A Pivot Bearing-Supported Centrifugal Pump for a Long-Term Assist Heart

A pivot bearing-supported centrifugal blood pump has been developed. It is a compact, cost effective, and anti-thrombogenic pump with anatomical compatibility. A preliminary evaluation of five paracorporeal left ventricular assist studies were performed on pre-conditioned bovine (70-100 kg), without cardiopulmonary bypass and aortic cross-clamping. The inflow cannula was inserted into the left ventricle (LV) through the apex and the outflow cannula affixed with a Dacron vascular graft was anastomosed to the descending aorta. All pumps demonstrated trouble free performance over a two-week screening period. Among these five studies, three implantations were subjected for one month system validation studies. All the devices were trouble free for longer than 1 month. (35, 34, and 31 days). After achieving one month studies, all experiments were terminated. There was no evidence of device induced thrombus formation inside the pump. The plasma free hemoglobin levels were within normal ranges throughout all experiments. As a consequence of these studies, a mass production model C1E3 of this pump was fabricated as a short-term assist pump. This pump has a Normalized Index of Hemolysis of 0.0007 mg/100L and the estimated wear life of the impeller bearings is longer than 8 years. The C1E3 will meet the clinical requirements as a cardiopulmonary bypass pump. For the next step, a miniaturized pivot bearing centrifugal blood pump PI-601 has been developed for use as a permanently implantable device after design optimization. The evolution from C1E3 to the PI-601 converts this pivot bearing centrifugal pump as a totally implantable centrifugal pump. A pivot bearing centrifugal pump will become an ideal assist pump for the patients with failing heart.

Therapeutic apheresis application using membrane plasma fractionation technology: present scope and limitations

Membrane technologies have been applied for therapeutic apheresis, such as plasma separation and plasma fractionation. Membrane used for plasma fractionation has a microporous structure with pore sizes in the range of 0.01-0.04 microm. A membrane plasma fractionator is utilized for the second filter in the double filtration plasmapheresis (DFPP) system and is applied for treatment of various diseases. This article summarizes the present scope and limitation of membrane plasma fractionation.

Development of the membrane autotransfusion system prototype-II: MATS-II

This article is the second of a two-part series describing a membrane autotransfusion system, MATS, utilizing plasmapheresis technology. Based on experiences obtained from the first prototype (MATS-I), optimum blood filtration parameters with refined blood and flux pump synchronization were put into an original CPU-board and loaded on a miniaturized, self-operative, and preclinical prototype (MATS-II). This study was conducted to evaluate the MATS-II using diluted blood of various hematocrit concentrations. The results proved that this device could concentrate 4,000-10,000 ml of various hematocrit concentrations into higher than 40% while automatically controlling the flow speed from 250 to 400 ml/min. Also, no significant damage was generated to the red blood cells (RBC). Moreover, the MATS-II salvaged over 90% of platelets together with the RBC. These results suggest that the MATS-II achieves all clinical requirements of an autotransfusion device; it is a continuous hemoconcentration device with minimum damage to cellular components of the blood.

In vitro evaluation study of the membrane autotransfusion system experimental prototype: MATS-I

Membrane Autotransfusion System (MATS) utilizing plasmapheresis technology has been developed in our laboratory. A specially designed polyethylene hollow fiber membrane was utilized. This study was conducted to evaluate performance of the first experimental prototype, MATS-I. The results of this study showed that the MATS-I could concentrate diluted blood at 10% of the initial hematocrit concentration (HCTi) into over 40% after passing through the system at a transmembrane pressure of 70 mm Hg. Moreover, the MATS-I can continuously treat 10,000 ml of diluted blood at various HCTi levels without deteriorating its performances. Even though the MATS-I met all required performances as an autotransfusion system, several areas of improvement of the system were necessary to meet various clinical needs. The next prototype, MATS-II, can be designed based on experiences obtained from the MATS-I. The MATS is smaller, more atraumatic and continuous, and is a faster system when compared to the currently available centrifugal autotransfusion devices.

An emergency balloon occlusion system for a rotary blood pump left ventricular assist system

A fatal outcome is expected in a left ventricular assist system (LVAS) utilizing a rotary blood pump if there is no mechanism to prevent the backflow from the aorta to the heart in the case of acute pump failure. To solve this problem, a passive mechanical clamping system at the outflow graft of a rotary blood pump was developed together with Fuji Systems, Inc., Yokohama, Japan. The system consisted of an emergency clamp port and an occlusion balloon. The balloon was fixed around the outlet graft of the LVAS. In an in vitro study, a fail-safe clamping operation with 2 ml saline injection under 7 L/min flow against 140 mm Hg pressure reduced the flow to 0.5 L/min while the pressure in the system increased to 190 mm Hg. The systems were also applied to 2 in vivo LVAD studies. When the pumps were stopped, there were approximately 3.0 L/min regurgitant flows. The balloon occluder prevented this regurgitant flow effectively against a 100/80 mm Hg arterial pressure. In conclusion, this emergency balloon occlusion system is relatively easy to operate and will work efficiently in all possible clinically encountered malfunctions of the rotary blood pump LVAS.

Long-term in vivo left ventricular assist device study for 284 days with Gyro PI pump

A totally implantable centrifugal artificial heart has been developed. The plastic prototype, the Gyro PI 601, passed 2 day hemodynamic tests as a functional total artificial heart (TAH), 2 week screening tests for anti-thrombogenecity, and a 1 month system feasibility study. Based upon these results, a metallic prototype, the Gyro PI 700 series, was subjected to long-term in vivo left ventricular assist device (LVAD) studies of over 1 month. The Gyro PI 700 series has the same inner dimension and same characteristics of the Gyro PI 601 such as an eccentric inlet port, a double pivot bearing system, and a magnet coupling system. The PI metallic pump is also driven with the Vienna DC brushless motor actuator like the PI 601. The pump-actuator package was implanted in 3 calves in the preperitoneal space, bypassing from the left ventricular (LV) apex to the descending aorta. Case 1 achieved a 284 day survival. Case 2 was euthanized early at 72 postoperative days as a result of the functional obstruction of the inlet port due to the excessive growth of the calf. There was no blood clot inside the pumps of either case. Case 3 is on-going (22 days on July 24, 1998). During these periods, all cases showed no physiological abnormalities. In conclusion, the PI 700 series pump has excellent results as a long-term implantable LVAD.

Preliminary evaluation study of a prototype hollow fiber membrane for the continuous membrane autotransfusion system

A totally new autotransfusion system has been developed utilizing a hollow fiber membrane, based upon plasmapheresis technology. Prior to fabricating the system, it was essential to evaluate the basic performance characteristics of the filter, which was designed particularly for the new system. The objective of this study was to prove or disprove that such a system would be available using this filter. An in vitro study was conducted on the filter using bovine blood. The result of the study showed that the filter could process 2-20% of hematocrit blood at a flow rate greater than 250 ml/min of inlet blood continuously. Moreover, it could concentrate 5-20% hematocrit blood to hematocrit percentages greater than 40% by a single passage through the filter. These results seemed to prove that a rapid, continuous, and compact autotransfusion system could be developed using this filter.

In vitro comparison study of CD63 and CD62P expression after contacting leukocyte filters

CD63 and CD62P have been recognized as platelet activation markers. This study investigated the secretion of these antigens to compare the platelet activation between a newly developed stainless steel leukocyte filter (SSLF) and 7 polyester or polyurethane commercially available leukocyte filters. Flow cytometry demonstrated that the SSLF initiated significantly smaller effects in terms of mean fluorescence intensity of CD63 (p<0.03) and of the amount of CD62P expressing platelets (p<0.002) compared to the polyurethane filters. However, there was no statistical difference between the SSLF and polyester filters. The result of this study suggests that the SSLF caused less platelet activation than the polyurethane filters and has biocompatible characteristics comparable to the currently available polyester filters. Stainless steel was selected because of its physicochemical conductivity. With these results, further evaluation of the SSLF will be continued in an attempt to develop an active immunomodulator using this unique characteristic.

Applications of membrane technologies for therapeutic apheresis

Membrane technologies have been applied for therapeutic apheresis. Membrane plasma separation and plasma fractionation are the most common, and hemodialysis and hemofiltration are also used for the combination methodologies of plasma exchange. This article describes the structure, performance, and application of membranes used for apheresis.

Long-term in vivo left ventricular assist device study with a titanium centrifugal pump

A totally implantable centrifugal artificial heart has been developed. The plastic prototype, Gyro PI 601, passed 2 day hemodynamic tests as a functional total artificial heart, 2 week screening tests for antithrombogenicity, and 1 month system feasibility. Based on these results, a metallic prototype, Gyro PI 702, was subjected to in vivo left ventricular assist device (LVAD) studies. The pump system employed the Gyro PI 702, which has the same inner dimensions and the same characteristics as the Gyro PI 601, including an eccentric inlet port, a double pivot bearing system, and a magnet coupling system. The PI 702 is driven with the Vienna DC brushless motor actuator. For the in vivo LVAD study, the pump actuator package was implanted in the preperitoneal space in two calves, from the left ventricular apex to the descending aorta. Case 1 achieved greater than 9 month survival without any complications, at an average flow rate of 6.6 L/min with 10.2 W input power. Case 2 was killed early due to the excessive growth of the calf, which caused functional obstruction of the inlet port. There was no blood clot inside the pump. During these periods, neither case exhibited any physiologic abnormalities. The PI 702 pump gives excellent results as a long-term implantable LVAD.

Development of a silicone hollow fiber membrane oxygenator for ECMO application

A new silicone hollow fiber membrane oxygenator for extracorporeal membrane oxygenation (ECMO) was developed using an ultrathin silicone hollow fiber, with a 300 microm outer diameter and a wall thickness of 50 microm. The hollow fibers were mechanically cross-wound on the flow distributor to achieve equal distribution of blood flow without changing the fiber shape. The housing, made of silicone coated acryl, was 236 mm long with an inner diameter of 60 mm. The surface area was 1.0 m2 for prototype 211, and 1.1 m2 for prototype 209. The silicone fiber length was 150 mm, and the silicone membrane packing density was 43% for prototype 211 and 36% for prototype 209. Prototype 211 has a priming volume of 208 ml, and prototype 209 has a priming volume of 228 ml. The prototype 211 oxygenator demonstrates a gas transfer rate of 120 +/- 5 ml/min (mean +/- SD) for O2 and 67 +/- 12 ml/min for CO2 under 2 L of blood flow and 4 L of O2 gas flow. Prototype 209 produced the same values. The blood side pressure drop was low compared with the silicone sheet oxygenator (Avecor, 1500ECMO). These results showed that this new oxygenator for ECMO had efficiency similar to the silicone sheet oxygenator that has a 50% larger surface area. These results suggest that the new generation oxygenator using an ultrathin silicone hollow fiber possesses sufficient gas transfer performance for long-term extracorporeal lung support.

Evaluation of platelet adhesion and activation on materials for an implantable centrifugal blood pump

A totally implantable centrifugal artificial heart has been developed in which a pivot bearing supported centrifugal pump is used as a blood pump. The following have been adopted as blood contacting materials in our pump: titanium alloy (Ti-6A1-4V) for the housing and impeller, alumina ceramic (Al2O3) for the male pivots, and ultrahigh molecular weight polyethylene (PE) for the female pivots. Greater antithrombogenicity is required for an implantable blood pump. To examine the thrombogenicity of these materials, we evaluated in vitro platelet adhesion and activation, which may play key roles in thrombogenesis on foreign surfaces. Ti-6A1-4V, Al2O3, and PE were compared with polycarbonate (PC), silicone carbide (SiC), and pure titanium (pTi). Platelet adhesion was assessed using monoclonal antibody (CD61) directed against glycoprotein IIIa. Platelet activation was evaluated by measuring P-selectin (GMP-140) released from irreversibly activated platelets. Each material with a surface area of 16.6 cm2 was incubated with 2.5 ml of plasma or 2.5 ml of heparinized fresh whole blood for 3 h at 37 degrees C. The optical density (OD) at a wavelength of 450 nm for CD61 was 0.93+/-0.35 in PC, 0.34+/-0.13 in PE, 0.27+/-0.13 in pTi, 0.26+/-0.01 in Al2O3, 0.21+/-0.04 in SiC, and 0.12+/-0.12 in Ti-6A1-4V. The GMP-140 levels of the tested materials were not significantly different from the control value (45.9+/-7.2 ng/ml). These results indicate that Al2O3, PE, and Ti-6A1-4V, which are incorporated into our implantable centrifugal pump, have satisfactory antithrombogenic properties in terms of platelet adhesion. However, platelet activation by any material was not observed under the static condition in this study.

Current therapeutic apheresis technologies for inflammatory bowel disease

A large number of physicians have indicated that patients with inflammatory bowel diseases (IBD) such as ulcerative colitis (UC) and Crohn's disease (CD) respond to current apheresis technology treatment. However, the mechanism of the apheresis procedure is undefined for patients with IBD. IBD appears to be caused by a complex of interactions from the genes, environment, and the immune system; therefore, the immune system plays a crucial role in the inflammatory responses. In this process, lots of interactions occur simultaneously, and they cross relate with each other. This review paper briefly discusses the etiology and pathogenesis of IBD and attempts to elucidate the mechanism that occurs after apheresis treatment.

Present status of apheresis technologies: part 4. Leukocyte filter

This article is the fourth of a 4 part series describing the currently available apheresis devices and technologies. The sections include the following: Part 1, Membrane Plasma Separator (published in Vol. 1, No. 1); Part 2, Membrane Plasma Fractionator (published in Vol. 1, No. 2); Part 3, Adsorbent (published in Vol. 1, No. 3); and Part 4, Leukocyte Filter.

Recent advances in the gyro centrifugal ventricular assist device

The gyro pump was developed as an intermediate-term assist pump (C1E3) as well as a long-term centrifugal ventricular assist device (VAD). The antithrombogenic design concept of this pump was confirmed throughout three 1 month ex vivo studies. The normalized index of hemolysis (NIH) of this gyro C1E3 model was lower than that of the BP-80. In the next step, a miniaturized centrifugal blood pump (The Gyro permanently implantable model PI-601) has been developed for use as a permanently implantable device after design optimization. A special motor design of the magnet circuit was utilized in this system in collaboration with the University of Vienna. The priming volume of this pump is 20 ml. The overall size of the pump actuator package is 53 mm in height, 65 mm in diameter, 145 ml of displacement volume, and 305 g in weight. This pump can provide 5 L/min against 120 mm Hg total pressure head at 2,000 rpm. The NIH value of this pump was comparable to that of the BP-80. The gyro PI-601 model is suitable for a VAD. The expected life from the endurance study is approximately 8 years. The evolution from C1E3 to the PI-601 converts this pump to a totally implantable centrifugal pump. Recent technologic advances in continuous flow devices are likely to realize a miniaturized and economical totally implantable VAD.

Effects of ultrathin silicone coating of porous membrane on gas transfer and hemolytic performance

To assess the effect of an ultrathin (0.2 microm) silicone-coated microporous membrane oxygenator on gas transfer and hemolytic performance, a silicone-coated capillary membrane oxygenator (Mera HP Excelung-prime, HPO-20H-C, Senko Medical Instrument Mfg. Co., Ltd., Tokyo, Japan) was compared with a noncoated polypropylene microporous membrane oxygenator of the same model and manufacturer using an in vitro test circuit. The 2 oxygenators showed little difference in the oxygen (O2) transfer rate over a wide range of blood flow rates (1 L/min to 8 L/min). The carbon dioxide (CO2) transfer rate was almost the same in both devices at low blood flow rates, but the silicone-coated oxygenator showed a decrease of more than 20% in the CO2 transfer rate at higher blood flow rates. This loss in performance could be partly attenuated by increasing the gas/blood flow ratio from 0.5 or 1.0 to 2.0. In the hemolysis study, the silicone-coated membrane oxygenator showed a smaller increase in plasma free hemoglobin than the noncoated oxygenator. The pressure drop across both oxygenators was the same. These results suggest that the ultrathin silicone-coated porous membrane oxygenator may be a useful tool for long-term extracorporeal lung support while maintaining a sufficient gas transfer rate and causing less blood component damage.

Anatomical consideration for an implantable centrifugal biventricular assist system

A miniaturized pivot bearing-supported centrifugal blood pump (Gyro PI) has been developed as a long-term biventricular assist system (BiVAS). In this study we determined the anatomical configuration of this system using a bovine model. Under general anesthesia, a left lateral thoracotomy was performed to open the chest. Two Gyro PI-601 pumps for left and right assists were placed in the preperitoneal pocket by a subcostal abdominal incision. The left pump could be placed along the dome of the diaphragm just beneath the apex of the left ventricle. The right pump could be placed next to the left pump. The inlet and outlet ports of both pumps penetrated the diaphragm. The inlet port of the left pump, with a length of 55 mm, was inserted directly into the apex of the left ventricle. A woven Dacron graft (150 mm long, 11 mm inner diameter) was placed between the outlet port of the left pump and the descending aorta. As for the right pump, a 100 mm long and 120 degree angled inflow conduit was placed between the inlet port and the right ventricular infundibulum. The outlet port of the right pump was connected to the main trunk of the pulmonary artery using a 90 mm long, 11 mm inner diameter Dacron graft. We could perform biventricular assistance to confirm the anatomical feasibility of the Gyro implantable centrifugal BiVAS.

Protein adsorption and platelet adhesion on the surface of an oxygenator membrane

Platelet adhesion on an oxygenator membrane is associated with thrombocytopenia or thrombus formation during extracorporeal circulation. The authors evaluated protein adsorption and platelet adhesion on three oxygenator hollow fiber membranes fabricated with polypropylene, silicone, and double layer polyolefin. Adsorbed proteins were analyzed by bicinchoninic acid protein assay, sodium dodecyl sulfate polyacrylamide gel electrophoresis, and Western blot. Platelet adhesion was assessed with enzyme immunoassays using monoclonal antibodies directed against CD42b and CD61. After 3 hr of incubation at 37 degrees C in whole blood, the amount of adsorbed protein was the least on silicone and increased from silicone < double polyolefin < polypropylene. The adsorbed protein pattern was similar; however, silicone showed less adsorption for all protein bands, and the gamma chain of fibrinogen was not detected. In contrast, double polyolefin showed the highest fibrinogen adsorption. The optical density at a wavelength of 450 nm for CD42b was 1.47 +/- 0.35 in polypropylene, 1.16 +/- 0.38 in silicone, and 1.85 +/- 0.19 in double polyolefin (p < 0.01 vs silicone) and for CD61 0.98 +/- 0.39 in polypropylene, 0.91 +/- 0.22 in silicone, and 1.69 +/- 0.25 in double polyolefin (p < 0.01 vs silicone and polypropylene). These data suggest that silicone is advantageous for long term extracorporeal respiratory support in terms of less platelet adhesion and no plasma leakage through the pores.

Present status of apheresis technologies, part 3: adsorbent

This article is the third of a 4 part series describing currently available apheresis devices and technologies. The sections include the following: Part 1: Membrane Plasma Separator (published in Vol. 1, No. 1) (1); Part 2: Membrane Plasma Fractionator (published in Vol. 1, No. 2) (2); Part 3: Adsorbent; and Part 4: Leukocyte Filter.

Development and initial testing of a permanently implantable centrifugal pump

To be able to salvage heart failure patients, the need for an economical permanent ventricular assist device is increasing. To meet this increasing demand, a miniaturized centrifugal blood pump has been developed as a permanently implantable device. The Gyro permanently implantable model (PI-601) incorporates a sealless design with a blood stagnation free structure. The pump impeller is magnetically coupled to the driver magnet in a sealless manner. This pump is atraumatic and antithrombogenic and incorporates a double pivot bearing system. A miniaturized actuator was utilized in this system in collaboration with the University of Vienna. The priming volume of this pump is 20 ml. The overall size of the pump actuator package is 53 mm in height and 65 mm in diameter, 145 ml of displacement volume, and 305 g in weight. Testing to date has included in vitro hydraulic performance and hemolysis. This pump can provide 5 L/min against a 110 mm Hg total pressure head at 2,000 rpm and 8 L/min against 150 mm Hg at 2,500 rpm. The normalized index of hemolysis (NIH) value of this pump was 0.0028 g/100 L at 5 L/min against 100 mm Hg. A preliminary anatomical study revealed the possibility of the implantability of 2 such systems in biventricular bypass at a preperitoneal location. This system is feasible for use as a permanently implantable biventricular assist device.

Present status of apheresis technologies: Part 2. Membrane plasma fractionator

This article is the second of a 4 part series describing currently available apheresis devices and technologies. The sections will include: Part 1: Membrane Plasma Separator (published in Vol. 1); Part 2: Membrane Plasma Fractionator: Part 3: Leukocyte Filter; and Part 4: Adsorbent.

A pivot bearing-supported centrifugal pump for a long-term assist heart

A pivot bearing-supported centrifugal blood pump has been developed. It is a compact, cost effective, and anti-thrombogenic pump with anatomical compatibility. A preliminary evaluation of five paracorporeal left ventricular assist studies were performed on pre-conditioned bovine (70-100 kg), without cardiopulmonary bypass and aortic cross-clamping. The inflow cannula was inserted into the left ventricle (LV) through the apex and the outflow cannula affixed with a Dacron vascular graft was anastomosed to the descending aorta. All pumps demonstrated trouble free performance over a two-week screening period. Among these five studies, three implantations were subjected for one month system validation studies. All the devices were trouble free for longer than 1 month. (35, 34, and 31 days). After achieving one month studies, all experiments were terminated. There was no evidence of device induced thrombus formation inside the pump. The plasma free hemoglobin levels were within normal ranges throughout all experiments. As a consequence of these studies, a mass production model C1E3 of this pump was fabricated as a short-term assist pump. This pump has a Normalized Index of Hemolysis of 0.0007 mg/100L and the estimated wear life of the impeller bearings is longer than 8 years. The C1E3 will meet the clinical requirements as a cardiopulmonary bypass pump. For the next step, a miniaturized pivot bearing centrifugal blood pump P1-601 has been developed for use as a permanently implantable device after design optimization. The evolution from C1E3 to the PI-601 converts this pivot bearing centrifugal pump as a totally implantable centrifugal pump. A pivot bearing centrifugal pump will become an ideal assist pump for the patients with failing heart.

Present status of apheresis technologies: Part 1. Membrane plasma separator

This article is the first of a 4 part series describing currently available apheresis devices and technologies. The sections will include: Part 1, Membrane plasma separator; Part 2, Membrane plasma fractionator; Part 3, Leukocyte filter; and Part 4, Adsorbent.

Membrane apheresis technology: historical perspective and new trends toward bioincompatible systems

During the past 25 years, membrane apheresis technology has been well developed through the use of biocompatible devices and immunomodulation. Now, however, we must move into a new era reconsidering the concepts of apheresis technology and considering the urgent need to develop a bioincompatible apheresis system. In the past, our aim in this field was to develop the best blood compatible system possible. With these systems, best efforts were made to reduce procedurally induced immunomodulation effects. However, it is these authors' opinion that procedurally induced immunomodulation effects should be augmented rather than reduced by incorporating such a bioincompatible apheresis system. Augmented immunoactivation and immunosuppression introduced by such systems should add therapeutic effects to the apheresis procedures. Therefore, we anticipate that the current marginally effective diseases may benefit from this strategic change in apheresis procedures.

Strategy of leukocyte filtration for immunomodulation: development of stainless steel leukocyte filter

Commercially available leukocyte filters are frequently used to prepare leukocyte depleted blood products for prevention of transfusion reactions. Recently, immunomodulation by using leukocyte filtration was evaluated. At this time, a new leukocyte filter was fabricated with a 4 microm diameter stainless steel fiber. The goal of this study was to assess the efficiency of the stainless steel filter for leukocyte and platelet removal by comparison with the polyester filter that is commercially available. The production of humoral factors, including interleukin-1 beta, tumor necrosis factor-alpha, and interleukin-1 receptor antagonist (IL-1 Ra), was also evaluated. The results show that the stainless steel filter has more than 2 times greater efficiency in leukocyte removal than the polyester filter. Furthermore, the cytokine studies indicate good biocompatibility of the filter, and the stainless steel filter has a possibility of inhibiting inflammatory cytokines by inducing interleukin-1 receptor.

Cytokine production and protein adsorption in a stainless steel filter used for leukocyte reduction

A new metallic filter made from a stainless steel fiber has been under development. To evaluate biocompatibility of this filter, the authors compared cytokine production with that of stainless steel fibers and polyester fibers by using a mononuclear cell culture. Furthermore, adsorbed proteins on each fiber were identified by using sodium-dodecyl sulfate (SDS)-polyacrlyamide gel electrophoresis (PAGE). The levels of tumor necrosis factor (TNF)-alpha in the cultured supernatant without fibers as the control, with polyester fibers, and with stainless steel fibers were 28.1 +/- 8.1, 39.3 +/- 2.6, and 29.1 +/- 6.7 pg/ml, respectively. The levels of interleukin (IL)-1 beta were 7.6 +/- 3.2, 8.9 +/- 1.5, and 8.9 +/- 2.1 pg/ml, respectively. The IL-4 levels were less than 0.25 pg/ml, and the interferon-tau levels were less than 7.8 pg/ml in all three conditions. The amount of adsorbed proteins was 3.39 +/- 0.27 microgram/cm2 for the polyester fibers and 2.72 +/- 0.23 microgram/ cm2 for the stainless steel fibers. The protein bands adsorbed to the polyester fibers by SDS-PAGE analysis were observed at approximately 180, 120, 90, 76, 67, 59, 56, and 28 kd molecular weight. In contrast, the protein bands adsorbed to the stainless steel fibers were observed at 90, 76, 67, 62, 56, 28, and 12 kd molecular weight. Thus, the proteins adsorbed to the stainless steel fibers differed from those on the polyester fibers. By western blot analysis, the amounts of albumin, IgG tau chain, and fibronectin adsorbed on the stainless steel fibers were smaller than those on the polyester fibers. The results of this study suggest that the stainless steel fibers do not stimulate monocytes, Th1, and Th2 cells. In addition, lesser adsorption of IgG tau chain and fibronectin may indicate that the stainless steel is a superior material for anti thrombogenicity compared to polyester.

Development of a membrane oxygenator for ECMO using a novel fine silicone hollow fiber

One of the limitations of conventional silicone hollow fiber oxygenators compared with microporous membrane oxygenators is poor gas permeability. However, the silicone hollow fiber is free from plasma leakage, which is the major life limiting factor of the microporous membrane oxygenator. It has been difficult to fabricate a fine, thin hollow fiber for reduction of resistance to gas permeability because of the poor mechanical strength of conventional silicone materials. The authors developed a novel silicone material with sufficient mechanical strength, and a fine silicone hollow fiber with a diameter of 30 microns and wall thickness of 50 microns, which is approximately half that of a conventional silicone hollow fiber. Using this newly developed silicone hollow fiber, the authors developed a compact extracapillary flow membrane oxygenator. The oxygenator consists of fine silicone hollow fibers inserted in a housing made of polycarbonate. The housing is a cylindrical case, 20 cm long and 55 mm in inside diameter. The hollow fibers are cross-wound. The surface area of the membrane is 2.0 m2, and priming volume is 230 ml. Gas transfer performance of the newly developed oxygenator was evaluated by in vitro experiments. Oxygen and carbon dioxide transfer rates were 195 ml/min and 165 ml/min, at a blood flow rate 3 L/min. The novel silicone membrane oxygenator developed in this study can be used for extended duration in such applications as extracorporeal membrane oxygenation.

An effective LDL removal filter for the treatment of hyperlipidemia

On-line membrane plasma fractionation techniques have made semiselective removal of pathological macromolecules practical. However, several problems such as cryogel formation exist when the procedure is performed at ambient temperature. Cryogel formation takes place when heparinized plasma is cooled below 35 degrees C and when it tends to occlude the pore structure of the secondary filter membrane resulting in a poor molecular cut off of the macromolecular filter. Thermofiltration is one of the on-line plasma fractionation techniques used when warming plasma from 37 to 42 degrees C to prevent cryogel formation. Thermofiltration enhanced the performance of the lipofilter (Kuraray 4A) and demonstrated better molecular cut off between low density lipoprotein (LDL) cholesterol and high density lipoprotein (HDL) cholesterol than double filtration plasmapheresis (DFPP). An improved lipofilter (Kuraray 5A) has been developed and has shown better molecular cut off between LDL cholesterol and HDL cholesterol than the 4A filter. However, cryogel formation still occurred even using the 5A filter during the DFPP procedure. Thermofiltration maintains the performance of the secondary filter by preventing cryogel formation. Further studies are required to evaluate the enhanced performance of the 5A filter by thermofiltration.

In vitro evaluation of a relationship between human serum- or plasma-material interaction and polymer bulk hydroxyl and surface oxygen content

To evaluate serum- or plasma-material interactions and a relationship between such interactions and membrane properties such as bulk hydroxyl percentage and surface oxygen percent, medical polymeric membranes with extremely different hydroxyl percentage and surface oxygen percentage were evaluated with normal human serums or plasmas. Six types of mini-membrane modules (hydroxyl & surface oxygen %) were studied including cellulose triacetate (CA; 0 & 34.7%), Cuprophan (CP; 31.5 and 37.4%), ethylene vinyl alcohol (EVAL; 30.4 and 25.3%), polyacrylonitrile (PAN; 1.5 and 10.2%), polysulfone (PS-F; 0 and 14.2%), and a polymer alloy of polysulfone (PS-K; 0 and 16.2%). Post-perfusion values of biochemical solutes and complement components for PAN and both PS membranes were smaller than those for sham, CA, CP, and EVAL membrane module perfusions. C3a and C4a concentrations showed no significant differences among all membranes except PS-K. Mononuclear cell transformation functions to all mitogens for serums in contact with CA and CP membranes were suppressed versus sham and PAN and both PS membranes. Fibrinogen concentration changes for plasma in contact with EVAL, PAN, and PS-F membranes were significantly smaller than sham, and a significant prolongation of APTT was found for only EVAL versus sham, CA, and CP. Higher surface oxygen percentages (CA, CP > EVAL > PAN, both PS) but not hydroxyl content were associated with lower protein adsorption and higher suppressive transformation function results. These results suggest that surface oxygen percentage may be an important indicator of biocompatibility.

Exchange blood transfusion and on-line plasma exchange for sepsis in infants

During the last 6 years, 19 infants with sepsis have been treated with exchange blood transfusions 47 times, and 13 patients survived. However, this procedure is compromised by antibody formation against WBCs and platelets. Accordingly, a miniature system for on-line plasma exchange (PE) between septic infant and healthy parent has been developed and evaluated using a canine model. Escherichia coli, at a dose of 5 X 10(9) CFU/ml/kg, was injected intravenously into 17 puppies that were divided into 3 groups; untreated; sham treated; and PE in which 80 ml/kg of plasma in each septic puppy was replaced during 2 hr with fresh plasma simultaneously obtained from healthy adult dogs. Four of 5 puppies survived in the PE group, while all other puppies died within 24 hr. In the PE group, viable cell counts of E. coli and endotoxin decreased significantly, and opsonic activity improved. This system is effective and applicable for treatment of sepsis in infants.

Ex vivo preclinical evaluation of membrane plasma separators

Four different types of hollow-fiber membrane plasma separators, constructed of cellulose acetate, polyvinyl alcohol, polyethylene, and polymethylmethacrylate membranes, were evaluated in ex vivo dog perfusions under conditions simulating their clinical use. An arteriovenous (A-V) fistula constructed in the dogs for blood access enabled repeated access to be achieved without surgical intervention. All modules produced transient leukopenia and a reduction of platelet counts. The polymethylmethacrylate module showed minimum reductions of white blood cell counts and CH50. The early leukocyte count reduction in membrane plasmapheresis is most likely related to the magnitude of complement activation by the membrane, as is seen with hemodialysis.