Preoperative triage to detect SARS-CoV-2 infection in surgical patients: lessons learned for resuming surgery.

PURPOSE: To define the impact of the COVID-19 outbreak on hospital surgical activity and assess the incidence of perioperative COVID-19 within two protocolized screening pathways for elective and non-elective surgery. METHODS: We conducted a prospective cohort study of adults undergoing surgery during the COVID-19 outbreak. The elective pathway included telephone surveys and a quantitative polymerase-chain-reaction test (RT-PCR) only for patients who were asymptomatic and at low risk of infection. Only patients with negative screening underwent surgery. In the non-elective pathway, preoperative screening was performed during the hospital admission. RESULTS: Among 835 patients considered for the elective pathway, 725 had negative RT-PCR results and underwent surgery. This reflects an 83% reduction in surgical activity from 2019. Moreover, 596 patients underwent non-elective surgery, representing a 28% reduction. Preoperatively, 39 patients (6.5%) tested positive for SARS-CoV-2 and underwent surgery through the non-elective pathway, vs. none in the elective pathway (p < 0.001). Postoperatively, 1.4% of elective surgery patients and 2.2% of non-elective surgery patients tested positive (p > 0.05). Mortality was higher in non-elective surgery (0.6% vs. 2.9%, p < 0.001) and in patients with COVID-19 (0% vs. 14%, p < 0.001). CONCLUSIONS: The low incidence of COVID-19 in elective surgeries during the outbreak demonstrates the importance and effectiveness of preoperative screening, combining surveys and RT-PCR.

Gas Sensors Based on Porous Ceramic Bodies of MSnO3 Perovskites (M = Ba, Ca, Zn): Formation and Sensing Properties towards Ethanol, Acetone, and Toluene Vapours.

In this work, the gas-sensing functionality of porous ceramic bodies formed by the slip casting technique was studied using perovskite nanoparticles of an MSnO3 system (M = Ba, Ca, Zn) synthesized by a chemical route. The performance and reliability of the sensitive materials in the presence of different volatile organic compounds (acetone, ethanol, and toluene), and other gases (CO, H2 and NO2) were analysed. The ZnSnO3, BaSnO3, and CaSnO3 sensors showed sensitivities of 40, 16, and 8% ppm-1 towards acetone, ethanol, and toluene vapours, respectively. Good repeatability and selectivity were also observed for these gaseous analytes, as well as excellent stability for a period of 120 days. The shortest response times were recorded for the ZnSnO3 sensors (e.g., 4 s for 80 ppm acetone) with marked responses to low concentrations of acetone (1000 ppb). These results are attributed to the porosity of the sensitive materials, which favours the diffusion of gases, induces surface defects, and provides greater surface area and good sensitivity to acetone, as is seen in the case of ZnSnO3.

Effects on cerebral blood flow of position changes, hyperoxia, CO2 partial pressure variations and the Valsalva manoeuvre: A study in healthy volunteers.

BACKGROUND: Maintaining adequate blood pressure to ensure proper cerebral blood flow (CBF) during surgery is challenging. Induced mild hypotension, sitting position or unavoidable intra-operative circumstances such as haemorrhage, added to variations in carbon dioxide and oxygen tensions, may influence perfusion. Several of these circumstances may coincide and it is unclear how these may affect CBF. OBJECTIVE: To describe the variation in transcranial Doppler and regional cerebral oxygen saturation (rSO2), as a surrogate of CBF, after cardiac preload and gravitational positional changes. DESIGN: Observational study. SETTING: Operating room at Hospital Clínic de Barcelona. VOLUNTEERS: Ten healthy volunteers, white, both sexes. INTERVENTIONS: Measurements were performed in the supine, sitting and standing positions during hyperoxia, hypocapnia and hypercapnia protocols and after a Valsalva manoeuvre. MAIN OUTCOME MEASURES: Cardiac index (CI), haemodynamic and respiratory variables, maximal and mean velocities (Vmax, Vmean) (transcranial Doppler) and rSO2 were acquired. Results were analysed using a generalised estimating equation technique. RESULTS: CI increases more than 16% after a preload challenge were not accompanied by differences in rSO2 or Vmax - Vmean. With positional changes, Vmean decreased more than 7% (P = 0.042) from the supine to the seated position. Hyperoxia induced a cerebral rSO2 increase more than 6% (P = 0.0001) with decreases in Vmax, Vmean and CI values more than 3% (P = 0.001, 0.022 and 0.001) in the supine and standing position. During hypocapnia, CI rose more than 20% from supine to seated and standing (P = 0.0001) with a 4.5% decrease in cerebral rSO2 (P = 0.001) and a decrease of Vmax - Vmean more than 24% in all positions (P = 0.001). Hypercapnia increased cerebral rSO2 more than 17% (P = 0.001), Vmax - Vmean more than 30% (P = 0.001) with no changes in CI. After a Valsalva manoeuvre, rSO2 decreased more than 3% in the right hemisphere in the upright position (P = 0.001). Vmax - Vmean decreased more than 10% (P = 0.001) with no changes in CI. CONCLUSION: CBF changes in response to cerebral vasoconstriction and vasodilatation were detected with rSO2 and transcranial Doppler in healthy volunteers during cardiac preload and in different body positions. Acute hypercapnia had a greater effect on recorded brain parameters than hypocapnia.

ZnO Structures with Surface Nanoscale Interfaces Formed by Au, Fe2O3, or Cu2O Modifier Nanoparticles: Characterization and Gas Sensing Properties.

Zinc oxide rod structures are synthetized and subsequently modified with Au, Fe2O3, or Cu2O to form nanoscale interfaces at the rod surface. X-ray photoelectron spectroscopy corroborates the presence of Fe in the form of oxide-Fe2O3; Cu in the form of two oxides-CuO and Cu2O, with the major presence of Cu2O; and Au in three oxidation states-Au3+, Au+, and Au0, with the content of metallic Au being the highest among the other states. These structures are tested towards nitrogen dioxide, ethanol, acetone, carbon monoxide, and toluene, finding a remarkable increase in the response and sensitivity of the Au-modified ZnO films, especially towards nitrogen dioxide and ethanol. The results for the Au-modified ZnO films report about 47 times higher response to 10 ppm of nitrogen dioxide as compared to the non-modified structures with a sensitivity of 39.96% ppm-1 and a limit of detection of 26 ppb to this gas. These results are attributed to the cumulative effects of several factors, such as the presence of oxygen vacancies, the gas-sensing mechanism influenced by the nano-interfaces formed between ZnO and Au, and the catalytic nature of the Au nanoparticles.

Influence of Mg Doping Levels on the Sensing Properties of SnO2 Films.

This work presents the effect of magnesium (Mg) doping on the sensing properties of tin dioxide (SnO2) thin films. Mg-doped SnO2 films were prepared via a spray pyrolysis method using three doping concentrations (0.8 at.%, 1.2 at.%, and 1.6 at.%) and the sensing responses were obtained at a comparatively low operating temperature (160 °C) compared to other gas sensitive materials in the literature. The morphological, structural and chemical composition analysis of the doped films show local lattice disorders and a proportional decrease in the average crystallite size as the Mg-doping level increases. These results also indicate an excess of Mg (in the samples prepared with 1.6 at.% of magnesium) which causes the formation of a secondary magnesium oxide phase. The films are tested towards three volatile organic compounds (VOCs), including ethanol, acetone, and toluene. The gas sensing tests show an enhancement of the sensing properties to these vapors as the Mg-doping level rises. This improvement is particularly observed for ethanol and, thus, the gas sensing analysis is focused on this analyte. Results to 80 ppm of ethanol, for instance, show that the response of the 1.6 at.% Mg-doped SnO2 film is four times higher and 90 s faster than that of the 0.8 at.% Mg-doped SnO2 film. This enhancement is attributed to the Mg-incorporation into the SnO2 cell and to the formation of MgO within the film. These two factors maximize the electrical resistance change in the gas adsorption stage, and thus, raise ethanol sensitivity.

Love Wave Sensors with Silver Modified Polypyrrole Nanoparticles for VOCs Monitoring.

Love wave sensors with silver-modified polypyrrole nanoparticles are developed in this work. These systems prove functional at room temperature with enhanced response, sensitivity and response time, as compared to other state-of-the-art surface acoustic wave (SAW) sensors, towards volatile organic compounds (VOCs). Results demonstrate the monitoring of hundreds of ppb of compounds such as acetone, ethanol and toluene with low estimated limits of detection (~3 ppb for acetone). These results are attributed to the use of silver-modified polypyrrole as a second guiding/sensitive layer in the Love wave sensor structure, which provides further chemically active sites for the gas-solid interactions. The sensing of low VOCs concentrations by micro sensing elements as those presented here could be beneficial in future systems for air quality control, food quality control or disease diagnosis via exhaled breath as the limits of detection obtained are within those required in these applications.

Portable Low-Cost Electronic Nose Based on Surface Acoustic Wave Sensors for the Detection of BTX Vapors in Air.

A portable electronic nose based on surface acoustic wave (SAW) sensors is proposed in this work to detect toxic chemicals, which have a great potential to threaten the surrounding natural environment or adversely affect the health of people. We want to emphasize that ferrite nanoparticles, decorated (Au, Pt, Pd) and undecorated, have been used as sensitive coatings for the first time in these types of sensors. Furthermore, the proposed electronic nose incorporates signal conditioning and acquisition and transmission modules. The electronic nose was tested to low concentrations of benzene, toluene, and xylene, exhibiting excellent performance in terms of sensitivity, selectivity, and response time, indicating its potential as a monitoring system that can contribute to the detection of toxic compounds.

Acoustic Sensors Based on Amino-Functionalized Nanoparticles to Detect Volatile Organic Solvents.

Love-wave gas sensors based on surface functionalized iron oxide nanoparticles has been developed in this research. Amino-terminated iron oxide nanoparticles were deposited, by a spin coating technique, onto the surface of Love-wave sensors, as a very reproducible gas-sensing layer. The gases tested were organic solvents, such as butanol, isopropanol, toluene and xylene, for a wide and low concentration range, obtaining great responses, fast response times of a few minutes (the time at which the device produced a signal change equal to 90%), good reproducibilities, and different responses for each detected solvent. The estimated limits of detection obtained have been very low for each detected compound, about 1 ppm for butanol, 12 ppm for isopropanol, 3 ppm for toluene and 0.5 ppm for xylene. Therefore, it is demonstrated that this type of acoustic wave sensor, with surface amino-functionalized nanoparticles, is a good alternative to those ones functionalized with metal nanoparticles, which result very expensive sensors to achieve worse results.

Experience with "Fast track" postoperative care after deep brain stimulation surgery.

BACKGROUND: A 24-h-stay in the post-anesthesia care unit (PACU) is a common postoperative procedure after deep brain stimulation surgery (DBS). OBJECTIVE: We evaluated the impact of a fast-track (FT) postoperative care protocol. METHODS: An analysis was performed on all patients who underwent DBS in 2 periods: 2006, overnight monitored care (OMC group), and 2007-2013, FT care (FT group). RESULTS: The study included 19 patients in OMC and 95 patients in FT. Intraoperative complications occurred in 26.3% patients in OMC vs. 35.8% in FT. Post-operatively, one patient in OMC developed hemiparesis, and agitation in 2 patients. In FT, two patients with intraoperative hemiparesis were transferred to the ICU. While on the ward, 3 patients from the FT developed hemiparesis, two of them 48h after the procedure. Thirty eight percent of FT had an MRI scan, while the remaining 62% and all patients of OMC had a CT-scan performed on their transfer to the ward. One patient in OMC had a subthalamic hematoma. Two patients in FT had a pallidal hematoma, and 3 a bleeding along the electrode. CONCLUSIONS: A FT discharge protocol is a safe postoperative care after DBS. There are a small percentage of complications after DBS, which mainly occur within the first 6h.

[Diagnostic yield and postoperative management of patients submitted to brain biopsy in a university hospital]. / Eficacia diagnóstica y manejo posoperatorio de los pacientes sometidos a biopsia cerebral en un hospital universitario.

OBJECTIVE: To assess the diagnostic yield and the incidence of perioperative complications in patients undergoing an open or closed cerebral biopsy and to determine the length of intensive care monitoring, for early diagnosis and fast management of perioperative complications. MATERIAL AND METHOD: This was a retrospective analysis of all the patients that underwent brain biopsy between January 2006 and July 2012. We recorded demographic data, comorbidities, modality of biopsy, intraoperative clinical data, histological results, computed tomography scanning findings and occurrence, and type of perioperative complications and moment of appearance. RESULTS: Seventy-six brain biopsies in 75 consecutive patients (51 closed and 25 open) were analysed. Diagnostic yield was 98% for closed biopsies and 96% for open biopsies. Mortality related to the procedures was 3.9 and 4%, respectively. The incidence of major complications was 3.9% for closed biopsies and 8% for open biopsies; half of these appeared within the first 24 postoperative hours, during patient stay in the Intensive Care Unit. Age was the only risk factor for complications (P=.04) in our study. No differences in morbimortality were found between the studied groups. CONCLUSIONS: Diagnostic yield was very high in our series. Because the importance of early diagnosis of complications for preventing long-term sequelae, we recommend overnight hospital stay for observation after open or closed brain biopsy.

Relationship between intraoperative regional cerebral oxygen saturation trends and cognitive decline after total knee replacement: a post-hoc analysis.

BACKGROUND: Bilateral regional brain oxygen saturation (rSO2) trends, reflecting intraoperative brain oxygen imbalance, could warn of brain dysfunction. Various types of cognitive impairment, such as memory decline, alterations in executive function or subjective complaints, have been described three months after surgery. Our aim was to explore the potential utility of rSO2 values as a warning sign for the development of different types of decline in postoperative psychological function. METHODS: Observational post-hoc analysis of data for the patient sample (n = 125) of a previously conducted clinical trial in patients over the age of 65 years undergoing total knee replacement under spinal anesthesia. Demographic, hemodynamic and bilateral rSO2 intraoperative values were recorded. An absolute rSO2 value of <50% or a reduction of >20% or >25% below baseline were chosen as relevant cutoffs. Composite function test scores were created from baseline to three months for each patient and adjusted for the mean (SD) score changes for a control group (n = 55). Tests were used to assess visual-motor coordination and executive function (VM-EF) (Wechsler Digit Symbol-Coding and Visual Reproduction, Trail Making Test) and memory (Auditory Verbal Learning, Wechsler Memory Scale); scales were used to assess psychological symptoms. RESULTS: We observed no differences in baseline rSO2 values; rSO2 decreased significantly in all patients during surgery (P < 0.0001). Seventy-five patients (60%) had no sign of cognitive decline or psychological symptoms. Twenty-one patients (16.8%) had memory decline, 3 (2.4%) had VM-EF decline, and 33 (26.4%) had psychological symptoms. Left and right rSO2 values were asymmetric in patients who had memory decline (mean [SD] left-right ratio of 95.03 [8.51] vs 101.29 [6.7] for patients with no changes, P = 0.0012). The mean right-left difference in rSO2 was also significant in these patients (-2.87% [4.73%], lower on the right, P = 0.0034). CONCLUSIONS: Detection of a trend to asymmetry in rSO2 values can warn of possible postoperative onset of memory decline. Psychological symptoms and memory decline were common three months after knee replacement in our patients over the age of 65 years.

Love-wave sensors combined with microfluidics for fast detection of biological warfare agents.

The following paper examines a time-efficient method for detecting biological warfare agents (BWAs). The method is based on a system of a Love-wave immunosensor combined with a microfluidic chip which detects BWA samples in a dynamic mode. In this way a continuous flow-through of the sample is created, promoting the reaction between antigen and antibody and allowing a fast detection of the BWAs. In order to prove this method, static and dynamic modes have been simulated and different concentrations of BWA simulants have been tested with two immunoreactions: phage M13 has been detected using the mouse monoclonal antibody anti-M13 (AM13), and the rabbit immunoglobulin (Rabbit IgG) has been detected using the polyclonal antibody goat anti-rabbit (GAR). Finally, different concentrations of each BWA simulants have been detected with a fast response time and a desirable level of discrimination among them has been achieved.

Nanocrystalline tin oxide nanofibers deposited by a novel focused electrospinning method. Application to the detection of TATP precursors.

A new method of depositing tin dioxide nanofibers in order to develop chemical sensors is presented. It involves an electrospinning process with in-plane electrostatic focusing over micromechanized substrates. It is a fast and reproducible method. After an annealing process, which can be performed by the substrate heaters, it is observed that the fibers are intertwined forming porous networks that are randomly distributed on the substrate. The fiber diameters oscillate from 100 nm to 200 nm and fiber lengths reach several tens of microns. Each fiber has a polycrystalline structure with multiple nano-grains. The sensors have been tested for the detection of acetone and hydrogen peroxide (precursors of the explosive triacetone triperoxide, TATP) in air in the ppm range. High and fast responses to these gases have been obtained.

Craniotomy in sitting position: anesthesiology management.

PURPOSE OF REVIEW: Sitting position to surgically approach posterior fossa disorder continues to be the first choice for some neurosurgical teams. We underwent a literature research for recent published studies involving neurosurgical patients operated on in this position. Preoperative evaluation, anesthetic technique, intraoperative monitoring, detection and treatment of venous or arterial air embolism episodes, and all the reported complications were recorded. RECENT FINDINGS: A modified semisitting (lounging) position aiming to create a positive pressure in the transverse and sigmoid sinuses, with lower head and higher legs positioned above the top of the head, decreases the incidence and severity of venous air embolism. Hyperventilation, compromising cerebral blood flow, has to be avoided during a sitting position. Precordial Doppler or transesophageal echocardiography monitoring improves the detection of small venous air embolism enabling its early treatment and diminishing its consequences. Patients with known patent foramen ovale can be operated on in a sitting position, under strict protocol, with few reported clinical venous air embolism and no paradoxical air embolism. SUMMARY: Sitting position for neurosurgical procedures may be a well tolerated approach for the patient if neurosurgeons and neuroanesthesiologists undergo a strict team protocol, including all necessary monitoring and meticulously followed.

[Detection of venous air embolism and patent foramen ovale in neurosurgery patients in sitting position]. / Detección de embolismo aéreo venoso y de foramen oval permeable en pacientes neuroquirúrgicos intervenidos en posición de sedestación.

INTRODUCTION: Early detection of venous air embolism (VAE) during neurosurgical procedures in sitting position decreases the severity of its complications. OBJECTIVES: our aim was to analyse the detection of VAE and its impact on patients operated in a sitting position, verify air aspiration through a central venous catheter and assess the feasibility of the routine use of transcranial Doppler (TCD) for intraoperative diagnosis of patent foramen ovale (PFO). MATERIAL AND METHODS: We performed a prospective study of consecutive neurosurgical procedures performed in the sitting position for 5 years. Precordial Doppler and end-tidal carbon dioxide were the diagnostic methods for VAE. PFO was explored by TCD after anaesthetic induction. RESULTS: 136 patients were operated in the sitting position, 93 craniotomies and 43 cervical spine procedures. Twenty-two patients (16.2%) were diagnosed with VAE (21.5% of craniotomies and 4.7% of spinal surgeries; p=.013). In 59% of cases, air was aspirated through the central venous catheter. There was haemodynamic involvement in 3 patients, impaired oxygenation in 4 and clinically relevant pneumocephalus in 5 of them. Two patients (1.4%) were diagnosed with PFO, but did not present episodes of VAE or paradoxical air embolism. CONCLUSIONS: The series analysed confirmed a higher incidence of VAE in craniotomies than in cervical spine surgery in a sitting position. We were able to aspirate air through the central venous catheter in more than half the cases. No patients suffered critical intraoperative complications following our approach. The low incidence of PFO detected with TCD will imply a modification of our protocol performed on anaesthetised patients.

Nanoscale, surface-confined phase separation by electron beam induced oxidation.

Electron-assisted oxidation of Co-Si-based focused electron beam induced deposition (FEBID) materials is shown to form a 2-4 nm metal oxide surface layer on top of an electrically insulating silicon oxide layer less than 10 nm thick. Differences between thermal and electron-induced oxidation on the resulting microstructure are illustrated.

Gas-Phase Synthesis of Iron Silicide Nanostructures Using a Single-Source Precursor: Comparing Direct-Write Processing and Thermal Conversion.

The investigation of precursor classes for the fabrication of nanostructures is of specific interest for maskless fabrication and direct nanoprinting. In this study, the differences in material composition depending on the employed process are illustrated for focused-ion-beam- and focused-electron-beam-induced deposition (FIBID/FEBID) and compared to the thermal decomposition in chemical vapor deposition (CVD). This article reports on specific differences in the deposit composition and microstructure when the (H3Si)2Fe(CO)4 precursor is converted into an inorganic material. Maximum metal/metalloid contents of up to 90 at. % are obtained in FIBID deposits and higher than 90 at. % in CVD films, while FEBID with the same precursor provides material containing less than 45 at. % total metal/metalloid content. Moreover, the Fe:Si ratio is retained well in FEBID and CVD processes, but FIBID using Ga+ ions liberates more than 50% of the initial Si provided by the precursor. This suggests that precursors for FIBID processes targeting binary materials should include multiple bonding such as bridging positions for nonmetals. In addition, an in situ method for investigations of supporting thermal effects of precursor fragmentation during the direct-writing processes is presented, and the applicability of the precursor for nanoscale 3D FEBID writing is demonstrated.

Association between preoperative serum lactate concentrate with tumor cell proliferative index in primary brain tumor.

BACKGROUND: Elevated preoperative lactate levels have been reported in patients admitted for resection of brain tumors. As histologic type and tumor grade have also been linked to lactate concentration, we hypothesized that preoperative lactate concentration in patients with brain tumors may be associated with tumor proliferation. We describe the relationship between preoperative plasma lactate levels, and the cell proliferation marker Ki-67 in brain tumor surgery. METHODS: In this cross-sectional study, records of patients who underwent craniotomy between June 2017 and February 2018 at our Hospital were reviewed to select glioma and meningioma cases in which lactate concentrations in plasma and degree of cell proliferation were registered. Bivariable and linear regression analyses were used to assess the association between lactate concentrations and the Ki-67 Index. RESULTS: Lactate concentrations in plasma and Ki-67 Index were available in 55 patients. Meningioma cases had a mean concentration of 1.2 (0.1) mmol/L compared to diffuse astrocytic and oligodendroglial tumors cases with 1.7 (0.1) mmol/L (P<0.01). Both variables had a low positive correlation in meningiomas (Spearman's r, 0.29; 95% CI, -0.10-0.61; P=0.13) and a high correlation in gliomas (Spearman's r, 0.64; 95% CI, 0.33-0.82; P<0.01). The pooled analysis showed a high correlation index (Spearman's r, 0.61; 95% CI, 0.40-0.76; P<0.01). A linear regression model showed that the Ki-67 Index explained 43% of the variation in lactate (P<0.01). CONCLUSIONS: Brain tumors with higher rates of cell proliferation have higher plasma lactate levels. In this scenario, lactate concentrations may not only reflect systemic perfusion.

Towards the development of an epitope-focused vaccine for SARS-CoV-2.

The rapid spread of COVID-19 on all continents and the mortality induced by SARS-CoV-2 virus, the cause of the pandemic coronavirus disease 2019 (COVID-19) has motivated an unprecedented effort for vaccine development. Inactivated viruses as well as vaccines focused on the partial or total sequence of the Spike protein using different novel platforms such us RNA, DNA, proteins, and non-replicating viral vectors have been developed. The high global need for vaccines, now and in the future, and the emergence of new variants of concern still requires development of accessible vaccines that can be adapted according to the most prevalent variants in the respective regions. Here, we describe the immunogenic properties of a group of theoretically predicted RBD peptides to be used as the first step towards the development of an effective, safe and low-cost epitope-focused vaccine. One of the tested peptides named P5, proved to be safe and immunogenic. Subcutaneous administration of the peptide, formulated with alumina, induced high levels of specific IgG antibodies in mice and hamsters, as well as an increase of IFN-γ expression by CD8+ T cells in C57 and BALB/c mice upon in vitro stimulation with P5. Neutralizing titers of anti-P5 antibodies, however, were disappointingly low, a deficiency that we will attempt to resolve by the inclusion of additional immunogenic epitopes to P5. The safety and immunogenicity data reported in this study support the use of this peptide as a starting point for the design of an epitope restricted vaccine.