Peri-operative red blood cell transfusion in neonates and infants: NEonate and Children audiT of Anaesthesia pRactice IN Europe: A prospective European multicentre observational study

BACKGROUND: Little is known about current clinical practice concerning peri-operative red blood cell transfusion in neonates and small infants. Guidelines suggest transfusions based on haemoglobin thresholds ranging from 8.5 to 12 g dl-1, distinguishing between children from birth to day 7 (week 1), from day 8 to day 14 (week 2) or from day 15 (≥week 3) onwards. OBJECTIVE: To observe peri-operative red blood cell transfusion practice according to guidelines in relation to patient outcome. DESIGN: A multicentre observational study. SETTING: The NEonate-Children sTudy of Anaesthesia pRactice IN Europe (NECTARINE) trial recruited patients up to 60 weeks' postmenstrual age undergoing anaesthesia for surgical or diagnostic procedures from 165 centres in 31 European countries between March 2016 and January 2017. PATIENTS: The data included 5609 patients undergoing 6542 procedures. Inclusion criteria was a peri-operative red blood cell transfusion. MAIN OUTCOME MEASURES: The primary endpoint was the haemoglobin level triggering a transfusion for neonates in week 1, week 2 and week 3. Secondary endpoints were transfusion volumes, 'delta haemoglobin' (preprocedure - transfusion-triggering) and 30-day and 90-day morbidity and mortality. RESULTS: Peri-operative red blood cell transfusions were recorded during 447 procedures (6.9%). The median haemoglobin levels triggering a transfusion were 9.6 [IQR 8.7 to 10.9] g dl-1 for neonates in week 1, 9.6 [7.7 to 10.4] g dl-1 in week 2 and 8.0 [7.3 to 9.0] g dl-1 in week 3. The median transfusion volume was 17.1 [11.1 to 26.4] ml kg-1 with a median delta haemoglobin of 1.8 [0.0 to 3.6] g dl-1. Thirty-day morbidity was 47.8% with an overall mortality of 11.3%. CONCLUSIONS: Results indicate lower transfusion-triggering haemoglobin thresholds in clinical practice than suggested by current guidelines. The high morbidity and mortality of this NECTARINE sub-cohort calls for investigative action and evidence-based guidelines addressing peri-operative red blood cell transfusions strategies. TRIAL REGISTRATION: ClinicalTrials.gov, identifier: NCT02350348

Melt inclusions : from crystal growth kinetics to planetary-bodies formation

Décrypter les mécanismes et cinétiques de croissance et dissolution des minéraux dans les liquides silicatés est indispensable à la compréhension des processus magmatiques fondamentaux. La migration transcristalline des inclusions magmatiques sous l'effet d'un gradient thermique permet de quantifier une loi cinétique de croissance et dissolution du minéral hôte dans des conditions proches de celles qui prévalent le plus souvent dans la nature. L'objectif principal de ce travail de thèse était : i) d'étudier l'effet de la composition du liquide piégé sur le processus de migration dans l'olivine et ii) d'exploiter systématiquement le processus de migration afin de quantifier les lois cinétiques pour d'autres couples minéral-liquide. Lorsqu'elles sont soumises à un gradient thermique, les inclusions siliceuses (SiO2 ≥ 60pds%) piégées dans les olivines mantelliques et les inclusions basaltiques piégées dans les clinopyroxènes volcaniques migrent à travers leur hôte en direction du point chaud de la zone de travail. La migration s'effectue à une vitesse constante et, dans les olivines, sans modification de la composition du liquide piégé ; les inclusions des clinopyroxènes subissent en revanche une rééquilibration chimique transitoire en début de migration. Les cavités, subsphériques avant la migration, évoluent vers la forme en cristal-négatif du minéral hôte en cours d'expérience. L'achèvement de l'évolution morphologique nécessite un temps caractéristique gouverné par la diffusion chimique dans le liquide. La bulle de gaz exsolvé dans les inclusions n'est pas entraînée dans la migration. Elle se sépare du liquide magmatique et donne naissance à une inclusion fluide isolée au sein du cristal hôte. Les résultats expérimentaux indiquent que la migration procède par dissolution du minéral hôte à l'avant et recristallisation à l'arrière de l'inclusion. La vitesse de migration est limitée par les mécanismes à l'interface cristal-liquide, non par la diffusion chimique. Les taux de croissance et dissolution de l'olivine et du clinopyroxène que nous obtenons sont respectivement trente et quinze fois inférieurs à ceux déterminés dans une étude antérieure à partir d'expériences de migration d'inclusions basaltiques dans des olivines volcaniques. Ils obéissent cependant à la même forme de loi cinétique, qui peut être aisément transposée à des environnements de cristallisation ou de fusion naturels, similaires ou de plus faible déséquilibre. Le taux de croissance et dissolution de l'olivine lors des migrations n'a pas de lien simple avec la composition du liquide piégé ; il est peut-être aussi en grande partie contrôlé par la densité de dislocations du cristal hôte. Le phénomène de migration n'a pas été observé dans le quartz et le plagioclase pour les durées d'expériences réalisées. Il est néanmoins probable que l'absence de migration lors des expériences ne soit qu'apparente. Notamment, la prédominance de liaisons de forte énergie dans la structure du quartz et du plagioclase est susceptible de rendre les processus interfaciaux, et donc aussi la dissolution, particulièrement lente. Au cours de ce travail de thèse, l'opportunité s'est présentée d'étudier les inclusions magmatiques piégées dans les cristaux d'olivine de la pallasite Brahin. En particulier, deux familles d'inclusions ont été identifiées. La première consiste en des plans d'inclusions secondaires contenant de nombreuses chromites et des assemblages à métal-sulfure et olivine phosphorée ; la seconde correspond à des inclusions isolées renfermant pour la plupart de la stanfieldite, une bulle de gaz et de l'olivine phosphorée. Les inclusions secondaires se seraient formées suite à un choc ayant eu lieu alors que l'assemblage minéralogique actuel de Brahin était déjà formé, ou en cours de formation. En revanche, les inclusions de stanfieldite témoigneraient d'un choc prépallasitique.Deciphering the mechanisms and kinetics of crystal growth and dissolution in silicate melts is essential for understanding the fundamental magmatic processes. When remelted and subjected to an imposed thermal gradient, melt inclusions migrate through their host, which provides a direct access to the host crystal growth / dissolution kinetics and allows to quantify the kinetic laws at very low undercoolings or overheatings, i.e. in conditions appropriate to many natural systems. The main goal of the present study was: i) to study the effect of the trapped melt composition on the migration process in olivine and ii) to extend the transcrystalline melt migration approach to quantify the kinetic law for other mineral-melt pairs. When subjected to a thermal gradient, Si-rich melt inclusions (SiO2 ≥ 60 wt%) in mantle olivines and basaltic melt inclusions in volcanic clinopyroxenes migrate through their host toward the host spot of the working zone. Migration proceeds at a constant rate and in olivine, without modification of the trapped melt composition ; melt inclusions in clinopyroxene, however, undergo a transient chemical reequilibration while they begin to migrate. While moving, the melt inclusions gradually change from subspherical to a faceted, negative-crystal shape. Completion ofthe morphological evolution requires a characteristic time that is governed by chemical diffusion. When a gas bubble is initially present, it responds to elastic forces by quickly shifting toward the cold end of the inclusion, where it soon becomes engulfed as an isolated fluid inclusion in the reprecipitated crystal. The experimental results indicate that the migration operates by progressive dissolution and recrystallistion of the host, governed by interface kinetics with no interference of chemical diffusion.The growth / dissolution rates we obtained for olivine and clinopyroxene are respectively thirty and fifteen times lower than those determined in a previous study from melt migration experiments on basaltic inclusions in volcanic olivines. Nevertheless, they obey the same form of kinetic law, which can be transposed to equally or more sluggish melting or crystallisation events in nature. Dependence of the growth / dissolution rate of olivine on trapped melt composition is not straightforward ; rates may be largely controlled by the density of dislocations in the host crystal. The melt migration phenomenon was not observed in quartz and plagioclase for the investigated experiment durations. Nonetheless, the lack of migration during experiments may only be apparent. Notably, the dominance of high-strength bonds in the quartz and plagioclase structure may render interfacial reactions, and so dissolution, particularly slow. During this research work, we had the opportunity to study the melt inclusions trapped in olivine crystals from the Brahin pallasite. In particular, two contrasted sets of melt inclusions were evidenced. The first set consists of plans of secondary inclusions containing abundant chromite and assemblies of metal, sulfide, and phosphoran olivine ; the second set corresponds to isolated inclusions consisting for the most part of stanfieldite, a gas bubble, and phosphoran olivine. Secondary inclusions may have formed during a shock event that took place while the current stony-iron assembly of the Brahin pallasite was already formed, or was created by this shock. However, stanfieldite inclusions may originate from a pre-pallasitic shock event

Les inclusions magmatiques : des cinétiques de croissance cristalline à la formation des corps planétaires

Deciphering the mechanisms and kinetics of crystal growth and dissolution in silicate melts is essential for understanding the fundamental magmatic processes. When remelted and subjected to an imposed thermal gradient, melt inclusions migrate through their host, which provides a direct access to the host crystal growth / dissolution kinetics and allows to quantify the kinetic laws at very low undercoolings or overheatings, i.e. in conditions appropriate to many natural systems. The main goal of the present study was: i) to study the effect of the trapped melt composition on the migration process in olivine and ii) to extend the transcrystalline melt migration approach to quantify the kinetic law for other mineral-melt pairs. When subjected to a thermal gradient, Si-rich melt inclusions (SiO2 ≥ 60 wt%) in mantle olivines and basaltic melt inclusions in volcanic clinopyroxenes migrate through their host toward the host spot of the working zone. Migration proceeds at a constant rate and in olivine, without modification of the trapped melt composition ; melt inclusions in clinopyroxene, however, undergo a transient chemical reequilibration while they begin to migrate. While moving, the melt inclusions gradually change from subspherical to a faceted, negative-crystal shape. Completion ofthe morphological evolution requires a characteristic time that is governed by chemical diffusion. When a gas bubble is initially present, it responds to elastic forces by quickly shifting toward the cold end of the inclusion, where it soon becomes engulfed as an isolated fluid inclusion in the reprecipitated crystal. The experimental results indicate that the migration operates by progressive dissolution and recrystallistion of the host, governed by interface kinetics with no interference of chemical diffusion.The growth / dissolution rates we obtained for olivine and clinopyroxene are respectively thirty and fifteen times lower than those determined in a previous study from melt migration experiments on basaltic inclusions in volcanic olivines. Nevertheless, they obey the same form of kinetic law, which can be transposed to equally or more sluggish melting or crystallisation events in nature. Dependence of the growth / dissolution rate of olivine on trapped melt composition is not straightforward ; rates may be largely controlled by the density of dislocations in the host crystal. The melt migration phenomenon was not observed in quartz and plagioclase for the investigated experiment durations. Nonetheless, the lack of migration during experiments may only be apparent. Notably, the dominance of high-strength bonds in the quartz and plagioclase structure may render interfacial reactions, and so dissolution, particularly slow. During this research work, we had the opportunity to study the melt inclusions trapped in olivine crystals from the Brahin pallasite. In particular, two contrasted sets of melt inclusions were evidenced. The first set consists of plans of secondary inclusions containing abundant chromite and assemblies of metal, sulfide, and phosphoran olivine ; the second set corresponds to isolated inclusions consisting for the most part of stanfieldite, a gas bubble, and phosphoran olivine. Secondary inclusions may have formed during a shock event that took place while the current stony-iron assembly of the Brahin pallasite was already formed, or was created by this shock. However, stanfieldite inclusions may originate from a pre-pallasitic shock event.Décrypter les mécanismes et cinétiques de croissance et dissolution des minéraux dans les liquides silicatés est indispensable à la compréhension des processus magmatiques fondamentaux. La migration transcristalline des inclusions magmatiques sous l'effet d'un gradient thermique permet de quantifier une loi cinétique de croissance et dissolution du minéral hôte dans des conditions proches de celles qui prévalent le plus souvent dans la nature. L'objectif principal de ce travail de thèse était : i) d'étudier l'effet de la composition du liquide piégé sur le processus de migration dans l'olivine et ii) d'exploiter systématiquement le processus de migration afin de quantifier les lois cinétiques pour d'autres couples minéral-liquide. Lorsqu'elles sont soumises à un gradient thermique, les inclusions siliceuses (SiO2 ≥ 60pds%) piégées dans les olivines mantelliques et les inclusions basaltiques piégées dans les clinopyroxènes volcaniques migrent à travers leur hôte en direction du point chaud de la zone de travail. La migration s'effectue à une vitesse constante et, dans les olivines, sans modification de la composition du liquide piégé ; les inclusions des clinopyroxènes subissent en revanche une rééquilibration chimique transitoire en début de migration. Les cavités, subsphériques avant la migration, évoluent vers la forme en cristal-négatif du minéral hôte en cours d'expérience. L'achèvement de l'évolution morphologique nécessite un temps caractéristique gouverné par la diffusion chimique dans le liquide. La bulle de gaz exsolvé dans les inclusions n'est pas entraînée dans la migration. Elle se sépare du liquide magmatique et donne naissance à une inclusion fluide isolée au sein du cristal hôte. Les résultats expérimentaux indiquent que la migration procède par dissolution du minéral hôte à l'avant et recristallisation à l'arrière de l'inclusion. La vitesse de migration est limitée par les mécanismes à l'interface cristal-liquide, non par la diffusion chimique. Les taux de croissance et dissolution de l'olivine et du clinopyroxène que nous obtenons sont respectivement trente et quinze fois inférieurs à ceux déterminés dans une étude antérieure à partir d'expériences de migration d'inclusions basaltiques dans des olivines volcaniques. Ils obéissent cependant à la même forme de loi cinétique, qui peut être aisément transposée à des environnements de cristallisation ou de fusion naturels, similaires ou de plus faible déséquilibre. Le taux de croissance et dissolution de l'olivine lors des migrations n'a pas de lien simple avec la composition du liquide piégé ; il est peut-être aussi en grande partie contrôlé par la densité de dislocations du cristal hôte. Le phénomène de migration n'a pas été observé dans le quartz et le plagioclase pour les durées d'expériences réalisées. Il est néanmoins probable que l'absence de migration lors des expériences ne soit qu'apparente. Notamment, la prédominance de liaisons de forte énergie dans la structure du quartz et du plagioclase est susceptible de rendre les processus interfaciaux, et donc aussi la dissolution, particulièrement lente. Au cours de ce travail de thèse, l'opportunité s'est présentée d'étudier les inclusions magmatiques piégées dans les cristaux d'olivine de la pallasite Brahin. En particulier, deux familles d'inclusions ont été identifiées. La première consiste en des plans d'inclusions secondaires contenant de nombreuses chromites et des assemblages à métal-sulfure et olivine phosphorée ; la seconde correspond à des inclusions isolées renfermant pour la plupart de la stanfieldite, une bulle de gaz et de l'olivine phosphorée. Les inclusions secondaires se seraient formées suite à un choc ayant eu lieu alors que l'assemblage minéralogique actuel de Brahin était déjà formé, ou en cours de formation. En revanche, les inclusions de stanfieldite témoigneraient d'un choc prépallasitique

Transcrystalline melt migration in clinopyroxene

International audienc

Serpentinite with and without brucite: A reaction pathway analysis of a natural serpentinite in the Josephine ophiolite, California

A partially serpentinized peridotite from the Josephine ophiolite has been studied in detail in order to characterize the chemical processes of its serpentinization. The original rock was harzburgite, and its olivine and orthopyroxene are partially replaced by veins and patches of lizardite serpentine and magnetite; brucite and talc are completely absent from the serpentinite, regardless of whether the precursor mineral was olivine or pyroxene. Petrographic and mineral-chemical data suggest at least two phases of serpentinization. Incipient serpentinization produced lizardite and magnetite veinlets, from preferential dissolution of orthopyroxene, and/or infiltration of a silica-rich fluid. No talc or brucite was produced, which suggests this serpentinization happened in a chemically open system. Later serpentinization was from a fluid closer to Fe-Mg-Si chemical equilibrium with the harzburgite, which should in theory favor formation of a brucite-bearing serpentinite. Brucite is absent from late serpentine veins, but they have some porosity which could represent former brucite that was dissolved out or was reacted out after serpentinization. Isocon modeling suggests that Si, Fe, and K were added during serpentinization and that Ca was lost; i.e., the serpentinization was not isochemical (except for H2O). Results of petrographic observations, thermodynamic modeling, and mass balance calculations were used to constrain the reactions for global serpentinization of the studied sample. These reactions indicate that water with a concentration of H2 up to two times that of deep sea vent fluids may have been produced during the serpentinization of the Josephine peridotite, which could then have been a potential host for significant biomass

Morbidity and mortality after anaesthesia in early life: results of the European prospective multicentre observational study, neonate and children audit of anaesthesia practice in Europe (NECTARINE)

Background: Neonates and infants requiring anaesthesia are at risk of physiological instability and complications, but triggers for peri-anaesthetic interventions and associations with subsequent outcome are unknown. Methods: This prospective, observational study recruited patients up to 60 weeks' postmenstrual age undergoing anaesthesia for surgical or diagnostic procedures from 165 centres in 31 European countries between March 2016 and January 2017. The primary aim was to identify thresholds of pre-determined physiological variables that triggered a medical intervention. The secondary aims were to evaluate morbidities, mortality at 30 and 90 days, or both, and associations with critical events. Results: Infants (n=5609) born at mean (standard deviation [sd]) 36.2 (4.4) weeks postmenstrual age (35.7% preterm) underwent 6542 procedures within 63 (48) days of birth. Critical event(s) requiring intervention occurred in 35.2% of cases, mainly hypotension (>30% decrease in blood pressure) or reduced oxygenation (SpO2 <85%). Postmenstrual age influenced the incidence and thresholds for intervention. Risk of critical events was increased by prior neonatal medical conditions, congenital anomalies, or both (relative risk [RR]=1.16; 95% confidence interval [CI], 1.04-1.28) and in those requiring preoperative intensive support (RR=1.27; 95% CI, 1.15-1.41). Additional complications occurred in 16.3% of patients by 30 days, and overall 90-day mortality was 3.2% (95% CI, 2.7-3.7%). Co-occurrence of intraoperative hypotension, hypoxaemia, and anaemia was associated with increased risk of morbidity (RR=3.56; 95% CI, 1.64-7.71) and mortality (RR=19.80; 95% CI, 5.87-66.7). Conclusions: Variability in physiological thresholds that triggered an intervention, and the impact of poor tissue oxygenation on patient's outcome, highlight the need for more standardised perioperative management guidelines for neonates and infants

Difficult tracheal intubation in neonates and infants. NEonate and Children audiT of Anaesthesia pRactice IN Europe (NECTARINE): a prospective European multicentre observational study

International audienceBackground: Neonates and infants are susceptible to hypoxaemia in the perioperative period. The aim of this study was to analyse interventions related to anaesthesia tracheal intubations in this European cohort and identify their clinical consequences.Methods: We performed a secondary analysis of tracheal intubations of the European multicentre observational trial (NEonate and Children audiT of Anaesthesia pRactice IN Europe [NECTARINE]) in neonates and small infants with difficult tracheal intubation. The primary endpoint was the incidence of difficult intubation and the related complications. The secondary endpoints were the risk factors for severe hypoxaemia attributed to difficult airway management, and 30 and 90 day outcomes.Results: Tracheal intubation was planned in 4683 procedures. Difficult tracheal intubation, defined as two failed attempts of direct laryngoscopy, occurred in 266 children (271 procedures) with an incidence (95% confidence interval [CI]) of 5.8% (95% CI, 5.1-6.5). Bradycardia occurred in 8% of the cases with difficult intubation, whereas a significant decrease in oxygen saturation (SpO2<90% for 60 s) was reported in 40%. No associated risk factors could be identified among co-morbidities, surgical, or anaesthesia management. Using propensity scoring to adjust for confounders, difficult anaesthesia tracheal intubation did not lead to an increase in 30 and 90 day morbidity or mortality.Conclusions: The results of the present study demonstrate a high incidence of difficult tracheal intubation in children less than 60 weeks post-conceptual age commonly resulting in severe hypoxaemia. Reassuringly, the morbidity and mortality at 30 and 90 days was not increased by the occurrence of a difficult intubation event