Black phosphorus as a bipolar pseudospin semiconductor.

Semiconductor devices rely on the charge and spin of electrons, but there is another electronic degree of freedom called pseudospin in a two-level quantum system1 such as a crystal consisting of two sublattices2. A potential way to exploit the pseudospin of electrons in pseudospintronics3-5 is to find quantum matter with tunable and sizeable pseudospin polarization. Here, we propose a bipolar pseudospin semiconductor, where the electron and hole states have opposite net pseudospin polarization. We experimentally identify such states in anisotropic honeycomb crystal-black phosphorus. By sublattice interference of photoelectrons, we find bipolar pseudospin polarization greater than 95% that is stable at room temperature. This pseudospin polarization is identified as a consequence of Dirac cones merged in the highly anisotropic honeycomb system6,7. The bipolar pseudospin semiconductor, which is a pseudospin analogue of magnetic semiconductors, is not only interesting in itself, but also might be useful for pseudospintronics.

Holstein polaron in a valley-degenerate two-dimensional semiconductor.

Two-dimensional (2D) crystals have emerged as a class of materials with tunable carrier density1. Carrier doping to 2D semiconductors can be used to modulate many-body interactions2 and to explore novel composite particles. The Holstein polaron is a small composite particle of an electron that carries a cloud of self-induced lattice deformation (or phonons)3-5, which has been proposed to play a key role in high-temperature superconductivity6 and carrier mobility in devices7. Here we report the discovery of Holstein polarons in a surface-doped layered semiconductor, MoS2, in which a puzzling 2D superconducting dome with the critical temperature of 12 K was found recently8-11. Using a high-resolution band mapping of charge carriers, we found strong band renormalizations collectively identified as a hitherto unobserved spectral function of Holstein polarons12-18. The short-range nature of electron-phonon (e-ph) coupling in MoS2 can be explained by its valley degeneracy, which enables strong intervalley coupling mediated by acoustic phonons. The coupling strength is found to increase gradually along the superconducting dome up to the intermediate regime, which suggests a bipolaronic pairing in the 2D superconductivity.

Sublattice Interference as the Origin of σ Band Kinks in Graphene.

Kinks near the Fermi level observed in angle-resolved photoemission spectroscopy (ARPES) have been widely accepted to represent electronic coupling to collective excitations, but kinks at higher energies have eluded a unified description. We identify the mechanism leading to such kink features by means of ARPES and tight-binding band calculations on σ bands of graphene, where anomalous kinks at energies as high as ∼4 eV were reported recently [Phys. Rev. Lett. 111, 216806 (2013)]. We found that two σ bands show a strong intensity modulation with abruptly vanishing intensity near the kink features, which is due to sublattice interference. The interference induced local singularity in the matrix element is a critical factor that gives rise to apparent kink features, as confirmed by our spectral simulations without involving any coupling to collective excitations.

Efficacy of bispectral index monitoring during balanced propofol sedation for colonoscopy: a prospective, randomized controlled trial.

BACKGROUND AND AIMS: Appropriate use of propofol is necessary, and objective monitoring of sedation with propofol may be helpful. Studies on the efficacy of bispectral index (BIS) monitoring in deep sedation have been conducted, but its efficacy in colonoscopy with moderate sedation is unknown. In this study, the efficacy of BIS monitoring during colonoscopy with moderate level sedation via balanced propofol sedation was investigated. METHODS: To determine the cut-off value of BIS before the test, an optimal BIS value was determined. Patients who were scheduled to undergo outpatient colonoscopy were prospectively randomized to either a BIS or control group. Finally, a total of 115 patients were selected for this study. The satisfaction level, the complication, and the dosage of the administered propofol were compared. RESULTS: The BIS values and the modified observer's assessment of alertness/sedation scores (MOAA/S) were positively correlated (r=0.66 and p<0.001). The optimal cut-off value of BIS for maintaining moderate sedation was 81, and the area under the ROC curve was 0.88 (95% CI 0.82-0.93), indicating high prediction accuracy. However, there was no difference between the BIS group and the control group in levels of satisfaction of either patients or endoscopists. In addition, there was no difference in the complication and the required dose of propofol between both groups. CONCLUSIONS: BIS and clinical sedation scores, MOAA/S scores, showed a high level of correlation. However, no significant efficacy was observed in the BIS group who underwent outpatient colonoscopy.

Quality Assessment and Relevant Clinical Impact of Randomized Controlled Trials of Varicocele: Next Step to Good-Quality Randomized Controlled Trial of Varicocele Treatment.

PURPOSE: To assess the quality of randomized controlled trials (RCTs) on varicocele published from 1979 to 2017. MATERIALS AND METHODS: We searched for original RCT on varicocele published between 1979 and 2017. Jadad scale, van Tulder scale, and Cochrane Collaboration Risk of Bias Tool were used to analyze RCT quality over time. Effects on RCT quality including funding source, Institutional Review Board (IRB) approval, and intervention were assessed. Treatment parameters of varicocele were also analyzed. RESULTS: Blinding and allocation concealment were described in 25.9% and 9.4% of RCT, respectively. Both tended to increase and a sharp dip in allocation concealment was observed in 2010-2017. Jadad scores increased steadily from 1979 to 2017 (1.28±0.59 to 2.19±1.10, p<0.01). Van Tulder scores tended to increase from 1979 to 2017 (4.21±0.94 to 5.58±1.58, p<0.01). RCTs with funding statements had higher Jadad (Yes vs. No, 3.25±0.50 vs. 1.70±0.97; p<0.01) and van Tulder (Yes vs. No, 7.25±1.26 vs. 4.81±1.26; p<0.01) scores than unfunded RCTs. IRB approval and intervention were associated with better quality. CONCLUSIONS: The number of RCTs on varicocele increased from 1979 to 2017. Also, quality improved over time with increasing IRB approval, funding, and multicenter trial. Most RCTs on varicocele reported the use of surgical treatment. RCTs of surgical treatments have limitations to satisfy the condition of RCT to conduct, but their quality has improved over time.

Anesthetics management of a renal angiomyolipoma using pulse pressure variation and non-invasive cardiac output monitoring: A case report.

BACKGROUND: Hypovolemic shock can lead to life-threatening organ dysfunction, and adequate fluid administration is a fundamental therapy. Traditionally, parameters such as vital signs, central venous pressure, and urine output have been used to estimate intravascular volume. Recently, pulse pressure variation (PPV) and non-invasive cardiac monitoring devices have been introduced. In this case report, we introduce a patient with massive active bleeding from giant renal angiomyolipoma (AML). During emergent nephrectomy, we used non-invasive cardiac monitoring with CSN-1901 (Nihon Kohden, Tokyo, Japan) and PPV to evaluate the patient's intravascular volume status to achieve optimal fluid management. CASE SUMMARY: A 30-year-old male patient with giant AML with active bleeding was referred to the emergency room complaining of severe abdominal pain and spontaneous abdominal distension. AML was diagnosed by computed tomography, and emergent nephrectomy was scheduled. Massive bleeding was expected so we decided to use non-invasive cardiac monitoring and PPV to assist fluid therapy because they are relatively easy and fast compared to invasive cardiac monitoring. During the surgery, 6000 mL of estimated blood loss occurred. Along with the patient's vital signs and laboratory results, we monitored cardiac output, cardiac output, stroke volume, stroke volume index with a non-invasive cardiac monitoring device, and PPV using an intra-arterial catheter to evaluate intravascular volume status of the patient to compensate for massive bleeding. CONCLUSION: In addition to traditional parameters, non-invasive cardiac monitoring and PPV are useful methods to evaluate patient's intravascular volume status and provide guidance for intraoperative management of hypovolemic shock patients.

Unilateral pulmonary hemorrhage caused by negative pressure pulmonary edema: A case report.

BACKGROUND: Unilateral pulmonary hemorrhage is typically reported in young and healthy men with upper respiratory tract obstruction during anesthesia in special situations. Negative pressure in the lungs is created, resulting in negative pressure pulmonary edema (NPPE). CASE SUMMARY: A 78-year-old male patient diagnosed with spinal stenosis was admitted to receive a unilateral laminectomy with bilateral decompression. The patient had been diagnosed with hypertension four years earlier and asthma more than 70 years earlier. We experienced a unilateral alveolar hemorrhage associated with NPPE that occurred in a longstanding asthma patient who bit the intubated endotracheal tube for a short period during posture change at the end of surgery. Because diffuse alveolar hemorrhage accompanied by NPPE was caused in this case by airway obstruction in an older patient with asthma without known risk factors, anesthesiologists should be careful not to induce airway irritation during anesthesia awakening in asthma patients. CONCLUSION: Because diffuse alveolar hemorrhage accompanied by NPPE can occur, anesthesiologists should take care not to induce airway irritation.

Ultrasound-guided greater occipital nerve block with botulinum toxin for patients with chronic headache in the occipital area: a randomized controlled trial.

BACKGROUND: Ultrasound-guided greater occipital nerve (GON) block has been frequently used to treat various types of headaches, and botulinum toxin has recently begun to be used in patients with headache. Our study presents the long-term effect of botulinum toxin on GON block using ultrasound in patients with chronic headache in occipital area. METHODS: Patients with occipital headache were divided into two groups (bupivacaine: BUP group [n = 27], botulinum toxin: BTX group [n = 27]), and ultrasound-guided GON block was performed at the C2 level. GON was detected with ultrasound and distance from GON to midline, from the skin surface to GON, and size of GON were measured in both groups. Visual analogue scale (VAS) scores and Likert scale were assessed at pretreatment and at 1, 4, 8, and 24 weeks after treatment in both groups. RESULTS: The distance from GON to midline was 18.9 ± 4.4 mm (right) and 17.3 ± 3.8 mm (left). The depth from the skin was 12.9 ± 1.5 mm (right) and 13.4 ± 1.6 mm (left). GON size was 3.1 mm on both sides. The VAS score and patient satisfaction score (Likert scale) in 4, 8, and 24 weeks after injection were superior for the BTX than the BUP group. CONCLUSIONS: Ultrasound-guided GON block using BTX is effective in reducing short-term and long-term pain in patients with chronic headache in the occipital area.

Reporting and methodologic evaluation of meta-analyses published in the anesthesia literature according to AMSTAR and PRISMA checklists: a preliminary study.

BACKGROUND: There have been few recent reports on the methodological quality of meta-analysis, despite the enormous number of studies using meta-analytic techniques in the field of anesthesia. The purpose of this study was to evaluate the quality of meta-analyses and systematic reviews according to the Assessment of Multiple Systematic Reviews (AMSTAR) and Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines in the anesthesia literature. METHODS: A search was conducted to identify all meta-analyses ever been published in the British Journal of Anaesthesia (BJA), Anaesthesia, and Korean Journal of Anesthesiology (KJA) between Jan. 01, 2004 and Nov. 31, 2016. We aimed to apply the AMSTAR and PRISMA checklists to all published meta-analyses. RESULTS: We identified 121 meta-analyses in the anesthesia literature from January 2004 through the end of November 2016 (BJA; 75, Anaesthesia; 43, KJA; 3). The number of studies published and percentage of 'Yes' responses for meta-analysis articles published after the year 2010 was significantly increased compared to that of studies published before the year 2009 (P = 0.014 for Anaesthesia). In the anesthesia literature as a whole, participation of statisticians as authors statistically improved average scores of PRISMA items (P = 0.004) especially in the BJA (P = 0.003). CONCLUSIONS: Even though there is little variability in the reporting and methodology of meta-analysis in the anesthesia literature, significant quality improvement in the reporting was observed in the Anaesthesia by applying the PRISMA checklist. Participation of a statistician as an author improved the reporting quality of the meta-analysis.

Does preoperative anxiety felt by patients requested to participate in clinical trials related to general anesthesia before elective surgery depend on temperament?

BACKGROUND: Preoperative anxiety may differ according to patient temperament. It will be increased when patients are requested to participate in a study involving anesthesia. The purpose of this study was to show that the anxiety felt when patients are requested to participate may differ according to temperament in both patients who agree and disagree to participate. METHODS: Three hundred and twenty-one patients over age 18 with American Society of Anesthesiologists 1 and 2 completed a survey questionnaire. The degree of anxiety was measured according to patient temperament. It was compared on the basis of the State-Trait Anxiety Inventory (STAI) and visual analogue scale (VAS). RESULTS: In the agreed group, the degree of anxiety measured by "usual, present STAI" and VAS in the monitors (those who want to know as much as possible about anesthesia and surgery) was significantly higher than that in the blunters (those who want to know as little as possible) (P = 0.041 for the "usual STAI", 0.017 for "present STAI", and 0.001 for VAS, respectively). Among patients with a lower educational level, the numbers of blunters and monitors were 57 (79%) and 32 (59%), respectively, indicating that the ratio of blunters was significantly higher (P = 0.026). CONCLUSIONS: Both traits of patients in each group were influenced by psychological burdens. The anxiety of the monitors who agreed to participate was significantly higher than that of blunters. In addition to temperament, education level affects participation. Obtaining consent for participation by understanding temperament and considering factors that may reduce the participation rate will be required.

The sedative effects of the intranasal administration of dexmedetomidine in children undergoing surgeries compared to other sedation methods: A systematic review and meta-analysis.

STUDY OBJECTIVE: Administration of intranasal dexmedetomidine for sedation is comfortable and effective in children who are afraid of needles, and it offers efficient sedation similar to that of intravenous administration. We performed a systematic review and meta-analysis to evaluate the clinical effects of the pre-procedural administration of intranasal dexmedetomidine. DESIGN: We identified randomized controlled trials (RCTs) that compared intranasal dexmedetomidine administration to other administration methods of various sedatives or placebo from MEDLINE, EMBASE, Cochrane, KoreaMed and hand searches of trial registries. SETTING: Pediatrics who underwent interventional procedures and surgeries. PATIENTS: Children under the age of 18. INTERVENTIONS: Studies were included if they were compatible with the criteria that dexmedetomidine was administered intranasally. MEASUREMENTS: We pooled data on the sedation status as the primary outcome and considered the behavioral score, blood pressure, heart rate and side effects to be secondary outcomes. Risk ratio (RR) and the standardized mean difference (SMD) with 95% confidence intervals (CIs) were calculated for dichotomous and continuous outcomes, respectively. MAIN RESULTS: This meta-analysis included 11 RCTs. The SMD for the sedative effects of intranasal dexmedetomidine was -2.45 (random, 95% CI; -3.33, -1.58) for continuous outcomes and RR of unsatisfactory patient outcome was 0.42 (M-H, random 95% CI; 0.26, 0.68 I2=45%) for dichotomous outcomes compared to that of intranasal saline. The SMD for the sedative effects of intranasal dexmedetomidine was -0.41 (random, 95% CI; -1.09, 0.27 I2=69%) for continuous outcomes and RR was 0.43 (M-H, random 95% CI; 0.32, 0.58 I2=0%) for dichotomous outcomes compared to that of per os benzodiazepines. CONCLUSIONS: This review suggests that intranasal dexmedetomidine is associated with better sedative effects than oral benzodiazepines without producing respiratory depression, but it had a significantly delayed onset of effects.

Rapid progressive atypical atraumatic osteonecrosis of humeral head: a case report.

Osteonecrosis of the humeral head is an uncommon and slow progressive condition. This condition is difficult to be recognized because its initial symptoms are nonspecific. Simple radiography is the standard tool to stage disease progression. However, plain radiographic findings of osteonecrosis are nearly normal in the initial stage. We report a case of 74 years old female patient who have suffered from painful limitation of the shoulder joint. She had no trauma history and no specific predisposing factors for osteonecrosis of the humeral head. To confirm, follow up radiography and shoulder magnetic resonance imaging were performed.

A cardiovascular collapse occurred in the beach chair position for shoulder arthroscopy under general anesthesia -A case report-.

The occurrence of severe hypotension and bradycardia, following placing to the beach chair position from supine during general anesthesia for repair of tendon injury of the rotator cuff of shoulder in a healthy 50 year-old man was described. The Bezold-Jarisch reflex, which is known to inhibit cardiovascular reflex and composed of three kinds of symptoms such as vasodilation, bradycardia and hypotension, has been reported mainly in peripheral nerve block, and may occur during orthostasis, hypovolemia, hemorrhage, supine inferior vena cava compression in pregnancy, interscalene block for shoulder surgery in the sitting position and so on. The bradycardia and hypotension can be more aggravated when causative elements overlaps each other. Anticholinergics and vasopressor were injected intravenously, and position of the patient was changed to the supine position immediately resulting in a normal vital signs dramatically.

The general anesthesia experience of deletion 8p syndrome patient -A case report-.

A deletion 8p syndrome is a relatively uncommon congenital disease characterized by mental retardation associated with multiple malformation that make anesthetic management a challenge. Anesthetic management of a patient with deletion 8p syndrome may pose a serious problem mainly from difficult tracheal intubation, aspiration complication and cardiac malformation. We experienced a case of 10 year-old boy with a deletion 8p syndrome who underwent appendectomy under the general anesthesia. Intubation was performed by video glidescope after unsuccessful attempt with Macintosh laryngoscope. A high arched palate, short neck, poor patient cooperation due to mental retardation and occasional autistic behaviour made airway management difficult. This case should alert anesthesiologists to the greater difficulties of managing patients with deletion 8p syndrome.

The optimal effect-site concentration of remifentanil for lightwand tracheal intubation during propofol induction without muscle relaxation.

STUDY OBJECTIVE: To determine the most suitable effect-site concentration of remifentanil during lightwand intubation when administered with a target-controlled infusion (TCI) of propofol at 4.0 µg/mL without neuromuscular blockade. DESIGN: Prospective study using a modified Dixon's up-and-down method. SETTING: Operating room of an academic hospital. PATIENTS: 28 ASA physical status 1 and 2 patients, aged 18-65 years, scheduled for minor elective surgery. INTERVENTIONS: Anesthesia was induced by TCI propofol effect-site concentration to 4.0 µg/mL, and the dose of remifentanil given to each patient was determined by the response of the previously tested patient using 0.2 ng/mL as a step size. The first patient was tested at a target effect-site concentration of 4.0 ng/mL of remifentanil. If intubation was successful, the remifentanil dose was decreased by 0.2 ng/mL; if it failed, the remifentanil dose was increased by 0.2 ng/mL. Successful intubation was defined as excellent or good intubating conditions. MEASUREMENTS AND MAIN RESULTS: The remifentanil effect-site concentration was measured. The optimal effect-site concentration of remifentanil for lightwand tracheal intubation during propofol induction using 2% propofol target effect-site concentration to 4 µg/mL was 2.16 ± 0.19 ng/mL. From probit analysis, the effect-site concentration of remifentanil required for successful lightwand intubation in 50% (EC50) and 95% (EC95) of adults was 2.11 ng/mL (95% CI 1.16-2.37 ng/mL) and 2.44 ng/mL (95% CI 2.20-3.79 ng/mL), respectively. CONCLUSION: A remifentanil effect-site concentration of 2.16 ± 0.19 ng/mL given before a propofol effect-site concentration of 4 µg/mL allowed lightwand intubation without muscle relaxant.

Ultrasound-guided greater occipital nerve block for patients with occipital headache and short term follow up.

BACKGROUND: The greater occipital nerve (GON) block has been frequently used for different types of headache, but performed with rough estimates of anatomic landmarks. Our study presents the values of the anatomic parameters and estimates the effectiveness of the ultrasound-guided GON blockade. METHODS: The GON was detected using ultrasound technique and distance from external occipital protuberance (EOP) to GON, from GON to occipital artery and depth from skin to GON was measured in volunteers. Patients with occipital headache were divided into two groups (ultrasound-guided block: group S, conventional blind block: group B) and GON block was performed. The same parameters were measured on group S and VAS scores were assessed at pretreatment, 1 week and 4 weeks after treatment on both groups. RESULTS: The GON had distance of 23.1 ± 3.4 mm (right) and 20.5 ± 2.8 mm (left) from EOP to GON. Its depth below the skin was 6.8 ± 1.5 mm (right) and 7.0 ± 1.3 mm (left). The distance from GON to occipital artery was 1.5 ± 0.6 mm (right) and 1.2 ± 0.6 mm (left) in volunteers. Initial VAS score of group S and group B patients were 6.4 ± 0.2 and 6.5 ± 0.2. VAS score of 4 weeks after injection were 2.3 ± 0.2 on group S and 3.8 ± 0.3 on group B (P = 0.0003). CONCLUSIONS: The parameters measured in this study should be useful for GON block and ultrasound-guided blockade is likely to be a more effective technique than blind blockade in occipital headache treatment.

Bilateral upper lobe pulmonary edema during gynecologic laparoscopic surgery in the Trendelenberg position -A case report-.

A 25-year-old woman was diagnosed with a ruptured ectopic pregnancy. During laparoscopic surgery, the patient was in the Trendelenberg position (20° degrees). Massive froth in the endotracheal tube was observed at the end of surgery. A portable chest x-ray, checked at the end of the operation, showed diffuse haziness in both upper lung fields. After one hour of aggressive treatment with drugs and positive mechanical ventilation, the amount of froth in the endotracheal tube was reduced considerably. Considering the symptom and radiologic findings, we concluded that diffuse bilateral upper lung field haziness was due to atypical pulmonary edema. We speculated that the rapid improvement of pulmonary edema was due to redistribution of fluid to the lowest part of lung by immediate reversing the patient's Trendelenberg position, along with aggressive treatment.

Comparison of volume-control and pressure-control ventilation during one-lung ventilation.

BACKGROUND: We hypothesized that pressure control ventilation allows a more even distribution in the lung and better maintenance of the mean airway pressure than is achieved with volume control ventilation. We try to compare the effect of pressure control ventilation (PC) with that of volume control ventilation without an end-inspiratory pause (VC) during one-lung ventilation (OLV) in an anesthetized, paralyzed patient for performing thoracopic bullectomy of the lung. METHODS: We ventilated 20 patients with VC and PC after the insertion of a thoracoscope in continual order for, at least for 15 minutes, for each, VC and PC procedure. At the end of VC and PC, the respiratory mechanics, gasometrics, and hemodynamic parameters were measured and collected. RESULTS: We found no significant differences between VC and PC except for the peak inspiratory airway pressure (PIP), the mean airway pressure and the arterial oxygen partial pressure (PaO2). The PIP was significantly decreased from 27.0 +/- 6.0 cmH2O (VC) to 21.8 +/- 5.4 cmH2O (PC). The mean airway pressure was significantly increased from 8.6 +/- 1.6 cmH2O (VC) to 9.4 +/- 2.0 cmH2O (PC), and the PaO2 was significantly increased from 252.9 +/- 97.3 mmHg (VC) to 285.2 +/- 103.8 mmHg (PC). CONCLUSIONS: If PC allows mechanical ventilation with the same tidal volume and respiratory rate as VC during OLV, then PC significantly increases the PaO2 but this is not clinically significant, and the PC significantly decreases the PIP, which induces barotrauma or volutrauma when the PIP is excessively high.

Awareness during general anesthesia due to the unlock position of the vaporizer : A report on two cases.

Awareness with recall after general anesthesia is a relatively infrequent occurrence and this awareness is often associated with significant adverse psychological sequelae, including posttraumatic stress disorder. The occurrence of awareness is often the consequence of the light anesthetic techniques with using minor anesthetic agents. Because the locking lever of the Penlon Sigma Delta Anesthetic vaporizer (sevoflurane) was at the unlock position, disconnection happened between the anesthetic machine and the vaporizer (the Selectatec(R) vaporizing system). In our two cases, the inhalation agents were not supplied and awareness with recall was identified after surgery. We recommend to check the concentration of the inhalation agents by monitoring the concentration of using endtidal inhalation agents and to measure the hypnotic level of anesthesia via the bispectral index (BIS) and the auditory evoked potential (AEP).