Sample Size Matters: A Guide for Surgeons

Considerations of sample size computations in the medical literature have gained increasing importance over the past decade and are now often mandatory for scientific grant proposals, protocols, and publications. However, many surgeons are ill-prepared to understand the parameters on which the appropriate sample size is based. The present article has several objectives: first, to review the need for sample size considerations; second, to explain the ingredients necessary for sample size computations in simple, nonmathematic language; third, to provide options for reducing the sample size if it seems impracticably large; and fourth, to help avoid some of the more common mistakes encountered when computing sample size

Lymphadenektomie der Axilla

Zusammenfassung: Die axilläre Lymphknotendissektion dient der lokalen Tumorkontrolle und dem Staging. Bei Mammakarzinom, malignem Melanom und vielen anderen soliden Tumoren stellt der nodale Status der wichtigste prädiktive und prognostische Faktor dar. Wegen der Morbidität dieses Eingriffes erfolgt die Lymphadenektomie im axillären Bereich heute selektiv, d.h. geleitet durch die histologische Aufarbeitung des Wachtpostenlymphknotens (Sentinel-node-Biopsie). Die chirurgische Technik der Axilladissektion wird dargestellt, Komplikationen und die onkologischen Ergebnisse für das Mammakarzinom und das maligne Melanom zusammengefass

The pond biodiversity index "IBEM", a new tool for the rapid assessment of biodiversity in ponds from Switzerland. Part 2. Method description and examples of application

Ponds are now widely recognized to contribute significantly to regional freshwater biodiversity. Therefore, tools to easily and rapidly assess biological quality specificalIy for these aquatic habitats have been increasingly requested by conservation planners and nature managers. In c10se association with practitioners, we developed such a method for Switzerland; the pond biodiversity index "IBEM". The IBEM-Index is based on the assessment of the taxonomic richness of 5 groups: aquatic vege­tation, Gastropoda, Coleoptera, adult Odonata and Amphibia. No abundance data are necessary and genus level identification is required for alI groups except Amphibia (species level). The sampling methodology is a stratified random strategy and alIows the use of richness estimators to transform the observed taxonomic richness (Sobs) into true taxonomic richness (Strue). As the IBEM assessment folIows the methodology presented in the Water Framework Directive, it is based on the caIculation of the ratio of true taxonomic richness (Strue) to reference-based predicted richness (Sref)' Each of the five taxonomic groups is assessed separately and the overalI biological quality of any given pond (i.e. the IBEM-Index) is the average of the five ratios. This score is later converted into one of five quality c1asses for each pond: bad (O to 0.2), poor (> 0.2 to 0.4), moderate (> 0.4 to 0.6), good (> 0.6 to 0.8), and high (> 0.8 to 1). In this paper, the implementation of the IBEM-Index is described in detail. The sampling methodologies are developed (for the biodiversity and the environmental variables) as welI as the assessment methodology. FinalIy, two examples are presen­ted in detail, for a "good" quality pond and for a "bad" quality pond. The method implementation also includes a website (http://campus.hesge.ch/ibem) which a1lows the online caIculation of the index, and provides support for both sampling and assessment methodologies to users. The IBEM-Index is a rapid assessment method which gives an overalI value of pond biodiversity in terms of taxa richness and can be used, for example, in regional screenings or site monitoring in Switzerland. Moreover, as biodiversity is generalIy recognized as a good indicator of global ecological quality, the IBEM-Index can also be used to investigate ecosystem quality.Está ampliamente reconocido que las pequeñas masas de agua (charcas) contribuyen de forma significativa a la biodiversi­dad regional de las aguas dulces. Por tanto, las herramientas que de manera rápida y fácil evalúen especíjicamente la calidad biológica de estos hábitats acuáticos están siendo requeridas cada vez más por profesionales de la gestión y conservación del medio natural. En estrecha colaboración con estos profesionales, se ha desarrollado un método de este tipo para Suiza; el índice de biodiversidad de charcas "IBEM". El Índice-IBEM se basa en la evaluación de la riqueza taxonómica de 5 grupos: vegetación acuática, gasterópoda, coleópteros, odonatos (adultos) y anfibios. No son necesarios datos de abundancia y se requiere un nivel identificación de género para todos los grupos excepto para los anfibios (nivel de especie). Se usa un muestreo aleatorio estratificado que permite obtener estimadores para transformar la riqueza taxonómica observada (Sobs) en riqueza taxonómica real (Strue)' La evaluación IBEM sigue la metodología de la Directiva Marco del Agua, que se basa en el cálculo de la relación entre la riqueza taxonómica real (Strue) y la riqueza esperable en un estado de referencia (Sre!)' Cada uno de los cinco grupos taxonómicos se evalúa por separado y la calidad biológica de una charca determinada (Índice-IBEM) es la media de los cinco coeficientes. Este resultado es posterionnente asignado a una de las cinco clases de calidad: malo (O a 0.2), deficiente (> 0.2 a 0.4), moderado (> 0.4 a 0.6), bueno (> 0.6 to 0.8), y muy bueno (> 0.8 al). En este artículo, se describe detalladamente la aplicación del índice IBEM y se desarrollan las metodologías de mues­treo (para la biodiversidad y las variables ambientales) y de valoración utilizadas. Por último, se presentan con detalle dos ejemplos, una charca con "buena" calidad y otra con "mala" calidad. Se incluye también una página web (http://campus.hesge.ch/ibem), que permite el cálculo del índice a través de intemet y sirve de apoyo a los usuarios en las metodologías de muestreo y de valoración. El índice IBEM es un método de evaluación rápida que da un valor general de la diversidad biológica de una charca en términos de riqueza de taxones y se puede utilizar, por ejemplo, a nivel regional o en el seguimiento de una localidad, en Suiza. Además, como la biodiversidad es un buen indicador de la calidad ecológica global, el índice IBEM también se puede usar para evaluar el estado del ecosistema

Factors predicting in-breast tumor recurrence after breast-conserving surgery

Purpose: The main objectives of this study were to identify risk factors for local in-breast tumor recurrence after breast-conservation and to evaluate the impact of IBTR (in-breast tumor recurrence) on overall survival. Methods: A total of 335 consecutive patients with 346 invasive and insitu breast cancers were treated with breast conserving therapy. Univariate and multivariate statistical analysis were performed and survival rates were calculated and analyzed using the Kaplan-Meier method. Results: With a median follow-up period of 70.6months 14 patients (4%) developed an IBTR. Overall survival and the disease-free 8-year actuarial survival of patients were 95% and 93%, respectively. The overall survival of patients with tumour recurrence on any site was significantly shorter than of those without recurrence (64% versus 85% after 8years of follow-up; P<0.0001). Similarly, overall survival was significantly reduced in patients with distant metastases compared to all others without distant disease (88% versus 40% after 8years; P<0.0001). In contrast, overall survival of patients who experienced IBTR did not differ significantly from the group of patients who never developed IBTR (87% versus 70% after 8years of follow-up). By univariate analysis, lobular carcinoma, high grade tumours, multifocality, concomitant LCIS and DCIS, the absence of estrogene and progesterone receptor status, as well as R1-status, were significant predictors of IBTR. By multivariate analysis, only R1-status (P<0.002) and the presence of LCIS around the invasive tumour (P<0.03) remained as significant factors predicting IBTR. Conclusions: Concomitant lobular carcinomas insitu, as well as R1 surgical status are independent significant risk factors for in breast tumor recurrence after breast conserving therap

The pond biodiversity index "IBEM", a new tool for the rapid assessment of biodiversity in ponds from SwitzerlandPart 1. Index development

Due to legal requirements, nature managers increasingly have to carry out assessments of biodiversity for conservation purpo­seso For ponds, a type of waterbody now widely recognized as an important reservoir for freshwater biodiversity, standardized bioassessment methods are needed, but still rare. We produced such a tool for smalllowland waterbodies in Switzerland: the Pond Biodiversity Index ("IBEM"). This Index is the adaptation of a method used by researchers for assessing the biodiver­sity in ponds, PLOCH, which does not currently meet the requirements for routine use by nature managers because it is too expensive and requires a high skill level in taxonomic identification. A method intended for practitioners has to be simple, standardized, cheap, adjustable, and consistent with the legislative framework. In order to fulfill these requirements, the theoretical and practical aspects of IBEM were developed with a group of representative end users including nature conservation managers, consuitants, govemmental organizations and taxonomic experts. To develop the method, we used a species dataset from 63 Swiss lowland ponds which included five taxonomic groups: aquatic plants, aquatic Gastropoda, aquatic Coleopte­ra, adult Odonata and Amphibia. The following topics were addressed: (i) the number and type of taxonomic groups which should be used for producing the index (is it possible to use surrogates?) (ii) the level of identification for each taxonomic group (species? genus? family?) (iii) the sampling strategy (sampling technique, number of replicates), (iv) the calculation of a unique index and the strategy for assessing its score, and (v) the transfer of this new method to end users. The new method IBEM uses all five taxonomic groups, because a subset of groups did not produce reliable assessments of pond biodiversity. Identification to genus level is required for four groups (aquatic plants, aquatic Gastropoda, aquatic Coleoptera, aduit Odona­ta) and species level for Amphibia. The sampling methodology is based on the stratified random strategy used in the PLOCH method, but with a slight modification in the number of samples per pond. The assessment follows the methodology adopted by the European Water Framework Directive, and the ratio of the observed richness to a reference-based predicted richness is translated into one of five quality categories for each pond. The final index is the mean of the five assessment scores. To facilitate the implementation of the IBEM method, a website (http://campus.hesge.ch/ibem) enables online calculation of the index, and provides instructions on both sampling and assessment methodologies. Furthermore, training courses are organized by the authors of the method for end users.Debido a requerimientos legales, es cada vez más necesario que los gestores del medio ambiente lleven a cabo evaluaciones de la biodiversidad dirigidas a la conservación de la naturaleza. Para las charcas, pequeñas masas de agua ampliamente reconocidas como importantes reservorios de diversidad biológica acuática, los métodos normalizados de bio-evaluación son necesarios, pero aún escasos. Para esta tipología de pequeñas masas de agua situadas a baja altitud en Suiza se ha elaborado el índice de Biodiversidad de charcas ("IBEM"). Este índice es la adaptación de un método utilizado por los investigadores para evaluar la diversidad biológica en charcas, PLOCH, que no cumplía los requisitos para un uso rutinario por parte de los gestores del medio natural por ser demasiado caro y requerir un alto nivel de experiencia en la identificación taxonómica. Un método destinado a estos profesionales tiene que ser sencillo, estandarizado, económico, ajustable y en consonancia con el marco legislativo. Con el fin de cumplir estos requisitos, los aspectos teóricos y prácticos de IBEM se han desarrollado con un grupo representativo de posibles usuarios, incluyendo gestores conservadores, consultores, organizaciones guber­namentales y expertos en taxonomía. Para desarrollar el método, se ha utilizado una base de datos de 63 charcas Suizas, situadas en altitudes bajas, que incluye cinco grupos taxonómicos: plantas acuáticas, gasterópodos acuáticos, coleópteros acuáticos, odonatos adultos y anfibios. Se han estudiado los siguientes aspectos: (i) el número y tipo de grupos taxonómicos que se deben utilizar (es posible el uso de sustitutos?) (ii) nivel de identificación para cada grupo taxonómico (¿especie, género, familia?) (iii) estrategia de muestreo (técnica, número de réplicas), (iv) cálculo de un índice único y procedimiento para la asignación de valores y (v) la transferencia de este método a los posibles usuarios. El nuevo método IBEM utiliza los cinco grupos taxonómicos, ya que un subconjunto de ellos no produciría evaluaciones fiables de la diversidad biológica de la charca. La identificación a nivel de género es necesaria para cuatro de estos grupos (plantas acuáticas, gasterópodos acuáticos, coleópteros acuáticos, y odonatos adultos) y para los anfibios es necesario el nivel de especie. El muestreo sigue un diseño aleatorio estratificado, utilizado en el método PLOCH, pero con una ligera modificación en el número de muestras por charca. La evaluación sigue la metodología adoptada por la Directiva Marco de Aguas, y la relación entre la riqueza observada y la del estado de referencia se traduce en una de las cinco categorías de calidad para cada charca. El índice final es la media de las cinco puntuaciones de la evaluación. Para facilitar la aplicación del método IBEM, un sitio web (http://campus.hesge.ch/ibem) permite cálculo del índice a través de la red y proporciona instrucciones tanto de las metodo­logías de muestreo como de la valoración. Además, los autores han organizado cursos de formación sobre el método para los usuarios

Occurrence of Localized Intense Cation Uptake Sites in the Vascular Rings of Red Beet Storage Tissue 2

Development and decline of cation uptake capacity in discs taken from the vascular and parenchyma rings of storage tissue of red table beet (Beta vulgaris L.) were observed during 12 d of ageing. Uptake capacity for Na+ and Rb+ showed a steady rise reaching maximums by the fourth to fifth days of ageing. Thereafter, there was a steady decline in the uptake rates. Vascular ring tissues were able to develop a greater uptake capacity for both Na+ and Rb+ than the tissues of parenchyma rings. This difference, which was more pronounced for Rb+ than for Na+ uptake, is attributed to a combination of variations in cell density and differences in the acquisition and retention of the cation uptake capacity. Respiration of tissue discs showed no significant rise during ageing, nor were there significant differences in the respiration of vascular and parenchyma tissues. Vascular tissues contained significantly more betacyanin than parenchyma tissues; and they retained their pigment, as well as their acquired cation uptake capacity, for a longer period during the ageing proces

Can skills assessment on a virtual reality trainer predict a surgical trainee's talent in laparoscopic surgery?

Background: A number of studies have investigated several aspects of feasibility and validity of performance assessments with virtual reality surgical simulators. However, the validity of performance assessments is limited by the reliability of such measurements, and some issues of reliability still need to be addressed. This study aimed to evaluate the hypothesis that test subjects show logarithmic performance curves on repetitive trials for a component task of laparoscopic cholecystectomy on a virtual reality simulator, and that interindividual differences in performance after considerable training are significant. According to kinesiologic theory, logarithmic performance curves are expected and an individual's learning capacity for a specific task can be extrapolated, allowing quantification of a person's innate ability to develop task-specific skills. Methods: In this study, 20 medical students at the University of Basel Medical School performed five trials of a standardized task on the LS 500 virtual reality simulator for laparoscopic surgery. Task completion time, number of errors, economy of instrument movements, and maximum speed of instrument movements were measured. Results: The hypothesis was confirmed by the fact that the performance curves for some of the simulator measurements were very close to logarithmic curves, and there were significant interindividual differences in performance at the end of the repetitive trials. Conclusions: Assessment of perceptual motor skills and the innate ability of an individual with no prior experience in laparoscopic surgery to develop such skills using the LS 500 VR surgical simulator is feasible and reliabl

Futility: ein Begriff im chirurgischen Alltag?

Zusammenfassung: Ethisch anspruchsvolle Indikationsstellungen bei Patienten, die ihren Willen nicht selbst äußern können, wie beispielsweise schwer demenzkranke Patienten, konfrontieren uns häufig. Es stellt sich hierbei die Frage, ob wir mit operativen Eingriffen eine Übertherapie vollziehen. Der Begriff "futility" der Medizinethik beschreibt Übertherapie, ist allerdings für eine konkrete Anwendung problematisch, da eine exakte Definition fehlt. In der klinischen Situation von schwer demenzkranken, hochbetagten Patienten muss in chirurgischen Abteilungen eine Aufarbeitung von medizinischem Hintergrund, Lebensumständen des Patienten und belegtem oder mutmaßlichem Patientenwillen erfolgen mit dem Ziel, Indikationen individualisiert zu stellen. Nur so können diese Patienten optimal versorgt werden, eine klare Kommunikation über Behandlungsziele mit Angehörigen stattfinden sowie eine Vermeidung eines "burn out" bei den Behandelnden erreicht werden. Von großem Nutzen ist hierbei eine enge Zusammenarbeit mit Medizinethiker

Simplified placement and management of cutting setons in the treatment of transsphincteric anal fistula: technical note

Background: We report one safe and standardized technique of seton placement and management. Conclusions: A simplified way to manage cutting setons helps to minimize manipulation and may reduce pain. In most patients our technique can be used with no additional anesthesia and in an outpatient settin