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Biomedical subjects

E S Bücherl

Publications and source records attributed to E S Bücherl.

At least 19 recordsLinked to original sources
PubMed1999

Proposal of a new electromechanical total artificial heart: the TAH Serpentina.

A new type of energy converter for an electro-mechanical total artificial heart (TAH) based on the principle of a unidirectional moving motor is described. Named the TAH Serpentina, the concept consists of 2 major parts, a pendulum shaped movable element fixed on one side using a joint bearing and a special shaped drum cam. Pusher plates are mounted flexibly to the crossbar of the pendulum. A motor drives the special shaped drum cam linked to the pendulum through a ball bearing. The circular motion of the unidirectional moving brushless DC motor is transferred into the linear motion of the pendulum to drive the pusher plates. Using a crossbar with a variable length, the stroke of the pendulum and therefore the displaced blood volume is alterable. To achieve a variable length, an electric driven screw thread or a hydraulic system is possible. Comparable to the natural heart, cardiac output would be determined by frequency and stroke volume.

Electronics, Medical↗
PubMed1991

[Esophageal diverticula. Clinical aspects and therapy].

18 patients (10 male, 8 female) with an average age of 57 years were operated for diverticula of the esophagus. We found 11 pharyngoesophageal diverticula, 5 parabronchial and 2 epiphrenic diverticula. Major symptoms were dysphagia and regurgitation in pharyngoesophageal diverticula. Dysphagia, substernal pain and hiccough in parabronchial and epiphrenic diverticula. The treatment was resection of diverticula which was combined with myotomy in case of pharyngoesophageal diverticula. 2 patients had severe secondary wound healing. Other postoperative dysfunctions of the esophagus or symptomatic recurrences were not seen.

Aged↗
PubMed1990

[The aorto-coronary bypass in the elderly patient].

In the FRG one person every ten is more than 70-years old; the average life expectancy, often underestimated, is about 11 years for the 70-years old and 6 years for 80-years old. The modern approach to coronary disease has broadened the indications for coronary artery bypass grafting in the elderly. The present report, studying 152 patients more than 70-years old, suggests the usefulness of a myocardial revascularization in the elderly; it remains to define the relative contraindications (renal failure, high LVEDP, valve replacement). However, the symptomatic improvement we could achieve (95.45%) seems to be a good result, considering the low CABG-related postoperative lethality (1.9%). The trend of our results regardless of 5 years survival is also encouraging (85.1%).

Aged↗
PubMed1990

Experience with vascular grafts in total artificial heart replacement.

In total artificial heart replacement the pumps are attached to the vascular system with the help of connectors. These consist of a woven Dacron vessel graft to which a short silastic segment is vulcanized. In 36 calves surviving total artificial heart replacement between one and seven months (average 85 days) the morphological alterations due to interfacial reactions were studied: thrombus formation and neointimal fibrous hyperplasia at the anastomoses. In 15 calves (41.7%) thrombus growth within the outflow tract led to anastomotic stenosis: pulmonary artery 14 (93.3%), aorta-anastomosis 1 (2.8%), both vessels 1 (2.8%), in combination with pannus growth in atrial location 13 (86.7%). In 73.3% the pannus consisted of infected organized thrombus imitating the course of septic vegetative endocarditis. Two calves were reoperated in order to remove the vegetative thrombi, one successfully. In five animals pulmonary stenosis was the main cause of death. The presence and location of excessive tissue growth and thrombus formation within the outflow tract are also inherent to the fluid mechanical design of the valve. Neointimal fibrous hyperplasia at the anastomoses of the grafts seems to be a reparative process started up by platelet-induced subendothelial cell proliferation in response to intimal injuries.

Anastomosis, Surgical↗
PubMed1990

Membranes as substrates for hepatocyte adhesion in liver support bioreactors.

Fourteen membranes out of cellulose (CuprophanR), polyamide and polypropylene were compared in a cytocompatibility test using the cytokinetics and cytomorphology of primary hepatatocytes as parameters. Additionally, the impact of coating the membranes with collagen or fibronectin was investigated. Hepatocytes were not able to attach in acceptable amounts on investigated cellulose membranes. On polyamide and polypropylene membranes a sufficient cell seeding was possible. Coating with collagen or fibronectin improves the attachment and spreading on all membranes. Differences between collagen and fibronectin were detected, observing the morphology of the cells: on collagen, most of the cells spread, whilst on fibronectin, most of the cells spread and flattened polygonally. If the adhesion of hepatocytes prolongs their metabolic function, a large adhesion surface in bioreactors is necessary. To reach a high surface area for cell adhesion in bioreactors one possibility is the use of polyamide and polypropylene membranes.

Animals↗
PubMed1989

The relevance of intraoperative pressure and oxygen saturation monitoring during pulmonary artery banding in infancy.

Different methods have been used to define an effective and tolerable degree of pulmonary artery banding (PAB) intraoperatively. As the hemodynamic response determines the results, a reduction of risk could be expected by evaluating several selected parameters and adjusting the band accordingly. Between 1981 and 1986, PAB was performed in 12 infants, three with complex cardiac lesions and nine with complete atrioventricular canal defects. Pressures in the distal pulmonary artery, in a systemic artery or the aorta, and in a central vein were monitored, and oxygen saturation measurements in both great arteries were taken before, during, and after the procedure. Adequate, complicated, intolerable, and contraindicated constriction were recognized and shown on characteristic pressure traces and oxygen saturation shifts. The measurements provided an indirect but reliable indication of the change in intracardiac shunting, and predicted whether the banding would be hemodynamically tolerated. Postoperatively, ten of the infants improved significantly, especially the seven infants previously in a low cardiac output state. One infant died on the day of surgery from acute right heart failure (8% hospital mortality). The results suggest that hemodynamically controlled PAB is an effective palliative treatment with a lower risk than had been previously reported.

Blood Pressure↗
PubMed1989

Endothelial cell seeding on different polyurethanes.

Six polyurethanes (PUs) were tested with respect to their cytocompatibility. Initial adhesion, initial spreading, and the proliferation of endothelial cells were investigated. All smooth PUs showed similar initial adhesion. Initial spreading was faster on rough PUs. Collagen coating resulted in faster initial adhesion but not better proliferation of endothelial cells.

Animals↗
PubMed1989

Isoelastic polyurethane prosthesis for segmental trachea replacement in beagle dogs.

Porous polyurethane (nonwoven) was used for the development of tracheal prosthesis, which--in a special testing design--was adapted to shape and biomechanic properties of the natural organ. This prosthesis was implanted into 19 beagle dogs using inverted, everted, and end-to-end anastomosis. Insufficiency of the anastomosis or infection was observed in the everted and end-to-end anastomosis, whereas the inverted anastomosis showed complete incorporation into surrounding tissue of the porous prosthesis but was complicated by airway obstruction due to anastomosis granuloma.

Anastomosis, Surgical↗
PubMed1989

Use of hepatocytes in adhesion and suspension cultures for liver support bioreactors.

Hepatocyte cultivation in bioreactors for hybrid liver support systems is possible under two conditions: attached to a substrate like membranes or microcarriers or in suspension culture. To compare the ammonia metabolism of hepatocytes cultivated under these two conditions, cultures of primary seeded rat hepatocytes were cultivated either attached to collagen coated tissue culture plastic or as a suspension culture. During the time course of culture, the ability of hepatocytes to reduce the ammonia content of the medium decreased in both adhesion and suspension cultures, though to different extents. In suspension cultures, ammonia content was reduced from 350 microM to about 100 microM (day 4) and to about 180 microM (day 6). No significant reduction was seen on day 8 of culture. In contrast, hepatocytes attached to collagen coated dishes remained viable and functional for at least 8 days after plating, reducing ammonia content from 350 microM to 70 microM (day 4), 90 microM (day 6) and 180 microM (day 8). The period of useful metabolism of hepatocytes in bioreactors for hybrid liver support systems appears to depend on the culture conditions.

Ammonia↗
PubMed1989

Isolation of vascular endothelial cells for investigations on hybrid prostheses.

Hybrid vascular prostheses are coated with vascular endothelial cells (EC) in an attempt to reduce thrombogenicity through the metabolic activities of living cells. The present studies were planned to develop a standardized method of isolating bovine aortic EC with high yield for studies of endothelial coating of vascular prostheses. The best results were achieved using a combination of incubation with collagenase and mechanically scraping the mobilised cells from the donor vessel. Isolated adult male bovine endothelial cells were identified by the typical "cobble stone" morphology in culture and characterized by factor VIII related antigen immunofluorescence microscopy. The cells were seeded successfully on PTFE vascular prostheses.

Animals↗
PubMed1989

Endothelial cell seeding on PTFE vascular prostheses using a standardized seeding technique.

A standardized method was developed for seeding endothelial cells (EC) in tubular vascular grafts. A rotational cell seeding device for tubular prostheses is presented and parameters influencing the kinetics of cell adhesion (rotation speed, graft diameter, cell suspension level, inoculated cell number) are reported. Seeding EC in 14 mm ID PTFE vascular grafts with rotation rate of 10 rph gave an adhesion rate of 80% in a homogeneous monolayer.

Blood Vessel Prosthesis↗
PubMed1989

Biostability of polyurethanes.

Aside from the medical requirements a material has to fulfill to qualify as biocompatible, for the bioengineer, who is involved in the design, construction and fabrication of prosthetic devices, the mechanical, physical and chemical properties of the material as well as its possible manufacturing procedures and, last but not least, its biostability are of the same importance. In the very aggressive biological environment, the material should behave inertly, showing no surface erosions, molecular chain disruptions, uptake of low molecular weight biological materials, local chemical imbalances, tendency to calcification or negative changes of mechanical properties. With regard to this aspect, different polyurethanes have been evaluated in-vitro and in-vivo as basic materials and already fabricated devices (blood pumps and heart valves). The comparison of the results stresses the necessity of further efforts to achieve a standardized test protocol for the prove of the biostability of polymers, containing appropriate, well-defined in-vitro and in-vivo test methods to establish the necessary data basa for the materials' clinical approval.

Animals↗
PubMed1989

[Heart surgery in terminal kidney failure and dialysis dependent patients. Intraoperative hemofiltration for the prevention of hyperhydration].

12 hemodialysis-dependent patients underwent heart surgery involving cardiopulmonary bypass. Their example outlines the special pre-, intra- and postoperative management in these patients. Intraoperative hemofiltration seems appropriate to prevent fluid overload caused by cardiopulmonary bypass. 3 patients died within the first two weeks after operation. 9 patients are well after 4 to 30 months. The results are compared to the reports found in the literature.

Adult↗
PubMed1988

[Corrosive burns of the upper gastrointestinal tract in adults].

Experience obtained from acid burns in 60 adult patients is reported in this paper. Twelve of them died, while 48 received conservative treatment, and twelve underwent surgery. Attempted suicide accounted for the highest number and severity of those accidental injuries. The therapeutic approach should be chosen on earliest possible endoscopy. Trends towards exploratory laparotomy and blind oesophagus stripping are described, and the problem of conservative therapy is discussed.

Acids↗