Attenuated hypocholesterolemia following severe trauma signals risk for late ventilator-associated pneumonia, ventilator dependency, and death: a retrospective study of consecutive patients

<p>Abstract</p> <p>Background</p> <p>Post-traumatic ventilator-associated pneumonia (VAP) is a substantial clinical problem that increases hospital costs and typically adds to the duration of mechanical ventilation. We evaluated the impact of VAP on ventilator days. We also assessed 48-hour total blood cholesterol (TC) and other potential risk factors for the development of VAP.</p> <p>Methods</p> <p>We performed a retrospective study of consecutive trauma patients requiring emergency tracheal intubation and evaluated TC, age, gender, ethanol status, smoker status, injury mechanism, chest injury, brain injury, Injury Severity Score (ISS), shock, day-one hypoxemia, and RBC transfusion as potential risks for VAP.</p> <p>Results</p> <p>The 152 patients had ISS 28.1, brain injury 68.4%, VAP 50.0%, ventilator days 14.3, and death 9.9%. Ventilator days were increased with late VAP (p < 0.0001). TC was 110.7 mg/dL with expected TC 197.5 mg/dL. TC was lower with chest injury, shock, and RBC transfusion but, higher with brain injury (p ≤ 0.01). TC decreased as ISS increased (p = 0.01). However, one patient subset (ISS ≥ 20-&-TC ≥ 90 mg/dL) had a relative increase in TC despite an increase in ISS. ISS ≥ 20-&-TC ≥ 90 mg/dL, but not ISS alone, was the only independent predictor of late VAP (OR 3.0; p = 0.002). ISS ≥ 20-&-TC ≥ 90 mg/dL and day-one hypoxemia were the only independent predictors for increased ventilator days (p = 0.01). ISS ≥ 20-&-TC ≥ 90 mg/dL, but not ISS alone, was the only predictor of death (OR 3.8; p = 0.03).</p> <p>Conclusions</p> <p>Severe traumatic injury produced substantial hypocholesterolemia that is greater with chest injury, shock, and RBC transfusion, but less with brain injury. Total blood cholesterol tended to decrease with increasing injury severity. However, attenuated hypocholesterolemia (ISS ≥ 20-&-TC ≥ 90 mg/dL) represents a unique response that can occur with critical injury. Attenuated hypocholesterolemia signals early risk for late VAP, ventilator dependency, and death.</p

Following severe injury, hypocholesterolemia improves with convalescence but persists with organ failure or onset of infection

INTRODUCTION: Our primary objective was to determine the impact of traumatic injury, onset of infection, organ/metabolic dysfunction, and mortality on serum cholesterol. METHODS: During 676 surgical intensive care unit (SICU) days, 28 ventilated trauma patients underwent daily measurement of white blood cell (WBC) count and differential, cholesterol, arterial oxygen tension/fractional inspired oxygen, bilirubin, glucose, creatinine, and bicarbonate. With the onset of infection, WBC response was considered positive if the WBC count was 16.0 or greater, immature neutrophils were 10% or greater, or WBC count increased by 20%. Cholesterol response was considered positive if cholesterol decreased or failed to increase by 10%. RESULTS: Injury Severity Score was 30.6 ± 8.6 and there were 48 infections. Initial cholesterol was decreased (119 ± 44 mg/dl) compared with expected values from a database (201 ± 17 mg/dl; P < 0.0001). The 25 survivors had higher cholesterol at SICU discharge (143 ± 35 mg/dl) relative to admission (112 ± 37 mg/dl; P < 0.0001). In the three patients who died, the admission cholesterol was 175 ± 62 mg/dl and the cholesterol at death was 117 ± 27 mg/dl. The change in percentage of expected cholesterol (observed value divided by expected value) from admission to discharge was different for patients surviving (16 ± 19%) and dying (-29 ± 19%; P = 0.0005). With onset of infection, the WBC response was positive in 61% and cholesterol response was positive in 91% (P = 0.001). Percentage of expected cholesterol was decreased with each system dysfunction: arterial oxygen tension/fractional inspired oxygen < 350, creatinine > 2.0 mg/dl, glucose > 120 mg/dl, bilirubin > 2.5 mg/dl, and bicarbonate ≥ 28 or ≤ 23 (P < 0.01). Percentage of expected cholesterol decreased as the number of dysfunctions increased (P = 0.0001). CONCLUSION: Hypocholesterolemia is seen following severe injury. Convalescing patients (ready for SICU discharge) have improved cholesterol levels, whereas dying patients appear to have progressive hypocholesterolemia. Decreasing or fixed cholesterol levels suggest the development of infection or organ/metabolic dysfunction. Cholesterol responses are more sensitive for the onset of infection than are WBC responses. Sequential cholesterol monitoring is recommended for patients with severe trauma

Can Protostellar Outflows Set Stellar Masses?

The opening angles of some protostellar outflows appear too narrow to match the expected core-star mass efficiency SFE = 0.3-0.5 if outflow cavity volume traces outflow mass, with a conical shape and a maximum opening angle near 90 deg. However, outflow cavities with paraboloidal shape and wider angles are more consistent with observed estimates of the SFE. This paper presents a model of infall and outflow evolution based on these properties. The initial state is a truncated singular isothermal sphere which has mass $\approx$1 $M_\odot$, free fall time $\approx$80 kyr, and small fractions of magnetic, rotational, and turbulent energy. The core collapses pressure-free as its protostar and disk launch a paraboloidal wide-angle wind. The cavity walls expand radially and entrain envelope gas into the outflow. The model matches SFE values when the outflow mass increases faster than the protostar mass by a factor 1 - 2, yielding protostar masses typical of the IMF. It matches observed outflow angles if the outflow mass increases at nearly the same rate as the cavity volume. The predicted outflow angles are then typically $\sim$50 deg as they increase rapidly through the stage 0 duration of $\sim$40 kyr. They increase more slowly up to $\sim$110 deg during their stage I duration of $\sim$70 kyr. With these outflow rates and shapes, model predictions appear consistent with observational estimates of typical stellar masses, SFEs, stage durations, and outflow angles, with no need for external mechanisms of core dispersal.Comment: Accepted for publication by The Astrophysical Journal; 47 pages, 10 figure

The Spitzer c2d Survey of Nearby Dense Cores. IX. Discovery of a Very Low Luminosity Object Driving a Molecular Outflow in the Dense Core L673-7

We present new infrared, submillimeter, and millimeter observations of the dense core L673-7 and report the discovery of a low-luminosity, embedded Class 0 protostar driving a molecular outflow. L673-7 is seen in absorption against the mid-infrared background in 5.8, 8, and 24 micron Spitzer images, allowing for a derivation of the column density profile and total enclosed mass of L673-7, independent of dust temperature assumptions. Estimates of the core mass from these absorption profiles range from 0.2-4.5 solar masses. Millimeter continuum emission indicates a mass of about 2 solar masses, both from a direct calculation assuming isothermal dust and from dust radiative transfer models constrained by the millimeter observations. We use dust radiative transfer models to constrain the internal luminosity of L673-7, defined to be the luminosity of the central source and excluding the luminosity from external heating, to be 0.01-0.045 solar luminosities, with 0.04 solar luminosities the most likely value. L673-7 is thus classified as a very low luminosity object (VeLLO), and is among the lowest luminosity VeLLOs yet studied. We calculate the kinematic and dynamic properties of the molecular outflow in the standard manner, and we show that the expected accretion luminosity based on these outflow properties is greater than or equal to 0.36 solar luminosities. The discrepancy between this expected accretion luminosity and the internal luminosity derived from dust radiative transfer models indicates that the current accretion rate is much lower than the average rate over the lifetime of the outflow. Although the protostar embedded within L673-7 is consistent with currently being substellar, it is unlikely to remain as such given the substantial mass reservoir remaining in the core.Comment: 19 pages, 14 figures. Accepted by Ap

The Spitzer c2d Survey Of Nearby Dense Cores. X. Star Formation In L673 And Cb188

L673 and CB188 are two low-mass clouds isolated from large star-forming regions that were observed as part of the Spitzer Legacy Project "From Molecular Clouds to Planet Forming disks" (c2d). We identified and characterized all the young stellar objects (YSOs) of these two regions and modeled their spectral energy distributions (SEDs) to examine whether their physical properties are consistent with values predicted from the theoretical models and with the YSO properties in the c2d survey of larger clouds. Overall, 30 YSO candidates were identified by the c2d photometric criteria, 27 in L673 and 3 in CB188. We confirm the YSO nature of 29 of them and remove a false Class III candidate in L673. We further present the discovery of two new YSO candidates, one Class 0 and another possible Class I candidate in L673, therefore bringing the total number of YSO candidates to 31. Multiple sites of star formation are present within L673, closely resembling other well-studied c2d clouds containing small groups such as B59 and L1251B, whereas CB188 seems to consist of only one isolated globule-like core. We measure a star formation efficiency (SFE) of 4.6%, which resembles the SFE of the larger c2d clouds. From the SED modeling of our YSO sample we obtain envelope masses for Class I and Flat spectrum sources of 0.01-1.0 M-circle dot. The majority of Class II YSOs show disk accretion rates from 3.3 x 10(-10) to 3 x 10(-8) M-circle dot yr(-1) and disk masses that peak at 10(-4) to 10(-3) M-circle dot. Finally, we examined the possibility of thermal fragmentation in L673 as the main star-forming process. We find that the mean density of the regions where significant YSO clustering occurs is of the order of similar to 10(5) cm(-3) using 850 mu m observations and measure a Jeans Length that is greater than the near-neighbor YSO separations by approximately a factor of 3-4. We therefore suggest that other processes, such as turbulence and shock waves, may have had a significant effect on the cloud's filamentary structure and YSO clustering.University of SouthamptonNASA 1279198, 1288806, 1365763Jet Propulsion Laboratory, California Institute of TechnologyAstronom

ALMA Cycle 1 Observations of the HH46/47 Molecular Outflow: Structure, Entrainment and Core Impact

We present ALMA Cycle 1 observations of the HH46/47 molecular outflow using combined 12m array and ACA observations. The improved angular resolution and sensitivity of our multi-line maps reveal structures that help us study the entrainment process in much more detail and allow us to obtain more precise estimates of outflow properties than previous observations. We use 13CO(1-0) and C18O(1-0) emission to correct for the 12CO(1-0) optical depth to accurately estimate the outflow mass, momentum and kinetic energy. This correction increases the estimates of the mass, momentum and kinetic energy by factors of about 9, 5 and 2, respectively, with respect to estimates assuming optically thin emission. The new 13CO and C18O data also allow us to trace denser and slower outflow material than that traced by the 12CO maps, and they reveal an outflow cavity wall at very low velocities (as low as 0.2km/s with respect to the cores central velocity). Adding with the slower material traced only by 13CO and C18O, there is another factor of 3 increase in the mass estimate and 50% increase in the momentum estimate. The estimated outflow properties indicate that the outflow is capable of dispersing the parent core within the typical lifetime of the embedded phase of a low-mass protostar, and that it is responsible for a core-to-star efficiency of 1/4 to 1/3. We find that the outflow cavity wall is composed of multiple shells associated with a series of jet bow-shock events. Within about 3000AU of the protostar the 13CO and C18O emission trace a circumstellar envelope with both rotation and infall motions, which we compare with a simple analytic model. The CS(2-1) emission reveals tentative evidence of a slowly-moving rotating outflow, which we suggest is entrained not only poloidally but also toroidally by a disk wind that is launched from relatively large radii from the source.Comment: Accepted for publication in ApJ. 26 pages, 20 figure

An extremely high velocity molecular jet surrounded by an ionized cavity in the protostellar source Serpens SMM1

We report ALMA observations of a one-sided, high-velocity ($\sim$80 km s$^{-1}$) CO($J = 2 \rightarrow 1$) jet powered by the intermediate-mass protostellar source Serpens SMM1-a. The highly collimated molecular jet is flanked at the base by a wide-angle cavity; the walls of the cavity can be seen in both 4 cm free-free emission detected by the VLA and 1.3 mm thermal dust emission detected by ALMA. This is the first time that ionization of an outflow cavity has been directly detected via free-free emission in a very young, embedded Class 0 protostellar source that is still powering a molecular jet. The cavity walls are ionized either by UV photons escaping from the accreting protostellar source, or by the precessing molecular jet impacting the walls. These observations suggest that ionized outflow cavities may be common in Class 0 protostellar sources, shedding further light on the radiation, outflow, and jet environments in the youngest, most embedded forming stars.Comment: 6 pages, 4 figures, accepted for publication in the Astrophysical Journal Letter