Parathyroid hormone serum concentration kinetic profile in critically ill patients undergoing continuous renal replacement therapies: a prospective observational study

Introduction: Elevated serum parathormone (PTH) levels have been observed in acute kidney injury and are related to calcium-phosphate metabolism disturbance, decreased renal production of 1,25 dihydroxyvitamin D3, impaired renal PTH excretion, and other renal-independent factors. There are no data regarding PTH concentration kinetics in critically ill patients undergoing continuous renal replacement therapies (CRRT) in an intensive care setting. The primary objective of this study was to investigate trends in PTH serum levels in critically ill patients with multiorgan failure undergoing CRRT, by performing periodic PTH measurements in the acute phase of critical illness. Material and methods: This was a single-centre, prospective, observational study conducted in an mixed, university-affiliated intensive care unit. Critically ill patients who fulfilled all of the following criteria were included: respiratory failure; circulatory failure; acute kidney injury treated by CRRT; and sequential organ failure assessment score (SOFA score) of 5 or more. Patients who met any of the following criteria were excluded: acute liver failure; hypercalcemia at admission (total calcium serum level > 10.6 mg/dL; total ionized calcium plasma level > 1.35 mmol/L); parathyroid gland disease; end-stage renal disease; patients undergoing therapeutic plasma exchange or extracorporeal membrane oxygenation procedures; aged under 18 years;  pregnant; and life expectancy after admission to the intensive care unit anticipated to be less than 72 hours as assessed by the investigator. Results: Thirty patients met the inclusion criteria. A statistically significant change in PTH over time was observed (Friedman ANOVA; p = 0.0001). The post-hoc test showed a statistically significant decrease in PTH: measurements 5–8 relative to measurement 1, and measurements 4–8 relative to measurement 2 (p < 0.05). No significant correlations between 25 hydroxyvitamin D3 deficiency, age, diagnosis, SOFA score, and PTH levels were observed. A statistical test indicated that serum concentrations of PTH were significantly higher in the de novo sepsis group (p < 0.05). Conclusions: The PTH serum concentration decreases during the course of CRRT in the majority of patients. When the course of the disease starts to be complicated by sepsis, PTH serum levels then remain high. A probable reason for this is the existence of the inflammatory state triggered by sepsis

Complexes excitoniques dans les boîtes quantiques naturelles dans des structures GaAs/A1As de type II

Des boîtes quantiques à fort confinement tridimensionnel et de très basse densité (106cm-2) ont été démontrées dans des structures qui ont été originellement développées comme des double puits quantique de GaAs/AIAs avec des barrières de GaAIAs. Le fait que ces structures soient de type Il permet de détecter les boîtes quantiques très facilement grâce à la très longue durée de vie des excitons indirects (de l'ordre de quelques millisecondes) et à leur capacité à diffuser efficacement Uusqu'à 100j.lm) dans les pièges zéro dimensionnels. Cet effet est généralement difficile à obtenir dans les structures directes. Les boites quantiques peuvent donc être facilement remplies par des excitons, provoquant la formation, non seulement d'excitons, mais aussi d'excitons chargés et de biexcitons,et également de molécules excitoniques plus complexes montrant un caractère zéro dimensionnel. Ce travail est consacré à l'étude des complexes excitoniques fortement confinés, à leur nature et aux processus permettant leur formation.Nous présentons des études spectroscopiques de l'émission d'une boîte quantique unique sous différentes conditions d'excitation et détectée de différentes manières.La possibilité de contrôler optiquement le nombre d'électrons et de trous qui occupent les niveaux discrets des boites quantiques nous a permis d'étudier la formation de complexes multi-excitoniques en fonction de la densités d'excitons. Les effets observés sont décrits par le modèle de la normalisation des bandes d'énergie comprenant les effets multi-corps, les interactions d'échange et les effets de corrélation.L'influence d'un champ magnétique sur les complexes multi-excitoniques est d'abord discutée. De manière générale, il est montré comment l'application d'un champ magnétique modifie la structure énergétique des transitions observées. Des propriétés typiques de boîtes quantiques telles que l'effet Zeeman, décalage diamagnétique et l'énergie de liaison excitonique sont discutées. Ces études ont permis une analyse de la symétrie et de la taille du potentiel de confinement des boîtes.Ensuite, les mécanismes de capture d'excitons dans les boîtes sont considérés. Le rôle important des processus de diffusion contribuant au temps de relaxation de l'émission des boîtes quantiques uniques est discuté sur la base d'expériences de spectroscopie résolue en temps.Le rôle des processus radiatifs et non radiatifs dans l'émission de complexes multi-excitoniques est montré dans l'émission thermiquement activée de boîtes quantiques uniques.Les mesures de corrélation de photon ont permis la classification des différentes lignes d'émission des complexes multi-excitoniques, d'étude du caractère de mécanisme de capture des porteurs photo-créés et la dynamique des fluctuations de charge caractéristiques d'une boîte quantique unique.L'approche expérimentale à un problème de boite quantique unique est largement discutée et des modèles théoriques sont appliqués pour décrire les effets observés.Quantum dots with strong three dimensional confinement and low surface density 106cm-2 have been identified in a structure which was nominally grown as a type Il GaAs/AIAs bilayer surrounded by GaAIAs barriers. The unique type Il system makes the dots easy to detect due to characteristic, very long-lived (ms range) indirect two-dimensional excitons. The 2D excitons efficiently diffuse (up to 100j.lm) into zero-dimensional traps, which is difficult to obtain in conventional, direct type structures. The dots can therefore be effectively filled by excitons, giving rise to the formation of not only excitons, charged excitons and biexcitons, but also more complex excitonic molecules which show a multiple zero-dimensional shell structure.This work is devoted to investigations of the nature, process of formation and interactions in the strongly confined exciton complexes system.Spectroscopie studies of single quantum dot emission under different conditions of excitation and detection are presented.The possibility of optically controlling the number of electrons and holes populating the discrete dot energy levels allows a discussion of the exciton complexes formation depending on exciton densities. The observed effects are described in the band-gap renormalisation model including many-body, exchange, and correlation type interactions.The influence of a magnetic field on the exciton complexes is discussed. ln general, it is shown how the application of a magnetic fjeld modifies the energy structure of the observed transitions. Typical quantum dot properties such as Zeeman splitting, diamagnetic shift, anc exciton binding energy are discussed. They allowed an analysis of the symmetry and size of the dots' confining potential.Moreover, the mechanisms of exciton capture in the dots are considered. The important role of diffusion processes revealed in single dot time resolved experiments is discussed.The role of radiative and non-radiative processes in the multiexciton emission is shown in temperature activated emission from a single dot.Photon correlation experiments allowed to classify the number of multiexciton emission lines, to study the character of capture of photocreated carriers, and to investigate the dynamics of charge fluctuations characteristic of a single quantum object.The experimental approach to a single quantum dot problem is widely discussed, and theoretical models are applied to describe the observed effects.GRENOBLE1-BU Sciences (384212103) / SudocSudocFranceF

Establishing a New ECMO Referral Center Using an ICU-Based Approach: A Feasibility and Safety Study

Background: A high-volume center with a multidisciplinary team is regarded as the optimal place for providing extracorporeal membrane oxygenation (ECMO). We hypothesize that an ECMO center can also be successfully created and subsequently developed entirely by intensivists in a mid-size mixed intensive care unit (ICU). Methods: A model was created for setting up a new ECMO referral center within the structure of an existing mixed ICU in a tertiary hospital. A retrospective analysis was carried out of the first 33 patients treated in the initial period of the center’s activity, from mid 2018 to the end of 2020. Results: An ECMO center was established and developed entirely based on the resources of an existing mixed ICU. Thirty-three patients were treated. They had an overall survival rate at 90 days of 60.6%. In veno-venous (VV) mode ECMO duration, ICU length of stay, and SOFA score were significantly higher than in veno-arterial mode. No significant differences in clinical characteristics were observed between survivors and non-survivors on VV-ECMO. Conclusions: A regional ECMO center can be set up as an integral part of a mixed ICU in a tertiary hospital. Extracorporeal therapy, such as continuous renal replacement therapy and mechanical ventilation can be managed entirely by intensivists. Further studies are needed to show that the ICU-based approach to setting up a new ECMO center is no less effective than the multidisciplinary approach