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Biomedical subjects

P Wyss

Publications and source records attributed to P Wyss.

At least 19 recordsLinked to original sources
PubMed2006

Interrelation of peri-operative morbidity and ASA class assignment in patients undergoing gynaecological surgery.

OBJECTIVE: The aim of this study was to estimate intra- and post-operative risk using the American Society of Anaesthesiologists (ASA) classification which is an important predictor of an intervention and of the entire operating programme. STUDY DESIGN: In this retrospective study, 4435 consecutive patients undergoing elective and emergency surgery at the Gynaecological Clinic of the University Hospital of Zurich were included. The ASA classification for pre-operative risk assessment was determined by an anaesthesiologist after a thorough physical examination. We observed several pre-, intra- and post-operative parameters, such as age, body-mass-index, duration of anaesthesia, duration of surgery, blood loss, duration of post-operative stay, complicated post-operative course, morbidity and mortality. The investigation of different risk factors was achieved by a multiple linear regression model for log-transformed duration of hospitalisation. RESULTS: Age and obesity were responsible for a higher ASA classification. ASA grade correlates with the duration of anaesthesia and the duration of the surgery itself. There was a significant difference in blood loss between ASA grades I (113+/-195 ml) and III (222+/-470 ml) and between classes II (176+/-432 ml) and III. The duration of post-operative hospitalisation could also be correlated with ASA class. ASA class I=1.7+/-3.0 days, ASA class II=3.6+/-4.3 days, ASA class III=6.8+/-8.2 days, and ASA class IV=6.2+/-3.9 days. The mean post-operative in-hospital stay was 2.5+/-4.0 days without complications, and 8.7+/-6.7 days with post-operative complications. Multiple linear regression model showed that not only the ASA classification contained an important information for the duration of hospitalisation. Parameters such as age, class of diagnosis, post-operative complications, etc. also have an influence on the duration of hospitalisation. CONCLUSION: This study shows that the ASA classification can be used as a good and early available predictor for the planning of an intervention in gynaecological surgery. The ASA classification helps the surgeon to assess the peri-operative risk profile of which important information can be derived for the planning of the operation programme.

Adult↗
PubMed2006

Time-lapsed investigation of three-dimensional failure and damage accumulation in trabecular bone using synchrotron light.

Synchrotron radiation micro-computed tomography (SRmicroCT) is a very useful technique when it comes to three-dimensional (3D) imaging of complex internal and external geometries. Being a fully non-destructive technique, SRmicroCT can be combined with other experiments in situ for functional imaging. We are especially interested in the combination of SRmicroCT with mechanical testing in order to gain new insights in the failure mechanism of trabecular bone. This interest is motivated by the immense costs in health care due to patients suffering from osteoporosis, a systemic skeletal disease resulting in decreased bone stability and increased fracture risk. To better investigate the different failure mechanisms on the microlevel, we have developed a novel in situ mechanical compression device, capable of exerting both static and dynamic displacements on experimental samples. The device was calibrated for mechanical testing using solid aluminum and bovine trabecular bone samples. To study different failure mechanisms in trabecular bone, we compared a fatigued and a non-fatigued bovine bone sample with respect to failure initiation and propagation. The fatigued sample failed in a burst-like fashion in contrast to the non-fatigued sample, which exhibited a distinct localized failure band. Moreover, microscopic cracks - microcracks and microfractures - were uncovered in a 3D fashion illustrating the failure process in great detail. The majority of these cracks were connected to a bone surface. The data also showed that the classification of microcracks and -fractures from 2D section can sometimes be ambiguous, which is also true for the distinction of diffuse and distinct microdamage. Detailed investigation of the failure mechanism in these samples illustrated that trabecular bone often fails in delamination, providing a mechanism for energy dissipation while conserving trabecular bone architecture. In the future, this will allow an even better understanding of bone mechanics related to its hierarchical structural organization.

Animals↗
PubMed2004

Comparison of microfocus- and synchrotron X-ray tomography for the analysis of osteointegration around Ti6Al4V implants.

Micro-computed tomography (microCT) provides quantitative three-dimensional information of bone around titanium implants similar to classical histology. The study, based on an animal model, containing cuboid-shaped biofunctionalised Ti6Al4V implants with surrounding bone after 4 weeks, is performed using 3 microCT-systems with X-ray tubes, one synchrotron-radiation-based microCT-system (SRmicroCT), and classical histology. Although the spatial resolution of the microCT-systems is comparable, only the results of SRmicroCT agree with results of classical histology. The X-ray tube sources give rise to huge artefacts in the tomograms (interface scattering, beam hardening), which impaired the quantitative analysis of bone up to about 200microm from the implant surface. Due to the non-destructive character of microCT the specimens can be subsequently examined by classical histology without restriction. The quantitative comparison of bone formation uncovers the strong dependence of the newly formed bone from the selected slice. This implies the necessity of 3D analysis. SRmicroCT and classical histology prove that surface modifications of the titanium implant significantly influence the bone formation. Using SRmicroCT, the preparation artefacts due to cutting and polishing are excluded.

Animals↗
PubMed2002

Impact of the reduction of anaesthesia turnover time on operating room efficiency.

BACKGROUND AND OBJECTIVE: We investigated whether an increase in anaesthesia staffing to permit induction of anaesthesia before the previous case had ended ('overlapping') would increase overall efficiency in the operating room. Hitherto, the average duration of operating sessions was too long, thus impeding the timely commencement of physicians' ward duties. METHODS: The investigation was designed as a prospective, non-randomized, interrupted time-series analysis divided into three phases: (a) a baseline of 3.5 months, (b) a 2.5 month intervention phase, in which anaesthesia staffing was increased by one attending physician and one nurse, and (c) a further 2 months under baseline conditions. Data focussed on process management were collected from operating room staff, anaesthesia personnel and surgeons using a structured questionnaire collected daily during the entire study. RESULTS: Turnover time between consecutive operations decreased from 65 to 52 min per operation (95% CI: 9; 17; P = 0.0001). Operating room occupancy increased from 4:28 to 5:27 h day-1 (95% CI: 50; 68; P = 0.005). The surgeons began their work on the ward 35 min (95% CI: 30; 40) later than before the intervention and their overtime increased from 22:36 to 139:50 h. CONCLUSIONS: The time between surgical operations decreased significantly. Increased operating room efficiency owing to overlapping induction of anaesthesia allows more intense scheduling of operations. Thus, physicians and nurses can be released to spend more time with their patients in the ward. Improving the efficiency of the operating room alone is insufficient to improve human resource management at all levels of a surgical clinic.

Anesthesiology↗
PubMed2001

Photodynamic therapy of locoregional breast cancer recurrences using a chlorin-type photosensitizer.

Chest wall recurrences are a frequent problem in patients treated by mastectomy for breast cancer. Surgery and ionizing radiation are established treatment modalities in these cases. Photodynamic therapy (PDT) provides an alternative treatment modality using a photosensitizer and laser light to induce selective tumor necrosis. PDT was performed as compassionate use in 7 patients aged 57.6 years (+/-12.6 SD). A total of 89 metastatic skin nodes were treated in 11 PDT sessions. As photosensitizer meta-tetra(hydroxyphenyl)chlorin (m-THPC) was applied intravenously. Patients (n = 3) photosensitized with a drug dose of 0.10 mg/kg bodyweight were irradiated 48 hr after drug application at a lightdose of 5 J/cm(2). Patients (n = 4) were illuminated by an optical dose of 10 J/cm(2) 96 hr after photosensitization with 0.15 mg/kg. Laser light at a wavelength of 652 nm was generated by a diode laser and applied by a front lens light diffuser using a fluence rate of 20--25 mW/cm(2). PDT using m-THPC resulted in complete response in all patients. Response to treatment did not differ when using the 2 different drugdose protocols. Healing time depended mainly on the size of the illumination field but not on the lightdose. Pain score usually raised 1 day after PDT and lasted at higher levels for about 10 days. Healing time usually ranged between 8--10 weeks. Photodynamic technique offers a minimal-invasive, outpatient treatment modality for recurrent breast cancer on the chest wall with few side effects, high patient's satisfaction and with possible repetitive application.

Antineoplastic Agents↗
PubMed2001

Skin protection for photosensitized patients.

BACKGROUND AND OBJECTIVE: The goal of this study was to evaluate various creams for their capability to protect photosensitized skin from visible light. STUDY DESIGN/MATERIALS AND METHODS: Two cover creams and creams containing various combinations of Vaseline with TiO(2), ZnO, and Fe(2)O(3) were used to measure the reduced light transmission and the light absorption spectrum. In vitro and in vivo tests were performed to assess the protection from light by above mentioned compounds. RESULTS: The cover creams and the 50% TiO(2) cream showed similar efficacy in reducing light transmission, while the sunscreen was less efficient by a factor of 5. Cell protection by 25% TiO(2)+25% ZnO, TiO(2), or the cover creams was more efficient than protection by the sunscreen or other compounds. In vivo, the dark cover cream protected the skin by a factor of 3.4 better than the sunscreen. CONCLUSION: The dark cover cream has acceptable properties to protect photosensitized skin.

Absorption↗
PubMed2001

Photodynamic therapy of vulvar intraepithelial neoplasia III using topically applied 5-aminolevulinic acid.

OBJECTIVES: The aim of this study was twofold: first, to determine the feasibility of photodynamic therapy (PDT) of vulvar intraepithelial neoplasia III (VIN III) using topically applied 5-aminolevulinic acid (ALA) for photosensitization, and second, to compare PDT results with those of laser evaporation and local excision. METHODS: Fifteen patients with VIN III had 10 g of 10% ALA gel applied to the entire vulva. Two to three hours after drug application the vulva was irradiated with 120 J/cm(2) laser light at a wavelength of 635 nm. The procedure was performed without anesthesia in most patients. Thirty patients with VIN III treated by laser evaporation and 27 patients treated by surgical excision served as controls. RESULTS: Eight weeks following PDT, 11 of 15 patients were free of VIN III as determined by biopsy. Excellent tissue preservation was achieved and no ulcers or scarring occurred. Three recurrences were seen during follow-up, at 5, 6, and 7 months after PDT. Twelve months after treatment, analysis of disease-free survival revealed no statistically significant difference between patients treated with PDT and patients treated with conventional treatment modalities (P = 0.67) but the power of this analysis is low. In multivariate analysis, multifocal disease was the sole variable associated with a reduced disease-free survival. CONCLUSION: While PDT of VIN III seems to show efficacy similar to that of conventional treatment modalities it offers unique advantages: healing time is short, preservation of normal vulvar appearance is excellent, and PDT may be performed without anesthesia. Hence, PDT of VIN III deserves further investigation.

Administration, Topical↗
PubMed2001

Necrosis of the tongue and unilateral blindness in temporal arteritis.

While blindness is one of the typical clinical presentations of temporal arteritis, tongue necrosis, on the other hand, is an unusual complication of the disease. An 80 year old male patient presenting a sudden massive swelling of the tongue was admitted to the Hospital of Yverdon. The swelling rapidly progressed to a complete necrosis of the tongue within a few days. The clinical presentation, the dramatic evolution of the necrosis, and sudden unilateral blindness despite prompt treatment confirmed our diagnosis of temporal arteritis. However, all the examinations, including biopsy of the right temporal artery, remained non-specific for the disease. Our diagnosis was based on the unusual clinical presentation of the disease.

Aged↗
PubMed2000

PEG-m-THPC-mediated photodynamic effects on normal rat tissues.

Photodynamic therapy (PDT) of malignancies uses light to activate a photosensitizer preferentially accumulated in cancer cells. The first pegylated photosensitizer, tetrakis-(m-methoxypolyethylene glycol) derivative of 7,8-dihydro-5,10,15,20-tetrakis(3-hydroxyphenyl)-21-23-[H]-porphyrin (PEG-m-THPC), was evaluated in non-tumor-bearing rats. The aim of this study was to assess the photodynamic threshold for damage and its sequelae in normal rat tissue. Thirty-five Fischer rats were sensitized with 3, 9 or 30 mg/kg body weight PEG-m-THPC. Colon, vagina and perineum were irradiated with laser light of 652 nm wavelength and an optical dose of 50, 150 or 450 J/cm fiber length. Temperature in the pelvis was measured during PDT. Three days following PDT the effect on skin, vagina, colon, striated muscle, connective tissue, nerves and blood vessels was assessed by histology. The healing of the above-mentioned tissues was assessed on two rats 3 and 8 weeks after PDT using 9 mg/kg PEG-m-THPC activated with 450 J/cm laser light. No dark toxicity was observed. PDT using 30 mg/kg PEG-m-THPC induced severe necrosis irrespective of the optical dose. Body weight of 9 or 3 mg/kg activated with less than 450 J/cm induced moderate or no damage. No substantial increase in body temperature was seen during PDT. Tissues with severe PDT-induced damage seem to have a good tendency to regenerate. We conclude that within the dose required for tumor treatment PEG-m-THPC is a safe photosensitizer with promising properties. PDT of the colon mucosa below 9 mg/kg PEG-m-THPC and 150 J/cm seems to be safe. All other tissues can be exposed to 9 mg/kg PEG-m-THPC activated with less than 450 J/cm laser light with little side effects.

Animals↗
PubMed2000

Appropriateness and necessity research on the Internet: using a "second opinion system".

Appropriateness and necessity research of various procedures in medicine may be the most complex field of innovation in healthcare and technology assessment. Nevertheless, the appropriateness of the indication of any medical intervention is probably more important than the outcome since even ideal quality components of structures, processes and outcomes become irrelevant without a proper indication. The first part of our appropriateness initiative in interventional cardiology and gynecology was to formulate guidelines. To define the appropriateness for coronary angiography, coronary revascularization and hysterectomy, literature-based consensus methods were used. The second part was to disseminate the guidelines in a user-friendly manner via the Internet. Therefore, we relied on a system-driven query facility for propositional (experts) rules. The next part of the appropriateness initiative may be a user-friendly Internet-based data collection system to validate the national accepted guidelines. Most important may be that only data that is needed can be collected using a refined database technology. The described Second Opinion System can be found under: http:sos.inf.ethz.ch. Research on indications with data on clinical outcome may open new opportunities to validate indication guidelines using Internet/database technology for data analysis and browsing of decision graphs concerning clinical decision-making. This new technology facilitates the evaluation of appropriateness and necessity criteria in combination with clinical outcomes.

Aged↗
PubMed1999

[Possible future of the project for quality assurance of indications and outcome in interventional cardiology and gynecology].

In the last few years the basis for national guidelines for the indications of coronary angiography, coronary revascularisation and hysterectomy has been established. The guidelines have been published and are accessible to medical doctors and patients on the Internet using a database system called "Second Opinion System": http:/(/)sos.inf.ethz.ch Dissemination, implementation and validation of the guidelines will be of major importance in the near future. With reference to validation, the question remains whether the established guidelines are correct for the everyday treatment of patients. A suitable method of answering this important question is comparison between the appropriateness and necessity rates of the various indication groups, combined with outcome measurements. The Internet-based second opinion system (SOS) may be used for data collection in order to verify hypotheses. Because of the database architecture, only relevant information about the patients is collected via Internet, independent of time and place. In addition, the system allows users to evaluate their individual data, and special attention is given to data protection. The discussion about priorities in health care (rationing) will be increasingly important in the near future. The present project may offer a way of maintaining adequate access to health care services for patients. Therefore, the participation of as many institutions as possible in the project "quality assurance of indication and outcome in interventional cardiology and in gynaecology" is of great importance.

Cardiology↗
PubMed1999

Swiss consensus guidelines for hysterectomy. Swiss Society of Gynecology and Obstetrics, Switzerland.

OBJECTIVE: The quality of the indication for hysterectomy is widely discussed at present. In early 1996, the committee for quality assurance of the Swiss Society of Gynecology and Obstetrics decided to set up nationally accepted guidelines for the indication of hysterectomy. METHODS: A modified Delphi approach was used. In a first step, general guidelines and actions prior to hysterectomy were defined. An expert panel of 17 Swiss gynecologists rated 74 frequent indications, twice for appropriateness (more benefits than risks for the patient), once for necessity (n = 34; procedure has to be offered or discussed with the patient), and outlined suggestions to be performed prior to hysterectomy. RESULTS: In a home rating round before the first panel met, there was an agreement rate of 48%. In 45% we observed neither agreement nor disagreement; in 7% we found disagreement. After the panel discussion 89% of experts agreed, 11% were indeterminate, and there was no disagreement. The necessity ratings showed agreement in 68% while 32% were indeterminate. The average median rating on a 1-9 point scale (1 = extremely inappropriate, 9 = extremely appropriate or necessary) was 5.4 over all single indications for appropriateness and 7.8 in single indications for necessity. After a second panel for consensus all panelists agreed on both appropriateness and necessity. CONCLUSION: The results of the appropriateness and necessity consensus presented in this paper reflect the findings of a 17 member Swiss panel. This joint effort by a medical society may be a step towards the direction of a peer controlled healthcare system.

Congresses as Topic↗
PubMed1998

Food intake in free-feeding and energy-deprived lean rats is mediated by the neuropeptide Y5 receptor.

The new neuropeptide Y (NPY) Y5 receptor antagonist CGP 71683A displayed high affinity for the cloned rat NPY Y5 subtype, but > 1, 000-fold lower affinity for the cloned rat NPY Y1, Y2, and Y4 subtypes. In LMTK cells transfected with the human NPY Y5 receptor, CGP 71683A was without intrinsic activity and antagonized NPY-induced Ca2+ transients. CGP 71683A was given intraperitoneally (dose range 1-100 mg/kg) to a series of animal models of high hypothalamic NPY levels. In lean satiated rats CGP 71683A significantly antagonized the increase in food intake induced by intracerebroventricular injection of NPY. In 24-h fasted and streptozotocin diabetic rats CGP 71683A dose-dependently inhibited food intake. During the dark phase, CGP 71683A dose-dependently inhibited food intake in free-feeding lean rats without affecting the normal pattern of food intake or inducing taste aversion. In free-feeding lean rats, intraperitoneal administration of CGP 71683A for 28 d inhibited food intake dose-dependently with a maximum reduction observed on days 3 and 4. Despite the return of food intake to control levels, body weight and the peripheral fat mass remained significantly reduced. The data demonstrate that the NPY Y5 receptor subtype plays a role in NPY-induced food intake, but also suggest that, with chronic blockade, counterregulatory mechanisms are induced to restore appetite.

Animals↗
PubMed1998

The pharmacology of neuropeptide Y (NPY) receptor-mediated feeding in rats characterizes better Y5 than Y1, but not Y2 or Y4 subtypes.

Thirteen neuropeptide Y (NPY) agonists were administered intracerebroventricularly (i.c.v.) in rats (full dose-response curves) to estimate their half-effective dose (ED50) on feeding. These values were compared to their binding affinities (IC50) for rat NPY receptor subtypes Y1, Y2, Y4 and Y5 in vitro. Correlations between in vivo ED50 and in vitro IC50 were strong for the Y5 (r = 0.87; P < 0.01), weak for the Y1 (r = 0.48; P < 0.04) and non-significant for the Y2 and Y4 receptor subtypes. In vitro, h[D-Trp32]NPY was found to be a Y5-selective ligand and a full agonist in Y5-expressing cells. In vivo, it dose-dependently stimulated feeding, but failed to induce the full maximal response observed with pNPY. It did not antagonize pNPY-induced feeding and overfeeding in 24 h fasted rats. These findings demonstrate a role for the Y5, or possibly Y5 in combination with Y1, but not Y2 or Y4 receptor subtypes in feeding. No evidence was found for the existence of an additional, as yet undescribed, NPY feeding receptor.

Animals↗
PubMed1998

Stimulation of feeding in lean but not in obese Zucker rats by a selective neuropeptide Y Y5 receptor agonist.

Obese Zucker rats are characterized by a reduced hypothalamic NPY receptor density. We tested the effects of intracerebroventricular injections of human NPY (hNPY) and [D-Trp32]NPY, a weak but selective NPY Y5 receptor agonist, on food intake in lean and obese Zucker rats. The effect of a maximal dose of hNPY (10 microg) on feeding was more pronounced in lean than in obese rats. [D-Trp32]NPY (10 microg) stimulated feeding in lean but not in obese Zucker rats. It did not affect the feeding response to hNPY, excluding the activation of an inhibitory receptor. These results are in favor of a down-regulation of the NPY 'feeding' receptor in the obese rat, which is suggested to be the Y5 subtype.

Animals↗
PubMed1998

Quality assessment in gynecology and obstetrics. Projects and experience in Switzerland.

The first steps in quality assessment of results of performance in gynecology and obstetrics were taken by the Swiss Association of the OB/GYN Clinics of the Swiss Society of Obstetrics and Gynecology in the 1980's. Currently, medical data of more than 800,000 patients are available, allowing a good comparison of the quality of results. Concerned that purchasing coverage for health services was made exclusively on the basis of cost, resulting in lower public health quality, the Swiss Society of OB/GYN set up a Board of Quality Assessment in 1995. Not only the quality of results, but also the quality of indications, structures and processes are considered by using a modified Donabedian model. Moreover, standardized patient information forms have been worked out for 15 gynecological and five obstetrical operations. Since hysterectomy is the most common major gynecological operation in Switzerland, the evaluation of the quality of the indications is of substantial interest. Guided by the RAND Appropriateness Method, criteria for quality assessment with respect to appropriateness and necessity of hysterectomy have been drawn up. Swiss guidelines and 125 different clinical scenarios are defined by a panel of 22 OB/GYN experts. The aim of this project is to offer an interactive second opinion system, called "Swiss Guidelines for Hysterectomy", and anonymous self-assessment of quality. Appropriateness and necessity of medical procedures have to be defined by medical professionals providing a proper balance between the patient's desires and financial demands.

Female↗
PubMed1997

Premenopausal node-negative breast cancer: may adjuvant chemotherapy be indicated by the analysis of nuclear DNA dynamics?

The management of premenopausal node-negative breast cancer patients is discussed controversially. Accurate cellular as well as biochemical markers are essential for this cancer group to identify high risk patients needing adjuvant chemotherapy. In the present study, flow cytometric DNA analysis (DNA-ploidy status, DNA-index, S-phase fraction, S+(G2+M)-phase fraction) and clinico-pathological variables (clinical stage, tumor size, receptor status, age, histological type and grade) as prognostic factors were determined on paraffin-embedded tumors to predict overall survival (OS) and disease-free survival (DFS). Median observation time was 6.1 years (n = 57). S+(G2+M)-phase fraction was the only flow cytometric DNA predictor of overall survival in the univariate analysis (log-rank test): As compared to the patients with lower S+(G2+M)-phase fraction (< or = 9.3%), patients with S+(G2+M)-phase fraction greater than 9.3% had shorter survival (P = 0.039). Of all the clinico-pathological parameters analyzed (univariate analysis), the survival time was found to be longer when estrogen- and/or progesterone-receptor status was positive (overall survival: P = 0.039; disease-free survival: P = 0.017) and the histological grade was low (overall survival: I + II vs III: P = 0.024; I vs II vs III: P = 0.046). In the multivariate analysis, receptor status was the strongest predictor for overall and disease-free survival. These results suggest that S+(G2+M)-phase fraction in premenopausal node-negative breast cancer could be an additional valuable prognostic factor to classify high risk breast cancer patients needing adjuvant chemotherapy.

Adult↗