Substituent-Guided Cluster Nuclearity for Tetranuclear Iron(III) Compounds with Flat {Fe4(µ3-O)2} Butterfly Core.

The tetranuclear iron(III) compounds [Fe4(µ3-O)2(µ-LZ)4] (1-3) were obtained by reaction of FeCl3 with the shortened salen-type N2O2 tetradentate Schiff bases N,N'-bis(salicylidene)-o-Z-phenylmethanediamine H2LZ (Z = NO2, Cl and OMe, respectively), where the one-carbon bridge between the two iminic nitrogen donor atoms guide preferentially to the formation of oligonuclear species, and the ortho position of the substituent Z on the central phenyl ring selectively drives towards Fe4 bis-oxido clusters. All compounds show a flat almost-symmetric butterfly-like conformation of the {Fe4(µ3-O)2} core, surrounded by the four Schiff base ligands, as depicted by both the X-ray molecular structures of 1 and 2 and the optimized geometries of all derivatives as obtained by UM06/6-311G(d) DFT calculations. The strength of the antiferromagnetic exchange coupling constants between the iron(III) ions varies among the three derivatives, despite their magnetic cores remain structurally almost unvaried, as well as the coordination of the metal ions, with a distorted octahedral environment for the two-body iron ions, Feb, and a pentacoordination with trigonal bipyramidal geometry for the two-wing iron ions, Few. The different magnetic behavior within the series of examined compounds may be ascribed to the influence of the electronic features of Z on the electron density distribution (EDD) of the central {Fe4(µ3-O)2} core, substantiated by a Quantum Theory of Atoms In Molecules (QTAIM) topological analysis of the EDD, as obtained by UM06 calculations 1-3.

Adult liver transplant anesthesiology practice patterns and resource utilization in the United States: Survey results from the society for the advancement of transplant anesthesia.

INTRODUCTION: Liver transplant anesthesiology is an evolving and expanding subspecialty, and programs have, in the past, exhibited significant variations of practice at transplant centers across the United States. In order to explore current practice patterns, the Quality & Standards Committee from the Society for the Advancement of Transplant Anesthesia (SATA) undertook a survey of liver transplant anesthesiology program directors. METHODS: Program directors were invited to participate in an online questionnaire. A total of 110 program directors were identified from the 2018 Scientific Registry of Transplant Recipients (SRTR) database. Replies were received from 65 programs (response rate of 59%). RESULTS: Our results indicate an increase in transplant anesthesia fellowship training and advanced training in transesophageal echocardiography (TEE). We also find that the use of intraoperative TEE and viscoelastic testing is more common. However, there has been a reduction in the use of veno-venous bypass, routine placement of pulmonary artery catheters and the intraoperative use of anti-fibrinolytics when compared to prior surveys. CONCLUSION: The results show considerable heterogeneity in practice patterns across the country that continues to evolve. However, there appears to be a movement towards the adoption of specific structural and clinical practices.

Safety and Benefit of Transesophageal Echocardiography in Liver Transplant Surgery: A Position Paper From the Society for the Advancement of Transplant Anesthesia (SATA).

More anesthesiologists are routinely using transesophageal echocardiography (TEE) during liver transplant surgery, but the effects on patient outcome are unknown. Transplant anesthesiologists are therefore uncertain if they should undergo additional training and adopt TEE. In response to these clinical questions, the Society for the Advancement of Transplant Anesthesia appointed experts in liver transplantation and who are certified in TEE to evaluate all available published evidence on the topic. The aim was to produce a summary with greater explanatory power than individual reports to guide transplant anesthesiologists in their decision to use TEE. An exhaustive search recovered 51 articles of uncontrolled clinical observations. Topics chosen for this study were effectiveness and safety because they were a major or minor topic in all articles. The pattern of clinical use was a common topic and was included to provide contextual information. Summarized observations showed effectiveness as the ability to make a new and unexpected diagnosis and to direct the choice of clinical management. These were reported in each stage of liver transplant surgery. There were observations that TEE facilitated rapid diagnosis of life-threatening conditions difficult to identify with other types of monitoring commonly used in the operating room. Real-time diagnosis by TEE images made anesthesiologists confident in their choice of interventions, especially those with a high risk of complications such as use of anticoagulants for intracardiac thrombosis. The summarized observations in this systematic review suggest that TEE is an effective form of monitoring with a safety profile similar to that in cardiac surgery patients.

Pathogenic Link Between Postextubation Pneumonia and Ventilator-Associated Pneumonia: An Experimental Study.

BACKGROUND: The presence of an endotracheal tube is the main cause for developing ventilator-associated pneumonia (VAP), but pneumonia can still develop in hospitalized patients after endotracheal tube removal (postextubation pneumonia [PEP]). We hypothesized that short-term intubation (24 hours) can play a role in the pathogenesis of PEP. To test such hypothesis, we initially evaluated the occurrence of lung colonization and VAP in sheep that were intubated and mechanically ventilated for 24 hours. Subsequently, we assessed the incidence of lung colonization and PEP at 48 hours after extubation in sheep previously ventilated for 24 hours. METHODS: To simulate intubated intensive care unit patients placed in semirecumbent position, 14 sheep were intubated and mechanically ventilated with the head elevated 30° above horizontal. Seven of them were euthanized after 24 hours (Control Group), whereas the remaining were euthanized after being awaken, extubated, and left spontaneously breathing for 48 hours after extubation (Awake Group). Criteria of clinical diagnosis of pneumonia were tested. Microbiological evaluation was performed on autopsy in all sheep. RESULTS: Only 1 sheep in the Control Group met the criteria of VAP after 24 hours of mechanical ventilation. However, heavy pathogenic bacteria colonization of trachea, bronchi, and lungs (range, 10-10 colony-forming unit [CFU]/g) was reported in 4 of 7 sheep (57%). In the Awake Group, 1 sheep was diagnosed with VAP and 3 developed PEP within 48 hours after extubation (42%), with 1 euthanized at 30 hours because of respiratory failure. On autopsy, 5 sheep (71%) confirmed pathogenic bacterial growth in the lower respiratory tract (range, 10-10 CFU/g). CONCLUSIONS: Twenty-four hours of intubation and mechanical ventilation in semirecumbent position leads to significant pathogenic colonization of the lower airways, which can promote the development of PEP. Strategies directed to prevent pathogenic microbiological colonization before and after mechanical ventilation should be considered to avert the onset of PEP.

Use of Transesophageal Echocardiography for Liver Transplantation: A Global Comparison of Practice From the ILTS, SATA, and LICAGE.

BACKGROUND: Anesthesiologists frequently use intraoperative transesophageal echocardiography (TEE) to aid in the diagnosis and management of hemodynamic problems during liver transplantation (LT). Although the use of TEE in US centers continues to increase, data regarding international use are lacking. METHODS: This prospective, global, survey-based study evaluates international experience with TEE for LT. Responses from 252 LT (105 US and 147 non-US) centers representing 1789 anesthesiologists were analyzed. RESULTS: Routine use of TEE in the United States has increased in the last 5 y (from 37% to 47%), but only 21% of non-US LT anesthesiologists use TEE routinely. Lack of training (44% US versus 70% non-US) and equipment (9% non-US versus 34% US) were cited as obstacles. Most survey participants preferred not to perform a complete cardiac examination but rather use only 6 of 11 basic views. Although non-US LT anesthesiologists more frequently had additional clinical training than their US counterparts, they had less TEE experience (13% versus 44%) and less frequently, TEE certification (22% versus 35%). Most LT anesthesiologists agreed that TEE certification is essential for proficiency. Of all respondents, 89% agreed or strongly agreed that TEE provides valuable information needed for immediate clinical decision-making, and >86% agreed or strongly agreed that that information could not be derived from other sources. CONCLUSIONS: The use of TEE for LT surgery in the US LT centers is currently higher compared with non-US LT centers. This may become a standard monitoring modality during LT in the near future.

Trapping an unprecedented octacoordinated iron(II) complex with neutral bis-tetrazolylpyridyl ligands and solvent molecules.

Iron(II) can show a very rich coordination chemistry with concomitant modulation of its properties as promising functional materials. Metalation of the neutral tridentate nitrogen-donor mer-coordinating ligand 2,6-bis(2-(methyl)-2H-tetrazol-5-yl)pyridine (Me2btp) with Fe(ClO4)2·6H2O through accurate solvent polarity control enables the selective crystallization of [FeHS/LS(Me2btp)2](ClO4)2·MeCN·2.75H2O (2HS/LS·MeCN·2.75H2O) as red rods, where half of the iron(II) centres resides in the low spin (LS, S = 0) state and the other half is in the high spin (HS, S = 2) state. The red rods spontaneously convert into yellow crystals once removed from the mother liquor and exposed to air due to solvent rearrangement within the crystal packing; these new crystals can be assigned to [FeHS(Me2btp)2](ClO4)2·solvent (2HS·solvent) where all the iron(II) centres are now blocked in the HS state, as confirmed by magnetic measurements. The polarity of the crystallization solvent, together with the maintenance of the crystals within the mother liquor, are pivotal for the reactivity and interconversion of different species. Indeed, upon long standing in solution, 2HS/LS·MeCN·2.75H2O converts to another form of red crystals belonging to [FeLS(Me2btp)2][FeHS(Me2btp)(MeCN)2(H2O)](ClO4)4·MeCN (2LS·3HS·MeCN), as confirmed by single crystal X-ray diffraction data. In this co-crystal, the iron(II) in 2 resides in the LS state at all temperatures while the iron(II) in 3 is blocked in the HS state. Well-formed yellow crystals could be also isolated among the red crystals of 2HS/LS·MeCN·2.75H2O, and they could be identified as the unprecedented octacoordinated species [Fe(Me2btp)2(MeCN)(H2O)](ClO4)2·H2O (1·H2O) by single-crystal X-ray diffraction. These yellow crystals are stable in the air, but slowly convert into 2LS·3HS·MeCN if kept in the mother liquor for about one week. 1·H2O can be considered the trapped intermediate in the solid state during the conversion of [FeHS(Me2btp)2]2+ into [FeHS(Me2btp)(MeCN)2(H2O)]2+ in solution, where the two tridentate ligands in the starting species can unfold to accommodate coordinated MeCN and H2O molecules, as confirmed by theoretical calculations, and eventually one of the two Me2btp is completely replaced by the solvent.

A proficient multivariate approach for iron(II) spin crossover behaviour modelling in the solid state.

Iron(II) bis-pyrazolilpyridyl (bpp-R) complexes [Fe(bpp-R)2](X)2·solvent, R = substituent and X- = anion, can undergo a spin transition from high (S = 2, HS) to low spin (S = 0, LS), being spin crossover (SCO) in the solid state. The distortion of the octahedral coordination environment around the metal centre is governed by crystal packing, i.e. the intermolecular interactions among the substituent R of the bpp-R ligands, the anion X-, and the co-crystallized solvent, and this modulates the SCO behaviour. In this work, an innovative multivariate approach, through the combination of the chemometric tools Principal Component Analysis and Partial Least Squares regression, was applied on the coordination bond distances and angles and selected torsional angles of the available HS structures. The obtained results can efficiently model and rationalize the structural data distinguishing between SCO-active and HS-blocked complexes bearing different R groups, X- anions, and co-crystallized solvents and help predict the spin transition temperature T1/2.

River widening in mountain and foothill areas during floods: Insights from a meta-analysis of 51 European Rivers.

River widening, defined as a lateral expansion of the channel, is a critical process that maintains fluvial ecosystems and is part of the regular functioning of rivers. However, in areas with high population density, channel widening can cause damage during floods. Therefore, for effective flood risk management it is essential to identify river reaches where abrupt channel widening may occur. Despite numerous efforts to predict channel widening, most studies have been limited to single rivers and single flood events, which may not be representative of other conditions. Moreover, a multi-catchment scale approach that covers various settings and flood magnitudes has been lacking. In this study, we fill this gap by compiling a large database comprising 1564 river reaches in several mountain regions in Europe affected by floods of varying magnitudes in the last six decades. By applying a meta-analysis, we aimed to identify the types of floods responsible for more extensive widening, the river reach types where intense widening is more likely to occur, and the hydraulic and morphological variables that explain widening and can aid in predicting widening. Our analysis revealed seven groups of reaches with significantly different responses to floods regarding width ratios (i.e., the ratio between channel width after and before a flood). Among these groups, the river reaches located in the Mediterranean region and affected by extreme floods triggered by short and intense precipitation events showed significantly larger widening than other river reaches in other regions. Additionally, the meta-analysis confirmed valley confinement as a critical morphological variable that controls channel widening but showed that it is not the only controlling factor. We proposed new statistical models to identify river reaches prone to widening, estimate potential channel width after a flood, and compute upper bound width ratios. These findings can inform flood hazard evaluations and the design of mitigation measures.

Approach to the patient with decompensated cirrhosis and aortic stenosis during liver transplantation evaluation.

Aortic stenosis (AS) is the most common valvular disease and is reported to be present in 2%-7% of people over the age of 65. Risk factors for aortic stenosis and NASH overlap; thus, as the population ages, there is an increased likelihood that patients undergoing liver transplantation evaluation may have severe aortic stenosis. There is a high mortality rate associated with cardiac surgeries in patients with cirrhosis. Further, there are no guidelines that assist in the decision making process for patients with cirrhosis and AS. In this review, we highlight key studies that compare transcatheter aortic valve implantation (TAVI) with surgical aortic valve replacement (SAVR) in patients with cirrhosis. We propose an algorithm as to how to approach the patient with aortic stenosis and considerations unique to patients with cirrhosis (i.e., anticoagulation, EGD for variceal assessment; need to determine timing after TAVI before listing).

Lung Ultrasound in Thoracic Surgery: Confirming Placement of a Pediatric Right Double-Lumen Tube.

In the recent decades, flexible bronchoscopy has replaced lung auscultation to confirm more precisely the placement of a double-lumen endotracheal tube (DLT) for thoracic surgery. However, bronchoscopes are costly and not always available. Lung ultrasound has been described in the literature as an alternative to confirm left DLT placement and lung isolation. In this case report, we describe a pediatric thoracic case in which lung ultrasound was utilized to confirm correct placement of a right-sided DLT.

Survey of the vaia storm deposits in the tegnas catchment (Dolomites, Italy): Field data and evidence of sediment-water flow types.

Brenna et al. [1] developed a survey protocol to collect evidence aimed at classifying flood deposits on the basis of the flow type that mobilized and deposited sediment. Such a survey protocol was adopted to characterize the flood deposits in a mountain catchment of the Dolomites (the Tegnas Torrent and its tributaries; drainage area of 51 km2) after a high-magnitude hydrological event that occurred in October 2018 (the so-called "Vaia Storm"). In this article, we present the field data collected at thirty-two survey sites considering the geomorphological and sedimentological characteristics of the analysed sedimentary products and their effects on the vegetation. Data on the characteristics of the flood deposits have enabled recognizing the transport mechanisms that occurred during the Vaia Storm along the stream network [1]. Future applications of the survey protocol adopted in this study could compare and integrate the collected data with those presented in detail in this article.

Channel control works and sediment connectivity in the European Alps.

The need for reducing erosion and sediment transport, and protecting human settlements has urged the construction of channel control works in mountain streams. Such works include different structures, the check dams being probably the most widespread and archetypical. The performance of channel control works in mountain streams has usually been evaluated based on their effectiveness in stabilizing the channels and the adjacent hillslopes, and in retaining sediment. The widespread presence of channel control works in mountain streams of various regions, however, has also a significant impact on hillslope-channel coupling and on sediment transfer across the channel system. Taking into account the impact of channel control works on sediment connectivity at the catchment scale has remarkable importance for planning new control structures and managing the existing ones and, more in general, for sediment management in mountain catchments. In this paper, we consider the channel control works within the conceptual framework of sediment connectivity and related terminology, and we analyze the spatial and temporal scales of the interactions between channel control works and sediment coupling-decoupling. Some examples from the Italian Alps outline the impact of check dams and other hydraulic structures on sediment connectivity and show the potential of geomorphometry in assessing such impacts. The overall effect of control works on sediment connectivity consists of an alteration of the sediment cascade with a decrease in the efficiency of sediment transfer. Sediment is partly retained behind grade-control dams within the catchment or in sediment traps equipped with retention check dams near the alluvial fan apex. These works contribute to decouple the alluvial fans from the upslope catchment. On the contrary, channel bed lining on alluvial fans favors sediment transfer to the receiving river, but this effect usually involves small amounts of sediment not retained by the check dams built upstream.

Systems and Sensors for Debris-flow Monitoring and Warning.

Debris flows are a type of mass movement that occurs in mountain torrents. They consist of a high concentration of solid material in water that flows as a wave with a steep front. Debris flows can be considered a phenomenon intermediate between landslides and water floods. They are amongst the most hazardous natural processes in mountainous regions and may occur under different climatic conditions. Their destructiveness is due to different factors: their capability of transporting and depositing huge amounts of solid materials, which may also reach large sizes (boulders of several cubic meters are commonly transported by debris flows), their steep fronts, which may reach several meters of height and also their high velocities. The implementation of both structural and nonstructural control measures is often required when debris flows endanger routes, urban areas and other infrastructures. Sensor networks for debris-flow monitoring and warning play an important role amongst non-structural measures intended to reduce debris-flow risk. In particular, debris flow warning systems can be subdivided into two main classes: advance warning and event warning systems. These two classes employ different types of sensors. Advance warning systems are based on monitoring causative hydrometeorological processes (typically rainfall) and aim to issue a warning before a possible debris flow is triggered. Event warning systems are based on detecting debris flows when these processes are in progress. They have a much smaller lead time than advance warning ones but are also less prone to false alarms. Advance warning for debris flows employs sensors and techniques typical of meteorology and hydrology, including measuring rainfall by means of rain gauges and weather radar and monitoring water discharge in headwater streams. Event warning systems use different types of sensors, encompassing ultrasonic or radar gauges, ground vibration sensors, videocameras, avalanche pendulums, photocells, trip wires etc. Event warning systems for debris flows have a strong linkage with debris-flow monitoring that is carried out for research purposes: the same sensors are often used for both monitoring and warning, although warning systems have higher requirements of robustness than monitoring systems. The paper presents a description of the sensors employed for debris-flow monitoring and event warning systems, with attention given to advantages and drawbacks of different types of sensors.

Intraoperative Transesophageal Echocardiogram During Orthotopic Liver Transplantation: TEE to the Rescue!

Supported by a growing number of studies and case reports in the literature, perioperative use of TEE in non-cardiac cases has significantly increased the past two decades. The utility of TEE in monitoring hemodynamic, and diagnosing causes of hypotension refractory to conventional therapy, have made it an almost indispensible tool during major surgeries, such liver transplantation. Despite this fact, compared to the adult population, there is a lack of an equivalent amount of literature on the perioperative use of TEE in pediatric cases. In our case we report the utilization of TEE during a pediatric liver transplant, to diagnose a post reperfusion suprahepatic anastomosis stricture. In this case, the cooperation of the anesthesia, the surgical, and the cardiology teams, helped in resolving the case, allowing a positive outcome for the patient. To our knowledge, this is the first case describing the use of TEE during a pediatric liver transplant.

POCUS in perioperative medicine: a North American perspective.

Ultrasound (US) performed at the point of care has found fertile ground in perioperative medicine. In the hands of anesthesiologists, transesophageal echocardiography (TEE) has become established as a powerful diagnostic and monitoring tool in the perioperative care of cardiac and non-cardiac patients. A number of point-of-care US (POCUS) applications are relevant to perioperative care, including airway, cardiac, lung and gastric US. Although guidelines exist to define the scope of practice for basic and advanced TEE, there remains a lack of such guidelines for perioperative point-of-care ultrasound (POCUS), despite a number of recent calls for action in the academic anesthesia community. POCUS training has been integrated into anesthesia residency curricula in Canada and the United States of America (USA). However, a nation-wide curriculum is still lacking. Many limitations to the development of perioperative POCUS curricula exist, including the need to define the scope of practice and design integrated longitudinal learning approaches. The main anesthesiologist societies in both the USA and Canada are promoting the development of guidelines and have introduced POCUS courses into their national conferences. Although bedside US imaging has been integrated into the curricula of many medical schools in North America, the need for specific national guidelines for the training and practice of POCUS in the perioperative setting by anesthesiologists is crucial to the further development of POCUS in perioperative medicine.

Foreign body entrapment during thoracic surgery-time for closed loop communication.

OBJECTIVES: During general thoracic surgery procedures, devices are often placed in the airway and oesophagus. This creates an opportunity for foreign body entrapment (FBE) during pulmonary and foregut surgery. Like retained foreign bodies (RFB), FBE is an entirely preventable event. Unlike RFB, there is minimal literature on FBE, thus little is known about its occurrence, risk factors, and prevention. METHODS: A survey was distributed to 215 surgeons of the General Thoracic Surgical Club. The survey included questions about socio-demographics, procedural volume, occurrence of FBE and factors leading to FBE. RESULTS: There were 110 responses (51%, 110/215). The majority of respondents worked in academic hospitals (75%, 82/110), in urban environments (63%, 69/110), and were male (85%, 94/110). One hundred and four respondents performed pulmonary resections and 92 performed foregut surgeries. In the pulmonary group, 40% (42/104) reported FBE with 67% (23/42) in open procedures. In the foregut group 38% (35/92) reported FBE with 69% (24/35) in open procedures. With both groups combined, 54.5% (60/110) of respondents reported FBE at least once and 29% (24/110) reported more than one FBE in their career. The most frequently reported contributing factor was communication errors between the surgical and anaesthesia teams. CONCLUSIONS: FBE during general thoracic procedures occurs in both minimally invasive and open pulmonary and foregut procedures. The greatest risk factor is communication error. Specific routine closed loop communication with the anaesthesia team prior to stapling/suturing the airway or oesophagus would minimize the risk of FBE.