Vein Size Research Articles

Effect of a thin-tipped short bevel needle for peripheral intravenous access on the compressive deformation and displacement of the vein: A preclinical study.

Peripheral intravenous catheter (PIVC) insertion often fails on the first attempt. Risk factors include small vein size and dehydration, causing vein deformation and displacement due to puncture resistance of the vessel. The authors developed a short, thin-tipped bevel needle and compared its puncture performance with needles of four available PIVCs using an ex vivo model. The PIVC with the thin-tipped short bevel needle was compared to four available PIVCs using an ex vivo model which simulated the cephalic vein of the human forearm. The ex vivo model consisted of a porcine shoulder and porcine internal jugular vein, and was used for evaluation of the rate of vein deformation and vessel displacement during needle insertion. An ex vivo model was created with a vessel diameter of 2.7-3.7 mm and a depth of 2-5 mm. The thin-tipped short bevel PIVC needle was associated with a significantly lower compressive deformation rate and venous displacement compared to the needles of the other four PIVCs. The thin-tipped short bevel needle induced lower compressive deformation and displacement of the vein than the conventional needles. This needle has the potential to improve the first-attempt success rate of peripheral intravenous catheterization in patients with difficult venous access.

Study of coronary sinus anatomy during levophase of coronary angiography.

BACKGROUNDCoronary sinus (CS) imaging has recently gained importance due to increasing need for mapping and ablation of electrophysiological arrhythmias and left ventricular (LV) pacing during cardiac resynchronization therapy (CRT). Retrograde venogram is the current standard for imaging CS and its tributaries. AIMTo evaluate CS anatomy during levophase of routine coronary angiography to aid LV lead implantation during CRT.METHODSIn this prospective observational study, 164 patients undergoing routine coronary angiography for various indications (Chronic stable angina-44.5%, acute coronary syndrome- 39.5%, Dilated cardiomyopathy-11%, atypical chest pain-5%) were included. Venous phase (levophase) of left coronary injection was recorded in left anterior oblique - cranial and right anterior oblique -cranial views. Visibility of coronary veins, width and shape of CS ostium, angulations of proximal CS with body of CS were noted. Presence, size, take-off angle and tortuosity of posterolateral vein (PLV), anterior interventricular veins (AIV) and middle cardiac vein (MCV) were also noted.RESULTSDuring levophase, visibility grade (Muhlenbruch grade) for coronary veins was 3 in 74% and 2 in 26% of cases. Visibility of CS did not correlate with body mass index. The diameter of CS ostium was < 10 mm, 10-15 mm and > 15 mm in 48%, 42% and 10% of patients respectively. Proximal CS was tubular in 136 (83%) patients and funnel-shaped in 28 (17%) patients. Sharp take-off angulation between ostium and body of CS was seen in 16 (10%) patients. Two or more PLV were present in 8 patients while PLV was absent in 52 (32%) patients. Angle of take-off of PLV with body of CS was favourable (0°-45°) in 65 (40%) patients. The angle was 45°-90° in 36 patients and difficult take-off angle (> 90°) was seen in 8 patients. Length of PLV reached distal third of myocardium in 84 cases and middle third in 11 cases. There was no tortuosity in 79 cases, a single bend in 29 cases and more than 2 bends in 4 cases. Thirty nine (24%) patients had other veins supplying posterior/Lateral wall of LV. There was a single vein supplying lateral/posterior wall in 31 (19%) patients. Diameter of MCV and AIV was significantly larger in patients with absent PLV as compared to patients with a PLV. CONCLUSIONLevophase study of left coronary injection is effective in visualization of the CS in almost all patients undergoing coronary angiography and may be an effective alternative to retrograde venogram in patients with LV dysfunction or LBBB.

Multi-functional topology optimization of Victoria cruziana veins.

The growth and development of biological tissues and organs strongly depend on the requirements of their multiple functions. Plant veins yield efficient nutrient transport and withstand various external loads. Victoria cruziana, a tropical species of the Nymphaeaceae family of water lilies, has evolved a network of three-dimensional and rugged veins, which yields a superior load-bearing capacity. However, it remains elusive how biological and mechanical factors affect their unique vein layout. In this paper, we propose a multi-functional and large-scale topology optimization method to investigate the morphomechanics of Victoria cruziana veins, which optimizes both the structural stiffness and nutrient transport efficiency. Our results suggest that increasing the branching order of radial veins improves the efficiency of nutrient delivery, and the gradient variation of circumferential vein sizes significantly contributes to the stiffness of the leaf. In the present method, we also consider the optimization of the wall thickness and the maximum layout distance of circumferential veins. Furthermore, biomimetic leaves are fabricated by using the three-dimensional printing technique to verify our theoretical findings. This work not only gains insights into the morphomechanics of Victoria cruziana veins, but also helps the design of, for example, rib-reinforced shells, slabs and dome skeletons.

Effect of exercises on the maturation of newly created arteriovenous fistulas over distal and proximal upper limb: A systematic review and meta-analysis.

The aims of our review were: (i) to evaluate the effect of post-operative upper extremity exercise on maturation of AVFs, stratified by their locations. (ii) To evaluate the effect of pre-operative arm exercise on patients' superficial vein caliber of patients. Literature search was performed on PubMed, Cochrane Library, Cumulative Index to Nursing and Allied Health Literature (CINAHL), and China National Knowledge Infrastructure (CNKI) to identify eligible articles. The quality of the randomized controlled trials (RCTs) were assessed using the Cochrane Risk of Bias tool 2.0. In the Meta-analysis, Risk ratios (RRs) of clinical maturation and ultrasonographic maturation were pooled from studies focused on post-operative exercise program; Mean difference (MD) of venous caliver was pooled from those studied pre-operative exercise. Nine studies (six for post-operative exercise; three for pre-operative exercise) were included in the review. Among the AVFs created in distal region (158 patients in exercise group and 144 patients in control group), there was a significantly superior clinical maturation (RR: 1.28; 95% CI: 1.10-1.48, p = 0.001; I2 = 0), and ultrasonographic maturation (RR: 1.30; 95% CI: 1.07-1.59, p = 0.009; I2 = 0) in the exercise group in comparison to the control group. For the AVFs created in proximal region (93 and 96 patients in exercise group and control group respectively), there is no significant difference in clinical maturation (RR:1.25, 95% CI: 0.88-1.78, p = 0.27, I2 = 74%) and ultrasonographic maturation (RR: 1.17, 95% CI: 0.97-1.40, p = 0.11, I2 = 43%) between the exercise group and controls. For pre-operative exercise, the mean difference of 0.34 mm (95% CI: 0.23-0.46, p < 0.001, I2 = 87% ) was found for vein size. In conclusion, existing upper extremity exercise programs appear to be useful in facilitating maturation of AVFs created in distal region, while its effect on fistulas created in proximal region is less certain. However, more robust trials are warranted to establish these findings.

Characterization of portal vein and other abdominal organs in portal hypertension patients using ultrasound

Portal hypertension occurs when the venous pressure increases in the portal vein due to some pathological changes such as liver cirrhosis, which results in an increased diameter of the portal and splenic vein. Objective: To assess and characterize the portal vein and other abdominal organs in portal hypertension patients using ultrasound to minimize the incidence of serious and life-threatening consequences of portal hypertension. Methods: A cross-sectional study with a sample size of 108 patients was carried out in five months, in a private hospital in Gujranwala. The subjects of age &gt; 30 years were included with other considered variables such as gender, portal and splenic vein diameter, size, and characteristics pattern of the liver &amp; spleen size with other abdominal complications. After taking informed written consent, patients were examined in a supine position using Mindray DC-3 Ultrasound Machine with a convex probe of 3.5 MHz’s frequency. After collecting data, it was analyzed using SPSS version 20. Results: The study revealed that 73.1% of patients were predominantly male with a male-to-female ratio and the patients in age between 50 – 59 years were more afflicted with this condition. 51.9% of patients were diagnosed with moderate dilatation of the portal vein and severe splenic vein dilatation was seen in 36.1% of the patients. The liver size was reduced in 75% of patients. 35.2% of patients were diagnosed with grossly enlarged spleen while the other 65% of patients were with mild and moderate splenomegaly. In 87% of patients, normal liver echotexture was changed into a heterogenous texture. Only 12% of patients were diagnosed with ascites and 27.8% with increased GB walls thickness. Conclusions: There was a notable link of portal hypertension with gender and age, as males of age between 50 – 59 years were commonly affected with this condition. Increased diameter of the portal and splenic vein, reduced liver size, splenomegaly, heterogeneous liver echotexture, ascites, and increased GB wall thickness were the common ultrasound findings in patients with portal hypertension.

A Comparison of Central Venous Access to the Internal Jugular Vein and Two Standard Approaches to the Subclavian Vein: A Study of Cross-Sectional Areas Using Computed Tomography Scans.

IntroductionThe supraclavicular approach to the subclavian vein has been cited as having many advantages to the infraclavicular approach, including a larger short-axis cross-sectional area, a greater margin of safety, and fewer complications.MethodsTo examine whether a larger short-axis cross-sectional area of the subclavian vein at the supraclavicular fossa is a potential explanation for the reduction in attempts with the supraclavicular approach seen in a previous study, we examined computed tomography scans from 50 patients (24 M, 26 F). The short-axis cross-sectional areas of the subclavian vein at the mid-clavicular line, the subclavian vein in the supraclavicular fossa, and the internal jugular vein at the level of the thyroid cartilage were calculated.ResultsThe internal jugular vein short-axis cross-sectional area was significantly larger than the subclavian vein short-axis cross-sections measured at each location. We found no difference between the short-axis cross-sectional areas of the subclavian vein or when comparing measurements as a factor of gender, age, or race. Weight had a significant relationship to the short-axis cross-sectional area of the internal jugular vein and subclavian vein at the mid-clavicular vein.ConclusionsOn supine computed tomographic imaging, the subclavian vein short-axis cross-section was not larger in the supraclavicular fossa than the mid-clavicular line. The short-axis cross-sectional area of the subclavian vein at the supraclavicular fossa does not appear to contribute to the decrease in attempts to access it. Weight, but not necessarily height, appears to be correlated with central vein size.

Assessment of variceal bleeding in cirrhotic patients: accuracy of multi-detector computed tomography

BackgroundEsophageal variceal hemorrhage (EVH) has been shown to be a leading cause of mortality in patients with portal hypertension. Our purpose was to assess the utility of multi-detector computed tomography (MDCT) features in the assessment of esophageal varices (EVs) and esophageal variceal hemorrhage (EVH). This prospective study included 85 cirrhotic patients who underwent MDCT and Upper Gastrointestinal Tract (UGIT) endoscopy within 2 weeks. Four radiologists evaluated the presence of EVs and the presence and size of different collaterals. Multivariable logistic regression analysis was calculated to investigate the significant predictors influencing EV and EVH.ResultsFindings of EV with MDCT were the best predictor of EV or EVH. The presence (and/or size) of following collaterals had significant association with both EV and EVH: paraesophageal (p < 0.001, < 0.001), short gastric (p = 0.024, 0.010), gastric varicosities (p < 0.001, < 0.001), coronary (p < 0.001, < 0.001), and main coronary vein (MCV) (p < 0.001, = 0.011). We proposed an imaging-based model (presence of coronary collaterals, main coronary vein size > 3.5 mm, presence of short gastric collaterals, presence of gastric varicosities, size > 1.5 mm) with 97% sensitivity, 91% specificity, and 94% accuracy to predict EVs. We suggested another model (presence of paraesophageal collaterals, presence of short gastric vein (SGC), SGC size > 2.5 mm, main coronary vein size > 3.5 mm, gastric varicosities size > 1.5 mm, size of EVs > 4 mm, and Child C score) to predict EVH with 98% sensitivity, 81% specificity, and 89.5% accuracy. Inter-observer agreement was high in the detection of EVs (W. Kappa = 0.71–0.88).ConclusionMDCT is an effective modality in the diagnosis of EVs. At MDCT, the presence and/or size of various collaterals including para-esophageal, short gastric, coronary collaterals, and gastric varicosities are accurate predictors for either EVs existence or EVH. We suggested two computed tomography imaging-based models with high reproducibility and acceptable accuracy for the prediction of EV and EVH. With cirrhotic patients, we recommend that radiologists report collaterals in their daily practice.

Predictive factors for re-bleeding of esophageal varices in hospitalized patients.

Bleeding due to esophageal varices is associated with high mortality and hospital costs. The incidence of morbidity and mortality can be reduced with appropriate treatment measures by identifying the predictors of re-bleeding at admission. Therefore, this study aimed to determine the risk factors for re-bleeding in hospitalized esophageal varices patients using factors included in the Child Turcotte Pugh (CTP) scoring system. In this cross-sectional study, 100 patients were evaluated for bleeding from esophageal varices. Some characteristics and variables were recorded, including age, gender, cause of disease, CTP classification score, and clinical, endoscopic, and laboratory findings. Patients were divided into two groups with and without bleeding from esophageal varices, and predictive factors were identified in both groups. Besides, a genetic predictor factor, i.e. plasminogen activator inhibitor type I (PAI-1), was evaluated by the Real-time PCR technique. Sixty-eight patients in the non-re-bleeding group with a mean age of 49.88 ± 16.42 years and 32 patients with a mean age of 54.22 ± 19.81 years were in the group with re-bleeding. Varicose vein size, encephalopathy, ascites, and CTP classification had a predictive effect on re-bleeding. Twelve people were in class A, 59 people in class B and 29 people in class C had CTP classification. The sensitivity of CTP, PAI-1 gene expression, and bilirubin in prediction through the ROC chart were calculated to be more than 85%, 61.4%, and 62%, respectively. In general, determining the degree and score of CTP at the time of referral of a patient with varicose hemorrhage provides valuable information on the risk of bleeding. Patients with class B CTP were strongly susceptible to re-bleeding in this study. Also, with increased bilirubin or ascites and more severe encephalopathy, the risk of bleeding is higher, and these people should be followed up.

The effect of left atrial wall thickness and pulmonary vein sizes on the acute procedural success of atrial fibrillation ablation

Nowadays, a novel contact-force guided ablation technique is used for enclosing pulmonary veins in patients with atrial fibrillation (AF). We sought to determine whether left atrial (LA) wall thickness (LAWT) and pulmonary vein (PV) dimensions, as assessed by cardiac CT, could influence the success rate of first-pass pulmonary vein isolation (PVI). In a single-center, prospective study, we enrolled consecutive patients with symptomatic, drug-refractory AF who underwent initial radiofrequency catheter ablation using a modified CLOSE protocol. Pre-procedural CT was performed in all cases. Additionally, the diameter and area of the PV orifices were obtained. A total of 1034 LAWT measurements and 376 PV area measurements were performed in 94 patients (mean CHA2DS2-VASc score 2.1 ± 1.5, mean age 62.4 ± 12.6 years, 39.5% female, 38.3% persistent AF). Mean procedure time was 81.2 ± 19.3 min. Complete isolation of all PVs was achieved in 100% of patients. First-pass isolation rate was 76% and 71% for the right-sided PVs and the left-sided PVs, respectively. No difference was found regarding comorbidities and imaging parameters between those with and without first-pass isolation. LAWT (mean of 11 regions or separately) had no effect on the acute procedural outcome on logistic regression analysis (all p ≥ 0.05). Out of all assessed parameters, only RSPV diameter was associated with a higher rate of successful right-sided first pass isolation (OR 1.01, p = 0.04). Left atrial wall thickness does not have an influence on the acute procedural success of PVI using ablation index and a standardized ablation protocol. RSPV diameter could influence the probability of right sided first-pass isolation.

Orbital Vascular Malformations: Determining Outflow with Valsalva Maneuver-Augmented Computed Tomography Angiography

Distensible orbital vascular malformations with direct outflow to the cavernous sinus tend to show a disproportionate increase in ipsilateral superior ophthalmic vein size on Valsalva CTA and are often located closer to the apex.

Analysis of Anastomotic Venous Factors in Traumatic Lower Extremity Injuries Reconstructed by Free Flap.

BackgroundVenous thrombosis has been shown to be the most frequent cause of free flap failure in traumatic lower extremity injuries. However, the roles of various anastomotic venous factors, including venous anastomosis (end-to-end (ETE) or end-to-side (ETS)), venous outflow (one vein or two veins), and recipient venous selection (deep or superficial vein), remain unclear. This retrospective study aims to investigate factors contributing to microvascular complications in patients with lower extremity Gustilo type IIIB/IIIC injuries reconstructed by free flap with a focus on the three abovementioned venous factors.MethodsA total of 44 flap treatment outcomes of 41 patients with these injuries from 2015 to 2020 were assessed according to the three venous factors (type of anastomosis, venous outflow, and vein selection).ResultsThe average patient age was 52 years, with the majority (75.6%) being male. Eight patients (18.2%) returned to the operating room due to venous thrombosis, and five patients (11.4%) experienced total flap failure. The following factors were suspected to have contributed to venous thrombosis: vein size mismatch (n = 2) and recipient vein insufficiency possibly due to post-traumatic vessel disease (PTVD) (n = 6). End-to-side (ETS) anastomoses showed lower venous thrombosis rates than end-to-end (ETE) anastomoses (6.3% versus 25%, p = 0.22), two-vein outflows had lower rates than one (8.3% versus 30%, p = 0.07), and deep veins had the lowest thrombosis rates (7.7%), whereas superficial veins had the highest (38.5%).ConclusionThe key venous factors in preventing venous thrombosis include using as many two-vein ETS anastomoses as possible to deep recipient veins.

Measuring the Size and Expansion of the Common Femoral Vein as A New Method of Detection and Stratification of Heart Failure

Heart Failure (HF) is on the end stage of the disease spectrum with many confounders and thus no specific symptoms and signs. There is a need for a test that can effectively confirm the diagnosis of volume overload in HF at its earliest to guide the initial approach and subsequent management. This study aimed to evaluate the effectiveness of a new test noted as the Size and Expansion of Femoral Vein (SEFV) in the diagnosis and management of patients with HF. This test was used specifically on asymptomatic patients or those who presented with severe comorbidities. The patients who arrived at the emergency room with a diagnosis of HF or suspected HF were enrolled. Ten patients without HF formed the control group. All patients received a standard physical examination (PE). The patients with the obvious diagnosis of HF by PE formed the HF control group. All patients with tentative diagnoses formed the HF study group. All patients underwent the ultrasound test to measure the size of the common femoral vein (CFV) and artery (CFA). The study enlisted 167 patients with HF or suspected HF. The results showed that the SEFV test was more accurate (98%) than the PE (54%). The SEFV test accurately differentiated between severely sick patients with intravascular overload and moderately sick patients with extravascular overflow. The test was accurate in patients with severe comorbidities (93%) or hypotension (100%). The SEFV test was more accurate in confirming the presence of fluid overload in patients with severe comorbidities or hypotension.

Jugular Foramen of Adult Human Skull and its Clinical Significance in Population of Eastern India: A Cross-sectional Study

Introduction: Jugular foramen is a complex irregular bony canal located at the base of the skull between the condylar part of occipital bone and petrous part of temporal bone. It allows passage of important nervous and vascular structures. These are ninth, tenth, eleventh cranial nerves, sigmoid sinus continued as the superior bulb of internal jugular vein and inferior petrosal sinus, meningeal branches of the ascending pharyngeal and occipital arteries. Jugular fossa has a septum and a dome. The dome lodges the superior bulb of internal jugular vein. The septum divides the foramen into two compartment, antero- medial and postero-lateral. There is a wide variation in shape, size and septation of jugular foramen in different regions of globe which have been studied by different authors in different periods of time. Many tumours may arise in this region causing compression of the vital structures passing through it. Surgery is the treatment of choice in these cases. Successful neuro surgeries involving this region require detailed knowledge about the anatomical variation of the jugular foramen. Aim: To study and compare the morphology of jugular foramen, its various dimensions, shape, size and septation which is related to the size of internal jugular vein. Materials and Methods: A cross-sectional descriptive study was carried out on 85 adult dry human skulls, collected from the Anatomy Department as well as from the first year Bachelor of Medicine and Bachelor of Surgery (MBBS) students of different Medical colleges of West Bengal from September 2020 to June 2021. Presence of septa were observed and anteroposterior (AP), mediolateral diameter (ML diameter) were measured by using vernier caliper. Then the area was calculated. Data collected were compiled in tabular form. They were analysed by using Statistical Package for Social Sciences (SPSS) statistics version 20.0 and paired t-test and chi-square tests were applied. Results: In the total 85 skulls studied, the area of jugular foramen was larger on right side in 91.76% and on left side in 8.24% of skull. The AP diameter was less than the ML diameter and areas in all cases. But both the diameters were significantly (p-value&lt;0.001) larger on right side than the left. Complete septation was present in right side of 34 foramina and in left side of 17 foramina. Partial or incomplete septation was present on right side of 51 foramina and left side of 68 foramina. Conclusion: The study revealed variation in shape, size and septation in different skulls and also bilateral variation in same skull. It has immense value to radiologists, Ear Nose Throat (ENT) surgeons, neuro-surgeons and radiologists who deal with the diagnosis and management of space occupying lesions surrounding the jugular foramen.

10-year experience of Paediatric varicocele embolization in a tertiary centre with long-term follow-up

Paediatric varicocele embolization has many benefits over surgical ligation, but lacks published long-term data. We investigated technical and clinical outcomes in this under reported patient group. To evaluate technical success, complications and recurrence rates following varicocele embolization in paediatric patients. A single-centre retrospective review of procedural data and electronic notes of consecutive patients referred for varicocele embolization over a 10-year period was performed (February 2010-March 2020). The primary outcomes were technical success and clinical efficacy (lack of symptom recurrence). Secondary outcomes included complications, testicular vein size reduction and procedural parameters including radiation exposure. Chi-square analysis was used to identify predictors of clinical success. Follow-up involved outpatient clinical assessment and telephone interview. 40 patients (median age 15) were referred for left-sided symptomatic varicocele. Technical embolization success was achieved in 36/40 patients (90%), with 4 procedures abandoned (inaccessible vein). Embolization technique was platinum-based coils±sclerosant. There were no immediate or long-term procedural complications. 32/36 patients completed short term follow-up at a median interval of 2.8 months. 30/32 (93.78%) experienced early clinical success. We found a significant reduction in peritesticular vein size following embolization (pre-3.70 vs post-2.56mm, p=0.00017) and a significant relationship between varicocele grade and early clinical success (χ2=4.2, p=0.04), but not pre-treatment peritesticular vein size (χ2=0.02, p=0.88). 33/36 patients completed long-term follow-up (median 4.2 years, range 0.36-9.9 years) producing a late clinical success rate of 93.9% (31/33). No post procedural complications including hydroceles were identified. This study demonstrates technical success, matching rates described in adult patients which is reassuring and in support of embolization in the younger patient cohort. More importantly, the overall clinical success rate is comparable with previous embolization studies. Reassuringly, all symptom recurrences occurred early in follow-up, and there is a cogent argument for a single follow-up appointment at this juncture. Our long-term average follow-up duration, primarily gained via telephone interview, exceeds other studies. Although our study has the longest follow-up for varicocele embolization in children, it is limited by a few patients being lost to early and long-term follow-up. This is a recognised issue faced by studies attempting to follow-up benign conditions with a high clinical success rate. Paediatric varicocele embolization is a successful alternative to surgical ligation, with no complications and good clinical outcomes over a long-term follow-up.

Outcomes of Autogenous Radiocephalic Versus Brachiocephalic Arteriovenous Fistula Surgery Based on Transit-Time Flowmeter Assessment: A Retrospective Study

Despite the better operative results of autogenous brachiocephalic arteriovenous fistula (BC-AVF), it is considered secondary to autogenous radiocephalic AVF (RC-AVF) failure. Here we compared the results of our multidisciplinary management protocol of BC-AVF versus RC-AVF. A total of 194 matched patients who requested autogenous BC-AVF or RC-AVF surgery between 2017 and 2019 were included in this retrospective study. All patients strictly adhered to our departmental perioperative management protocol for AVF surgery, including vessel status monitoring, exercise with or without a tourniquet, intraoperative flow assessment, and antiplatelet and anticoagulant medications. AVF function and patient status data were acquired from the electronic medical records, and the final evaluation was made via outpatient department visit or phone call in October 2020. Patients who underwent elective BC-AVF or RC-AVF (n=97 each) were included. The patient groups had similar preoperative clinical characteristics. Artery and vein sizes at the planned anastomosis site were larger in the BC-AVF group (P < 0.001). The mean intraoperative maximal flow rate was higher in the BC-AVF group (492.5 ± 186.9 mL/min) than in the RC-AVF group (307.3 ± 113.0 mL/min, P < 0.001). The simultaneously evaluated mean pulsatility index was 0.5 ± 0.2 in the BC-AVF group and 0.6 ± 0.2 in the RC-AVF group (P < 0.001). The median observation duration was 19.4 months (11.0‒31.3 months). The primary patency rate was higher in the BC-AVF group (88.7%) than in the RC-AVF group (62.9%, P < 0.001). Patency duration was similar between groups, and the primary patency maintenance duration was longer in the BC-AVF group. Three cases of cephalic arch stenosis were observed in the BC-AVF group, while no cases of arterial steal syndrome were observed during the indexed observation period. Mortality rates were 14.4% and 9.3% in the BC-AVF and RC-AVF groups, respectively (P=0.267), and the cause of death did not differ significantly between groups. For mortality, the estimated hazard ratio of RC-AVF over BC-AVF was 0.47 (95% CI, 0.19‒1.17, P=0.106) during the observation period. BC-AVF had good characteristics for hemodialysis without an increased risk of AVF related complications during a median 19-month observation period. BC-AVF did not feature high flow-related complications with the multimodal approach, including preoperative exercise, intraoperative flow assessment to guarantee an adequate flow rate, postoperative exercise, and medications.

A critical review of surgical strategies to minimise venous stenosis in arteriovenous grafts.

It is inevitable that complications arising from surgical procedures are ascribed to surgical technique, and this applies to venous stenosis (VS) in arteriovenous grafts. However, despite a wide range of cellular studies, computer modelling, observational series and clinical trials, there remains uncertainty on whether surgical technique contributes to VS. This article reviews evidence from basic science, fluid dynamics and clinical data to try and rationalise the main surgical options to modify the occurrence of venous stenosis. There is sufficient data from diverse sources to make recommendations on clinical practice (size of target vein, shape of anastomosis, angle of approach, distance from venous needling, trauma to the target vein) whilst at the same time this emphasises the need to carefully report the practical aspects of surgical technique in future clinical trials.

Leaf Vein Morphological Variation in Four Endangered Neotropical Magnolia Species along an Elevation Gradient in the Mexican Tropical Montane Cloud Forests.

Climatic variations influence the adaptive capacity of trees within tropical montane cloud forests species. Phenology studies have dominated current studies on tree species. Leaf vein morphology has been related to specific climatic oscillations and varies within species along altitudinal gradients. We tested that certain Neotropical broad leaf Magnolia species might be more vulnerable to leaf vein adaptation to moisture than others, as they would be more resilient to the hydric deficit. We assessed that leaf vein trait variations (vein density, primary vein size, vein length, and leaf base angle) among four Magnolia species (Magnolia nuevoleonensis, M. alejandrae, M. rzedowskiana, and Magnolia vovidesii) through the Mexican Tropical montane cloud forest with different elevation gradient and specific climatic factors. The temperature, precipitation, and potential evaporation differed significantly among Magnolia species. We detected that M. rzedowskiana and M. vovidesii with longer leaves at higher altitude sites are adapted to higher humidity conditions, and that M. nuevoleonensis and M. alejandrae inhabiting lower altitude sites are better adjusted to the hydric deficit. Our results advance efforts to identify the Magnolia species most vulnerable to climate change effects, which must focus priorities for conservation of this ecosystem, particularly in the Mexican tropical montane cloud forests.

Computing Z‐Score Equations for Clinical Use to Measure Fetal Umbilical Vein Size and Flow Using Six Independent Variables of Age and Size

Measurements of the umbilical vein diameter (UVD) and blood flow (mL/min) (UVF) have been demonstrated to be decreased in fetuses with growth restriction (FGR) using gestational age (GA) as the independent variable. However, no previous studies have used the biparietal diameter (BPD), head circumference (HC), abdominal circumference (AC), femur length (FL), and the estimated fetal weight (EFW) to create equations to be used for z-score computations when evaluating fetuses at risk foran abnormal UVD and UVF. Two hundred and forty normal fetuses between 20 and 40 weeks of gestation were examined in which the UVD and time averaged maximal velocity (TAMX) were measured from which the UVF, UVF/HC, UVF/AC, and UVF/kg were computed. Fractional polynomial regression analysis was used to compute z-score equations using the above independent variables. Thirty-six fetuses with abnormal growth of the AC were examined to test the validity of the equations. The UVD, TAMX, UVF, UVF/HC, and UVF/AC all increased with gestatonal age and fetal growth except for the UVF/kg, which decreased with age and growth. From the regression equations, two z-score calculators were created using an Excel spreadsheet that can be used in clinical practice. Abnormal measurements of the UVD, UVF, UVF/HC, UVF/AC, and UVF/kg were observed in the 36 study fetuses, 21 with an AC < 10th centile and 15 with an AC > 90th centile. Using the equations generated from this study and the z-score calculators provides a clinical tool to measure the size and flow of the umbilical vein that may have clinical implications.

Vessel diameter and close surveillance helps predict early patency in native arteriovenous fistulas.

Arteriovenous fistulas are the preferred method of vascular access for haemodialysis. Data suggests patency rates can be low and may be related to vessel diameters prior to creation. We use specific size criteria for fistula selection. We aimed to establish patency rates in relation to vessel size and whether other factors affect fistula patency. Consecutive patients undergoing radiocephalic (RCF) or brachiocephalic (BCF) creation between 2016 and 2018 were analysed. Preoperative arterial and venous diameters were collected. Six-week and six-month primary and secondary patency rates were analysed to establish any impact of vessel size on patency and re-intervention rates between groups. A univariate analysis was performed. Ninety four RCFs and 101 BCFs were created. Median artery and vein size for RCF were 2.7 and 3.0 mm respectively. For BCF, they were 4.6 and 4.3 mm respectively. At 6-weeks, overall satisfactory patency for RCF and BCF combined was 91.8%. 89.7% demonstrated primary patency; 2.1% secondary patency. At 6-months, overall patency was 78.7%; 58.5% demonstrated primary patency, 20.2% secondary patency. A univariate analysis, for both groups, revealed vein size was a significant predictor of overall satisfactory patency at 6-weeks, with larger veins more likely to remain patent (p = 0.025 RCF, p = 0.007 BCF). However, artery size was not predictive (p = 0.1 RCF, p = 0.5 BCF). At 6-months, neither artery nor vein diameter were predictive in either group. When comparing size of vessel based on fistula type, vessels used to create RCFs were smaller than those for BCFs (p < 0.001). RCFs were more likely to receive endovascular intervention or occlude when compared to BCFs (p = 0.014). Excellent patency and maturation rates can be achieved using fairly strict vessel size criteria. Vein size might be the more important predictor of early success. RCFs can be challenging due to smaller vessels, but maturation rates can be optimised by close surveillance and aggressive re-intervention.

Study on Bearing Mechanism of Split Grouting Pile Based on Finite Element Simulation

In order to realize the directional and controllable splitting of splitting grouting, the field grouting test was carried out. Using a new grouting pipe designed, the splitting direction and size of the branch vein are effectively controlled through the control of grouting pressure and grouting amount. In order to explore the bearing characteristics of split grouting pile and provide necessary parameters for the design of split grouting pile composite foundation in engineering practice, the field static load test and indoor geotechnical test of split grouting pile are designed, and the ultimate bearing capacity of single pile and necessary soil parameters are obtained. In order to make up for the limitations of field static load test, the three-dimensional finite element model of pile, soil and branch vein of split grouting pile is established by using the finite element analysis software ABAQUS. The finite element analysis results are compared with the measured values of field test, and the variation laws of pile shaft axial force, stress and displacement of branch vein at different depths, pile side friction, etc. are further explored, Through these changes, the interaction and load transfer mechanism between pile and soil are analyzed, which provides a reference for optimal design.