Global benchmarks in primary robotic bariatric surgery redefine quality standards for Roux-en-Y gastric bypass and sleeve gastrectomy

BACKGROUND Whether the benefits of the robotic platform in bariatric surgery translate into superior surgical outcomes remains unclear. The aim of this retrospective study was to establish the 'best possible' outcomes for robotic bariatric surgery and compare them with the established laparoscopic benchmarks. METHODS Benchmark cut-offs were established for consecutive primary robotic bariatric surgery patients of 17 centres across four continents (13 expert centres and 4 learning phase centres) using the 75th percentile of the median outcome values until 90 days after surgery. The benchmark patients had no previous laparotomy, diabetes, sleep apnoea, cardiopathy, renal insufficiency, inflammatory bowel disease, immunosuppression, history of thromboembolic events, BMI greater than 50 kg/m2, or age greater than 65 years. RESULTS A total of 9097 patients were included, who were mainly female (75.5%) and who had a mean(s.d.) age of 44.7(11.5) years and a mean(s.d.) baseline BMI of 44.6(7.7) kg/m2. In expert centres, 13.74% of the 3020 patients who underwent primary robotic Roux-en-Y gastric bypass and 5.9% of the 4078 patients who underwent primary robotic sleeve gastrectomy presented with greater than or equal to one complication within 90 postoperative days. No patient died and 1.1% of patients had adverse events related to the robotic platform. When compared with laparoscopic benchmarks, robotic Roux-en-Y gastric bypass had lower benchmark cut-offs for hospital stay, postoperative bleeding, and marginal ulceration, but the duration of the operation was 42 min longer. For most surgical outcomes, robotic sleeve gastrectomy outperformed laparoscopic sleeve gastrectomy with a comparable duration of the operation. In robotic learning phase centres, outcomes were within the established benchmarks only for low-risk robotic Roux-en-Y gastric bypass. CONCLUSION The newly established benchmarks suggest that robotic bariatric surgery may enhance surgical safety compared with laparoscopic bariatric surgery; however, the duration of the operation for robotic Roux-en-Y gastric bypass is longer

Facteurs pronostiques de la formation de fistules enteroatmosphériques chez les patients en ventre ouvert et traités par thérapie par pression négative : une expérience multicentrique

La thérapie par pression négative pour les laparostomes permet une réduction de la mortalité. Cependant, certains auteurs ont exprimé leur inquiétude face à un risque accru de fistules enteroatmosphériques. Nous avons émis l'hypothèse que des facteurs métaboliques et chirurgicaux pourraient augmenter l'incidence de ces fistules. Il s'agit d'une étude rétrospective multicentrique des patients traités par thérapie par pression négative entre 2005 et 2015. Les facteurs associés à la formation de fistules enteroatmosphériques ont été inclus dans une analyse multivariée. Cinquante-sept patients ont été inclus et quatorze pour cent ont présenté des fistules enteroatmosphériques. Des lactates artériels préopératoires > 3,5 mmol / L étaient un prédicteur indépendant avec un odds ratio de 12.41 (95% CI 1.54–99.99). L'ischémie mésentérique augmente le risque de fistule entéroatmosphérique. La réalisation d'anastomoses doit être réservée à des patients revascularisés au préalable. Lorsque la vascularisation mésentérique n'est pas rétablie, la confection de stomies est conseillée

A novel equivalence method for high fidelity hybrid stochastic-deterministic neutron transport simulations

Thesis: Ph. D. in Computational Nuclear Science and Engineering, Massachusetts Institute of Technology, Department of Nuclear Science and Engineering, September, 2020Cataloged from student-submitted PDF version of thesis.Includes bibliographical references.With ever increasing available computing resources, the traditional nuclear reactor physics computation schemes, that trade off between spatial, angular and energy resolution to achieve low cost highly-tuned simulations, are being challenged. While existing schemes can reach few-percent accuracy for the current fleet of light water reactors, thanks to a plethora of astute engineering approximations, they cannot provide sufficient accuracy for evolutionary reactor designs with highly heterogeneous geometries. The decades-long process to develop and qualify these simulation tools is also not in phase with the fast-paced development of innovative new reactor designs seeking to address the climate crisis. Enabled by those computing resources, high fidelity Monte Carlo methods can easily tackle challenging geometries, but they lack the computational and algorithmic efficiency of deterministic methods. However, they are increasingly being used for group cross section generation. Downstream highly parallelized 3D deterministic transport can then use those cross sections to compute accurate solutions at the full core scale. This hybrid computation scheme makes the most of both worlds to achieve fast and accurate reactor physics simulations. Among the few remaining approximations are neglecting the angular dependence of group cross sections, which lead to an over-estimation of resonant absorption rates, especially for the lower resonances of ²³⁸U. This thesis presents a novel equivalence method based on introducing discontinuities in the track angular fluxes, with a polar dependence of discontinuity factors to preserve the polar dependence of the neutron currents as well as removing the self-shielding error. This new method is systematically benchmarked against the state-of-the-art method, SuPerHomogenization in three different approaches to obtaining equivalence factors: a same-scale iterative approach, a multiscale approach, and a single-step non-iterative approach. Both methods show remarkable agreement with a reference Monte Carlo solution on a wide array of test cases, from 2D pin cells to 3D full core calculations, for the iterative and the multi-scale approaches. The self-shielding error is eliminated, improving significantly the predictive capabilities of the scheme for the distribution of ²³⁸U absorption in the core. A single-step non-iterative approach to obtaining equivalence factors is also pursued, and was shown to only be adequate with the novel discontinuity factor-based method. This study is largely enabled by a significant optimization effort of the 3D deterministic neutron transport solver. By leveraging low level parallelism through vectorization of the multi-group neutron transport equation, by increasing the memory locality of the method of characteristics implementation and with a novel inter-domain communication algorithm enabling a near halving of memory requirements, the 3D full core case can now be tackled with only 50 nodes on an industrial sized computing cluster rather than the many thousands of nodes on a TOP20 supercomputer used previously. This thesis presents fully resolved solutions to the steady-state multi-group neutron transport equation for full-core 3D light water reactors, and these solutions are comparable to gold-standard continuous-energy Monte Carlo solutions.by Guillaume Louis Giudicelli.Ph. D. in Computational Nuclear Science and EngineeringPh. D. in Computational Nuclear Science and Engineering Massachusetts Institute of Technology, Department of Nuclear Science and Engineerin

Achievable power uprates in pressurized water reactors using uranium nitride fuel

Thesis: S.M., Massachusetts Institute of Technology, Department of Nuclear Science and Engineering, 2017.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from student-submitted PDF version of thesis.Includes bibliographical references (pages 85-88).This work aims at investigating the potential benefits of nitride fuel use in pressurized water reactors. The AP1000 is chosen as the reference power plant. Both oxide and nitride fuel are considered and compared using a steady state thermal hydraulics and mechanics parametric optimization study to achieve a maximal core power. A subsequent neutronics study determined the achievable energy extracted per fuel mass (burnup) and sets the core power that allows for an 18-months fuel cycle length. The impact of the change in the core operating temperature on the steam cycle efficiency is considered in order to provide a final evaluation of the electric power uprate. The steady state limits considered are pressure drop, minimum departure from nucleate boiling ratio, fretting and sliding wear and fuel average and centerline temperatures. These limits were set by the reference design's performance. Two strategies were used to raise the core power while remaining within specified limits: increasing the core mass flow rate and decreasing the core inlet temperature. These two strategies were implemented in a simplified MATLAB tool using correlations and a MATLAB-VIPRE (subchannel simulation tool) interface to better model cross-flows. Designs with smaller pins but with similar pitch-todiameter ratios compared to the reference design were found to be optimal with regards to these performances for both strategies. Fretting wear was found to be the limiting constraint for these designs for the first strategy, and additional spacer grids can be introduced to reduce fretting wear and to allow a further power increase. MDNBR was found to be the limiting constraint for these designs in the second strategy. The fuel temperature was not limiting for these designs and both oxide and nitride fuel can be utilized with the same uprates. Both tools provided similar results: smaller fuel pins with similar pitch over diameter ratios allow for better performances than the nominal design in the aforementioned criteria. The most promising strategy proved to be decreasing the core inlet temperature. With this strategy, the possible uprate is 16%, or 550 MWth, in both tools. Such an uprate requires an additional steam generator, and when lowering the core inlet temperature the efficiency of the steam cycle is lowered by 1% as we also need to lower the steam generator saturation pressure. This will require a larger high-pressure turbine. The optimized nitride-fueled design was compared with the oxide-fueled nominal core in terms of neutronics performances. I showed that the new design can reach an 18 month cycle length, at an uprated power, with a 4.3% enrichment and a 60 assembly feed using uranium nitride, compared with a 4.6% enrichment and a 68 assembly feed for the nominal design at the nominal power. With a higher enrichment and a higher feed, a two-year cycle length can be reached even with the uprate. The moderator temperature coefficient, the shutdown margin and the power coefficient of both designs satisfied licensing requirements. A 5% increase in fuel cycle costs was noted with the nitride optimized core, minor compared to the revenue of a 150 MWe uprate. Transient performances, and more extensive fuel performance studies are left for future studies.by Guillaume Giudicelli.S.M

CONTRAINTES DE LA SITUATION TRANSCULTURELLE POUR L'APPROCHE MEDICO-PSYCHIATRIQUE D'ENFANTS PSYCHOTIQUES ISSUS DE SOCIETES NON-OCCIDENTALES (REFLEXIONS ET ANALYSES AUTOUR DE TROIS OBSERVATIONS D'ENFANTS SENEGALAIS PRESENTANT DES TROUBLES GRAVES DU COMPORTEMENT ET DE LA COMMUNICATION (DES PSYCHIATRIE))

AIX-MARSEILLE2-BU Méd/Odontol. (130552103) / SudocPARIS-BIUM (751062103) / SudocSudocFranceF

Global Benchmark Values for Laparoscopic Roux-en-Y-Gastric Bypass: a Potential New Indicator of the Surgical Learning Curve

Background: Laparoscopic Roux-en-Y gastric bypass (LRYGB) is a technically demanding procedure. The learning curve of LRYGB is challenging and potentially associated with increased morbidity. This study evaluates whether a general laparoscopic surgeon can be safely trained in performing LRYGB in a peripheral setting, by comparing perioperative outcomes to global benchmarks and to those of a senior surgeon. Methods: All consecutive patients undergoing primary LRYGB between January 2014 and December 2017 were operated on by a senior (A) or a trainee (B) bariatric surgeon and were prospectively included. The main outcome of interest was all-cause morbidity at 90 days. Perioperative outcomes were compared with global benchmarks pooled from 19 international high-volume centers and between surgeons A and B for their first and last 30 procedures. Results: The 213 included patients had a mean all-cause morbidity rate at 90 days of 8% (17/213). 95.3% (203/213) of the patients were uneventfully discharged after surgery. Perioperative outcomes of surgeon B were all within the global benchmark cutoffs. Mean operative time for the first 30 procedures was significantly shorter for surgeon A compared with surgeon B, with 108.6 min (± 21.7) and 135.1 min (± 28.1) respectively and decreased significantly for the last 30 procedures to 95 min (± 33.7) and 88.8 min (± 26.9) for surgeons A and B respectively. Conclusion: Training of a new bariatric surgeon did not increase morbidity and operative time improved for both surgeons. Perioperative outcomes within global benchmarks suggest that it may be safe to teach bariatric surgery in peripheral settin

Generalized equivalence methods for 3D multi-group neutron transport

The process of generating multi-group cross section data to be used in full core 3D transport models requires not only accurate resonance self-shielding methods, but also some form of equivalence method in order to precisely preserve reaction rates of spectral geometry calculations. This paper presents extensions of the traditional concepts of local reaction rate preservation (common in discontinuity factor, SPH, and BBH methods), to derive a new state-of-the-art transport equivalence method that incorporates angular flux jump conditions that provide polar angle neutron current preservation. This method is tested on numerous fixed-source pin-cell problems by condensing fine energy resonance fluxes and cross sections. The method is demonstrated to precisely preserve all spectral geometry multi-group reaction rates as well as polar angle neutron currents for a wide range of cross section resonance heights, fuel pin diameters, coolant densities, and group energy widths. Keywords: Neutron transport; Self-shielding; Equivalence; Condensation; Discontinuity factors; Jump conditionsUnited States. Department of Energy. Nuclear Energy University Program (Grant DE-NE0008578

Is an Early Resumption of a Regular Diet After Laparoscopic Roux-en-Y Gastric Bypass Safe?

BACKGROUND: Return to a normal diet is a crucial step after bariatric surgery. Proximal anastomosis is a source of concern for early feeding as the passage of solid food through a recent anastomosis could well increase pressure and the risk of leakage. This study aims to assess the safety of an early normal diet after a laparoscopic Roux-en-Y gastric bypass (LRYGB). MATERIALS AND METHODS: All consecutive patients undergoing primary LRYGB between January 2015 and December 2020 were included prospectively. Three postoperative pureed diets were compared at 4 weeks, 2 weeks, and 1 week. All-cause morbidity at 90 days was the main outcome. Overall complications, severe complications (Clavien-Dindo ≥ grade 3a), length of hospital stay, number of emergency, and unplanned consultations during the 3 postoperative months were recorded for each group. RESULTS: Three hundred and sixty-seven patients with a mean BMI of 42.10 kg/m(2) (± SD: 4.78) were included. All-cause morbidity at 90 days was 11.7% (43/367) and no significant difference was observed between the 3 groups. Adjustment for patients and operative cofounders did not demonstrate any increased risk of postoperative complications between the 3 groups, with an odds ratio of 1, 1.23(95% CI [0. 55–2.75]), and 1.14 (95% CI [0.49, 2.67]) for groups 1, 2, and 3 respectively. Severe complications (Clavien-Dindo ≥ grade 3a) and emergency or unplanned consultations were also similar in the 3 groups. CONCLUSION: Return to a normal diet 1 week after LRYGB did not increase short-term morbidity and unplanned consultations. It may be safe and contribute to patient comfort. GRAPHICAL ABSTRACT: [Image: see text