bluuebunny/crossref_metadata_2025 huggingface dataset:
What Should We Expect From a Bioartificial Liver In Fulminant Hepatic Failure?
Authors: Bismuth Henri , Figueiro Jose , Samuel Didier
Published: March 2003

Fulminant hepatic failure is associated with high mortality. Liver transplantation is an effective therapy that improves survival, and because of donor organ shortage and urgency, a bioartificial liver could act as an effective bridge to liver transplantation in patients with fulminant hepatic failure. We discuss the place of the bioartificial liver in the treatment of other causes of liver failure.
Lixelle Adsorbent to Remove Inflammatory Cytokines
Authors: Tsuchida Kenji , Takemoto Yoshiaki , Nakamura Takahiro , Fu Ontaku , Okada Chikako , Yamagami Seiji , Kishimoto Taketoshi
Published: March 2003

It is the goal of this section to publish material that provides information regarding specific issues, aspects of artificial organ application, approach, philosophy, suggestions, and/or thoughts for the future.

A β2‐microglobulin (β2M) selective adsorbent (Lixelle) for direct hemoperfusion has been used for the treatment of hemodialysis patients with the long‐term complication of dialysis related amyloidosis (DRA), but there is no significant correlation between the serum level of β2M and the occurrence of DRA. Inflammatory cytokines such as interleukin (IL)‐1, IL‐6, and tumor necrosis factor alpha (TNFα) are related to the development of DRA. We studied the adsorptive rates of cytokines in vitro using the Lixelle adsorbent. The adsorptive rates were 98. 5% for IL‐1β, 98.0% for interleukin‐1 receptor antagonist (IL‐1RA), 82.9% for IL‐6, 99.9% for IL‐8, 31.2% for TNF α, and 46.1% for soluble TNF receptor (sTNFr), respectively. As the molecular weights of cytokines increase, the adsorptive rates decrease. The Lixelle column adsorbed β2M and various inflammatory cytokines as well. Therefore, the removal of both β2M and inflammatory cytokines may play an important role in the treatment of DRA.
Membrane Immunoisolation of a Diffusion Chamber for a Bioartificial Pancreas
Authors: Ohgawara Hisako , Hirotani Sachiko , Miyazaki Jun‐ichi , Teraoka Satoshi
Published: March 2003

Immunoisolation is a potentially important approach to transplanting islets without any immunosuppressive therapy. The concept of immunoisolation is outlined in systems in which the transplanted tissue is separated from the immune system of the host by an artificial barrier. We previously described a diffusion chamber as a bioartificial endocrine pancreas (Bio‐AEP), which was constructed by placing pancreatic endocrine cells, trapped in a mixed matrix, in the center of a ring holder sandwiched between nucleopore membranes, which were shielded by silicone. This experiment was designed to evaluate a suitable pore size for the nucleopore membrane to ensure immunoisolation during xenoimplantation of the Bio‐AEP in vitro and in vivo. A nucleopore membrane of pore size 0.1 μm or 0.2 μ m was employed as the semipermeable membrane which provided a mechanical barrier between the endocrine pancreas graft and the host immune system. The protective effect of the Bio‐AEP from humoral immunity was determined in vitro, using sensitized sheep erythrocytes (EAs). A complement protein did not destroy the cell membranes of the EAs in the diffusion chamber containing the mixed matrix with the nucleopore membrane of 0.1 μm pore size. In an in vivo experiment, 6 streptozotocin (STZ) induced diabetic rats were implanted with Bio‐AEPs constructed with nucleopore membranes of pore size 0. 1 μm and containing MIN6 cells in the mixed matrix. In the STZ diabetic rats with Bio‐AEPs, a return to normoglycemia was observed up to 50 weeks after implantation without the use of any immunosuppressant. Also, the body weights of the rats gradually increased. During the observation, when the Bio‐AEPs were removed from the STZ diabetic rats, the blood glucose immediately returned to preimplantation levels, and the body weights of the rats also decreased. The membranes of the Bio‐AEPs removed from the STZ diabetic rats showed a very thin layer of fibroblastic cells on the outer surfaces. The results indicated that the Bio‐AEP, in which pancreatic endocrine cells were trapped in a mixed matrix and with a 0.1 μm pore size membrane, should be useful for xenoimplantation into diabetic animals and may open a new field in the therapy of human diabetics.
Inhibition of Gastric Secretion by Omeprazole and Efficiency of Calcium Carbonate on the Control of Hyperphosphatemia in Patients on Chronic Hemodialysis
Authors: Hardy P. , Sechet A. , Hottelart C. , Oprisiu R. , Abighanem O. , Said S. , Rasombololona M. , Brazier M. , Moriniere P. , Achard J.‐M. , Pruna A. , Fournier A.
Published: March 2003

Abstract: Contradictions exist in the literature regarding the effect of gastric secretion inhibition on phosphate absorption. In healthy controls, omeprazole would decrease the hyperphosphatemia or the hyperphosphaturia induced by an acute phosphate load, suggesting an inhibition of phosphate absorption. In chronic hemodialysis patients, gastric hypersecretion is associated with hyperphosphatemia, but inhibition of gastric hypersecretion by ranitidine in those receiving calcium carbonate (CaCO3) as a phosphate binder would paradoxically exacerbate their hyperphosphatemia. Because of these conflicting observations, we performed an open crossover study on 16 chronic stable hemodialyzed patients with a daily mean intake of 9.4 ± 4 g of CaCO3, and we compared the plasmatic predialysis levels of phosphate, calcium, protides, bicarbonates, intact parathyroid hormone (PTH), urea, and creatininemia during 2 successive periods of 2 months, the first one without omeprazole and the second one with 20 mg omeprazole intake in the morning. Phosphatemia increased with omeprazole but not significantly from 1. 80 ± 0.38 to 1.89 ± 0.42 mM whereas corrected calcemia decreased significantly (p = 0.04) from 2.41 ± 0.18 to 2.36 ± 0.16 mM as did bicarbonatemia from 26.7 ± 3.5 to 25.7 ± 3.1 mM (p < 0.05). No change in creatininemia or in blood urea was observed, suggesting the stable efficiency of dialysis as well as the stable intakes of protein and therefore of phosphate during the two study periods. In conclusion, inhibition of gastric secretion by omeprazole increases the plasmatic phosphate predialytic level but in a nonsignificant way. This increase may be explained by a slight but significant concomitant decrease of calcemia and bicarbonatemia. These results do not support the phosphate binding efficiency of CaCO3 being decreased by the inhibition of gastric acid secretion.
Functionalized Hollow Fiber Membrane Cartridge for Adsorption of Anticofactor/Antiphospholipid Antibodies: A Potential Tool for Treatment
Authors: Darnige L. , Legallais C. , Arvieux J. , Pitiot O. , Vijayalakshmi M.A.
Published: March 2003

Abstract: It is of considerable interest to ascertain whether a hollow fiber cartridge containing histidine immobilized on polyethylenevinyl alcohol membrane (His‐PEVA) is able to retain specific autoantibodies involved in antiphospholipid syndrome. To this end diluted patient pathogenic plasma containing high levels of anti‐β2‐glycoprotein I (anti‐β2GPI) and antiprothrombin antibodies was processed through the functionalized cartridge. The adsorbed material was then eluted under mild conditions and analyzed; an enrichment of the eluted fractions in total IgG and more specifically in IgG2 subclass was observed, compared with the injected sample. Enzyme‐linked immunosorbent assay tests showed a higher specific binding of antiprothrombin and anti‐β2GPI in these fractions. This was in accordance with the concomitant higher anticoagulant activity measured on the same fractions. All in vitro results clearly demonstrated the ability of the His‐PEVA cartridge to preferentially adsorb these autoantibodies. Hence the functionalized cartridge represents a potential tool for the treatment of antiphospholipid syndrome by selective extracorporeal removal of IgG.
A Simplified Single Pump Circuit for Cardiac Bypass with Autogenous Oxygenation
Authors: Marques Euclydes , Cestari Ismar N. , Cestari Idágene A. , Leirner Adolfo A.
Published: March 2003

A simplified extracorporeal circulation (ECC) assemblage with autogenous oxygenation (AO) using a single centrifugal pump was tested in dogs. The transpulmonary gradient was obtained by increasing pressure in the right atrium through volume expansion and decreasing it in the left atrium by collecting the blood from the pulmonary veins in a reservoir placed below the level of the animal, generating a siphon effect. This arrangement dispenses with a right side pump. The heart was electrically fibrillated after perfusion was started and defibrillated at the end of the bypass. This ECC circuit allowed the maintenance of adequate hemodynamic and blood gas parameters during the bypass. The operating field and the mobility of the heart were equivalent to that of conventional cardiopulmonary bypass (CPB). We conclude that the use of a single centrifugal pump simplifies the autogenous oxygenation approach, making it a practical choice for the coronary artery bypass graft (CABG) procedure.
Clinical Audit of 5 Years Provision of the Odstock Dropped Foot Stimulator
Authors: Taylor Paul , Burridge Jane , Dunkerley Anna , Wood Duncan , Norton Jonathan , Singleton Christine , Swain Ian
Published: March 2003

The Odstock dropped foot stimulator (ODFS) is a foot switch controlled single channel neuromuscular stimulator for correction of dropped foot. Following a randomized controlled trial, the ODFS was recommended for use in the United Kingdom's National Health Service and a clinical service established. The patient performance was assessed by measurement of walking speed over 10 m, physiological cost index (PCI), and by questionnaire. After 4.5 months stroke patients (n = 111) showed a mean increase in walking speed of 27% and reduction in PCI of 31% with stimulation and changes of 14% and 19%, respectively, unassisted. Multiple sclerosis patients (n = 21) gained similar orthotic benefit but no carry over. The principal reason cited for using the equipment was that it reduced the effort of walking. The principal reasons identified for discontinuing were an improvement in mobility, electrode positioning difficulties, and deteriorating mobility. A comprehensive clinical follow‐up service is essential to achieve the maximum continuing benefit from FES based orthosis.
Measurement of Blood Hematocrit Inside the Magnetically Suspended Centrifugal Pump Using an Optical Technique: Application to Assessment of Pump Flow
Authors: Kaiwa Takeshi , Mori Taketoshi , Kijima Toshihiko , Nogawa Masamichi , Nojiri Chisato , Takatani Setsuo
Published: March 2003

To measure blood hematocrit inside the magnetically suspended centrifugal pump, we have performed both forward and backward light scattering measurements using a specially designed optical cell. In the forward scattering measurement, an optical fiber was used to guide the near infrared light at 780 nm into a 250 μm gap region, and the light that forward scattered toward a detector fiber was measured using a phototransistor. The light intensity decreased exponentially with an increase in the hematocrit to around 20%. The forward scattering method suffered from sensitivity at the hematocrit levels around 25–45% due to the diffusion effect. By making the optical path length larger than several millimeters, the sensitivity of the forward scattering method in terms of hematocrit change can be improved. In the back scattering method, however, better sensitivity in terms of hematocrit change from 0–50% was obtained. By making the optical fiber separation distance less than 1 mm, the system will measure the first order back scattering from the shallow layer while, by making the fiber separation distance larger than several millimeters, the system will primarily measure the diffuse reflectance from the deeper layer. Both approaches will yield sensitive optical intensity change in terms of the physiological hematocrit range.
Peripheral Vascular Resistances During Total Left Heart Bypass with an Oscillated Blood Flow
Authors: Yambe Tomoyuki , Kawano Satoyoshi , Nanka Shun‐suke , Kobayashi Shin‐ichi , Tanaka Akira , Owada Naoki , Yoshizawa Makoto , Abe Ken‐ichi , Tabayashi Kouichi , Takeda Hiroshi , Hashimoto Hiroyuki , Nitta Shin‐ichi
Published: March 2003

For development aimed at a totally implantable type ventricular assist device (VAD), the vibrating flow pump (VFP) has been developed at Tohoku University. A transcutaneous energy transmission system (TETS) using amorphous fibers was developed to power the totally implantable VAD system. The VFP works at a high frequency compared to that of a natural heart of a biological system. It is a frequency of 10–50 Hz. In this research, animal experiments with left heart bypass were carried out with healthy adult goats. For comparison between nonpulsatile flow and oscillated flow, a rotary pump (RP) and the VFP were used in the experiments. For the achievement of total left heart bypass, left ventricular approaches were carried out, and blood was pumped from the left ventricle to the descending aorta. Adequate support of the left heart was provided by both pumps. In terms of the results, the vascular resistances tended to decrease during the use of both pumps during 100% bypass driving. When we compared these pumps at the same flow rate, the resistances during RP driving were significantly smaller than those during VFP driving. These results may suggest that the influences of the VFP upon the peripheral vessels may be relatively small compared to those of the RP. This may be an important result when a stable hemodynamic condition is required during artificial circulation. The VFP was considered as a candidate for a totally implantable VAD as a result.
Computational Fluid Dynamics Analysis to Establish the Design Process of a Centrifugal Blood Pump: Second Report
Authors: Miyazoe Yuki , Sawairi Toshio , Ito Kazuyuki , Konishi Yoshiaki , Yamane Takashi , Nishida Masahiro , Asztalos Balazs , Masuzawa Toru , Tsukiya Tomonori , Endo Seiko , Taenaka Yoshiyuki
Published: March 2003

To establish an efficient design process for centrifugal blood pumps, the results of computational fluid dynamics (CFD) analysis were compared to the results of flow visualization tests and hemolysis tests, using the Nikkiso centrifugal blood pump. CFD analysis revealed that the radial gap greatly affected the shear stress in the outlet diffuser. The hemolysis study also indicated a similar tendency. To see the flow behind the impeller, we conducted a comparative study between models with and without washout holes using the CFD technique. CFD analysis indicated that flow and pressure distributions behind the impeller were different between both models, and a particle was observed to remain longer behind the impeller in the model without washout holes. In the future, CFD analysis could be a useful tool for developing blood pumps in comparison to flow visualization tests and hemolysis tests.
Characterization of a Magnetic Bearing System and Fluid Properties for a Continuous Flow Ventricular Assist Device
Authors: Baloh Michael J. , Allaire Paul E. , Hilton Edgar F. , Wei Naihong , Olsen Don B. , Bearnson Gill B. , Khanwilkar Pratap S.
Published: March 2003

This article presents the performance test results of the CFVAD3 continuous flow blood pump in an artificial human circulation system. The CFVAD3 utilizes magnetic bearings that support a thin pancake impeller, the shape of which allows for a very compact pump whose total axial length is less than 5 cm with a radial length of about 10 cm. This gives a total volume of about 275 cc. The impeller itself has 4 vanes with a designed operating point of 6 L/min at 100 mm Hg of differential pressure and 2,000 rpm. The advantages of magnetic bearings, such as large clearance spaces and no mechanical wear, are elaborated upon. Furthermore, bearing model parameters such as load capacity and current gains are described. These parameters in conjunction with the operating conditions during testing are then used to estimate the fluid forces, stiffness, and damping properties while pumping. Knowledge of these parameters is desirable because of their effects on pump behavior. In addition, a better plant model will allow more robust control algorithms to be devised that can boost pump performance and reliability.
Rotary Blood Pump Flow Spontaneously Increases During Exercise Under Constant Pump Speed: Results of a Chronic Study
Authors: Akimoto Takehide , Yamazaki Kenji , Litwak Philip , Litwak Kenneth N. , Tagusari Osamu , Mori Toshio , Antaki James F. , Kameneva Marina V. , Watach Mary J. , Umezu Mitsuo , Tomioka Jun , Kormos Robert L. , Koyanagi Hitoshi , Griffith Bartley P.
Published: March 2003

Many types of rotary blood pumps and pump control methods have recently been developed with the goal of clinical use. From experiments, we know that pump flow spontaneously increases during exercise without changing pump control parameters. The purpose of this study was to determine the hemodynamics associated with the long‐term observation of calves implanted with centrifugal blood pumps (EVAHEART, Sun Medical Technology Research Corporation, Nagano, Japan). Two healthy female Jersey calves were implanted with devices in the left thoracic cavity. A total of 22 treadmill exercise tests were performed after the 50th postoperative day. During exercise, the following parameters were compared with conditions at rest: heart rate, blood pressure, central venous oxygen saturation (SvO2), pump speed, and pump flow. The pump flow in a cardiac cycle was analyzed by separating the systole and diastole. Compared to the base data, statistically significant differences were found in the following interrelated parameters: the heart rate (66.8 ± 5.2 vs. 106 ± 9.7 bpm), mean pump flow (4.8 ± 0.2 vs. 7.0 ± 0.3 L/min), and volume of pump flow in diastole (26.0 ± 1.8 vs. 13.5 ± 2.5 ml). During exercise, the volume of pump flow in systole was 3 times larger than that measured in diastole. Blood pressure, SvO2, and pump speed did not change significantly from rest to exercise. These results suggested that the mean pump flow depends on the systolic pump flow. Therefore, the increase in the mean pump flow during exercise under constant pump speed was caused by an increase in the heart rate.
Proposed Entry Criteria for Postoperative Cardiac Extracorporeal Membrane Oxygenation After Pediatric Open Heart Surgery
Authors: Trittenwein Gerhard , Pansi Heike , Graf Bernadette , Golej Johann , Burda Gudrun , Hermon Michael , Marx Manfred , Wollenek Gregor , Trittenwein Hildegard , Pollak Arnold
Published: March 2003

Abstract: While extracorporeal membrane oxygenation (ECMO) is being used increasingly after pediatric cardiac surgery, criteria are lacking for initiating ECMO after bypass weaning. To develop clinically useful ECMO entry criteria based on parameters readily available, children were examined at postoperative pediatric intensive care unit (PICU) admission. Using hospital mortality as the primary outcome, univariate and multiple logistic regressions were performed to estimate the predictive value of clinical (age, weight, and diagnosis) and laboratory (arterial blood pressure, pH, lactate, creatine kinase, and arterial and central venous oxygen saturation [ScvO2]) variables. Data from 218 children over a 2 year period were analyzed retrospectively. Univariate regression demonstrated that age, weight, diagnosis, blood pressure, venous and arterial saturation, and lactate were significantly associated with postoperative mortality (p < 0.05). In multiple regression, ScvO2 and lactate level were found to be independent predictors and were used in a predictive model (ScvO2 odds ratio: 2.03–828.6, p = 0.016) (lactate odds ratio: 1.58 –4.20, p = 0.0002) (R2 = 0.70). Applying an 80% risk of mortality to establish entry criteria as in neonatal ECMO, PICU admission values of lactate > 70mg/dl if ScvO2 < 60% or lactate >163mg/dl if ScvO2 > 60% are proposed to serve as postoperative ECMO entry criteria if bypass weaning has been possible but is followed by low cardiac output.
Computational Flow Study of the Continuous Flow Ventricular Assist Device, Prototype Number 3 Blood Pump
Authors: Anderson Jay B. , Wood Houston G. , Allaire Paul E. , Bearnson G. , Khanwilkar P.
Published: March 2003

Abstract: A computational fluid dynamics study of blood flow in the continuous flow ventricular assist device, Prototype No. 3 (CFVAD3), which consists of a 4 blade shrouded impeller fully supported in magnetic bearings, was performed. This study focused on the regions within the pump where return flow occurs to the pump inlet, and where potentially damaging shear stresses and flow stagnation might occur: the impeller blade passages and the narrow gap clearance regions between the impeller‐rotor and pump housing. Two separate geometry models define the spacing between the pump housing and the impeller's hub and shroud, and a third geometry model defines the pump's impeller and curved blades. The flow fields in these regions were calculated for various operating conditions of the pump. Pump performance curves were calculated, which compare well with experimentally obtained data. For all pump operating conditions, the flow rates within the gap regions were predicted to be toward the inlet of the pump, thus recirculating a portion of the impeller flow. Two smaller gap clearance regions were numerically examined to reduce the recirculation and to improve pump efficiency. The computational and geometry models will be used in future studies of a smaller pump to determine increased pump efficiency and the risk of hemolysis due to shear stress, and to insure the washing of blood through the clearance regions to prevent thrombosis.
Design of a Fluidized Bed Bioartificial Liver
Authors: Legallais Cécile , Doré Emmanuel , Paullier Patrick
Published: March 2003

Abstract: The aim of this study was to design a bioreactor for extracorporeal liver supply containing alginate beads in a fluidized bed regimen. The objective was to achieve a satisfactory mixing into the bioreactor to promote the potential exchanges and mass transfers. First, we checked whether both present phases (solid: alginate beads; liquid: saline solution at 20°C) might allow for this fluidization. Then the optimal design was defined as a function of the required operating conditions, bead volume, and perfusion flow rate; the bioreactor cross section and height especially needed to be adjusted. The efficient fluidization, under optimized conditions, was proven through the follow‐up of the head losses generated by the fluidized bed. Criteria for scaling up were also determined.
Specific Determination of Endothelial Cell Viability in the Whole Cell Fraction from Cryopreserved Canine Femoral Veins Using Flow Cytometry
Authors: Park Jong‐Chul , Sung Hak‐Joon , Lee Dong Hee , Park Young Hwan , Cho Bum Koo , Suh Hwal
Published: March 2003

Abstract: An efficient method for specifically determining the viability of endothelial cells (EC) from cells dissociated from the human saphenous vein was investigated. Three different methods, trypan blue staining assay, [3H]‐proline incorporation assay, and flow cytometry (FCM), combined with the fluorescein isothiocyanate conjugated with Griffonia simplicifolia agglutins (GS1‐FITC)/propidium iodide (PI) double staining, were used. Both trypan blue staining and [3H] proline incorporation assays demonstrated less sensitivity to determine viability of EC differentially from the other cells. FITC‐GS1 showed prominent binding to the vascular EC and could be counted by FCM including PI on dead cells. Following the cryopreservation process, the GS1‐FITC/PI FCM analytical method was adopted to test simultaneously the viability of whole cells and EC from the same tissue, human saphenous veins, and mongrel dogs' femoral veins after harvesting, antibiotic solution treatment, and thawing. The viability of the whole cells from veins decreased with a significant difference (p < 0.05) from that of EC after thawing.
Plasmapheresis‐Related Hypotension
Authors: Yeh Jiann‐Horng , Chiu Hou‐Chang
Published: March 2003

Abstract: Hypotension is an uncommon complication of procedures involving extracorporeal circulation, including plasmapheresis. From November 1993 to March 1999, we treated 139 patients who underwent a total of 1,137 sessions of double filtration plasmapheresis (DFP). Hypotension was defined as a systolic blood pressure (BP) < 80 mm Hg or any decrease of systolic BP with systemic reactions. A total of 17 (1.5%) episodes of hypotension were documented in 15 patients during the study period. Hypotensive episodes occurred in 2.3% of patients with inflammatory neuropathy, 1.2% of patients with myasthenia gravis, and 1.2% of patients with all other medical diseases. Involvement of the autonomic nerve system (ANS) and a low baseline BP were associated with the occurrence of hypotension. Eight (47%) of 17 episodes were symptomatic and 2 were complicated with seizure. Patients with symptomatic hypotension had a higher level of systolic BP prior to DFP and a larger drop of systolic BP and pulse rate during hypotensive attacks compared to asymptomatic patients. Most hypotensive episodes were resolved briefly after intravenous infusion of saline within 30 min. Eight (47%) of the hypotensive episodes occurred during the first session of DFP treatment. Twelve (71%) of 17 episodes occurred during the last half period of treatment; 6 of them were noted during the terminating stage of DFP. In conclusion, in this series plasmapheresis‐related hypotension occurred in 1.5% of DFP sessions and had a higher prevalence in patients with ANS instability and low BP. Extra caution in monitoring BP during DFP therapy is warranted in these vulnerable patients, especially during the termination phase of the first DFP session.
Use of Tactile Stiffness to Detect Fatigue in the Latissimus Dorsi Muscle
Authors: Inaba Hirotaka , Miyaji Kagami , Kaneko Yukihiro , Ohtsuka Toshiya , Ezure Masahiko , Tambara Keiichi , Takamoto Shinichi , Omata Sadao
Published: March 2003

Abstract: In clinical settings, no method has been established to examine the fatigue of a latissimus dorsi muscle (LDM) preconditioned for cardiomyoplasty. We examined the feasibility of measuring muscle stiffness (tactile stiffness) to evaluate muscle fatigue in situ using our tactile sensor. We stimulated canine LDM with burst pacing and monitored both stiffness and tension to determine their relationship. In both dissected LDM and LDM in situ, the decrements of these parameters during burst pacing were compared between preconditioned and unconditioned LDM. In measurement in situ, the sensor probe was placed on the LDM through a small incision. Strong statistical correlation was shown between stiffness and tension (r = 0.935). In decrements of stiffness in situ, there were statistically significant differences between preconditioned and unconditioned LDM. Our tactile sensor system can provide an efficient method for evaluating fatigue of muscles in situ without measuring muscle tension.
Implantation of One Piece Biventricular Assist Device by Left Thoracotomy in an Ovine Model
Authors: Kim Won Gon , Jo Yong Ho , Min Byoung Goo , Won Tae Hee
Published: March 2003

Abstract: In this report, we describe an operative procedure for our implantable 1 piece biventricular assist device (BiVAD) based on a moving actuator mechanism, using an ovine model. Our implantable BiVAD is a volumetric coupled 1 piece unit including right and left blood sacs and an actuator assembly based on the moving actuator mechanism. The BiVAD was controlled by fixed rate control with 75 bpm for the most part. Both the left and the right full ejection modes with the maximum stroke angle were selected to minimize blood stasis in the blood sacs because of low assist flow condition. Three Corriedale sheep were used for the device implantation by a left thoracotomy incision. Cannulation was successfully performed in all cases. Although exposability of the right atrial appendage varied from animal to animal, the insertion of the cannula was easily performed. The cannulas were connected to the pump‐actuator assembly in the preperitoneal pocket. All 3 animals survived the experimental procedure. During implantation of the device, in the 1 month survival animal, pump flow was maintained between 2.0 L/min and 2.5 L/min, mean aortic pressure was 90–110 mm Hg, and mean pulmonary artery pressure was 20–30 mm Hg. The left and right atrial pressure were maintained between 0 and 5 mm Hg. In conclusion, this ovine model for implantation of the 1 piece BiVAD can be an effective alternative for testing in vivo biocompatibility of the device although it needs more consideration for anatomical fittability for future human application.
Cerebral Tissue Oxygen Saturation During Percutaneous Cardiopulmonary Support in a Canine Model of Respiratory Failure
Authors: Wada Hideichi , Watari Masanobu , Sueda Taijiro , Kochi Kazuhiro , Sakai Hiroshi , Shibamura Hidenori , Imai Katsuhiko , Fukunaga Shintaro , Orihashi Kazumasa , Matsuura Yuichiro
Published: March 2003

Abstract: Percutaneous cardiopulmonary support (PCPS) has come to be applied for cardiopulmonary resuscitation and in the management of severe respiratory failure as well as severe heart failure. We investigated cerebral tissue oxygen saturation during PCPS in a canine model of respiratory failure using near‐infrared spectroscopy. Animals were mechanically ventilated with 10% oxygen to make a respiratory failure model. Perfusion with PCPS was performed via the left femoral artery and switched to that via the right axillary artery. Cerebral tissue oxygen saturation was 54.2 ± 3.4% during PCPS via the femoral artery and was 82.3 ± 4.6% during PCPS via the axillary artery (p = 0.001). Hepatic tissue oxygen saturation was not significantly different. LV dP/dt max increased significantly after switching to the axillary blood supply (p = 0.001). Conventional PCPS may not have the capability of supporting cerebral circulation under severe respiratory failure without organic heart disease.
Computational Fluid Dynamics Analysis of Hydrodynamic Bearings of the VentrAssist Rotary Blood Pump
Authors: Qian Yi , Bertram Christopher D.
Published: March 2003

Abstract: The computational fluid dynamics (CFD) package CFX‐TASCflow was applied to simulate the flows through the blood pump hydrodynamic bearings. The three‐dimensional flow patterns through the bearings were predicted and the hydraulic performance analyzed. The computations were carried out at 3 axial positions of the pump impeller. Net lift force away from the nearer part of the housing increased when the impeller moved closer to this part. Radial force and drag force were also found. Separated flows were observed at the leading and trailing edge of the bearing gap. To test the CFD package, a series of two‐dimensional computations were also carried out for various bearing geometries. The results were compared with published experimental data.
Vero Cell Growth and Differentiation on Poly(l‐Lactic Acid) Membranes of Different Pore Diameters
Authors: Santos Arnaldo R. , Barbanti Samuel H. , Duek Eliana Aparecida R. , Dolder Heidi , Wada Ronaldo S. , Wada Maria Lucia F.
Published: March 2003

Abstract: In the last few years, the demand has increased for research on polymeric materials, which can be used as substitutes for injured tissues and organs or to improve their regeneration. In this work, we studied poly(l‐lactic acid) (PLLA) membranes, a resorbable biomaterial, which were either dense or had different pore diameters (less than 45 μm, between 180 and 250 μm, and between 250 and 350 μm), in relation to stimulation of cell adhesion, growth, and differentiation in vitro. We used Vero cells, a fibroblastic cell line, as the biological model of investigation. We found that cells attached slowly to all PLLA membranes studied. On the other hand, once the adhesion occurs, the cells are able to grow and differentiate on the different polymers. The cells grew to form a confluent monolayer and were capable of producing collagen Type IV and fibronectin on different PLLA membranes. This behavior indicates that cells try to create a better environment to stimulate their growth. This also indicates that Vero cells alter their differentiation pattern once they are producing extracellular matrix molecules related to epithelial differentiation.
Integrating Particle Image Velocimetry and Laser Doppler Velocimetry Measurements of the Regurgitant Flow Field Past Mechanical Heart Valves
Authors: Kini V. , Bachmann C. , Fontaine A. , Deutsch S. , Tarbell J.M.
Published: March 2003

Abstract: This study investigates the transient regurgitant flow downstream of a prosthetic heart valve using both laser Doppler velocimetry (LDV) and particle image velocimetry (PIV). Until now, LDV has been the more commonly used tool in investigating the flow characteristics associated with mechanical heart valves. The LDV technique allows point‐by‐point velocity measurements and provides enough information about the temporal variations in the flow. The main drawback of this technique is the time consuming nature of the data acquisition process in order to assess an entire flow field area. The PIV technique, on the other hand, allows measurement of the entire flow field in space in a plane at a given instant. In this study, PIV with spatial resolution of 0 (1 mm) and LDV with a temporal resolution of 0 (1 ms) were used to measure the regurgitant flow proximal to the Björk‐Shiley monostrut (BSM) valve in the mitral position. With PIV, the ability to measure 2 velocity components over an entire plane simultaneously provides a very different insight into the flow field compared to a more traditional point‐to‐point technique like LDV. In this study, a picture of the effects of occluder motion on the fluid flow in the atrial chamber is interpreted using an integration of PIV and LDV measurements. Specifically, fluid velocities in excess of 3.0 m/s were recorded in the pressure‐driven jet during valve closure, and a 1.5 m/s sustained regurgitant jet was observed on the minor orifice side. Additionally, the effects of the impact and subsequent rebound of the occluder on the flow also were clearly recorded in spatial and temporal detail by the PIV and LDV measurements, respectively. The PIV results provide a visually intuitive way of interpreting the flow while the LDV data explore the temporal variations and trends in detail. This analysis is an integrated flow description of the effects of valve closure and leakage on the pulsatile regurgitation flow field past a tilting‐disc mechanical heart valve (MHV). It further reinforces the hypothesis that the planar flow visualization techniques, when integrated with traditional point‐to point techniques, provide significantly more insight into the complex pulsatile flow past MHVs.
A Blood Pressure Sensor for Long‐Term Implantation
Authors: Bullister Edward , Reich Sanford , D'Entremont Peter , Silverman Neil , Sluetz James
Published: March 2003

Abstract: An implantable flow‐through blood pressure sensor prototype has been developed for use with an implantable left ventricular assist device (LVAD). This sensor incorporates a flat pressure‐sensing diaphragm that is designed to be integral with the wall of a titanium tube that may be placed in the inlet or the outlet flow path of any LVAD. The interior tube flow geometry is transitioned from a round to a D‐shape such that flow separation is eliminated. Bench testing of 3 sensors was performed to characterize the sensor. The worst‐case results showed a maximum nonlinearity of 0.64 mm Hg, a maximum hysteresis of 0.87 mm Hg, and a maximum nonrepeatability of 0.87 mm Hg. Long‐term drift studies of 2 sensors at 193 days and 112 days resulted in a projected annual drift rate of 1.4 and 2.0 mm Hg, respectively. The APEX pressure sensors were evaluated in 5 ventricular assist acute calf experiments in which the sensor outputs were compared with Millar pressure catheter sensors. Pressure output comparisons showed similar pressure tracings. No visible evidence of thrombus formation was found on the APEX sensor compared with thrombus formation found on the Millar catheter at the entrance to the flow path. Tests demonstrated that the blood pressure sensor can accurately measure blood pressure and indicate that it has long‐term stability.
An Ultradurable and Compact Rotary Blood Pump with a Magnetically Suspended Impeller in the Radial Direction
Authors: Masuzawa Toru , Kita Toshiyuki , Okada Yohji
Published: March 2003

Abstract: A magnetically suspended centrifugal blood pump has been developed with a self‐bearing motor for long‐term ventricular assist systems. The rotor of the self‐bearing motor is not only actively suspended in the radial direction, but also is rotated by an electromagnetic field. The pump has a long lifetime because there are no mechanical parts such as seals and motor bearings. An outer rotor mechanism was adopted for the self‐bearing motor. The stator was constructed in the central space of the motor. The rotor shaped thin ring was set at the circumferential space of the stator. Six vanes were extended from the upper surface of the rotor toward the center of the pump to construct an open‐type impeller. The outer diameter and the height of the impeller are 63 mm and 34 mm, respectively. The magnetic bearing method and the servomotor mechanism were adopted to levitate and rotate the rotor. Radial movements of the rotor and rotation are controlled actively by using electromagnets in the stator. Axial movement and tilt of the rotor are restricted by passive stability to simplify the control. The radial gap between the rotor and the stator is 1 mm. A closed‐loop circuit filled with water was used to examine basic performance of the pump. Maximum flow rate and pressure head were 8 L/min and 200 mm Hg, respectively. Maximum amplitude of radial displacement of the impeller was 0.15 mm. The impeller could be suspended completely without touching the casing wall during the entire pumping process. Power consumption of the pump was only 9.5 W to produce a flow rate of 5 L/min against a pressure head of 100 mm Hg. We conclude that the pump has sufficient performance for the implantable ventricular assist system.
Monitoring of Brain Water by Chemical Shift Imaging During Ammonia‐Induced Brain Swelling in Rats After Portacaval Anastomosis
Authors: Venkatasubramanian P.N. , Tom B. , Blei A.T. , Wyrwicz A.M.
Published: March 2003

Abstract: Brain edema is a leading cause of death in acute liver failure (ALF). In experimental models of ALF, an increase in the content of brain water has been inferred indirectly by measuring intracranial pressure or determined directly via analysis of brain tissue postmortem. In this study, noninvasive proton two‐dimensional chemical shift imaging (2‐D CSI) was used to follow the time course of the development of brain edema in a well characterized model, namely ammonium acetate infusion into rats 48 to 72 h after portacaval anastomosis (PCA). Clear differences between control and experimental rat brains were observed, with an increase of brain water signal only in the parietal cortex of the PCA + ammonia group. Selective swelling of the cerebral cortex points to a cytotoxic mechanism in the evolution of brain edema in this model. CSI signal enhancement was much greater than the gravimetrically determined water content increase. The significantly greater signal change observed with 2‐D CSI may reflect enhanced proton density that results from increased water content as well as edema‐related alterations in water relaxation times.
Dose Effect Relationship of Reviparin in Chronic Hemodialysis: A Crossover Study Versus Nadroparin
Authors: Reach I. , Luong N. , Chastang C. , Chakroun M. , Mirshahi S. , Mirshahi M.C. , Soria J. , Desmichels D. , Baumelou A.
Published: March 2003

Abstract: Low molecular weight heparins (LMWHs) are used for prevention of clotting in the dialysis circuit. The aim of this trial was to define the optimal dose of a new LMWH and to test the efficiency of a single dose at the start of the session. Fifteen patients were treated according to a double blind and crossover design during 4 blocks of 5 consecutive reviparin doses assigned randomly as 50, 60, 70, 85, and 100 IU anti‐Xa/kg. Assessment was carried out on screening of fibrin rings or clots in the arterial and venous air traps and on visual detection of fiber in the dialyzer after rinsing. These clinical results were compared to plasmatic anti‐Xa activity and thrombin‐antithrombin (TAT) complex generation. A standard dose of 70 IU anti‐Xa/kg of nadroparin was used as the control. After a bolus of 50 to 100 IU anti‐Xa/kg, the occurrence of fibrin rings and clots in the air traps was dependent on three factors: dose of LMWH, time of the session, and patient status. A bolus of 85 IU anti‐Xa/kg of reviparin was effective and safe for sessions of 4 h. For this dose, plasmatic anti‐Xa activity was 0.96 ± 0.28 IU/ml at Hour 2 and 0.82 ± 0.22 IU/ml at Hour 4. TAT complexes are good markers of the activation of the coagulation. They did not increase during a 4 h session after a reviparin bolus of 100 IU/kg. For the same LMWH dose, the trial shows a great variability of the clinical effect and anti‐Xa activities from one patient to another. A single dose of 85 IU anti‐Xa/kg of reviparin can be used at the start of the dialysis session as a loading dose. We advise adapting the dose during the subsequent sessions according to the appearance of the blood circuit. The benefit of monitoring anti‐Xa activity and TAT complexes could be tested in a further trial.
Intravascular Micropump for Augmented Liver Perfusion: First In Vivo Experience
Authors: Havlík Roman , Kerkhoffs Wolfgang , Jiao Long R. , Schumacher Olivier , Reul Helmut , Habib Nagy
Published: March 2003

Abstract: The aim of this study was to assess the in vivo performance of a new microaxial rotary blood pump developed for long‐term intraportal implantation. The pump, measuring 7 mm in diameter, has a single stage impeller and is powered by a microelectric motor. The pump was implanted into the portal vein in 13 large white pigs under general anesthesia. All animals recovered after the portal pump implantation, and they were observed until the pump failed. The 2 longest running pumps performed for 40 and 36 h, respectively. Either thrombus formation or technical problems, especially in the bearings, were the main causes of pump failure during the experiment. No local or systemic adverse effects were observed during the portal pumping period. Full recovery of the animals following intraportal pump implantation was achieved. However, further technical improvements to the pump are required to maintain a longer performance in vivo.
Platelet Damage Caused by the Centrifugal Pump: Laser‐Light Scattering Analysis of Aggregation Patterns
Authors: Tanaka Masashi , Kawahito Koji , Adachi Hideo , Isawa Hideaki , Ino Takashi
Published: March 2003

Abstract:Platelets are damaged by shear force during centrifugal pumping; however, the mechanism of this damage has not been fully investigated. A new laser‐light scattering (LS) assay method enables quantification of real‐time changes in the number of platelet aggregates of different sizes. Using this method, we assessed the kinetics of platelet damage caused by the centrifugal pump from the standpoint of platelet aggregation capacity. Conventional optical density (OD) and LS methods were used to measure platelet aggregation with a Kowa AG‐10 aggregometer. Platelet aggregation in fresh human blood was evaluated in a mock circuit for 3 h under a flow rate of 5.0 L/min and a pressure head of 100 mm Hg. Test samples were obtained before pumping for control, and at 1, 2, and 3 h after the start of pumping. The test series was begun 8 times. Aggregation after stimulation by 2.0 μg/ml collagen was determined; small (9 to 25 μm), medium (25 to 50 μm), and large (50 to 70 μm) aggregates were counted by the LS method. OD measurement at hourly intervals showed significant reduction in platelet aggregation. The LS method showed that generation of small and medium aggregates was not suppressed during pumping, but that generation of large aggregates was significantly reduced at 2 and 3 h of pumping. Platelet aggregation is significantly suppressed during centrifugal pumping, and the resulting platelet dysfunction is due mainly to inhibited development of small aggregates into larger aggregates.
A Novel Method for Faster Formation of Rat Liver Cell Spheroids
Authors: Okubo Hisashi , Matsushita Michiaki , Kamachi Hirofumi , Kawai Tomoaki , Takahashi Manabu , Fujimoto Tetsuya , Nishikawa Kazutaka , Todo Satoru
Published: March 2003

Abstract: Hepatocyte spheroids are expected to be the main component of the artificial liver bioreactor for their higher function. The preparation of hepatocyte spheroids, however, can require as many as 24 to 96 h. To reduce this time, we investigated a method employing a new technique of rat hepatocyte preparation and a dynamic culture. The modified Seglen's method for standard hepatocyte isolation was altered by elimination of ethyleneglycol bis(aminoethylether) tetraacetate from the first perfusate and calcium from the second perfusate. Isolated hepatocytes were cultured in a spinner flask by spinning at 120 rpm. The modified Seglen's method was used as a control. Cells obtained by the new method were more cohesive and formed a higher proportion of cell aggregates than control cells. In the spinning culture, hepatocytes had a tendency to aggregate and 80% of cells formed spheroids within 6 h of culturing. The mean size of spheroids was 68.5 ± 18.5 μm. Confocal laser scanning microscopy revealed that individual spheroids contained approximately 30% of nonparenchymal cells over their surface. Using the new hepatocyte preparation method followed by a spinning culture, we were able to produce hepatocyte spheroids in as few as 6 h.
Interaction of the Cardiovascular System with an Implanted Rotary Assist Device: Simulation Study with a Refined Computer Model>
Authors: Vollkron Michael , Schima Heinrich , Huber Leopold , Wieselthaler Georg
Published: March 2003

Abstract: In recent years, implanted rotary pumps have achieved the level of extended clinical application including complete mobilization and physical exercise of the recipients. A computer model was developed to study the interaction between a continuous‐flow pump and the recovering cardiovascular system, the effects of changing pre‐ and afterloads, and the possibilities for indirect estimation of hemodynamic parameters and pump control. A numerical model of the cardiovascular system using Matlab Simulink simulation software was established. Data of circulatory system modules were derived from patients, our own in vitro and in vivo experiments, and the literature. Special care was taken to simulate properly the dynamic pressure‐volume characteristics of both left and right ventricle, the Frank‐Starling behavior, and the impedance of the proximal vessels. Excellent correlation with measured data was achieved including pressure and flow patterns within the time domain, response to varying loads, and effects of previously observed pressure‐flow hysteresis in rotary pumps. Potential energy, external work, pressure‐volume area, and other derived heart work parameters could be calculated. The model offers the possibility to perform parameter variations to study the effects of changing patient condition and therapy and to display them with three‐dimensional graphics (demonstrated with the effects on right ventricular work and efficiency). The presented model gives an improved understanding of the interaction between the pump and both ventricles. It can be used for the investigation of various clinical and control questions in normal and pathological conditions of the left ventricular assist device recipient.