bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Mathematical Approach to the Evaluation of Sediment Transport Capacity in the Human Urinary Tract
Authors: Calomino F. , Di Paolo N. , Palma G. , Gaggiotti E. 
Published: January 2018

Background It is not yet clear whether forced diuresis is useful for flushing out of the urinary tract, especially in cases of renal calculi or infections. A series of experiments conducted initially in vitro and then in vivo in rabbits, using sand and small glass spheres, showed that sediments can be eliminated from the urinary tract by forced diuresis. When distilled water was used, the effect was greater, both as weight of sand and as number of spheres eliminated, than when normal saline was used. The different characteristics of the two liquids gave rise to different intrapelvic pressures for a given flow. Materials and Methods Intrapelvic pressures, and liquid and solid discharges in vitro and in rabbits were used in a fluid mechanics analysis of the phenomenon to obtain non-dimensional formulae so that the results in rabbits could be extended to humans. Results The results made it possible to evaluate solid transport capacity induced in a healthy human of given weight by drinking a given quantity of water in an hour. Conclusions The mathematical model makes it possible to determine the quantity of water a patient must drink to induce a transport force sufficient for urinary tract wash-out.
Design and in Vitro Performance of a Novel Bileaflet Mechanical Heart Valve Prosthesis
Authors: Medart D. , Schmitz C. , Rau G. , Reul H. 
Published: January 2018

Design and in vitro performance of a novel bileaflet mechanical heart valve prosthesis are presented. The novel heart valve exhibits three main design characteristics: (i) The leaflets form a Venturi passage in open position. Thus, a beneficial pressure distribution is obtained and the leaflets are stabilised in opened position. (ii) The orifice inlet is nozzle-shaped. Flow is convectively accelerated and flow separation at the orifice inlet is avoided. (iii) The hinge design facilitates an additional axial movement of the leaflets and leads to a self cleaning effect and enhances washout of the hinges. The design of the leaflet hinges is of main importance for the functional reliability and durability of mechanical heart valves. After manufacturing first prototypes from titanium and polymeric materials the hydrodynamic performance was evaluated according to ISO 5840 and FDA guidelines. Hydrodynamic performance is comparable with the results of commonly available bileaflet mechanical heart valve prostheses. Initial durability tests showed suitable material couples for further long term studies.
Comparative Analysis of Frozen and Acellularized Vascular Xenografts
Authors: Kim W.G. , Seo J.W. , Yang J.H 
Published: January 2018

Background We implanted frozen and acellularized porcine xenograft vessels as small-diameter arterial grafts in goats and comparatively analyzed the explanted grafts by gross observation and by light microscopy at predetermined periods. Materials and Methods Porcine carotid arteries were harvested and immediately stored within a tissue preservation solution at −70°C in a freezer designated for frozen xenograft vessels. The acellularized xenograft vessels were prepared with NaCl-SDS solution and stored frozen until use. One pair of porcine xenograft vessels were used to compare the frozen and acellularized grafts in the bilateral carotid arteries in one goat. The grafts were implanted for one, 3, and 6 months in three animals. Periodic ultrasonographic examinations were performed during the observation period. Explanted grafts were analyzed by gross observation, and by light microscopy. Results All animals survived the experimental procedure without specific problems. Ultrasonographic examinations showed excellent patency in all grafts during the observation period. Gross observations revealed nonthrombotic patent smooth lumens. Microscopic examinations of the explanted grafts showed satisfactory cellular reconstruction to the 6-month stage. Although more inflammatory responses were observed in the early phase of implantation of frozen xenografts than of acellularized xenografts, there was no evidence of significant rejection of the frozen xenografts. Conclusion These findings suggest that porcine vessel xenografts, regardless of them being acellularized or simply frozen xenografts, can be acceptably implanted in goats as a form of small-diameter vascular graft.
Dialytic Performance Evaluation of Rexeed™: a New Polysulfone-based Dialyzer with Improved Flow Distributions
Authors: Brendolan A. , Nalesso F. , Fortunato A. , Crepaldi C. , De Cal M. , Cazzavillan S. , Cruz D. , Techawathanawanna N. , Ronco C. 
Published: January 2018

New dialyzers are designed to optimize the convective and diffusive components of solute transport. Asahi Kasei Medical Co., Ltd. has developed a new high flux dialyzer series called Rexeed™ with improved flow distributions. We evaluated the in vivo dialytic performance of two dialyzers of the Rexeed™ series: Rexeed-18A and Rexeed-25A (1.8 m2 and 2.5 m2). We calculated the clearance for urea, creatinine, phosphate and b2-microglobulin both in high flux dialysis (HFD) and in 15 liter postidiluitional on-line hemodiafiltration (HDF) mode. With n=3 patients in high flux HD at blood flow 450, 400, 350 and 250 ml/min we found remarkably high clearance for urea (347±4%,305±0%,288±5%,230±3%, for Rexeed-18A and 361±3%,329±0%,313±1%,234±3% for Rexeed-25A), creatinine (282±10%,234±0%, 221±8%, 174±8%, for Rexeed-18A and 276±6%,245±0%,226±9%,172±13% for Rexeed-25A), phosphate (347±0%,316±0%,275±4%,202±16%, for Rexeed-18A and 364±3%,365±0%,286±3%,224±2% for Rexeed-25A) and b2-microglobulin (133±21%,124±0%,118±12%,98±11%, for Rexeed-18A and 159±8%,169±0%,157±8%,129±7% for Rexeed-25A) With n=2 patients in HDF at blood flow 300 ml/min we found remarkably high clearance for urea (268±2%, for Rexeed-18A and 283±2% for Rexeed-25A), creatinine (183±6% for Rexeed-18A and 205±9% for Rexeed-25A), phosphate (245±3%, for Rexeed-18A and 270±2% for Rexeed-25A) and b2-microglobulin (166±12%, for Rexeed-18A and 192±4% for Rexeed-25A). Our preliminary evaluation describes the characteristics and the performances of a new polysulfone-based hemodialyzer series called Rexeed™. Several innovative features have been implemented by the manufacturer. These constructive approaches seem to have produced a positive effect on the dialyzer performance at the bedside.
Effect of Hirudin versus Heparin on Hemocompatibility of Blood Contacting Biomaterials: An in Vitro Study
Authors: Kopp R. , Bensberg R. , Kashefi A. , Mottaghy K. , Rossaint R. , Kuhlen R. 
Published: January 2018

Hirudin serves as an alternative anticoagulant for extracorporeal blood circulation. Comparing anticoagulation with hirudin (2.5 or 5.0 μg/mL) and heparin (2.0 or 4.0 IU/mL) human blood was circulated in a modified “Chandler System” using PVC-tubes for 2 hours at 37°C. Activation of coagulation (thrombin-antithrombin III-complex, prothrombin fragment 1+2 and D-Dimer), platelet (platelet factor 4 - PF4) and complement systems was analyzed. Both heparin concentrations and 5.0 μg/dL hirudin led to as significantly less activated plasmatic coagulation as 2.5 μg/dL hirudin. Decreased levels of PF4 and anaphylatoxin C5a (P&0.05) as well as terminal complement complex demonstrated improved hemocompatibility after anticoagulation with heparin in contrast to hirudin. Because initial coagulation cascade, platelet activation and complement activation is less influenced by hirudin than by heparin, hemocompatibility is more dependent on the characteristics of the biomaterials used. This predestines hirudin as anticoagulant for in vitro studies analyzing hemocompatibility of biomaterials or surface modifications.
Advantages and Disadvantages of Surgical Placement of PD Catheters with Regard to Other Methods
Authors: Stegmayr B.G. 
Published: January 2018

Peritoneal dialysis is underused for various reasons. One reason may be problems with insertion of catheters for access. Another reason is the delayed start (break-in period) of about 2 weeks after operation. This review describes various approaches to the insertion of a peritoneal dialysis catheter. The optimal conditions to strive for are given as is an overview of various techniques. This article favours surgical placement while others might prefer other techniques. Described is the use a 3-purse string suture technique that allows immediate start of dialysis after catheter insertion both for acute dialysis indications as well as for acute start in chronic dialysis patients. A key to lesser complications is to establish a team devoted to the insertions rather than to allow various physicians to perform insertions as a training procedure. An optimal access is one of the important life lines for these patients.
The Self-Locating Catheter: Review and Cost Analysis
Authors: Di Paolo N. , Sansoni E. , Cappelletti F. , Cavatorta F. , Galli S. , Nicolai G.A. , Gaggiotti E. 
Published: January 2018

The self-locating catheter invented by Nicola Di Paolo has been increasingly used in Italy and elsewhere since 1994, with about a thousand patients currently implanted every year. Twelve grams of tungsten inserted in the tip of the conventional Tenckhoff catheter during extrusion do not significantly change its form, but suffice to keep the tip firmly in the Douglas cavity. The validity of the new catheter is confirmed by a multicentric controlled study in a large population of peritoneal dialysis patients. This trial showed that patients with the new catheter have fewer episodes of peritonitis, tunnel infection, cuff extrusion, catheter malfunction, obstruction and leakage. This paper outlines the present situation and reports a comparative analysis of the costs of Tenckhoff and self-locating catheters.
Informed Consent for Therapy and Research in Continuous Renal Replacement Therapy: An International Survey
Authors: Zamperetti N. , Bellomo R. , Ronco C. , Bolgan I. , Ricci Z. 
Published: January 2018

Objective To study the approach of health care workers (HCW) to informed consent for therapy and research in the field of continuous renal replacement therapy (CRRT) Design Administration of questionnaire. Setting Two International Courses on Critical Care Nephrology (CCN) held in Vicenza and Melbourne. Participants Eight hundred and twenty one course participants. Results We obtained 349 analysable questionnaires (42.5% of participants). Only 22.5% of responders always obtain informed consent for CRRT; 70.3% just inform patients/relatives without seeking consent, 7.1% never obtain informed consent. In ICU patients, informed consent is considered “good, correct and feasible” for therapy and for research by only 13% and 27% of responders, respectively. Consent for clinical research obtained from the next of kin or legal guardian is considered “good, correct and feasible” by 56.3% of respondents, while 39.1% believe that next of kin or legal guardians can not really make informed decisions. Finally, nearly half of responders think that present rules hamper research in ICU. For many questions, significant variability of responses was found according to profession, speciality and origin of responders. Conclusions In the field of CRRT, stated practice, beliefs and currently accepted ethical standards vary greatly according to profession, speciality and origin. A significant disagreement between what is widely promoted to be the “correct” approach and what is currently done is evident.
Design of a Subcutaneous Vascular Access Device Using Ni-Ti SMA Clamps for Hemodialysis
Authors: Choi S.W. , Nam K.W. , Lee J.C. , Yoon K.H. , Kim J.C. , Sun K. , Min B.G. 
Published: January 2018

A subcutaneous vascular access device which utilizes an Ni-Ti shape memory alloy (Ni-Ti SMA) spring, has been developed as a new method for subcutaneous vascular access in the treatment of hemodialysis patients. Until now, the connection between the SVAD and needle cannot be externally monitored, and the clamp must be opened and closed with a percutaneous needle by a nephrologist. The SMA-SVAD accomplishes the opening and closing of its clamp using two Ni-Ti SMA springs, and a transcutaneous energy transmission system (TET) transmits energy to the Ni-Ti SMA springs without the need for percutaneous wires. Two SMA springs open and close the clamp of the SMA-SVAD, without affecting any of the other parts of the system. Wasted thermal energy is reduced to minimal values via electrical regional heating methods. The state of the SMA-SVAD can be monitored according to the amount of power consumed by the external energy transmitter. In in-vitro experiments, when the clamp was opened and the pressure difference in the hemodialysis machine was set to 50 mmHg, water flow through SMA-SVAD reached 500 ml/min. The maximal surface temperatures of the SVAD and catheter were successfully maintained at proper levels (38~39°C), 2~3 degrees higher than the temperature of the surrounding tissues. The time elapsed from the initiation of energy transmission until the opening of the SMA clamp was 5 seconds.
In Vitro Set-Up of Modified Blalock Taussig Shunt: Vascular Resistance-Flow Relationship
Authors: Bakir I. , Van Tricht I. , Verdonck P. , Meyns B. 
Published: January 2018

Background A modified Blalock-Taussig (mBT) shunt is an anastomosis created between the systemic and pulmonary arterial tree in order to improve pulmonary blood flow in neonates and children with congenital heart disease. The aim of this study was to assess vascular resistance-flow relationship in an in vitro set-up of a modified Blalock Taussig shunt. Methods A shunt set-up was constructed with the vessels of a sheep. A modified BT shunt was anastomosed between an innominate (brachiocephalic) and a right pulmonary artery. A Medos pump (ventricular assist device) was used to create pulsatile flow. Three different mean pulmonary artery flow rates (QPA) were applied. Once mean pulmonary and mean aortic flows (QAO) were fixed, shunt flow rates for twelve different pulmonary vascular resistances (Rp) were investigated. Results For all three pulmonary flow rates, the shunt flow decreased with increasing pulmonary resistance. In addition, systemic flow decreased compared to pulmonary flow. When pulmonary flow rate was set at 800 ml/min and aorta flow rate at 900 ml/min, the distribution of flow between pulmonary and systemic organs flow rates ranged between 69% - 70% and 30% - 31% respectively. Similarly, when both pulmonary and aorta flow rates were set at 900 ml/min, pulmonary and systemic organ flows ranged between 73% - 77% and 23% - 27% respectively. For pulmonary and aorta flow rates of 1000 ml/min and 900 ml/min, respectively, the distribution of flow between pulmonary and systemic organ flow rates varied between 79% - 83% and 17% - 21% respectively. Conclusion Knowledge of the relationship between vascular resistances and flow in this surgically created in vitro mBT shunt set-up may be helpful in the clinical management of the patients whose survival is crucially dependent on the blood flow distribution between the pulmonary and systemic circulation.
Safety of Citrate Based Hemofiltration in Critically Ill Patients at High Risk for Bleeding: A Comparison with Nadroparin
Authors: Van Der Voort P.H.J. , Postma S.R. , Kingma W.P. , Boerma E.C. , Van Roon E.N. 
Published: January 2018

Purpose To study the incidence and severity of bleeding in high risk critically ill patients during high volume, citrate based continuous veno-venous hemofiltration (CVVH). Design A prospective 1-year observational cohort study comparing citrate based CVVH with nadroparin based CVVH. Procedures Critically ill patients with multiple organ dysfunction and in need of CVVH were observed for bleeding complications during their CVVH sessions. Pre-defined criteria determined that patients were treated with citrate based CVVH in case of active bleeding or increased risk for bleeding. Otherwise nadroparin was used as anticoagulant. Statistical and Outcome Methods The incidence of bleeding complications, the number of transfused blood cell concentrates and the filter-run-time were recorded. Analyses were made by non-parametric tests. Main Findings Fifty-five patients received 272 CVVH sessions. In the citrate group 14.8% experienced a bleeding complication compared to 25% in the nadroparin group (p=0.04). The number of transfused red blood cell concentrates was not different between groups. The nadroparin group had a longer filter run time (median 31.5 hours versus 22.5 hours, p=0.0001). Conclusions In high risk critically ill patients citrate based anticoagulation for CVVH is safe in terms of bleeding complications and transfusion requirements.
Impedance Cardiography Derived Cardiac Output in Hemodialysis Patients: A Study of Reproducibility and Comparison with Echocardiography
Authors: Karakitsos D.N. , Patrianakos A.P. , Paraskevopoulos A. , Parthenakis F.I. , Tzenakis N. , Fourtounas C. , Daphnis E.K. , Vardas P.E. 
Published: January 2018

Background Hemodialysis patients experience a variety of hemodynamic abnormalities that contribute to cardiovascular disease mortality which is the leading cause of death in these patients. Impedance cardiography has been utilized in order to monitor cardiac hemodynamics with lower cost and inconvenience, but it has not been appropriately validated in the hemodialysis population. Aim We repeatedly used impedance cardiography to assess short- (48 hours) and long-term (15 days) reproducibility of cardiac output measurements and we compared baseline impedance cardiography measurements with echocardiographic measurements. Patients and Methods We studied 109 stable hemodialysis patients, aged 59.70 ± 11.97 years being on hemodialysis for 67.59 ± 40.15 months, on a non-dialysis day. Cardiac output was obtained with the BioZ impedance cardiography system (Cardiodynamics, San Diego, Ca, USA). Baseline echocardiography was performed using a Hewlett-Packard Sonos 2500 (Andover, Mass., USA). Results The values of impedance cardiography derived cardiac output were 5.28 ± 0.79, 5.27 ± 0.75 and 5.25 ± 0.74 l/min at baseline (107 patients), 48 hours (107 patients) and 15 days (98 patients) respectively, showing high reproducibility. Bland and Altman analysis estimated that bias at 48 hours and at 15 days were: −0.013 (95% confidence intervals = −0.045 to 0.019) and 0.028, (95% confidence intervals = −0.044 to 0.101), respectively. In addition baseline impedance cardiography derived cardiac output was significantly correlated with the echocardiographic derived cardiac output (r = 0.9, p < 0.0001). Conclusion Impedance cardiography is a simple non invasive technique for cardiac output estimation in hemodialysis patients which has high reproducibility when performed under controlled conditions, and is closely correlated with echocardiographic measurements of cardiac output.
Virtual Respiratory System for Education and Research: Simulation of Expiratory Flow Limitation for Spirometry
Authors: Golczewski T. , Darowski M. 
Published: January 2018

Background Due to economic and ethical problems, virtual organs may appear more convenient than experiments on animals or limited investigations on patients. In particular, a virtual respiratory system (VRS) may be useful for tasks such as respirators and support methods testing, education, staff (medical and technical) training, (initial) testing of scientific hypotheses. Methods A comparative study of simulated and real spirometric results for different patient states (healthy lungs, restrictive lung disease, and obstructive lung disease of different localization and degree) was performed. The volume-flow curve and such standard parameters as FEV1, FEV1%VC, MEF75 etc. were analyzed. Results A mathematical description of collapsing bronchi was proposed. All fundamental phenomena present during spirometry also appeared in VRS, especially characteristic dependence between lung volume and air flow for forced expiration. In particular, both airway resistance and the flow limitation were described with one formula derived from commonly known dependence of the resistance on lung volume. Generally there were no significant differences between simulated results and those seen in clinical practice. Only simulation of obstruction in upper airways gave incorrect results, which suggested a different flow limitation mechanism (perhaps wave-speed limitation). Conclusions Our VRS can already be used in medical education, e.g. courses of spirometry, and in some other applications. It seems that the significance of the wave-speed criterion has been overestimated.
Surgical Procedures before and after Starting Chronic Hemodialysis in a Predominantly Male Population with High Prevalence of Diabetes
Authors: Martinez Milagros , Last Reuben , Agaba Emmanuel I. , Kassam Hussein , Sun Yijuan , Servilla Karen S. , Murata Glen H. , Tzamaloukas Antonios H. 
Published: January 2018

Purpose The purposes of this study were to analyze changes in the frequency of different categories of surgical procedures after initiation of chronic hemodialysis (HD) and to identify the types of procedures associated with in-hospital postoperative mortality. Methods This was a retrospective analysis of surgical procedures performed in an incident HD population of 392 patients followed in the dialysis unit of one hospital over 15 years. Among these patients, 384 were men and 258 had diabetes mellitus. At the start of HD, age of the patients was 66.3 ± 11.2 years and Charlson index 5.35 ± 2.41. Rates of procedures per patient year (n/[pt-yr]), reported as mean (95% Confidence Interval [CI]), were compared by nonparametric methods. Results In the whole HD population, the overall rate of procedures increased in the HD period (pre-HD 0.125 [95% CI 0.101–0.149] n/[pt-yr]; HD 0.928 [95% CI 0.795–1.061] n/[pt-yr]; p<0.001). The increase, noted in patients with and without diabetes, reflected increases in the rates for both vascular access and non-vascular access procedures from the pre-HD to the HD period. Amputations and surgery for hip fractures accounted for the increase in the rates of procedures related to non-vascular access. Procedures associated with mortality in the HD period included amputations, hip repair and abdominal surgery for septic conditions. Conclusions Rates of surgical procedures for vascular access, amputations, and hip fractures increased after the start of HD. Amputations and hip fractures, both potentially preventable, are associated with mortality in HD patients.