Molecular surgery for the treatment of malignant tumors: bioincompatible material apheresis for cancer therapy?

Controlled immunological shock, induced by bioincompatible material apheresis for cancer (BIC MAC) therapy, produces an immunoactive status in experimental subjects. However, in order to provide a safe, painless, effective, and reproducible BIC MAC therapy, it is mandatory to provide general anesthesia with endotracheal intubation not only during apheresis procedures of 1-h duration but also for an additional 5 h. Using this procedure, there was no mortality experienced during animal experiments. Also, there were no procedurally related physical or sensory abnormalities demonstrated. This general anesthesia of 6 h covered not only the initial 30 min of the hypotension and hypoxic stages but also the recovery stages to hemodynamically normalize the experimental animals. After 6 h, the accumulated leukocytes in the lung are released back to the systemic circulation. In general, granulocytes decreased almost 100% while lymphocytes decreased only 40-50%. During these 6 h, increases of cytokines (tumor necrosis factor-α, interleukin-6, etc.) sometimes up to 1000 times occurred. After the 6-h procedure, leukocytes returned nearly to preoperative levels but tended to be continuously increased. After the fourth day, leukocyte counts more than doubled. These cellular and humoral activations were normalized after 2 weeks. These studies were conducted on six normal mongrel dogs. Currently, similar studies are planned to be conducted on tumor-bearing experimental animals. This procedurally induced immunoactivation by apheresis may be able to produce effective apoptosis in malignant tumor cells.

Preliminary studies for the development of a second generation granulocytapheresis (G-CAP) column. Part II: in vitro and ex vivo studies.

Our previous studies concluded Egyptian cotton was the most appropriate material for making a second generation granulocytapheresis (G-CAP) column as structural dimensions of the cotton fibers are able to attract granulocytes. Unfortunately, it is considered to be blood incompatible as its fibers are of non-synthetic origins. In this study we examined the alteration of the removal rates of blood cells with different surface modifications of Egyptian cotton to enhance its blood compatibility. The surface-modified cotton fibers were compared after three kinds of combination treatments. There were no differences in the removal rates of white blood cells (WBCs) and particularly neutrophils with the use of three kinds of biolized cottons. Next, an ex vivo animal study with a healthy dog was performed with the prototype of the G-CAP column. The dog's blood pressure (BP) decreased to approximately 80% of the initial values of BP at 20 min after the start of the extracorporeal circulation. The decrease in BP gradually reverted to normal. WBCs and particularly neutrophils decreased significantly at 15 min after the start of the extracorporeal circulation and remained low during the extracorporeal circulation. The ability of this column to remove WBCs was maintained during extracorporeal circulation. Especially, neutrophils at the inlet of the column were thoroughly removed for 1 h. Based upon these results, a second generation G-CAP column could be fabricated with Egyptian cotton and applied for clinical use on the condition that the biocompatibility of the Egyptian cotton needs to be improved by the appropriate biolization method.

The need to change our objective for artificial heart development: from totally implantable permanent ventricular assist devices to wearable therapeutic ventricular assist devices.

As a therapeutic VAD to be combined with drugs, apheresis, and cellular implants, it is advisable to develop a wearable VAD for less than 6 months of application. Such an example was shown by describing the therapeutic BCM Gyro centrifugal VAD.

Preliminary studies for the development of a second generation granulocytapheresis (G-CAP) column.

The preliminary studies for developing a second generation granulocytapheresis (G-CAP) column were made. In the past, the G-CAP column has been used for the treatment of ulcerative colitis and rheumatoid arthritis. However, recent clinical studies have revealed that the therapeutic effects of the G-CAP column are not significant compared with those of the sham column. These results were considered to be due to insufficient reduction of granulocytes. Thus, development of a better granulocyte removal column was attempted. Realizing that white cells adhered on small-diameter synthetic fibers of 1-2 microm, small diameter cotton fibers were subjected to the studies of their granulocyte-removing capabilities. Three types of cotton, Pakistani, Australian and Egyptian cottons, were evaluated using normal human blood in vitro. Miniature columns were made of each fiber, and CBC and WBC differentiation was compared between pre- and post-filtered blood. The Egyptian cotton removed leukocytes, especially granulocytes, the most efficiently of the three types of cotton. The Egyptian cotton's granulocyte adhesion properties were not altered after different chemical treatments. A 4-ml column of packaged Egyptian cotton with a density of more than 0.125 g/ml could remove granulocytes effectively up to 80 ml of blood passages. Based upon these studies, second generation G-CAP could be carried out with Egyptian cotton fibers as a scaled-up clinical module.

A new transcutaneous energy transmission system with hybrid energy coils for driving an implantable biventricular assist device.

We have developed a new transcutaneous energy transmission (TET) system for a totally implantable biventricular assist device (BVAD) system in the New Energy and Industrial Development Organization (NEDO) artificial heart project. The TET system mainly consists of an energy transmitter, a hybrid energy coil unit, an energy receiver, an internal battery system, and an optical telemetry system. The hybrid energy coil unit consists of an air-core energy transmission coil and an energy-receiving coil having a ferrite core. Internal units of the TET system are encapsulated in a titanium alloy casing, which has a size of 111 mm in width, 73 mm in length, and 25 mm in height. In in vitro experiments, the TET system can transmit a maximum electric energy of 60 Watts, and it has a maximum transmission efficiency of 87.3%. A maximum surface temperature of 46.1 degrees C was measured at the ferrite core of the energy-receiving coil during an energy transmission of 20 Watts in air. The long-term performance test shows that the TET system has been able to operate stably for over 4 years with a decrease of energy-transmission efficiency from 85% to 80%. In conclusion, the TET system with the hybrid energy coil can overcome the drawback of previously reported TET systems, and it promises to be the highest performance TET system in the world.

Experimental evaluation of a new antithrombogenic stent using ion beam surface modification.

A new antithrombogenic stent using ion beam surface modification nanotechnology was evaluated. The ion stent is being developed to inhibit acute and chronic stent-related thrombosis. Thirty self-expanding mesh stents were fabricated from Ti-Ni metal wires with a dimension of 4 mm (diameter) x 25 mm (length) x 0.15 mm (thickness). Twenty stents were coated with type I collagen and irradiated with a He(+) ion beam at an energy of 150 keV with fluences of 1 x 10(14) ions/cm(2) (ion stent group). Ten stents had no treatment (non-ion stent group). The self-expanding stents were implanted into the right and left peripheral femoral arteries of 15 beagle dogs (vessel diameter approximately 3 mm) via a 6Fr catheter under fluoroscopic guidance. Heparin (100 units/kg) was administered intravenously before implantation. Following stent implantation, no antiplatelet or anticoagulant drugs were administered. The 1-month patency rate for the non-ion stent group was 10% (1/10), and for the ion stent group it was 80% (16/20) with no anticoagulant or antiplatelet drugs given after stent implantation (P = 0.0004 by Fisher's exact test). Ten stents remain patent after 2 years in vivo with no anticoagulant or antiplatelet drugs. These results indicate that He(+) ion-implanted collagen-coated Ti-Ni self-expanding stents have excellent antithrombogenicity and biocompatibility. This ion stent is promising for coronary and cerebral stent applications.

Three-dimensional ultrasound imaging model of mitral valve regurgitation: design and evaluation.

We describe the development of a cardiac flow model and imaging chamber to permit Doppler assessment of complex and dynamic flow events. The model development included the creation of a circulatory loop with variable compliance and resistance; the creation of a secondary regurgitant circuit; and incorporation of an ultrasound imaging chamber to allow two-dimensional (2D) and three-dimensional (3D) Doppler characterization of both simple and complex models of valvular regurgitation. In all, we assessed eight different pulsatile regurgitant volumes through each of four rigid orifices differing in size and shape: 0.15 cm(2) circle, 0.4 cm(2) circle, 0.35 cm(2) slot and 0.4 cm(2) arc. The achieved mean (and range) hemodynamic measures were: peak trans-orifice pressure gradient 117 mm Hg (40 to 245 mm Hg), trans-orifice peak Doppler velocity 560 cm/s (307 to 793 cm/s), Doppler time-velocity integral 237 cm (111 to 362 cm), regurgitant volume 43 mL (11 to 84 mL) and orifice area 0.32 cm(2) (0.15 to 0.4 cm(2)). The model was designed to optimize Doppler signal quality while reflecting anatomic structural relationships and flow events. The 2D color Doppler, 3D color Doppler and continuous wave Doppler quality was excellent whether the data were acquired from the imaging window parallel or perpendicular to the long-axis of flow. This model can be easily adapted to mimic other intracardiac flow pathology or assess future Doppler applications.

In vitro validation of real-time three-dimensional color Doppler echocardiography for direct measurement of proximal isovelocity surface area in mitral regurgitation.

The 2-dimensional (2D) color Doppler (2D-CD) proximal isovelocity surface area (PISA) method assumes a hemispheric flow convergence zone to estimate transvalvular flow. Recently developed 3-dimensional (3D)-CD can directly visualize PISA shape and surface area without geometric assumptions. To validate a novel method to directly measure PISA using real-time 3D-CD echocardiography, a circulatory loop with an ultrasound imaging chamber was created to model mitral regurgitation (MR). Thirty-two different regurgitant flow conditions were tested using symmetric and asymmetric flow orifices. Three-dimensional-PISA was reconstructed from a hand-held real-time 3D-CD data set. Regurgitant volume was derived using both 2D-CD and 3D-CD PISA methods, and each was compared against a flow-meter standard. The circulatory loop achieved regurgitant volume within the clinical range of MR (11 to 84 ml). Three-dimensional-PISA geometry reflected the 2D geometry of the regurgitant orifice. Correlation between the 2D-PISA method regurgitant volume and actual regurgitant volume was significant (r(2) = 0.47, p <0.001). Mean 2D-PISA regurgitant volume underestimate was 19.1 +/- 25 ml (2 SDs). For the 3D-PISA method, correlation with actual regurgitant volume was significant (r(2) = 0.92, p <0.001), with a mean regurgitant volume underestimate of 2.7 +/- 10 ml (2 SDs). The 3D-PISA method showed less regurgitant volume underestimation for all orifice shapes and regurgitant volumes tested. In conclusion, in an in vitro model of MR, 3D-CD was used to directly measure PISA without geometric assumption. Compared with conventional 2D-PISA, regurgitant volume was more accurate when derived from 3D-PISA across symmetric and asymmetric orifices within a broad range of hemodynamic flow conditions.

Non-cardiac surgery applications of extracorporeal circulation.

Although the efficacy of extracorporeal circulation (ECC) is well established for open-heart surgery, application of ECC in other surgical areas has not been given much attention. Advances in the related surgical technique and anesthetic management combined with refinements in the ECC procedure itself have encouraged several institutions to use ECC for complex non-cardiac surgeries. ECC is beginning to be used for circulatory support or tissue oxygenation during surgery on the lung, brain, liver, and kidney as well as in emergency situations. With ECC, difficult and complex surgeries can be performed more safely, and the success rate of certain surgeries has been positively affected. It is important that the surgeon, anesthesiologist, and perfusionist are trained in non-cardiac surgery applications of ECC. Thus, we review here non-cardiac uses that have emerged and summarize the related procedures.

Ten-year NEDO BVAD development program: moving forward to the clinical arena.

Since 1995, the Baylor Group has been developing a totally implantable NEDO BVAD system. This 10-year program was completed in March 2005, and preparation for clinical trials is underway. This article summarizes the entire 10-year NEDO program and describes the strategy for clinical trials. The project aimed to achieve: (1) dual centrifugal pumps with the ability of full biventricular support, (2) a compact system implantable into small adults, (3) a totally implantable system with transcutaneous energy transmission system (TETS), (4) a durable system with a lifetime of over 5 years, and (5) a system free of thrombus and with minimal hemolysis. The final goals are to complete preclinical system evaluations and commence the clinical trials in the near future. In vitro studies have demonstrated a pump capacity of over 8.5 l/min and an Index of Hemolysis of <0.004 g/100 l. The pump-bearing life expectancy was over 5 years. To date, eight pumps endured in vivo studies of over 3 months without complications, including thromboembolic events. The in vitro endurance studies of eight pumps are longer than 1 year. There were no mechanical malfunctions or pump failure. A stepwise clinical trial is being planned: Step1, a wearable BVAD/VAD will be clinically studied; Step 2, the BVAD/VAD will be implanted intracorporeally without TETS; and, Step 3, a totally implantable system will be clinically evaluated. The NEDO BVAD system has completed preclinical testing. Clinical trial preparation is underway.

Indirect flow rate estimation of the NEDO PI Gyro pump for chronic BVAD experiments.

In totally implantable ventricular assist device systems, measuring flow rate of the pump is necessary to ensure proper operation of the pump in response to the recipient's condition or pump malfunction. To avoid problems associated with the use of flow probes, several methods for estimating flow rate of a rotary blood pump used as a ventricular assist device have been studied. In the present study, we have performed a chronic animal experiment with two NEDO PI gyro pumps as the biventricular assist device for 63 days to evaluate our estimation method by comparing the estimated flow rate with the measured one every 2 days. Up to 15 days after identification of the parameters, our estimations were accurate. Errors increased during postoperation days 20 to 30. Meanwhile, their correlation coefficient r was higher than 0.9 in all the acquired data, and estimated flow rate could simulate the profile of the measured one.

Development of a clipped single-bag with bicarbonate replacement fluid to ensure proper mixing.

A clipped single-bag for bicarbonate replacement fluid was developed to ensure proper mixing before administering to the patient. Nonmixture can cause imbalances of electrolytes and pH, which is a key problem for the current double-bag type bicarbonate replacement fluid sets. To resolve this problem, this single bag properly mixes the solutions before use. The new bag consists of a clip that is placed in the middle to keep the two solutions separated and sealed. When the caregiver is ready to administer treatment, the bag is simply unfolded and the clip automatically detaches, releasing the fluids. Thereby, the bicarbonate fluids are effectively mixed. An optimal clip size with an outer diameter of 16 mm and thickness of 2 mm was determined using compression tests and drop tests. This bag may be a safer and more effective way to provide proper replacement fluid supply for both hemofiltration and hemodiafiltration.

SELCAB (self-lung cardiac bypass) procedures for pediatric patients.

Cardiopulmonary bypass (CPB) for pediatric heart surgeries is not ideal. The currently available systems have a priming volume of 400-1,200 ml, requiring substantial hemodilution. CPB also subjects immature lung tissue to unphysiologic conditions. Exposure of the pediatric patient's blood to the large surface areas of foreign materials associated with an oxygenator results in humoral and cellular impacts on the pediatric patient's immature organs and should be avoided. For selected cases of pediatric heart surgeries, the SELCAB (self-lung cardiac bypass) procedure would be advantageous over CPB. This procedure is equivalent to a biventricular assist device (BVAD) implantation. To distinguish this procedure from long-term BVAD, a BVAD implantation of less than 2 weeks is referred to as SELCAB. Also, the SELCAB's inflow cannulations are either in atria or veins, whereas BVAD inflow cannulations are in ventricles. Advantages and disadvantages of SELCAB are discussed. The physiologic acceptance of SELCAB procedures in immature calves (pediatric model), with beating and nonbeating natural hearts for as long as 3 months, is described. The SELCAB and BVAD systems developed by these authors are also described in this article.

Non-blood contacting biventricular support for severe heart failure.

BACKGROUND: Direct mechanical ventricular actuation (DMVA) is a non-blood contacting method of biventricular support. DMVA employs a vacuum attached, pneumatically regulated, flexible membrane to transfer both systolic and diastolic forces to the ventricular myocardium. The purpose of this study was to determine if DMVA effectively restores pump performance when applied to the severely failing heart. METHODS: Bovines (n = 10) underwent thoracotomy and were instrumented for continuous hemodynamic monitoring. Cardiac failure was induced by beta1-blockade to achieve a cardiac index of < 1.5 l/min/m2 for 1 hour. Heart rate was maintained at 100 bpm by atrioventricular sequential pacing. Synchronous DMVA support was then applied for 3 hours. RESULTS: Eight animals achieved significant reductions in cardiac index and mean arterial pressures (35%* and 43%* control, respectively; *p < 0.05). DMVA restored cardiac index to baseline and significantly increased arterial pressures (p < 0.05; DMVA versus cardiac failure). Pulmonary flow and mean pulmonary artery pressures were similar to baseline during DMVA (p = NS). Pathologic exam did not demonstrate evidence of significant device trauma. CONCLUSIONS: DMVA support can effectively restore pump performance of the acutely failing heart. Synchronization may be inherent to the stimulus of cardiac compression. These data further substantiate DMVA's potential as an adjunct to the field of circulatory support.

Feasibility of a new hollow fiber silicone membrane oxygenator for long-term ECMO application.

Currently in United States, there are no clinically-applicable hollow fiber extracorporeal membrane oxygenation (ECMO) oxygenators available. Therefore, our laboratory is in the process of developing a silicone hollow fiber membrane oxygenator for long-term ECMO usage. This oxygenator incorporates an ultrathin silicone hollow fiber. At this time, a specially-modified blood flow distributor (one chamber distributor) is centered in the module to prevent blood stagnation. An ex vivo long-term durability test for ECMO was performed using a healthy miniature calf for 2 weeks. Venous blood was drained from the left jugular vein of a calf, passed through the oxygenator and infused into the left carotid artery using a Gyro C1E3 centrifugal blood pump. A successful 2-week ex vivo experiment was performed. The O2 and CO2 gas transfer rates were maintained at the same value of 40 m/min at a blood flow rate of 1 L/min flow and V/Q=3 (V=gas flow rate; Q=blood flow rate). The plasma free hemoglobin was maintained around 5 mg/dl. After the experiment, no blood clot formation was observed in the module and no abnormal necropsy findings were found. These data suggest that the performance of this newly-improved oxygenator was stable, reliable, and acceptable for long-term ECMO.