variables with the polyurethane concept. After 5 years 6 had died and 20 amputees of the surviving 23 used the polyurethane concept. CONCLUSIONS: The polyurethane concept increased comfort considerably and physical activity increased when the trans-tibial amputees changed from conventional suspension. Gait registration was not useful to evaluate the amputees' satisfaction or socket comfort.

Adolescent↗

PubMedDate not supplied

Evaluation of the efficacy of a polyurethane condom: results from a randomized, controlled clinical trial.

CONTEXT: Condoms made of latex are not comfortable or appropriate for all consumers. Polyurethane condoms may provide a needed alternative. METHODS: In a double-masked study, 805 monogamous couples were randomized to use either the polyurethane condom or the latex condom for six months. Couples recorded the frequency of intercourse, of condom use and of breakage and slippage throughout the trial in coital diaries and in detailed reports on the first five uses. Breakage and slippage rates were determined, and typical-use and consistent-use pregnancy rates were calculated using life-table analysis, adjusted for use of emergency contraception. RESULTS: The six-month pregnancy rate during typical use (adjusted for use of emergency contraception) was 4.8% for the polyurethane condom and 6.3% for the latex condom. Similarly adjusted pregnancy rates during consistent use over six completed menstrual cycles--2.4% for the polyurethane condom and 1.1% for the latex condom--did not differ significantly. Clinical failure rates (including breakage and slippage occurring during either intercourse or withdrawal) were 8.5% for the polyurethane condom and 1.6% for the latex condom. In general, male participants were more satisfied with the latex condom, and users of latex were significantly less likely to drop out of the study for condom-related reasons than were users of polyurethane. CONCLUSIONS: Although polyurethane and latex condoms provide equivalent levels of contraceptive protection, the polyurethane condom's higher frequency of breakage and slippage suggests that this condom may confer less protection from sexually transmitted infections than does the latex condom.

Condoms↗

PubMed2006

[Animal study of intravascular gene therapy based on polyurethane implantable devices].

OBJECTIVE: To explore the feasibility of utilizing two implantable devices made from modified polyurethane films with antibody tethered replication-defective adenoviruses encoding for green fluorescent protein (AdGFP) as gene delivery platforms. METHODS: Intra-aortic button implants of collagen-coated polyurethane films with antibody tethered AdGFP were sutured into the infrarenal aorta of adult pigs and pulmonary valve leaflet in juvenile sheep was replaced by polyurethane pulmonary valve cusp replacement with antibody-tethered AdGFP. After seven days, the buttons, prosthetic leaflets, and their surrounding tissues were explanted and evaluated for biocompatibility and AdGFP-mediated gene transfer by fluorescent microscopy and PCR analysis. RESULTS: In vivo analysis of gene transfer from collagen-coated polyurethane films in pig infrarenal aorta implants, one week explants of the collagen-coated polyurethane films demonstrated (14.2 +/- 2.5)% of neointimal cells on the surface of the implant. In sheep pulmonary valve leaflet replacement studies, polyurethane films with antibody tethered AdGFP vector demonstrated (25.1 +/- 5.7)% of cells attached to polyurethane valve leaflets were transduced in one week. PCR analyses showed that GFP DNA was not detectable in blood or distal tissues. CONCLUSION: Site-specific intravascular delivery of adenoviral vectors for gene therapy can be achieved with these two kinds of polyurethane implants utilizing the antivector antibody tethering mechanism.

Adenoviridae↗

PubMed1997

Mechanical performance of polyurethane ureteral stents in vitro and ex vivo.

A serious problem associated with the use of ureteral stents is fracture in situ. Following clinical observations of fracture of polyurethane stents in vivo, this study examined the mechanical properties of 17 polyurethane stents (double-J containing drainage holes) retrieved from patients over a 24-week period of insertion. In addition, stents were immersed in human and artificial urine in an in vitro model at 37 degrees C to determine their general propensity to fracture. Mechanical properties of ureteral stents were examined using the standard ASTM D-412 tensile test and by the novel application of dynamic mechanical analysis (DMA). The ultimate tensile strength and elongation at break (but not the Young's modulus) of unused polyurethane stent sections containing side-drainage holes were greater than stent sections devoid of side-drainage holes. No correlations were observed between increased or decreased Young's modulus, ultimate tensile strength or elongation at break of polyurethane stents and their time of immersion in either human urine or artificial urine in simulated upper urinary tract conditions of 37 degrees C and 5% CO2. Similarly, no correlations were observed between Young's modulus, ultimate tensile strength or elongation of polyurethane stents and stent dwell time in situ. DMA of retrieved stents revealed that their tan delta value and storage modulus did not differ significantly from unused stents following dwell times in situ of up to 24 weeks. No changes in the glass transition temperatures were observed in retrieved stents. Although patient variation was observed, the results indicate that the polyurethane stents examined in vitro and following removal from patients did not exhibit any greater propensity to fracture than their unused counterparts. Fracture of retrieved polyurethane stents, arising in vivo and also during subsequent tensile testing, was observed to occur along the drainage holes, suggesting that elimination of these holes will reduce the incidence of polyurethane ureteral stent fracture in use.

Biocompatible Materials↗

PubMed1993

Cellular responses to silicone and polyurethane prosthetic surfaces.

Prosthetic devices composed of silicone or polyurethane are commonly used in surgery. These devices elicit a soft tissue reaction which may frequently be complicated by capsule formation. Histologically the capsule comprises both cellular (fibroblasts and endothelial cells (EC)) and matrix components (predominantly collagen type I). We hypothesized that the function of the cellular elements is altered by exposure to prosthetic materials and that this alteration contributes to capsule formation. To test this hypothesis, we utilized specific in vitro assays of cell function (attachment, proliferation, matrix gel contraction), which closely mimic in vivo cellular events, in order to define the responses of EC and fibroblasts to prosthetic surfaces (foam polyurethane, flat silicone, and textured silicone). Morphologic changes were evaluated by scanning electron microscopy (SEM). Attachment of both cell types to all prosthetic surfaces was significantly decreased compared to control (HUVEC: control, 55 +/- 1; foam polyurethane, 19 +/- 4*; flat silicone, 25 +/- 3*; textured silicone, 36 +/- 1*; fibroblast: control, 93 +/- 6; foam polyurethane, 21 +/- 4*; flat silicone, 57 +/- 5*; textured silicone, 44 +/- 5* (*P < 0.05 = significant; units, percentage spread)). Fibroblast proliferation was significantly decreased on foam polyurethane (0.1 +/- 0.03*) and textured silicone (0.18 +/- 0.05*), but not on flat silicone (0.79 +/- 0.2; control = 0.96 +/- .2). In contrast, HUVEC proliferation was significantly decreased on both silicone surfaces but not on polyurethane (units, cpm/cell; control, 0.26 +/- 0.05; foam polyurethane, 0.15 +/- 0.05; flat silicone, 0.08 +/- 0.03*; textured silicone, 0.02 +/- 0.01*).(ABSTRACT TRUNCATED AT 250 WORDS)

Cell Adhesion↗

PubMed1992

Effects of biostability and morphology on host response of polyurethane-based soft tissue implants.

Polyurethane has been found to be one of the most successful polymers for soft tissue applications. We have investigated the effect of material biostability and morphology on the host response of polyurethane-based soft tissue implants in rabbits. The polyurethane containing allophanate linkage was prepared by using hexamethylene diisocyanate, polypropylene glycol (400) and 1,4-butane diol. Biuret-based biostable polyurethanes were prepared by using hexamethylene diisocyanate, polytetramethylene glycol and trimethylol propane and water. Samples of circular button and rectangular specimens were implanted subcutaneously in rabbits in the paravertebral region for a post-implantation period of 9 months. Relatively larger polyurethane samples with different morphology elicit a varied tissue response with our candidate polyurethane materials. A favorable tissue response was observed with rectangularly shaped thin polyurethane. Giant cell reaction, absence of fibrous tissue encapsulation and degradation were noticed for the rectangular smooth samples at the end of post-implantation period of 9 months. No malignant changes were noticed in any of these samples.

Animals↗

PubMed1991

Effect of surface hydrophilicity on ex vivo blood compatibility of segmented polyurethanes.

The relationship between surface, bulk and ex vivo blood-contacting properties of segmented polyurethanes with various polyol soft segment was investigated. The polyols used in this study were poly(ethylene oxide), poly(tetramethylene oxide), hydrogenated poly(butadiene), poly(butadiene) and poly(dimethylsiloxane). The hard segment of these segmented polyurethanes was composed of 4,4' diphenylmethane diisocyanate and 1,4 butanediol, present at 50 wt%. An experimental polyurethane, Biostable PUR, which has shown excellent biostability, was used in this study. The segmented polyurethanes based on the hydrophobic polyols such as poly(dimethylsiloxane) and hydrogenated poly(butadiene) showed distinct microphase separation between hard and soft segments. X-ray photoelectron spectroscopy revealed the surface enrichment of the hydrophobic component at the air-solid interface. Dynamic contact angle measurements indicated that the poly(dimethylsiloxane)-based segmented polyurethane possessed a hydrophobic surface in water. The poly(dimethylsiloxane)-based segmented polyurethane had the lowest platelet adhesion among the segmented polyurethanes investigated in this study, whilst the platelet deposition on the poly(ethylene oxide)-based polymer increased with time.

Animals↗

PubMed1993

Autoclavable highly cross-linked polyurethane networks in ophthalmology.

Highly cross-linked aliphatic polyurethane networks have been prepared by the bulk step reaction of low molecular weight polyols and hexamethylenediisocyanate (HDI). These polyurethane networks are optically transparent, colourless and autoclavable amorphous glassy thermosets, which are suited for use in ophthalmic applications such as intraocular lenses and keratoprostheses. The properties of these glassy polyurethanes, obtained from the reaction of the low molecular weight polyols triisopropanolamine (TIPA) or tetrakis (2-hydroxypropyl)ethylenediamine (Quadrol) and HDI in stoichiometric proportions, have been investigated in more detail. The glassy Quadrol/HDI-based polyurethane exhibits a reduction in ultimate glass transition temperature from 85 to 48 degrees C by uptake of 1% of water, and good ultimate mechanical properties (tensile strength 80-85 MPa, elongation at break ca 15%, modulus ca 1.5 GPa). IR spectra of these hydrophobic polyurethane networks revealed the absence of an isocyanate absorption, indicating that all isocyanates, apparently, had reacted during the cross-linking reaction. The biocompatibility could be increased by grafting tethered polyacrylamide chains onto the surface during network formation. These transparent cross-linked polyurethanes did not transmit UV light up to 400 nm, by incorporation of a small amount of the UV absorbing chromophore Coumarin 102, and could be sterilized simply by autoclaving. They were implanted in rabbit eyes, either in the form of small circular disks or in the form of a keratoprosthesis (artificial cornea). It was shown that the material was well tolerated by the rabbit eyes. Serious opacification of the cornea, a direct result of an adverse reaction to the implant, was never seen. Even 1 yr after implantation of a polyurethane keratoprosthesis the eye was still 'quiet'.

Animals↗

PubMed1995

Effect of sulphonate incorporation on in vitro leucocyte adhesion to polyurethanes.

A series of poly(tetramethylene oxide)-based polyurethane block copolymers was synthesized with varying levels of sulphonate ion incorporated in the hard segment block. Static in vitro adhesion of polymorphonuclear leucocytes (PMNs) on the underivatized and propyl sulphonate-grafted polyurethanes was investigated. The effect of plasma proteins on PMN adhesion to the polymers was also examined. The number of adherent cells on the sulphonated polyurethane surfaces was significantly higher than on the underivatized polyurethane under all conditions. The adherent PMNs on sulphonated polyurethanes showed increased cell spreading compared to the underivatized base polyurethane. Increasing the level of sulphonate incorporation from 5 to 17 mol% had no effect on the extent of cell adhesion. The presence of preadsorbed proteins generally led to a decrease in the number of adherent PMNs on the surfaces. However, the presence of plasma proteins in the suspension medium had no effect on the degree of leucocyte adhesion to the sulphonated polyurethanes.

Absorption↗

PubMed1999

A prospective, randomized, controlled trial comparing transparent polyurethane and hydrocolloid dressings for central venous catheters.

BACKGROUND: This study was undertaken to determine the frequency of skin colonization, hub colonization, and central venous catheter colonization in transparent hydrocolloid versus standard polyurethane dressings. METHODS: Adult patients requiring the insertion of a multilumen central venous catheter in an intensive care unit were randomized to receive either a standard polyurethane dressing or a transparent hydrocolloid dressing. Cultures were obtained from 125 skin insertion sites, 141 catheter hubs, 128 catheter tips, and blood samples from 132 patients. Extensive data on patient and catheter characteristics were collected. RESULTS: Skin and hub cultures revealed no significant difference in degree of colonization. However, the hydrocolloid group had a significantly higher level of catheter colonization than the polyurethane group (P =.048). Conversely, there was a significantly higher frequency of positive blood cultures in the polyurethane group (P =.03), although the majority were considered to be potential contaminants. There were only 6 cases in which the same species was simultaneously isolated from a positive blood culture and a colonized catheter, 5 from the hydrocolloid group and 1 from the polyurethane group. CONCLUSIONS: The results of this study suggest that an increased risk of catheter colonization is associated with the use of hydrocolloid dressings, despite previous research suggesting that they significantly reduce microbial growth compared with standard polyurethane. The clinical significance of increased numbers of positive blood cultures in the polyurethane group requires further examination, although distinguishing between contamination and true infection in intensive care settings continues to be methodologically challenging. Further studies are required to determine whether these findings are generalizable across different study settings and whether similar outcomes are obtained when different brands of hydrocolloid dressing are used.

Adolescent↗