Ethical Analysis of Withdrawing Total Artificial Heart Support

Objectives

To describe the characteristics of patients who undergo withdrawal of total artificial heart support and to explore the ethical aspects of withdrawing this life-sustaining treatment.

BD 方案与VAD 方案治疗多发性骨髓瘤的疗效比较

 目的比较硼替佐米联合地塞米松方案（BD方案）与VAD 方案治疗多发性骨髓瘤的临床疗效及安全性。方法回顾性
分析120 例多发性骨髓瘤病例,根据其治疗方案分为：（1）BD 组（ n=37）：其中初治16 例,复发/难治21 例;（2）VAD 组（ n=83）：
其中初治39 例,复发/难治44 例。化疗4~7 个疗程后全面评价两组疗效及副反应。采用EBMT/ABMT 标准判定疗效,并按WHO
标准判断不良反应。结果（1）BD组：中位生存期为43.5 个月,2 年和4 年生存率分别为86.4%和47.3%,平均起效疗程数为
2.06,总有效率为91.9%,其中CR/nCR 32.4%（12/37）,PR 48.6%（18/37）,MR 10.8%（4/37）。初治患者CR/nCR 37.5%（6/16）,
PR 50.0%（8/16）,MR 6.3%（1/16）,NR 6.3%（1/16）,有效率为93.8%;复发/难治患者CR/nCR 28.6%（6/21）,PR 47.6%（10/
21）,MR 14.3%（3/21）,NR 4.8%（1/21）,PD 4.8%（1/21）,有效率为90.5%;（2）VAD 组：中位生存期为29.1 个月,2 年和4 年生
存率分别为64.3%和33.5%,平均起效疗程数为3.09,总有效率为66.3%,其中CR/nCR 12.0%（10/83）,PR 38.6%（32/83）,MR
15.7%（13/83）。初治患者CR/nCR 15.4%（6/39）,PR 38.5%（15/39）,MR 12.8%（5/39）,NR 20.5%（8/39）,PD 12.8%（5/39）,有
效率66.7%;复发/难治患者CR/nCR 9.1%（4/44）,PR 38.6%（17/44）,MR 18.2%（8/44）,NR 18.2%（8/44）,PD 15.7%（7/44）,有
效率为65.9%。字2检验结果显示,2 组方案疗效之间比较差异有统计学意义（ < 0.05）;经Log-rank 检验发现,2 组生存率比较差
异有统计学意义（ < 0.05）;（3）与VAD组相比,BD 组不良反应较轻微,患者耐受性较好。结论与VAD方案相比,BD方案能
达到更高的缓解率,显著延长患者的生存期,并提高患者的生活质量,疗效显著,毒副反应小,耐受性好。     

Treatment of multiple organ failure by a totally implantable ventricular assist device

Multiple organ failure (MOF) becomes an important problem during clinical use of the ventricular assist device (VAD). To improve the clinical record of the VAD, the function of other organs may be vitally important. For that reason, we have been developing a VAD system aiming at improving the function of other organs. Development of the vibrating flow pump (VFP), which can generate a unique flow pattern from 10 to 50Hz, is still ongoing in our institute. In order to evaluate brain blood flow and oxygen consumption, oxyhemoglobin was measured with NIRO (Hamamatsu Photo.) in healthy adult goats. Four healthy adult goats were anesthetized with halothane inhalation, and left thoracotomy was performed for left heart bypass. Oxyhemoglobin in the brain was measured with the recording of the hemodynamic variables during left heart assistance with the VFP system. During left heart bypass with the VFP system, the hemodynamic parameters kept within the normal range, and satisfactory pump output was easily obtained. Pump output was kept within 40%–50% bypass to evaluate the effect of high-frequency oscillating assist flow on brain blood flow with the same cardiac output. Interesting results were observed during the experiments. During 30Hz driving of the VFP left heart assistance, oxyhemoglobin suggested that brain blood flow was significantly increased compared with another drive frequency with the same total cardiac output. These results suggest that we can control brain blood flow with a totally implantable VAD system such as the VFP system, which can control the frequency of the blood flow. Presented in part at the 7th Congress of the International Society for Rotary Blood Pumps, August 26–28, 2000, in Tokyo, Japan     

Considerations and Problems in the Development of the Mini-Spindle Pump

Abstract: The premise for the development of the mini-spindle pump, planned as an implantable device for assisted circulation, was to transport 4 L of water/min in mock circulation with a speed of 12–15,000 rpm against an afterload of 90 mm Hg. After calculations, the resulting first prototype had a spindle rotor with 3 threads (outer diameter, 18 mm; inner diameter, 6.2 mm; length, 45 mm) in a U-shaped housing, driven by an electric motor with a cooling system. In mock circulation, this pump moved 7.8 L of water/min at 18,000 rpm. To avoid animal experiments, its influence on the blood was tested in a Maxima oxygenator. The device circulated 4.2 L of blood/min with the same speed. Because of its high traumatic he-molysis rate (>250 mg% of free hemoglobin after 7 h of pumping), the rotor was modified, first without effect at 2.5 threads and then at 4 threads. In addition, in this third prototype, the flow direction was reversed. This prototype was more effective (4.3 L of blood/min at 12,000 rpm in the oxygenator) and the hemolysis rate, after a pumping duration of 8 h, could only be reduced to 180 mg% of free hemoglobin. As a result, a fourth prototype was developed (i.e., the U-shape of the housing was abandoned). This device functioned better than the third prototype (4.5 L of blood/min at 12,000 rpm in the oxygenator), but the blood trauma increased (220 mg% of free hemoglobin after 7 h of pumping). To find out if the oxygenator may be responsible for the hemolysis problem, the 16th prototype of the large spindle pump was tested in the oxygenator. The result was expected, the level of free plasma hemoglobin was high again (190 mg%). To verify the function of the third and the fourth prototype of the mini-spindle pump, 4 animal experiments were performed. Under normal cardiac conditions, the devices emptied the left ventricle up to 70% with a speed between 10,500 and 11,200 rpm, moving about 6 L of blood/min (afterload between 65 and 90 mm Hg). The hemolysis rates were between 32 and 90 mg% of free hemoglobin in the plasma.     

Computational Prediction of Hemolysis in a Centrifugal Ventricular Assist Device

Abstract: This paper describes the use of computational fluid dynamics (CFD) to predict numerically the hemolysis in centrifugal pumps. A numerical hydrodynamical model, based on the full Navier-Stokes equation, was used to obtain the flow in a vaneless centrifugal pump (of corotating disks type). After proper postprocessing, critical zones in the channel were identified by means of two-dimensional color-coded maps of %Hb release. Simulation of different conditions revealed that flow behavior at the entrance region of the channel is the main cause of blood trauma in such devices. A useful feature resulting from the CFD simulation is the visualization of critical flow zones that are impossible to determine experimentally with in vitro hemolysis tests.     

Closed circuit MR compatible pulsatile pump system using a ventricular assist device and pressure control unit

The aim of this study was to evaluate the performance of a closed circuit MR compatible pneumatically driven pump system using a ventricular assist device as pulsatile flow pump for in vitro 3D flow simulation. Additionally, a pressure control unit was integrated into the flow circuit. The performance of the pump system and its test‐retest reliability was evaluated using a stenosis phantom (60% lumen narrowing). Bland–Altman analysis revealed a good test–retest reliability (mean differences = ?0.016 m/s, limits of agreement = ±0.047 m/s) for in vitro flow measurements. Furthermore, a rapid prototyping in vitro model of a normal thoracic aorta was integrated into the flow circuit for a direct comparison of flow characteristics with in vivo data in the same subject. The pneumatically driven ventricular assist device was attached to the ascending aorta of the in vitro model to simulate the beating left ventricle. In the descending part of the healthy aorta a flexible stenosis was integrated to model an aortic coarctation. In vivo and in vitro comparison showed significant (P = 0.002) correlations (r = 0.9) of mean velocities. The simulation of increasing coarctation grade led to expected changes in the flow patterns such as jet flow in the post‐stenotic region and increased velocities. Magn Reson Med, 2011. © 2011 Wiley‐Liss, Inc.