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Biomedical subjects

H Harasaki

Publications and source records attributed to H Harasaki.

At least 73 records · Page 4Linked to original sources
PubMed1983

Experimental results for chronic left ventricular assist and total artificial heart development.

After more than 20 years of research on the artificial heart, it is now accepted that the pneumatically actuated total artificial heart can maintain near-normal physiology in experimental animals for several months. Such systems are clinically acceptable for short-term application (a few months) in patients waiting for a suitable heart transplant. However, realistically, a cardiac prosthesis that has the capability of being totally implantable for over 2 years must be available. Based on this premise, our group initiated the development of a mechanically actuated total artificial heart, capable of coupling with either a thermal or electrical actuation system. Since 1977, under the National Institutes of Health chronic left ventricular assist program, we have used two different pusher-plate pumps and electrical systems. Taking advantage of technology generated in these programs, we began developing a prosthesis to replace the total cardiac function. This paper is a summary of both the chronic left ventricular assist and total artificial heart development progress in this laboratory.

Animals↗
PubMed1983

Infection in artificial blood pump implantation.

Infection has been observed in artificial heart experimentation to be of early onset and generally within the first 2 postoperative weeks. The organisms most often detected in blood cultures were Pseudomonas aeruginosa, Enterobacter cloacae, E. coli and Enterococcus, all of which are intestinal species. Contamination is thus thought to be the most plausible cause of perioperative infection. Absolute sterility must be maintained in animal care areas and blood access to these animals is to be minimized. Although prompt selection of a proper antibiotic therapy is essential, the eradication of infection maintains a poor prognosis. The time course of fibrinogen levels is a reliable index to determine the onset of infection.

Animals↗
PubMed1982

Hexsyn trileaflet valve: application to temporary blood pumps.

A trileaflet valve, compression molded of Hexsyn rubber, was evaluated as a component in temporary blood pumps. A pair of valves was integrated into an LVAD which was tested in vitro and in vivo. The valve's hemodynamic performance was satisfactory and the blood compatibility was excellent in a three-week, in vivo experiment conducted to demonstrate performance in a short-term application. Hexsyn, which has excellent properties and produces high quality, complex components with ease of fabrication, offers a potential for low-cost blood pump valves.

Alkenes↗
PubMed1982

Volume compensation for left ventricle assist systems (LVAS): 18 month in vivo evaluation.

The smooth surface cycled chambers, both Biomer and silicone rubber, developed thick tissue capsules and exhibited persistent active tissue reactions at the diaphragm-capsule interface. Textured surface chambers (dacron velour), both the cycled and control, developed a thin, stable capsule, with no active tissue reaction. Textured surface chambers have been explanted and examined after 210 and 494 days. One experiment is continuing, approaching 2 yrs in vivo with good performance. Although the number of textured surface compliance chamber studies as yet is limited, the dramatic improvement in performance and tissue response between the smooth and textured surface studies demonstrates the biological feasibility of this method of variable volume compensation for use in completely intracorporeal LVAS.

Biocompatible Materials↗
PubMed1981

Pusher-plate type TAH system operated in the left and right free-running variable rate mode.

A TAH system utilizing two pusher-plate type pumps was developed and tested in two calves for 45 and 108 days with excellent results. A Hall effect sensor was utilized to operate each pump with a full stroke at variable rates (VR); each pump was then allowed to run independently at different rates depending on its own preload and afterload. With this system, the animals' atrial pressures were kept to near-normal levels (less than 10 mmHg). However, significant differences in the left and right pump flows were observed (left higher than right) and they ranged from 5 to 30% of the left flow with a mean of 15%. These flow differences may be due to the bronchial circulation and related shunts. Right pump flows averaged 70 to 95 ml/min-kg and circulating blood volume ranged from 67 to 95 ml/kg. When various control modes including fixed rate and master-slave type simultaneously or alternatively ejecting VR modes were applied in the same animals and both pump flows were forced to be equal, unphysiological atrial pressures resulted. This result indicates that perhaps left and right flow differences are necessary physiological conditions to regulate the atrial pressures within normal ranges. Metabolic data also indicated that under simultaneously and alternately ejecting modes, A-V O2 content differences were increased due to decreased right pump flow as compared with those of the free-running VR mode. The left and right free-running VR mode of operation imposed minimal constraints on the animals' cardiovascular system and therefore yielded excellent hemodynamic and metabolic results.

Animals↗
PubMed1981

Axial changes of blood and plasma flow, pressure, and cellular deposition in capillary plasma filters.

The ability to separate plasma on-line from whole blood by membranes has generated interest in applying this process to source plasma collection and to the therapeutic treatment of various disease states. The availability of capillary membrane devices in particular has prompted investigations in these areas. The deposition of blood cellular elements has required the investigation of those parameters related to fluid and mass flux. Analytical solutions relating blood flow rate, filtration rate, and pressure and deposition with respect to axial distance have been obtained. Comparison of these solutions with preliminary experimental results have been made. Results indicate that the deposition parameter versus distance from the inlet is a very sensitive function of capillary membrane properties and operating conditions. Plasma fluxes are also highly dependent on blood, membrane, and filter properties and operating conditions.

Blood↗
PubMed1981

Promising results with a new textured surface intrathoracic variable volume device for LVAS.

The smooth surface cycled chambers, both Biomer and silicone rubber, developed thick tissue capsules and exhibited persistent acute tissue reaction at the interface. The silicone rubber noncycled chambers either developed no capsule or a very thin capsule without the acute inflammation observed with the cycled side. The dacron velour surface chambers, both the cycled and noncycled, developed a thin, stable capsule, with no acute inflammation. The cycled dacron velour surface chambers have achieved almost one year with acceptable performance and are continuing at this time. These results with the textured surface compliance chambers compare favorably with the smooth surface series. Although the number of studies as yet is limited, the performance of the textured series compliance chambers shows promise for the application of the compliance chamber for use with totally implantable blood pump systems.

Animals↗