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Systematic review and meta-analysis, level III.

BACKGROUND Resuscitative endovascular balloon occlusion of the aorta (REBOA) is an emerging option for hemorrhage control, but its use is limited in scenarios such as penetrating chest trauma. The aim of this study was to describe the use of REBOA as a resuscitative adjunct in these cases with major hemorrhage and to propose a new clinical management algorithm. METHODS This was a prospective, observational study conducted at a single Level I trauma center in Colombia. We included all patients older than 14 years with severe trauma who underwent REBOA from January 2015 to December 2019. Patients received REBOA if they were in hemorrhagic shock and were unresponsive to resuscitation. RESULTS A total of 56 patients underwent REBOA placement of which 37 had penetrating trauma and 23 had chest trauma. All patients were hemodynamically unstable upon arrival to the emergency department, with a median systolic blood pressure of 69 mm Hg (interquartile range [IQR], 57–90 mm Hg) and median Injury Severity Score was 25 (IQR, 25–41). All REBOAs were deployed and inflated in zone 1, median inflation time was 40 minutes (IQR, 26–55 minutes), and no adverse neurologic outcomes were observed. Fifteen patients had REBOA and a median sternotomy. Eleven patients had concomitant abdominal wounds. Overall mortality was 28.6%, and there was no significant difference between penetrating versus blunt trauma patients (21.6% vs. 42.1%, p = 0.11). The survival rate of thoracic injured patients was similar to the predicted survival (65.2% vs. 63.3%). CONCLUSION Resuscitative endovascular balloon occlusion of the aorta can be used safely in penetrating chest trauma, and the implementation of a REBOA management algorithm is feasible with a well-trained multidisciplinary team. LEVEL OF EVIDENCE Therapeutic, level V.

The roles of indenter material and size in the failure of brittle veneer layers in all-ceramic crown-like structures are studied. Glass veneer layers 1 mm thick bonded to alumina layers 0.5 mm thick on polycarbonate bases (representative of porcelain/ceramic-core/dentin) are subject to cyclic contact loading with spherical indenters in water (representative of occlusal biting environment). Two indenter materials-glass and tungsten carbide-and three indenter radii-1.6, 5.0, and 12.5 mm-are investigated in the tests. A video camera is used to follow the near-contact initiation and subsequent downward propagation of cone cracks through the veneer layer to the core interface, at which point the specimen is considered to have failed. Both indenter material and indenter radius have some effect on the critical loads to initiate cracks within the local Hertzian contact field, but the influence of modulus is weaker. The critical loads to take the veneer to failure are relatively insensitive to either of these indenter variables, since the bulk of the cone crack propagation takes place in the contact far field. Clinical implications of the results are considered, including the issue of single-cycle overload versus low-load cyclic fatigue and changes in fracture mode with loading conditions.

The thermoelectric properties of SnSe are studied by first-principles methods using an original methodology. We computed first the electronic structure of the system, which justifies its macroscopic anisotropy; the inclusion of van der Waals dispersive corrections improves the agreement of the structural parameters with experiments. The Seebeck coefficient and the electrical and thermal conductivities of single crystals and polycrystals are subsequently described in good agreement with experimental data. As for the electrical conductivity, values calculated with a temperature-dependent relaxation time compare well with the available measurements, especially for single crystals; in contrast, a constant relaxation time suffices to describe the results for polycrystals. Based on the iterative solution of the Boltzmann transport equation for phonons, we discuss the behavior of the thermal conductivity of the system in terms of its phonon spectrum. Finally, the figure of merit of SnSe single crystals and polycrystals is calculated and correlated with the previous discussions about electrical and thermal conductivities. From these findings, possible strategies to increase the figure of merit in practice are suggested.

BACKGROUND This study aimed to determine the critical threshold of systolic blood pressure (SBP) for aortic occlusion (AO) in severely injured patients with profound hemorrhagic shock. METHODS All adult patients (>15 years) undergoing AO via resuscitative endovascular balloon occlusion of the aorta (REBOA) or thoracotomy with aortic cross clamping (TACC) between 2014 and 2018 at level I trauma center were included. Patients who required cardiopulmonary resuscitation in the prehospital setting were excluded. A logistic regression analysis based on mechanism of injury, age, Injury Severity Score, REBOA/TACC, and SBP on admission was done. RESULTS A total of 107 patients underwent AO. In 57, TACC was performed, and in 50, REBOA was performed. Sixty patients who underwent AO developed traumatic cardiac arrest (TCA), and 47 did not (no TCA). Penetrating trauma was more prevalent in the TCA group (TCA, 90% vs. no TCA, 74%; p < 0.05) but did not modify 24-hour mortality (odds ratio, 0.51; 95% confidence interval, 0.13–2.00; p = 0.337). Overall, 24-hour mortality was 47% (50) and 52% (56) for 28-day mortality. When the SBP reached 60 mm Hg, the predicted mortality at 24 hours was more than 50% and a SBP lower than 70 mm Hg was also associated with an increased of probability of cardiac arrest. CONCLUSION Systolic blood pressure of 60 mm Hg appears to be the optimal value upon which AO must be performed immediately to prevent the probability of death (>50%). However, values of SBP less than 70 mm Hg also increase the probability of cardiac arrest. LEVEL OF EVIDENCE Therapeutic study, level IV.

A study is made of the competition between failure modes in ceramic-based bilayer structures joined to polymer-based substrates, in simulation of dental crown-like structures with a functional but weak "veneer" layer bonded onto a strong "core" layer. Cyclic contact fatigue tests are conducted in water on model flat systems consisting of glass plates joined to glass, sapphire, alumina or zirconia support layers glued onto polycarbonate bases. Critical numbers of cycles to take each crack mode to failure are plotted as a function of peak contact load on failure maps showing regions in which each fracture mode dominates. In low-cycle conditions, radial and outer cone cracks are competitive in specimens with alumina cores, and outer cone cracks prevail in specimens with zirconia cores; in high-cycle conditions, inner cone cracks prevail in all cases. The roles of other factors, e.g. substrate modulus, layer thickness, indenter radius and residual stresses from specimen preparation, are briefly considered.

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