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Biomedical subjects

T Akutsu

Publications and source records attributed to T Akutsu.

At least 91 records · Page 5Linked to original sources
PubMed1985

Antithrombogenic elastomers: novel anticoagulant/complement inhibitor-controlled release systems.

We have introduced novel synthetic anticoagulant and complement inhibitors for controlled release systems with high biocompatibility. These drugs were molecularly designed for extremely high biospecific inhibition, are readily soluble in polar organic solvents, such that they have versatile applications in commonly used hydrophilic polymeric systems via an easily attainable one-step co-casting technique at a given amount of loading. Another characteristic feature of the controlled release system is that both release rate and duration are controlled by the material, formulation and fabrication variables. These are easily manipulated by the hydrophilicity of polymers, amount of loading and film thickness. The drug-impregnated system may generate a new dimension in the formulation of controlled release biocompatibility.

Animals↗
PubMed1985

[Artificial organs and surgery. Present status and problems. The artificial heart].

Various means to assist the failing heart surgically will include, according to the order of simplicity and readiness of their application, intraaortic balloon pumping (IABP), veno-arterial bypass with oxygenator (VAB), and ventricular assist device (VAD). However, when the severity of the cardiac failure is beyond the capacity of these assist devices, the use of the total heart replacement device (total artificial heart-TAH) will be the final solution. Increase of the cardiac output by the use of IABP is limited being less than 1.0l/min. Results of VAB has been poor. The number of VAD cases reported to date is over 200 in the world. Thirty-six percent of them were successfully weaned, but only 15.8% of the patients were discharged. Among 14 cases experienced in Japan, 2 patients survived longer than one month following the VAD removal. The recent overall world result has been steadily improving. The TAH has been used in five patients in the world. In the first two patients TAH was used as a temporary relief assuming heart transplantation later, which was proposed by Cooley as two-staged heart replacement in 1969. In the recent three TAH was applied being expressly stated as a permanent device. Timely judgment and decision when to apply are most important.

Adult↗
PubMed1984

A new test circulatory system for research in cardiovascular engineering.

A new test circulatory system (TCS) has been developed for the in vitro testing of artificial hearts (AH) and for research in cardiovascular engineering, when connected to an AH that mimics the natural heart. The TCS is controlled by five variables whereby the slopes of the systemic and pulmonary venous return curves and the mean circulatory pressure can be fixed. It allows us to observe the mutual influence between TCS and AH characteristics and particularly the blood volume distribution, the pressure distribution, and the flowrates in steady-state conditions and (in the near future) also in dynamic conditions. A steady-state mathematical analysis describing the TCS is reported. Numerical results for the human circulatory system at different levels of activity and in physiologic conditions are shown. A first prototype of the TCS has been working for more than one year. The experimental results are in agreement with the mathematical analysis.

Biomedical Engineering↗
PubMed1984

Circulation control of experimental and clinical profound left ventricular failures by automatic left ventricular assist system.

It is desirable that circulation control of the patient using a left ventricular assist device (LVAD) should be achieved appropriately and safely. We have developed an automatic LVAD system, which can maintain the normal circulation irrespective of the severity of heart failure and can restore the failing heart by decreasing the bypass flow (BF) through the LVAD as the heart recovers. The main part of the control-drive unit is an automatic level control (ALC) system for left atrial pressure (LAP) and total flow (TF). Profound left ventricular failure (LVF) was made by complete interception of blood supply to the extent of 50% (5 goats) and 70% (5 goats) of the LV free wall. The air-driven diaphragm-type LVAD was implanted between LA and aorta. At the beginning of LVAD pumping, BF tended to be very high to keep LAP at the preset level (0-5 mmHg) and to maintain TF at somewhat higher level (120-140 ml/kg/min). The recovering heart was able to decrease LAP gradually. Since the LAP was set at a certain level, the ALC of LAP decreased BF to maintain LAP at the preset level. During the recovering stage from LVF, preset level of LAP was gradually raised while checking the pulmonary function. When natural heart output exceeded 100 ml/kg/min, LVAD was removed. The 50% LVF group recovered between 17 hours and 3 days, and 70% LVF group between 6th and 16th postoperative day. This LVAD system was then applied to the postoperative profound LVF in a MVR patient whose entire circulation was maintained normal during 14 day pumping. The failed heart gradually recovered and the pump was successfully removed. We consider that the decompression of LV will prevent overextension of impaired myocardium and simultaneously accelerate the solid scar formation. And gradual increase of LV work will promote the compensation ability of the residual myocardium. Continuous LVAD assistance can therefore earn time for the impaired myocardium to recover while maintaining normal circulation.

Adult↗