Nonmonotonic Composition Dependence of Viscosity upon Adding Single-Chain Nanoparticles to Entangled Polymers.

Well-characterized single-chain nanoparticles (SCNPs), synthesized from a linear polystyrene precursor through an intramolecular [4 + 4] thermal cycloaddition cross-linking reaction in dilute conditions, were added to entangled polystyrene melts at different concentrations. Starting from the pure linear melt, which is much more viscous than the melt of SCNPs, the zero-shear viscosity increased upon the addition of nanoparticles and reached a maximum before eventually dropping to the value of the SCNP melt. Molecular simulations reveal the origin of this unexpected behavior, which is the interplay of the very different compositional dependences of the dynamics of the two components. The SCNPs become much slower than the linear chains as their concentration decreases because they are threaded by the linear chains, reaching a maximum viscosity which is higher than that of the linear chains at a fraction of about 20%. This behavior is akin to that of single-loop ring polymers when added to linear matrices. This finding provides insights into the design and use of SCNPs as effective entropic viscosity modifiers of polymers and contributes to the discussion of the physics of loopy structures.

The optimal operative protocol to accomplish CO2-EVAR resulting from a prospective interventional multicenter study.

OBJECTIVES: Carbon dioxide (CO2) angiography for endovascular aortic repair (CO2-EVAR) is used to treat abdominal aortic aneurysms (AAAs), especially in patients with chronic kidney disease or allergy to iodinated contrast medium (ICM). However, some technical issues regarding the visualization of the lowest renal artery (LoRA) and the best quality image through angiographies performed from pigtail or introducer sheath are still unsolved. The aim of this study was to analyze different steps of CO2-EVAR to create an operative standardized protocol. METHODS: Patients undergoing CO2-EVAR were prospectively enrolled in five European centers from 2019 to 2021. CO2-EVAR was performed using an automated injector (pressure, 600 mmHg; volume, 100 cc); a small amount of ICM was injected in case of difficulty in LoRA visualization. LoRA visualization and image quality (1 = low, 2 = sufficient, 3 = good, 4 = excellent) were analyzed at different procedure steps: preoperative CO2 angiography from pigtail and femoral introducer sheath (first step), angiographies from pigtail at 0%, 50%, and 100% of proximal main body deployment (second step), contralateral hypogastric artery (CHA) visualization with CO2 injection from femoral introducer sheath (third step), and completion angiogram from pigtail and femoral introducer sheath (fourth step). Intraoperative and postoperative CO2-related adverse events were also evaluated. χ2 and Wilcoxon tests were used for statistical analysis. RESULTS: In the considered period, 65 patients undergoing CO2-EVAR were enrolled (55/65 [84.5%] male; median age, 75 years [interquartile range (IQR), 11.5 years]). The median ICM injected was 17 cc (IQR, 51 cc); 19 (29.2%) of 65 procedures were performed with 0 cc ICM. Fifty-five (84.2%) of 65 patients underwent general anesthesia. In the first step, median image quality was significantly higher with CO2 injected from femoral introducer (pigtail, 2 [IQR, 3] vs introducer, 3 [IQR, 3]; P = .008). In the second step, LoRA was more frequently detected at 50% (93% vs 73.2%; P = .002) and 100% (94.1% vs 78.4%; P = .01) of proximal main body deployment compared with first angiography from pigtail; similarly, image quality was significantly higher at 50% (3 [IQR, 3] vs 2 [IQR, 3]; P ≤ .001) and 100% (4 [IQR, 3] vs 2 [IQR, 3]; P = .001) of proximal main body deployment. CHA was detected in 93% cases (third step). The mean image quality was significantly higher when final angiogram (fourth step) was performed from introducer (pigtail, 2.6 ± 1.1 vs introducer, 3.1 ± 0.9; P ≤ .001). The intraoperative (7.7%) and postoperative (12.5%) adverse events (pain, vomiting, diarrhea) were all transient and clinically mild. CONCLUSIONS: Preimplant CO2 angiography should be performed from femoral introducer sheath. Gas flow impediment created by proximal main body deployment can improve image quality and LoRA visualization with CO2. CHA can be satisfactorily visualized with CO2 alone. Completion CO2 angiogram should be performed from femoral introducer sheath. This operative protocol allows performance of CO2-EVAR with 0 cc or minimal ICM, with a low rate of mild temporary complications.

Vascular education through e-Learning.

Background: The COVID-19 pandemic has changed everyday life and work in many ways. As travelling to meetings and conferences was almost completely suppressed for most of healthcare professionals, e-Learning became increasingly prominent. The overall utility of e-Learning during the COVID-19 pandemic as well as its shortcomings in the international community of vascular surgery were assessed through the EL-COVID study. Regional variability was observed amongst participating nations, which is currently being addressed through several ongoing subgroup analyses. Our study completes the aforementioned efforts and aims to investigate the adherence and adoption of vascular e-Learning in Germany. Methods and participants: Using an online survey, EL-COVID gathered answers from 856 vascular surgeons, of whom 70 were located in Germany. We analyzed the answers of 62 German responders that attended at least one e-Learning activity and compared them with the remaining worldwide data. Results: Out of all European countries, Germany was best represented and ranked second worldwide after Mainland China (n=109). 30.6 percent of the German responders were female (vs. 20% worldwide; p=0.048) and 56.4% were vascular surgeons with >5 years of practice (vs. 56.3; p=0.975). The international cohort generally engaged in more e-Learning. Most German participants attended less than 4 online activities, while only 24.2% took part in more than 4 such events (vs. 56.3; p<0.0001). While the overall impression of e-Learning activities during the COVID-19 pandemic was positive, German employers were less supportive of participation during working hours (30.6% vs. 44%; p=0.042). The main reason for not attending was lack of time due to increased workload (56.5% vs. 50%; p=0.328). National and international societies played a lesser role in promoting such activities in Germany (22.6% vs. 39.2%; p=0.010), the same accounts for social media (16.1 vs. 30.3; p=0.017). Conclusions: E-Learning complements the classical training methods and has been embraced as a relevant alternative in the time of the COVID-19 pandemic. The results of this survey appeal to German employers and national societies to improve support and dissemination of e-Learning activities in the vascular medicine community.

Venous Thromboembolism Following Major Abdominal Surgery for Cancer: A Guide for the Surgical Intern.

BACKGROUND: Venous thromboembolism (VTE) is a term used to compositely describe deep vein thrombosis (DVT) and pulmonary embolism (PE). Overall, the incidence of VTE after major abdominal and pelvic surgery has been reported to be between 10% and 40%. OBJECTIVE: The aim of this study is to estimate the incidence of post-operative VTE in patients undergoing major abdominal surgery for cancer, to identify risk factors associated with VTE, and to assess available thromboprophylaxis tools. METHODS: A Medline and Cochrane literature search from database inception until February 1st, 2021 was performed according to the PRISMA (Preferred Reporting Items for Systematic reviews and Meta-Analyses) guidelines. RESULTS: Thirty-one studies met our eligibility criteria and were included in the current review. In total, 435,492 patients were identified and the overall incidence of VTE was 2.19% (95% CI: 1.82-2.38). Τhe following risk factors were associated with VTE: smoking, advanced age (>70 years), a history of diabetes mellitus, American Society of Anesthesiologists' (ASA) classification of Physical Health class III or IV, a history of cardiovascular or pulmonary disease, a history of DVT or PE, elevated plasma fibrinogen level, c-reactive protein (CRP) level, cancer stage III or IV, postoperative acute respiratory distress syndrome (ARDS), prolonged postoperative hospital stay, previous steroid use, history of Inflammatory Bowel Disease (IBD), heart failure and neoadjuvant and adjuvant chemotherapy. CONCLUSION: VTE remains an important complication after major abdominal surgery for cancer and seems to increase mortality rates.

Limb Salvage in Patients With Severe Critical Limb Ischemia (CLI) After Referral for a Second Opinion to a Dedicated CLI Center.

The complexity of critical limb ischemia (CLI) requires dedicated multidisciplinary teams of different care providers, who will supervise the full cycle of CLI care. Until CLI treatment is fully centralized, such dedicated teams may work as second-opinion tools before major amputation is undertaken in CLI patients. The aim of the study is to assess the effectiveness of a well-timed referral to a dedicated CLI-center of patients scheduled to major amputation elsewhere. A retrospective analysis of all CLI-patients treated in our department between January 2019 and March 2020 was conducted. Only patients scheduled for a major amputation elsewhere and referred to our clinic were included. Primary endpoint was amputation-free survival, whereas technical success, limb salvage, minor amputation rate, re-admission at 30 days, and frequency of medication change from other disciplines were the secondary endpoints. Sixteen patients with 19 treated limbs were identified and included in this analysis. The WIfI (wound, infection and foot ischemia) clinical stage on admission was 2 in 4 limbs (21%), 3 in 5 limbs (26%), and 4 in 10 limbs (53%). All patients underwent advanced endovascular revascularization. Minor amputation was performed in 8 patients (42%). Amputation-free survival at 6 months was 93% with limb salvage rate of 100%. Technical success and re-admission rates at 30 days was 95% and 6%, respectively. There was a medication adjustment from other specialties in 13 (81%) patients. Patients in severe stages of CLI scheduled to major amputation reached high limb salvage and survival rate, since they are referred for a second opinion to a dedicated multidisciplinary CLI team.

Dataset of the vascular e-Learning during the COVID-19 pandemic (EL-COVID) survey.

This dataset supports the findings of the vascular e-Learning during the COVID-19 pandemic survey (the EL-COVID survey). The General Data Protection Regulation (GDPR) of the European Union was taken into consideration in all steps of data handling. The survey was approved by the institutional ethics committee of the Primary Investigator and an online English survey consisting of 18 questions was developed ad-hoc. A bilingual English-Mandarin version of the questionnaire was developed according to the instructions of the Chinese Medical Association in order to be used in mainland People's Republic of China. Differences between the two questionnaires were minor and did affect the process of data collection. Both questionnaires were hosted online. The EL-COVID survey was advertised through major social media. All national and regional contributors contacted their respective colleagues through direct messaging on social media or by email. Eight national societies or groups supported the dissemination of the EL-COVID survey. The data provided demographics information of the EL-COVID participants and an insight on the level of difficulty in accessing or citing previously attended online activities and whether participants were keen on citing these activities in their Curricula Vitae. A categorization of additional comments made by the participants are also based on the data. The survey responses were filtered, anonymized and submitted to descriptive analysis of percentage.

Vascular e-Learning During the COVID-19 Pandemic: The EL-COVID Survey.

BACKGROUND: The corona virus disease (COVID-19) pandemic has radically changed the possibilities for vascular surgeons and trainees to exchange knowledge and experience. The aim of the present survey is to inventorize the e-learning needs of vascular surgeons and trainees as well as the strengths and weaknesses of vascular e-Learning. METHODS: An online survey consisting of 18 questions was created in English, with a separate bilingual English-Mandarin version. The survey was dispersed to vascular surgeons and trainees worldwide through social media and via direct messaging from June 15, 2020 to October 15, 2020. RESULTS: Eight hundred and fifty-six records from 84 different countries could be included. Most participants attended several online activities (>4: n = 461, 54%; 2-4: n = 300, 35%; 1: n = 95, 11%) and evaluated online activities as positive or very positive (84.7%). In deciding upon participation, the topic of the activity was most important (n = 440, 51.4%), followed by the reputation of the presenter or the panel (n = 178, 20.8%), but not necessarily receiving accreditation or certification (n = 52, 6.1%). The survey identified several shortcomings in vascular e-Learning during the pandemic: limited possibility to attend due to lack of time and increased workload (n = 432, 50.5%), no protected/allocated time (n = 488, 57%) and no accreditation or certification, while technical shortcomings were only a minor problem (n = 25, 2.9%). CONCLUSIONS: During the COVID-19 pandemic vascular e-Learning has been used frequently and was appreciated by vascular professionals from around the globe. The survey identified strengths and weaknesses in current e-Learning that can be used to further improve online learning in vascular surgery.

The Association of Spondylitis and Aortic Aneurysm Disease.

OBJECTIVES: The aim of this study is to assess any relation between spondylitis and aortic aneurysmal disease by reviewing the current literature. METHODS: A systematic search was undertaken using MEDLINE, EMBASE and CENTRAL databases till May 2019, for articles reporting on patients suffering from spondylitis and aortic aneurysm. RESULTS: The most involved aortic segment was infrarenal aorta (56.9%). The lumbar vertebrae were more frequently affected (79.7%). Commonest symptoms were back pain (79.1%), fever (33.7%) and lower limb pain (29.1%). 55.8% of cases were diagnosed using computed tomography. The pathology was attributed to infectious causes in 25.1% of cases. 53.4% of patients were treated only for the aneurysm, 27.9% for both pathologies, while two patients solely for the vertebral disease. Endovascular aneurysm repair was chosen in 12.8% of cases. The 30-day mortality was 8.1% (7/86); mostly from vascular complications. CONCLUSIONS: A synchronous spondylitis and aortic aneurysm may share common etiopathology, when an infectious or inflammatory cause is presented. The lumbar vertebrae are more frequently affected. Low quality data do not allow safe conclusion to suggest the best treatment option.

The Potential Role of Carbon Nanoparticles in Lymph Node Tracing, Recurrent Laryngeal Nerve Identification and Parathyroid Preservation During Thyroid Surgery: A Systematic Review.

BACKGROUND/OBJECTIVE: Carbon nanoparticles (CNs) are a novel injected suspension used during thyroidectomy in order to black stain the thyroid gland and the lymph nodes while maintaining the anatomic color of the parathyroid glands and the laryngeal nerves. The aim of this systematic review is to investigate the benefits of carbon nanoparticles in thyroid surgical procedures and examine their role in lymph node tracing, parathyroid preservation, and recurrent laryngeal nerve protection. METHODS: A systematic review of the literature in the PubMed/Medline database was performed. Articles reporting randomized clinical trials, prospective, and retrospective studies that compared the use of carbon nanoparticles in one group of patients with a control-blank group were included. The article was reported in accordance with PRISMA guidelines (CRD42021243015). RESULTS: The search strategy retrieved 22 studies of the literature. Fourteen studies calculated a greater number of lymph nodes detected/dissected in the central neck zone to the patients using CN solution and 1 article noted a higher rate of lymph nodes resected in the lateral neck zone in the same group of patients. A significant increase in the number of metastatic lymph nodes retrieved in the CN group was found in 7 studies. Twenty-one studies suggested that the use of CNs for the protection of the parathyroid glands was beneficial. Transient hypoparathyroidism and transient hypocalcemia were presented with a significantly lower incidence in the CN group in 13 and in 8 studies, respectively. CONCLUSION: Carbon nanoparticles may improve both central and lateral neck dissection and enhance parathyroid gland identification and preservation.

Captopril versus atenolol to prevent expansion rate of thoracic aortic aneurysms: rationale and design.

Thoracic aortic aneurysms are correlated with significant mortality and morbidity. No therapy, however, is effective at limiting aneurysm expansion and preventing rupture. Angiotensin-converting enzyme inhibitors can reduce the wall shear stress and inflammation, both of which play vital roles in the expansion of the aneurysm. A total of 636 patients will be randomized into one of three parallel arms, receiving captopril, atenolol or placebo. The primary end point will be the rate of change in the absolute diameter of the aortic root and ascending aorta on MRI of the aorta after 36 months. The trial will investigate the efficacy of angiotensin-converting enzyme inhibitors versus beta-blocker therapy in reducing the growth rate of thoracic aortic aneurysms and rupture. Trial registration number: NCT04224675.

Tissue-specific relaxin-2 is differentially associated with the presence/size of an arterial aneurysm and the severity of atherosclerotic disease in humans.

Circulating or tissue-related biomarkers are of clinical value for risk stratification in patients with abdominal aortic aneurysms. Relaxin-2 (RL2) has been linked to the presence and size of arterial aneurysms, and to the extent of atherosclerosis in human subjects. Here, we assessed the expression levels of RL2 in aneurysmal (AA, n = 16) and atherosclerotic (ATH, n = 22) arteries, and established the correlation between RL2 levels and the presence/size of AA and the clinical severity of atherosclerosis. The expression levels of metalloproteinases (MMPs) and endothelial nitric oxide synthetase (eNOS) were also detected for correlations with different phenotypes of atherosclerosis and AA. Temporal artery biopsy specimens (n = 6) and abdominal aortic tissues harvested from accident victims during autopsy (n = 10) were used as controls. Quantitative tissue biomarker analysis revealed that tissue-specific RL2 was increased in patients with larger or symptomatic AA compared to subjects with atherosclerotic disease and healthy controls. In situ RL2 levels were proportional to the size and the severity of aneurysmatic disease, and were substantially elevated in patients with symptomatic aneurysm of any diameter or asymptomatic aneurysm of a diameter >350% of that of the normal artery. In contrast, tissue RL2 was inversely associated with the clinical severity of atherosclerotic lesions. Correlation between RL2 and MMP2 was different between ATH1 and ATH2, depending on atherosclerosis grade. Overall, tissue RL2 is differentially associated with discrete phenotypes of arterial disease and might exert multipotent biological effects on vascular wall integrity and remodeling in human subjects.

Endothelium in Aortic Aneurysm Disease: New Insights.

Inflammation is recognized as a fundamental element in the development and growth of aortic aneurysms. Aortic aneurysm is correlated with aortic wall deformities and injury, as a result of inflammation, matrix metalloproteinases activation, oxidative stress, and apoptosis of vascular smooth muscle cells. The endothelial wall has a critical part in the inflammation of the aorta and endothelial heterogeneity has proven to be significant for modeling aneurysm formation. Endothelial shear stress and blood flow affect the aortic wall through hindrance of cytokines and adhesion molecules excreted by endothelial cells, causing reduction of the inflammation process in the media and adventitia. This pathophysiological process results in the disruption of elastic fibers, degradation of collagen fibers, and destruction of vascular smooth muscle cells. Consequently, the aortic wall is impaired due to reduced thickness, decreased mechanical function, and cannot tolerate the impact of blood flow leading to aortic expansion. Surgery is still considered the mainstay therapy for large aortic aneurysms. The prevention of aortic dilation, though, is based on the hinderance of endothelial dysregulation with drugs, the reduction of reactive oxygen and nitrogen species, and also the reduction of pro-inflammatory molecules and metalloproteinases. Further investigations are required to enlighten the emerging role of endothelial cells in aortic disease.

Physiology of Intraluminal Administration of Carbon Dioxide as a Contrast Medium.

BACKGROUND: Carbon dioxide (CO2) exists in nature around us. In the middle of the 20th century, the intraluminal injection of CO2 demonstrated similar results to those of Digital Subtraction Angiography (DSA) with an iodinated contrast agent (ICA). Since then, the technology behind CO2 DSA has developed significantly. OBJECTIVE: The aim of this study is to inform physicians about the unique properties of CO2 and its physiology after intraluminal injection. METHODS: An extensive search for English literature on the properties of CO2 and the physiology of intraluminal administration was conducted using Pubmed. RESULTS: There is sufficient literature on the properties of CO2 and the physiology of CO2 DSA. A review of this literature explains what happens to the human organism after the injection of CO2. CONCLUSION: There is enough evidence that CO2 DSA is both effective, diagnostic and safe, but the properties of CO2 should be taken under consideration as complications occur, although rarely.

Tips and tricks to cross chronic total occlusions in the superficial femoral artery.

Chronic total occlusion (CTO) is a common finding during endovascular treatment of peripheral arterial disease. The treatment of CTOs is a challenging task, which requires good knowledge of the devices and their specific characteristics and skills to different techniques for crossing. As a matter of fact, any dedicated center treating patients with peripheral arterial disease requires an adequate consignment stock regarding wires, catheters, balloons and some specific devices for challenging anatomic scenarios. Herein, the most important steps of a successful recanalization of a femoropopliteal CTO are summarized together with a number of tips regarding utilization of different techniques and specific devices.