bluuebunny/crossref_metadata_2025 huggingface dataset:
Improved Biocompatibility of Heparin Surface-Coated Ventricular Assist Devices
Authors: Von Segesser L.K. , Weiss B.M. , Hänseler E. , Bisang B. , Leskosek B. , Von Felten A. , Turina M.
Published: March 2018

Heparin surface coated ventricular assist devices (VADs) and cannulas were evaluated in comparison to uncoated VADs in 10 bovine experiments (body weight 77 ± 6 kg). All systems were primed with cristalloid solution. No systemic heparin was given. Left ventricular assist was started with a blood flow of 4.2 ± 0.4 l/min and maintained over 6 hours. Besides hemodynamic monitoring, blood samples were taken at regular intervals for blood gas, hematological, biochemical and coagulation studies. All animals in the study group (coated) were assisted for the scheduled 6 hours without device failure. In the control group, however, total occlusion occurred in 1 VAD after 1 hour of left ventricular assist whereas the other 4 VADs remained functional throughout the protocol. Mixed venous oxygens saturation was preassist 56 ± 12% for coated versus 63 ± 11% for uncoated and the final value at 60 minutes after weaning was 58 ± 16% versus 59 ± 5% (NS). Mean hematocrit dropped from a baseline value of 33 ± 4% for coated versus 29 ± 8% for uncoated to 29 ± 7% versus 30 ± 5% (NS) after 6 hours of assist. There was no significant difference between the baseline values (5.7 ± 3.0/jmol/l for coated versus 4.6 ± 3.1/umol/l for uncoated) and the 6-hour values (3.8 ± 3.7/umol/l versus 7.6 ± 6.4/jmol/l) for mean plasma hemoglobine. The normalized platelet levels dropped after 10 minutes of assist to 91 ± 21% for coated versus 94 ± 49% for uncoated (NS) and 89 ± 29% versus 65 ± 44 at 6 hours (NS). The activated clotting time evolved from a baseline value of 127 ± 12 s for coated versus 131 ± 5 s for uncoated (NS) to 122 ± 17 s versus 139 ± 18 s at 60 minutes after assist (NS). Renal embolus score showed a mean level of 11 ± 8 for coated versus 15 ± 12 for uncoated. The VAD clot score showed a mean level of 0.2 ± 0.4 for coated versus 2.2 ± 1.6 for uncoated (p < 0.5). We conclude, that heparin coating of blood exposed surfaces provides significant improvement of VAD biocompatibility.
Characterisation and Evaluation of a New Double Lumen Central Venous Catheter
Authors: Donnelly P.K. , Morton D. , Woffindin C. , Hoenich N.A.
Published: March 2018

The performance of a new double lumen central venous haemodialysis catheter was tested in two laboratory models. In a bench model the patient's venous system was simulated by a reservoir from which water or glycerol was drawn through a fixed tube. A double lumen silastic catheter was then inserted into the tube, as it would in a major vein, with the tip directed away from the direction of flow. The catheter was linked to a dialysis circuit incorporating pressure sensors and dye was infused at constant rate so that recirculation at the tip could be measured and found to be less than 5%. The same catheters were inserted operatively into the superior vena cava via the external jugular vein of three pigs (weight 27-31 kg). The catheters remained patent for four weeks and when connected to an extracorporeal circuit had recirculation and pressure flow characteristics comparable to the bench model in the range 50-400 ml/min. The new double lumen catheter is worthy of clinical evaluation.
Hemodynamic and Cardiac Effects of Erythropoietin in Patients on Regular Dialysis
Authors: Pascual J. , Teruel J.L. , Marcén R. , LiañO F. , Moya J.L. , Jiménez M. , Ortuño J.
Published: March 2018

The long-term impact of erythropoietin (EPO) treatment on cardiac structures and function was prospectively studied in eight hypertensive (Group I) and seven normotensive (Group II) patients on hemodialysis (HD). Doppler-echocardiograms were done before EPO and at two and twelve months of treatment. Mean hemoglobin (± SD) before EPO was 6.4 ± 0.9; it rose significantly up to two months and then remained constant. At two months, cardiac index (CI) had significantly decreased, while peripheral vascular resistances increased. Five patients required increased antihypertensive drug treatment. No changes were seen in myocardial parameters at this short follow-up. After one year, left ventricular mass index (LVMi) decreased (p < 0.05) in both groups concomitantly with a decrease in diastolic diameter and septum and posterior wall thicknesses. Basal LVMi was higher in Group I than in Group II, and after one year the regression was more marked in Group II. Left cardiac work showed prompt and steady improvement in both groups. Maintained partial correction of anemia with EPO during one year was associated with a return to normal of high CI, decreased left cardiac work and impressive regression of left ventricular hypertrophy.
Dynamic Catheterography in the Early Diagnosis of Peritoneal Catheter Malfunction
Authors: Scabardi M. , Ronco C. , Chiaramonte S. , Feriani M. , Agostini F. , La Greca G.
Published: March 2018

The dynamic catheterography is an imagin technique that allows to study the peritoneal solution inflow and outflow phases in case of catheter malfunction. The examination is carried out in three subsequent steps: 1) direct examination without contrast media in order to define the position of the catheter inside the abdomen; 2) low speed catheterography by normal injection of 10 ml of hydrosoluble contrast medium to verift the patency of the cannula; 3) high speed catheterography by 30 ml hydrosoluble dye injected with an automateds high pressure system to study the inflow phase, the fluid distribution in the peritoneal cavity and the patency of the catheter holes. Different radiographic patterns can be found: dislocation of the catheter tip, KinKing, one way obstruction, inner lumen obstruction. The procedure is simple, safe and reliable for a correct diagnosis and for the choice of a successfull therapeutic approach to peritoneale catheter malfunction.
A Cardiac Assist Device as Blood Supply in Ischemic Heart Disease
Authors: Beyer M. , Hoffer H. , Beyer U. , Mierdl S. , Hannekum A.
Published: March 2018

Before the event of modern bypass surgery revascularisation of the heart was tried with the transplantation of pedicled muscle flaps onto the heart. For patients who cannot undergo bypass surgery this method could be –- in a modified way –- of help. This was shown in 12 dogs. In those a free muscle flap was transplanted onto the heart which had undergone a previous artificial infarction. The muscle flap was anastomosed with the a. mammaria, venous flow was directed into the right atrium. After 5 months the muscle was almost completely atrofic, but a fit capillary network was penetrating the underlying myocardium
In Vivo Clearance and Elimination of Nine Marker Substances during Hemofiltration with Different Membranes
Authors: Krämer B.K. , Pickert A. , Hohmann C. , Liebich H.M. , Müller G.A. , Hablitzel M. , Risler T.
Published: March 2018

The handling of low, middle and high molecular weight markers was examined in seven stable dialysis patients during hemofiltration with different membranes. Four membranes were examined in a randomized, crossover order (polysulfone, polyamide, AN69 polyacrylonitrile, Asahi polyacrylonitrile) by measuring plasma and dialysate concentrations of phosphate, creatinine, vitamin B12, β2-microglobulin, furanic acid, hippuric acid, retinolbinding protein, alpha-1-antitrypsin, and albumin. Sieving coefficients and plasma clearances of β-microglobulin or retinol-binding protein were markedly or slightly lower during hemofiltration with the Asahi polyacrylonitrile membrane than with the other membranes (highest removal with polysulfone/AN69 polyacrylonitrile membranes). No differences of obvious clinical relevance could be seen between the four membranes. A high β2-microglobulin removal rate might be important to prevent dialysis-associated amyloidosis.
Biocompatibility of High-Flux Membranes
Authors: Putz D. , Barnas U. , Luger A. , Mayer G. , Woloszczuk W. , Graf H.
Published: March 2018

Standard dialysis with cuprophane membranes is known to stimulate the immune system. As a result of activation of macrophages various interleukins and tumor necrosis factor (TNF) are secreted, presenting further evidence of the poor biocompatibility of cuprophane. We investigated the immunogenic properties of three modern high-flux membranes. Seven patients were studied during hemodiafiltration sessions using either a polysulfone (F60, Fresenius), a polymethylmetacrylate (BK 2.1, Toray) or a cellulose triacetate (FB-210 U, Nipro) dialyzer in a hemodiafiltration procedure. Serial measurements were made during each treatment of interleukin-1β (II-1β), TNF, soluble IL-2 receptor (sII-2r), soluble CD4 (sCD4), soluble CD8 (sCD8), interferon gamma (IFNg) and neopterin. In contrast to the known increase of IL-1β, IL-2r and TNF with cuprophane membranes, none of the modern high-flux dialyzers stimulated the production of these factors. Significant decreases of neopterin and sCD4 were observed. IFNg and sCD8 did not change significantly. Our results suggest that the modern high-flux dialyzers are non-immunogenic, and thus provide further evidence of the superior biocompatibility of synthetic or semisynthetic membranes over the conventional cuprophane.
Blood Flow Rate and Access Recirculation in Hemodialysis
Authors: Daniels I.D. , Berlyne G.M. , Barth R.H.
Published: March 2018

We studied the effect of extracorporeal blood flow rate (BFR) on access recirculation (recirc) in 19 hemodialysis patients. BUN was determined in simultaneous peripheral (P), arterial (A), and venous (V) blood obtained at BFRs of 200, 400 and 600 ml/min. Percent recirc was calculated for each BFR using the formula (P-A) / (P-V) X 100. Venous drip-chamber (VP) and pre-blood-pump (AP) pressures were measured at each BFR. Fistulograms were performed in 10 patients, and stenoses were identified in 5, all at the proximal (arterial) end of the access. Recirc increased with increasing BFR from 200 to 400 ml/min but increased little from 400 to 600 ml/min. At all BFRs recirc in the stenotic patients was higher than that of non-stenotic or unstudied patients. Urea clearance, corrected for recirc, rose with blood flow both in stenotic and non-stenotic patients. There were no differences in AP or in VP between stenotic and non-stenotic patients. At BFR ≥ 400 ml/min, a recirc threshold of 15% identified stenoses with sensitivity 100% and specificity 71%. We conclude (1) recirc increases with increasing BFR but not enough to outweight the concomitant increase in urea clearance; (2) significant access stenosis and recirc may be present even with low VP; (3) recirc was associated with arterial side stenoses; (4) at BFR ≥ 400 ml/min, access stenosis is associated with recirc > 15%.
Dynamic Pumping Performance of the Hemopump®-A Small Intraventricular Blood Pump
Authors: Kunst E.E. , Van Alsté J.A.
Published: March 2018

We studied the pumping characteristics of the Hemopump®, a commercially availabe miniature intraventricular blood pump for temporary support of failing hearts. The Hemopump® is an axial flow pump of which the characteristics can be described by turbomachine theory. Experiments with water and a mock circulation verified that the pumping characteristics of the Hemopump®, in terms of both pressure head and flow as a function of rotational speed, very well can be described by a first order differential equation. The influence of blood with its non-Newtonian character is being investigated
Hemocompatibility of Titanium Nitride
Authors: Dion I. , Baquey C. , Candelon B. , Monties J.R.
Published: March 2018

The left ventricular assist device is based on the principle of the Maillard-Wenkel rotative pump. The materials which make up the pump must present particular mechanical, tribological, thermal and chemical properties. Titanium nitride (TiN) because of its surface properties and graphite because of its bulk characteristics have been chosen. The present study evaluated the in vitro hemocompatibility of TiN coating deposited by the chemical vapor deposition process. Protein adsorption, platelet retention and hemolysis tests have been carried out. In spite of some disparities, the TiN behavior towards albumin and fibrinogen is interesting, compared with the one of a reference medical grade elastomer. The platelet retention test gives similar results as those achieved with the same elastomer. The hemolysis percentage is near to zero. TiN shows interesting characteristics, as far as mechanical and tribological problems are concerned, and presents very encouraging blood tolerability properties.
Fast Lysis by Complement and Uptake by Liver of Avidin-Carrying Biotinylated Erythrocytes
Authors: Muzykantov V.R. , Seregina N. , Smirnov M.D.
Published: March 2018

The fate of 51Cr-labelled avidin-carrying biotinylated erythrocytes after intravenous injection in the rat was examined. Surface amino groups of the erythrocyte membrane were modified by biotin N-hydroxysuccinimide ester. The biodistribution and stability of biotinylated erythrocytes in the blood were similar to those of non-biotinylated cells. Both types of cells circulated in the bloodstream for prolonged periods of time without substantial lysis (about 2-3% of injected radioactivity per g of blood for 24-48 hours, no more than 2% of lysis). Both types of erythrocytes were cleared by the spleen. The clearance of biotinylated cells was faster and more pronounced (peak of spleen uptake at 3 hours after injection, up to 35% of injected radioactivity per g of spleen), than that of non-biotinylated cells (peak of spleen uptake at 24 hours after injection, up to 25% of injected radioactivity per g of spleen). Attachment of avidin to biotinylated cells results in extremely rapid lysis and clearance from the bloodstream (0.17% of injected radioactivity per g of blood 30 min after injection, 100% lysis). Radioactivity was rapidly cleared by the liver (up to 80% of injected dose per g of tissue, 70% per organ). Uptake by the spleen plays only a minor role in the clearance. Considerable lung uptake of avidin-carrying biotinylated erythrocytes was observed. Avidin-carrying biotinylated erythrocytes were lysed by fresh homologous serum in vitro in contrast to biotinylated and native cells. Lysis was eliminated by pretreatment of serum with EDTA or heating, which indicates a complement-dependent mechanism of lysis.
Variables Associated with the Assessment of Systemic Tumor Necrosis Factor Alpha Levels during Hemodialysis
Authors: Jörres A. , Froese P. , Fischer C. , Safak H. , Gahl G.M. , Müller C. , Vienken J.
Published: March 2018

Conflicting results have been published concerning the systemic induction of the cytokine tumor necrosis factor alpha (TNFα) during hemodialysis (HD). We therefore evaluated in vitro TNFα production in whole blood as well as in vivo variability of TNFα levels in patients on long-term HD. Whole blood was incubated at room temperature (RT) with or without exogenously added endotoxin (ET), and plasma-TNFα was measured after 5, 30, 120, 240, and 960 min by specific enzyme immunoassay. Additionally, plasma-TNFα before and after 120 and 240 min HD was studied longitudinally once a week over a period of 4 weeks in 36 patients on Cuprophan® (CU, n=23) or polysulfone-F60 (PSu, n=13) HD. Mean plasma TNFα levels in vitro rose from (mean) 8 pg/ml after 5 min to 12 pg/ml (120′) and 32 pg/ml (960′) even without ET addition, and to 18 pg/ml (after 120′) and 88 pg/ml (after 960′) when 0.1 μg/ml ET were added. Pre-dialytic as well as intradialytic TNFα levels in patients showed high intra-individual variability. A substantial (> 100%) increase in plasma TNFα was observed during only 14 out of 84 treatments with CU and 20 out of 47 with PSu, however, the increase in TNFα was not statistically significant in either group. We conclude that the sampling procedure, if not carefully standardized, is a potential source of artifacts with regard to “systemic” TNFα levels. The high intra and inter-individual variability of plasma TNFα suggests that results of cross-sectional studies are questionable.
Neutrophilic Intracellular Acidosis Induced by Conventional, Lactate-Containing Peritoneal Dialysis Solutions
Authors: Yu A.W. , Zhou X.J. , Zhou F.Q. , Nawab Z.M. , Gandhi V.C. , Ing T.S. , Vaziri N.D.
Published: March 2018

Exposure of human neutrophils to a conventional, acidic, lactate-containing peritoneal dialysis solution (PDS) resulted in the development of a prompt and substantial intracellular acidosis. It is possible that this intracellular acidosis contributes to cellular dysfunction.
Hemoperfusion with a New Anion Exchange Resin Corrects the Metabolic Alkalosis in Pyloric Stenosis: An Experimental Demonstration
Authors: Faenza S. , Balestri M. , Martinelli G. , Spighi M. , Fini M. , Giardino R. , Colì L. , Cianciolo G. , Stefoni S. , Bonomini V.
Published: March 2018

An experimental model of hypertrophic pyloric stenosis was made by suture of the pyloric wall and gastrostomy in 10 rabbits under general anesthesia. Blood sampling indicated severe alkalosis and hypochloremia 3h 30 min after surgery. To correct the derangement, we tested an ion exchange resin (Dowex SAR), coated with a methacrylic hydrogel. A cartridge containing 18 g of this resin was inserted in an extracorporeal circuit. This chloride charged resin achieved uptake of HCO−3 ions, and elution of CI− ions. The electrolytic balance was fully restored after 10 min of treatment.
In Vitro Hemolysis by Mechanical Heart Valve Prostheses with Tilting Disc
Authors: Wendt M.O. , Pohl M. , Pratsch S. , Lerche D.
Published: March 2018

Hemolytic and subhemolytic blood damage by mechanical heart valve prostheses have been observed in both clinical and in vitro investigations. A direct comparison between these studies is not possible. Nevertheless the transfer of some in vitro results to the behaviour of the valve in situ may be performed considering the similarity principle. This requires the use of dimensionless similarity numbers such as the plasma's hemoglobin concentration (PHb) or others, instead of dimensioned parameters. To evaluate the in vitro hemolysis of valve prosthesis a test chamber filled with human banked blood was used. An artificial ventricle ensuring an oscillatory flow through the valve was also used. The rise of PHb was evaluated in terms of a similarity number, called the lysis number. This number describes the probability of destroying a single red blood cell participating once in the hemolytic process under consideration. The lysis number, a Björk-Shiley valve (TAD 29), was found to be in the order of 2 × 10−4. From this, the survival time of erythrocytes in patients with an artificial heart valve was estimated. It was found to be in the order of 20 d of T50 Cr in agreement with clinical results
Liquid Phase Enzyme Reactor, a New Bioreactor Principle
Authors: Schmer G.
Published: March 2018

One of the drawbacks of solid phase enzyme reactors is the sharp decrease in substrate affinity as shown by an increase in the Km app value. To circumvent this problem a liquid phase enzyme reactor system was designed. Biotin labeled L-Tryptophan side chain oxidase (TSO) was directly injected into the plasma circuit of a filter plasmaphoresis system of rabbits and adsorbed onto an Avidin column prior to its reentry into the animal's general blood circulation. In five experiments total L-Tryptophan depletion could be observed in the plasma circuit during 60 minutes of the experiment with complete readsorption of the enzyme to the Avidin column.
Effects of 1,25 (OH)2 D3 Treatment on Lipid Levels in Uremic Hemodialysis Patients
Authors: Yeksan M. , Türk S. , Polat M. , Çiǧli A. , Erdoǧan Y.
Published: March 2018

The aim of this study was to evaluate the effect of 1,25 (OH)2D3 treatment on lipid levels in uremic hemodialysis (HD) patients. Thirty-one HD patients who had never been treated with vitamin D nor related drugs and 12 healthy subjects with normal renal functions were studied. Uremic HD patients were randomly divided into two groups. Sixteen uremic HD patients were treated with oral calcitriol (0.5 μg/day) for 8 weeks. 13 uremic HD patients and 12 healthy subjects were given placebo. In all these cases before and after 8 weeks of treatments; serum total lipid, total cholesterol, HDL-cholesterol, LDL-cholesterol and triglycerid levels were determined. After calcitriol treatment, triglycerid levels were significantly decreased. But total lipid, cholesterol, HDL-cholesterol and LDL-cholesterol levels did not significantly change. In the other two groups there were no significant changes. These results show that calcitriol treatment has a positive effect on triglycerid levels in uremic HD patients. This effect of mechanism of calcitriol treatment has not been known yet. But it could be due to regulation carbohydrates metabolism and normalization of parathormone (PTH) levels.
Improvement of Survival Rate in Patients with Cardiogenic Shock by Using Nonpulsatile and Pulsatile Ventricular Assist Device
Authors: Minami K. , El-Banayosy A. , Posival H. , Seggewiβ H. , Murray E. , Körner M.M. , Körfer R.
Published: March 2018

Between January 1988 and January 1992, 65 patients (pts) had a ventricle assist device (VAD) inserted in our clinic. In 24 pts a VAD was applied because of primarily unsuccessful weaning from cardiopulmonary bypass (Group A). In a further 24 pts (Group B) a VAD was installed for the therapy of refractive cardiogenic shock (CS) after initially successful cardiac surgery (n=21) and after acute myocardial infarction (n=3). Twelve pts were bridged to heart transplantation (Group C) and five had a VAD inserted for various other reasons (Group D). In 36 (55.4%) of the total 65 pts a nonpulsatile VAD (Biomedicus® 540) was used: 10 in Group A; 20 in B, 3 in C and 3 in D. In 29 pts (44.6%) a pulsatile VAD (Abiomed® BVS 5000) was used: 14 in Group A, 4 in B, 9 in C and 2 in D. Weaning rate and long-term survival rates were 50% and 46% respectively in Group A and 38% and 42% in Group B. Seven pts from Group C were transplanted and six are long-term survivors. Two pts (40%) in Group D were discharged from hospital. Major postoperative complications were bleeding (46%), thromboembolism (14%), multiple organ failure (11%), renal failure (11%), arterial embolism (4.6%), sepsis (3%). The results indicate that application of a VAD can be recommended in pts with postcardiotomy CS to allow recovery of cardiac function and in pts with irreversible ventricular damage as bridging to HTX.
Modelling the Optimal Control of Cyclical Leg Movements Induced by Functional Electrical Stimulation
Authors: Veltink P.H. , Franken H.M. , van Alsté J.A. , Boom H.B.K.
Published: March 2018

An optimal control strategy for FES-induced cyclical leg movements in paraplegics is proposed. The control of the cyclical movement of a freely swinging leg is considered as an example. Quadriceps and the flexion withdrawal reflex are stimulated in order to generate a cyclical movement, of which the forward swing resembles the swing phase of gait. Optimal stimulation patterns are determined on the basis of an optimization criterion and a dynamic model of the system. The criterion is based on desired movement parameters and a minimal duration of the stimulation bursts. The movement parameters should ensure the generation of the desired cyclical movement: a desired hip angle range, sufficient foot clearance during the forward swing and knee extension at the beginning of the backward swing. Minimal duration of the stimulation bursts is assumed to yield minimal fatigue. A dynamic model, describing the dynamics of the neural system, the muscles and the leg, was constructed and its parameters identified on the basis of preliminary experiments and literature. Optimal timing of the quadriceps and flexion reflex stimulation bursts was determined by means of computer simulation. These simulations predicted that the flexion reflex should be stimulated in a short burst approximately 150 ms before the start of the forward swing. The quadriceps should be stimulated approximately starting 200 ms before the end of the forward swing in order to ensure knee extension at the beginning of the backward swing. The duration of one cycle of the movement was between 1300 and 1500 ms in these simulations. These results predict that the movement specified by the functional objectives can be realised using only two channels of stimulation. On the basis of the optimal timing, an adaptive control strategy can be designed, which varies the stimulation burst width when muscles fatigue.
Plasma Na-K Atpase Inhibitor Activity and Intracellular Ions during Hemodialysis
Authors: Krzesinski J.M. , Du F. , Pequeux M.L. , Rorive G.L.
Published: March 2018

We have investigated the relationship between plasma Na-K ATPase inhibitor activity (EDLS) and intracellular ions in 37 uremic hemodialysed hypertensive patients, and in 20 normotensive non uremic controls (NC). As compared with the NC population, significantly enhanced values for erythrocyte (RBC) Na, Ca, platelet cytosolic Ca and EDLS were observed in all the uremic patients tested just before a dialysis session, as well as a decrease in RBC Ca ATPase and in the platelet pH. In uremia, significant correlations have been noted between RBC Na and platelet Ca (r = 0.6) or systolic BP (r = 0.45); between platelet Ca and systolic blood pressure (r = 0.8) or diastolic BP (r = 0.5) and between EDLS and RBC Na, Ca or platelet Ca (r = 0.5). Anti-hypertensive treatment has no influence on these parameters. During dialysis, a significant decrease has been noted in RBC Na, Ca, platelet Ca, SBP (only in untreated patients) and EDLS and an increase in RBC Ca ATPase and platelet pH. These modifications are significantly correlated with the weight change.
Maintaining the Patency of Double-Lumen Silastic Jugular Catheters for Haemodialysis
Authors: Uldall R. , Besley M.E. , Thomas A. , Salter S. , Nuezca L.A. , Vas M.
Published: March 2018

A system has been developed for maintaining the patency of double lumen silastic jugular catheters in patients with refractory vascular access problems. Most patients receive a small daily dose of aspirin. Selected patients also receive warfarin to maintain a prothrombin time (PT) of 15, 20, or 30 seconds. Inadequate blood flow due to thrombus obstruction can be overcome by the intravenous administration of urokinase, 250.000 units. This can be administered safely to outpatients provided that heparin is not given simultaneously. Occasionally a second dose may be required. By adopting this policy all catheter obstructions have been overcome. The danger of iatrogenic bleeding cannot be discounted. Warfarin therapy must be very closely monitored.
Different Stroke Volumes for the Left and Right Ventricles in the Moving-Actuator Type Total Artificial Heart
Authors: Min B. , Kim I. , Kim H.
Published: March 2018

A new electromechanical moving-actuator type total artificial heart (TAH) has been developed to solve the imbalance problem without an extra compliance chamber. A different stroke volume was achieved by the large left sac size and the asymmetry of the actuator motion referred to the center position. The left ventricle consists of a double sac with the outer sac attached to the actuator providing active diastolic filling, while the double sac of the right ventricle being free from the actuator, and having sufficient suction produced due to the rigid pump housing. The stroke volume difference between the left and right sac is compensated through the air in the interventricular space of the variable volume (VV) space. Computer simulation based on the geometrical relationships between the blood sacs and the actuator was performed to simulate the physical mechanisms of the moving-actuator type TAH. Results were then compared with the measured pressure changes in various chambers of the pump and the stroke volume differences in mock circulation test. In two acute calf experiments, the balanced left and right atrial pressures were achieved in the moving-actuator type TAH without an extra compliance chamber
A Technique for the Laboratory Determination of Recirculation in Single Needle Dialysis
Authors: Hoenich N.A. , Smirthwaite P.T. , Woffindin C. , Lancaster P. , Frost T.H. , Vanholder R.
Published: March 2018

Recirculation is an important factor in single needle dialysis and, if high, can compromise treatment efficiency. To provide information regarding recirculation characteristics of access devices used in single needle dialysis, we have developed a new technique to characterise recirculation and have used this to measure the recirculation of a Terumo 15G fistula needle and a VasCath SC2300 single lumen catheter. The experimentally obtained results agreed well with those established clinically (8.5 ± 2.4% and 18.4 ± 3.4%). The experimental results have also demonstrated a dependence on access type, pump speeds and fistula flow rate. A comparison of experimental data with theoretical predictions showed that the latter exceeded those measured with the largest contribution being due to the experimental fistula.
The Epidermo-Peritoneal Potential in Patients Treated with Continuous Ambulatory Peritoneal Dialysis
Authors: Davenport A. , Dealler S.F.
Published: March 2018

At physiologic pH, S. epidermidis moves along an electrical potential gradient. We measured the epidermo-peritoneal electrical potential (EPP) in 23 end-stage renal failure patients treated with CAPD. There was a negative correlation between the mean EPP and the patient's age (r=0.47, p=0.016), but no correlation between the mean EPP and the duration of treatment (r=0.003, p=0.5). The EPP was greater in those patients with a history of recurrent bacterial peritonitis due to S. epidermidis [median EPP 23 mv (95% confidence limits 16-51)] compared to those with only one or no episodes of bacterial peritonitis due to S. epidermidis infection [11 mv (9-17), p<0.05]. Thus electrical gradients caused by the presence of the CAPD catheter could contribute to colonisation and subsequent infection by skin commensals, by aiding bacterial migration.
Catecholamine Infusion versus Intraaortic Counterpulsation at the Initial Phase of Left Intraventricular Balloon Pumping in the Fibrillating Animal Heart
Authors: Stamatelopoulos S. , Zakopoulos N. , Saridakis N. , Stefanou S. , Adractas A. , Kanakakis J. , Vinieratos N. , Zoumis G. , Gougoulakis A. , Moulopoulos S.
Published: March 2018

This experimental study compares the effect of catecholamine infusion to the effect of intraaortic counterpulsation (IABP) while initiating intraventricular balloon pumping (IVBP) in the fibrillating heart. In 12 dogs IVBP started immediately after the induction of ventricular fibrillation. Intravenous adrenaline or noradrenaline (at a progressively increasing infusion rate until the systolic aortic blood pressure was 120 mm Hg) was interchanged with IABP. The systolic aortic pressure, the aotic flow and the mean left atrial pressure were, respectively, 120.4 ± 0.5 mm Hg, 42 ± 4 mlkg-1min-1 and 18.7 ± 1.2 mm Hg (x ± SEM) ten min after initiating catecholamine infusion and 97 ± 5 mm Hg (with a 131 ± 4 mm Hg diastolic wave), 69.6 ± 4 mlkg-1min-1 and 16 ± 1.5 mm Hg ten min after initiating IABP. The difference in aortic flow was significant (p<0.001). The results indicate that a better aortic flow may be obtained by combining IVBP and IABP than IVBP and vasoconstrictive agents in the fibrillating heart. If IVBP, IABP and catecholamines are combined, both AF and AP may increase.
In Vivo Accumulation of Sodium Pump Inhibitor by Normal and Uremic Erythrocytes
Authors: Gallice P. , Lai E. , Brunet P. , Berland Y. , Elsen R. , Crevat A.
Published: March 2018

A uremic toxin fraction (fraction 2-3-1) in the middle molecular mass range (300-2000 Da) containing a sodium potassium inhibitor pump was studied. As fraction 2-3-1 was known to be present in minute quantities in urine and plasma, erythrocyte lysates were used as an alternative source. Results show that fraction 2-3-1 is more abundant in erythrocytes than in normal urine. In addition, the fraction is present in a greater quantity in uremic erythrocytes than in normal blood cells. It is concluded that fraction 2-3-1 is concentrated at the erythrocyte level in uremic patients
Albumin Treatment Reduces in Vitro Platelet Deposition to Pmma Dialysis Membrane
Authors: Remuzzi A. , Boccardo P.
Published: March 2018

We investigated in an in vitro system the effect of albumin on the interaction between circulating platelets and artificial membranes used for hemodialysers. Using a recently described method we evaluated platelet adhesion to polymethylmethacrylate (PMMA) and cuprophan (CU) hollow-fibers. Deposition of washed radiolabelled platelets on these two membranes was measured in small dialysis filters with or without previous perfusion with an albumin solution. Also measured was the amount of albumin that adhered to the membranes after perfusion of the filters with radiolabelled albumin. Platelet deposition to PMMA was significantly reduced by albumin treatment (from 1070 ± 498 to 296 ± 174 plt/mm2, P < 0.01). Platelet deposition on the CU membrane was comparable with and without albumin pre-perfusion (141 ± 70 vs. 152 ± 100 plt/mm2). Deposition of radiolabelled albumin was higher on PMMA than on CU membrane. Thus, higher adborption of this protein, observed in our in vitro system, might explain the lower platelet deposition found on the PMMA rather than on the CU membrane. These results suggest that platelet interactions with PMMA during dialysis could be improved by treating the dialyser with albumin before blood contact. However, before this treatment is used clinically further experimental studies are required to confirm that our in vitro observation also applies to in vivo conditions.
Disseminated Tuberculosis in a Renal Transplant Recipient Presenting as a Non-Healing Skin Ulcer. A Case Report
Authors: Ghosh A.K. , Verma P.P. , Jha V. , Gupta K.L. , Sakhuja V. , Chugh K.S.
Published: March 2018

Cutaneous tuberculosis in renal allograft recipients is rare. A 33 year old recipient of a second renal allograft developed a painless ulcer on the left foot two months after surgery, followed by the appearance of a cold abscess in the left inguinal region. Smear from the pus aspirated from this abscess revealed acid fast bacilli, and biopsy from the edge of the ulcer showed an epitheloid cell granuloma with Langhans type of giant cells. X-ray of the chest revealed miliary mottling in both lung fields. Antitubercular therapy lead to a complete resolution of the tuberculous lesions
Photochromic Flow Visualization for the Investigation of Artificial Heart Valves
Authors: Yurechko V.N.
Published: March 2018

A new method for the investigation of hydrodynamics of artificial heart valves is presented. It is a method of flow visualisation. The photochromic flow visualization method is based on activation of color tracers in originally colorless photochromic solutions by pulse laser radiation during 10-6 − 10-9 seconds. The tracer appears as a straight colored line, which subsequently is deformed by the flow. The methods known so far for the flow visualization give an insight on the general flow but do not provide quantitative data. The method mainly used, the LDA, permits measurements only in one point. The new method combines the precision of the LDA with the clarity of flow visualization.
Biomaterials in Medicine - A Bioengineering Perspective
Authors: Courtney J.M. , Irvine L. , Jones C. , Mosa S.M. , Robertson L.M. , Srivastava S.
Published: March 2018

Biomaterials are considered with an emphasis on those used in artificial organs. Attention is drawn to the importance of the polymeric biomaterials and factors which affect their properties. Functions of membranes, sorbents, blood tubing, ventricular diaphragms and cell culture substrates are examined in order to obtain a summary of fundamental properties. Observations are made on the importance of blood compatibility assessment and its association with a biomaterial structure-property relationship. Blood-biomaterial interactions are discussed in terms of an overall relationship between the three components –- blood, biomaterial and antithrombotic agent, with examples given of factors influencing each component. Cell-biomaterial interactions are examined in the areas of toxicity evaluation and the promotion of cell attachment and growth, where an overall relationship is described for the cell, growth medium and growth factors, and the biomaterial acting as a substrate.
Assessment of Acute Parathyroid Responsiveness to High Calcium Dialysate in Uremic Patients
Authors: Melan A. , Schiffl H. , Held E. , Horn K.
Published: March 2018

The response of the parathyroid glands to dialysis-induced changes in calcium has been studied in 83 normocalcemic patients receiving maintenance hemodialysis. Predialysis concentrations of intact parathyroid hormone (iPTH) were normal in 13 patients; 70 patients had increased iPTH levels of different degrees. All patients had analytically significant changes in total serum calcium (2.3 ± 0.2 vs 2.8 ± 0.2 mmol/l) without additional parenteral calcium loading during a standard dialysis session with a dialysis solution of 1.75 mmol calcium chloride. During hemodialysis the concentration of iPTH fell in 77 patients and was normalized in 48 of these patients. The remaining 6 patients showed no or an inadequate response (less than 30% suppression of predialysis iPTH) to the increase in Ca. Parathyroidectomy was performed in patients with refractory iPTH secretion. Histological evidence of marked parathyroid hyperplasia was obtained in all these patients. All patients with normal or partial responsiveness of the parathyroids tolerated at least small doses of 1.25 (OH)2-vitamin D3. Quantification of predialysis and postdialysis iPTH concentrations is a useful and simple method for identifying those uremic patients with true autonomy of the parathyroid glands at an early stage.
Infections Associated with Prosthetic Devices: Clinical Considerations
Authors: Dickinson G.M. , Bisno A.L.
Published: March 2018

The successful development of synthetic materials and introduction of artificial devices into nearly all body systems has been shadowed by the adaptation of microorganisms to the opportunities these devices afford for eluding defenses and invading the host. Clinicians are faced with the task of recognizing the manifestations of device-associated infection, predicting the likely pathogens involved, knowing the appropriate diagnostic methods, and initiating appropriate therapy. Infections associated with prosthetic heart valves are particularly challenging to successfully treat; surgical replacement may be necessary. Infection associated with an artificial joint usually requires removal of the device in addition to appropriate antibiotics. Intravascular associated infections are the leading cause of nosocomial bacteremias and, because of their intravascular location, these infections are often life catheter threatening if not promptly diagnosed and treated. Even contact lenses, external to epithelial surfaces, may give rise to serious sight-threatening infections. Although artificial devices play a paramount role in medicine today, infection is an ever present potential with which clinicians must be familiar.
Infections Associated with Implanted Blood Pumps
Authors: Burns G.L.
Published: March 2018

A variety of prosthetic blood pumps are currently undergoing experimental development or are available for clinical use. The Jarvik-7® and Jarvik 7-70® (Symbion-7® and Symbion 7-70®) total artificial hearts (TAH) have been used worldwide both experimentally and for clinical mechanical circulatory support. Of the 190 patients implanted with these devices, 133 went on to cardiac transplantation and 68 of the transplanted patients are alive. Complications associated with the use of the TAH have included postoperative hemorrhage, thrombosis with thromboembolism and infection. The incidence of infection in the patients implanted with the TAH has declined significantly since initial clinical use and is now near 30%. Staphylococcus epidermidis and Pseudomonas aeruginosa are the most commonly pathogens isolated from these devices.
A Mouse Model of Implant-Associated Infection
Authors: Gagnon R.F. , Richards G.K.
Published: March 2018

Infections of implanted devices are of increasing frequency and importance, representing a significant limitation of many therapeutic modalities. There are puzzling features of implant-associated infection including the changes in microbial flora, the tendency to chronicity and impaired responses to conservative modes of treatment. The concept of the bacterial biofilm as a shielding mechanism generated by bacteria adherent to artificial surfaces has recently been proposed as an explanation for these features. The biofilm is a term applied to a complex comprising the implant surface, adherent bacteria and a specialized matrix enclosing the bacteria. The matrix of the biofilm is an electrostatically charged glue-like extracellular polymer derived by bacterial enzymes acting on tissue carbohydrates, formed by bacteria when adherent to surfaces. This matrix binds the bacteria to the surface providing a sequestration affording selective protection against harmful elements of the environment, especially mechanisms of host defenses and antimicrobial agents. These biological systems are complex to study because of the dynamic interaction of the microbial variables, host defenses, properties of synthetic materials and the biofilm matrix itself. There is a need for a laboratory model in which the variables can be controlled permitting the researcher to examine the outcomes of modifying one variable at a time in a planned and orderly manner. The practical way to attain this end is the conduct of studies in a stable reproducible animal model of localized biofilm-implant infection. Staphylococcus epidermidis is a representative of the class of microorganisms predominant in implant-associated infection. This paper describes the development of a model utilizing an implant-S. epidermidis-biofilm infection localized to the peritoneal cavity of the mouse. The natural history of the infection has been well documented and is stable in all respects for periods exceeding 3 months. This chronicity is especially advantageous in analyzing the impact of long-term therapeutic modalities and necessary periods of recovery and assessment. A representative example of an experimental use of this model to determine the relative efficacy of antibiotic therapeutic regimes is described, demonstrating its scope and efficacy.
Efficacy and tolerability of recombinant human erythropoietin treatment in pre-dialysis patients: Results of a multicenter study
Authors: Albebtazzi A. , Liberato L. Dl , Daniele F. , Battistel V. , Colombi L.
Published: March 2018

Chronic renal failure is characterized by a normochromic normocytic anemia, the severity of which generally increases during progression toward uremia. The purpose of the study was to evaluate the efficacy and safety of recombinant human erythropoietin (rHu-EPO) given subcutaneously (s.c.), the dose required to reach and maintain Hb levels within 10 and 11g% and its effects, if any, on the progression of chronic renal failure. Eighty-four pre-dialysis patients (46 F, 38M, age 61.7+13.9 years) with Hb levels between 6 and 9g% and serum creatinine ranging from 3 to 9 mg/dl were treated with s.c. rHu-EPO (2000 U/twice weekly). After 6 weeks, if Hb increase was below 1g%, 1000 U of s.c. rHu-EPO were added at each administration (3000 U twice weekly). Once the Hb target was reached (10–11g%), the rHu-EPO weekly dose was halved and administration reduced to once weekly. The patients showed a significant rise in mean Hb values (p<0.001) after 3 months. Mean Hb values were as follows: 8.00±0.77g% (pretreatment), 9.35±1.0 (3rd month), 10.06±1.04 (6th month), 10.25±0.62g% (12th month). The mean rHu-EPO doses were 4000 U/w (start of the study), 3592+1685 U/w (6th month), 2840±1178 U/w (12th month).

Renal function was evaluated by plotting the reciprocal of serum creatinine values vs time with a two period comparison: period A (retrospective-8 mo); period B (prospective-12 mo). The residual renal function was not impaired by rHu-EPO therapy. Meanwhile, no relevant modifications were observed in mean blood pressure values.

Low doses of s.c. rHu-EPO were well tolerated, safe and effective; this therapeutic approach should therefore be considered for the improvement of anemia in pre-dialysis patients. A slow and gradual correction of anemia induces an improved sense of well being and a more active of life style. (Int J Artif Organs 1998; 21:12-8)
Test procedure for artificial mitral valves
Authors: Schichl K. , Affeld K. , Dreysse S.
Published: March 2018

The flow curve of a valve-tester has a great influence on the performance of a valve. Usually the flow curve of the aorta is used. However, the mitral valve flow curve differs greatly from the flow curve of the aortic valve. It varies with the pulse rate and is further changed in patients with certain heart diseases. To investigate the different mitral flow conditions, ultrasonic flow curves from patients with a mechanical artificial mitral valve were analyzed. The curves show that a mitral valve prosthesis has not only to work under physiological flow conditions, but also in pathologically deviant flows. According to these results three different characteristic flow curves were selected and used to test several valves with a computer controlled valve-tester. The mean diastolic pressure difference and the whole closing behavior were influenced by the flow curve; and the differences in energy losses were particularly great. This indicates, that the flow curve must be adjusted appropriately. (Int J Artif Organs 1998; 21:37–42)
Positive biochemical effects of a bioartificial liver support system (BALSS) in a porcine fulminant hepatic failure (FHF) model
Authors: Sheil A.G.R. , Sun J. , Mears DC. , Waring M. , Woodman K. , Johnston B. , Horvat M. , Watson J. , Koutalistras N. , Wang L.
Published: March 2018

This study describes biochemical changes in the plasma and blood of pigs with devascularised livers treated in a bioartificial liver support system (BALSS). Porcine hepatic cells were incubated with collagen-coated dextran microspheres (COM) for 3 hours and the medium tested to determine cellular metabolic activity. Incubation continued for a further 18 hours during which the hepatic cells attach to the COM. The CDM-attached cells were inoculated into a hollow fibre bioreactor which was part of an extracorporeal support system. Hepatic cell content of the bioreactor was 6x109 cells. The system was tested in a controlled trial in pigs prepared in a surgical model of fulminant hepatic failure (FHF). When plasma from FHF pigs was circulated through the device containing hepatic cells, there was significantly less increase in the accumulation of ammonia and most amino acids, together with a decrese in plasma lactate and of one amino acid, compared to control experiments when hepatic cells were excluded. We conclude that primary porcine hepatocytes can contribute beneficial metabolic function in a BALSS. (Int J Artif Organs 1998; 21:43–8)