An adjoint method for determining the sensitivity of island size to magnetic field variations

An adjoint method to calculate the gradient of island width in stellarators is presented and applied to a set of magnetic field configurations. The underlying method for calculation of the island width is that of Cary & Hanson (Phys. Fluids B, vol. 3, issue 4, 1991, pp. 1006-1014) (with a minor modification), and requires that the residue of the island centre be small. Therefore, the gradient of the residue is calculated in addition. Both the island width and the gradient calculations are verified using an analytical magnetic field configuration introduced by Reiman & Greenside (Comput. Phys. Commun., vol. 43, issue 1, 1986, pp. 157-167). The method is also applied to the calculation of the shape gradient of the width of a magnetic island in a National Compact Stellarator Experiment (NCSX) vacuum configuration with respect to positions on a coil. A gradient-based optimization is applied to a magnetic field configuration studied by Hanson & Cary (Phys. Fluids, vol. 27, issue 4, 1984, pp. 767-769) to minimize stochasticity by adding perturbations to a pair of helical coils. Although only vacuum magnetic fields and an analytical magnetic field model are considered in this work, the adjoint calculation of the island width gradient could also be applied to a magnetohydrodynamic (MHD) equilibrium if the derivative of the magnetic field, with respect to the equilibrium parameters, is known. Using the island width gradient calculation presented here, more general gradient-based optimization methods can be applied to design stellarators with small magnetic islands. Moreover, the sensitivity of the island size may itself be optimized to ensure that coil tolerances, with respect to island size, are kept as high as possible

Predictors of deep-vein thrombosis in subarachnoid hemorrhage: a retrospective analysis

Background: Subarachnoid hemorrhage is a severe subtype of hemorrhagic stroke, and deep-vein thrombosis is a frequent complication detected in these patients. In addition to other well-established risk factors, the early activation of coagulation systems present in patients with subarachnoid hemorrhage could potentially play a role in the incidence of deep-vein thrombosis. This study aims to identify possible predictors for deep-vein thrombosis related to subarachnoid hemorrhage. Methods: We conducted a retrospective cohort study on patients with a diagnosis of subarachnoid hemorrhage who presented to our institution between 1 January 2014 and 1 August 2018. We reviewed electronic medical records and analyzed several parameters such as Fisher scale, World Federation of Neurosurgical Surgeons scale, aneurysm site, surgical or endovascular treatment, decompressive craniectomy, vasospasm, infection (meningitis and pneumonia), presence of motor deficit, length of stay in the ICU, length of hospital stay, number of days under ventilator support, d-dimer at hospitalization, and the time to thromboprophylaxis (days). Results: The univariate analysis showed that intraparenchymal cerebral hemorrhage, d-dimer at hospitalization, the time to thromboprophylaxis, motor deficit, and aneurysm located at the internal carotid artery were statistically significant factors. Intraparenchymal cerebral hemorrhage (OR 2,78 95%CI 1.07\u20137.12), motor deficit (OR 3.46; 95%CI 1.37\u20139.31), and d-dimer at hospitalization (OR 1.002 95% CI 1.001\u20131.003) were demonstrated as independent risk factors for deep-vein thrombosis. Length of hospital stay was also found to be significantly longer in patients who developed deep-vein thrombosis (p value 0.018). Conclusion: Elevated d-dimer level at the time of hospitalization, motor deficit, and the presence of an intraparenchymal hemorrhage are independent risk factors for deep-vein thrombosis. Patients with DVT also had a significantly longer hospital stay. Even though further studies are needed, patients with elevated d-dimer at hospitalization and intraparenchymal cerebral hemorrhage may benefit from a more aggressive screening strategy for deep-vein thrombosis

Extensively drug-resistant and multidrug-resistant gram-negative pathogens in the neurocritical intensive care unit

Background: Abrupt increase of multidrug-resistant, extensively drug-resistant, and pandrug-resistant bacteria may complicate the course, management, and costs of neurocritical patients and is associated with high morbidity and mortality rates. No data exists regarding risk factors for colonization by gram-negative pathogens in neurocritical patients. The aim of the study was to identify risk factors associated with colonization by multidrug-resistant, extensively drug-resistant, and pandrug-resistant gram-negative bacteria in neurocritical patients. Methods: We conducted a retrospective cohort study in a neurointensive care unit over a period of 3\ua0years. We included adult neurocritical patients admitted for more than 48\ua0h. We analyzed several factors including both anamnestic factors and admission diagnosis. Results: Four hundred twenty neurocritical patients were retrospectively enrolled. Seventy-three patients developed colonization by multidrug-resistant and 53 by extensively drug-resistant gram negative pathogens. Logistic regression identified intensive care unit length of stay (LOS) as the strongest predictor for both multidrug-resistant (AUC 0.877; 95% CI 0.841\u20130.913) and extensively drug-resistant (AUC 0.839 0.787\u20130.892) gram negative pathogens. In addition, external ventricular drainage and intracerebral pressure monitoring catheter were risk factors for XDR. Survival analysis revealed that MDR bacteria colonization happens earlier (log-rank test p\ua0= 0.017). Conclusions: Optimization of healthcare strategies is required in order to reduce patients\u2019 length of stay to prevent multi- and extensively-drug gram-negative colonizations. Indeed, an early external ventricular drainage and intracerebral pressure monitoring catheter removal is deemed necessary as soon as clinically appropriate

Inattentional blindness in anesthesiology: A gorilla is worth one thousand words

Introduction People are not able to anticipate unexpected events. Inattentional blindness is demonstrated to happen not only in naïve observers engaged in an unfamiliar task but also in field experts with years of training. Anaesthesia is the perfect example of a discipline which requires a high level of attention and our aim was to evaluate if inattentional blindness can affect anesthesiologists during their daily activities. Materials and methods An online survey was distributed on Facebook between May 1, 2021 and May 31, 2021. The survey consisted of five simulated cases with questions investigating the anesthetic management of day-case surgeries. Each case had an introduction, a chest radiography, an electrocardiogram, preoperative blood testing and the last case had a gorilla embedded in the chest radiography. Results In total 699 respondents from 17 different countries were finally included in the analysis. The main outcome was to assess the incidence of inattentional blindness. Only 34 (4.9%) respondents were able to spot the gorilla. No differences were found between anesthesiologists or residents, private or public hospitals, or between medical doctors with different experience. Discussion Our findings assess that inattentional blindness is common in anesthesia, and ever-growing attention is deemed necessary to improve patient safety; to achieve this objective several strategies should be adopted such as an increased use of standardized protocols, promoting automation based strategies to reduce human error when performing repetitive tasks and discouraging evaluation of multiple consecutive patients in the same work shifts independently of the associated complexity

Safety in training for ultrasound guided internal jugular vein CVC placement: a propensity score analysis

Background: Central venous catheter (CVC) placement is a routine procedure but is potentially associated with severe complications. Relatively small studies investigated if the use of ultrasound is effective in bridging the skill gap between proficient and not proficient operators, while patient safety during training remains a controversial topic. The first aim of this study was to evaluate if resident proficiency affects the failure rate in CVC positioning under ultrasound guidance. In addition, it aimed to investigate the different rate of complications between proficient and non proficient residents. Methods: We conducted a cohort study including CVC placed by residents at the University Hospital of Padova, from November 1, 2012 to July 9, 2020 comparing proficient and non proficient residents. To avoid bias the two cohorts were matched using propensity score. Results: A total of 356 residents positioned 2310 CVC during the 8 year study period. Among them, two groups of 1060 CVCs each were matched with a propensity score analysis. There was no difference in the failure rate among the groups (2.8 vs 2.7%, p-value 0.895). Moreover, cohorts had the same rate of hematomas, catheter tip malposition, arterial puncture and pneumothorax. No cases of hemothorax were reported. Conclusions: We found the same rate of success and incidence of adverse complications among cohorts, meaning that the process of skill acquisition is safe as long as appropriate training and direct supervision by a senior consultant are available

Nasal/orotracheal tube switch to reduce length of mechanical ventilation in neurocritical patients: A propensity score matched analysis

Introduction and objectives: Nasotracheal intubation was advocated to increase patients comfort and tube tolerance, but no study showed a clear benefit of nasotracheal intubation over orotracheal intubation. Neurocritically ill patients are a fragile group with specific requirements regarding ventilation and sedation. The aim of this study was to evaluate whether nasotracheal intubation might reduce length of mechanical ventilation in neurocritically ill patients. Materials and methods: We conducted a retrospective cohort study with propensity matched analysis including all patients who underwent prolonged mechanical ventilation in the neurocritical Intensive Care Unit. Results: A total of 4030 patients were admitted during the period of interest and 312 entered the final analysis. Propensity score analysis identified 74 matched couples. Length of mechanical ventilation in patients who underwent early nasotracheal intubation resulted to be statistically significantly shorter than patients who underwent orotracheal intubation. Accordingly, length of sedation was significantly lower in patients with nasotracheal intubation, while no difference in complications occurred with similar length of stay. Conclusions: In critical care units using nasotracheal intubation in the standard management of patients, the nasotracheal route was associated with lesser need for sedatives leading to shorter mechanical ventilation in neurocritical patients. However, causality has to be proven by future randomized controlled trials