485 research outputs found
Hemodynamic impact of ephedrine on hypotension during general anesthesia : a prospective cohort study on middle-aged and older patients
Background
Ephedrine is a mixed α- and β-agonist vasopressor that is frequently used for the correction of hypotension during general anesthesia. β-responsiveness has been shown to decrease with age; therefore, this study aimed to determine whether aging would reduce the pressor effect of ephedrine on hypotension during general anesthesia.
Methods
Seventy-five patients aged ≥ 45 years were included in this study, with 25 patients allocated to each of the three age groups: 45–64 years, 65–74 years, and ≥ 75 years. All patients received propofol, remifentanil, and rocuronium for the induction of general anesthesia, followed by desflurane and remifentanil. Cardiac output (CO) was estimated using esCCO technology. Ephedrine (0.1 mg/kg) was administered for the correction of hypotension. The primary and secondary outcome measures were changes in the mean arterial pressure (MAP) and CO, respectively, at 5 min after the administration of ephedrine.
Results
The administration of ephedrine significantly increased MAP (p < 0.001, mean difference: 8.34 [95% confidence interval (CI), 5.95–10.75] mmHg) and CO (p < 0.001, mean difference: 7.43 [95% CI, 5.20–9.65] %) across all groups. However, analysis of variance revealed that the degree of elevation of MAP (F [2, 72] = 0.546, p = 0.581, η2 = 0.015 [95% CI, 0.000–0.089]) and CO (F [2, 72] = 2.023, p = 0.140, η2 = 0.053 [95% CI, 0.000–0.162]) did not differ significantly among the groups. Similarly, Spearman’s rank correlation and multiple regression analysis revealed no significant relation between age and the changes in MAP or CO after the administration of ephedrine.
Conclusion
The administration of ephedrine significantly increased MAP and CO; however, no significant correlation with age was observed in patients aged > 45 years. These findings suggest that ephedrine is effective for the correction of hypotension during general anesthesia, even in elderly patients
Rotation in the NGC 1333 IRAS 4C Outflow
We report molecular line observations of the NGC 1333 IRAS 4C outflow in the
Perseus Molecular Cloud with the Atacama Large Millimeter/Submillimeter Array.
The CCH and CS emission reveal an outflow cavity structure with clear
signatures of rotation with respect to the outflow axis. The rotation is
detected from about 120 au up to about 1400 au above the envelope/disk
mid-plane. As the distance to the central source increases, the rotation
velocity of the outflow decreases while the outflow radius increases, which
gives a flat specific angular momentum distribution along the outflow. The mean
specific angular momentum of the outflow is about 100 au km/s. Based on
reasonable assumptions on the outward velocity of the outflow and the protostar
mass, we estimate the range of outflow launching radii to be 5-15 au. Such a
launching radius rules out that this outflow is launched as an X-wind, but
rather, it is more consistent to be a slow disk wind launched from relatively
large radii on the disk. The radius of the centrifugal barrier is roughly
estimated, and the role of the centrifugal barrier in the outflow launching is
discussed.Comment: Accepted to ApJ. 29 pages, 8 figure
The Co-evolution of Disk and Star in Embedded Stages: The Case of the Very Low-mass Protostar
We have observed the CCH (N=3-2, J=7/2-5/2, F=4-3 and 3-2) and SO (6_7-5_6)
emission at a 0"2 angular resolution toward the low-mass Class 0 protostellar
source IRAS 15398-3359 with ALMA. The CCH emission traces the
infalling-rotating envelope near the protostar with the outflow cavity extended
along the northeast-southwest axis. On the other hand, the SO emission has a
compact distribution around the protostar. The CCH emission is relatively weak
at the continuum peak position, while the SO emission has a sharp peak there.
Although the maximum velocity shift of the CCH emission is about 1 km s^-1 from
the systemic velocity, a velocity shift higher than 2 km s^{-1} is seen for the
SO emission. This high velocity component is most likely associated with the
Keplerian rotation around the protostar. The protostellar mass is estimated to
be 0.007^{+0.004}_{-0.003} from the velocity profile of the SO emission. With
this protostellar mass, the velocity structure of the CCH emission can be
explained by the model of the infalling-rotating envelope, where the radius of
the centrifugal barrier is estimated to be 40 au from the comparison with the
model. The disk mass evaluated from the dust continuum emission by assuming the
dust temperature of 20 K-100 K is 0.1-0.9 times the stellar mass, resulting in
the Toomre Q parameter of 0.4-5. Hence, the disk structure may be partly
unstable. All these results suggest that a rotationally-supported disk can be
formed in the earliest stages of the protostellar evolution
Infalling-Rotating Motion and Associated Chemical Change in the Envelope of IRAS 16293-2422 Source A Studied with ALMA
We have analyzed rotational spectral line emission of OCS, CH3OH, HCOOCH3,
and H2CS observed toward the low-mass Class 0 protostellar source IRAS
16293-2422 Source A at a sub-arcsecond resolution (~0".6 x 0".5) with ALMA.
Significant chemical differentiation is found at a 50 AU scale. The OCS line is
found to well trace the infalling-rotating envelope in this source. On the
other hand, the CH3OH and HCOOCH3 distributions are found to be concentrated
around the inner part of the infalling-rotating envelope. With a simple
ballistic model of the infalling-rotating envelope, the radius of the
centrifugal barrier (a half of the centrifugal radius) and the protostellar
mass are evaluated from the OCS data to be from 40 to 60 AU and from 0.5 to 1.0
Msun, respectively, assuming the inclination angle of the envelope/disk
structure to be 60 degrees (90 degrees for the edge-on configuration). Although
the protostellar mass is correlated with the inclination angle, the radius of
the centrifugal barrier is not. This is the first indication of the centrifugal
barrier of the infalling-rotating envelope in a hot corino source. CH3OH and
HCOOCH3 may be liberated from ice mantles due to weak accretion shocks around
the centrifugal barrier, and/or due to protostellar heating. The H2CS emission
seems to come from the disk component inside the centrifugal barrier in
addition to the envelope component. The centrifugal barrier plays a central
role not only in the formation of a rotationally-supported disk but also in the
chemical evolution from the envelope to the protoplanetary disk
Subarcsecond Analysis of Infalling-Rotating Envelope around the Class I Protostar IRAS 04365+2535
Sub-arcsecond images of the rotational line emission of CS and SO have been
obtained toward the Class I protostar IRAS 043652535 in TMC-1A with ALMA. A
compact component around the protostar is clearly detected in the CS and SO
emission. The velocity structure of the compact component of CS reveals
infalling-rotating motion conserving the angular momentum. It is well explained
by a ballistic model of an infalling-rotating envelope with the radius of the
centrifugal barrier (a half of the centrifugal radius) of 50 AU, although the
distribution of the infalling gas is asymmetric around the protostar. The
distribution of SO is mostly concentrated around the radius of the centrifugal
barrier of the simple model. Thus a drastic change in chemical composition of
the gas infalling onto the protostar is found to occur at a 50 AU scale
probably due to accretion shocks, demonstrating that the infalling material is
significantly processed before being delivered into the disk.Comment: 15 March 2016, ApJ, accepte
Synthetic Observations of the Infalling Rotating Envelope: Links between the Physical Structure and Observational Features
We performed synthetic observations of the Ulrich, Cassen, and Moosman (UCM)
model to understand the relation between the physical structures of the
infalling envelope around a protostar and their observational features in
molecular lines, adopting L1527 as an example. We also compared the physical
structure and synthetic position-velocity (P-V) diagrams of the UCM model and a
simple ballistic (SB) model. There are multiple ways to compare synthetic data
with observational data. We first calculated the correlation coefficient. The
UCM model and the SB model show similarly good correlation with the
observational data. While the correlation reflects the overall similarity
between the cube datasets, we can alternatively compare specific local
features, such as the centrifugal barrier in the SB model or the centrifugal
radius in the UCM model. We evaluated systematic uncertainties in these
methods. In the case of L1527, the stellar mass values estimated using these
methods are all lower than the value derived from previous Keplerian analysis
of the disk. This may indicate that the gas infall motion in the envelope is
retarded by, e.g., magnetic fields. We also showed analytically that, in the
UCM model, the spin-up feature of the P-V diagram is due to the infall velocity
rather than the rotation. The line-of-sight velocity is thus , where is the offset. If the infall is retarded, rotational
velocity should dominate so that is proportional to , as is often
observed in the protostellar envelope.Comment: 17 pages, 12 figures, published in ApJ, 2024 January 1
Temperature Structure of the Pipe Nebula Studied by the Intensity Anomaly of the OH 18 cm
We present observations of the four hyperfine structure components of the OH
18 cm transition (1612, 1665, 1667 and 1720 MHz) toward a filamentary dark
cloud, the Pipe nebula, with the Green Bank Telescope. A statistical
equilibrium analysis is applied to the spectra,and the kinetic temperature of a
diffuse molecular gas surrounding dense cores is determined accurately; the
derived temperature ranges from 40 K to 75 K. From this result, we assess the
heating effect on the filamentarystructure of the nebula's "stem" region due to
UV photons from a nearby star -Ophiuchi and a possible
filament-filament collision in the interface of the "stem" and "bowl" regions.
In the stem region, the gas kinetic temperature is found to be almost
independent of the apparent distance from -Ophiuchi: the UV-heating
effect by the star is not visible. On the other hand, the gas kinetic
temperature is raised, as high as 75 K, at the interface of the two
filamentary structures. This result provides us with an additional support to
the filament-filament collision scenario in the Pipe nebula.Comment: 33 pages, 13 figure
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