Implementation of a Vascular Acute Care Surgery Model is Associated with Improved Surgeon Efficiency and Two-Year Mortality After Lower Extremity Intervention.

OBJECTIVE: Vascular surgeons work long, unpredictable hours with repeated exposure to high-stress situations. Inspired by general surgery acute care surgery models, we sought to organize the care of vascular emergencies with the implementation of a vascular acute care surgery (VACS) model. Within this model, a surgeon is in-house without elective cases and assigned for consultations and urgent operative cases on a weekly basis. This study examined the impact of a VACS model on postoperative mortality and surgeon efficiency. METHODS: This was a retrospective cohort analysis of institutional Vascular Quality Initiative data from July 2014 - July 2023. Patients undergoing lower extremity bypass, peripheral vascular intervention, or amputation were included. There was a washout period from January 2020 - January 2022 to account for COVID-19 pandemic practice abnormalities. Patients were separated into pre- or post-VACS groups. The primary clinical outcomes were 30-day and 2-year mortality. Secondary clinical outcomes included 30-day complications and 30-day and 1-year major adverse limb events (MALE). Separate analyses of operating room data from July 2017 - February 2024 and fiscal data from fiscal year 2019 - fiscal year 2024 were conducted. A washout period from January 2020 - January 2022 was applied. Efficiency outcomes included monthly relative value units (RVUs) per clinical fraction full-time equivalent (cFTE) and daytime (0730-1700, Monday-Friday) operating room minutes. Patient factors and operative efficiency were compared using appropriate statistical tests. Regression modeling was performed for the primary outcomes. RESULTS: There were 972 and 257 patients in the pre- and post-VACS groups, respectively. Pre-VACS patients were younger (66.8±12.0 vs 68.7±12.7 years, p=0.03) with higher rates of coronary artery disease (34.6% vs 14.8%, p<0.01), hypertension (88.4% vs 82.2%, p=0.01), and tobacco history (84.4% vs 78.2%, p=0.02). 30-day mortality (2.4% pre- vs 0.8% post-VACS, p=0.18) and Kaplan-Meier estimation of 2-year mortality remained stable after VACS (p=0.07). VACS implementation was not associated with 30-day mortality but was associated with lower 2-year mortality hazard on multivariable Cox regression (hazard ratio: 0.5, 95% confidence interval: 0.3-0.9, p=0.01). Operative efficiency improved post-VACS (850.0 [765.7, 916.3] vs 918.0 [881.0, 951.1] RVU/cFTE-month, median [inter-quartile range], p=0.03). Daytime operating minutes increased (469.1±287.5 vs 908.2±386.2 minutes, p<0.01), while non-daytime minutes (420.0 [266.0, 654.0] vs 469.5 [242.0, 738.3] minutes, p=0.40) and weekend minutes (129.0 [0.0, 298.0] vs 113.5 [0.0, 279.5] minutes, p=0.59) remained stable. CONCLUSIONS: A VACS model leads to improvement in surgeon operative efficiency while maintaining patient safety. The adoption of a vascular acute care model has a positive impact on the delivery of comprehensive vascular care.

Implementation of a vascular acute care surgery service model is associated with decreased surgeon burnout.

OBJECTIVE: Vascular surgeons have one of the highest rates of burnout among surgical specialties, often attributed to high patient acuity and clinical workload. Acute Care Surgery models are a potential solution used among general and trauma surgeons. METHODS: This is a retrospective analysis of prospectively collected Accreditation Council for Graduate Medical Education survey results from faculty and residents before and after implementation of a vascular Acute Care Surgery (VACS) model. The VACS model assigns a weekly rotation of an attending surgeon with no elective cases or clinic responsibilities and a monthly rotating resident team. Residents and attendings are in-house to cover all urgent and emergent vascular daytime consultations and procedures, whereas nights and weekend coverage remain a typical rotating schedule. Survey question results were binned into domains consistent with the Maslach Burnout Inventory. RESULTS: Both residents and faculty reported an increase in median scores in Maslach Burnout Inventory domains of emotional exhaustion (Faculty: 2.9 vs 3.4; P < .001; Residents: 3.1 vs 3.6; P < .001) and faculty reported higher personal accomplishment scores (Faculty: 3.3 vs 3.8; P = .005) after the VACS model implementation. CONCLUSIONS: A VACS model is a tangible practice change that can address a major problem for current vascular surgeons, as it is associated with decreased burnout for faculty and residents through improvement in both emotional exhaustion and personal accomplishment. Improved longitudinal assessment of resident and faculty burnout is needed and future work should identify specific practice patterns related to decreased burnout.

Direct Observation of Enhanced Electron-Phonon Coupling in Copper Nanoparticles in the Warm-Dense Matter Regime.

Warm dense matter (WDM) represents a highly excited state that lies at the intersection of solids, plasmas, and liquids and that cannot be described by equilibrium theories. The transient nature of this state when created in a laboratory, as well as the difficulties in probing the strongly coupled interactions between the electrons and the ions, make it challenging to develop a complete understanding of matter in this regime. In this work, by exciting isolated ∼8 nm copper nanoparticles with a femtosecond laser below the ablation threshold, we create uniformly excited WDM. Using photoelectron spectroscopy, we measure the instantaneous electron temperature and extract the electron-ion coupling of the nanoparticle as it undergoes a solid-to-WDM phase transition. By comparing with state-of-the-art theories, we confirm that the superheated nanoparticles lie at the boundary between hot solids and plasmas, with associated strong electron-ion coupling. This is evidenced both by a fast energy loss of electrons to ions, and a strong modulation of the electron temperature induced by strong acoustic breathing modes that change the nanoparticle volume. This work demonstrates a new route for experimental exploration of the exotic properties of WDM.

Telehealth During COVID-19 for Adults with Multiple Chronic Conditions: Associations with Self-Reported Food Insecurity and with Physical Limitations.

Background: Adults with chronic medical conditions complicated by food insecurity or physical limitations may have higher barriers to accessing telehealth implemented during the COVID-19 pandemic. Objective: To examine the relationships of self-reported food insecurity and physical limitations with changes in health care utilization and medication adherence comparing the year before (March 2019-February 2020) and the first year of the COVID-19 pandemic (April 2020-March 2021) among patients with chronic conditions insured by Medicaid or Medicare Advantage. Methods: A prospective cohort study of 10,452 Kaiser Permanente Northern California members insured by Medicaid and 52,890 Kaiser Permanente Colorado members insured by Medicare Advantage was conducted. Difference-in-differences (DID) between the pre-COVID and COVID years in telehealth versus in-person health care utilization and adherence to chronic disease medicines by food insecurity and by physical limitation status were measured. Results: Food insecurity and physical limitations were each associated with small but significantly greater shifts from in-person to telehealth. Medicare Advantage members with physical limitations also had significantly greater decline in adherence to chronic medications from year to year compared with those without physical limitations (DID from pre-COVID year to COVID year ranged from 0.7% to 3.6% greater decline by medication class, p < 0.01). Conclusions: Food insecurity and physical limitations did not present significant barriers to the transition to telehealth during the COVID pandemic. The greater decrease in medication adherence among older patients with physical limitations suggests that care systems must further address the needs of this high-risk population.

Long-term anticoagulation is associated with type II endoleaks and failure of sac regression after endovascular aneurysm repair.

OBJECTIVE: Within the context of endovascular aneurysm repair (EVAR), the role of anticoagulation therapy on endoleak development and subsequent reintervention is unclear with conflicting data in the literature. The hypothesis of this study is that long-term anticoagulation is associated with persistent type II endoleaks and failure of sac regression in patients undergoing endoluminal repair of intact infrarenal aortic aneurysm. METHODS: Retrospective cohort abstracted from the Vascular Quality Initiative index hospitalization and long-term follow-up datasets for EVAR (2003-2017) were included in the analysis. Patients not taking aspirin preoperatively and postoperatively were excluded. Patients taking anticoagulation and aspirin concomitantly (treatment) after the index procedure were compared against patients taking aspirin alone (control). Anticoagulation included warfarin and novel oral anticoagulants, including factor Xa inhibitors and direct thrombin inhibitors. One-to-one greedy matching using propensity scores was implemented to match patients. The primary end points were failure of aneurysm sac regression, sac expansion, risk of endoleak, and reintervention rate for endoleak at follow-up. Sac regression was defined as a decrease of at least 5 mm and sac expansion was defined as an increase of at least 5 mm. RESULTS: There were 9004 patients who received ASA alone and 332 patients who received ASA and anticoagulation. Propensity scores were used to create 301 matching pairs to account for differences in baseline characteristics and comorbidities, including but not limited to age, sex, smoking, coronary artery disease, heart failure, and chronic kidney disease between the treatment and control groups. After adjusting for covariables anticoagulation use was independently associated with a significantly decreased abdominal aortic aneurysm sac regression (41.59% vs 58.41%; P = .001), but no statistically significant difference in sac expansion with long-term anticoagulation use (9.7% vs 4.9%; P = .056). There was increased risk of type II endoleaks (11.96% vs 6.31%; P = .023; relative risk, 1.89; 95% confidence interval, 1.11-3.23; P = .016), but no significant differences in type I, III, or indeterminate endoleaks. There was no statistical difference in 2-year reintervention rates (4.32% vs 2.66%; hazard ratio, 1.43; 95% confidence interval, 0.55-3.77; P = .461). There were no differences in any primary outcome between warfarin and novel oral anticoagulants. CONCLUSIONS: These data demonstrate that long-term aspirin plus anticoagulation use is associated with a lack of aortic sac reduction and persistent type II endoleak, but not an increased risk for subsequent reintervention. Because prior studies have demonstrated that sac regression is a correlate of survival, these findings associating regression failure suggest a potential therapeutic failure for patients undergoing EVAR who also require long-term anticoagulation therapy. Although not a contraindication, long-term anticoagulation should be considered when counseling patients with a surgical indication aortic aneurysm.

Accounting for Social Risk Does not Eliminate Race/Ethnic Disparities in COVID-19 Infection Among Insured Adults: a Cohort Study.

BACKGROUND: Communities of color have been disproportionately impacted by the COVID-19 epidemic in the USA. OBJECTIVES: To examine the relationship of self-reported social health needs with SARS-COV-2 infection by race/ethnicity among insured adults with access to high-quality health care. DESIGN AND PARTICIPANTS: A prospective cohort study of 26,741 adult Kaiser Permanente Northern California members insured by Medicaid and 58,802 Kaiser Permanente Colorado members insured by Medicare Advantage who completed social risk assessments prior to the onset of the COVID-19 pandemic. MAIN MEASURES: We examined the independent relationships of demographic, medical, and social factors on SARS-COV-2 testing and positivity between March 1, 2020, and November 30, 2020, by race/ethnicity. KEY RESULTS: Findings were similar in the two cohorts, with Latino (16-18%), Asian (11-14%), and Black (11-12%) members having the highest prevalence of SARS-COV-2 infection (ORs adjusted for age, gender, and use of interpreter ranging from 1.68 to 2.23 compared to White member [7-8%], p < 0.001). Further adjustment for medical comorbidity (e.g., obesity, diabetes, chronic lung disease); neighborhood measures; and self-reported social risk factors (e.g., trouble paying for basics, food insecurity, housing concerns, transportation barriers) did not appreciably change these results. CONCLUSIONS: Compared to non-Latino White members, members of other race/ethnic groups had higher positivity rates that were only minimally reduced after controlling for medical and neighborhood conditions and self-reported social risk factors. These findings suggest that traditional infection transmission factors such as essential work roles and household size that have disproportionate representation among communities of color may be important contributors to SARS-COV-2 infection among insured adults.

Left Subclavian Artery Coverage is Not Associated with Neurological Deficits in Trauma Patients Undergoing Thoracic Endovascular Repair.

BACKGROUND: Endovascular repair of the thoracic aorta (TEVAR) outcomes have been studied with an interest in complications related to left subclavian artery (LSA) coverage in patients with atherosclerotic pathologies; however, specific data on the management of the LSA in a trauma population are lacking. The objective of this study is to evaluate outcomes following TEVAR for traumatic aortic injury based on LSA coverage. METHODS: The Vascular Quality Initiative thoracic endovascular aortic repair module (2010-2017) was analyzed. Patients were included if they had a traumatic aortic injury requiring TEVAR. Patients were placed in 2 groups based on coverage of the LSA. Patients were propensity score matched and the primary outcomes were cerebrovascular symptoms and spinal cord ischemia. Additional clinical and resource utilization outcomes were analyzed. RESULTS: Four hundred and fifty one patients were included in the analysis. There were 268 patients in the LSA not-covered group and 183 patients in the LSA covered group. The mean aortic injury grade was 2.88 ± 0.056 vs. 2.88 ± 0.049 in the covered versus not-covered group (P = 0.957). Glasgow coma scale and injury severity score were not different between the groups. There was no difference between groups for cerebrovascular symptoms or spinal cord ischemia, 1.4% vs. 2.8%, P = 0.684 and 0% vs. 2.1%, P = 0.247, after propensity score matching. Significant differences in access site complications and resource utilization were identified between groups. CONCLUSIONS: This is the largest series to evaluate complications based on LSA coverage following TEVAR in trauma patients. Our data demonstrate that coverage of the LSA during TEVAR following blunt trauma is associated with no difference in central nervous system outcomes. As such, LSA revascularization strategies, while possible, are not directly supported by these data and should be individualized based on each patient's specific clinical scenario.

Bright, single helicity, high harmonics driven by mid-infrared bicircular laser fields.

High-harmonic generation (HHG) is a unique tabletop light source with femtosecond-to-attosecond pulse duration and tailorable polarization and beam shape. Here, we use counter-rotating femtosecond laser pulses of 0.8 µm and 2.0 µm to extend the photon energy range of circularly polarized high-harmonics and also generate single-helicity HHG spectra. By driving HHG in helium, we produce circularly polarized soft x-ray harmonics beyond 170 eV-the highest photon energy of circularly polarized HHG achieved to date. In an Ar medium, dense spectra at photon energies well beyond the Cooper minimum are generated, with regions composed of a single helicity-consistent with the generation of a train of circularly polarized attosecond pulses. Finally, we show theoretically that circularly polarized HHG photon energies can extend beyond the carbon K edge, extending the range of molecular and materials systems that can be accessed using dynamic HHG chiral spectro-microscopies.

Regional Variation in Usage of Ultrasound-Guided Femoral Access in the Vascular Quality Initiative.

BACKGROUND: Access site complications are among the most common complications following peripheral vascular interventions. Previous studies have demonstrated a reduced rate of complications with ultrasound-guided vascular access (UGVA). The objective of this study is to evaluate the regional use of UGVA within the Vascular Quality Initiative (VQI). METHODS: The VQI peripheral intervention module between 2010 and 2018 was evaluated. Regional ID was used to compare distribution of ultrasound usage. Regions were grouped into terciles based on the rate of ultrasound use. Patients were categorized based on type of access. Primary outcome was use of ultrasound across regions. Secondary outcomes were access site complications. RESULTS: Over 43,000 cases across the 18 VQI regions were evaluated. The average rate of ultrasound usage was 71% across the regions with a wide variation (range 38-97%). There is a significant difference in utilization among the top third (87%), middle third (79%), and bottom third (58%) (P < 0.001). Average sheath size was similar across all 3 groups. A higher use of ultrasound-guided access was associated with significantly fewer access site complications (top third 1.96% vs. bottom third 3.04%, P < 0.001), the most significant of which was a decreased rate of access site hematoma (top third 1.37% vs. bottom third 2.35%, P < 0.001). CONCLUSIONS: This is the first study to evaluate ultrasound-guided access across VQI regions. Our results demonstrate that despite strong evidence supporting the utilization of UGVA, there remains a wide variation in ultrasound usage across VQI regions. This is also the first study to show that the prevalence of ultrasound use in peripheral vascular interventions (PVI) is inversely related to access site complications. Given all of the data supporting the usage of UGVA across numerous specialties, our findings encourage the consideration of an ultrasound-first approach for vascular access in PVI and the implementation of targeted strategies and evidence-based guidelines to enhance UGVA utilization in PVI.

Effect of solid feed level and types of roughage on passage kinetics of milk replacer, concentrate, and roughage in veal calves.

This study aimed (1) to provide estimates of total mean retention times of milk replacer (MR), concentrates, and roughage in veal calves fed a mixed diet; (2) to determine the effect of level and type of solid feed (SF) on passage kinetics of MR, concentrates, and roughages in veal calves; and (3) to compare passage kinetics in veal calves using the fecal excretion curves of indigestible markers and a noninvasive 13C tracer breath test approach to determine whether the latter technique can serve as an alternative. At the start of the trial, 48 Holstein-Friesian calves (6 wk of age; 68 ± 7.7 kg of body weight; BW) were assigned to 1 of 4 dietary treatments (for statistical analysis, only 39 calf observations were used). Three treatments contained chopped wheat straw as roughage in the SF mixture in a concentrate:roughage ratio of 90:10 (dry matter basis). The SF level was 20 g/kg of metabolic BW per day (low straw), 30 g/kg of metabolic BW per day (middle straw), or 40 g/kg of metabolic BW per day (high straw). The fourth treatment (high hay) contained long perennial ryegrass hay as roughage in the SF mixture in a concentrate:roughage ratio of 70:30 (dry matter basis, at 40 g/kg of metabolic BW per day). The quantity of MR was fixed for the high straw treatment, whereas the amount of MR for the other treatments during the adaptation period was adjusted based on a pair gain strategy (i.e., exchanging ration components but keeping similar net energy). At the end of the adaptation period, calves ranged from 12 to 15 wk of age with an average BW of 123 ± 8.6 kg. Passage kinetics of concentrates were estimated by measuring 13C enrichment excess of CO2 in breath from a pulsed-dose of [1-13C]octanoate. Passage kinetics of roughage, concentrates, and MR were also estimated using fecal excretion curves obtained after ingestion of chromium-mordanted roughage, Yb2O3, and Co-EDTA, respectively. We conclude that [1-13C]octanoate cannot serve as a measure for oro-duodenal transit of concentrates because of unrealistic estimates. Based on the fecal excretion curves, we concluded that the total mean retention time of MR (i.e., time to peak; the moment that the excretion curve reaches peak concentration) was, on average, 12.4 h, and that the passage kinetics of MR was not affected by the level or type of SF. The mean retention time of concentrates was shorter (21.4 h) than that of both straw (59.1 h) and hay (36.8 h), and was not affected by the level or type of SF. Also, the mean retention time of the slowest compartment (i.e., the rumen) was shorter for concentrates (39.6 h) than that of straw (110.0 h) and hay (59.2 h). Contrary, the passage of roughage was affected by level and type of SF. Long hay increased time to peak by 22.3 h and decreased ruminal mean retention time by 50.8 h relative to chopped straw, indicating that the passage rate of long hay is faster than that of chopped straw. We conclude that the level and type of SF only affects the passage kinetics of roughage and not that of MR and concentrates.

Optical timing jitter due to atmospheric turbulence: comparison of frequency comb measurements to predictions from micrometeorological sensors.

During propagation through atmospheric turbulence, variations in the refractive index of air cause fluctuations in the time-of-flight of laser light. These timing jitter fluctuations are a major noise source for precision laser ranging, optical time transfer, and long-baseline interferometry. While there exist models that estimate the turbulence-induced timing jitter power spectra using parameters obtainable from conventional micrometeorological instruments, a direct and independent comparison of these models to measured timing jitter data has not been done. Here we perform this comparison, measuring turbulence-induced optical pulse timing jitter over a horizontal, near-ground path using frequency comb lasers while independently characterizing the turbulence along the path using a suite of micrometeorological sensors. We compare the power spectra of measured optical pulse timing jitter to predictions based on the measured micrometeorological data and standard turbulence theory. To further quantitatively compare the frequency comb data to the micrometeorological measurements, we extract and compare the refractive index structure parameter, Cn2, from both systems and find agreement to within a factor of 5 for wind speed >1 m/s, and further improvement is possible as wind speed increases. These results validate the use of conventional micrometeorological instruments in predicting optical timing jitter statistics over co-located laser beam paths.

Aortoiliac calcification correlates with 5-year survival after abdominal aortic aneurysm repair.

BACKGROUND: An anatomic severity grade (ASG) score to categorize and to define anatomic factors for abdominal aortic aneurysm (AAA) repair was proposed. Other studies have previously reported that aortic anatomic complexity is a marker of survival and resource utilization after repair, although it remains unclear whether individual components of the ASG score independently contribute to survival. This study analyzed and validated an aortic and iliac artery calcium scoring system that can potentially predict survival after AAA repair. METHODS: Patients who underwent infrarenal AAA repairs from July 2007 to May 2012 were analyzed using complete 5-year records. Those who died ≤30 days of surgery were excluded. Calcium score (CS) was defined using the ASG scoring system for its basis by preoperative imaging <6 months before surgery. A CS for any patient was 0 to 5 points, the sum of the points assigned to aortic neck (2 points total) and iliac artery (3 points total) calcification. A receiver operating characteristic curve was used to determine a CS threshold for mortality. The 5-year survivors and deaths were compared in regard to comorbidities, pharmacology, and CS at or above the defined threshold. Each variable with a P value <.1 between the groups was then placed into a Cox proportional hazards model, with statistical significance of P < .05. RESULTS: There were 356 patients who underwent AAA repair with complete 5-year follow-up data; 26% died within 5 years of surgery. Of these, 13% had CS of 0 with 15% mortality, 28% had CS of 1 with 21% mortality, 24% had CS of 2 with 24% mortality, 23% had CS of 3 with 35% mortality, 10% had CS of 4 with 40% mortality, and 2% had CS of 5 with 17% mortality. The receiver operating characteristic curve demonstrated an appropriate threshold of CS 3. Of these patients, 65% had a CS <3, whereas 35% had a CS ≥3. Patients with a CS ≥3 had a lower 5-year survival probability (P = .003). Comparing 5-year survivors and deaths in a Cox proportional hazards analysis, CS ≥3 was associated with a hazard ratio of 1.579 (95% confidence interval, 1.038-2.402; P = .0328). CONCLUSIONS: A CS ≥3 is linked to a lower 5-year survival after AAA repair in our population. This system potentially can be another measure for risk stratification and serve as a means to predict midterm mortality in AAA repairs. Future study will be needed for further validation to predict midterm mortality and to better guide surgical decision-making.

Bright circularly polarized soft X-ray high harmonics for X-ray magnetic circular dichroism.

We demonstrate, to our knowledge, the first bright circularly polarized high-harmonic beams in the soft X-ray region of the electromagnetic spectrum, and use them to implement X-ray magnetic circular dichroism measurements in a tabletop-scale setup. Using counterrotating circularly polarized laser fields at 1.3 and 0.79 µm, we generate circularly polarized harmonics with photon energies exceeding 160 eV. The harmonic spectra emerge as a sequence of closely spaced pairs of left and right circularly polarized peaks, with energies determined by conservation of energy and spin angular momentum. We explain the single-atom and macroscopic physics by identifying the dominant electron quantum trajectories and optimal phase-matching conditions. The first advanced phase-matched propagation simulations for circularly polarized harmonics reveal the influence of the finite phase-matching temporal window on the spectrum, as well as the unique polarization-shaped attosecond pulse train. Finally, we use, to our knowledge, the first tabletop X-ray magnetic circular dichroism measurements at the N4,5 absorption edges of Gd to validate the high degree of circularity, brightness, and stability of this light source. These results demonstrate the feasibility of manipulating the polarization, spectrum, and temporal shape of high harmonics in the soft X-ray region by manipulating the driving laser waveform.

Phase matching of noncollinear sum and difference frequency high harmonic generation above and below the critical ionization level.

We investigate the macroscopic physics of noncollinear high harmonic generation (HHG) at high pressures. We make the first experimental demonstration of phase matching of noncollinear high-order-difference-frequency generation at ionization fractions above the critical ionization level, which normally sets an upper limit on the achievable cutoff photon energies. Additionally, we show that noncollinear high-order-sum-frequency generation requires much higher pressures for phase matching than single-beam HHG does, which mitigates the short interaction region in this geometry. We also dramatically increase the experimentally realized cutoff energy of noncollinear circularly polarized HHG, reaching photon energies of 90 eV. Finally, we achieve complete angular separation of high harmonic orders without the use of a spectrometer.

Helicity-Selective Enhancement and Polarization Control of Attosecond High Harmonic Waveforms Driven by Bichromatic Circularly Polarized Laser Fields.

High harmonics driven by two-color counterrotating circularly polarized laser fields are a unique source of bright, circularly polarized, extreme ultraviolet, and soft x-ray beams, where the individual harmonics themselves are completely circularly polarized. Here, we demonstrate the ability to preferentially select either the right or left circularly polarized harmonics simply by adjusting the relative intensity ratio of the bichromatic circularly polarized driving laser field. In the frequency domain, this significantly enhances the harmonic orders that rotate in the same direction as the higher-intensity driving laser. In the time domain, this helicity-dependent enhancement corresponds to control over the polarization of the resulting attosecond waveforms. This helicity control enables the generation of circularly polarized high harmonics with a user-defined polarization of the underlying attosecond bursts. In the future, this technique should allow for the production of bright highly elliptical harmonic supercontinua as well as the generation of isolated elliptically polarized attosecond pulses.

Bundling of Reimbursement for Inferior Vena Cava Filter Placement Resulted in Significantly Decreased Utilization between 2012 and 2014.

BACKGROUND: On January 1, 2012, reimbursement for inferior vena cava filters (IVCFs) became bundled by the Centers for Medicare and Medicaid Services. This resulted in ICVF placement (CPT code 37191) now yielding 4.71 relative value units (RVUs), a decrease from 15.6 RVUs for placement and associated procedures (CPT codes 37620, 36010, 75825-26, 75940-26). Our hypothesis was that IVCF utilization would decrease in response to this change as other procedures had done once they had become bundled. METHODS: Including data from 2010 to 2011 (before bundling) and 2012 to 2014 (after bundling), we utilized 5% inpatient, outpatient, and carrier files of Medicare limited data sets and analyzed IVCF utilization before and after bundling across specialty types, controlling for total diagnosis of deep vein thrombosis (DVT) and pulmonary embolism (PE) (ICD-9 codes 453.xx and 415.xx, respectively) and placement location. RESULTS: In 2010 and 2011, the rates/10,000 DVT/PE diagnoses were 918 and 1,052, respectively (average 985). In 2012, 2013, and 2014, rates were 987, 877, and 605, respectively (average 823). Comparing each year individually, there is a significant difference (P < 0.0001) with 2012, 2013, and 2014 having lower rates of ICVF utilization. Comparing averages in the 2010-2011 and 2012-2014 groups, there is also a significant decrease in utilization after bundling (P < 0.0001). CONCLUSIONS: Following the bundling of reimbursement for IVCF placement, procedural utilization decreased significantly. More data from subsequent years will be needed to show if this decrease utilization continues to persist.

Aortic anatomic severity grade correlates with resource utilization.

BACKGROUND: Potential cost effectiveness of endovascular aneurysm repair (EVAR) compared with open aortic repair (OAR) is offset by the use of intraoperative adjuncts (components) or late reinterventions. Anatomic severity grade (ASG) can be used preoperatively to assess abdominal aortic aneurysms, and provide a quantitative measure of anatomic complexity. The hypothesis of this study is that ASG is directly related to the use of intraoperative adjuncts and cost of aortic repair. METHODS: Patients who undergo elective OAR and EVAR for abdominal aortic aneurysms were identified over a consecutive 3-year period. ASG scores were calculated manually using three-dimensional reconstruction software by two blinded reviewers. Statistical analysis of cost data was performed using a log transformation. Regression analyses, with a continuous or dichotomous outcome, used a generalized estimating equations approach with the sandwich estimator, being robust with respect to deviations from model assumptions. RESULTS: One hundred forty patients were identified for analysis, n = 33 OAR and n = 107 EVAR. The mean total cost (± standard deviation) for OAR was per thousand (k) $38.3 ± 49.3, length of stay (LOS) 13.5 ± 14.2 days, ASG score 18.13 ± 3.78; for EVAR, mean total cost was k $24.7 ± 13.0 (P = .016), LOS 3.0 ± 4.4 days (P = .012), ASG score 15.9 ± 4.13 (P = .010). In patients who underwent EVAR, 25.2% required intraoperative adjuncts, and analysis of this group revealed a mean total cost of k $31.5 ± 15.9, ASG score 18.48 ± 3.72, and LOS 3.9 ± 4.5, which were significantly greater compared with cases without adjunctive procedures. An ASG score of ≥15 correlated with an increased propensity for requirement of intraoperative adjuncts; odds ratio, 5.75 (95% confidence interval, 1.82-18.19). ASG >15 was also associated with chronic kidney disease, end stage renal disease, hypertension, female sex, increased cost, and use of adjunctive procedures. CONCLUSIONS: Complex aneurysm anatomy correlates with increased total cost and need for adjunctive procedures during EVAR. Preoperative assessment with ASG scores can delineate patients at greater risk for increased resource use. Patient comorbid factors are associated with anatomic complexity defined according to ASG. A critical examination of the relationship between anatomic complexity and finances is required within the context of aggressive endovascular treatment strategies and shifts toward value-based reimbursement.

Controlling Nonsequential Double Ionization in Two-Color Circularly Polarized Femtosecond Laser Fields.

Atoms undergoing strong-field ionization in two-color circularly polarized femtosecond laser fields exhibit unique two-dimensional photoelectron trajectories and can emit bright circularly polarized extreme ultraviolet and soft-x-ray beams. In this Letter, we present the first experimental observation of nonsequential double ionization in these tailored laser fields. Moreover, we can enhance or suppress nonsequential double ionization by changing the intensity ratio and helicity of the two driving laser fields to maximize or minimize high-energy electron-ion rescattering. Our experimental results are explained through classical simulations, which also provide insight into how to optimize the generation of circularly polarized high harmonic beams.

Solvents effects on charge transfer from quantum dots.

To predict and understand the performance of nanodevices in different environments, the influence of the solvent must be explicitly understood. In this Communication, this important but largely unexplored question is addressed through a comparison of quantum dot charge transfer processes occurring in both liquid phase and in vacuum. By comparing solution phase transient absorption spectroscopy and gas-phase photoelectron spectroscopy, we show that hexane, a common nonpolar solvent for quantum dots, has negligible influence on charge transfer dynamics. Our experimental results, supported by insights from theory, indicate that the reorganization energy of nonpolar solvents plays a minimal role in the energy landscape of charge transfer in quantum dot devices. Thus, this study demonstrates that measurements conducted in nonpolar solvents can indeed provide insight into nanodevice performance in a wide variety of environments.

Effect of continuity of care on hospital utilization for seniors with multiple medical conditions in an integrated health care system.

PURPOSE: Lower continuity of care has been associated with higher rates of adverse outcomes for persons with multiple chronic medical conditions. It is unclear, however, whether this relationship also exists within integrated systems that offer high levels of informational continuity through shared electronic health records. METHODS: We conducted a retrospective cohort study of 12,200 seniors with 3 or more chronic conditions within an integrated delivery system. Continuity of care was calculated using the Continuity of Care Index, which reflects visit concentration with individual clinicians. Using Cox proportional hazards regression permitting continuity to vary monthly until the outcome or censoring event, we separately assessed inpatient admissions and emergency department visits as a function of primary care continuity and specialty care continuity. RESULTS: After adjusting for covariates (demographics; baseline, primary, and specialty care visits; baseline outcomes; and morbidity burden), greater primary care continuity and greater specialty care continuity were each associated with a lower risk of inpatient admission (respective hazard ratios (95% CIs) = 0.97 (0.96, 0.99) and 0.95 (0.93, 0.98)) and a lower risk of emergency department visits (respective hazard ratios = 0.97 (0.96, 0.98) and 0.98 (0.96, 1.00)). For the subgroup with 3 or more primary care and 3 or more specialty care visits, specialty care continuity (but not primary care continuity) was independently associated with a decreased risk of inpatient admissions (hazard ratio = 0.94 (0.92, 0.97)), and primary care continuity (but not specialty care continuity) was associated with a decreased risk of emergency department visits (hazard ratio = 0.98 (0.96, 1.00)). CONCLUSIONS: In an integrated delivery system with high informational continuity, greater continuity of care is independently associated with lower hospital utilization for seniors with multiple chronic medical conditions. Different subgroups of patients will benefit from continuity with primary and specialty care clinicians depending on their care needs.