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At least 991 records · Page 55Linked to original sources

PubMed1992

Evaluation of an in-line bipolar polyurethane ventricular pacing lead.

A study was undertaken to evaluate the performance of the Medtronic 4012 polyurethane in-line bipolar pacing electrode. One hundred twenty six patients implanted with the 4012 lead were followed by our clinic with 116 of these leads implanted at our institution. Patients were followed a minimum of every 4 months. Testing included the performance of stimulation thresholds, sensing thresholds, and provocative maneuvers to evaluate for myopotential inhibition testing a minimum of every eight months. There were 12 documented lead failures of the total 126 patients. Further analysis was limited to the ten failures occurring in the 116 leads implanted at our center. All ten failed leads utilized the suture anchoring sleeve. Six of the leads were left cephalic implants, three were right cephalic, and one was right subclavian. Manifestations of failure included: seven oversensing abnormalities, three undersensing, four loss of ventricular capture, one premature end of service, four lead impedance decreases to < 250 omega and some presentations in combination. No leads were explanted for evaluation. The Kaplan-Meier product limit method was used to estimate the time to lead failure. The probability of not experiencing a lead failure within the first 4 years of implant is estimated to be 0.9103 (SE = 0.0338). Pacemaker dependent patients implanted with the 4012 lead should be given special consideration for prophylactic replacement.

Actuarial Analysis↗

PubMed1992

A multicenter experience with a bipolar tined polyurethane ventricular lead.

A multicenter study was undertaken to determine the failure rate of a specific polyurethane bipolar tined pacing lead, the Medtronic 4012 pacing lead. Six centers in the United States and Canada implanted 1,190 Medtronic 4012 pacing leads. The study was designed to determine the probability and clinical manifestations of lead failure. Only failures compatible with an insulation problem were included. The probability of a 4012 lead failure by Kaplan-Meier analysis was 20.9% at 6 years after implantation. Failures were manifested as sensing abnormalities, failure to capture, early battery depletion, and significant decrease in measured impedance compared with the previous impedance measurements. Of the 95 definite lead failures, 16 (16.8%) were associated with symptoms similar to those experienced before pacemaker placement. The observed failure rate is unacceptable, and strong consideration should be given to replacing the 4012 pacing lead in pacemaker-dependent patients and closely monitoring nondependent patients.

Aged↗

PubMed1994

Clinical surveillance of an active fixation, bipolar, polyurethane insulated pacing lead, Part II: The ventricular lead.

Since 1989, 72 Telectronics 330-201 active fixation, polyurethane insulated ventricular leads (Accufix) have been implanted at the Mayo Clinic. There were four (5.6%) acute lead related complications (perforation, microdislodgment, and macrodislodgment), three of which led to early reoperation. Over a follow-up time of up to 2.7 years (median 9.4 months), there were six (8.3%) chronic lead related complications but no failures of lead material. Most of these complications developed during the first month, and half of them were transient, with documented improvement later. Two patients (2.8%) required reoperation for chronic complications. At follow-up examination of the pacing thresholds, usually performed about 3 months after implantation, 14.3% of the examined patients had high pacing thresholds necessitating high-output programming. The mechanisms and later evolution of this phenomenon should be further evaluated.

Adult↗

PubMed1994

Clinical surveillance of an active fixation, bipolar, polyurethane insulated pacing lead, Part I: The atrial lead.

Since 1989, 168 Telectronics model 330-801 active fixation, polyurethane insulated atrial leads (Accufix) have been implanted at the Mayo Clinic. There were four (2.4%) acute lead related complications, (i.e., perforation, microdislodgment, and pericarditis). Over a median follow-up time of 7.6 months (up to 2.7 years), there were 14 (8.3%) chronic complications, including 1 instance (0.6%) of definite lead failure. Most of these complications were early (within the first month) and transient. Four patients (2.4%) required reoperation for chronic complications. During follow-up, 23% of the examined patients had high pacing thresholds, most at about 3 months after implantation, necessitating high-output programming. The exact mechanism and natural history of this phenomenon should be further investigated.

Adolescent↗

PubMed1995

Multicenter experience with a bipolar tined polyurethane ventricular lead.

A multicenter study was undertaken to determine the failure rate of a specific bipolar tined polyurethane ventricular pacing lead, the Medtronic 4004/4004M pacing lead. Seven centers in the United States and Canada implanted 586 Medtronic 4004/4004M pacing leads. The study was designed to determine the probability and clinical manifestations of lead failure. Only failures compatible with an insulation problem were included. The Kaplan-Meier estimate of the percentage of 4004/4004M lead failures within 4 years after implantation was 14.1% (95% confidence interval: 8.5%-19.3%). Failures were manifested as sensing abnormalities, failure to capture, early battery depletion, and significant decrease in measured impedance compared with previous impedance measurements. The observed rate of failure is unacceptable, and strong consideration should be given to replacing the 4004/4004M pacing lead in pacemaker dependent patients and closely monitoring nondependent patients.

Adolescent↗

PubMed1998

Venous access thrombosis detected by transcutaneous vascular ultrasound in patients with single-polyurethane-lead permanent pacemaker.

In order to assess the incidence of significant venous thrombosis after transvenous permanent pacemaker implantation, transcutaneous ultrasound studies were performed in 109 consecutive patients with single-polyurethane-lead pacemakers. Ultrasonic evaluation was found to be a good noninvasive method in assessing the veins. Six patients (5.5%) were found to have significant venous obstruction in the subclavian vein. However, none of them were symptomatic. No difference in the incidence of venous obstruction was found, based on the age, duration of implantation, operative technique, potentially thrombogenic factors including atrial fibrillation, diabeties mellitus, hypertension, heart failure and end-stage renal disease.

Adult↗

PubMed1992

Occupational dermatitis from exposure to polyurethane chemicals.

In addition to asthma, contact dermatitis may also develop from occupational contact with polyurethane (PU) chemicals. 6 cases of allergic contact dermatitis from exposure to PU chemicals were diagnosed in 1974-1990. The present paper summarizes the results and gives detailed descriptions of 3 such patients. 3 patients were allergic to 5 different diisocyanates (DICs), including 4,4'-diphenylmethane DIC (MDI), toluene DIC (TDI), 1,6-hexamethylene DIC (HID), and furthermore to diaminodiphenylmethane (MDA). 3 patients were sensitized by exposure to MDI. 2 of these reacted to MDI and MDA, and 1 to TDI in addition. 1 of the 3 patients reacted only to MDA, possibly formed by hydrolysis of MDI. Primary sensitization to MDA and cross-allergy to MDI could explain the reactions of the patients exposed to MDI, but separate sensitization may also be possible. Patch tests with fresh petrolatum (pet.) mixtures were first made and a 2% concentration was recommended for MDI and TDI. In order to determine the stability of DIC test substances, the last 2 patients were tested with old test substances. Tests with MDI 1.5% pet. and TDI 1.5% pet., 5.5 months and 15.5 months old, were positive. The results suggest that, when allergy to PU chemicals is suspected, patch tests should include, in addition to MDA, at least MDI and TDI 1.5-2% pet. They also suggest that test substances can be used for over a year, and that allergy to MDA may point to MDI exposure contained in PU chemicals.

Adult↗

PubMed2003

Compressive and shear properties of commercially available polyurethane foams.

BACKGROUND: The shear properties of rigid polyurethane (PU-R) foams, routinely used to simulate cancellous bone, are not well characterized. METHOD OF APPROACH: The present assessment of the shear and compressive properties of four grades of Sawbones "Rigid cellular" PU-R foam tested 20 mm gauge diameter dumb-bell specimens in torsion and under axial loading. RESULTS: Shear moduli ranged from 13.3 to 99.7 MPa, shear strengths from 0.7 MPa to 4.2 MPa. Compressive yield strains varied little with density while shear yield strains had peak values with "200 kgm-3" grade. CONCLUSIONS: PU-R foams may be used to simulate the elastic but not failure properties of cancellous bone.

Biocompatible Materials↗

PubMed1967

Segmented polyurethane: a new elastomer for biomedical applications.

A segmented polyurethane elastomer, originally developed for elastic thread, is now being used for molded prostheses. Performance of this material when used for components of a heart-assist system warrants a thorough investigation of its effectiveness in a variety of biomedical devices.

Animals↗

PubMed1976

Comparison between numbers and kinds of freshwater protozoans colonizing autoclaved and unautoclaved polyurethane foam substrates.

Autoclaved and unautoclaved polyurethane substrates were placed in Douglas Lake, Michigan, to determine whether fatty amines produced by autoclaving affected the colonization process. These results indicate that there was no major difference in the numbers of colonizing species in either kind of substrate. The kinds of species showed considerable overlap among the categories of substrate.

Animals↗

PubMed1975

Inhibition of microbial growth by fatty amine catalysts from polyurethane foam test tube plugs.

When polyurethane foam test tube plugs are autoclaved, they release volatile fatty amines that inhibit the growth of some microorganisms. The chemical structures of these amines were determined by the use of a gas chromatograph-mass spectrometer. They are catalysts used to produce the foam. The problem of contaminating growth media with toxic substances released from polymeric materials is discussed.

Acinetobacter↗

PubMed1987

Staphylococcal adherence to polyvinyl chloride and heparin-bonded polyurethane catheters is species dependent and enhanced by fibronectin.

Intravenous hyperalimentation has improved the survival of premature infants. However, long-term placement of intravenous catheters may result in the development of catheter-related sepsis. Fibronectin in plasma contains binding sites for staphylococcal species as well as marked affinity for inert plastics and therefore may provide a substrate for bacterial adherence to indwelling catheters. We determined the adherence of labeled [( 3H]leucine) coagulase-positive (CPS) and coagulase-negative (CNS) staphylococci to untreated and fibronectin-coated polyvinyl chloride (PVC) and heparin-bonded polyurethane (HBP) catheter segments and quantitated the binding of 14C-labeled, purified fibronectin to these catheters. PVC catheter segments bound significantly more CNS than CPS (P less than 0.05), while HBP catheters bound more CPS than CNS (P less than 0.05). Fibronectin significantly increased the adherence of CPS to PVC catheters (P less than 0.05) and CNS to HBP catheters (P less than 0.05). PVC catheters bound more fibronectin (P less than 0.0001) than did HBP catheters. Catheter composition may influence the spectrum of nosocomial pathogens to which infants are susceptible through different bacterial adherences and interactions with adhesive proteins.

Bacterial Adhesion↗

PubMed1975

Assessment of anti-inflammatory drugs in the rat using subcutaneous implants of polyurethane foam impregnated with dead tubercle bacilli.

The fluid and cellular phases of inflammatory resonse have been measured using a technique employing subcutaneous implantation of polyurethane foam cubes impregnated with heat-killed Mycobacterium tuberculosis. Phenylbutazone, azathioprine, aspirin, cyclophosphamide, and prednisolone suppressed fluid response, whereas sodium aurothiomalate, hydroxychloroquine, and D-penicillamine had no effect. All the drugs used suppressed the infiltration of inflammatory cells into the cubes.

Animals↗

PubMed1983

Assessment of nonsteroidal anti-inflammatory drug combinations by the polyurethane sponge implantation model in the rat.

The anti-inflammatory effect of single doses and combinations of aspirin and commonly used nonsteroidal anti-inflammatory drugs was investigated by the polyurethane sponge implantation model of acute inflammation. Dose response curves were performed to delineate a suppressive (high) and nonsuppressive (low) dose of each drug prior to studying these doses in combination with aspirin. The results suggest that a combination of aspirin in either high or low dose does not increase the anti-inflammatory effect of other nonsteroidal anti-inflammatory drugs in this model of inflammation.

Animals↗

PubMed1992

Diurnal variation in peak expiratory flow rate among workers exposed to toluene diisocyanate in the polyurethane foam manufacturing industry.

The diurnal variation in peak expiratory flow rate (PEFR) was studied in 26 mixers from eight factories making polyurethane foam, who were exposed to toluene diisocyanate (TDI), and 26 unexposed controls matched for age, race, and smoking. They were all men. The mean diurnal variation in PEFR of the mixers was 6.2%, which was significantly higher than the 4.3% for controls. Six mixers had a diurnal variation of greater than 15% on at least one day compared with none among the controls. There was, however, no overt cause of occupational asthma. All but one of the 24 environmental samples taken exceeded the short term exposure limit of 0.02 ppm for TDI. This accounted for the high prevalence (50%) of irritative symptoms such as cough and eye irritation. Forced expiratory volume in one second (FEV1) and FEV1/forced vital capacity (FVC) (%) was negatively correlated with duration of exposure to TDI. Foam workers may still have high exposure to TDI, high prevalence of irritative symptoms, increased diurnal variation in PEFR and evidence of chronic airway obstruction, particularly in those with greater than or equal to 10 years of exposure.

Adult↗

PubMed1993

Incidence of cancer and exposure to toluene diisocyanate and methylene diphenyldiisocyanate: a cohort based case-referent study in the polyurethane foam manufacturing industry.

OBJECTIVE: To assess the association between occupational exposure to toluene diisocyanate or methylene diphenyldiisocyanate and risk of cancer. DESIGN: A cohort based case-referent study. STUDY BASE: 7023 subjects employed during the period 1958 to 1987 in nine Swedish polyurethane foam manufacturing plants. MAIN OUTCOME MEASURES: Odds ratios adjusted with respect to the matching factors (age at risk, calendar year at risk, sex, and plant), calculated from the conditional logistic regression model. RESULTS: A non-significant association was found between high exposure to isocyanates and prostate cancer (OR 2.66, 90% confidence interval (90% CI) 0.39-18.1), which was not enhanced when an induction latency period of 10 years was applied. An association between isocyanate exposure and colon cancer was even weaker. No associations were seen for non-Hodgkin's lymphoma and rectal cancer. CONCLUSIONS: The tentative associations, derived from a previous cohort study, between isocyanate exposure and excess risk for non-Hodgkin's lymphoma and rectal cancer were not supported. Instead, non-significant associations with prostate cancer, and possibly colon cancer, were seen.

Case-Control Studies↗

PubMed1993

Mortality and cancer morbidity of production workers in the United Kingdom flexible polyurethane foam industry.

OBJECTIVE: To describe cause specific mortality and site specific cancer morbidity among workers employed in factories that produce polyurethane foams, and to determine if any part of the experience may be due to occupation, and in particular to exposure to diisocyanates. DESIGN: Historical prospective cohort study. SETTING: 11 factories in England and Wales. SUBJECTS: 8288 male and female production employees with some employment in the period 1958-79, and with a minimum period of employment of six months. MAIN OUTCOME MEASURES: Observed and expected numbers of deaths for the period 1958-88, and corresponding figures for cancer registrations for the period 1971-86. RESULTS: Compared with the general population of England and Wales, standardised mortality ratios (SMRs) for all causes and all neoplasms were 97 (observed deaths (Obs) 816) and 88 (Obs 221) respectively. Statistically significant excesses were found among women for cancer of the pancreas (expected deaths (Exp) 2.2, Obs 6, SMR 271, 95% CI 100-595) and cancer of the lung (Exp 9.1, Obs 16, SMR 176, 95% CI 100-285). Similar excesses were not found among male employees, and the SMRs for cancers of the lung and pancreas among the total study population were 100 (Obs 81) and 136 (Obs 14) respectively. Overall incidence of cancer was also below expectation (SRR 94, Obs 277), although statistically significant excesses among women were found for cancers of the larynx and kidney, based on three and four cases respectively. Incident cancers of the lung and pancreas among women were also in excess, although these findings were not independent of the findings for mortality. Poison regression did not indicate that ever having been employed in jobs attracting either higher or lower exposure to isocyanates was a risk factor for the mentioned cancers. A nested case-control design was used to investigate any associations with nine other occupational exposures. No statistically significant association was found. CONCLUSIONS: In general, cancer rates in this population were lower than those for the general population. All increased cancer rates among women occurred at sites of cancer known to be related to cigarette smoking, and these excesses are probably due to a combination of cigarette smoking, chance, and factors unrelated to the industry under study.

Adolescent↗

PubMed1996

Biomarkers of exposure, antibodies, and respiratory symptoms in workers heating polyurethane glue.

OBJECTIVES: The pathogenic basis of respiratory disorders associated with isocyanates are still obscure. One reason for this is the lack of good estimates of human exposure. In this study exposure was estimated by measurement of isocyanate metabolites in biological samples. METHODS: In a factory using isocyanate based polyurethane (PUR) glue, isocyanate concentrations in air were measured by liquid chromatography. Samples from 174 employees were analysed for metabolites of 4,4'-methylene diphenyl diisocyanate (MDI) in plasma (P-MDX) and urine (U-MDX). After hydrolysis, 4,4'-methylenedianiline was measured by gas chromatography-mass spectrometry (GC-MS). The employees were screened for work related respiratory symptoms and tested for specific immunoglobulin E (IgE) and IgG antibodies directed against isocyanate conjugated to human serum albumin. RESULTS: The time weighted isocyanate concentrations in air were low (MDI < 0.2-7; hexamethylene diisocyanate (HDI) < 0.1-0.7; 2,6-toluene diisocyanate (TDI) < 0.1 microgram/m3). All subjects had detectable P-MDX and U-MDX. There were significant associations between the estimates of exposure to thermal degradation products of an MDI based glue and P-MDX (range < or = 0.10-5.5 micrograms/l); and U-MDX (< or = 0.04-5.0 micrograms/g creatinine); in cases of heavy exposure. P-MDX and U-MDX were associated with each other (r = 0.64; P = 0.0001), work related symptoms (P-MDX: P = 0.03; Mann-Whitney U test), and serum concentrations of MDI specific IgG antibodies (r = 0.26; P = 0.0007). Unexpectedly, high P-MDX and U-MDX concentrations were also encountered in workers cutting textile (P-MDX 2.4-4.5 micrograms/l; U-MDX 0.81-3.8 micrograms/g creatinine); the reason is still unknown. Equally unexpected, there were significant negative associations between P-MDX and liver function tests. CONCLUSIONS: The results clearly show the value of biomarkers for isocyanate exposure; in particular, P-MDX is useful. Further, these results show the risk connected with thermal degradation of PUR.

Adhesives↗