Tracheal Infection Resulting from High Endotracheal Tube Cuff Pressure in an Unconscious Patient with Brain Trauma.

Deep neck infections (DNIs) are mainly caused by dental caries, tonsillitis, and pharyngitis; however, DNIs can also occur after head and neck trauma. A 79-year-old male patient underwent a craniectomy due to an acute subdural hematoma. The patient was unconscious and continued to have a fever, but no clear cause was found. On postoperative day 9, he suddenly showed redness and swelling on the anterior neck. Enhanced computed tomography of the pharynx revealed tracheal necrosis and an abscess in the surrounding area. An incision and drainage were performed and Enterobacter aerogenes and E. faecalis were identified. The infection was controlled after antibiotic treatment. High endotracheal tube cuff pressure was suspected as the cause of the tracheal infection. Although DNIs are difficult to predict in patients who cannot report their symptoms due to unconsciousness, prevention and rapid diagnosis are important, as DNIs have serious side effects.

Biomechanical Comparison of Four Different Atlantoaxial Posterior Fixation Constructs in Adults: A Finite Element Study.

STUDY DESIGN: Finite element analysis. OBJECTIVE: To compare the biomechanical stability imparted to the C1 and C2 vertebrae by the transarticular (TA), C1 lateral mass (LM)-C2 pedicle (PS), C1LM-C2 pars, and C1LM-C2 translaminar (TL) screw fixation techniques. SUMMARY OF BACKGROUND DATA: Cadaveric biomechanical studies of several atlantoaxial posterior fixation techniques have been performed, showing significant heterogeneity in biomechanical properties among the studies. METHODS: From computed tomography images, a nonlinear intact three-dimensional C1-2 finite element model was developed and validated. Four finite element models were reconstructed from different C1-2 fixation techniques. The range of motion (ROM) and maximum von Misses stresses for the four screw techniques were compared under flexion, extension, lateral bending, and axial rotation. RESULTS: C1LM-C2PS showed the greatest decrease in ROM with flexion/extension and lateral bending. C1-2TA and C1LM-C2 pars showed less ROM reduction than the other techniques, in flexion/extension. C1LM-C2TL showed the least decrease in ROM during axial rotation. For C1-2TA, the maximum stress was in the C1-2 joint region. In the C1LM-C2PS, the C1 rod head, C2 pars screw, and C2TL screw were stressed at the C2 rod head. The maximal von Mises stress on the C1-2TA at the C1-2 joint site was the highest at flexion/extension, whereas the C1LM-C2PS had the lowest stress on the screw at flexion/extension and lateral bending. The C1LM-C2TL showed the highest stress in axial rotation and lateral bending. CONCLUSION: In this study, C1LM-C2PS fixation was the most stable technique. If surgeons have to use other fixation methods besides the C2 pedicle screw, they need to be aware that additional fixation or postoperative immobilization may be required to achieve ROM restriction. Careful observation at the maximum stress site on the screw including screw loosening, screw-bone interface disruption or screw fracture will be necessary during follow-up imaging examinations (x-ray and computed tomography scan) after atlantoaxial fixation. LEVEL OF EVIDENCE: N/A.

Feasibility of a Modified E-PASS and POSSUM System for Postoperative Risk Assessment in Patients with Spinal Disease.

OBJECTIVE: This retrospective case control study aimed to evaluate the feasibility of using Estimation of Physiological Ability and Surgical Stress (E-PASS) and Physiological and Operative Severity Score for the enumeration of Mortality and Morbidity (POSSUM) systems in patients undergoing spinal surgical procedures. Degenerative spine disease has increased in incidence in aging societies, as has the number of older adult patients undergoing spinal surgery. Many older adults are at a high surgical risk because of comorbidity and poor general health. METHODS: We retrospectively reviewed 217 patients who had undergone spinal surgery at a single tertiary care. We investigated complications within 1 month after surgery. Criteria for both skin incision in E-PASS and operation magnitude in the POSSUM system were modified to fit spine surgery. We calculated the E-PASS and POSSUM scores for enrolled patients, and investigated the relationship between postoperative complications and both surgical risk scoring systems. To reinforce the predictive ability of the E-PASS system, we adjusted equations and developed modified E-PASS systems. RESULTS: The overall complication rate for spinal surgery was 22.6%. Forty-nine patients experienced 58 postoperative complications. Nineteen major complications, including hematoma, deep infection, pleural effusion, progression of weakness, pulmonary edema, esophageal injury, myocardial infarction, pneumonia, reoperation, renal failure, sepsis, and death, occurred in 17 patients. The area under the receiver operating characteristic curve (AUC) for predicted postoperative complications after spine surgery was 0.588 for E-PASS and 0.721 for POSSUM. For predicted major postoperative complications, the AUC increased to 0.619 for E-PASS and 0.842 for POSSUM. The AUC of the E-PASS system increased from 0.588 to 0.694 with the Modified E-PASS equation. CONCLUSIONS: The POSSUM system may be more useful than the E-PASS system for estimating postoperative surgical risk in patients undergoing spine surgery. The preoperative risk scores of E-PASS and POSSUM can be useful for predicting postoperative major complications. To enhance the predictability of the scoring systems, using of modified equations based on spine surgery-specific factors may help ensure surgical outcomes and patient safety.

Nanocrystalline Ferrihydrite-Based Catalysts for Fischer-Tropsch Synthesis: Part I. Reduction and Carburization Behavior.

Temperature-programmed reduction using H2 (H2-TPR) and CO (CO-TPR) was carried out to investigate the reduction and carburization behavior of nanocrystalline ferrihydrite-based Fe/Cu/K/SiO2 catalysts for use in Fischer-Tropsch synthesis (FTS). Unlike pure ferrihydrite, the ferrihydrite-based catalysts did not pass through the intermediate decomposition step of ferrihydrite (Fe9O2(OH)23) into hematite (a-Fe2O3) as they were reduced into magnetite (Fe3O4). This is attributed to the enhanced thermal stability induced by SiO2. For the ferrihydrite-based catalysts, the reduction of ferrihydrite into magnetite occurred in two stages because the reduction promoter, Cu, is not homogeneously distributed on the catalyst surfaces. The Cu-rich sites are likely to be reduced in the first stage, and the Cu-lean sites may be reduced in the second stage. After the ferrihydrite is reduced to magnetite, the reduction process of magnetite was similar to that for conventional hematite-based FTS catalysts: 'magnetite --> metallic iron' and 'magnetite --> wüstite (FeO) or fayalite (Fe2SiO4) --> metallic iron' in the H2 atmosphere; 'magnetite --> iron carbides' in the CO atmosphere.

Nanocrystalline Ferrihydrite-Based Catalysts for Fischer-Tropsch Synthesis: Part II. Effects of Activation Gases on the Catalytic Performance.

Fischer-Tropsch synthesis (FTS) was carried out over nanocrystalline ferrihydrite-based (Fe9O2(OH)23) catalysts activated by different reducing agents: syngas (H2+CO), CO, and H2. The syngas activation successfully changed the ferrihydrite-based catalysts into an active and stable catalytic structure with chi-carbide (Fe2.5 C) and epsilon'-carbide (Fe2.2 C). The crystal structure of the catalysts obtained by syngas activation was similar to the structure obtained by CO activation; this similarity was probably due to the peculiar reduction behavior of the ferrihydrite-based catalysts, which exhibit much greater reducibility in CO atmosphere than in H2 atmosphere. The performance of the catalysts activated by syngas was much higher than the performance of the catalysts activated by H2 and was comparable to the performance of the catalysts activated by CO. This strongly demonstrates that the ferrihydrite-based catalysts are advantageous for industrial FTS processes because syngas can be commonly used for both activation pre-treatment and subsequent reaction.

Nanocrystalline Iron-Ore-Based Catalysts for Fischer-Tropsch Synthesis.

Nanocrystalline iron ore particles were fabricated by a wet-milling process using an Ultra Apex Mill, after which they were used as raw materials of iron-based catalysts for low-temperature Fischer-Tropsch synthesis (FTS) below 280 degrees C, which usually requires catalysts with a high surface area, a large pore volume, and a small crystallite size. The wet-milling process using the Ultra Apex Mill effectively destroyed the initial crystallite structure of the natural iron ores of several tens to hundreds of nanometers in size, resulting in the generation of nanocrystalline iron ore particles with a high surface area and a large pore volume. The iron-ore-based catalysts prepared from the nanocrystalline iron ore particles effectively catalyzed the low-temperature FTS, displaying a high CO conversion (about 90%) and good C5+ hydrocarbon productivity (about 0.22 g/g(cat)(-h)). This demonstrates the feasibility of using the iron-ore-based catalysts as inexpensive and disposable catalysts for the low-temperature FTS.

Embolization with Gamma Knife Radiosurgery of Giant Intracranial Arteriovenous Malformations.

AIM: Giant arteriovenous malformations (i.e., those greater than 6 cm maximum diameter or volume > 33 cc) are difficult to treat and often carry higher treatment morbidity and mortality rates. In our study, we reviewed the angiographic results and clinical outcomes for 11 patients with giant arteriovenous malformations who were treated between 1994 and 2012. MATERIAL AND METHODS: The patients selected included 9 males (82%) and 2 females (18%). Their presenting symptoms were hemorrhage (n=2; 18%), seizure (n=7; 64%), and headache (n=2; 12%). Nine patients were Spetzler-Martin Grade III, 2 were Spetzler-Martin Grade IV. The mean arteriovenous malformation volume was 41 cc (33-52 cc). The mean age of the patients was 45.1 years (24-57 years) and the mean radiation dose delivered to the margin of the nidus was 14.2 Gy. RESULTS: Ten patients received pre-Gamma Knife radiosurgery embolization and Gamma Knife radiosurgery, 1 patient received pre-Gamma Knife radiosurgery embolization and Gamma Knife radiosurgery twice and the interval between Gamma Knife radiosurgeries was 3 months. The complete obliteration rate following Gamma Knife radiosurgery was 36%, subtotal obliteration ( > 70% decreased size of nidus) was 36%, and partial obliteration was 28%. One patient experienced a small hemorrhage after embolization. CONCLUSION: Combined embolization and Gamma Knife radiosurgery showed successful obliteration of the arteriovenous malformation nidus. The use of embolization to initially reduce nidus size followed by Gamma Knife radiosurgery improves the treatment results. Repeated Gamma Knife radiosurgery should be a treatment option when there is a small nidus remnant.

High-Resolution Magnetic Resonance Imaging of Intracranial Vertebral Artery Dissecting Aneurysm for Planning of Endovascular Treatment.

The equipment and techniques associated with magnetic resonance imaging (MRI) have rapidly evolved. The development of 3.0 Tesla MRI has enabled high-resolution imaging of the intracranial vessel wall. High-resolution MRI (HRMRI) can yield excellent visualization of both the arterial wall and lumen, thus facilitating the detection of the primary and secondary features of intracranial arterial dissection. In the present report, we describe the manner in which HRMRI affected our endovascular treatment planning strategy in 2 cases with unruptured intracranial vertebral artery dissection aneurysm. HRMRI provides further information about the vessel wall and the lumen of the unruptured intracranial vertebral artery dissecting aneurysm, which was treated by an endovascular approach in the 2 current cases.

A new synthesis of carbon encapsulated Fe5C2 nanoparticles for high-temperature Fischer-Tropsch synthesis.

Using a simple thermal treatment under a CO flow, uniform micrometer-sized iron oxalate dihydrate cubes prepared by hydrothermal reaction were transformed into Fe5C2@C nanoparticles to form a mesoporous framework; the final structure was successfully applied to the high-temperature Fischer-Tropsch reaction and it showed high activity (CO conversion = 96%, FTY = 1.5 × 10(-4) molCO gFe(-1) s(-1)) and stability.