Coherent charge oscillations in a bilayer graphene double quantum dot.

The coherent dynamics of a quantum mechanical two-level system passing through an anti-crossing of two energy levels can give rise to Landau-Zener-Stückelberg-Majorana (LZSM) interference. LZSM interference spectroscopy has proven to be a fruitful tool to investigate charge noise and charge decoherence in semiconductor quantum dots (QDs). Recently, bilayer graphene has developed as a promising platform to host highly tunable QDs potentially useful for hosting spin and valley qubits. So far, in this system no coherent oscillations have been observed and little is known about charge noise in this material. Here, we report coherent charge oscillations and [Formula: see text] charge decoherence times in a bilayer graphene double QD. The charge decoherence times are measured independently using LZSM interference and photon assisted tunneling. Both techniques yield [Formula: see text] average values in the range of 400-500 ps. The observation of charge coherence allows to study the origin and spectral distribution of charge noise in future experiments.

Particle-hole symmetry protects spin-valley blockade in graphene quantum dots.

Particle-hole symmetry plays an important role in the characterization of topological phases in solid-state systems1. It is found, for example, in free-fermion systems at half filling and it is closely related to the notion of antiparticles in relativistic field theories2. In the low-energy limit, graphene is a prime example of a gapless particle-hole symmetric system described by an effective Dirac equation3,4 in which topological phases can be understood by studying ways to open a gap by preserving (or breaking) symmetries5,6. An important example is the intrinsic Kane-Mele spin-orbit gap of graphene, which leads to a lifting of the spin-valley degeneracy and renders graphene a topological insulator in a quantum spin Hall phase7 while preserving particle-hole symmetry. Here we show that bilayer graphene allows the realization of electron-hole double quantum dots that exhibit near-perfect particle-hole symmetry, in which transport occurs via the creation and annihilation of single electron-hole pairs with opposite quantum numbers. Moreover, we show that particle-hole symmetric spin and valley textures lead to a protected single-particle spin-valley blockade. The latter will allow robust spin-to-charge and valley-to-charge conversion, which are essential for the operation of spin and valley qubits.

Spin relaxation in a single-electron graphene quantum dot.

The relaxation time of a single-electron spin is an important parameter for solid-state spin qubits, as it directly limits the lifetime of the encoded information. Thanks to the low spin-orbit interaction and low hyperfine coupling, graphene and bilayer graphene (BLG) have long been considered promising platforms for spin qubits. Only recently, it has become possible to control single-electrons in BLG quantum dots (QDs) and to understand their spin-valley texture, while the relaxation dynamics have remained mostly unexplored. Here, we report spin relaxation times (T1) of single-electron states in BLG QDs. Using pulsed-gate spectroscopy, we extract relaxation times exceeding 200 µs at a magnetic field of 1.9 T. The T1 values show a strong dependence on the spin splitting, promising even longer T1 at lower magnetic fields, where our measurements are limited by the signal-to-noise ratio. The relaxation times are more than two orders of magnitude larger than those previously reported for carbon-based QDs, suggesting that graphene is a potentially promising host material for scalable spin qubits.

Widening access to veterinary education: descriptive analysis of ethnicity, societal representation and educational background of applicants to veterinary education in Aotearoa New Zealand.

AIMS: To describe the ethnicity of domestic applicants for selection into the professional phase of veterinary education in Aotearoa New Zealand from 2003 to 2019, and to compare this with the ethnic composition of New Zealand society. This study also aims to explore whether there are differences in the demographic features and educational background of Maori applicants compared to non-Maori applicants that may be relevant to widening access to veterinary education. METHODS: This study was conducted with a Kaupapa Maori research methodology. Data for all applicants to the Bachelor of Veterinary Science programme at Massey University (Palmerston North, NZ) from 2003 to 2019 were retrieved from the university's Student Management System and the School of Veterinary Science selection application databases. Self-identified ethnicity was analysed in four time periods (2003-2006, 2007-2012, 2013-2016, 2017-2019) defined by factors that might influence whether an individual chose to apply for selection into the veterinary programme. Gender, age, previous university experience, decile and type of high school, and being first in family to attend university were compared between Maori and non-Maori. RESULTS: From 2003 to 2019, 3,819 individuals submitted 4,802 applications for selection into the veterinary programme. Across all time periods, applicants who identified as Maori (274/4,802; 5.7%) or Pacific (56/4,802; 1.2%) were underrepresented compared to the New Zealand population (Maori 16.5%; Pacific 8.1%), while applicants who identified as European (4,035/4,802; 84%) were over-represented (70.2% of the New Zealand population). The proportion of Maori (p = 0.82) and Pacific (p = 0.31) applicants did not change over time, while the proportion of European applicants decreased from 853/968 (88.1%) to 823/977 (84.2%; p < 0.001). Compared to non-Maori, Maori applicants were more likely to have attended a lower decile school (p < 0.001), have attended a state rather than private or overseas school (p = 0.003) and to have been the first in their family to attend university (p = 0.001). CONCLUSIONS: Maori are underrepresented in the veterinary applicant pool and veterinary profession in comparison to the New Zealand population. Additionally, Maori applicants differed from non-Maori applicants in pre-university factors that are barriers to university attendance. Implementing activities and processes aimed at widening veterinary programme access with the eventual goal of improving the ethnic representation of the veterinary workforce needs to be a priority for the university and profession.

Effects of transcranial direct-current stimulation on laparoscopic surgical skill acquisition.

BACKGROUND: Changes in medical education may limit opportunities for trainees to gain proficiency in surgical skills. Transcranial direct-current stimulation (tDCS) can augment motor skill learning and may enhance surgical procedural skill acquisition. The aim of this study was to determine the effects of tDCS on simulation-based laparoscopic surgical skill acquisition. METHODS: In this double-blind, sham-controlled randomized trial, participants were randomized to receive 20 min of anodal tDCS or sham stimulation over the dominant primary motor cortex, concurrent with Fundamentals of Laparoscopic Surgery simulation-based training. Primary outcomes of laparoscopic pattern-cutting and peg transfer tasks were scored at baseline, during repeated performance over 1 h, and again at 6 weeks. Intent-to-treat analysis examined the effects of treatment group on skill acquisition and retention. RESULTS: Of 40 participants, those receiving tDCS achieved higher mean(s.d.) final pattern-cutting scores than participants in the sham group (207·6(30·0) versus 186·0(32·7) respectively; P = 0·022). Scores were unchanged at 6 weeks. Effects on peg transfer scores were not significantly different (210·2(23·5) in the tDCS group versus 201·7(18·1) in the sham group; P = 0·111); the proportion achieving predetermined proficiency levels was higher for tDCS than for sham stimulation. Procedures were well tolerated with no serious adverse events and no decreases in motor measures. CONCLUSION: The addition of tDCS to laparoscopic surgical training may enhance skill acquisition. Trials of additional skills and translation to non-simulated performance are required to determine the potential value in medical education and impact on patient outcomes. Registration number: NCT02756052 (https://clinicaltrials.gov/).

Development and validation of a feline abdominal palpation model and scoring rubric.

Simulation in veterinary education enables clinical skills practice without animal use. A feline abdominal palpation model was created that allows practice in this fractious species. This study assessed the model and rubric using a validation framework of content evidence, internal structure and relationship with level of training. Content Evidence: Veterinarians accepted this model as a helpful training tool for students (median=4 on five-point Likert scale). Internal Structure Evidence: G-coefficients were low for first- and second-year students (0.28 and 0.23), but were acceptable for veterinarians (0.61). Internal consistency values (0.24, 0.42 and 0.67) followed a similar pattern. Thus, scores were more reliable for veterinarians than for the students. Evidence of Relationship with Level of Training: Although level of training impacted reliability, its effect on performance scores was inconsistent. Analysis of variance (ANOVA) identified no differences among the groups of students and veterinarians. However, effect size between first- and third-year students was medium to large (0.62). Effect sizes between the veterinarians and student groups were small. Although the model and rubric appeared valid for experts, modifications would be necessary to generate reliable scores for students. These results allow greater understanding of the needs of students utilising a low-fidelity model.

Standardised clients as assessors in a veterinary communication OSCE: a reliability and validity study.

In human medicine, standardised patients (SP) have been shown to reliably and accurately assess learners' communication performance in high-stakes certification Objective Structured Clinical Examinations (OSCE), offering a feasible way to reduce the need for recruitment, time commitment and coordination of faculty assessors. In this study, we evaluated the use of standardised clients (SC) as a viable option for assessing veterinary students' communication performance. We designed a four-station, two-track communication skills OSCE. SC assessors used an adapted nine-item Liverpool Undergraduate Communication Assessment Scale (LUCAS). Faculty used a 21-item checklist derived from the Calgary-Cambridge Guide (CCG) and a five-point global rating scale. Participants were second year veterinary students (n=96). For the four stations, intrastation reliability (α) ranged from 0.63 to 0.82 for the LUCAS, and 0.73 to 0.87 for the CCG. The interstation reliability coefficients were 0.85 for the LUCAS and 0.89 for the CGG. The calculated Generalisability (G) coefficients were 0.62 for the LUCAS and 0.60 for the CGG. Supporting construct validity, SC and faculty assessors showed a significant correlation between the LUCAS and CCG total percent scores (r=0.45, P<0.001), and likewise between the LUCAS and global rating scores (r=0.49, P<0.001).Study results support that SC assessors offer a reliable and valid approach for assessing veterinary communication OSCE.

Bronchial collapse during bronchoalveolar lavage in horses is an indicator of lung inflammation.

REASONS FOR PERFORMING STUDY: The bronchoalveolar lavage (BAL) procedure can return variable volumes of fluid, possibly depending on the presence of bronchial collapse during fluid aspiration and on the severity of lung inflammation. OBJECTIVES: We tested the hypothesis that horses with bronchial collapse during BAL are at higher risk of having severe lung inflammation. STUDY DESIGN: Prospective field study. METHODS: Bronchial collapse was graded using a new simple scoring method (0, 1 or 2) during a standardised BAL procedure in the field on 131 horses with normal, mild/moderate or severe lower airway inflammation on cytology of BAL fluid. RESULTS: Of the 131 horses, 37 (28%), 55 (42%) and 39 (30%) horses had bronchial collapse scores of 0, 1 and 2, respectively. There was a difference in collapse scores between all the BAL inflammation categories (P<0.001). Severe collapse had a positive predictive value of 0.95 for both mild/moderate and severe BAL inflammation, with a prevalence of 63% and 20%, respectively. The BAL fluid return volume in the horses with severe collapse scores was lower than volumes in the partial (score 1/2) and no collapse (score 0/2) groups (P<0.001). The BAL fluid volume was negatively correlated with BAL neutrophil percentage (P<0.001). CONCLUSIONS: Airway collapse during BAL is associated with airway inflammation and neutrophilia. POTENTIAL RELEVANCE: During a standardised BAL procedure, clinicians can expect lung inflammation in horses that have bronchial collapse and bronchial collapse in horses with lung inflammation. Lung inflammation may be a contributing factor in the mechanism of bronchial collapse during BAL in horses.

[Pleural empyema - treatment strategies in light of etiology]. / Pleuraempyem - Behandlungsstrategien unter Berücksichtigung der Ätiologie.

The variety of strategies in the treatment of parapneumonic pleural empyema demonstrates the ambiguity for the method of choice. Parapneumonic pleural empyema has been classified into different stages and classes. While the American Thoracic Society (ATS) classification is based on the natural course of the disease, or according to the radiological, physical and biochemical characteristics respectively, the American College of Chest Physicians (ACCP) has categorized the patients with pleural empyema according to the risk of a poor outcome. The British Thoracic Society (BTS) developed a treatment algorithm based on a systematic review of peer-reviewed literature. With regard to this classification the management of parapneumonic and postoperative pleural empyema is based on the stage of the disease. Therapeutic strategies include chest tube alone, chest tube with fibrinolysis, thoracoscopic debridement and decortication in open or minimally invasive techniques, closed empyemectomy, or treatment with thoracomyoplasty, open window treatment or vacuum clothing with negative pressure. The different conservative and operative therapeutic possibilities determinate the central treatment function of thoracic surgery.

Xenon anesthesia impairs hepatic oxygenation and perfusion in healthy pigs.

BACKGROUND: Over the last 15 years, there has been growing interest in the noble gas xenon as a new inhalational anesthetic. This is due to its favorable pharmacological properties such as short onset and offset, as well as its hemodynamic stability. However, most volatile anesthetics appear to play an important role in the multi-factorial etiology of perioperative liver injury by decreasing liver blood flow with a subsequent reduction of hepatic oxygen supply. However, the effects of the anesthetic gas xenon on hepatic perfusion and oxygenation have not been completely investigated. METHODS: Following ethical approval, 18 anesthetized and acutely monitored pigs were randomly assigned to the two following groups: 9 animals received xenon anesthesia in increasing inspiratory concentrations of 0%, 20%, 50%, and 65% in addition to their basic intravenous anesthesia; 9 animals served as a control group. Measurement points for systemic and regional hemodynamic and oxygenation parameters were performed 30 min after changing the xenon concentration. RESULTS: Xenon elicited dose-dependent systemic hemodynamic changes such that the mean arterial pressure did not change, while the heart rate and cardiac output decreased by about 30%, thereby indicating an increase in the systemic vascular resistance. Portal venous blood flow decreased, while hepatic arterial blood flow was unchanged. The oxygen supply of the liver was reduced, but not the rate of indocyanine plasma disappearance from the liver. Furthermore, the increase of liver surface pO2 to systemic hyperoxia was absent, and hepatic lactate uptake was reduced. CONCLUSION: Xenon, in addition to basic intravenous anesthesia, elicited a decrease in heart rate and cardiac output and an increase in mean arterial pressure. Similar to volatile anesthetics, xenon does reduce portal venous flow and influences hepatic tissue oxygenation. In contrast, hepatic arterial blood flow remains stable in the presence of xenon, and no changes in the hepatic arterial buffer responses were evident. Xenon does affect hepatic perfusion and oxygenation.

Xenon or propofol anaesthesia for patients at cardiovascular risk in non-cardiac surgery.

BACKGROUND: The results of two European multi-centre trials on xenon anaesthesia led to the hypothesis that a xenon-based anaesthetic would keep left ventricular (LV) and circulatory function more stable than a propofol-based anaesthetic, in patients with coronary artery disease (CAD). METHODS: In a prospective, randomized design, 40 patients of ASA classes III and IV with known CAD were anaesthetized for elective non-cardiac surgery with either xenon (n=20) or propofol (n=20), each combined with remifentanil. Target criteria were intraoperative LV function as evaluated by transoesophageal echocardiography (TOE: Tei index, circumferential fibre shortening), arterial pressure, and heart rate (HR). RESULTS: Mean arterial pressure was decreased with propofol but was stable at pre-anaesthetic level with xenon (P<0.02) and HR was lower with xenon (P<0.01). The Tei index (also known as myocardial performance index) improved from 0.53 (0.14) to 0.45 (0.10) after 1 h with xenon and changed from 0.50 (0.14) to 0.55 (0.20) with propofol anaesthesia [means (SD); P=0.01 between the groups]. Deviation of circumferential fibre shortening from expected value after 1 h was -2 (14)% with xenon and -14 (18)% with propofol [means (SD); P=0.03]. There were no perioperative signs of acute myocardial ischaemia (TOE, ECG, and troponin T release). CONCLUSIONS: Xenon anaesthesia provided a higher arterial pressure level than propofol, with no signs of cardiovascular compromise, in patients with CAD. Echocardiographic indices showed better LV function with xenon.

Autonomic cardiac control with xenon anaesthesia in patients at cardiovascular risk.

BACKGROUND: The cardiovascular stability found with xenon anaesthesia may be caused by absence of circulatory depression. Xenon may also act directly on autonomic cardiovascular control. METHODS: In a prospective, randomized design, 26 patients (ASA class III and IV) with increased cardiac risk were anaesthetized for elective non-cardiac surgery with either xenon (n = 13) or propofol (n = 13), each combined with remifentanil. From intraoperative Holter ECG, 5-min intervals of stable sinus rhythm were analysed at baseline anaesthesia with etomidate/remifentanil, and after 30 and 60 min of propofol or xenon anaesthesia. Target criteria were total power and ratio of low to high frequency power of the heart rate (HR) power spectrum between 0.003 and 0.4 Hz, indicating global activity and sympatho-vagal balance of autonomic modulation of HR. RESULTS: When compared with baseline, total power decreased with propofol from 8.6 (1.6) to 7.1 (0.5) and to 7.8 (1.1) ms(2) at 30 and 60 min, respectively, [mean (sd) of logarithmic transform] and was unchanged with xenon (P = 0.02; anova). The low/high frequency power ratio changed from 3.0 (3.5) to 4.3 (4.3) and 4.1 (6.2), respectively, with xenon and from 3.9 (3.6) to 1.8 (1.5) and 1.8 (0.8) with propofol (P = 0.04; generalized linear model test). Mean arterial pressure was significantly higher with xenon throughout (P < 0.001; anova). CONCLUSIONS: Propofol caused a decrease in arterial pressure as well as autonomic HR modulation, but xenon did not. The higher arterial pressure with xenon anaesthesia may be explained by less suppression of sympatho-vagal balance.

Patients' self-evaluation after 4-12 weeks following xenon or propofol anaesthesia: a comparison.

BACKGROUND AND OBJECTIVE: The aim of this study was to assess postoperative patients' self-evaluation after xenon anaesthesia compared to total intravenous anaesthesia with propofol. METHODS: 160 patients aged 18-60 yr, ASA I-II undergoing elective surgery took part in this randomised-controlled trial. After approval by the local Ethics Committee and as soon as the patients had given their written informed consent, they were randomly allocated to either the xenon (n = 80) or propofol (n = 80) group. In both groups remifentanil was used as opioid. The postoperative patients' self-evaluation was assessed with a double-blind telephone poll. Early spatial orientation, patients' self-evaluation of anaesthesia, choice of the same anaesthesia for future operations and recall of uncomfortable feelings after anaesthesia were determined. RESULTS: 116 Patients were analysed, 63 in the xenon and 53 in the propofol group. The two study groups were comparable with respect to age, weight, height, gender and ASA classification. The two groups indicated similar values in the early spatial orientation at the onset of recovery and thereafter. Patients' self-evaluation of anaesthesia with main emphasis at high marks and repetition of the same anaesthesia if necessary were similar in both groups. Recalls of uncomfortable feelings were comparable but not for postoperative pain and appetite/thirst which appeared with a significantly higher incidence in the xenon group. CONCLUSIONS: Patients' self-evaluation and memory of early spatial orientation following xenon anaesthesia are comparable to propofol.

Xenon anaesthesia may preserve cardiovascular function in patients with heart failure.

BACKGROUND: The hypothesis that xenon anaesthesia provided haemodynamic stability was tested in patients with heart failure in a prospective, randomized, single-blind design. METHODS: Twenty-six patients scheduled for implantation of a cardioverter-defibrillator (ICD) received xenon 60-65% in oxygen (xenon group, n = 12) or propofol 3 mg/kg/h (propofol group, n = 14), both combined with remifentanil 0.2 microg/kg/min. After induction of anaesthesia with etomidate and remifentanil, heart rate (HR), mean arterial pressure (MAP) and left ventricular ejection fraction (LVEF) were recorded. After 60 min of propofol or xenon anaesthesia, the same parameters were recorded. RESULTS: While HR decreased in both groups, MAP was unchanged with xenon (73 vs. 76 mmHg) and decreased with propofol (from 78 to 64 mmHg, P < 0.02). LVEF was stable in both groups [32% vs. 37%, xenon (NS), and 30% vs. 34%, propofol (NS)]. Preload, as measured by end-diastolic volume (EDV), did not change (66 vs. 63 ml with xenon; 79 vs. 81 ml with propofol, both NS). Afterload, as determined by end-systolic pressure-volume product (ESPV), decreased with propofol (6760 vs. 4920 ml mmHg) but not with xenon (4060 vs. 3780 ml mmHg, P < 0.01 between groups). CONCLUSION: With propofol, MAP is reduced and LVEF is not increased in spite of reduced afterload. In contrast, MAP and LVEF are maintained with xenon.

Effects of xenon anaesthesia on the circulatory response to hypoventilation.

BACKGROUND: Circulatory response to hypoventilation is aimed at eliminating carbon dioxide and maintaining oxygen delivery (DO(2)) by increasing cardiac output (CO). The hypothesis that this increase is more pronounced with xenon than with isoflurane anaesthesia was tested in pigs. METHODS: Twenty pigs received anaesthesia with xenon 0.55 MAC/remifentanil 0.5 microg kg(-1) min(-1) (group X, n=10) or isoflurane 0.55 MAC/remifentanil 0.5 microg kg(-1)min(-1) (group I, n=10). CO, heart rate (HR), mean arterial pressure (MAP) and left ventricular fractional area change (FAC) were measured at baseline, after 5 and 15 min of hypoventilation and after 5, 15 and 30 min of restored ventilation. RESULTS: CO increased by 10-20% with both anaesthetics, with an equivalent rise in HR, maintaining DO(2) in spite of a 20% reduction in arterial oxygen content. Decreased left ventricular (LV) afterload during hypoventilation increased FAC, and this was more marked with xenon (0.60-0.66, P<0.05 compared with baseline and isoflurane). This difference is attributed to negative inotropic effects of isoflurane. Increased pulmonary vascular resistance during hypoventilation was found with both anaesthetics. CONCLUSION: The cardiovascular effects observed in this model of moderate hypoventilation were sufficient to maintain DO(2). Although the haemodynamic response appeared more pronounced with xenon, differences were not clinically relevant. An increase in FAC with xenon is attributed to its lack of negative inotropic effects.

Haemodynamic effects of haemorrhage during xenon anaesthesia in pigs.

BACKGROUND: It was hypothesized that xenon would stabilize mean arterial pressure (MAP) in haemorrhagic shock, recovery, and volume resuscitation, because a higher MAP has been observed with xenon, when compared with isoflurane anaesthesia. The responses to haemorrhage and subsequent volume replacement were therefore compared between xenon and isoflurane anaesthesia, in pigs. METHODS: Pigs were randomized to anaesthesia with xenon 0.55 MAC (group Xe, n=9) or isoflurane 0.55 MAC (group Iso, n=9), each with remifentanil 0.5 microg kg(-1) min(-1). MAP, heart rate, cardiac output (CO), and left ventricular fractional area change (FAC) were collected at control (1), after haemorrhage (20 ml kg(-1)) (2), after 10 min of recovery (3), after volume replacement (4), and 30 min later (5). Data were analysed by two-way repeated measures anova. RESULTS: Blood loss decreased MAP (Xe: 103 [21] to 53 [24] mm Hg; Iso: 92 [18] to 55 [14] mm Hg) and CO (Xe: 4.1 [0.8] to 2.6 [0.5] litre min(-1); Iso: 5.1 [1.1] to 3.8 [1.2] litre min(-1)), in spite of significant tachycardia. MAP and CO recovered to about 75% of control, and subsequent volume replacement completely reversed symptoms in both groups, but increased FAC only with xenon. CONCLUSION: Haemodynamic response to acute haemorrhage appeared faster with xenon/remifentanil than with isoflurane/remifentanil anaesthesia. In particular MAP decrease and short-term recovery were more marked with xenon (P<0.02). In the xenon group, volume replacement increased FAC compared with control and isoflurane (P<0.02).

Acute effects of monounsaturated fatty acids with and without omega-3 fatty acids on vascular reactivity in individuals with type 2 diabetes.

AIMS/HYPOTHESIS: We examined the acute postprandial effects of meals containing unsaturated fatty acids on flow-mediated dilation (FMD) of the brachial artery and triacylglycerols in individuals with type 2 diabetes. We hypothesised that consumption of omega-3 fatty acids would enhance vascular function. Saturated fat reduces FMD for several hours, but there is inconsistent evidence about whether foods containing unsaturated fats impair FMD acutely. Little is known about the acute effects of omega-3 fatty acids on vascular reactivity. METHODS: We measured FMD before and 4 h after 3 test meals (50 g fat, 2,615 kJ) in 18 healthy adults with type 2 diabetes. The monounsaturated fatty acids (MUFA) meal contained 50 g fat from high oleic safflower and canola oils. Two additional meals were prepared by replacing 7% to 8% of MUFA with docosahexaenoic acid and eicosapentaenoic acid from sardine oil or alpha-linolenic acid from canola oil. RESULTS: In the sample as a whole, FMD was increased 17% at 4 h vs. the fasting baseline. After the MUFA meal, subjects with the largest increases in triacylglycerols had the largest FMD decreases. The opposite pattern was observed after meals containing docosahexaenoic acid and eicosapentaenoic acid or alpha-linolenic acid. In subjects with high fasting triacylglycerols, meals containing 3 to 5 g of omega-3 fatty acids increased FMD by 50% to 80% and MUFA alone had no significant effects on FMD. CONCLUSIONS/INTERPRETATION: Endothelium-dependent vasodilation was not impaired 4 h after meals containing predominantly unsaturated fatty acids. The fatty acid composition of the meal and the metabolic status of the individual determine the vascular effects of a high-fat meal.

Randomized controlled trial of the haemodynamic and recovery effects of xenon or propofol anaesthesia.

BACKGROUND: There is limited clinical experience with xenon in a large number of patients. We present intra- and postoperative haemodynamic and recovery data comparing xenon and total intravenous anaesthesia with propofol. METHODS: A total of 160 patients aged 18-60 years (ASA I and II) undergoing elective surgery took part in this prospective non-blinded randomized controlled trial. After local ethics committee approval and written informed consent, patients were allocated randomly to either the xenon or the propofol group. Anaesthesia was induced with propofol and remifentanil and was maintained with xenon at 60% (minimal alveolar concentration 0.95) or with propofol 0.1-0.12 mg kg(-1) min(-1). Remifentanil was titrated to clinical need in both groups. RESULTS: The two study groups were comparable with respect to age, weight, height, gender and ASA classification. Baseline in heart rate and systolic arterial pressure (SAP) were comparable in both groups. Following induction, SAP initially decreased but returned to baseline values over 15 min in the xenon group and differed significantly from the propofol group. Heart rate decreased significantly only in the xenon group and remained at stable values. Occurrence and duration of hypertension, hypotension and bradycardia showed no significant difference between groups. Patient recovery time in the post-anaesthetic care unit and recovery from anaesthesia was similar in the two groups. CONCLUSIONS: After induction the xenon/opioid regimen maintains systolic blood pressure at baseline levels and a low heart rate. No differences between groups were found in haemodynamic stability during anaesthesia. Recovery from xenon anaesthesia was similar to that observed in the propofol group.

Effects of xenon anaesthesia on intestinal oxygenation in acutely instrumented pigs.

BACKGROUND: Xenon is a narcotic gas that might be able to replace volatile anaesthetics or nitrous oxide due to its favourable pharmacological properties, such as providing haemodynamic stability. Intestinal oxygenation is affected by most volatile anaesthetics as a result of cardiodepressive effects. Reducing oxygenation of the gut might be a factor leading to perioperative organ dysfunction. This animal study was designed to assess the effects of xenon on intestinal oxygenation. METHODS: After ethical approval, 24 anaesthetized, acutely instrumented pigs were randomly assigned to three groups: nine animals received xenon anaesthesia with inspiratory concentrations of 0, 20, 50 and 65% in addition to their basic i.v. anaesthesia, nine animals served as a study control group, and five animals were used to assess model stability. Measurement of systemic and regional haemodynamic and oxygenation parameters was made 30 min after changing the xenon concentration. RESULTS: Xenon elicited dose-dependent systemic haemodynamic changes: heart rate and cardiac output decreased by 30%, while mean arterial pressure was stable. Superior mesenteric artery blood flow was lower in the xenon group. Vascular resistance of the superior mesenteric artery increased. The small intestinal oxygen supply decreased with increasing xenon concentration; the mucosal tissue oxygen partial pressure decreased but did not reach hypoxic (<5 mm Hg) values. Serosal tissue oxygen partial pressure was maintained. CONCLUSIONS: Xenon, in addition to basic i.v. anaesthesia, elicited a decrease in cardiac output and maintained mean arterial pressure. Intestinal oxygenation was maintained, although regional macrohaemodynamic perfusion decreased. Xenon does not impair intestinal oxygenation under physiological conditions.

Biological correlates of day-to-day variation in flow-mediated dilation in individuals with Type 2 diabetes: a study of test-retest reliability.

AIMS/HYPOTHESIS: Dysfunction of the vascular endothelium is commonly observed in Type 2 diabetes, and endothelial function may be an important outcome for clinical trials in diabetic samples. However, the most commonly used non-invasive test of endothelial function (flow-mediated dilation [FMD]) is technically challenging to perform, and no previous studies have carefully examined the reproducibility of FMD measurements in individuals with Type 2 diabetes. In this study, we tested the hypothesis that larger day-to-day changes in insulin and glucose are associated with larger fluctuations in FMD. METHODS: Ultrasound was used to measure the FMD (% change from baseline diameter) of the brachial artery in 18 healthy adults with Type 2 diabetes on three separate occasions, in the absence of changes to diet, activity level or medications. The CV and mean deviations between pairs of FMD scores in the same individual were used as the primary outcome variables. RESULTS: The CV for FMD (29.7%) was higher than the level traditionally accepted for biochemical assays. However, this CV estimate is within the low range of published values for FMD in healthy individuals. FMD scores were not significantly correlated with glucose or insulin levels. However, subjects with the largest variability in FMD also showed the largest fluctuations in glucose ( r=0.52), insulin ( r=0.47) and heart rate ( r=0.48) ( p