As part of the work to develop safer soft polymeric materials for medical use ethylene-vinyl acetate copolymers (EVA) were evaluated by physico-chemical and biological tests. Test materials were extracted in distilled water at 37°, 70° or 100°C. The extracts obtained were submitted to determining the amount of potassium permanganate-reducing substance, and the absorbance of ultraviolet absorption at 220mμ. Hemolytic activity was studied in two ways by exposing canine red blood cell to plastic surface, and to the extract that was prepared by extraction of test material in physiological saline solution. EVA showed very low level of teachable ingredients and hemolysis compared with Tygon. Antithrombogenicity of EVA was similar to that of silicone rubber. EVA was implanted subcutaneously in a dog for one year. Tensile strength and infrared absorption spectrum of the implanted film were practically unchanged. These results suggest that EVA is feasible as a safer soft material in biomedical applications.

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An analysis of the circulatory equilibrium with natural and artificial heart including the afterload effects on cardiac output was proposed as an extension of the Guyton's theory not including the afterload effects, in which the equilibrium condition of circulation was obtained by equating cardiac output and venous return curves.
The results of this analysis showed that the venous pressure and cardiac output were given by equating the effective cardiac output curve, which was obtained as the points of intersection of the afterload characteristic curves and a peripheral conductance curve, and a venous return curve corresponding to a peripheral conductance. Then arterial pressure was given as a point of intersection of a peripheral conductance curve and the cardiac output obtained above. The circulatory autoregulation with applying an artificial heart to circulatory system was also analysed graphycally. Generally, the cardiac output sensitivity of an artificial heart to venous pressure changes was less greater than that of the natural heart, therefore the circulatory equilibrium during an artificial heart pumping was physiologically different from the natural heart. Farthermore, the resistance of the outflow cannula caused a depressive effect on cardiac output curve and an increased effect on venous pressure.

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Kidney function during total artificial heart pumping renal function of calves implanted with total cardiac prosthesis seems adequately to maintaine with proper amount of urine production and plasma metabolite level. However, as survival time is prolonged, it becomes evident that renal function of some of these animals is not normal. In many of our experimental cases, accumulation of body water occurs and increases with the extension of the pumping period. Increase in plasma metabolite level becomes apparent later toward the end of experiments. These are found to be associated with deterioration of the glomerular function, while tubular function as measured by extraction ratio of filtered Na is generally well maintained, even at the termination of experiments. This type of renal function deterioration is not seen in the animals in which sudden cessation of the experiments due to artificial heart breakage or driving system failure is obliged. Therefore, it is considered to be caused by gradually decreased renal perfusion due to decreased cardiac output with artificial heart.

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A new assisted artificial liver with compulsory electrodialysis was developed to remove rapidly the toxic substances, especially of ammonia or lower fatty acid, which is considered as one of pathogenesis of hepatic coma. An assisted artificial liver devised by us consists of both electrodialyzer and metabolic perfusion circuit. The membranes of CMV and AMV as blood dialyzer were used and electrified between them. By reforming these membranes, blood dialysis could be applied to both ACC and AC method. The effects on blood dialysis were quantitatively analysed by in vitro and in vivo experiments. With increasing electrical current and effective dialysis area, the rapidity and efficiency of blood ammonia removal was increased, which was analytical showed by graphycal representation. Furthermore hemolysis and denaturation of protein by the electrodialyzer was quantitatively discussed with liver failure dogs made by portacaval shunt subsequently with ligation of hepatic artery. From these results it was discussed that the AC method was available in practical use. Electrodialytic disposal of amino acids or amines in addition to ammonia is now investigated and reported in detail hereafter.

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The average lifespan of our 69 removed pulse generators in the last three years was only 20.3 months. About half of those 69 units were replaced by battery exhaustion and by elective (prophylactic) reasons. Another half of pacemakers had to be removed from patients by various pacemaker complications excluding battery problems. Our data suggested that tha diminution of various pacemaker complications was mandatory for the prolongation of the average lifespan of pacemakers. Twenty-two of the 69 units were replaced by the battery depletion. The failed implant lifetimes of these 22 were 29.8 months in average. The lifespan of present mercury battened pacemakers seemed to be about three years on fortunate occasions.

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There are two conventional modes of electrode insertion for implantation of pacemakers, myocardial and transvenous catheter modes. At the present time, the latter is widely used because of its easier operative procedure and a lesser incidence of surgical burdens and complications. However, the problems of the dislodgement of electrodes and many other accidents lie in patients with catheter electrodes. Therefore, we have, as a rule, implanted myocardial electrodes to avoid the problems described above. To manage postoperative troubles accompanied with myocardial implantation, we administered adequate doses of corticosteroids and antibiotics after operation, with patients enjoying uneventful postoperative courses. We would recommend the mode of myocardial implantation rather than transvenous catheter implantation because of the following reasons: 1) no troublesome complications are associated with former mode, such as dislodgement of electrodes and cardiac perforation, 2) the postoperative untoward reactions accompanied with myocardial implantation are well managed by combination of enough corticosteroids and antibiotics.

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There has not been a simple parameter by which hemodialysis treatment can be measured. Dialysis hours on the machine per treatment or per week is usually difined, but this method is thought to be unsatisfactory. Because important factors are not taken into account if dialysis is expressed in terms of time alone. Hemodialyses of equal length are not necessarily equally effective, since the rates of blood flow, which significantly affects the efficiency of dialysis, are often changed during a treatment and from one treatment to another.
We use the total dialyzed blood volume in liters as a quantitative parameter for the evaluation and prescription of dialysis. The total dialyzed blood volume can be easily measured by counting the revolution of the blood pump which was equipped by a digital revolution counter. Total dialyzed blood volume in liter is correlated with the body weight of the patient in kilogram. We chose a total dialyzed blood volume in liter, which is 117% of body weight in kilogram. The corresponding number of revolutions can be easily determined with relation to either liters of total dialyzed blood volume or kilograms of body weight. The therapeutic effect of dialysis can be maintained on an optimal and even level in 17 chronic hemodialysis patients.

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