An economic appraisal of lower extremity bypass graft maintenance

AbstractObjective: Infrainguinal graft surveillance leads to intervention on the basis of duplex-identified stenoses. We have become increasingly concerned about the high frequency with which such revisions are required to maximize graft patency and limb salvage rates. The economic implications of these procedures have not been carefully analyzed or justified. Methods: We retrospectively reviewed 155 consecutive autogenous infrainguinal bypass grafts performed for chronic leg ischemia in 141 patients. All patients were enrolled in a prospective surveillance program using color flow duplex imaging. Full economic appraisal (cost analysis, cost-effect analysis, and cost-benefit analysis) was performed for all graft surveillance and limb salvage–related interventions through use of standard accounting and valuation techniques. Results: Mean follow-up was 27 months. Five-year assisted primary patency (72%) and limb salvage rates (91%) were calculated by means of life table analysis. A total of 61 grafts required 86 revisions. Within 1 year of implantation, 36% of the grafts required revision. During this first year, the mean cost per graft enrolled was $9417. Time intervals after the initial year demonstrated a reduced annual revision rate (6$1725 per graft). The mean 5-year cost of graft maintenance ($16,318) approached that of the initial bypass graft ($19,331). The sum of the initial cost of bypass graft and 5-year graft maintenance cost ($35,649) was similar to the cost of amputation ($36,273). Grafts revised for duplex-detected stenoses (n = 46), in comparison with those revised after thrombosis (n = 15), had an improved 1-year patency (93% vs 57%; P <.01), required fewer amputations (2% vs 33%; P <.01), less frequently required multiple graft revisions (P =.06), and generated fewer expenses (at 12 months after revision, $17,688 vs$45,252, P <.01). Conclusion: The cost associated with graft maintenance is significant, particularly within the first year, and demands consideration. Revision of a duplex-identified stenosis was significantly less costly than revision after graft thrombosis. Compared with the cost of limb amputation, limb salvage–related expenses appear to be justified. (J Vasc Surg 2000;32:1-12.

The correlation of early flow disturbances with the development of infrainguinal graft stenosis: A 10-year study of 341 autogenous vein grafts

AbstractPurpose: Although duplex surveillance of infrainguinal bypass grafts is widely accepted, the optimal frequency and intensity of graft surveillance remains controversial. Earlier reports have suggested that grafts can be stratified into high-risk and low-risk groups based on the presence or absence of early graft flow disturbances. The purpose of this study was to provide long-term data in determining whether early graft flow disturbances detected by means of duplex scanning can predict the development of intrinsic vein graft stenosis. Methods: We reviewed a series of patients undergoing prospective duplex graft surveillance after autogenous infrainguinal bypass grafting procedures from 1987 to 1997. Patients included in the study underwent at least one duplex scan within 3 months of graft implantation and were observed for a minimum of 6 months. Grafts were categorized as abnormal when a focal flow disturbance with a peak systolic velocity greater than 150 cm/s was identified within 3 months of graft implantation. Results: Of 341 vein grafts in 296 patients who met inclusion criteria, 89 grafts (26%) required revision for intrinsic stenosis; the mean follow-up period was 35 months (range, 6 months to 10 years). Early flow disturbances were detected in 84 (25%) grafts. Grafts with early flow disturbances were more likely to ultimately require revision (43% vs 21%; P = .0001) and required initial revision earlier (8 months vs 16 months; P = .019). Eighty-two percent of initial graft revisions occurred in the first 2 postoperative years; 69% occurred in the first year. However, an annual 2% to 4% incidence of late-appearing graft stenosis persisted during long-term follow-up. An additional 24 patients (7% of grafts) required an inflow or outflow reconstruction. Conclusion: Grafts with early postoperative flow disturbances detected by means of duplex scanning have nearly three times the incidence of graft-threatening stenosis and an earlier requirement for revision, when compared with normal grafts. This suggests that the biology and etiology of these lesions may differ. These data support not only aggressive efforts to detect early graft lesions to stratify grafts at highest risk, but also continued lifelong graft surveillance to detect late-appearing lesions, inflow and outflow disease progression, and maximize graft patency. (J Vasc Surg 1999;30:8-15.

Coordination of photosynthetic traits across soil and climate gradients

"Least-cost theory" posits that C3 plants should balance rates of photosynthetic water loss and carboxylation in relation to the relative acquisition and maintenance costs of resources required for these activities. Here we investigated the dependency of photosynthetic traits on climate and soil properties using a new Australia-wide trait dataset spanning 528 species from 67 sites. We tested the hypotheses that plants on relatively cold or dry sites, or on relatively more fertile sites, would typically operate at greater CO2 drawdown (lower ratio of leaf internal to ambient CO2 , Ci :Ca ) during light-saturated photosynthesis, and at higher leaf N per area (Narea ) and higher carboxylation capacity (Vcmax 25 ) for a given rate of stomatal conductance to water vapour, gsw . These results would be indicative of plants having relatively higher water costs than nutrient costs. In general, our hypotheses were supported. Soil total phosphorus (P) concentration and (more weakly) soil pH exerted positive effects on the Narea -gsw and Vcmax 25 -gsw slopes, and negative effects on Ci :Ca . The P effect strengthened when the effect of climate was removed via partial regression. We observed similar trends with increasing soil cation exchange capacity and clay content, which affect soil nutrient availability, and found that soil properties explained similar amounts of variation in the focal traits as climate did. Although climate typically explained more trait variation than soil did, together they explained up to 52% of variation in the slope relationships and soil properties explained up to 30% of the variation in individual traits. Soils influenced photosynthetic traits as well as their coordination. In particular, the influence of soil P likely reflects the Australia's geologically ancient low-relief landscapes with highly leached soils. Least-cost theory provides a valuable framework for understanding trade-offs between resource costs and use in plants, including limiting soil nutrients

Surgical Treatment of Carotid Body Paragangliomas: Outcomes and Complications According to the Shamblin Classification

OBJECTIVES: The objective of this study was to review our experience in the surgical management of carotid body paragangliomas and evaluate the outcomes and complications according to the Shamblin classification. METHODS: Thirteen patients who had been diagnosed and surgically treated for carotid body tumors (CBTs) were enrolled in this study. We reviewed patient demographics, radiographic findings, and surgical outcomes collected from medical records. RESULTS: Fifteen CBTs were found in 13 patients and 13 tumors were resected. Selective preoperative tumor embolization was performed on six patients. The median blood loss, operation time, and hospital stay for these patients were not significantly reduced compared to those without embolization. The median tumor size was 2.3 cm in Shamblin I and II and 4 cm in Shamblin III. The median intraoperative blood loss was 280 mL and 700 mL, respectively (P<0.05). Internal carotid artery ligation with reconstruction was accomplished on three patients (23%), and they all belonged to Shamblin III (38%). One Shamblin III patient (8%) developed transient cerebral ischemia, and postoperative stroke with death occurred in another Shamblin III patient. Postoperative permanent cranial nerve deficit occurred in three patients (23%) who were all in Shamblin III (P=0.03). There were no recurrences or delayed complications at the median follow up of 29 months. CONCLUSION: Shamblin III had a high risk of postoperative neurovascular complications. Therefore, early detection and prompt surgical resection of CBTs will decrease surgical morbidity.ope

Hawai‘i Forest Review: Synthesizing the Ecology, Evolution, and Conservation of a Model System

As the most remote archipelago in the world, the Hawaiian Islands are home to a highly endemic and disharmonic biota that has fascinated biologists for centuries. Forests are the dominant terrestrial biome in Hawai‘i, spanning complex, heterogeneous climates across substrates that vary tremendously in age, soil structure, and nutrient availability. Species richness is low in Hawaiian forests compared to other tropical forests, as a consequence of dispersal limitation from continents and adaptive radiations in only some lineages, and forests are dominated by the widespread Metrosideros species complex. Low species richness provides a relatively tractable model system for studies of community assembly, local adaptation, and species interactions. Moreover, Hawaiian forests provide insights into predicted patterns of evolution on islands, revealing that while some evidence supports “island syndromes,” there are exceptions to them all. For example, Hawaiian plants are not as a whole less defended against herbivores, less dispersible, more conservative in resource use, or more slow-growing than their continental relatives. Clearly, more work is needed to understand the drivers, sources, and constraints on phenotypic variation among Hawaiian species, including both widespread and rare species, and to understand the role of this variation for ecological and evolutionary processes, which will further contribute to conservation of this unique biota. Today, Hawaiian forests are among the most threatened globally. Resource management failures – the proliferation of non-native species in particular – have led to devastating declines in native taxa and resulted in dominance by novel species assemblages. Conservation and restoration of Hawaiian forests now rely on managing threats including climate change, ongoing species introductions, novel pathogens, lost mutualists, and altered ecosystem dynamics through the use of diverse tools and strategies grounded in basic ecological, evolutionary, and biocultural principles. The future of Hawaiian forests thus depends on the synthesis of ecological and evolutionary research, which will continue to inform future conservation and restoration practices

Temporal Network Based Analysis of Cell Specific Vein Graft Transcriptome Defines Key Pathways and Hub Genes in Implantation Injury

Vein graft failure occurs between 1 and 6 months after implantation due to obstructive intimal hyperplasia, related in part to implantation injury. The cell-specific and temporal response of the transcriptome to vein graft implantation injury was determined by transcriptional profiling of laser capture microdissected endothelial cells (EC) and medial smooth muscle cells (SMC) from canine vein grafts, 2 hours (H) to 30 days (D) following surgery. Our results demonstrate a robust genomic response beginning at 2 H, peaking at 12–24 H, declining by 7 D, and resolving by 30 D. Gene ontology and pathway analyses of differentially expressed genes indicated that implantation injury affects inflammatory and immune responses, apoptosis, mitosis, and extracellular matrix reorganization in both cell types. Through backpropagation an integrated network was built, starting with genes differentially expressed at 30 D, followed by adding upstream interactive genes from each prior time-point. This identified significant enrichment of IL-6, IL-8, NF-κB, dendritic cell maturation, glucocorticoid receptor, and Triggering Receptor Expressed on Myeloid Cells (TREM-1) signaling, as well as PPARα activation pathways in graft EC and SMC. Interactive network-based analyses identified IL-6, IL-8, IL-1α, and Insulin Receptor (INSR) as focus hub genes within these pathways. Real-time PCR was used for the validation of two of these genes: IL-6 and IL-8, in addition to Collagen 11A1 (COL11A1), a cornerstone of the backpropagation. In conclusion, these results establish causality relationships clarifying the pathogenesis of vein graft implantation injury, and identifying novel targets for its prevention

Flipping the College Course: A Case Study

A Family Studies & Human Development (FSHD) 377 Adolescence course was flipped for the first time in the Spring 2015 semester with the goal of attaining better student learning experiences, learning outcomes, as well as peer dynamics. Flipping was done based on the Team-Based Learning approach. Seventy-nine students were enrolled. Assigned individual student work was completed outside of class. Students met in class, once a week, with their 3-4 person teams. Class generally followed this pattern: time for questions or mini lecture (when time allowed), individual post-test, group post-test, and an in-class activity. Other assignments included a group movie paper and weekly online discussion posts. The final section of the course featured guest lecturers focusing on psychosocial issues in adolescence. Students were surveyed at four times throughout the semester. In general, flipping seems to have included more perceived negatives than benefits. As expected, it was met with much student resistance. This included a lack of individual preparation, poor "student buy-in", and a great student preference for lecture. Student final course grades for Spring 2015 (flipped course) were higher, on average, than those of Spring 2014 (traditional lecture). The four questionnaires and coding of results are included in the appendices

Plasticity and Ontogeny in Dynamic Environments: A Case Study of Two Neotropical Understory Herbs

For understory plants in tropical forests, light strongly influences rates of growth, survival, and reproduction, i.e., vital rates. To better understand how light availability influences the vital rates of two co-occurring understory herbs, Calathea crotalifera and Heliconia tortuosa, I monitored their growth, survival, and reproduction in forest plots. Plant size influenced the effect of light on vital rates, and increasing light did not always increase vital rates. Both species grew at small sizes but shrank at larger sizes, and larger individuals were more sensitive to changes in light than small individuals. I also found evidence of tradeoffs among vital rates, which were influenced by the interaction between plant size and light. These results support the hypothesis that life stage (ontogeny) influences the ability to capture and utilize light, and reveal that high light may negatively influence the demographic performance of plants that are adapted to deep shade. To better understand how the ability to capture and utilize light influences growth, I estimated photosynthetic light responses for individuals in the forest plots and used model averaging to determine the importance of size, light, and photosynthetic responses for estimating future size. I found minor differences between the species in their photosynthetic traits, but found significant differences in the importance of size, light, and physiology on growth. Calathea that diminished in size had one of two combinations of photosynthetic efficiency and respiratory costs, either higher respiratory costs coupled with lower photosynthetic efficiency, or, higher efficiency coupled with maximum photosynthetic capacity compared to individuals that increased in size. Heliconia that diminished in size also had different combinations, lower respiratory costs coupled with photosynthetic capacity or lower efficiency, coupled with lower respiration, and lower photosynthetic capacity than individuals that increased in size. These results do not support the hypothesis that that shade tolerant species should have high efficiency but low respiration and low photosynthetic capacity and therefore they indicate differences in mechanisms and degrees of shade tolerance among species. I used a shadehouse experiment to determine whether demographic traits and functional traits were positively influenced by variability in light, light availability during the seedling stage, and soil moisture. I measured growth, survival, leaf lifespan, photosynthetic capacity, and biomass allocation of Heliconia and Calathea over two years. Plants in a variable light environment had greater growth than those in a constant light environment when moisture was low. At low moisture, a variable light environment increased growth when individuals started in low light and had no influence on growth when individuals started in high light. At high moisture, a constant light environment increased growth whether individuals started in low or high light. Survival decreased with increasing environmental variability but more so at high moisture. Photosynthetic capacity decreased for individuals in a variable light environment, when they had lived in high light as seedlings, but was unaffected by environmental variability when they had lived in low light as seedlings. Calathea had a significantly greater proportion of its total biomass aboveground than Heliconia. Leaf lifespan was unaffected by the treatments. Thus, although these species inhabit highly heterogeneous and variable light environments, these results do not support the hypothesis that environmental variability positively influences demographic and functional traits. Instead they reveal that environmental variability may be stressful even for plants found in intrinsically heterogeneous environments. They may have low plasticity, i.e., a low capacity to acclimate. To determine the effects of static and dynamic light environments on population growth rates, I used Integral Projection Models. Growth was modeled as a function of plant size, maximum photosynthetic capacity (Amax), and light, and all other vital rates were modeled as functions of plant size and light. I estimated the population growth rates for both species over a range of light levels and Amax values. Finally, I evaluated three types of elasticity (proportional sensitivity) of the population growth rate for three levels of Amax: perturbations in the mean and variance of vital rates (ES), increased variance of vital rates (ESσ), environment-specific perturbations of vital rates (ESβ). The latter are especially of interest as it addresses the relative impact on overall fitness of events that occur in different light environments, in other words the potential strength of selection of events that occur in high light vs shady environments. Adaptation to shady environments means a higher impact of events that occur in the shade on fitness whereas adaptation to high light environments means a higher impact of events that occur in high light on fitness. As light availability increased, the population growth rate (λ) increased for Calathea but shrank for Heliconia, and increasing Amax had no effect on λ for Calathea but increased λ for Heliconia in low light. As Amax increased, the population growth rate in a dynamic light environment (λS) increased for Heliconia, but not Calathea. These results suggest that Calathea is more strongly adapted to shade than Heliconia and indicates that increasing the ability to use light has a direct positive influence on population growth, and therefore fitness. Photosynthetic capacity (Amax ) had an impact on how sensitive the population growth rate was to changes in life history rates for Heliconia, but not Calathea. Calathea λS was most sensitive to perturbations in intermediate-sized individuals under high light, and changing Amax had little effect on this relationship. When light availability was low, elasticities were more widely distributed among the size classes, but λS was much more sensitive to seeds and seedlings. In contrast, Heliconia λS was sensitive to intermediate- and large-sized individuals when light availability was low, and became much more sensitive to seeds and seedlings as light availability increased. Changing Amax had much more of an effect on elasticity of Heliconia when light was abundant than when light was scarce. These results demonstrate that photosynthetic physiology can have large consequences for the population dynamics of plants in both static and dynamic light environments, and that the effect of light on population dynamics is influenced by photosynthetic rates. In conclusion, I found that increasing light and increasing the capacity to use light does not always improve demographic performance for plants adapted to living in the shade. Plant size interacts with light availability to influence rates of growth, survival, and reproduction. Growth is in turn influenced by different combinations of physiological responses for my study species. I found that the effect of light variability is influenced by soil moisture and early life conditions. Finally, population growth rates, an indicator of fitness, are significantly influenced by photosynthetic capacity for one species but not the other, and reflect differences in the ability to use light. The broader impact of this study is that physiological responses can be used to predict the fates of species in temporally variable environments.</p

Persisting Dreams: The Impact of the Doctoral Socialization Process on Latina Post-Doctoral Career Aspirations

Latinas are underrepresented within the professorate and within doctoral programs, particularly within Research Intensive Institutions. This dissertation explores how the doctoral socialization process impacts the pipeline from the Ph.D. to scholarly careers for Latinas in Research universities. Given the low numbers of representation and production at the doctoral level for Latinas, what happens when they do enter Ph.D. programs? Their doctoral experience must be marked in one way or another by their identities as women of color in institutions where they are the overwhelming minority. More significantly, how does their doctoral experience groom them to become future faculty members in the academy? In this dissertation, I examine the doctoral experiences for Latinas and how their educational experiences impact their post-doctoral career aspirations and career trajectories