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Results for “Randomized Response Technic”

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PubMed1992

Dental health care workers' response to the HIV epidemic.

Random samples of Minnesota DHCWs were surveyed in late 1989 regarding HIV-related and infection control KAPs. Response rates were: dentists 69% (438/631); hygienists 73% (439/603); and assistants 56% (384/691). More than 50% of DHCWs said they did not have sufficient information to safely and effectively provide care for HIV-infected patients. Use of infection control techniques varied considerably. Parenteral injuries were relatively high, but only 5% of DHCWs believed they could have been exposed to HIV from these occurrences, and few DHCWs sought medical evaluation. Less than 45% of offices had a blood/body fluid exposure staff protocol, and few offices had a policy for HIV-infected staff. Nearly twice as many DHCWs said offices have an ethical versus a legal duty to treat HIV-infected persons. Low percentages of DHCWs believed the private practice dental office is the best place to treat HIV-infected patients, but approximately 50% said they would provide care. Twenty percent indicated that a diagnosed HIV-infected person had been seen at their office. Seventy-six percent said staff had been uncomfortable treating HIV-infected patients, 14% said staff had refused to treat, and 10% said referrals were difficult. DHCWs exhibited substantial improvements in their HIV-related KAPs compared to previous surveys. Nevertheless, additional cognitive and behavioral changes are necessary to ensure that all DHCWs provide care with the highest technical, legal, and ethical standards for all patients.

Acquired Immunodeficiency Syndrome↗

PubMed2004

Comet-FISH using peptide nucleic acid probes detects telomeric repeats in DNA damaged by bleomycin and mitomycin C proportional to general DNA damage.

For the optimal use of anticancer drugs a knowledge of the whole spectrum of side-effects is required. A potential hazard, so far only scarcely investigated, is uncontrolled effects of drugs such as bleomycin (BLM) and mitomycin C (MMC) on telomere shortening in non-cancerous tissues of the treated person. For the first time, directly labelled telomere-specific peptide nucleic acid (PNA) hybridization probes were applied in comet-FISH to detect DNA fragmentation on an intermediate scale. The effects of BLM and MMC were measured in peripheral blood cells of three human volunteers, following ex vivo incubation. Fragmentation of telomeres and subtelomeric regions was highly specifically detected by the comet-FISH assay, a combination of the comet assay and fluorescence in situ hybridization. As a technical detail, the effects of the hybridization procedure have been studied on the level of single comets. Image analysis before and after the hybridization process reveals a small decrease in the detected fragmented DNA, probably due to diffusion of small fragments. It could not only be shown that both drugs actually induce breaks in telomere-associated DNA, but also that the comet-FISH technique, as a quantitative approach, is a useful tool for the detection and evaluation of the role of sequence-specific DNA damage after mutagenic action. The breakage frequency for DNA of or adjacent to telomeric repeats was found to be proportional to that of the total DNA, which hints at random induction of DNA breaks by BLM and MMC. In terms of therapy, the results indicate that no over- or under-proportional effects on telomeres of BLM or MMC need be expected.

Antibiotics, Antineoplastic↗

PubMed1997

Placebo-controlled biofeedback blood pressure effect in hypertensive humans.

The role of biofeedback in blood pressure control remains ill-defined because of nonspecific (placebo) effects, small study numbers, and the technical limitations of continuous pressure feedback. Clarification of its potential is awaited by those seeking a nonpharmacological approach to blood pressure control. This study examines the capability for systolic pressure lowering of 5 mm Hg or more using continuous pressure feedback in a statistical sample of untreated, well-characterized, mildly hypertensive individuals. Subjects were randomized in a double-blind study to active or placebo biofeedback. Placebo consisted of a modified contingency approach, using a partial disguise based on a digital high pass filter with 15 elements. Blood pressure-lowering capability was assessed during two laboratory sessions. Continuous visual feedback resulted in 11 of 28 subjects on active treatment and 12 of 28 on placebo treatment lowering their systolic pressure by 5 mm Hg or more (11 +/- 5.6 and 12 +/- 8.4 mm Hg, respectively; P = NS). Prestudy pressure was well-matched (153 +/- 9/97 +/- 4 and 154 +/- 8/98 +/- 4 mm Hg, respectively). An initial small difference in diurnal profile did not change. These findings indicate that among mildly hypertensive individuals, almost half can lower systolic pressure at will for short periods. This capability is independent of the real or placebo nature of the feedback signal. We conclude that there is no specific short-term biofeedback pressure-lowering capability in hypertensive individuals. Further exploration is needed to determine whether specific components of the placebo effect can be delineated, whether personality characteristics influence the response, and whether further biofeedback training can alter the outcome.

Adult↗

PubMedDate not supplied

Genotypic drug resistance interpretation systems--the cutting edge of antiretroviral therapy.

The technical quality of genotypic and phenotypic drug resistance testing has considerably improved, and therefore the major challenge now lies in the interpretation of drug resistance. This is due to several facts: (i) in times of combination therapy, the effect of drug resistance-associated mutations cannot be considered independently, (ii) many additive and subtractive interactions between mutations exist, and resistant strains may exhibit varying degrees of cross-resistance, (iii) the phenotype cannot adequately determine slight, but clinically relevant, differences for those drugs with a narrow range of resistance, and (iv) pharmacokinetic interactions may shift relevant levels of drug resistance. Genotypic drug resistance interpretation systems are designed to solve these problems. Rule-based systems incorporate current knowledge about correlations between genotype, phenotype and clinical response. Database-driven systems use the information provided by paired geno- and phenotypic data, applying database matching search or bioinformatic approaches. For detailed comparison, 11 interpretation systems were selected which present a comprehensive system for most of the available drugs, can easily be accessed via the Internet and are regularly updated. The systems were characterized for the source data, access, input, output, and availability of clinical studies. For further comparison, existing clinical databases should be merged into one large database to allow competition between the systems. This may also solve the burning problem of clinically relevant cut-offs. Head-to-head comparisons of interpretation systems require large prospective randomized trials in which only the interpretation system is different between groups, before a consensus can be achieved for the best antiretroviral therapy of the individual patient.

Algorithms↗

PubMed2000

Inverse planning incorporating organ motion.

Accurate targeting is important in intensity-modulated radiation therapy (IMRT). The positional uncertainties of structures with respect to the external beams arise in part from random organ motion and patient setup errors. While it is important to improve immobilization and reduce the influence of organ motion, the residual effects should be included in the IMRT plan design. Current inverse planning algorithms follow the conventional approach and include uncertainties by assuming population-based margins to the target and sensitive structures. Margin around a structure represents a "hard boundary" and the fact that a structure has a spatial probability distribution has been completely ignored. With increasing understanding of spatial uncertainties of structures and the technical capability of fine-tuning the dose distribution on an individual beamlet level in IMRT, it seems timely and important to fully utilize the information in the planning process. This will reduce the "effective" margins of the structures and facilitate dose escalation. Instead of specifying a "hard margin," we describe an inverse planning algorithm which takes into consideration positional uncertainty in terms of spatial probability distribution. The algorithm was demonstrated by assuming that the random organ motion can be represented by a three-dimensional Gaussian distribution function. Other probability distributions can be dealt with similarly. In particular, the commonly used "hard margin" is a special case of the current approach with a uniform probability distribution within a specified range. The algorithm was applied to plan treatment for a prostate case and a pancreatic case. The results were compared with those obtained by adding a margin to the clinical target volume. Better sparing of the sensitive structures were obtained in both cases using the proposed method for approximately the same target coverage.

Algorithms↗

PubMed1996

Technical and biological conditions influencing the functional APC resistance test.

Poor anticoagulant response to APC is conveniently screened by a commercially available functional test (Coatest APC Resistance) allowing identification of APC-resistant patients. These patients may then be genotyped with respect to factor V, the Arg -> Gln mutation being the principle cause of APC resistance. However, determination of phenotype generally precedes that of genotype, and the need for an "abnormality threshold" prompted a study of inter-batch variations and the clinical conditions associated with an altered APC response. The response to APC was assessed twice in plasma from 111 patients using two of four successive kit batches. A modest but significant inter-batch variability was observed. At the same time, we also tested 130 patients with retinal venous occlusion (RVO), 28 patients with glaucoma and 24 normal volunteers. The APCaPTT/aPTT ratio was found to be lower in the presence of elevated thrombin-antithrombin complexes (r = 0.167, p < 0.02) and low blood viscosity (at high shear rate: r = 0.305, p < 0.0001) independently of any alteration in genotype.

Aged↗

PubMed2006

Hypoxic abdominal stop-flow perfusion in the treatment of advanced pancreatic cancer: a phase II evaluation/trial.

In the past decade, some authors have reported objective responses and prolonged median survival times using hypoxic abdominal perfusion (HAP) for the treatment of advanced pancreatic cancer. However, these promising results have not been confirmed by others, making it difficult to define the effectiveness of this loco-regional chemotherapy. The aim of this study, therefore, was to evaluate the response rate, time to disease progression and overall survival following HAP treatment of 22 consecutive patients with advanced pancreatic tumors. Within the period from 1999 to 2003, 22 patients with histological diagnosis of unresectable stage III/IV pancreatic cancer, not responsive to systemic chemotherapy, were treated with mitomycin C 30mg/m(2) and cisplatin 60mg/m(2) by HAP (stop flow technique). Immediately after perfusion, hemofiltration was performed to reduce systemic side toxic effects. Responses were assessed by CT-scan 30days from the end of treatment. Minor or partial responses were confirmed by a second CT-scan 4weeks later. Following 26 treatment cycles no death or technical complications were recorded; four patients (18.2%) achieved a partial response, 2 (9.1%) a minimal response and 13 (59.1%) stable disease. The remaining 3 patients (13.6%) showed progression of the disease. The median time to disease progression was 3 months (range 1-10). The median survival time from the start of regional chemotherapy was 6 months (range 1.9-16), with a 1-year survival rate of 9%. Our data show that HAP is a relatively effective second-line treatment for advanced stage pancreatic cancer with a low complication rate. We do not concur with the opinion of others that HAP is an inactive treatment approach. However, taking into account the invasiveness of this procedure, and associated morbidity and cost, HAP would not appear to be preferable to less invasive loco-regional chemotherapeutic alternatives.

Aged↗

PubMed2006

Metallosis after contemporary metal-on-metal total hip arthroplasty. Five to nine-year follow-up.

BACKGROUND: Authors of recent studies have reported early periprosthetic osteolysis in patients who have been treated with a contemporary metal-on-metal total hip arthroplasty and have suggested that metal hypersensitivity associated with an immunologic response to metal may be of etiologic importance. We evaluated the results and histologic findings in patients who had undergone revision of a failed contemporary metal-on-metal total hip arthroplasty. METHODS: Two hundred and seventeen total hip arthroplasties (SL-Plus stem and Bicon-Plus cup) with a Sikomet metal-on-metal articulation were implanted in 194 consecutive patients, and the results were retrospectively reviewed at a mean of seventy-seven months postoperatively. Clinical follow-up with the Harris hip score and plain radiographic evaluation were performed. Periprosthetic tissues from fourteen hips that had undergone revision arthroplasty were subjected to histologic analysis. RESULTS: The mean Harris hip score improved from 45 points preoperatively to 88 points at the final evaluation. Fourteen hips (6.5%) were revised: nine because of aseptic loosening, two because of technical failure, and three because of septic failure. Histologic examination of the retrieved periprosthetic tissues from the eleven patients who had undergone revision because of aseptic loosening or technical failure showed metallosis and extensive lymphocytic and plasma-cell infiltration around the metal debris. With removal of the component because of aseptic loosening as the end point, survivorship was 93% for the stem and 98% for the cup. CONCLUSIONS: Our findings are in agreement with those in recent publications and support the possibility that periprosthetic osteolysis and aseptic loosening in hips with a metal-on-metal articulation are possibly associated with hypersensitivity to metal debris. Prospective, comparative, randomized long-term studies are necessary to determine the cause(s) of loosening of prostheses with this particular articulation.

Adult↗

PubMed1991

[Real time collection of pain profile in treatment with ibuprofen].

In an open three-center pilot study, 17 patients suffering from chronic persistent pain syndrome, due to osteoarthritis of the hip and knee or spondylarthrosis, were treated orally with 1800-2400 mg Ibuprofen per day for 3 weeks. The chronic pain syndrome and joint status were assessed by the physician at the beginning, and after 7, 14 and 21 days. Self-assessments were made by the patients six times daily during the full study period by means of battery-driven electronic diaries (E.D.). The data entered by the patients were stored in the E.D. and after online transfer, processed and evaluated in a PC using appropriate software programs. E.D. were returned by 16 of 17 patients for evaluation. The technical functioning of the instrument was perfect; its use was accepted by patients and physicians. The closely-meshed real-time recording of pain course and other subjective data, such as adverse events or medication, etc., enables the physician to calculate more exactly and reliably improvement rates, as well as to carry out prognostic trend analyses and individual benefit-risk-ratio estimates. By comparing different kinds of data, each entered at the same time, plausibility checks are possible. The procedure presented here is considered to be a new valuable tool for reviewing subjective data from clinical drug trials.

Adult↗

PubMed2006

Chlorfenapyr and mallard ducks: overview, study design, macroscopic effects, and analytical chemistry.

The first commercial pesticide derived from a class of compounds known as halogenated pyrroles was registered for use in the United States in 2001. Chlorfenapyr degrades slowly in soil, sediment, and water and is highly toxic to birds. Information on biochemical or histological endpoints in birds is lacking; therefore, a two-year study was conducted to provide information needed to develop diagnostic criteria for chlorfenapyr toxicosis. In the first year, male mallard ducks were fed concentrations of 0, 2, 5, or 10 ppm technical chlorfenapyr or 5 ppm of a formulated product in their diet during a 10-week chronic exposure study. Survival, body weight, feed consumption (removal), behavior, and molt progression were monitored. Feed and liver were analyzed for chlorfenapyr and two metabolites. Five of 10 ducks in the 10-ppm group died, and neurotoxic effects were observed in the 5- and 10-ppm groups. Feed removal increased for ducks receiving chlorfenapyr and body weights of 5- and 10-ppm ducks were reduced. Loss of body fat, muscle atrophy, and bile retention were suggestive of metabolic disruption or a decreased ability to digest and absorb nutrients. Liver and kidney weights and liver and kidney weight/body weight ratios exhibited a positive response to concentrations of chlorfenapyr in the diet. Emaciation and elevated organ weight/body weight ratios are candidates for a suite of indicators of chronic chlorfenapyr exposure. Liver is the preferred tissue for chemical confirmation of exposure.

Animals↗

PubMed2005

Sudden cardiac death unresponsive to implantable defibrillator therapy: an urgent target for clinicians, industry and government.

A major expansion in utilization of implantable cardioverter-defibrillators (ICDs) is anticipated based on the results of randomized clinical trials (RCT) that demonstrate increased survival in a sizable population of patients with reduced left ventricular function. However, if RCT accurately reflect clinical practice, then a substantial proportion of patients will die suddenly despite ICD implantation. ICD-unresponsive sudden cardiac death (SCD) has been recognized since the initial ICD experience. Yet, despite 25 years of technical advances, the frequency of ICD-unresponsive SCD has not declined. Pooled analysis of RCT indicates a crude rate of ICD-unresponsive SCD of 5%. This may not cause alarm in an average practice, but it comprises about 30% of cardiac deaths. Meta-analyses of RCT show that ICD therapy is associated with a relative risk reduction of SCD of approximately 60%, far less than the greater than 90% efficacy that many expect. The suboptimal performance of ICD therapy accounts for the failure of some RCT to achieve statistically significant effects on survival. The number of patients with ICD-unresponsive SCD is highly correlated with the number of cardiac deaths among control patients as well as ICD recipients. Otherwise, no definite patterns have emerged that clearly distinguish this mode of demise from other modes of cardiac death. Retrospective post-hoc analyses have not revealed distinguishing characteristics of patients with ICD-unresponsive SCD with respect to clinical variables, pre-terminal symptoms or to the setting of the terminal event. Despite advanced storage capabilities of implanted devices, almost no information has become available from RCT regarding the terminal rhythm or the response of the ICD. These observations have implications for clinical management and research. Candidates for ICD implantation based on RCT should be accurately informed about the residual risk of SCD. Investigators seeking to identify populations likely to benefit from ICD therapy based on SCD incidence should recognize that a significant fraction may not respond to ICD therapy. Reducing the incidence of ICD-unresponsive SCD would substantially improve survival and cost-effectiveness related to ICD therapy. Close cooperation between clinicians, investigators and representatives of industry and government is urgently needed to develop strategies to identify patients prone to ICD-unresponsive SCD, to determine its mechanisms and to develop methods of prevention and treatment.

Death, Sudden, Cardiac↗

PubMed1996

Carotid stent-supported angioplasty: a neurovascular intervention to prevent stroke.

Obstructive carotid artery disease is responsible for 60% of strokes in the United States and is the third major cause of death. Stent-supported carotid artery angioplasty has the potential to prevent stroke in thousands of patients and offers a number of potential advantages over surgical revascularization (carotid endarterectomy). Results of the prospective observational study at the University of Alabama at Birmingham indicate that carotid stent-supported angioplasty is safe and probably effective in reducing stroke in patients with high-risk cerebrovascular disease. Technical success was achieved in 99% of 146 procedures; 210 stents were placed in 152 vessels, with only 1 instance of stent thrombosis. The rate of major in-hospital complications was unexpectedly low-only 1 death and 2 major strokes. Seven patients suffered minor strokes, but only 2 were left with minor weakness. When compared with a projected complication rate of 6% had these patients undergone carotid endarterectomy, stenting resulted in fewer major events. At 6-month follow-up, 69 of 74 patients were evaluated by angiography or ultrasound, which detected 8 cases of stent deformation and a restenosis rate of < 5%. Because of these instances of stent deformation, use of the Palmaz (biliary) stent was discontinued. Although 1 patient had a transient ischemic attack, no strokes occurred during follow-up. To date, carotid stenting is an investigational procedure. Cardiovascular interventionalists, industry, and the FDA are encouraged to validate this approach through clinical testing. However, improvements in technique, devices, and adjunctive therapies are needed before the method can be tested in randomized trials.

Adult↗

PubMed1999

Evaluating computerized health information systems: hardware, software and human ware: experiences from the Northern Province, South Africa.

Despite enormous investment world-wide in computerized health information systems their overall benefits and costs have rarely been fully assessed. A major new initiative in South Africa provides the opportunity to evaluate the introduction of information technology from a global perspective and assess its impact on public health. The Northern Province is implementing a comprehensive integrated hospital information system (HIS) in all of its 42 hospitals. These include two mental health institutions, eight regional hospitals (two acting as a tertiary complex with teaching responsibilities) and 32 district hospitals. The overall goal of the HIS is to improve the efficiency and effectiveness of health (and welfare) services through the creation and use of information, for clinical, administrative and monitoring purposes. This multi-site implementation is being undertaken as a single project at a cost of R130 million (which represents 2.5 per cent of the health and welfare budget on an annual basis). The implementation process commenced on 1 September 1998 with the introduction of the system into Mankweng Hospital as the pilot site and is to be completed in the year 2001. An evaluation programme has been designed to maximize the likelihood of success of the implementation phase (formative evaluation) as well as providing an overall assessment of its benefits and costs (summative evaluation). The evaluation was designed as a form of health technology assessment; the system will have to prove its worth (in terms of cost-effectiveness) relative to other interventions. This is more extensive than the traditional form of technical assessment of hardware and software functionality, and moves into assessing the day-to-day utility of the system, the clinical and managerial environment in which it is situated (humanware), and ultimately its effects on the quality of patient care and public health. In keeping with new South African legislation the evaluation process sought to involve as many stakeholders as possible at the same time as creating a methodologically rigorous study that lived within realistic resource limits. The design chosen for the summative assessment was a randomized controlled trial (RCT) in which 24 district hospitals will receive the HIS either early or late. This is the first attempt to carry out an RCT evaluation of a multi-site implementation of an HIS in the world. Within this design the evaluation will utilize a range of qualitative and quantitative techniques over varying time scales, each addressing specific aims of the evaluation programme. In addition, it will attempt to provide an overview of the general impact on people and organizations of introducing high-technology solutions into a relatively unprepared environment. The study should help to stimulate an evaluation culture in the health and welfare services in the Northern Province as well as building the capacity to undertake such evaluations in the future.

Computers↗

PubMed2004

The recognition potential during sentence presentation: stimulus probability, background stimuli, and SOA.

Recognition potential (RP) is an electrical brain response that has proved its usefulness for studying semantic processing of isolated words, and appears when subjects view meaningful stimuli embedded in a stream of background images at a high rate of presentation: the rapid stream stimulation paradigm (RSS). The present technical study is aimed at testing the validity of this procedure in the study of words within sentences. For this purpose, we varied word and background probability of appearance, the number of background stimuli preceding each word, and stimulus onset asynchrony. Probability did not have significant effects on RP, but it was found that a minimum number of two background stimuli preceding each word and a high rate (250 ms) of presentation are preferable for enhancing RP amplitude. The RSS paradigm would therefore improve the visibility-and, hence, refine the analysis-of a component that can nevertheless be obtained with more standard paradigms, such as rapid serial visual presentation, devoid of interspersed background stimuli.

Adult↗

PubMed2005

Resident physicians' preparedness to provide cross-cultural care.

CONTEXT: Two recent reports from the Institute of Medicine cited cross-cultural training as a mechanism to address racial and ethnic disparities in health care, but little is known about residents' educational experience in this area. OBJECTIVE: To assess residents' attitudes about cross-cultural care, perceptions of their preparedness to deliver quality care to diverse patient populations, and educational experiences and educational climate regarding cross-cultural training. DESIGN, SETTING, AND PARTICIPANTS: A survey was mailed in the winter of 2003 to a stratified random sample of 3435 resident physicians in their final year of training in emergency medicine, family practice, internal medicine, obstetrics/gynecology, pediatrics, psychiatry, or general surgery at US academic health centers. RESULTS: Responses were obtained from 2047 (60%) of the sample. Virtually all (96%) of the residents indicated that it was moderately or very important to address cultural issues when providing care. The number of respondents who indicated that they believed they were not prepared to care for diverse cultures in a general sense was only 8%. However, a larger percentage of respondents believed they were not prepared to provide specific components of cross-cultural care, including caring for patients with health beliefs at odds with Western medicine (25%), new immigrants (25%), and patients whose religious beliefs affect treatment (20%). In addition, 24% indicated that they lacked the skills to identify relevant cultural customs that impact medical care. In contrast, only a small percentage of respondents (1%-2%) indicated that they were not prepared to treat clinical conditions or perform procedures common in their specialty. Approximately one third to half of the respondents reported receiving little or no instruction in specific areas of cross-cultural care beyond what was learned in medical school. Forty-one percent (family medicine) to 83% (surgery and obstetrics/gynecology) of respondents reported receiving little or no evaluation in cross-cultural care during their residencies. Barriers to delivering cross-cultural care included lack of time (58%) and lack of role models (31%). CONCLUSIONS: Resident physicians' self-reported preparedness to deliver cross-cultural care lags well behind preparedness in other clinical and technical areas. Although cross-cultural care was perceived to be important, there was little clinical time allotted during residency to address cultural issues, and there was little training, formal evaluation, or role modeling. These mixed educational messages indicate the need for significant improvement in cross-cultural education to help eliminate racial and ethnic disparities in health care.

Adult↗

PubMed1990

Mortality and fertility: how large is the direct child replacement effect in China?

"The direct child replacement effect, that is the extent to which parents will have a child to replace one that died, was estime d by Olsen's method in China, using microdata from a sample survey of 4785 ever-married women in Hebei province taken in 1985. Olsen's method corrects for bias in the ordinary least squares estimate and uses mortality rates as an instrumental variable. Data for all age groups were pooled. Estimates of the direct replacement effect before and after correction for bias were 0.836 and 0.556, showing that over half of child deaths were replaced. The instrumental variable estimate produced a result of 0.614, similar to 0.613, computed by considering p1 to be random. A computation without instrumental variables yielded 0.774. The results showed that this method for calculating the direct replacement effect works well with these data because several of the alternative methods gave close estimates. There appears to be little family specific variation in child mortality rates, pointing out the effectiveness of Chinese primary health care. The direct replacement effect of about 0.6 is, however about 3 times that found by Olsen in Colombia and Malaysia, and close to the theoretical maximum. The reason for such a high value may be the small family size in China, where death of a child is more likely to provoke a response. Or it might suggest that severe government policy causes couples to attempt to have another child. Policy implications in this setting are that rather than make more contraceptives available, or improve infant survival, Chinese policymakers should make a small family size attractive, e.g., by improving education or pensions.

Asia↗

PubMed2006

Iliac anastomotic stenting with a biodegradable poly-L-lactide stent: a preliminary study after 1 and 6 weeks.

PURPOSE: To assess the technical feasibility, thrombogenicity, and biocompatibility of a new biodegradable poly-L-lactic acid (PLLA) anastomotic stent. METHODS: A polytetrafluoroethylene bifurcated graft was implanted in 17 pigs through a midline abdominal incision. After transverse graft incision, 17 316L stainless steel stents and 17 PLLA stents were randomly implanted at both iliac anastomotic sites and deployed with a 6-mm balloon under direct vision without angiography. Intended follow-up was 1 week in 6 pigs receiving oral acetylsalicylic acid (ASA) and in 7 pigs receiving ASA/clopidogrel; 4 pigs receiving ASA/clopidogrel were followed for 6 weeks. At the end of the study, the segments containing the stents were surgically explanted and processed for histology to measure the mean luminal diameter, intimal thickness, and the vascular injury and inflammation scores. RESULTS: Initial technical success of stent placement was achieved in all animals without rupture of the suture. Two pigs died (unrelated to the stent) at 3 days after operation (1 in groups A and B). At 1 week, all PLLA stents showed thrombotic occlusion with the use of ASA alone. In contrast, all PLLA stents remained patent with concurrent administration of ASA/clopidogrel. All metal stents were patent regardless of the antiplatelet regimen. The mean luminal diameter of patent PLLA stents (4.13+/-0.17 mm) was comparable to metal stents (4.27+/-0.35 mm, p=0.78) at 1 week, but significantly diminished at 6 weeks (3.21+/-0.44 versus 4.19+/-0.18 mm, p=0.005). Histological analysis showed no signs of excessive recoil. PLLA stents induced a higher inflammation score (1.79+/-0.56) and more intimal hyperplasia (0.34+/-0.11 mm) compared to metal stents [1.27+/-0.44 mm (p<0.001) and 0.18+/-0.04 mm (p=0.006), respectively] at 6 weeks. Vascular injury was comparable between PLLA and metal stents. CONCLUSION: Biodegradable PLLA stents showed higher thrombogenicity and reduced patency compared to metal stents during early follow-up. Although ASA and clopidogrel prevented thrombotic occlusion, the increased inflammatory response and neointima formation remain major concerns of PLLA stents. A solution to this problem might be the incorporation of anti-inflammatory drugs into the PLLA stent.

Absorbable Implants↗

PubMed1996

Combined immunosuppressive therapy with tacrolimus and mycophenolate mofetil for small bowel transplantation in pigs.

In a swine model of orthotopic small bowel transplantation, we assessed the efficacy of combined therapy with a low dose of tacrolimus plus mycophenolate mofetil, compared with high-dose tacrolimus monotherapy. The bowel was replaced in 25 piglets: group 1 (n = 5), no immunosuppression; group 2 (n = 10), tacrolimus, 0.3 mg/kg daily i.m. for 7 days, followed by b.i.d. oral doses to maintain blood levels of 15-25 ng/ml; and group 3 (n = 10), tacrolimus, 0.1 mg/kg i.m., in a single dose on day 0 and thereafter oral doses to maintain blood levels of 5-15 ng/ml, plus oral mycophenolate mofetil (10 mg/kg twice daily). Follow-up time was limited to 60 days. Median survival time as 11, 27, and > 60 days in groups 1, 2, and 3, respectively (P = 0.001). Survival rates were 0%, 40%, and 80% at 30 days and 0%, 0%, and 70% at 60 days in groups 1, 2, and 3, respectively (P = 0.03), group 1 vs. group 2; P = 0.003, group 1 vs. group 3; P = 0.02, group 2 vs. group 3). One animal in group 1 (20%) and two animals each in groups 2 and 3 (20%) died of technical complications. Rejection was the cause of death of 80% of animals of group 1 and of no animals in either group 2 or 3. None of the immunosuppressed animals developed clinical or histopathological evidence of graft-versus-host disease. Sixty percent of animals in group 2 (n = 6) and 10% in group 3 (n = 1) died from infections; two other animals in group 2 died of emaciation. The seven animals of group 3 that were alive at 60 days had immunosuppression stopped at that time. All died of rejection within 1 month. In conclusion, double-drug therapy with tacrolimus and mycophenolate mofetil consistently allowed extended survival after small bowel transplantation in swine, preventing or controlling acute cellular rejection without a high incidence of lethal complications related to overimmunosuppression.

Animals↗