ABSTRACT
Objective To observe the therapeutic effect of folic acid on transient ischemic attack(TIA)patients with homocysteinaemia (Hcy ). Methods 129 patients of primary TIA with Hcy were divided into two groups randomly. The observation group ( n = 65 )was administered with conventional therapy and folic acid, and the control group ( n=64 ) was only given conventional therapy. The variances of the plasma HCA level three months later were compared, and remission rate of TIA and complete stroke incidence one year later were analyzed between two groups. Results The Hcy incidence rate of TIA patients was up to 41.4%. Three months later, the plasma HCA level of observation group was lower than control group( ( 14.27 ± 6. 13 ) μmol/L vs (24.99 ± 6.87 )μmol/L, t=2.799, P＜0. 01 ) ,and much lower than that of the control group post-treatment ( ( 14. 27 ±6. 13)μmol/L vs (24.68 ± 6.89) μmol/L, t = 2.735, P ＜ 0.01 ). One year later, the complete stroke incidence of TIA in observation group was lower than that of the control group(9.8% vs 25.0%, P＜0.05 ) ,and complete remission rate was higher than the latter(73.8% vs 50.0%, P ＜ 0. 01 ). Conclusion Folic acid can decrease the plasma HCA level of TIA patients with Hcy efficiently,and improve the prognosis of such patients.
ABSTRACT
BACKGROUND: Axial-flow blood pump is a main pump for ventricle assistance. Previous researches demonstrate that poor hemocompatibility of blood pump is an important factor for hemolysis and thrombus.OBJ ECTTVE: To design an axial-flow blood pump based on previous kinds of blood pumps through changing whole appearance and impeller shape of the pump by using Computer-Aided Design CAD) and Computational Fluid Dynamics (CFD), and manufacture it successfully.DESIGN: Rationality of theoretical design was verified by practical tests.SETTTNG: Beijing Anzhen Hospital of Capital University of Medical Sciences Department of Biomedical Engineering,Beijing Institute of Heart, lung and Blood Vessel Diseases; the Faurteenth Institute of China-Aerospace Science and Industry Corporation.MATERIALS: Body of blood pump and impeller were titanium alligation, and shaft bearing was ceramic. Test in vitro was accorded to artificial ventricular assist device which was provided by Department of Biomedical Engineering, Beijing Anzhen Hospital of Capital University of Medical Sciences. Experimental goats were provided by Experimental Animal Center, Beijing Anzhen Hospital of Capital University of Medical Sciences.METHODS: Since the beginning of 2005, a model of axial flow blood pump was designed in the 14th Institute of China-Aerospace Science and Industry Corporation base on decreasing shearing force and circulating dead bands. In the process, CAD and CFD were used to generate the geometrical data document of pump's structure, which included the figures of pump's body, shape and number of impeller's vanes, the structure and position of the guide vanes, and the size of impeller's screw-pitch. And then, NC machine tool was used for shaping. Finally, axial-flow blood pump was fixed on artificial ventricular assist device which was provided by Department of Biomedical Engineering, Beijing Anzhen Hospital of Capital University of Medical Sciences. The pump's hemodynamic output was 5 L/min and the average pressure was 13.3 kPa under the mixture of glycerin and water and fresh anticoagulation goat blood. The samples were collected at every one half hour during pumps being pumping for 4 hours. According to testing pressure output of blood pump, normalized index of hemolysis (NIH) was used to reflect content of free hemoglobin in plasma, observe thrombogenesis in pump and verify pump's hemodynamic output and vascular damaging degree.RESULTS: Shaped axial-flow blood pump included body, impeller, guide vanes, ceramic shaft bearing, export and import. The volume was 63 mL. Experimental results in vitro indicated that when the rotation speed of blood pump was 10 000 r/min, its pressure and flow output were 21.01 kPa and 6.0 L/min. The hemodynamic output might satisfy for left ventricular assistance. Surface temperature did not change obviously during successive rotation. The calculation indicated that most parts in blood pump showed a streaming flow. The mean NIH was (0.047±0.017) g/100 L, which was less than that of previous pumps; while, thrombogenesis was not observed in blood pump.CONCLUSTON: Axial-flow blood pump designed by using CAD and CFD can not only satisfy for the hemodynamics of a left ventricular assistant devices, but also the blood damage is milder than previous pumps. Therefore, axial-flow blood pump improves blood compatibility.
ABSTRACT
Hemolysis caused by blood pumps is a very important characteristic. In vitro hemolysis test circuits were constructed to operate the model I centrifugal pump, the model II axial flow pump, the magnetic coupling pump and the model I & II spiral mixed pump. The output of all pumps was set at flow 5 L/min, an average pressure of 100 mmHg. Experiments were conducted for 4 hours at room temperature(25 degrees C) with 500 ml fresh anticoagulant sheep blood. Blood samples were taken for plasma free-hemoglobin measurement, and the change in temperature at the pump outlet port was measured during the experiment. Calculate the normalized index of hemolysis (NIH). The results showed that there was no relationship either between the pump rotational speed and the NIH in five types of blood pumps, or between change in temperature at the pump outlet port and NIH. The dynamic fluid field caused by pump design and structure could be the main cause of blood damage.