We hypothesized that different phases of intraoperative hypotension should be differentiated because of different underlying causative mechanisms. We defined post-induction hypotension (PIH; i.e. ...arterial hypotension occurring during the first 20 min after anaesthesia induction) and early intraoperative hypotension (eIOH; i.e. arterial hypotension during the first 30 min of surgery).
In this retrospective study, we included 2037 adult patients who underwent general anaesthesia. Arterial hypotension was defined as a systolic arterial blood pressure (SAP) <90 mm Hg or a need for norepinephrine infusion at > 6 µg min−1 at least once during the phases of PIH and eIOH. Multivariate logistic regression analysis was used to test for association of clinical factors with PIH and eIOH.
Independent variables significantly related to PIH were pre-induction SAP odds ratio (OR) 0.97 (95% confidence interval 0.97–0.98), age OR 1.03 (1.02–1.04), and emergency surgery OR 1.75 (1.20–2.56); P<0.01 each. Pre-induction SAP OR 0.99 (0.98–0.99), P<0.01, age OR 1.02 (1.02–1.03), P<0.01, emergency surgery OR 1.83 (1.28–2.62), P<0.01, supplementary administration of spinal or epidural anaesthetic techniques OR 3.57 (2.41–5.29), P<0.01, male sex OR 1.41 (1.12–1.79), P<0.01, and ASA physical status IV OR 2.18 (1.19–3.99), P=0.01 were significantly related to eIOH.
We identified clinical factors associated with PIH and eIOH. The use of these factors to estimate the risk of PIH and eIOH might allow the avoidance or timely treatment of hypotensive episodes during general anaesthesia.
The determination of blood flow, i.e. cardiac output, is an integral part of haemodynamic monitoring. This is a review on noninvasive continuous cardiac output monitoring in perioperative and ...intensive care medicine. We present the underlying principles and validation data of the following technologies: thoracic electrical bioimpedance, thoracic bioreactance, vascular unloading technique, pulse wave transit time, and radial artery applanation tonometry. According to clinical studies, these technologies are capable of providing cardiac output readings noninvasively and continuously. They, therefore, might prove to be innovative tools for the assessment of advanced haemodynamic variables at the bedside. However, for most technologies there are conflicting data regarding the measurement performance in comparison with reference methods for cardiac output assessment. In addition, each of the reviewed technology has its own limitations regarding applicability in the clinical setting. In validation studies comparing cardiac output measurements using these noninvasive technologies in comparison with a criterion standard method, it is crucial to correctly apply statistical methods for the assessment of a technology's accuracy, precision, and trending capability. Uniform definitions for ‘clinically acceptable agreement’ between innovative noninvasive cardiac output monitoring systems and criterion standard methods are currently missing. Further research must aim to further develop the different technologies for noninvasive continuous cardiac output determination with regard to signal recording, signal processing, and clinical applicability.
Context. The NASA Origins, Spectral Interpretation, Resource Identification, and Security–Regolith Explorer (OSIRIS-REx) mission has obtained thousands of spectra of asteroid (101955) Bennu with the ...OSIRIS-REx Visible and InfraRed Spectrometer (OVIRS).
Aims. We present a spectral search for minor absorption bands and determine compositional variations on the surface of Bennu.
Methods. Reflectance spectra with low and high spatial resolutions were analyzed for evidence of weak absorption bands. Spectra were also divided by a global average spectrum to isolate unique spectral features, and variations in the strongest band depths were mapped on a surface shape model. The global visible to near-IR spectrum of Bennu shows evidence of several weak absorption bands with depths of a few percent.
Results. Several observed bands are consistent with phyllosilicates, and their distribution correlates with the stronger 2.74-μm hydration band. A 0.55-μm band is consistent with iron and is deepest in the spectrally reddest areas on Bennu. The presence of hydrated phyllosilicates and iron oxides indicates substantial aqueous alteration in Bennu’s past.
Conclusions. Bennu’s spectra are not identical to a limited set of carbonaceous chondrite spectra, possibly due to compositional properties and spatial scale differences; however, returned samples should contain a mixture of common chondrite materials.
The composition of asteroids and their connection to meteorites provide insight into geologic processes that occurred in the early Solar System. We present spectra of the Nightingale crater region on ...near-Earth asteroid Bennu with a distinct infrared absorption around 3.4 micrometers. Corresponding images of boulders show centimeters-thick, roughly meter-long bright veins. We interpret the veins as being composed of carbonates, similar to those found in aqueously altered carbonaceous chondrite meteorites. If the veins on Bennu are carbonates, fluid flow and hydrothermal deposition on Bennu's parent body would have occurred on kilometer scales for thousands to millions of years. This suggests large-scale, open-system hydrothermal alteration of carbonaceous asteroids in the early Solar System.
Contact.
The NASA New Frontiers asteroid sample return mission Origins, Spectral Interpretation, Resource Identification, and Security–Regolith Explorer (OSIRIS-REx) has provided a large amount of ...data on the asteroid (101955) Bennu, including high-quality spectra obtained by the OSIRIS-REx Visible and InfraRed Spectrometer (OVIRS).
Aims.
To better constrain the surface properties and compositional variations of Bennu, we studied the visible and near-infrared spectral behavior across the asteroid surface by means of a statistical analysis aiming to distinguish spectrally distinct groups, if present.
Methods.
We applied the
G
-mode multivariate statistical analysis to the near-infrared OVIRS spectra to obtain an automatic statistical clustering at different confidence levels.
Results.
The statistical analysis highlights spectral variations on the surface of Bennu. Five distinct spectral groups are identified at a 2
σ
confidence level. At a higher confidence level of 3
σ
, no grouping is observed.
Conclusions.
The results at a 2
σ
confidence level distinguish a dominant spectral behavior group (group 1, background) and four small groups showing spectral slope variations, associated with areas with different surface properties. The background group contains most of the analyzed data, which implies a globally homogeneous surface at the spectral and spatial resolution of the data. The small groups with redder spectra are concentrated around the equatorial ridge and are associated with morphological surface features such as specific craters and boulders. No significant variation is detected in the band area or depth of the 2.74
μ
m band, which is associated with hydrated phyllosilicate content. The spectral slope variations are interpreted as a consequence of different regolith particle sizes, and/or porosity, and/or space weathering, that is, the presence of more or less fresh material. The OSIRIS-REx mission primary sampling site, Nightingale, and a boulder known as the Roc, are redder than the background surface.
The OSIRIS-REx Visible and Infrared Spectrometer (OVIRS) is a point spectrometer covering the spectral range of 0.4 to 4.3 microns (25,000-2300 cm−1). Its primary purpose is to map the surface ...composition of the asteroid Bennu, the target asteroid of the OSIRIS-REx asteroid sample return mission. The information it returns will help guide the selection of the sample site. It will also provide global context for the sample and high spatial resolution spectra that can be related to spatially unresolved terrestrial observations of asteroids. It is a compact, low-mass (17.8 kg), power efficient (8.8 W average), and robust instrument with the sensitivity needed to detect a 5% spectral absorption feature on a very dark surface (3% reflectance) in the inner solar system (0.89-1.35 AU). It, in combination with the other instruments on the OSIRIS-REx Mission, will provide an unprecedented view of an asteroid's surface.
The deep eutectic solvent glyceline formed by choline chloride and glycerol in 1:2 molar ratio is much less viscous compared to glycerol, which facilitates its use in many applications where high ...viscosity is undesirable. Despite the large difference in viscosity, we have found that the structural network of glyceline is completely defined by its glycerol constituent, which exhibits complex microscopic dynamic behavior, as expected from a highly correlated hydrogen-bonding network. Choline ions occupy interstitial voids in the glycerol network and show little structural or dynamic correlations with glycerol molecules. Despite the known higher long-range diffusivity of the smaller glycerol species in glyceline, in applications where localized dynamics is essential (e.g., in microporous media), the local transport and dynamic properties must be dominated by the relatively loosely bound choline ions.
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