Critical Care Utilization and Outcomes of Interhospital Medical Transfers at Lower Risk of Death.

PURPOSE: To evaluate utilization and mortality outcomes of interhospital transferred critically-ill medical patients with lower predicted risk of hospital mortality. MATERIALS & METHODS: Multisite retrospective cohort analysis of patients with Acute Physiology and Chronic Health Evaluation (APACHE) IV-a predicted mortality of ≤20% from 335 ICUs in 208 hospitals in the Philips eICU database between 2014-2015. Differences in length-of-stay (LOS) and mortality between transferred and local patients were evaluated using negative binomial logistic regression and logistic regression, respectively. Stratified analyses were conducted for subgroups of predicted mortality: 0%-5%, 6%-10%, 11%-15%, and 16%-20%. RESULTS: Transfers had a higher risk of longer ICU and hospital LOS across all risk strata (IRR 1.12; 95% CI 1.09-1.16, P < 0.001 and IRR 1.11; 95% CI 1.07-1.14, P < 0.001 respectively). Mortality was higher among transfers, largely driven by the 6%-10% mortality risk strata (OR 1.30; 95% CI 1.09-1.54, P = 0.003). CONCLUSIONS: Interhospital transfer of critically-ill medical patients with lower illness severity is associated with higher ICU and hospital utilization and increased mortality. Better understanding of factors driving patient selection for and characteristics of interhospital transfer for this population will have an impact on ICU resource utilization, care efficiency, and hospital quality.

Gender Disparity in Evaluation of Internal Medicine Clerkship Performance.

Importance: Women studying medicine currently equal men in number, but evidence suggests that men and women might not be evaluated equally throughout their education. Objective: To examine whether there are differences associated with gender in either objective or subjective evaluations of medical students in an internal medicine clerkship. Design, Setting, and Participants: This single-center retrospective cohort study evaluated data from 277 third-year medical students completing internal medicine clerkships in the 2017 to 2018 academic year at an academic hospital and its affiliates in Pennsylvania. Data were analyzed from September to November 2020. Exposure: Gender, presumed based on pronouns used in evaluations. Main Outcomes and Measures: Likert scale evaluations of clinical skills, standardized examination scores, and written evaluations were analyzed. Univariate and multivariate linear regression were used to observe trends in measures. Word embeddings were analyzed for narrative evaluations. Results: Analyses of 277 third-year medical students completing an internal medicine clerkship (140 women [51%] with a mean [SD] age of 25.5 [2.3] years and 137 [49%] presumed men with a mean [SD] age of 25.9 [2.7] years) detected no difference in final grade distribution. However, women outperformed men in 5 of 8 domains of clinical performance, including patient interaction (difference, 0.07 [95% CI, 0.04-0.13]), growth mindset (difference, 0.08 [95% CI, 0.01-0.11]), communication (difference, 0.05 [95% CI, 0-0.12]), compassion (difference, 0.125 [95% CI, 0.03-0.11]), and professionalism (difference, 0.07 [95% CI, 0-0.11]). With no difference in examination scores or subjective knowledge evaluation, there was a positive correlation between these variables for both genders (women: r = 0.35; men: r = 0.26) but different elevations for the line of best fit (P < .001). Multivariate regression analyses revealed associations between final grade and patient interaction (women: coefficient, 6.64 [95% CI, 2.16-11.12]; P = .004; men: coefficient, 7.11 [95% CI, 2.94-11.28]; P < .001), subjective knowledge evaluation (women: coefficient, 6.66 [95% CI, 3.87-9.45]; P < .001; men: coefficient, 5.45 [95% CI, 2.43-8.43]; P < .001), reported time spent with the student (women: coefficient, 5.35 [95% CI, 2.62-8.08]; P < .001; men: coefficient, 3.65 [95% CI, 0.83-6.47]; P = .01), and communication (women: coefficient, 6.32 [95% CI, 3.12-9.51]; P < .001; men: coefficient, 4.21 [95% CI, 0.92-7.49]; P = .01). The model based on the men's data also included growth mindset as a significant variable (coefficient, 4.09 [95% CI, 0.67-7.50]; P = .02). For narrative evaluations, words in context with "he or him" and "she or her" differed, with agentic terms used in descriptions of men and personality descriptors used more often for women. Conclusions and Relevance: Despite no difference in final grade, women scored higher than men on various domains of clinical performance, and performance in these domains was associated with evaluators' suggested final grade. The content of narrative evaluations significantly differed by student gender. This work supports the hypothesis that how students are evaluated in clinical clerkships is associated with gender.

Differential Effect of Long-Term Systemic Exposure of TNFα on Health of the Annulus Fibrosus and Nucleus Pulposus of the Intervertebral Disc.

The inflammatory cytokine tumor necrosis factor alpha (TNFα) is considered to play a key role in the pathogenesis of intervertebral disc disease. To evaluate the importance of this cytokine we examined the inflammatory environment and spinal phenotype of 9-month-old human TNFα overexpressing transgenic (hTNFα-TG) mice. The mice evidenced increased circulating levels of interleukin-1ß (IL-1ß), IL-2, keratinocyte chemoattractant/human growth-regulated oncogene (KC/GRO), and monocyte chemoattractant protein-1 (MCP-1) along with thinning of the cortical and trabecular vertebral bone. Surprisingly, although the nucleus pulposus (NP) of these mice was intact and healthy, the caudal annulus fibrosus (AF) evidenced robust cell death and immune cell infiltration. Despite these differences, there were no obvious alterations in the collagen or aggrecan content in the NP and AF. However, there was a reduction in cartilage oligomeric matrix protein (COMP), suggesting destabilization of the AF matrix. Microarray analysis of the NP from hTNFα-TG mice cells revealed minimal changes in global gene expression. These findings lend support to the notion that NP tissue is isolated from systemic inflammation. In contrast, the severe AF phenotype suggests that systemic inflammation interferes with AF health, predisposing discs to herniation as opposed to directly causing NP degeneration. © 2020 American Society for Bone and Mineral Research.

A New Understanding of the Role of IL-1 in Age-Related Intervertebral Disc Degeneration in a Murine Model.

Increased cytokine expression, in particular interleukin-1ß (IL-1ß), is considered a hallmark of intervertebral disc degeneration. However, the causative relationship between IL-1 and age-dependent degeneration has not been established. To investigate the role of IL-1 in driving age-related disc degeneration, we studied the spine phenotype of global IL-1α/ß double knockout (IL-1KO) mice at 12 and 20 months. Multiplex ELISA analysis of blood revealed significant reductions in the concentrations of IFN-γ, IL-5, IL-15, TNF-α, IP-10, and a trend of reduced concentrations of IL-10, macrophage inflammatory protein 1α (MIP-1α), keratinocyte chemoattractant/human growth-regulated oncogene (KC/GRO), and IL-6. However, the circulating level of MIP-2, a neutrophil chemoattractant, was increased in the IL-1KO. The alterations in systemic cytokine levels coincided with altered bone morphology-IL-1KO mice exhibited significantly thicker caudal cortical bone at 12 and 20 months. Despite these systemic inflammatory and bony changes, IL-1 deletion only minimally affected disc health. Both wild-type (WT) and IL-1KO mice showed age-dependent disc degeneration. Unexpectedly, rather than protecting the animals from degeneration, the aging phenotype was more pronounced in IL-1KO animals: knockout mice evidenced significantly more degenerative changes in the annulus fibrosis (AF) together with alterations in collagen type and maturity. At 20 months, there were no changes in nucleus pulposus (NP) extracellular matrix composition or cellular marker expression; however, the IL-1KO NP cells occupied a smaller proportion of the NP compartment that those of WT controls. Taken together, these results show that IL-1 deletion altered the systemic inflammatory environment and vertebral bone morphology. However, instead of protecting discs from age-related disc degeneration, global IL-1 deletion amplified the degenerative phenotype. © 2019 American Society for Bone and Mineral Research.

Transgenic mice overexpressing human TNF-α experience early onset spontaneous intervertebral disc herniation in the absence of overt degeneration.

There is a well-established link between cytokine expression and the progression of intervertebral disc degeneration. Among these cytokines, interleukin-1ß (IL-1ß) and tumor necrosis factor-α (TNF-α) are the most commonly studied. To investigate whether systemic hTNF-α overexpression affects intervertebral disc health, we studied the spine phenotype of Tg197 mice, a widely used hTNF-α transgenic line. These mice were studied at 12-16 weeks of age using comprehensive histochemical and immunohistological analysis of the spinal motion segment. Micro-CT analysis was performed to quantify vertebral trabecular bone architecture. The Tg197 mice evidenced spontaneous annular tears and herniation with increased vascularity in subchondral bone and significant immune cell infiltration. The full-thickness annular tear without nucleus pulposus (NP) extrusion resulted in neutrophil, macrophage, and mast cell infiltration into the disc, whereas the disc with full-thickness tear and pronounced NP herniation showed additional presence of CD4+ and CD8+ T cells. While the observed defects involved failure of the annular, endplate, and vertebral junction, there were no obvious alterations in the collagen or aggrecan content in the NP and annulus fibrosus or the maturity of collagen fibers in Tg197 mice. Despite elevated systemic inflammation and pronounced loss of trabecular bone in the vertebrae, intact Tg197 discs were healthy and showed an increase in NP cell number. The NP cells in intact discs preserved expression of phenotypic markers: CAIII, Glut1, and Krt19. In conclusion, elevated systemic TNF-α increases the susceptibility of mice to spontaneous disc herniation and possibly radiculopathy, without adversely affecting intact intervertebral disc health.

Discovery of the drivers of inflammation induced chronic low back pain: from bacteria to diabetes.

The intervertebral disc is a unique avascular organ that supports axial skeleton flexion and rotation. The high proteoglycan content of the nucleus pulposus tissue, present at the center of the disc, is pivotal for its mechanical function, distribution of compressive loads. Chronic low back pain, a prevalent and costly condition, is strongly associated with disc degeneration. Degenerated discs exhibit high levels of inflammatory cytokines, matrix catabolizing enzymes, and an overall reduction in proteoglycan content. Although the cytokine profile of diseased discs has been widely studied, little is known of what initiates and drives inflammation and subsequent low back pain. Recent studies have shown that anaerobic bacteria are present in a high percentage of painful, herniated discs and long-term treatment with antibiotics resolves symptoms associated with chronic low back pain. It is thought that these anaerobic bacteria in the disc may stimulate inflammation through toll-like receptors to further exacerbate disc degeneration. Despite the promise and novelty of this theory, there are other possible inflammatory mediators that need careful consideration. The metabolic environment associated with diabetes and atypical matrix degradation products also have the ability to activate many of the same inflammatory pathways as seen during microbial infection. It is therefore imperative that the research community must investigate the contribution of all possible drivers of inflammation to address the wide spread problem of discogenic chronic low back pain.

Hypoxic regulation of functional extracellular matrix elaboration by nucleus pulposus cells in long-term agarose culture.

Degeneration of the intervertebral discs is strongly implicated as a cause of low back pain. Since current treatments for discogenic low back pain show poor long-term efficacy, a number of new biological strategies are being pursued. For such therapies to succeed, it is critical that they be validated in conditions that mimic the unique biochemical microenvironment of the nucleus pulposus (NP), which include low oxygen tension. Therefore, the objective of this study was to investigate the effects of oxygen tension on NP cell functional extracellular matrix elaboration in 3D culture. Bovine NP cells were encapsulated in agarose constructs and cultured for 14 or 42 days in either 20% or 2% oxygen in defined media containing transforming growth factor beta-3. At each time point, extracellular matrix composition, biomechanics, and mRNA expression of key phenotypic markers were evaluated. Results showed that while bulk mechanics and composition were largely independent of oxygen level, low oxygen promoted improved restoration of the NP phenotype, higher mRNA expression of extracellular matrix and NP specific markers, and more uniform matrix elaboration. These findings indicate that culture under physiological oxygen levels is an important consideration for successful development of cell and growth factor-based regenerative strategies for the disc.

In vitro characterization of a stem-cell-seeded triple-interpenetrating-network hydrogel for functional regeneration of the nucleus pulposus.

Intervertebral disc degeneration is implicated as a major cause of low-back pain. There is a pressing need for new regenerative therapies for disc degeneration that restore native tissue structure and mechanical function. To that end we investigated the therapeutic potential of an injectable, triple-interpenetrating-network hydrogel comprised of dextran, chitosan, and teleostean, for functional regeneration of the nucleus pulposus (NP) of the intervertebral disc in a series of biomechanical, cytotoxicity, and tissue engineering studies. Biomechanical properties were evaluated as a function of gelation time, with the hydrogel reaching ∼90% of steady-state aggregate modulus within 10 h. Hydrogel mechanical properties evaluated in confined and unconfined compression were comparable to native human NP properties. To confirm containment within the disc under physiological loading, toluidine-blue-labeled hydrogel was injected into human cadaveric spine segments after creation of a nucleotomy defect, and the segments were subjected to 10,000 cycles of loading. Gross analysis demonstrated no implant extrusion, and further, that the hydrogel interdigitated well with native NP. Constructs were next surface-seeded with NP cells and cultured for 14 days, confirming lack of hydrogel cytotoxicity, with the hydrogel maintaining NP cell viability and promoting proliferation. Next, to evaluate the potential of the hydrogel to support cell-mediated matrix production, constructs were seeded with mesenchymal stem cells (MSCs) and cultured under prochondrogenic conditions for up to 42 days. Importantly, the hydrogel maintained MSC viability and promoted proliferation, as evidenced by increasing DNA content with culture duration. MSCs differentiated along a chondrogenic lineage, evidenced by upregulation of aggrecan and collagen II mRNA, and increased GAG and collagen content, and mechanical properties with increasing culture duration. Collectively, these results establish the therapeutic potential of this novel hydrogel for functional regeneration of the NP. Future work will confirm the ability of this hydrogel to normalize the mechanical stability of cadaveric human motion segments, and advance the material toward human translation using preclinical large-animal models.

In vivo retention and bioactivity of IL-1ra microspheres in the rat intervertebral disc: a preliminary investigation.

BACKGROUND: Inflammatory cytokines such as interleukin-1 beta (IL-1ß) contribute to the progression of intervertebral disc degeneration. Previously we demonstrated, in vitro, that by delivering interleukin-1 receptor antagonist (IL-1ra) from poly(lactic co-glycolic acid) (PLGA) microspheres, we could attenuate the degradative effects of IL-1ß on the nucleus pulposus (NP) for up to 20 days. The objective of this study was to undertake a preliminary investigation into whether microspheres could be successfully delivered to and retained in the disc in vivo, and whether IL-1ra released from those microspheres remained biologically active. For retention studies, fluorescently-labeled microspheres were delivered to the NPs of rat caudal discs. Rats were sacrificed at time points up to 56 days, and microspheres were localized using fluorescent microscopy. To investigate whether IL-1ra microspheres could effectively inhibit the effects of IL-1ß in vivo, four disc levels were allocated to the following treatment groups: intact; saline; IL-1ß; or IL-1ß + IL-1ra microspheres. Rats were sacrificed after seven days and NP glycosaminoglycan content was measured. FINDINGS: Microspheres were visible in the disc at all time points up to 28 days, and localized to the NP, the annulus fibrosus (AF), or both. Glycosaminoglycan content for discs injected with IL-1ß alone was significantly lower than for intact controls. For discs injected with IL-1ß along with IL-1ra microspheres, glycosaminoglycan content was not significantly different from intact controls. CONCLUSIONS: Microspheres can successfully be delivered to the disc in vivo and retained for a clinically relevant time frame. IL-1ra released from microspheres can effectively prevent IL-1ß-induced NP glycosaminoglycan loss in vivo.

Needle puncture injury causes acute and long-term mechanical deficiency in a mouse model of intervertebral disc degeneration.

Low back pain is a significant socioeconomic burden and intervertebral disc degeneration has been implicated as a cause. A reliable animal model of disc degeneration is necessary to evaluate therapeutics, and functional metrics are essential to quantify their benefit. To this end, needle puncture injuries were created in the caudal intervertebral discs of mice to induce disc degeneration. Compression, torsion, and creep mechanics were assessed both immediately and after eight weeks to distinguish between the effects of injury and the subsequent reparative or degenerative response. Two needle sizes (29 and 26 gauge) were used to determine injury size-dependence. Compressive stiffness (62%), torsional stiffness (60%), and early damping stiffness (84%) decreased immediately after injury with the large needle (26G). These mechanical properties did not change over time despite structural and compositional changes. At 8 weeks following large needle injury, disc height decreased (37%), nucleus pulposus (NP) glycosaminoglycan content decreased (41%), and NP collagen content increased (45%). The small needle size had no significant effect on mechanics and did not initiate degenerative changes in structure and composition. Thus, the injection of therapeutics into the NP with a minimal needle size may limit damage due to the needle insertion. These findings, along with the wide commercial availability of mouse-specific biological probes, indicate that the mouse caudal disc model can be a powerful tool for investigating disc degeneration and therapy.

Decreased bacteria activity on Si3N4 surfaces compared with PEEK or titanium.

A significant need exists for orthopedic implants that can intrinsically resist bacterial colonization. In this study, three biomaterials that are used in spinal implants--titanium (Ti), polyether-ether-ketone (PEEK), and silicon nitride (Si3N4)--were tested to understand their respective susceptibility to bacterial infection with Staphylococcus epidermidis, Staphlococcus aureus, Pseudomonas aeruginosa, Escherichia coli and Enterococcus. Specifically, the surface chemistry, wettability, and nanostructured topography of respective biomaterials, and the effects on bacterial biofilm formation, colonization, and growth were investigated. Ti and PEEK were received with as-machined surfaces; both materials are hydrophobic, with net negative surface charges. Two surface finishes of Si3N4 were examined: as-fired and polished. In contrast to Ti and PEEK, the surface of Si3N4 is hydrophilic, with a net positive charge. A decreased biofilm formation was found, as well as fewer live bacteria on both the as-fired and polished Si3N4. These differences may reflect differential surface chemistry and surface nanostructure properties between the biomaterials tested. Because protein adsorption on material surfaces affects bacterial adhesion, the adsorption of fibronectin, vitronectin, and laminin on Ti, PEEK, and Si3N4 were also examined. Significantly greater amounts of these proteins adhered to Si3N4 than to Ti or PEEK. The findings of this study suggest that surface properties of biomaterials lead to differential adsorption of physiologic proteins, and that this phenomenon could explain the observed in-vitro differences in bacterial affinity for the respective biomaterials. Intrinsic biomaterial properties as they relate to resistance to bacterial colonization may reflect a novel strategy toward designing future orthopedic implants.

IL-1ra delivered from poly(lactic-co-glycolic acid) microspheres attenuates IL-1ß-mediated degradation of nucleus pulposus in vitro.

INTRODUCTION: Inflammation plays a key role in the progression of intervertebral disc degeneration, a condition strongly implicated as a cause of lower back pain. The objective of this study was to investigate the therapeutic potential of poly(lactic-co-glycolic acid) (PLGA) microspheres loaded with interleukin-1 receptor antagonist (IL-1ra) for sustained attenuation of interleukin-1 beta (IL-1ß) mediated degradative changes in the nucleus pulposus (NP), using an in vitro model. METHODS: IL-1ra was encapsulated in PLGA microspheres and release kinetics were determined over 35 days. NP agarose constructs were cultured to functional maturity and treated with combinations of IL-1ß and media conditioned with IL-1ra released from microspheres at intervals for up to 20 days. Construct mechanical properties, glycosaminoglycan content, nitrite production and mRNA expression of catabolic mediators were compared to properties for untreated constructs using unpaired Student's t-tests. RESULTS: IL-1ra release kinetics were characterized by an initial burst release reducing to a linear release over the first 10 days. IL-1ra released from microspheres attenuated the degradative effects of IL-1ß as defined by mechanical properties, glycosaminoglycans (GAG) content, nitric oxide production and mRNA expression of inflammatory mediators for 7 days, and continued to limit functional degradation for up to 20 days. CONCLUSIONS: In this study, we successfully demonstrated that IL-1ra microspheres can attenuate the degradative effects of IL-1ß on the NP for extended periods. This therapeutic strategy may be appropriate for treating early-stage, cytokine-mediated disc degeneration. Ongoing studies are focusing on testing IL-1ra microspheres in an in vivo model of disc degeneration, as a prelude to clinical translation.

Silver nanoparticle toxicity in Drosophila: size does matter.

BACKGROUND: Consumer nanotechnology is a growing industry. Silver nanoparticles are the most common nanomaterial added to commercially available products, so understanding the influence that size has on toxicity is integral to the safe use of these new products. This study examined the influence of silver particle size on Drosophila egg development by comparing the toxicity of both nanoscale and conventional-sized silver particles. METHODS: The toxicity assays were conducted by exposing Drosophila eggs to particle concentrations ranging from 10 ppm to 100 ppm of silver. Size, chemistry, and agglomeration of the silver particles were evaluated using transmission electron microscopy, X-ray photoelectron spectroscopy, and dynamic light scattering. RESULTS: This analysis confirmed individual silver particle sizes in the ranges of 20-30 nm, 100 nm, and 500-1200 nm, with similar chemistry. Dynamic light scattering and transmission electron microscope data also indicated agglomeration in water, with the transmission electron microscopic images showing individual particles in the correct size range, but the dynamic light scattering z-average sizes of the silver nanoparticles were 782 ± 379 nm for the 20-30 nm silver nanoparticles, 693 ± 114 nm for the 100 nm silver nanoparticles, and 508 ± 32 nm for the 500-1200 nm silver particles. Most importantly, here we show significantly more Drosophila egg toxicity when exposed to larger, nonnanometer silver particles. Upon exposure to silver nanoparticles sized 20-30 nm, Drosophila eggs did not exhibit a statistically significant (P < 0.05) decrease in their likelihood to pupate, but eggs exposed to larger silver particles (500-1200 nm) were 91% ± 18% less likely to pupate. Exposure to silver nanoparticles reduced the percentage of pupae able to emerge as adults. At 10 ppm of silver particle exposure, only 57% ± 48% of the pupae exposed to 20-30 nm silver particles became adults, whereas 89% ± 25% of the control group became adults, and 94% ± 52% and 91% ± 19% of the 500-1200 nm and 100 nm group, respectively, reached adulthood. CONCLUSION: This research provides evidence that nanoscale silver particles (<100 nm) are less toxic to Drosophila eggs than silver particles of conventional (>100 nm) size.