Association of Early Beta-Blocker Exposure and Functional Outcomes in Critically Ill Patients With Moderate to Severe Traumatic Brain Injury: A Transforming Clinical Research and Knowledge in Traumatic Brain Injury Study

OBJECTIVES

We aimed to 1) describe patterns of beta-blocker utilization among critically ill patients following moderate-severe traumatic brain injury (TBI) and 2) examine the association of early beta-blocker exposure with functional and clinical outcomes following injury.

DESIGN

Retrospective cohort study.

SETTING

ICUs at 18 level I, U.S. trauma centers in the Transforming Clinical Research and Knowledge in TBI (TRACK-TBI) study.

PATIENTS

Greater than or equal to 17 years enrolled in the TRACK-TBI study with moderate-severe TBI (Glasgow Coma Scale of <13) were admitted to the ICU after a blunt TBI.

INTERVENTIONS

None.

MEASUREMENTS

Primary exposure was a beta blocker during the first 7 days in the ICU, with a primary outcome of 6-month Glasgow Outcome Scale-Extended (GOSE). Secondary outcomes included: length of hospital stay, in-hospital mortality, 6-month and 12-month mortality, 12-month GOSE score, and 6-month and 12-month measures of disability, well-being, quality of life, and life satisfaction.

MAIN RESULTS

Of the 450 eligible participants, 57 (13%) received early beta blockers (BB+ group). The BB+ group was on average older, more likely to be on a preinjury beta blocker, and more likely to have a history of hypertension. In the BB+ group, 34 participants (60%) received metoprolol only, 19 participants (33%) received propranolol only, 3 participants (5%) received both, and 1 participant (2%) received atenolol only. In multivariable regression, there was no difference in the odds of a higher GOSE score at 6 months between the BB+ group and BB- group (odds ratio = 0.86; 95% CI, 0.48-1.53). There was no association between BB exposure and secondary outcomes.

CONCLUSIONS

About one-sixth of subjects in our study received early beta blockers, and within this group, dose, and timing of beta-blocker administration varied substantially. No significant differences in GOSE score at 6 months were demonstrated, although our ability to draw conclusions is limited by overall low total doses administered compared with prior studies.

Polarized secretory trafficking directs cargo for asymmetric dendrite growth and morphogenesis

Proper growth of dendrites is critical to the formation of neuronal circuits, but the cellular machinery that directs the addition of membrane components to generate dendritic architecture remains obscure. Here, we demonstrate that post-Golgi membrane trafficking is polarized toward longer dendrites of hippocampal pyramidal neurons in vitro and toward apical dendrites in vivo. Small Golgi outposts partition selectively into longer dendrites and are excluded from axons. In dendrites, Golgi outposts concentrate at branchpoints where they engage in post-Golgi trafficking. Within the cell body, the Golgi apparatus orients toward the longest dendrite, and this Golgi polarity precedes asymmetric dendrite growth. Manipulations that selectively block post-Golgi trafficking halt dendrite growth in developing neurons and cause a shrinkage of dendrites in mature pyramidal neurons. Further, disruption of Golgi polarity produces neurons with symmetric dendritic arbors lacking a single longest principal dendrite. These results define a novel polarized organization of neuronal secretory trafficking and demonstrate a mechanistic link between directed membrane trafficking and asymmetric dendrite growth.

Room-temperature preparation and characterization of poly (ethylene glycol)-coated silica nanoparticles for biomedical applications

Monodisperse, spherical, polyethylene glycol (PEG)-coated silica nanoparticles have been prepared at room temperature and characterized for the purpose of biomedical applications. The particles were synthesized by the hydrolysis of tetramethyl orthosilicate (TMOS) in alcohol media under catalysis by ammonia, and their size can range from about 50-350 nm in diameter. We studied the particle size and size distribution using a scanning electron microscope (SEM) and an asymmetric field-flow fractionation (AFFF) multiangle static light-scattering instrument. The chemical and/or physical binding of PEG to the silica nanoparticles was studied by infrared spectroscopy, and the weight percentage of PEG attached to the particles was quantified. The PEG-coated silica nanoparticles showed enhanced colloidal stability when redispersed into aqueous solutions from the dried state as a result of the steric stabilization function of the PEG polymer grafted on the surface of particles. A nonspecific protein-binding test was also carried out to show that the PEG coating can help reduce the protein adsorption onto the surface of the particles, relating to the biocompatibility of these PEG-coated particles. Also, the inclusion of magnetic nanoparticles into the silica particles was shown as an example of the possible applications of PEG-coated silica particles. These silica nanoparticles, as a matrix for encapsulation of certain reagents, have potential for applications to in vivo diagnosis, analysis, and measurements inside intact biologic systems.