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Biomedical subjects

H Harasaki

Publications and source records attributed to H Harasaki.

At least 145 records · Page 8Linked to original sources
PubMedDate not supplied

Systemic and local effects of heat dissipation in the thermally powered LVAS.

A thermally powered left ventricular assist system (LVAS) requires 20 W of heat dissipation either to the blood or to the surrounding tissues, such as the lung subcutaneous tissues. Postoperative systemic and local effects of heat dissipation were studied in 5 thermally powered LVASs and 2 heated blood pumps implanted in calves, and compared with 10 pneumatically powered left ventricular assist devices (LVADs). Postoperative mean temperatures of the heat dissipation group were as follows: 1. rectal (RT), 39.1 x 0.4 degrees C (NS versus control); 2. Lung interface, 41.6 +/- 0.6 degrees C (P less than 0.01 versus RT); 3. tissue interface, 40.2 +/- 1.2 degrees C (P less than 0.01 versus RT); and 4. blood, 39.2 +/- 0.8 degrees C (NS versus RT). There was no significant postoperative change in heart rate, respiratory rate, or rectal temperature between the two groups. No difference was shown between the two groups in hematologic parameters, plasma free hemoglobin, liver and renal function, fibrinogen levels, or coagulation processes at the same postoperative time. Heat dissipation to the pump-blood interface promoted a thinner neointima when compared with the nonheated surface. Angioneogenesis was observed in the tissue capsule adjacent to the heat dissipating surface. These results indicated that the thermal LVAS induced no deleterious local or systemic effects on recipient animals.

Air↗
PubMedDate not supplied

Renal effects of a pyridoxalated-hemoglobin-polyoxyethylene conjugate solution as a blood substitute in exchange transfusions.

With PHP as an oxygen carrier, histologic studies in ET showed changes of renal tubular epithelial cells at 2 weeks post ET, with normal structure by 3-12 months post ET. The renal functional effects of PHP were evaluated by ET (30%, N = 3; 50%, N = 1; 80%, N = 3) in seven healthy mongrel dogs. Blood, urine, and renal biopsy specimens were taken pre ET and at 0, 1, and 2 days, 2, 4, and 6 weeks, and 3, and 6 months post ET. Data were compared to modified criteria of acute tubular necrosis. All dogs tolerated the procedure well and survived for 1 year. Urine output was normal with elevation during the first 2 days in the 50 and 80% ET, followed by stable output by 2 weeks, ranging from 12 to 60 ml/kg/day. Blood urea nitrogen (BUN) and serum creatinine (SCr) were normal. BUN/SCr was normal. The urine to plasma osmolality ratios were 2.6 to 8.3 (normal greater than 1), and fractional percent excretions of sodium (FES) were stable throughout. No existence of broad granular pigmented casts (BGPC) in urine sediment were noted. Renal histologic evaluation of vacuolization in the renal tubules were seen to be dose-dependent and transient, with normal histology by 3-6 months post ET. Dose-dependent vacuole formation observed in the early weeks post ET with PHP showed no renal functional changes. Based upon the modified criteria for acute tubular necrosis, no histologic abnormalities were noted.

Animals↗
PubMedDate not supplied

Flow visualization in an artificial heart using diffuse and planar laser lighting.

The purpose of the study was to characterize flow properties within a clinical pusher plate type artificial heart. Dual camera video tape and synchronized still photographs were used to study flow patterns. Diffused light and a planar laser source provided illumination. The laser light was turned into a plane of light with a thickness varying from 0.1 to 10 mm, and magnesium oxide and Amberlite particles were used as tracers. Qualitative and quantitative analyses were performed by the examination and digitization of flow patterns. Inflow, outflow, pneumatic drive and after-load pressure, diaphragm motion, cardiac output, and heart rate were measured and recorded. An electrical circuit was developed to synchronize pump diaphragm motion with captured images of flow trajectories. Trajectories were then digitized, and velocities, turbulence, and shear stresses were calculated. As the result of these experiments, disturbed, recirculating, and stagnation zones were identified and global and local turbulence values were determined. Simultaneous turbulence, stasis, recirculation, and laminar flow patterns were observed during most phases of the pumping cycle. Velocities obtained varied from 2 cm/sec to 145 cm/sec; total local shear stresses of 12 to 897 dynes/cm2 were seen.

Blood Flow Velocity↗
PubMedDate not supplied

A titanium-nickel alloy intravascular endoprosthesis. In vitro studies.

In order to evaluate the implantation technique and reliability of conversion at different temperatures, a miniaturized intravascular endoprosthesis (IVEP) composed of thermal shape-memory effect TiNi alloy was delivered via a catheter into a 37 degrees C water mock circulatory loop (MCL) with a flow of 100 ml/min. The 2.5 mm diameter wire coil IVEP was torsion reduced to 1.4 mm, mounted on a modified balloon angioplasty catheter, and delivered into the MCL. Shape-memory conversion was activated thermally by injecting normal saline (3, 5, or 10 ml) at 45 degrees, 50 degrees, 55 degrees, 60 degrees, 65 degrees, or 70 degrees C, while the local temperature (Tp) at the endoprosthesis site was monitored by a thermocouple. Inconsistent completed conversions of the IVEP were produced by injecting 10 ml of 60 degrees C, or 5 ml of 65 degrees C normal saline, which raised the Tp to 45 degrees to 53 degrees C. Complete conversion of the IVEP to 2.5 mm was produced consistently by injecting 10 ml of 65 degrees C or 5 ml of 70 degrees C saline, which raised Tp to 55 degrees C for less than 1 sec. This moderate Tp (55 degrees C) for such a short duration was shown to be a reliable method for remote conversion of the IVEP after catheter delivery. Knowledge of the minimum temperature and volume for consistent, complete conversion of the IVEP has permitted simple, safe conversion during in vivo studies. Delivery after balloon angioplasty is envisioned to either treat acute dissection with occlusion or to prevent chronic restenosis, in order to further improve the safety and efficacy of balloon angioplasty procedures.

Alloys↗
PubMedDate not supplied

Hemolysis. A comparative study of four nonpulsatile pumps.

Hemolysis is one of the important performance parameters of blood pumps. However, comparisons of published data are compromised by the different test methods used. This article reports the results obtained when testing four nonpulsatile blood pumps (Roller pump, Biopump Model 600, Biopump BP-80, Hemadyne pump) in the identical test circuit under the same hemodynamic conditions. A closed test circuit was composed of a flexible bag reservoir and two short tubes for connection to the pump head. The priming volume was 1 L, and the total surface area was 950 cm2. Fresh blood from a fasted calf was directly primed into the circuit and maintained at 37 degrees C. It was pumped at 6 L/min for 12 hr against a 100 mmHg afterload. The hemolysis index (HI), defined as grams of hemoglobin released per 100 L pumped, was calculated from a curve fit to the hourly data. Each pump was tested five times. The mean HI obtained ranged from 0.0467 for the roller pump to 0.0076 for the Biopump BP-80. There was no statistically significant difference among the three centrifugal pumps tested.

Animals↗
PubMedDate not supplied

Selective removal of high level cryoglobulins (CG) and immune complexes (IC) by a large pore membrane.

The investigated membranes having a pore size of 3 micron or less can retain over 95% of cryoprecipitable proteins and immune complexes with nearly complete passage of other plasma proteins at 4 degrees C. Based on this result, the G-3 module consisting of V-3000 membrane was chosen for further study. The G-3 module (0.148 m2 of surface area) processed a 10 times higher plasma volume per unit surface area with higher selectivity than the Asahi Plasmaflo AP 06M. Separation efficiency of cryoprecipitable proteins and immune complexes in cryoglobulinemic plasmas by cryofiltration at 4 degrees C is related to the composition of the cryoprecipitable protein; three of four plasmas contained cryoprecipitable proteins that were removable by cryofiltration. Cryoprecipitation was too slow in one of four plasmas. For this plasma SDS PAGE showed its light chain to be of higher molecular weight than other plasmas. Two of four plasmas had elevated amounts of IC that were removed by cryofiltration.

Adult↗
PubMedDate not supplied

In vivo evaluation of a permanently implantable thermal ventricular assist system.

The System 7 pump/actuator/engine combination has demonstrated biologic compatibility and physiologic effectiveness and responsiveness in five TVAS in vivo studies. The recent 75-day implant supports the feasibility of extended reliability of the system components. Postoperative system maintenance was necessary only because of the nonhermetic design of System 7. However, the ability to pump 11 l/min at 120 beats/min, synchronize at beat rates of 144 beats/min, and pump against mean arterial pressures of more than 150 mmHg while maintaining hematologic and biochemical values within physiologic range sets a very optimistic stage for System 8 hardware. A System 8 concept is shown in Figure 14. The System 8 hardware will include a thermal salt package capable of providing completely untethered circulatory support for a nominal 8-h period. Recharge will be accomplished with a transcutaneous transformer in 1 h. Thermal management problems become minimal, with an average energy input of 15.8 W (peak of 24.9 W). The human preclinical testing of System 8 will start in 1988.

Animals↗
PubMedDate not supplied

Surface structure of the human cardiac valve. A comparative study of normal and diseased valves.

This article reports the surface structure of the endothelial cells covering the cardiac valves and their changes in chronic inactive rheumatic valvulitis and bacterial endocarditis. The endocardial surface of the normal cardiac valve was covered by a layer of endothelial cells, each of which was recognized because of the presence of centrally located nuclear bulge and marginal folds at the cell boundaries. In the cardiac valves affected by chronic rheumatic valvulitis, the endothelial layer denuded extensively, even in the regions where only slight thickening was noticed in the intravalvular tissues. As compared to the inflow side of the valve, denudation of the endothelial layer was more conspicuous on the outflow side. There was no morphological difference between the two hemodynamically different conditions, i.e. stenosis and regurgitation. In the cardiac valves affected by bacterial endocarditis, in contrast, the destruction of the endothelial layer was preferentially observed along the closing margins of the valve, and in the region of calcification and vegetation. These findings are compatible to the interpretation that differences in morphological changes of the endothelial layer in these two acquired valvular diseases may reflect the differences of their pathogeneses. The present study thus suggest an importance of endothelial cell in elucidating the pathogenesis of acquired valvular diseases.

Aortic Valve↗
PubMedDate not supplied

Effect of respiration on the arterial pressure wave in calves with nonpulsatile biventricular bypass.

The possibility of idioperipheral pulsation in calves with chronic nonpulsatile biventricular bypass has been previously reported. To test the hypothesis that both spontaneous respiration and mechanical ventilation are the cause of pulsation in the arterial pressure recording in calves with nonpulsatile biventricular bypass, two protocols were used to generate data. Both right and left ventricles were bypassed using two centrifugal pumps followed by electrical fibrillation in seven calves. In protocol 1, the spontaneous respiratory rate was increased in awake calves by carbon dioxide gas inhalation. In protocol 2, the animals were anesthetized and intubated to control ventilation, and data were collected as the ventilation rate or tidal volume was changed in a stepwise fashion, as well as when the ventilation was stopped for several seconds. The results of protocol 1 showed good correlation between the arterial pulse rate and spontaneous respiratory rate (Y = 1.03 X, r = 0.822, p < 0.001). The results of protocol 2 showed that the relationship between the ventilation rate and the arterial pulse cycle was identical (Y = X, r = 1.000, p < 0.001), and no pulsation was seen when the ventilator was stopped. The authors conclude that the arterial pulsation observed in calves with nonpulsatile biventricular bypass is caused by respiration.

Animals↗
PubMedDate not supplied

Development of a magnetically operated artificial urethral sphincter. Chronic effects of compression on the skin structure and blood flow.

The artificial urethral sphincter (AUS) has been in clinical use for more than 20 years. Currently available AUS devices, however, are difficult to use and not entirely reliable. A magnetically operated AUS is currently under the development. Although the skin between the magnets will be compressed all day long, little information exists on the effects of chronic pressure on the skin structure and blood flow. In five miniature pigs, two internal magnets and one control metal disk were implanted subcutaneously at three different positions, and external magnets with differing magnetic forces were applied to the skin overlying the internal magnets for six weeks. In four pigs, the skin blood flow was measured by a laser Doppler flow meter applying different pressures. Compression of 10 mmHg preserved normal skin morphology in all but one animal where blood flow had not recovered 2 weeks after surgery. Compression of 20 mmHg for 6 weeks, however, produced pressure ulcers in all five cases (p < 0.05 vs. 10 mmHg group). The skin blood flow declined for pressures exceeding 20 mmHg (0 mmHg: 4.3 +/- 1.2, 10 mmHg: 4.3 +/- 3.3, 20 mmHg: 2.6 +/- 2.7 ml/min/100 g). We concluded that the magnetically operated AUS should use a magnetic coupling with a pressure less than 10 mmHg exerted on the interposing skin.

Animals↗