Challenges of Providing Optimal and Safe Intrapartum Analgesia in Patients With HELLP Syndrome: A Case Report and Literature Review.

HELLP (Hemolysis, Elevated Liver enzymes, Low Platelets) Syndrome is a rare but serious complication of pregnancy that can lead to disseminated intravascular coagulation, pulmonary edema, respiratory failure, hepatic and renal injury, and death if not recognized and treated promptly. A 36-year-old nulligravid (G0) active duty Marine at 36 weeks and 1 day gestation with dichorionic diamniotic twins presented to triage for routine cervical examination found to have elevated blood pressures and symptomatic thrombocytopenia, with a suspected diagnosis of HELLP. A multidisciplinary decision was made by anesthesiology, obstetrics and gynecology, and pediatrics to deliver the twins to avoid any further complications. The twins were in cephalic presentation and the patient desired to attempt a vaginal delivery. Due to the patient's thrombocytopenia, neuraxial anesthesia (spinal and/or epidural) left the patient at a high risk of developing catastrophic complications such as an epidural hematoma, and the subsequent motor block/weakness would likely lessen the patient's ability to participate in active labor for a vaginal delivery. A Cesarean section under general anesthesia was also to be avoided as the patient's elevated risk of catastrophic hemorrhage would be worsened by volatile anesthetic agents which cause significant uterine vascular relaxation and reduced uterine muscular tone. Ultimately, the decision was made to provide analgesia through a remifentanil PCA (patient-controlled analgesia) for labor and a ketamine bolus for delivery. The mother delivered both twins vaginally in the operating room without perioperative complication. This case demonstrates the safety of alternate forms of anesthesia for delivery when neuraxial anesthesia is contraindicated.

Bronchoalveolar Lavage and Oleic Acid Two-hit Model for Inducing Acute Respiratory Distress Syndrome in Swine Models.

INTRODUCTION: Acute respiratory distress syndrome (ARDS) is a widespread and often fatal clinical syndrome marked by the acute onset of pulmonary edema and inflammatory-mediated disruptions in alveolar-capillary permeability resulting in impaired gas exchange and tissue oxygenation with subsequent acute respiratory failure that accounts for 10.4% of all intensive care unit admissions worldwide and boasts a mortality rate of 38.5%. The current treatment for ARDS remains largely supportive. This is largely because of the many challenges of achieving a stable and sustainable animal model that recreates the pathophysiology of ARDS experimentally in a controlled setting to allow research to elucidate potential treatments of ARDS moving forward. MATERIALS AND METHODS: The bronchoalveolar lavage and oleic acid models are currently the 2 most frequently used experimental models in inducing ARDS in animal models. This study demonstrated that combining them into a "two-hit model" can produce sustained ARDS in swine models per the Horowitz index (PaO2/FiO2 ratio of ≤300 mmHg). Additionally, expected changes in pH, pCO2, lung compliance, cytokines, and tissue histopathology were observed and add to our confidence and reliability that the "two-hit model" produces symptomatic ARDS in a manner very similar to that observed in humans. RESULTS AND CONCLUSIONS: In conclusion, we demonstrated a viable animal model of human ARDS that is maintained for a prolonged period, suitable for continuous monitoring of the progression, and evaluation of potential future treatments and procedures to reduce patient morbidity and mortality. To carry out this two-hit model, lung injury was induced through a combination of bronchoalveolar lavage and oleic acid administration and the disease process of ARDS is subsequently tracked through clinically relevant parameters such as respiratory mechanics, cytokine response, aretrial blood gas (ABG) changes, and observation of postmortem histopathologic changes. This promising new model has the capacity to successfully replicate human ARDS which is a well-known and notoriously multifactorial pathogenic process to reproduce experimentally for an extended period of time. The "two-hit model" is a viable and appropriate model for the research of novel treatments for ARDS.

Total Knee Arthroplasty Revision in the Setting of Periprosthetic Joint Infection Resulting in Bone Cement Implantation Syndrome (BCIS), Pulseless Electrical Activity (PEA) Arrest, and Intraoperative Death: A Case Report and Literature Review.

An 87-year-old female with a history of total knee arthroplasty (TKA) presented to the emergency department (ED) for left knee pain in the setting of recent methicillin-sensitive Staphylococcus aureus (MSSA) sepsis of unknown origin. She was subsequently diagnosed with a complicated symptomatic periprosthetic joint infection of her left TKA hardware and was admitted for TKA revision following an orthopedic surgery consultation. Upon arrival at the operating room (OR), standard American Society of Anesthesiology (ASA) monitors were applied. These included non-invasive blood pressure, electrocardiogram (ECG), pulse oximeter, and an esophageal temperature probe. The patient then underwent induction of general endotracheal anesthesia (GETA) without significant hemodynamic compromise. Intraoperatively, the patient tolerated the removal of her infected hardware without major complication but upon placement of the methyl methacrylate (MMA), commonly referred to as bone cement, the patient had an acute drop in her end-tidal carbon dioxide (EtCO2) and then developed significant bradycardia and hypotension. Despite rapid detection and treatment, the patient continued to collapse hemodynamically and was noted to be pulseless and in pulseless electrical activity (PEA) arrest on ECG. Cardiopulmonary resuscitation (CPR) was immediately started per the Advanced Cardiac Life Support (ACLS) algorithm. Roughly after 45 minutes of continuous CPR and multiple doses of 1 mg epinephrine, it was determined that the patient had suffered a catastrophic and fatal intraoperative event. A team decision was made to stop providing any lifesaving interventions. This patient's presentation is consistent with bone cement implantation syndrome (BCIS), an uncommon phenomenon that remains poorly understood. Two leading models for BCIS described in the literature are the monomer-mediated and embolus-mediated models. However, further research into BCIS is warranted to better understand its pathophysiology, incidence, as well as potential prophylactic measures, including the use of cementless arthroplasty. This complicated and fatal case serves as a reminder of the morbidity and mortality associated with BCIS and underscores that anesthesiology teams must remain vigilant and prepared during orthopedic joint procedures.

Honeycomb gold specimen supports enabling orthogonal focussed ion beam-milling of elongated cells for cryo-ET.

Cryo-focussed ion beam (FIB)-milling is a powerful technique that opens up thick, cellular specimens to high-resolution structural analysis by electron cryotomography (cryo-ET). FIB-milled lamellae can be produced from cells on grids, or cut from thicker, high-pressure frozen specimens. However, these approaches can put geometrical constraints on the specimen that may be unhelpful, particularly when imaging structures within the cell that have a very defined orientation. For example, plunge frozen rod-shaped bacteria orient parallel to the plane of the grid, yet the Z-ring, a filamentous structure of the tubulin-like protein FtsZ and the key organiser of bacterial division, runs around the circumference of the cell such that it is perpendicular to the imaging plane. It is therefore difficult or impractical to image many complete rings with current technologies. To circumvent this problem, we have fabricated monolithic gold specimen supports with a regular array of cylindrical wells in a honeycomb geometry, which trap bacteria in a vertical orientation. These supports, which we call "honeycomb gold discs", replace standard EM grids and when combined with FIB-milling enable the production of lamellae containing cross-sections through cells. The resulting lamellae are more stable and resistant to breakage and charging than conventional lamellae. The design of the honeycomb discs can be modified according to need and so will also enable cryo-ET and cryo-EM imaging of other specimens in otherwise difficult to obtain orientations.

Intraoperative Acute Cardiac Tamponade as a Result of Intracardiac Perforation Requiring Emergency Continuous Pericardiocentesis and Open Sternotomy: A Case Report and Literature Review of a Rare but Fatal Complication.

Intraoperative acute cardiac tamponade associated with iatrogenic intracardiac perforation from percutaneous interventional cardiac procedures is a rare but potentially catastrophic complication. We report a case of intraoperative acute hemopericardium caused by a left atrial (LA) perforation resulting in cardiac tamponade in a patient undergoing a baffling procedure for the correction of two anomalous pulmonary veins draining into her superior vena cava (SVC) that required continuous pericardiocentesis with autologous blood transfusion via the femoral vein and an emergency intraoperative transfer from the interventional cardiology cath lab to the cardiac operating room for an open sternotomy and primary repair. An 86-year-old female with known right-ventricular (RV) failure with preserved ejection fraction (left ventricular ejection fraction (LVEF): 50-55% on transesophageal echocardiography (TEE) one week prior) and atrial fibrillation was admitted for her third heat failure exacerbation in two months despite being adherent to her aggressive diuresis medication regimen. Upon her readmission and due to her symptomatic and seemingly refractory heart failure, the patient underwent a cardiac computer tomography (CT) with 3D reconstruction that showed previously undiagnosed partial anomalous pulmonary venous return (PAPVR) of two of her four pulmonary veins aberrantly draining into the SVC. This anatomic pathology was deemed to be the likely etiology of her repeated episodes of recurring heart failure exacerbations, shortness of breath, peripheral edema, and fatigue. The patient was counseled and consented to a percutaneous baffle of the two anomalous veins to redirect more of the returning pulmonary venous blood away from the SVC and to the LA. While under general endotracheal anesthesia (GETA) with a TEE in place during the procedure, the patient suddenly developed acute hypotension, tachycardia, and a reduction in expired carbon dioxide (EtCO2) was noted quickly followed by evidence of a rapidly accumulating hemopericardium on TEE. Cardiothoracic surgery was urgently consulted to the interventional cardiology cath lab while the patient underwent an emergency pericardiocentesis that momentarily alleviated her hemodynamic instability, cardiac tamponade physiology, and deteriorating overall clinical picture. While performing continuous pericardiocentesis with autologous return of the aspirated blood via femoral venous access the patient was urgently transported to the cardiac operating room and prepped for emergency sternotomy for primary repair of the LA. Following primary repair via sternotomy, multiple drains were placed and the thoracic cavity was closed with wires. The patient was immediately transported to the surgical intensive care unit (SICU) intubated, mechanically ventilated, and sedated. During this time, the patient progressively required additional vasoactive and inotropic agents to support her mean arterial pressure (MAP), and following a multidisciplinary discussion with the patient's family regarding her goals of care, the decision was made to withdraw further resuscitation efforts and the patient expired four hours later.

Accurate magnification determination for cryoEM using gold.

Determining the correct magnified pixel size of single-particle cryoEM micrographs is necessary to maximize resolution and enable accurate model building. Here we describe a simple and rapid procedure for determining the absolute magnification in an electron cryomicroscope to a precision of <0.5%. We show how to use the atomic lattice spacings of crystals of thin and readily available test specimens, such as gold, as an absolute reference to determine magnification for both room temperature and cryogenic imaging. We compare this method to other commonly used methods, and show that it provides comparable accuracy in spite of its simplicity. This magnification calibration method provides a definitive reference quantity for data analysis and processing, simplifies the combination of multiple datasets from different microscopes and detectors, and improves the accuracy with which the contrast transfer function of the microscope can be determined. We also provide an open source program, magCalEM, which can be used to accurately estimate the magnified pixel size of a cryoEM dataset ex post facto.

Structure determination by cryoEM at 100 keV.

Electron cryomicroscopy can, in principle, determine the structures of most biological molecules but is currently limited by access, specimen preparation difficulties, and cost. We describe a purpose-built instrument operating at 100 keV-including advances in electron optics, detection, and processing-that makes structure determination fast and simple at a fraction of current costs. The instrument attains its theoretical performance limits, allowing atomic resolution imaging of gold test specimens and biological molecular structure determination in hours. We demonstrate its capabilities by determining the structures of eleven different specimens, ranging in size from 140 kDa to 2 MDa, using a fraction of the data normally required. CryoEM with a microscope designed specifically for high-efficiency, on-the-spot imaging of biological molecules will expand structural biology to a wide range of previously intractable problems.

Scalable and Chromatography-Free Synthesis of Efflux Pump Inhibitor Phenylalanine Arginine ß-Naphthylamide for Its Validation in Wild-Type Bacterial Strains.

Phenylalanine arginine ß-naphthylamine, or PAßN, is a C-terminus capped dipeptide discovered in 1999 as an RND-type efflux pump inhibitor (EPI). Since then, PAßN has become a standard tool compound in EPI research and development. Despite this, PAßN lacks a detailed or efficient synthesis, and standard parameters for its use in wild-type bacterial strains are inconsistent or non-existent. Therefore, a scalable and chromatography-free synthesis of PAßN was developed using streamlined traditional solution-phase peptide coupling chemistry. With this procedure, gram scale quantities of PAßN were synthesized alongside analogues and stereoisomers to build a focused library to evaluate simple structure activity relationships. While most analogues were less active than the broadly utilized L,L-PAßN itself, we identified that its enantiomer, D,D-PAßN, also provided 8- to 16-fold potentiation of the antibiotic levofloxacin at 40 to 50 µg/mL concentrations of EPI in various wild-type Pseudomonas aeruginosa strains. Additionally, D,D-PAßN was shown to be significantly more hydrolytically stable than L,L-PAßN, indicating that it may be a useful, and now readily synthesized, tool compound facilitating future EPI research.

Physiologic Fidelity as a Domain in Assessing Mixed Reality Trauma Simulation.

INTRODUCTION: Mixed reality has been used in trauma and emergency medicine simulation for more than a decade. As mixed reality potential in trauma simulation continues to expand, so too does the need to validate it as a surrogate for real-life emergency scenarios. Validation of these simulations can occur by measuring fidelity, or the degree to which a computing system can reproduce real-world experiences. After performing a literature review, we determined that most fidelity assessments of trauma and emergency simulations focus on how the user subjectively experiences the simulation. Although subjective user assessment is an important component of determining fidelity, we pose an introductory three-part framework that may assess mixed reality trauma simulation more adequately. MATERIALS AND METHODS: A literature review was conducted using Google Scholar, PubMed, and the Uniformed Services University PowerER search database. Relevant articles were assessed to identify how studies measured fidelity in trauma simulation. We then designed the three-part framework to aid researchers in assessing the fidelity of mixed reality trauma simulations. RESULTS: The domains we determined to best assess mixed reality emergency simulation are as follows:1. Continue assessing fidelity via subjective user assessments. This allows the researcher to know how real the simulation looked and felt to the user based on their individual report.2. Determine whether the trauma simulation changes the medical decision-making capacity of the user. If the user's decision-making capacity changes with a stress-inducing trauma simulation versus a non-stress-inducing simulation, then the stress-inducing trauma environment would be approaching greater fidelity.3. Study the domain of our newly proposed concept: physiologic fidelity. We define physiologic fidelity as the degree to which the simulation elicits a measurable, autonomic response independent of observed emotion or perceived affect. Recreating objective autonomic arousal may be the best way to ensure a trauma simulation reaches fidelity. CONCLUSION: We propose a methodology to assess mixed reality trauma simulation fidelity. Once fidelity is more fully known to the researcher and the simulation user, adjustments can be made to approach reality more closely. Improved simulators may enrich the preparedness of both junior and senior learners for real-life emergencies. We believe assessing the three domains using the Wide Area Virtual Experience at the Val G. Hemming simulation center in Bethesda, MD, will validate mixed reality-trauma simulators as invaluable surrogates for real-life emergency scenarios and ultimately contribute to improved clinical outcomes for clinicians and their patients.

Cryomicroscopy in situ: what is the smallest molecule that can be directly identified without labels in a cell?

Electron cryomicroscopy (cryoEM) has made great strides in the last decade, such that the atomic structure of most biological macromolecules can, at least in principle, be determined. Major technological advances - in electron imaging hardware, data analysis software, and cryogenic specimen preparation technology - continue at pace and contribute to the exponential growth in the number of atomic structures determined by cryoEM. It is now conceivable that within the next decade we will have structures for hundreds of thousands of unique protein and nucleic acid molecular complexes. But the answers to many important questions in biology would become obvious if we could identify these structures precisely inside cells with quantifiable error. In the context of an abundance of known structures, it is appropriate to consider the current state of electron cryomicroscopy for frozen specimens prepared directly from cells, and try to answer to the question of the title, both now and in the foreseeable future.

Imaging biological macromolecules in thick specimens: The role of inelastic scattering in cryoEM.

We investigate potential improvements in using electron cryomicroscopy to image thick specimens with high-resolution phase contrast imaging. In particular, using model experiments, electron scattering theory, Monte Carlo and multislice simulations, we determine the potential for improving electron cryomicrographs of proteins within a cell using chromatic aberration (Cc) correction. We show that inelastically scattered electrons lose a quantifiable amount of spatial coherence as they transit the specimen, yet can be used to enhance the signal from thick biological specimens (in the 1000 to 5000 Å range) provided they are imaged close to focus with an achromatic lens. This loss of information quantified here, which we call "specimen induced decoherence", is a fundamental limit on imaging biological molecules in situ. We further show that with foreseeable advances in transmission electron microscope technology, it should be possible to directly locate and uniquely identify sub-100 kDa proteins without the need for labels, in a vitrified specimen taken from a cell.

Phase contrast imaging with inelastically scattered electrons from any layer of a thick specimen.

A controversy exists as to whether the signal in a high resolution phase contrast electron micrograph of a particle in a thick specimen is the same irrespective of the particle's position along the beam axis. Different conceptions of inelastic scattering and its effects on wave interference have led to radically different expectations about the degree of phase contrast vs. depth. Here we examine the information available from bright field phase contrast images of small crystalline particles on the top or bottom of a thick support. The support is an aluminium foil which has strong plasmon resonances that cause a large proportion of the electron beam to lose energy in transit. Phase contrast micrographs of the atomic lattice of two ensembles of platinum particles were measured in an energy loss window corresponding to the first plasmon resonance. The signal measured for particles on top was equal to that for particles on the bottom of the foil to within a 99% confidence interval, and the measurements exclude other models of depth dependent phase contrast in the literature to >5σ. These observations are consistent with quantum theory which considers dynamical effects as independent of event sequence and is distinct from the "top-bottom effect" observed in amplitude contrast. We thus confirm that phase contrast using inelastically scattered electrons can be obtained equally well from particles within any layer of a thick specimen.

On the reduction in the effects of radiation damage to two-dimensional crystals of organic and biological molecules at liquid-helium temperature.

We have studied the fading of electron diffraction spots from two-dimensional (2D) crystals of paraffin (C44H90), purple membrane (bacteriorhodopsin) and aquaporin 4 (AQP4) at stage temperatures between 4K and 100K. We observed that the diffraction spots at resolutions between 3 Å and 20 Å fade more slowly at liquid-helium temperatures compared to liquid-nitrogen temperatures, by a factor of between 1.2 and 1.8, depending on the specimens. If the reduction in the effective rate of radiation damage for 2D crystals at liquid-helium temperature (as measured by spot fading) can be shown to extend to macromolecular assemblies embedded in amorphous ice, this would suggest that valuable improvements to electron cryomicroscopy (cryoEM) of biological specimens could be made by reducing the temperature of the specimens under irradiation below what is obtainable using standard liquid-nitrogen cryostats.

2.4-Å structure of the double-ring Gemmatimonas phototrophica photosystem.

Phototrophic Gemmatimonadetes evolved the ability to use solar energy following horizontal transfer of photosynthesis-related genes from an ancient phototrophic proteobacterium. The electron cryo-microscopy structure of the Gemmatimonas phototrophica photosystem at 2.4 Å reveals a unique, double-ring complex. Two unique membrane-extrinsic polypeptides, RC-S and RC-U, hold the central type 2 reaction center (RC) within an inner 16-subunit light-harvesting 1 (LH1) ring, which is encircled by an outer 24-subunit antenna ring (LHh) that adds light-gathering capacity. Femtosecond kinetics reveal the flow of energy within the RC-dLH complex, from the outer LHh ring to LH1 and then to the RC. This structural and functional study shows that G. phototrophica has independently evolved its own compact, robust, and highly effective architecture for harvesting and trapping solar energy.