bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluation of coral reef carbonate production models at a global scale
Authors: Jones N. S. , Ridgwell A. , Hendy E. J.
Published: September 2014

Abstract. Calcification by coral reef communities is estimated to account for half of all carbonate produced in shallow water environments and more than 25% of the total carbonate buried in marine sediments globally. Production of calcium carbonate by coral reefs is therefore an important component of the global carbon cycle. It is also threatened by future global warming and other global change pressures. Numerical models of reefal carbonate production are essential for understanding how carbonate deposition responds to environmental conditions including future atmospheric CO2 concentrations, but these models must first be evaluated in terms of their skill in recreating present day calcification rates. Here we evaluate four published model descriptions of reef carbonate production in terms of their predictive power, at both local and global scales, by comparing carbonate budget outputs with independent estimates. We also compile available global data on reef calcification to produce an observation-based dataset for the model evaluation. The four calcification models are based on functions sensitive to combinations of light availability, aragonite saturation (Ωa) and temperature and were implemented within a specifically-developed global framework, the Global Reef Accretion Model (GRAM). None of the four models correlated with independent rate estimates of whole reef calcification. The temperature-only based approach was the only model output to significantly correlate with coral-calcification rate observations. The absence of any predictive power for whole reef systems, even when consistent at the scale of individual corals, points to the overriding importance of coral cover estimates in the calculations. Our work highlights the need for an ecosystem modeling approach, accounting for population dynamics in terms of mortality and recruitment and hence coral cover, in estimating global reef carbonate budgets. In addition, validation of reef carbonate budgets is severely hampered by limited and inconsistent methodology in reef-scale observations.
High-frequency monitoring of nitrogen and phosphorus response in three rural catchments to the end of the 2011–2012 drought in England
Authors: Outram F. N. , Lloyd C. E. M. , Jonczyk J. , Benskin C. McW. H. , Grant F. , Perks M. T. , Deasy C. , Burke S. P. , Collins A. L. , Freer J. , Haygarth P. M. , Hiscock K. M. , Johnes P. J. , Lovett A. L.
Published: September 2014

Abstract. This paper uses high-frequency bankside measurements from three catchments selected as part of the UK government-funded Demonstration Test Catchments (DTC) project. We compare the hydrological and hydrochemical patterns during the water year 2011–2012 from the Wylye tributary of the River Avon with mixed land use, the Blackwater tributary of the River Wensum with arable land use and the Newby Beck tributary of the River Eden with grassland land use. The beginning of the hydrological year was unusually dry and all three catchments were in states of drought. A sudden change to a wet summer occurred in April 2012 when a heavy rainfall event affected all three catchments. The year-long time series and the individual storm responses captured by in situ nutrient measurements of nitrate and phosphorus (total phosphorus and total reactive phosphorus) concentrations at each site reveal different pollutant sources and pathways operating in each catchment. Large storm-induced nutrient transfers of nitrogen and or phosphorus to each stream were recorded at all three sites during the late April rainfall event. Hysteresis loops suggested transport-limited delivery of nitrate in the Blackwater and of total phosphorus in the Wylye and Newby Beck, which was thought to be exacerbated by the dry antecedent conditions prior to the storm. The high rate of nutrient transport in each system highlights the scale of the challenges faced by environmental managers when designing mitigation measures to reduce the flux of nutrients to rivers from diffuse agricultural sources. It also highlights the scale of the challenge in adapting to future extreme weather events under a changing climate.
Infrastructure sufficiency in meeting water demand under climate-induced socio-hydrological transition in the urbanizing Capibaribe River basin – Brazil
Authors: Ribeiro Neto A. , Scott C. A. , Lima E. A. , Montenegro S. M. G. L. , Cirilo J. A.
Published: September 2014

Abstract. Water availability for a range of human uses will increasingly be affected by climate change, especially in the arid and semiarid tropics. The main objective of this study is to evaluate the infrastructure sufficiency in meeting water demand under climate-induced socio-hydrological transition in the Capibaribe River basin (CRB). The basin has experienced spatial and sectoral (agriculture-to-urban) reconfiguration of water demands. Human settlements that were once dispersed, relying on intermittent sources of surface water, are now larger and more spatially concentrated, which increases water-scarcity effects. Based on the application of linked hydrologic and water-resources models using precipitation and temperature projections of the IPCC SRES (Special Report: Emissions Scenarios) A1B scenario, a reduction in rainfall of 26.0% translated to streamflow reduction of 60.0%. We used simulations from four members of the HadCM3 (UK Met Office Hadley Centre) perturbed physics ensemble, in which a single model structure is used and perturbations are introduced to the physical parameterization schemes in the model (Chou et al., 2012). We considered that the change of the water availability in the basin in the future scenarios must drive the water management and the development of adaptation strategies that will manage the water demand. Several adaptive responses are considered, including water-loss reductions, wastewater collection and reuse, and rainwater collection cisterns, which together have potential to reduce future water demand by 23.0%. This study demonstrates the vulnerabilities of the infrastructure system during socio-hydrological transition in response to hydroclimatic and demand variabilities in the CRB and also indicates the differential spatial impacts and vulnerability of multiple uses of water to changes over time. The simulations showed that the measures proposed and the water from interbasin transfer project of the São Francisco River had a positive impact over the water supply in the basin, mainly for human use. Industry and irrigation will suffer impact unless other measures are implemented for demand control.
A scoring test on probabilistic seismic hazard estimates in Italy
Authors: Albarello D. , Peruzza L. , D'Amico V.
Published: September 2014

Abstract. Probabilistic estimates of seismic hazard represent a basic element for planning seismic risk reduction strategies and they are key elements of seismic regulation. Due to its importance, it is mandatory to select most effective estimates among the available ones. A possible empirical scoring strategy is described here and is applied to a number of time-independent hazard estimates available in Italy both at national and regional scale. Scoring is based on the comparison of outcomes provided by available computational models at a number of accelerometric sites where observations are available for 25 years. This comparison also allows identifying computational models providing outcomes that contrast observations and thus should be discarded. The analysis shows that most of hazard estimates so far proposed for Italy do not contrast with observations and some computational models perform significantly better than the others do. Furthermore, one can see that, at least locally, older estimates can perform better that the most recent ones. Finally, since the same computational model can perform differently depending on the region considered and on average return time of concern, no single model can be considered as the best performing one. This implies that time-by-time, the most suitable model must be selected by considering the specific problem of concern.
The structure of disaster resilience: a framework for simulations and policy recommendations
Authors: Edwards J. H. Y.
Published: September 2014

Abstract. In this era of rapid climate change there is an urgent need for interdisciplinary collaboration and understanding in the study of what determines resistance to disasters and recovery speed. This paper is an economist's contribution to that effort. It traces the entrance of the word "resilience" from ecology into the social science literature on disasters, provides a formal economic definition of resilience that can be used in mathematical modeling, incorporates this definition into a multilevel model that suggests appropriate policy roles and targets at each level, and draws on the recent empirical literature on the economics of disaster searching for policy handles that can stimulate higher resilience. On the whole it provides a framework for simulations and for formulating disaster resilience policies.
Biochar can be used to capture essential nutrients from dairy wastewater and improve soil physico-chemical properties
Authors: Ghezzehei T. A. , Sarkhot D. V. , Berhe A. A.
Published: September 2014

Abstract. Recently, the potential for biochar use to recapture excess nutrients from dairy wastewater has been a focus of a growing number of studies. It is suggested that biochar produced from locally available excess biomass can be important in reducing release of excess nutrient elements from agricultural runoff, improving soil productivity, and long-term carbon (C) sequestration. Here we present a review of a new approach that is showing promise for the use of biochar for nutrient capture. Using batch sorption experiments, it has been shown that biochar can adsorb up to 20–43% of ammonium and 19–65% of the phosphate in flushed dairy manure in 24 h. These results suggest a potential of biochar for recovering essential nutrients from dairy wastewater and improving soil fertility if the enriched biochar is returned to soil. Based on the sorption capacity of 2.86 and 0.23 mg ammonium and phosphate, respectively, per gram of biochar and 10–50% utilization of available excess biomass, in the state of California (US) alone, 11 440 to 57 200 tonnes of ammonium-N and 920–4600 tonnes of phosphate can be captured from dairy waste each year while at the same time disposing up to 8–40 million tons of excess biomass.
Evaluating the importance of surface soil contributions to reservoir sediment in alpine environments: a combined modelling and fingerprinting approach in the Posets-Maladeta Natural Park
Authors: Palazón L. , Gaspar L. , Latorre B. , Blake W. H. , Navas A.
Published: September 2014

Abstract. Soil in alpine environments plays a key role in the development of ecosystem services and in order to maintain and preserve this important resource, information is required on processes that lead to soil erosion. Similar to other mountain alpine environments, the Benasque catchment is characterised by temperatures below freezing that can last from November to April, intense rainfall events, typically in spring and autumn, and rugged topography which makes assessment of erosion challenging. Indirect approaches to soil erosion assessment, such as combined model approaches, offer an opportunity to evaluate soil erosion in such areas. In this study (i) the SWAT (Soil and Water Assessment Tool) hydrological and erosion model and (ii) sediment fingerprinting procedures were used in parallel to assess the viability of a combined modelling and tracing approach to evaluate soil erosion processes in the area of the Posets-Maladeta Natural Park (central Spanish Pyrenees). Soil erosion rates and sediment contribution of potential sediment sources defined by soil type (Kastanozems/Phaeozems; Fluvisols and Cambisols) were assessed. The SWAT model suggested that, with the highest specific sediment yields, Cambisols are the main source of sediment in the Benasque catchment and Phaeozems and Fluvisols were identified as the lowest sediment contributors. Spring and winter model runs gave the highest and lowest specific sediment yield, respectively. In contrast, sediment fingerprinting analysis identified Fluvisols, which dominate the riparian zone, as the main sediment source at the time of sampling. This indicates the importance of connectivity as well as potential differences in the source dynamic of material in storage versus that transported efficiently from the system at times of high flow. The combined approach enabled us to better understand soil erosion processes in the Benasque alpine catchment, wherein SWAT identified areas of potential high sediment yield in large flood events but sediment fingerprinting identified areas that, due to high connectivity, contribute more to channel-stored sediment deposits.
Lamellar Corneal Lenticule Graft to Treat Keratolysis after Alphacor Keratoprosthesis Implantation
Authors: Hoffart Louis , Carles Gérard , Matonti Frédéric
Published: September 2014

Purpose

Clinical assessment of AlphaCor keratoprosthesis and evaluation of surgical method to treat keratolysis in case of stromal necrosis occurrence.

Methods

This is a noncomparative, retrospective, interventional case series. The medical records of 12 eyes of 12 patients who underwent consecutive AlphaCor keratoprosthesis implantations were reviewed. Patients with severe bilateral corneal pathology unsuitable for a conventional corneal graft, a best-corrected visual acuity (BCVA) from light perception (LP) to 20/200, with no active ocular surface inflammation, controlled intraocular pressure prior to the surgery, and an unstimulated Schirmer test of >2.5 mm at 5 minutes were included. Postoperative medications included topical dexamethasone, ciprofloxacin, and 2% cyclosporine A. Main outcome measures included BCVA and complications occurrence.

Results

After a mean follow-up of 25 ± 12.3 months (range 2-38 months), 8 (66.7%) AlphaCor devices were retained. Postoperative BCVA ranged from LP to 20/63 (mean gain of 2.5 ± 3.1 lines). Seven cases of stromal melt (58.3%) occurred. Three were reversed to penetrating keratoplasty and 3 had a donor corneal layer fixated over the AlphaCor with satisfactory results (mean follow-up 23 ± 1.6 months). There were no instances of endophthalmitis, retinal detachment, or glaucoma exacerbation.

Conclusions

AlphaCor showed a low incidence of the classic keratoprosthesis complications but a high occurrence of recipient cornea necrosis. Corneal melts were successfully managed in 3 cases by lamellar corneal lenticule graft, thereby increasing the retention of AlphaCor and maintaining BCVA.
Comparison of Primary Open-Angle Glaucoma and Exfoliation Glaucoma at Diagnosis
Authors: Tarkkanen Ahti H.A. , Kivelä Tero T.
Published: September 2014

Purpose

To compare ocular findings in eyes with primary open-angle glaucoma (POAG) and exfoliation glaucoma (EG) at the time of diagnosis when identical diagnostic criteria for glaucoma were applied.

Methods

We conducted a study on records of 519 consecutive, unselected patients with chronic glaucoma filing for cost-free medication from the Finnish National Social Insurance Institute (FSII). Fourteen cases were excluded for having other types of glaucoma. The documents were provided by eye hospitals or by licensed ophthalmologists. The criteria for glaucoma were set by the Parliament of Finland and applied by FSII. A total of 329 patients had POAG and 176 had EG. The main outcome measures were best-corrected visual acuity (BCVA), intraocular pressure (IOP), cup-to-disc ratio of the optic nerve head (C/D), and glaucomatous changes of the visual fields (VF).

Results

As regards sex, the 2 groups were comparable: 66% female with POAG and 68% with EG. The EG patients were older (mean ± SD 74 ± 8.6 years) vs POAG (68 ± 11.4 years). The EG eyes had slightly lower BCVA. The POAG eyes had mean intraocular pressure (IOP) 24 ± 5.4 mm Hg. A total of 12% in this group had highest IOP of less than 18 mm Hg (low-tension glaucoma [LTG]) but there were none of EG. All EG eyes had a mean IOP 28.3 ± 9.3 mm Hg. Among EG patients, 26% had unilateral disease, with a mean IOP of 33.7 ± 8.7 mm Hg, while the opposite eyes had a mean of 19 ± 3 mm Hg. There was not much difference in the C/D ratios of POAG and EG eyes and the VF profiles were similar.

Conclusions

At diagnosis, patients with EG were older than those with POAG and had higher mean IOP values. Among patients with POAG, there were 12% with LTG, but none among EG. A total of 26% among EG had unilateral disease with marked IOP asymmetry. The C/D and VF profiles were similar because the patients had been seen early in the disease course. Early recognition and lifelong most effective therapy of EG are strongly advocated.
Effect of the Blue Filter Intraocular Lens on the Progression of Geographic Atrophy
Authors: Pipis Antonios , Touliou Eftychia , Pillunat Lutz E. , Augustin Albert J.
Published: September 2014

Purpose

To clinically evaluate the effect of blue light–filtering intraocular lenses (IOLs) on disease progression in patients with geographic atrophy (GA).

Methods

Clinical data from 66 eyes of 40 patients were investigated, 27 with a blue filter and 39 with a non–blue filter IOL. Spectral-domain optical coherence tomography technology and the advanced retinal pigment epithelium analysis software tool were used to measure lesion size and monitor its progression over 1 year.

Results

The mean and median baseline area of GA for the total sample was 5.55 ± 4.72 mm2 and 4.40 mm2, respectively. There was a statistically significant difference of the mean (p = 0.0002) and median (p<0.0001) GA progression in 1 year between the blue filter and non–blue filter IOL group (0.72 ± 0.39 SD mm2 mean and 0.70 mm2 median compared to 1.48 ± 0.88 SD mm2 and 1.30 mm2, respectively).

Conclusions

The clinical data strongly support a photoprotective role of blue light–filtering IOLs on the progression of the atrophic form of dry age-related macular degeneration after cataract surgery.
Trochanteric Bursitis: The Last Great Misnomer
Authors: Board Tim N. , Hughes Simon J. , Freemont Anthony J.
Published: September 2014

Trochanteric bursitis has been used as a general term to describe pain around the greater trochanteric region of the hip. We hypothesised that trochanteric bursitis may not however have an inflammatory component and that accordingly, bursal inflammation has no role in lateral hip pain. This study was designed to test this hypothesis. Patients undergoing primary total hip replacement were enrolled in this prospective, case-controlled, blinded study. Twenty-five patients who met the criteria for diagnosis of trochanteric bursitis (group A) were matched with a control group of 25 patients (group B). Trochanteric bursal samples were harvested from all patients intraoperatively and sent for histological analysis for the presence of inflammation. The intraoperative appearance of the abductor tendon insertion was also noted. None of the samples showed any evidence of acute or chronic inflammatory changes. Intraoperatively, five patients (20%) in group A were noted to have thinning of the gluteus medius tendon but no macroscopic tendon tears were detected in any bursal samples. This study suggests that there is no inflammatory component to so-called trochanteric bursitis, which accordingly casts doubt on both the terminology and the existence of this condition as a separate clinical entity. Clinicians should search for an alternative cause of symptoms in such cases.
Cemented ABG-II Prosthesis: 5-Year Results
Authors: Krismer Martin , Nogler Michael , Huber Dennis , Oberaigner Wilhelm
Published: September 2014

Purpose

ABG II - cemented anatomic stems share their geometry and instrumentation with the uncemented version and provide a promising concept. This study compares a consecutive series of cemented ABG IIs to a pool of all other implants used during the same observation period at the institution of the authors.

Methods

This retrospective study is based on data from our regional hip arthroplasty register. The results of 141 cases with ABG II prosthesis were compared to those of 2,315 cases that were operated during the same period of time and reported in the regional arthroplasty registry. Survival was calculated using the Kaplan Meier method.

Results

The patients with cemented ABG II had a significantly worse preoperative WOMAC sum score and WOMAC domains, and similar ameliorated results as the control group at 1-year follow-up. The 5-year revision rate of the ABG II compares well to the 5-year revision rate of the controls in this study.

Conclusions

Revision rate and health related, quality of life, of cases with cemented ABG prosthesis are similar to those of a register based control group.
Preserving Arteriovenous Fistula Outcomes during Surgical Training
Authors: McGrogan Damian G. , Maxwell Alexander P. , Inston Nicholas G. , Krishnan Hari , Field Mel
Published: September 2014

Purpose

Arteriovenous fistulae (AVFs) are the preferred option for vascular access, as they are associated with lower mortality in hemodialysis patients than in those patients with arteriovenous grafts (AVGs) or central venous catheters (CVCs). We sought to assess whether vascular access outcomes for surgical trainees are comparable to fully trained surgeons.

Methods

A prospectively collected database of patients was created and information recorded regarding patient demographics, past medical history, preoperative investigations, grade of operating surgeon, type of AVF formed, primary AVF function, cumulative AVF survival and functional patency.

Results

One hundred and sixty-two patients were identified as having had vascular access procedures during the 6 month study period and 143 were included in the final analysis. Secondary AVF patency was established in 123 (86%) of these AVFs and 89 (62.2%) were used for dialysis. There was no significant difference in survival of AVFs according to training status of surgeon (log rank x2 0.506 p=0.477) or type of AVF (log rank x2 0.341 p=0.559). Patency rates of successful AVFs at 1 and 2 years were 60.9% and 47.9%, respectively.

Conclusion

We have demonstrated in this prospective study that there are no significant differences in outcomes of primary AVFs formed by fully trained surgeons versus surgical trainees. Creation of a primary AVF represents an excellent training platform for intermediate stage surgeons across general and vascular surgical specialties.
A Prospective, Randomized Comparison of three different types of Valved and Non-Valved Peripherally inserted Central Catheters
Authors: Pittiruti Mauro , Emoli Alessandro , Porta Patrizia , Marche Bruno , DeAngelis Rosa , Scoppettuolo Giancarlo
Published: September 2014

Purpose

Few randomized studies have investigated the impact of valved and non-valved power-injectable peripherally inserted central catheters (PICCs) in terms of incidence of occlusion, infection, malfunction and venous thrombosis.

Methods

We have prospectively compared three types of third-generation polyurethane PICCs. One hundred and eighty adult patients candidate to chemotherapy were randomized into three groups: power-injectable PICCs with Solo-2 proximal valve (Bard); power-injectable PICCs with PASV (Pressure Activated Safety Valve) proximal valve (Navilyst); and non-valved power-injectable PICCs (Medcomp). All PICCs were single lumen 4Fr, inserted according to a well-defined protocol - maximal barrier precautions, ultrasound guidance, intracavitary electrocardiography (IC-ECG), and so on - and managed according to the recommendations of the most recent guidelines (antisepsis with 2% chlorhexidine, transparent dressing, sutureless device, strict ‘scrub the hub’ policy, neutral displacement needle-free connectors and so on). All catheters were flushed with 10 ml saline before and after each infusion, or with 20 ml saline after blood sampling or infusion of blood products. No heparin was used.

Results

We detected no complications at insertion; no PICC-related bloodstream infections; no dislocations; five cases of transient occlusion and two cases of persistent withdrawal occlusion, evenly distributed among the groups; one episode of complete irreversible obstruction (group A); four episodes of asymptomatic peripheral venous thrombosis; one episode of symptomatic, severe central vein thrombosis (group B). In 31% of PICCs in group A (19/61) and in 65% of group B (39/60), difficulties with gravity infusion were reported; three PICCs of group A were complicated by rupture of the intravascular tract during pump infusion. Five PICCs were removed because of complications, four in group A (one obstruction; three ruptures) and one in group B (central venous thrombosis).

Conclusion

We found no clinical advantages of valved vs. non-valved PICCs.
The Intracavitary ECG Method for Positioning the Tip of Central Venous access Devices in Pediatric Patients: Results of an Italian Multicenter Study
Authors: Rossetti Francesca , Pittiruti Mauro , Lamperti Massimo , Graziano Ugo , Celentano Davide , Capozzoli Giuseppe
Published: September 2014

Purpose

The Italian Group for Venous Access Devices (GAVeCeLT) has carried out a multicenter study investigating the safety and accuracy of intracavitary electrocardiography (IC-ECG) in pediatric patients.

Methods

We enrolled 309 patients (age 1 month-18 years) candidate to different central venous access devices ( VAD) - 56 peripherally inserted central catheters (PICC), 178 short term centrally inserted central catheters (CICC), 65 long term VADs, 10 VADs for dialysis - in five Italian Hospitals. Three age groups were considered: A (<4 years, n = 157), B (4-11 years, n = 119), and C (12-18 years, n = 31). IC-ECG was applicable in 307 cases. The increase of the P wave on IC-ECG was detected in all cases but two. The tip of the catheter was positioned at the cavo-atrial junction (CAJ) (i.e., at the maximal height of the P wave on IC-ECG) and the position was checked during the procedure by fluoroscopy or chest x-ray, considering the CAJ at 1-2 cm (group A), 1.5-3 cm (group B), or 2-4 cm (group C) below the carina.

Results

There were no complications related to IC-ECG. The overall match between IC-ECG and x-ray was 95.8% (96.2% in group A, 95% in group B, and 96.8% in group C). In 95 cases, the IC-ECG was performed with a dedicated ECG monitor, specifically designed for IC-ECG (Nautilus, Romedex): in this group, the match between IC-ECG and x-ray was 98.8%.

Conclusions

We conclude that the IC-ECG method is safe and accurate in the pediatric patients. The applicability of the method is 99.4% and its feasibility is 99.4%. The accuracy is 95.8% and even higher (98.8%) when using a dedicated ECG monitor.
Association between Multiple IV attempts and Perceived Pain levels in the Emergency Department
Authors: Fields J. Matthew , Piela Nicole E. , Ku Bon S.
Published: September 2014

Purpose

Intravenous (IV) access is the most commonly performed procedure in the emergency department (ED). Patients with difficult venous access require multiple needlesticks (MNS) for successful IV cannulation and may experience increased pain with many attempts.

Objective

To determine the association between number of IV attempts and overall pain experienced by the patient from IV placement.

Methods

Cross-sectional observational study on consecutive patients undergoing IV placement with a 20-gauge IV in the upper extremity in an urban academic hospital. Exclusion criteria included refusal to participate or fully complete all survey questions. The total number of IV attempts and patient pain scores marked on a standardized visual analog scale was recorded. Mean pain scores of two groups, single needlestick (SNS) and MNS, were compared using Student's t-test.

Results

A total of 760 patients were approached, of whom 31 were excluded, leaving 729 patients in the analysis; 556 with SNS (76%) and 173 with MNS (24%). The mean pain score (95% CI) was 51 mm (46–55 mm) for the MNS group and 25 mm (23–28 mm) for the SNS group, p<0.001. Compared to patients who underwent one IV attempt, patients with two and three attempts had an average 19 mm and 33 mm increase in pain scores, respectively, with the highest average pain associated with five attempts. A total of 58% of MNS patients rated IV placement as the most painful experience while in the ED.

Conclusions

Patients experience increased pain in association with multiple IV attempts.
Novel Modular Anastomotic Valve Device for Hemodialysis Vascular Access: Preliminary Computational Hemodynamic Assessment
Authors: McNally Andrew , Akingba A. George , Robinson Eric A. , Sucosky Philippe
Published: September 2014

Purpose

Arteriovenous graft patency is limited by terminal occlusion caused by intimal hyperplasia (IH). Motivated by evidence that flow disturbances promote IH progression, a modular anastomotic valve device (MAVD) was designed to isolate the graft from the circulation between dialysis periods (closed position) and enable vascular access during dialysis (open position). The objective of this study was to perform a preliminary computational assessment of the device ability to normalize venous flow between dialysis periods and potentially limit IH development and thrombogenesis.

Methods

Computational fluid dynamics simulations were performed to compare flow and wall shear stress (WSS) in a native vein and MAVD prototypes featuring anastomotic angles of 90° and 30°. Low WSS (LWSS) regions prone to IH development were characterized in terms of temporal shear magnitude (TSM), oscillatory shear index (OSI), and relative residence time (RRT). Thrombogenic potential was assessed by investigating the loading history of fluid particles traveling through the device.

Results

The closed MAVD exhibited the same flow characteristics as the native vein (0.3% difference in pressure drop, 3.5% difference in surface-averaged WSS). The open MAVD generated five LWSS regions (TSM <0.5 Pa) exhibiting different degrees of flow reversal (surface-averaged OSI: 0.03–0.36) and stagnation (max RRT: 2.50–37.16). Reduction in anastomotic angle resulted in the suppression of three LWSS regions and overall reductions in flow reversal (surface-averaged OSI <0.21) and stagnation (max RRT <18.05).

Conclusions

This study suggests the ability of the MAVD to normalize venous flow between dialysis periods while generating the typical hemodynamics of end-to-side vein-graft anastomoses during dialysis.
Mechanical Properties of Seldinger Guidewires
Authors: Schummer Wolfram , Trommer Sabine , Kleemann Frieder , Schummer Claudia
Published: September 2014

Background

Almost all central venous catheters are placed using the Seldinger technique. Despite the introduction of ISO 11070 in 1998, we continue to see mechanical wire failures and their associated complications.

Methods

Seven different wire types were tested regarding their tensile strength and eight different types for their flexing performance. For each wire type six wires were assessed. Tensile strength was examined using the test method described in ISO 11070, but the test did not end at 10 N. For flexing performance testing a new apparatus, closely mimicking clinical requirements, was designed. Wires were scanned digitally after testing for measurement and analysis.

Results

All wire types tested, except one, consistently met ISO 11070 requirements for 10 N tensile strength. The maximum tension the wires were able to withstand ranged from 15.06 N to 257.76 N. None of the wires kinked. The monofil wires had no evidence of bending. Two core and coil wires displayed minor bending (angle 1.5°). All other wires displayed bending angles between 22.5° and 43.0°. The degree of bending was also dependent on the angle between the dilator and wire.

Conclusion

The mechanical properties of different types of guidewires show considerable differences, not detected with current ISO 11070 based testing. Uncovering those may allow set up of clinical trials to examine whether regular use of wires with high-end mechanical properties could reduce CVC insertion-related complication rates.
External Jugular Vein Approach for TIVAD Implantation: First Choice or Only an Alternative? A Review of the Literature
Authors: Iorio Olga , Cavallaro Giuseppe
Published: September 2014

Purpose

Totally implantable venous access devices (TIVADs) can be implanted by percutaneous approach (to the subclavian or internal jugular vein) or by surgical approach, through cephalic vein or external jugular vein (EJV). The authors present a review of the literature about EJV approach for TIVAD implantation.

Methods

A review of articles indexed in MEDLINE (PubMed) and Cochrane Central Register on “EJV access,” “EJV cut-down,” and “TIVADs” was performed, even matching the terms. We gathered articles from papers quoting patient number, specialist involved, number of devices implanted, site and technique of implantation and complications.

Results

A total of 1,308 TIVAD implantations through EJV have been reported, with a success rate ranging from 73.7% to 100% and a complication rate up to 13%. Only in 4 on 10 series reported (with more than 15 procedures) the EJV approach was the first choice, while in the other 6 series this approach was the alternative after failure of other approaches.

Conclusions

Despite the lack of consistent series and prospective studies comparing EJV with other approaches, data present in the literature may support the evidence that EJV approach for TIVAD implantation is safe and effective, and may be considered as the first approach in selected patients.
Transjugular Tunnelled Dialysis Catheter Tip Placement into the Inferior Vena Cava Upper Segment after Length Overestimation
Authors: Renaud Claude J. , Seow Ying Ying , Teh Hui Siong
Published: September 2014

Purpose

The right atrium is preferred over the superior vena cava (SVC) for tunnelled dialysis catheter (TDC) tip placement as it offers the best compromise between optimal catheter performance and complications. However, clinical practice guidelines are not all unanimous on this as a universal recommendation. Right atrial tip placement may also fail due to variations in body surface area, venous anatomy or TDC designs and lengths. Moreover, the presence of recurrent long intra-cardiac fibrin sheath or cardiac rhythm management device leads serves as contraindications. Extra-cardiac tip placement in the azygous, hepatic veins and lower segment of the inferior vena cava (IVC) is an alternative but is invariably associated with poor blood flow and shortened patency.

Methods

We report the concept of extra-cardiac tip placement into the larger calibre hepatic segment IVC via a transjugular approach in two diabetic haemodialysis patients with overestimated TDC length out of 380 insertions.

Results

Blood flow was maintained above 250 ml/min for 5-6 months and no tip migration ensued.

Conclusions

The IVC upper segment is a reliable site for extra-cardiac tip placement in select cases but its safety and efficacy need to be further studied in larger clinical trials.
Ankle Fistula as the Last Resort for Vascular Access: Case Report and Literature Review
Authors: Goh Mingzheng A. , Ali Jason M. , Lagaac Regin , Pettigrew Gavin J.
Published: September 2014

Purpose

For the majority of patients with end-stage renal failure, renal replacement therapy in the form of dialysis offers the only means of life prolongation. Survival times on haemodialysis have improved, and consequently, patent vascular access is required for an increasing period of time. Upper extremity options for arteriovenous placement are increasingly being exhausted, leading to creation of fistulae in the lower extremities.

Methods

We describe the management of a patient with superior vena cava obstruction requiring haemodialysis in whom venous access options were becoming very limited. An ankle fistula was formed by anastomosing great saphenous vein (GSV) to dorsalis pedis.

Conclusion

The long-term patency of lower limb fistulae remains unclear. An ankle fistula preserves precious venous capital in patients who have no remaining options in the upper extremities for haemodialysis access. Furthermore, it allows for proximal revision if necessary. This serves to prolong the time spent dialysing through native fistulae, with their reduced complications and greater cost-effectiveness.
Donor Artery Aneurysm Formation following the Ligation of Haemodialysis Arteriovenous Fistula: A Systematic Review and Case Reports
Authors: Kordzadeh Ali , Barbara Raquel M. D'Espiney , Ahmad Ali S. , Hanif Muhammad A. , Panayiotopoulos Yiannis P.
Published: September 2014

Purpose

The purpose of this study is to investigate the pathogenesis, presentation and diagnosis of donor artery aneurysm formation following arteriovenous fistula (AVF) ligation and reach a consensus on their management.

Methods

A systematic review of literature in Ovid, MedLine, Embase, Scopus and CINHAL in the English language from 1951 to 2014 was performed. This was accompanied by two case reports. A total of 12 articles with 23 case reports were identified. Variables including patient's demographics, signs, symptoms, fistula type, duration of fistula use, time to aneurysm formation, renal transplantation, diagnostic modality, aneurysm type and size, type of surgery and outcome were reviewed.

Results

The data demonstrate a male predominance (5:1) and a median age of 47 years (range, 27-75 years). The median duration of access was 54 months (range, 6-300 months). The median time from ligation to aneurysm was 120 months (range, 6-280 months). The commonest aneurysm was of the brachial artery (BA, n = 21, 84%). The commonest type of AVF was radiocephalic (n = 15, 60%) followed by brachiocephalic AVF (n = 9, 36%). The management of choice was aneurysmectomy followed by interposition vein grafting (n = 12, 50%) with a median reported patency of 12 months (range, 1-38 months). This was followed by polytetrafluoroethylene (PTFE) grafting (n = 6, 25%) with a median reported patency of 6 months (range, 1-48 months).

Conclusions

The pathogenesis of donor artery aneurysms remains contentious. This review suggests that duplex is the investigative modality of choice and aneurysmectomy with interposition grafting is preferred over bypass.
Hemodialysis Vascular access Construction in the Upper Extremity: A Review
Authors: Lew Susie Q. , Nguyen Bao-Ngoc , Ing Todd S.
Published: September 2014

Purpose

This article reviews the conventional vascular access types in the upper extremities for hemodialysis.

Methods

We performed a literature search for autogenous arteriovenous fistula in the upper extremities.

Results

The upper extremities have four potential sites: radio-cephalic or radio-basilic transposition in the forearm, and brachio-cephalic or brachio-basilic transposition in the upper arm. A pre-operative Duplex ultrasound provides valuable information regarding arterial inflow and venous outflow. The surgical approach to fistula formation and final product depends on vein diameter and length as well as proximal vein patency. The discussion focuses on access outcomes and management of common complications.

Conclusions

The upper extremity arteriovenous fistula is the preferred access for hemodialysis. A number of arteriovenous fistulas can be created in the upper extremities. The Duplex ultrasound identifies suitable arteries and veins for successful arteriovenous hemodialysis fistula creation. Arteriovenous hemodialysis fistula has the best long-term patency outcomes and the lowest associated morbidity and mortality. Early detection and intervention can save the fistula when complications occur.
A comparison of Infections and Complications in Central Venous Catheters in Adults with Solid Tumours
Authors: Coady Karin , Ali Mohammed , Sidloff David , Kenningham Richard R. , Ahmed Samreen
Published: September 2014

Aim

The aim of this study is to compare the complication rates of three vascular access devices in patients with solid tumours having infusion chemotherapy.

Materials and Methods

An observational study of 58 central venous catheter (CVC) lines inserted in 55 patients with solid tumours requiring infusional chemotherapy was performed. The study was conducted between January 2011 and August 2013, looking at complication and infection rates as primary outcomes. Data were recorded from patients with 19 tunnelled cuffed silicone catheters, nine with peripherally inserted central catheters (PICCs) and 30 central venous ports.

Results

The two CVC groups (ports and non-ports) matched equally in terms of tumour site; all patients with solid tumours were included, haematology patients were excluded and chemotherapy regimens were comparable. Thirteen out of 28 non- ports had complications compared with one out of 30 central venous ports. Ten out of 19 tunnelled catheters had complications including three displacements and seven were removed due to infection. There were no reports of line-related sepsis in the PICC or ports. Three out of nine PICC lines had complications including two displacements and one PICC blocked permanently requiring removal. In addition, one port out of 30 was removed due to erosion through the skin. There were no episodes of thrombosis or fibrin sheath formation related to any of the devices.

Conclusions

In our study, we demonstrated that central venous ports and PICC lines in patients undergoing infusional chemotherapy had lower line infection rates than tunnelled catheters, and only ports have been shown to be almost complication-free. In addition, we found infection rates higher in CVCs s cared for by patient/carers rather than hospital only care, and higher in colorectal patients with stomas. Therefore, we recommend that central venous ports are a safe, acceptable CVC option for infusional chemotherapy for adults with solid tumours.
Chronic Hemodialysis Access-Induced Distal Ischemia (HAIDI): Distinctive form of a Major Complication
Authors: Modaghegh Mohammad-Hadi Saeed , Kazemzadeh Gholamhossein , Rad Masoud Pezeshki , Ravari Hassan , Hafezi Shahab , El-Husheimi Alaa , Barzanouni Amir
Published: September 2014

Purpose

Hemodialysis access-induced distal ischemia (HAIDI) is an uncommon but potentially devastating complication. HAIDI is classified as acute, subacute and chronic based upon the time of onset. The aim of this study was to determine the prevalence, severity, patients’ characteristics and the underlying etiologic mechanism of chronic HAIDI using color Doppler ultrasonography (CDUS).

Methods

Between June and August 2010, 676 hemodialysis patients with arteriovenous access (AVA) were evaluated for clinical evidence of chronic HAIDI. In the case–control part of the study, CDUS findings were compared between ischemic patients and asymptomatic matched controls. Also, patients with chronic HAIDI were followed up until February 2014, access ligation, kidney transplantation or death.

Results

Eighteen chronic HAIDI patients were diagnosed (2.66%). Cold hand and cold sensation were the most common signs and symptoms of hand ischemia, respectively. Fifteen patients were classified in stage 1. Patients with proximal autogenous arteriovenous fistula, younger age, more previous AVAs and less access age were more likely to develop chronic HAIDI. Excessive fistula flow was found in the majority of ischemic patients (83.3%). The mean fistula flow was significantly higher in cases compared to controls (p=0.001). Eleven patients with chronic HAIDI were successfully treated by conservative measures alone until the end of follow-up ( n=3), kidney trans-plantation ( n=4) or death ( n=4).

Conclusions

CDUS is a useful adjunctive diagnostic tool to determine the etiology of chronic HAIDI. Conservative measures combined with close follow-up can be used as the first step in the management of chronic HAIDI patients with mild symptoms.
Predicting Outcomes in Native AV Forearm Radio-cephalic Fistulae; the CAVeA2T2 Scoring System
Authors: Bosanquet David C. , Rubasingham Jeffrey , Imam Mariam , Woolgar Justin D. , Davies Christopher G.
Published: September 2014

Purpose

The aim of this study was to identify significant factors relating to fistula survival and create an easy-to-use scoring system for predicting fistula patency rates.

Methods

A total of 276 consecutive radio-cephalic forearm fistulae created in a single tertiary vascular unit were identified retrospectively. Numerous patient- and fistula-related demographics were noted. Cox regression analysis was used to identify significant factors predictive of reduced fistula patency rates, and significant variables weighted according to their hazard ratio.

Results

Five significant factors were identified: ipsilateral Central venous access, Age >73 years, anastomosed Vein <2.2 mm, previous lower limb Angioplasty and absent intraoperative Thrill (1 point for first three variables, 2 points for the latter two). The CAVeA2T2 score (maximum 7 points) significantly predicted for reduced fistula patency (p = 0.001) and a reduced rate of successful dialysis (p = 0.001). Fistulae with CAVeA2T2 scores ≥2 had 6 week and 1 year patency rates significantly below pooled published rates. Without scoring for thrill, that is in the pre-operative setting, the scoring system remained significant at all stages.

Conclusion

The CAVeA2T2, scoring system is a potential scoring system for predicting fistula patency rates and the likelihood of dialysing through a fistula. Further studies and/or external validation is required in the context of methodological limitations. How to manage patients with a high CAVeA2T2 score is unknown.
Percutaneous Retrieval of PICC Fractures via the Femoral Vein in Six Cancer Patients
Authors: Wang Qi , Xiong Bin , Zheng ChuanSheng , Feng GanSheng , Liang Ming , Liang HuiMin
Published: September 2014

Purpose

To investigate the feasibility and safety of the interventional technique of retrieving the fractured peripherally inserted central catheter (PICC) segments within the vessels via the femoral vein.

Methods

From July 2007 to January 2012, we performed percutaneous retrieval of PICC fractures in six cancer patients who accepted chemotherapy via PICC. The fractures occurred during the traction of the catheter and were diagnosed with chest plain film radiography and/or computed tomography. The patients included four cases of ovarian cancer, one case of breast cancer and one case of cervical cancer. The fractures were retained in the vessels of the patients for 1 to 10 days. According to the location of the ends of the PICC fractures, three methods were employed using the most commonly used interventional devices in the digital subtraction angiography suite.

Results

The PICC fractures were located in the subclavian vein, superior vena cava, right atrium, right ventricle or pulmonary arteries. During the procedures, a goose neck snare, pigtail catheter and stone basket catheter were used individually or in combination. The PICC fractures were removed successfully in all six patients via unilateral or bilateral femoral vein access. No major complications occurred during the operation or the follow-up period of 7 to 10 days.

Conclusions

Via femoral vein access, PICC fractures could be removed with common interventional instruments such as a goose snare, basket catheter and pigtail catheter. The interventional retrieval is a safe, convenient and minimally invasive method for the removal of PICC fractures.
Retroperitoneoscopic Renal Biopsy: Still a Good Indication!
Authors: Micali Salvatore , Dandrea Matteo , De Carne Cosimo , Martorana Eugenio , De Stefani Stefano , Cappelli Gianni , Bianchi Giampaolo
Published: September 2014

The histological evaluation of the renal parenchyma is often essential in cases of several renal diseases and provides useful information in determining the prognosis and guiding treatment. In patients with contraindications to percutaneous kidney biopsy, retroperitoneal laparoendoscopic single-site surgery (LESS) is to be preferred as a minimally invasive technique. However, there are cases in which the LESS technique is difficult to perform, especially given that the learning curve is not optimal. We present a case of a Jehovah's Witness patient with severe obesity, in whom conventional retroperitoneal laparoscopic renal biopsy was preferred to the LESS technique.