bluuebunny/crossref_metadata_2025 huggingface dataset:
Potassium-Based Dilutional Method to Measure Hemodialysis access Recirculation
Authors: Brancaccio D. , Tessitore N. , Carpani P. , Gammaro L. , Losi B. , Zoni U. , Maschio G. , Gallieni M.
Published: March 2018

Background

Assessment of access recirculation (AR) is crucial to dialysis efficiency and there is thus a need for a method yielding a highly accurate, fast, easy and economical measurement that can be applied in any busy dialysis clinic. Non-urea based dilutional methods are more accurate than urea based methods and avoid problems with cardiopulmonary recirculation, but they require expensive specialized devices, which limit their applicability.

Methods

We developed a simple dilutional method of AR which does not require any specific device, based on the determination of serum potassium [K+] in two samples. Briefly, a basal sample is drawn at the time of needle insertion (basal [K+]); needles are connected to blood lines and blood flow rate is quickly increased to 300 ml/mm; a second sample (arterial [K+]) is drawn from the arterial line port within 5 to 10 seconds, to avoid errors due to cardiopulmonary recirculation of the normal saline entering the blood stream. At this time, if recirculation is present, part of the normal saline will enter the arterial line and dilute the serum [K+]. The AR formula is: AR (%) = 100 x [1 - arterial K+ / basal K+] We compared our method with the two-needle urea and ultrasound velocity dilution methods. Results: AR values by the ultrasound method > 10% were hypothesized as gold standard for AR, against which values obtained with the potassium method were compared. The potassium based method showed: sensitivity (100%,); specificity (95%); predictive value, positive (91%); predictive value, negative (100%). In addition, the potassium based method appears to be more reliable than the two-needle urea based method.

Conclusion

Our method, similar to other dilutional methods, is not influenced by cardiopulmonary recirculation or veno-venous disequilibrium and is fast and accurate. Moreover it is very simple, economical, and can easily be performed in any dialysis unit.
Two-Dimensional Finite Element Model for Oxygen Transfer in Cross-Flow Hollow Fiber Membrane Artificial Lungs
Authors: Dierickx P.W. , De Wachter D.S. , Verdonck P.R.
Published: March 2018

A predictive, two-dimensional model with good absolute accuracy for flow and mass transfer in cross-flow hollow fiber membrane artificial lungs is developed. The proposed model is able to predict the gas transfer to water flowing outside and perpendicular to hollow fibers in the artificial lung. The model uses a finite element technique to solve the Navier-Stokes equations and the convection-diffusion equation on the computational domain of a unit fiber cell. Subsequent stream-wise and cross-wise unit fiber cells are then coupled/assembled to the relationship between the oxygen transfer rate and flow rate of a cross-flow hollow fiber membrane artificial lung. The model is compared to experimental water data obtained by perfusing three commercial artificial lungs with water.
Tissue-Engineered Heart Valve Leaflets: An Animal Study
Authors: Kim W.G. , Cho S.K. , Kang M-C. , Lee T-Y. , Park J.K.
Published: March 2018

Background

Tissue-engineered heart valve leaflets are a promising way to overcome the inherent limitations of current prosthetic valves. The aim of this study was to compare the biological responses of an autologous cell seeded scaffold and an acellular scaffold implanted in the pulmonary valve leaflet in the same animal.

Methods

Myofibroblasts and endothelial cells were isolated and cultured from an ovine artery. A synthetic biodegradable scaffold consisting of polyglycolic acid and polylactic acid was initially seeded with the myofibroblasts, then coated with endothelial cells. Cells were seeded using a medium containing collagen and cultured. A tissue-engineered construct and a plain scaffold were implanted as double pulmonary valve leaflet replacement in the same animal in an ovine model (n=3). Additionally, the tissue-engineered construct (n=2) and the plain scaffold (n=2) were implanted as single valve leaflet replacements for long-term analysis. After sacrifice, the implanted valve leaflet tissues were retrieved, analyzed visually and using light microscopy.

Results

Three animals that underwent replacement of two valve leaflets with a tissue-engineered construct and a plain scaffold, survived only a short-time (12, 24, 36 hours). The death was attributed to heart failure caused by severe pulmonary insufficiency. Animals that underwent single valve leaflet replacement survived longer and were electively sacrificed at 6 and 9 weeks after operation. The analysis of the leaflets from the short-term survivors showed that the tissue-engineered constructs contained less fibrins and protein exudates than the plain scaffold. In contrast, leaflets obtained from animals surviving 6 and 9 weeks showed similar well organized granulation tissues in the tissue-engineered constructs and the plain scaffolds.

Conclusion

This animal experiment demonstrates that in the early phase of implantation, the tissue-engineered construct shows a better biological response in terms of antithrombogenicity than the plain scaffold, although both of them have similar results in the later reparative phase.
Water and Small Solute Excretion in Continuous Peritoneal Dialysis Patients with Lean Body Mass Exceeding 90% of Body Weight as Estimated from Creatinine Kinetics
Authors: Tzamaloukas A.H. , Murata G.H.
Published: March 2018

Lean body mass computed from creatinine kinetics (LBM) is an index of somatic nutrition and correlates with other nutrition indices in CAPD. However, LBM exceeding 90% of body weight (LBM/W ≥ 0.9) may be an index of non-compliance, rather than nutrition. To test this hypothesis, we analyzed fluid and solute excretion in 40 CAPD patients with LBM/W ≥ 0.9 (group A). The comparison group (group B) consisted of 885 CAPD patients with LBM/W < 0.9. Group A was younger (38.3±14.8 vs 54.7±14.7 yr) and had a lower percent of women (23.5% vs 41.1%) and diabetic subjects (17.5% vs 42.6%) than group B (at P ≤ 0.019). Group A also had lower body mass index (22.7±2.7 vs 25.8±5.1 kg/m2 P <0.001) and serum albumin (33.0±6.7 vs 35.2±5.5 g/L, P = 0.014). Despite similar prescribed daily fill volumes (group A 8.3±2.4, group B 8.5±2.2 L/24 h) and similar D/P urea and creatinine values, group A had higher daily drain volume (11.0±3.6 vs 9.6±2.1 L/24 h, P < 0.001). Renal clearances were similar, while peritoneal and total clearances were apparently higher in group A. Creatinine excretion was higher in group A (27.4±5.1 vs 13.6±4.1 mg/kg x 24 h, P < 0.001), with a large part of the excess creatinine excretion in group A being accounted for by peritoneal excretion. The combination of an apparently high daily ultrafiltration volume (2.7 L/24 h on the average), unrealistically high creatinine excretion rate, and relatively poor nutrition (low body mass index and serum albumin) in group A is consistent with non-compliance. We suggest that the finding of LBM/W ≥ 0.9 during a clearance study in CAPD should trigger an investigation for non-compliance.
Flow Analysis in Vascular Shunts that Bypass the Carotid Artery
Authors: Verkerke G.J. , Van Den Dungen J.J.A.M. , Meyer T. , Rakhorst G.
Published: March 2018

When blood flow through a carotid artery is impaired and vascular surgery is necessary to restore adequate circulation a vascular shunt can be applied to maintain cerebral blood flow. Several vascular shunts are commercially available, but there is only limited test data on their flow capacity. The purpose of this study is to determine the flow capacity of three vascular shunt systems. A theoretical model has been developed for this purpose. To validate the model, in vitro flow measurements were taken. Application of the model showed that all shunts cause a decrease in blood flow. The amount of flow decrease varied widely from 13% (Javid shunt) to 55% (Pruitt-Inahara). In vitro measurements confirmed the validity of the model.

In conclusion, it is important for the vascular surgeon to realise that vascular shunts show large differences in flow capacity. Of the three investigated shunts, the Javid has the highest flow capacity.
Surface Topography and Surface Elemental Composition Analysis of Helixone®, a New High-Flux Polysulfone Dialysis Membrane
Authors: Bowry S.K. , Ronco C.
Published: March 2018

Modern dialysis membranes need to fulfil two basic requirements. Firstly, the membrane structure, defined in terms of the size, structure and distribution of the pores at the inner separating layer of the membrane must be such that uraemic solutes of a defined molecular-weight range are selectively removed. Secondly, the physical and chemical properties of the blood-contacting surface must be such that minimal blood-material interactions take place that could either affect the functioning of the membrane, or, cause adverse reactions for the patient.

A new polysulfone dialysis membrane, Helixone®, has been developed specifically for the elimination of larger uraemic toxins using convective therapy modalities such as haemodiafiltration. The membrane is characterised by the nanoscale modulation of the innermost surface structures that lead to significantly increased sieving coefficients for molecules such as β2-microglobulin, while maintaining the extremely low albumin removal property of the high-flux Fresenius Polysulfone® membrane. A recent publication (Ronco C, Bowry SK. Nanoscale modulation of the pore dimensions, size distribution and structure of a new polysulfone-based high-flux dialysis membrane. Int J Artif Organs 2001; 24: 726–35) described the characterisation of the membrane of Helixone® in terms of the membrane wall structure- and permeation-related parameters.

In this paper, we describe the analysis of membrane surface parameters that influence the biocompatibility as well as the functioning of a membrane. The degree of roughness and the type of chemical groups of a blood-contacting surface are two of the main determinants of the biocompatibility characteristics of a membrane. The surface elemental composition of Helixone® was determined using electron spectroscopy for elemental analysis (ESCA) while the surface topography of the membrane was evaluated using atomic force microscopy (AFM). The analysis showed that Helixone® has an improved, smoother blood-contacting surface and retains the essential surface chemistry, and therefore the acknowledged biocompatibility profile, of the Fresenius Polysulfone® membrane.
Choosing New Adsorbents for Endogenous Ultrapure Infusion Fluid: Performances, Safety and Flow Distribution
Authors: De Nitti C. , Giordano R. , Gervasio R. , Castellano G. , Podio V. , Sereni L. , Ghezzi P.M. , Ronco C. , Brendolan A. , Inguaggiato P. , Tonelli M. , La Greca G. , Tetta C.
Published: March 2018

Adsorption may notably contribute to the removal of uremic toxins and to the efficiency of hemodialysis. We examined different uncoated stationary matrixes, charcoals and synthetic resins to establish their adsorptive capacities in relation to low (urea, creatinine) and high molecular weight (β2-microglobulin, myoglobin) compounds in in vitro conditions (steady state and flow-through) using isotonic solutions or uremic ultrafiltrate. Trace metal, particle release analyses and scanning electron microscopy of different adsorbents were performed. Dynamic flow-distribution studies were made using 99Technetium and analysing the different regions of interest by single head γ-camera. We show that adsorbents may differ greatly as to their adsorptive capacity depending on flow rate, nature, and total mass of the compounds to be removed from the ultrafiltrate. These studies suggest a methodological approach for screening stationary matrixes for possible application in hemodialysis.
Mass Preparation of Primary Porcine Hepatocytes and the Design of a Hybrid Artificial Liver Module using Spheroid Culture for a Clinical Trial
Authors: Fukuda J. , Sakiyama R. , Nakazawa K. , Ijima H. , Yamashita Y. , Shimada M. , Shirabe K. , Tsujita E. , Sugimachi K. , Funatsu K.
Published: March 2018

To isolate a large number of porcine hepatocytes, we originally developed a mass preparation method that combined the usual collagenase perfusion method of a whole liver with a collagenase redigestion method of tissue fragments after liver perfusion. Using a pig of 10kg, collagenase perfusion only resulted in a yield of 63 ± 78 x 108 total cells with a viability of 69.2 ± 25.3 %, but our combined method had a yield of 167 ± 31 x 108 total cells with a viability of 87.9 ± 4.4 % (mean ± SD). Also, the combined method was applied to two pigs of 10kg body weight at the same time, and isolated 387 ± 89 x 108 hepatocytes with a viability of 87.1 ± 6.9 % and a purity of 93.6 ± 2.8 % in 11 experiments.

We designed a large multi-capillary polyurethane foam (MC-PUF) packed-bed module containing 1 x 1010 porcine hepatocytes on a clinical trial scale. The porcine hepatocytes in the module formed spherical multicellular aggregates (spheroids) of 200 – 500 μm diameter. Most hepatocytes forming spheroids were viable judged by fluorescein diacetate and ethidium bromide staining. The activities of ammonia removal, albumin secretion and oxygen consumption of the large MC-PUF module were the same as for a small MC-PUF module containing 2 x 108 porcine hepatocytes, and were maintained for at least 9 days of culture. These results show that a large MC-PUF module is successfully scaled up 50 times.

In conclusion, we succeeded in developing a mass preparation method of porcine hepatocytes and a large hybrid artificial liver module on a clinical trial scale.
Experimental Evaluation of a Cell Module for Hybrid Liver Support
Authors: Gerlach J.C. , Botsch M. , Kardassis D. , Lemmens P. , Schön M. , Janke J. , Puhl G. , Unger J. , Kraemer M. , Busse B. , Böhmer C. , Belal R. , Ingenlath M. , Kosan M. , Kosan B. , Sültmann J. , Patzold A. , Tietze S. , Rossaint R. , Müller C. , Mönch E. , Sauer I.M. , Neuhaus P.
Published: March 2018

Aim of the study was to evaluate a hybrid liver support system in a porcine model of acute liver failure, after hepatectomy. Pigs with a body weight of 70±18 kg underwent total hepatectomy and porto - cavo - caval shunting as well as ligation of the bile duct and the hepatic artery. Control animals were connected to the system (including capillary membrane plasma separation) containing a four compartment bioreactor with integral oxygenation and decentralized mass exchange but without liver cells. The treatment group received hybrid liver support with the same system including 370±42 g primary isolated porcine parenchymal liver cells in co-culture with hepatocyte nursing cells, tissue engineered to liver- like structures at high density. Treatment started after complete recovery from anesthesia and was performed continuously. A positive influence on peripheral vascular resistance and a reduced need of catecholamine dosage was observed in the treatment group. Hybrid liver support with a cell module upscaled for clinical application significantly prolonged survival time in animals after hepatectomy with the longest survival being 26 hours in the control group an 57 hours in the treatment group.
The Ovariectomized Ewe Model in the Evaluation of Biomaterials for Prosthetic Devices in Spinal Fixation
Authors: Giavaresi G. , Fini M. , Torricelli P. , Martini L. , Giardino R.
Published: March 2018

The effect of surgical ovariectomy on cancellous bone was investigated by comparing mechanical properties and microarchitectural characteristics of the lumbar vertebrae in ovariectomized and sham-operated ewes. Eighteen mongrel ewes, 4±1 years old, were randomly divided into three groups: 6 animals served as a control group (Baseline), 6 were bilaterally ovariectomized (OVX), and the others were used as a sham-operated group (SHAM). OVX and SHAM ewes were euthanized 24 months after surgery; the L5 vertebrae were processed for mechanical and histomorphometric analyses. Maximum load, maximum strength (p<0.0005) and elastic modulus (p <0.005) decreased by about 28% in the OVX group in comparison with the other groups. In the OVX group, vertebral cancellous bone volume, trabecular thickness and trabecular number decreased by about 32% (p<0.0005), 15% (p=0.001) and 20% (p=0.019), respectively. An overall decrease in the bone turnover rate of the OVX group was registered in terms of bone formation rate (p= 0.007) and activation frequency (p<0.0005). The variations observed in cancellous bone mechanics and histomorphometry would suggest the development of an osteopenic state in ewe vertebrae at 24 months. Such findings may be useful for future experimental investigations on biomaterials and prosthetic devices to be implanted in the osteopenic spine.
The Effect of Serum from Liver Cancer Patients on the Growth and Function of Primary and Immortalised Hepatocytes
Authors: Grant M.H. , Rodgers E.H. , Anderson K. , Haydon G.H. , Hayes P.C.
Published: March 2018

A limiting factor in the efficacy of bioartificial liver (BAL) for the treatment of liver failure is the toxicity of the patients’ serum to the hepatocytes in the device. This study investigates the interaction of liver cancer patient serum with primary and immortalised rat hepatocytes. Liver cancer serum increased the growth rate of immortalised hepatocytes, without affecting reduced glutathione levels. The activities of DT-diaphorase and pi glutathione-S-transferase (GST), enzymes associated with de-differentiation, were also increased. Exposure of primary hepatocytes to liver cancer serum resulted in a decrease in cytochrome P450 (CYP) content, and in P450 dependent metabolism of testosterone. Formation of 2-alpha- and 6-beta- hydroxy testosterone was decreased. These reactions are predominantly associated with CYP 2C11 and 3A1 respectively in normal rat liver. The activity of total GST was also decreased, although that of the pi isoenzyme of GST was not affected. Our results suggest that exposure of hepatocytes in a bioreactor to liver cancer patient serum will result in overgrowth of cells, if proliferating cells are being used, and in de-differentiation. The serum may have to be pretreated with adsorbants to remove toxins prior to BAL treatment.
Ozonation of Blood during Extracorporeal Circulation II. Comparative Analysis of Several Oxygenator-Ozonators and Selection of One Type
Authors: Bocci V. , Di Paolo N. , Borrelli E. , Larini A. , Cappelletti F.
Published: March 2018

Exposure of human blood ex vivo to oxygen-ozone (O2- O3) using either dialysis exchangers or normal oxygenators gives rise to a number of problems, one of which linked to platelet activation, leads to rapid occlusion and no gas exchange. Semipermeable membranes were found unsuitable because, except for one, they were gas-transfer inefficient, allowed ultrafiltration and were more or less vulnerable to O3. Over the last three years we have examined several types of hydrophobic O3-resistant hollow fiber capillaries but, if the polypropylene surface is not properly coated, there is platelet aggregation and blood coagulation. These problems while far less relevant with O2 alone, become prohibitive in the presence of ozone. Recently new oxygenators have been prepared with special materials to make them more biocompatible and it has become possible to oxygenate and ozonate up to 5L of blood in about an hour, thus making the treatment of critical patients feasible.
Long Term Clinical and Echocardiographic Results of Isolated Aortic Valve Replacement in Elderly Patients
Authors: De Feo M. , Renzulli A. , Vicchio M. , Onorati F. , Dialetto G. , De Santo L.S. , Corte A. Della , Cotrufo M.
Published: March 2018

Results after isolated aortic valve replacement with bileaflet prostheses in patients over 70 years old were reviewed.

One-hundred-twenty-eight elderly patients were operated on between January 1988 and January 2000. Patients with associated heart disease were excluded from the study. Preoperative data, early and late postoperative mortality, all valve related complications and data concerning anticoagulation status were recorded.

Hospital mortality was 9.3%. Mean follow-up time was 60.98±2.23 months. Twelve-year actuarial survival was 69.6±0.08%. Valve related and anticoagulation related complication rates (0.8% and 1.6% respectively) and actuarial freedom (99±0.009 both) were low, as well as the mean interval between consecutive INR checks (18.39±1.90 days) and the mean INR value (2.17±0.135). Late echocardiographic results showed low postoperative mean transprosthetic gradients (15.48±0.94).

Bileaftlet prostheses in the elderly can achieve excellent results with a low incidence of anticoagulation related complications and low risk of reoperation. Older age can no longer be considered a contraindication to bileaftlet prosthesis implant.
Insomnia is Associated with Systolic Hypertension in Uremic Patients on Hemodialysis
Authors: De Santo R.M. , Lucidi F. , Violani C. , Bertini M.
Published: March 2018

A newly developed questionnaire was administered to 140 hemodialyzed patients (82 M and 58 F) who have achieved adequate anemia correction according to the best guidelines with the aim: to evaluate the prevalence of clinical/subclinical dyssomnias in these patients; to study the influence of the dialytic shift (morning versus afternoon schedules) on sleep duration and disturbancies; and to evaluate the relationship between clinical sleep disorders and blood pressure values in uremic patients. Results indicated that 85% of uremic patients undergoing hemodialysis complain of clinical insomnia (frequent, persistent and associated with daytime consequences) or subclinical sleep disorders; patients dialyzing in the morning sleep significantly less during the night preceding the treatment, than those dialyzing in the afternoon; older patients complaining of clinical insomnia have a higher risk of failure to achieve target-optimal values in systolic blood pressure.
The Influence of Different Glucose Concentrations in Haemodialysis Solutions on Metabolism and Blood Pressure Stability in Diabetic Patients
Authors: Simic-Ogrizovic S. , Backus G. , Mayer A. , Vienken J. , Djukanovic L. , Kleophas W.
Published: March 2018

In recent years the percentage of diabetic patients on haemodialysis has increased. Considering the high frequency of intradialytic hypotensive and hypoglycaemic episodes experienced by these patients, it was the aim of the present study to evaluate the influence of different dialysate glucose concentrations (5.5 mmol/L or 11 mmol/L) on blood pressure and glycaemic regulation, using special dialysis equipment - the GENIUS® System.

This cross-over, prospective and randomised study, total duration 14 weeks, included 20 diabetic patients on maintenance haemodialysis. Group 1: 9 patients dialysed using dialysate with a glucose concentration of 5.5 mmol/L and after 7 weeks switched to dialysate with a glucose concentration of 11 mmol/L. Group 2: vice versa.

Results show a statistically higher number of patients with hypoglycaemic and hypotensive episodes using dialysate with a 5.5 mmol/L glucose concentration. Also, mean serum glucose values were higher during haemodialysis sessions with a glucose dialysate concentration of 11 mmol/L. There were no statistical differences between the groups in laboratory values, HbA1C, insulin doses or in anthropometric parameters.

Our results suggest that fewer diabetic patients undergoing haemodialysis using a higher dialysate glucose concentration of 11 mmol/L have hypoglycaemic and hypotensive episodes. Since this dialysate glucose concentration had no influence on lipid or hepatic metabolism, anthropometric parameters and especially HbA1C values in this short-term study, the long term examination of its effects is warranted.
The Need for Imaging Methods in Bioengineering of Three-Dimensional Cell Cultures
Authors: Freimark Denise , Ehlicke Franziska , Czermak Peter
Published: March 2018

The analysis of live cells and tissue is gaining increasing importance in research and development. A number of demands are thus being made on the cultivation and analysis of cell response as well. For certain research approaches, in vitro three-dimensional (3D) cultivation best mimics natural conditions. Nevertheless, the imaging of such 3D environments is still a problem. To understand cell function in 3D, a number of in vivo imaging methods have been developed. This article introduces this field and proposes some interesting and promising imaging techniques for this approach.
Evaluation of Cartilage Specific Matrix Synthesis of Human Articular Chondrocytes after Extended Propagation on Microcarriers by Image Analysis
Authors: Goepfert Christiane , Lutz Vivien , Lünse Svenja , Kittel Sabrina , Wiegandt Katharina , Kammal Michael , Püschel Klaus , Pörtner Ralf
Published: March 2018

Background

Cell-based technologies for the repair of cartilage defects usually rely on the expansion of low numbers of chondrocytes isolated from biopsies of healthy cartilage. Proliferating chondrocytes are known to undergo dedifferentiation characterized by downregulation of collagen type II and proteoglycan production, and by upregulation of collagen type I synthesis. Re-expression of cartilage specific matrix components by expanded chondrocytes is therefore critical for successful cartilage repair.

Methods

Human articular chondrocytes were expanded on microcarriers Cytodex 3. The growth area was increased by adding empty microcarriers. Added microcarriers were colonized by bead-to-bead transfer of the cells. The chondrocytes were harvested from the microcarriers and characterized by their ability to synthesize collagen type II when cultivated in alginate beads using chondrogenic growth factors. A semi-automatic image analysis technique was developed to determine the fractions of collagen type II and type I positive cells.

Results

The expansion of human articular chondrocytes on microcarriers yielded high cell numbers and propagation rates compared to chondrocytes expanded in flask culture for one passage. The proportion of collagen type II positive cells compared to collagen type I synthesizing cells was increased compared to chondrocytes expanded using conventional methods. The matrix synthesis upon treatment with chondrogenic factors IGF-I and BMP-7 was enhanced whereas TGF-β had an inhibitory effect on microcarrier expanded chondrocytes.

Conclusions

Expanding human articular chondrocytes on microcarriers omitting subcultivation steps leads to superior ratios of collagen type II to type I forming cells compared to the expansion in conventional monolayer culture.
Feasibility of Monte CarlO simulations in Quantitative Tissue Imaging
Authors: Maeder Ulf , Schmidts Thomas , Avci Ersin , Heverhagen Johannes T. , Runkel Frank , Fiebich Martin
Published: March 2018

Purpose

The feasibility of Monte Carlo simulations as a tool to facilitate quantitative image analysis is investigated by means of simulating light transport in skin phantoms.

Methods

A Monte Carlo tool is used to compare if simulated fluorescent signals show agreement with measured data. The lipophilic fluorescent probe Nile Red and dedicated skin phantoms are also used in simulations to investigate the influence of the optical properties of the skin on the signal.

Results

It is shown that the simulated and measured fluorescence signals show linear behavior up to a certain concentration of Nile Red. The simulations of the skin phantoms show the varying influence of single skin layers on the fluorescence signal. A calibration factor for quantitative analysis can be determined for the different skin layers.

Conclusion

Characterizing the influence of different media on imaging signals is a primary task in developing quantitative analysis methods. Monte Carlo simulations are a useful tool to investigate imaging properties of biological specimen where quantifying signals is important. However, detailed models must be provided.
Off-Label use of Stretchable Polytetrafluoroethylene: Overexpansion of Synthetic Shunts
Authors: Verbelen Tom O. , Famaey Nele , Gewillig Marc , Rega Filip R. , Meyns Bart
Published: March 2018

Purpose

To describe our experience with balloon dilatation and stenting of modified systemic-to-pulmonary artery (PA) shunts in relation to an assessment and interpretation of the mechanical properties of thin-walled expandable polytetrafluoroethylene (ePTFE) stretch vascular grafts.

Methods

Our pediatric cardiology/cardiac surgery database was reviewed to identify all infants and children with a modified systemic-to-PA shunt who underwent cardiac catheterization. Reports and images were reviewed. Thin-walled stretchable and regular Gore-Tex® vascular grafts were mechanically compared using tensiometry.

Results

11 patients underwent dilatation or stenting procedures of a systemic-to-PA shunt. No major complications occurred and none of our patients died during or due to this intervention. High pressures in balloons and stents with diameters larger than the graft were used. Shunt diameters and oxygen saturation levels increased from 2.05 ± 1.25 mm to 4.75 ± 0.88 mm and with 12 ± 6.8%, respectively. In 6 patients re-catheterizations were performed. Four patients died, all with patent shunts. The fail-stress and the fail-strain in the circumferential direction of the stretchable graft were significantly higher than in the non-stretchable graft.

Conclusions

Dilatation and stenting of stenosed modified systemic-to-PA shunts is feasible and safe. Dilatation and stenting of these shunts to calibers larger than those provided by the manufacturer is possible. Results of our technical study posit a great advantage for the use of the thin-walled stretch configuration of ePTFE.
Microstructure and Cytocompatibility of Electrospun Nanocomposites Based on Poly(ɛ-Caprolactone) and Carbon Nanostructures
Authors: Bianco Alessandra , Del Gaudio Costantino , Baiguera Silvia , Armentano Ilaria , Bertarelli Chiara , Dottori Mariaserena , Bultrini Giorgio , Lucotti Andrea , Kenny Josè Maria , Folin Marcella
Published: March 2018

Carbon nanostructures (CNSs) are attractive and promising nanomaterials for the next generation of tissue engineering scaffolds, especially in neural prosthesis. Optimizing scaffold vascularization may be an important strategy to promote the repair of damaged brain tissue. In this context, the idea was to evaluate the cell response of electrospun nanohybrid scaffolds loaded with CNSs. Fibrous composites based on poly(ɛ-caprolactone) (PCL) and CNSs were fabricated by means of electrospinning technique. High-purity carbon nanofibers (CNFs) and single-wall carbon nanotubes (SWNTs) were studied. A detailed microstructural characterization was performed to evaluate the most favorable experimental conditions for the realization of fibrous PCL/CNS fabrics. Electrospun mats comprised of rather uniform and homogeneous submicrometric fibers were obtained starting from 1:1 v/v mixture of tetrahydrofuran (THF) and N,N dimethylformamide (DMF). In vitro cytocompatibility tests were performed using rat cerebro-microvascular endothelial cells (CECs). Acquired results showed an increased cell viability for PCL/CNS nanocomposites, suggesting these materials as a suitable environment for endothelial cells. These results are indicative of the promising potential of CNS-based nanocomposites in biomedical devices for tissue engineering applications where endothelial functional properties are required.
Adaptive Support Ventilation: A Translational Study Evaluating the Size of Delivered Tidal Volumes
Authors: Veelo Denise P. , Dongelmans Dave A. , Binnekade Jan M. , Paulus Frederique , Schultz Marcus J.
Published: March 2018

Purpose

Adaptive support ventilation (ASV) is a microprocessor-controlled, closed-loop mode of mechanical ventilation that adapts respiratory rates and tidal volumes (VTs) based on the Otis least work of breathing formula. We studied calculated VTs in a computer simulation model, and VTs delivered in a test lung setting as well as in clinical practice.

Materials and Methods

In a computer simulation model using the Otis formula, VTs were calculated for increasing predicted body weights (from 50 to 80 kg) and increasing minute volumes (from 0.7 to 1.5 ml/kg). Different compliance-resistance combinations were chosen to mimic “acute lung injury (ALI)” (compliance 27 ml/cmH2O, resistance 20 cmH20 l/s), “ALI using an open lung approach” (compliance 50 ml/cmH2O, resistance 20 cmH20 l/s), “healthy lungs” (compliance 65 ml/cmH2O, resistance 20 cmH20 l/s) and “chronic obstructive pulmonary disease (COPD)” (compliance 80 ml/cmH2O, resistance 50 cmH2O l/s). In a test setting using a human ventilator connected to a test lung set to mimic similar pulmonary conditions, VTs delivered by the ASV were studied. In a series of stable intensive care unit patients after cardiothoracic surgery, the delivered VTs were collected and analyzed.

Results

VTs with the Otis formula resembled those in the test setting. With ALI, the ventilator delivered VTs between 6 and 8 ml/kg. With ALI using an open lung approach and with healthy lungs, the ventilator delivered VTs between 8 and 10 ml/kg. With COPD, all VTs were above 10 ml/kg. In patients after coronary artery bypass surgery ASV delivered VTs between 7 and 9 ml/kg and VTs never exceeded 10 ml/kg.

Discussion

The ASV performed as intended, bearing in mind that the ASV algorithm was originally designed to provide VTs between 8 and 12 ml/kg. However, the VTs that were calculated and delivered were frequently higher than those presently recommended in the guidelines. Considering the size of VT delivered in the setting of ALI using an open lung approach as well as in the setting of COPD, we feel caution should be taken when applying ASV in patients with these conditions.
Clinical Evaluation of Five Commercially Available Adult Oxygenators in Terms of Pressure Drop during Normothermic and Hypothermic Cardiopulmonary Bypass
Authors: Ji Bingyang , Wang Hongyue , Miao Na , Xing Jialin , Liu Wei , Liu Ruifang , Long Cun
Published: March 2018

Background

It is well documented that trans-membrane pressure drop (TMPD) of hollow-fiber membrane oxygenators (HFMO) may lead to hemolysis, damage to platelets, and systemic inflammatory response. The purpose of this study was to evaluate five commercially available adult oxygenators in terms of pressure drop during normothermic and hypothermic cardiopulmonary bypass (CPB).

Materials and Methods

In a clinical setting, 5 different adult HFMOs were tested in terms of TMPDs. Forty patients scheduled for cardiac surgery were enrolled in the study and were divided into 5 groups according to the type of oxygenator used during CPB: group J (Maquet Quardox n=8), group A (Affinity NT n=8), group P (Polystan Safe Maxi n=8), group T (Terumo Capiox SX 18 n=8) and group C (COBE APEX-TM n=8). Clinical parameters were collected during CPB, including mean arterial pressure (MAP), pump flow, temperature, hematocrit, duration of CPB, cross-clamp time and bypass time. TMPDs of pre-oxygenator and post-oxygenator pressures were recorded at the start of systemic cooling (T1), 10 min after stable hypothermia at 30°C (T2), and at termination of rewarming before the end of CPB (T3).

Results

There were no significant differences among the 5 groups in pump-flow rate, temperature, hematocrit, and mean arterial pressure during CPB. TMPDs of group J were the lowest at different time-points (T1, 30.71 ± 8.42mmHg; T2, 25.71 ± 5.41 mmHg; T3, 27.42 ± 13.01 mmHg). Compared to the other 3 groups (P, C and T groups), TMPDs of groups J and A at various time-points were lower (J group compared with the other three groups (p<0.001). Although TMPDs in groups A, P and T during hypothermia were higher than during normothermia and post-rewarming, there was no significant statistical difference (p> 0.05).

Conclusions

These results suggest that the HFMOs in groups J and A produced significantly lower TMPDs and pre- and post-oxygenator extracorporeal circuit pressures during normothermic and hypothermic CPB.
Mineral Water Administration may Increase Kidney Elimination of Urea, Creatinine and Folic Acid in a Concentration-Dependent Fashion
Authors: Calomino Francesco , Di Paolo Nicola , Nicolai Giulia , Miglio Antonio
Published: March 2018

Background

In a previous experimental study we showed that the administration of a large water load in a short time increases the urinary flow and the transport capacity in the excretory tract of the rabbit ureter. In human subjects drinking a water load of 25 ml/kgBW in 30 minutes, diuresis, creatinine and urea clearance increase more than in those drinking the same load in 24 hours.

Purpose

The aim of the present study was to investigate possible correlations between percent reduction and baseline values of serum urea, creatinine, folic acid, and magnesium in humans. Methods and results: 20 volunteers were divided in two groups. Subjects in group 1 received a water load of 25 ml/kgBW in 24 hours followed by the same load in 30 minutes. Subjects in group 2 received the same water load but in inverse order. Before and after each water administration, the following variables were measured and compared: diuresis, serum urea, creatinine, folic acid and magnesium concentration, and urea and creatinine clearance.

Results

Serum urea and folic acid concentration decreased up to 40% after administration of the water load in 24 hours. Serum creatinine concentration decreased up to 20% after administration of the water load in 30 minutes. The concentration drop of these metabolites increased with increasing baseline metabolite concentrations.
Therapy with Nucleos(t)ide Analogues: Current Role in Dialysis Patients
Authors: Fabrizi Fabrizio , Messa Piergiorgio , Dixit Vivek , Martin Paul
Published: March 2018

Hepatitis B virus (HBV) infection persists among patients undergoing maintenance dialysis in the industrialized world. Knowledge of the epidemiology and the natural history of HBV infection in dialysis patients has markedly improved but antiviral therapy for hepatitis B remains a significant challenge in this population. A variety of therapeutic options are now available for the treatment of chronic hepatitis B, including potent new nucleos(t)ide analogues, along with standard and pegylated interferon. The most extensive experience in the dialysis population has been with lamivudine. Although several questions about lamivudine use in dialysis patients remain unanswered, it has shown potent antiviral activity: the range of clearance of HBV viremia (HBV DNA) from serum is between 56% and 100% in dialysis patients with chronic hepatitis B. Its major limitation is emergence of resistance. Tolerance to conventional or pegylated interferon monotherapy is poor in the dialysis population. There is limited data regarding adefovir dipivoxil (ADV) therapy in the dialysis population, while very little information is available about the use of the newer agents, tenofovir and entecavir, in patients with renal failure. It is recommended that dialysis patients with persistent HBsAg seropositive status be evaluated for antiviral treatment and that the decision to treat be based on the potential benefits and risks of therapy including life expectancy, candidacy for kidney transplantation, and comorbidities. Hepatitis B is relatively uncommon among patients undergoing dialysis in developed countries and this clearly hampers prospective clinical trials aimed to evaluate the efficacy and safety of therapy with nucleos(t)ide analogues for chronic hepatitis B in this population.
Hemodynamic Performance of a Sutureless Anastomosis Device (the Graft Connector): A Numerical Study
Authors: Sun Anqiang , Fan Yubo , Deng Xiaoyan , Xu Zaipin
Published: March 2018

Sutureless anastomosis devices have been developed to facilitate arterial bypass surgery on the beating heart. However, these devices can significantly alter the hemodynamics at the end-to-side anastomosis and in the host artery, leading to the formation of thrombus or/and intimal hyperplasia (IH). In this study, a numerical analysis was performed on the hemodynamic performance of the Graft Connector (GC), a sutureless anastomosis device, under pulsatile flow conditions. The results showed that blood flow was severely disturbed in the GC model with the formation of vortices and flow stagnation at the bed and the toe, and distal to each of the stent struts, which led to low wall shear stresses and high oscillating shear indices in these regions. This may cause severe IH in the host artery and compromise the performance of the device. Based on the numerical study, suggestions were proposed for the design of the GC to improve its performance.
Feasibility of using Sodium Chloride as a Tracer for the Characterization of the Distribution of Matter in Complex Multi-Compartment 3D Bioreactors for Stem Cell Culture
Authors: Gerlach Jörg C. , Witaschek Tom , Strobel Catrin , Brayfeld Candace A. , Bornemann Reinhard , Catapano Gerardo , Zeilinger Katrin
Published: March 2018

The experimental characterization of the distribution of matter in complex multi-compartment three-dimensional membrane bioreactors for human cell culture is complicated by tracer interactions with the membranes and other bioreactor constituents. This is due to the fact that membranes with a high specific surface area often feature a hydrophobic chemical backbone that may adsorb tracers often used to this purpose, such as proteins and dyes. Membrane selectivity, and its worsening caused by protein adsorption, may also hinder tracer transfer across neighboring compartments, thus preventing effective characterization of the distribution of matter in the whole bioreactor.

Tracer experiments with sodium chloride (NaCl) may overcome some of these limitations and be effectively used to characterize the distribution of matter in complex 3D multi-compartments membrane bioreactors for stem cell culture. NaCl freely permeates most used membranes, it does not adsorb on uncharged membranes, and its concentration may be accurately measured in terms of solution conductivity. In this preliminary study, the feasibility of complex multi-compartment membrane bioreactors was investigated with a NaCl concentration pulse challenge to characterize how their distribution of matter changes when they are operated under different conditions. In particular, bioreactors consisting of three different membrane types stacked on top of one another to form a 3D network were characterized under different feed conditions.
A Starr-Edwards Mitral Prosthesis after 44 Years of Good Performance
Authors: De Santo Luca Salvatore , De Feo Marisa , Della Corte Alessandro , Cerasuolo Flavio , Santè Pasquale , Torella Michele , Nappi Gianantonio
Published: March 2018

The Starr-Edwards caged-ball prosthesis has been widely used to replace cardiac valves. The Model 6120 mitral prosthesis was introduced on the market in 1965 to reduce the high incidence of ball variance and thromboembolism of the previous model. We report the case of a Starr-Edwards Model 6120 which had been in place for 44 years and was still well functioning with no apparent structural damage.
Deranged Mineral Content in the Bone of Patients with Chronic Renal Failure, Estimated by Computed Tomography
Authors: Marumo F. , Sakurai K. , Sato N. , Shimada H. , Iwanami S.
Published: March 2018

To evaluate the extent of renal osteodystrophy in patients with chronic renal failure, the CT numbers of the lateral condylus and mid-shaft of the femur were measured. To adjust for variation due to measurement conditions, calibration phantom was simultaneously scanned with the femur. The CT numbers of the lateral condylus were significantly lower than the control in both nondialyzed (p < 0.005) and dialyzed patients (p < 0.05). The CT numbers of the mid-shaft of the femur in dialyzed patients correlated significantly to the duration of hemodialysis (r = 0.807, p < 0.001). In 15 patients subjected to both CT scan and the photon absorptiometry, the CT numbers of the lateral condylus positively correlated to the mineral content of the radial (r = 0.57) and ulnar (r = 0.69) bones as calculated by photon absorptiometry. These results indicate that the CT scan can be used to estimate bone mineral content quantitatively, and is useful tool for evaluating renal osteodystrophy in patients with chronic renal failure.
Hemoperfusion of Phencyclidine in the Dog
Authors: Allen W.R. , O'Barr T.P. , Corby D.G.
Published: March 2018

Experiments were conducted to determine whether charcoal hemoperfusion (HP) would be useful in severe phencyclidine (PCP) overdose. Dogs were given a single 5 mg/kg injection of PCP. In 6 experiments HP for 2.5 hours was done; and in 6 control experiments, the extracorporeal circuit contained no HP cartridge. The number of seizures, symptoms, duration of coma, and PCP concentrations in the tissues of HP dogs were not different from control. PCP clearance by HP was 67 ± 16.5 ml/min. PCP recovery by HP was 2.25 ± 0.25 mg (2.0% of the administered dose). Urinary excretion of PCP was 1.33 ± 0.46 mg (1.2% of the dose). Volume of distribution of PCP was 21.8 ± 1.7 L/kg. Due to the high volume of distribution, high lipid solubility and low plasma levels of PCP, HP was not effective in managing PCP overdose in the dog.
Biochemical and Clinical Evaluation of a New Cellulose Diacetate Secondary Filter for Cascade Filtration
Authors: Valbonesi M. , Tarantino M. , Montani F. , Florio G. , Romorini A.
Published: March 2018

We have performed 24 cascade filtration treatments in 8 patients with hyperviscosity syndrome (2 cases), essential mixed cryoglobulinemia, post-hepatitic cryoglobulinemia, Sjogrens disease, rheumatoid vasculitis, Miller-Fisher syndrome and chronic dysimmune polyneuropathy. New cellulose diacetate filters were employed, giving a satisfactory performance. At 1.5 L plasma treatment, the rejection rate for macromolecular plasma components was close to 90%, whereas albumin recovery was close to 70%. Treatments were clinically effective, confirming that cascade filtration is an alternative to conventional plasma exchange in patients with IgM or immune complex mediated diseases.
A New Hemodialysis Monitoring Device Using Filtrate Concentrations: A Comparison with Standard Serum Techniques
Authors: Munaretto G. , Bonadonna A. , Piccoli A. , Sama C.
Published: March 2018

A new device allowing sampling to be performed at any time, and using the filtrate obtained during hemodialysis is described. The device was used in 27 patients undergoing regular dialysis.

Urea, creatinine and potassium were measured in samples taken both from arterial blood and from the device at 10, 40, 120 and 230 minutes after the beginning of the dialysis.

The results were compared.

A constant bias of about 10% was noted between the two sets of results but statistical analysis showed this was correctable.
Amino Acid Absorption of Plasmapheresed Serum by Resins and Charcoal
Authors: Alp M.H. , Lipschitz E.
Published: March 2018

The amino acid absorption capacity of two types of charcoal and six forms of ion exchange resin has been assessed. To plasmapheresed serum obtained from human donors amino acids were added to stimulate the levels seen in hepatic failure. This was passed through columns of either resin or charcoal over three hours. The amino acid absorption was estimated. Charcoal consistently removed greater amounts of essential amino acids than resin. None of the ion exchange resins were found to be effective in amino acid absorption.