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Biomedical subjects

E Hennig

Publications and source records attributed to E Hennig.

At least 19 recordsLinked to original sources
PubMed1992

Recovery of end-organ failure during mechanical circulatory support.

To evaluate organ recovery during mechanical assistance, respiratory, hepatic and renal function parameters of 40 patients who underwent bridge-to-transplant procedures were reviewed retrospectively. Mechanical circulatory support was indicated if the hemodynamic and clinical status deteriorated despite pharmacotherapy with catecholamines, vasodilators, and intravenous use of the phosphodiesterase inhibitor enoximone. Sequelae of cardiogenic shock such as renal, hepatic and respiratory insufficiency were not considered a contraindication for mechanical support. The analysis of preimplant data such as serum creatinine, liver enzymes and pulmonary gas exchange did not identify any predictive indicator of irreversible organ damage. Functional recovery of preexisting respiratory, hepatic and renal dysfunction was found in 91%, 90%, and 85%, respectively. Subsequent transplantation, however, was affected by the number of failing organs prior to mechanical support. Of 17 patients with isolated organ failure prior to assist, 14 (82%) were transplanted. By contrast, 9 (75%) of 12 with combined failure of two organs, and only 6 (54%) of 11 patients with clinical patterns of three failing organ systems received transplants. In all patients who underwent successful transplantation, transplantability was associated with rapid organ recovery within 10 to 15 days after initiating mechanical assistance.

Adolescent↗
PubMed1992

[Measuring model for intraoperative determination of vascular resistance in crural vascular surgery].

The measurement of the vascular outflow resistance during reconstructive vascular operations was applied since 1989 on 45 subjects with reliable results. This measurement is an aid for decision of additional treatment increasing the outflow, like a jump- or sequential bypass or a pharmacological therapy. The principle of measurement is based on the injection of a known volume of saline in the vessel and the integration of the intravascular pressure during this injection. In the prototype used, the pressure integration was performed by means of a modified analog/digital conversion method, hereby the results could be achieved directly as numerical values. Further an automatic, microcomputer based implementation of the outflow resistance measurement, showed remarkable improvements of accuracy in laboratory tests.

Foot↗
PubMed1992

[Effect of vascular resistance on results in crural artery surgery].

Between February 1989 and June 1991 the peripheral outflow resistance was measured at 45 patients during infragenual bypass surgery. In order to find out whether there is a correlation between successful bypass grafting and measured outflow resistance, all patients were controlled regularly. There was a significant difference in mean resistance between those grafts remaining patent and those that failed. 8 out of 11 bypasses, that failed up to one month after operation, had measured peripheral resistance higher than 1.1 mmHg x min/ml. 12 out of 15 bypass grafts remained patent for more than one month and had an outflow resistance less than 0.55 mmHg x min/ml. There is no definite correlation between a measured outflow resistance from 0.55 to 1.1 mmHg x min/ml because of the low number of patients in this group. The purpose of resistance measurement during peripheral vascular surgery was to determine a final value for a decision, if additional surgical or non surgical treatment for a better runoff is necessary. In our study this value is 1.1 mmHg x min/ml. Additional treatments are the peripheral AV-fistula and a jump- or sequential-graft. Another possibility is the intra- and postoperative application of Prostaglandin, which is in an experimental study in our clinic.

Aged↗
PubMed1992

[Physical and physiological principles of calculating vascular resistance in cardiovascular circulation].

After reconstructive vascular surgery the quality of perfusion and the risk of failure can be predicted, if the distal outflow resistance of the graft is known. The laws of the hydrodynamics for the calculation of flow resistance in tubes are discussed with respect to their validity in the circulatory system. Because of great differences between the physiological realities and the physical assumption, and problems in monitoring some of the parameters of the equations, the calculation of the physiological vascular resistance according to the a.m. laws is not possible. With "Ohms law" of the hydrodynamic the calculation of the outflow resistance distal of a graft is possible if the flow through the bypass and the pressure losses in the outflow bed are known. Easier to perform is the measurement of the pressure-time integral generated by the injection of a standardized volume into the graft and the calculation of the outflow resistance with the help of a microprocessor.

Arterial Occlusive Diseases↗
PubMed1991

Dose-dependent differences in the profile of mutations induced by an ultimate carcinogen from benzo[a]pyrene.

Mutations in the coding region of the hypoxanthine (guanine) phosphoribosyltransferase (HPRT) gene of Chinese hamster V-79 cells were examined after exposure of the cells to a high cytotoxic dose (0.48 microM; 35% survival) and a low noncytotoxic dose (0.04 microM; 100% survival) of the ultimate carcinogen (+)-7R,8S-dihydroxy-9S,10R-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene [(+)-BPDE]. Independent 8-azaguanine-resistant colonies were isolated and cDNAs were prepared by reverse transcription. The coding region of the cDNA of the HPRT gene was amplified by the polymerase chain reaction and sequenced. An examination of the DNA base sequence changes induced by different doses of (+)-BPDE demonstrated that the high dose of (+)-BPDE caused base substitution mutations almost exclusively at G.C base pairs whereas the low dose of (+)-BPDE caused mutations at both G.C and A.T base pairs. Thus, use of a low dose of (+)-BPDE allowed the detection of mutations (at A.T base pairs) that were not readily observed with a high dose of (+)-BPDE. The data also suggest that the low dose of (+)-BPDE may have caused a different profile of base substitutions at G.C base pairs and exon deletions than the high dose. The results indicate dose-dependent differences in the profile of mutations for an ultimate carcinogen.

7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide↗
PubMed1991

Mechanical left ventricular support as a bridge to cardiac transplantation in childhood.

The mechanical extrathoracic "Berlin Heart" cardiac assist device was used for left ventricular support in an 8-year-old child of 27 kg body weight. Terminal left ventricular failure and life-threatening ventricular tachyarrhythmias in this child were sequelae of coarctation of the aorta, aortic stenosis and resultant severe left ventricular dilatation, hypokinesia and fibrosis. With the assist device, cardiogenic shock could be reversed. The child was extubated and mobilized during an 8-day waiting period for orthotopic heart transplantation. This case illustrates that the use of ventricular assist devices can be successfully extended to children and may be advantageous compared to other techniques of mechanical circulatory support, such as balloon pumping or extracorporeal membrane oxygenation.

Age Factors↗
PubMed1991

Patient selection for mechanical circulatory support as a bridge to cardiac transplantation.

Between 7/87 and 9/90 thirty-four patients underwent total artificial heart (Berlin Heart) (n = 2) or biventricular assist device (Berlin Heart) (n = 32) implantation as a bridge to cardiac transplantation. The time of mechanical support ranged from 2 to 60 days, for a mean of 19.2 days. Twenty-three patients received heart transplants, with 74% 30-day survival and 52% long-term survival. Implantation of a mechanical support system became indicated in those patients whose hemodynamic and clinical condition deteriorated despite treatment with enoximone in addition to maximal sympathomimetic medication. The strategy to administer enoximone routinely was the result of a prospective study on 24 pretransplant patients in whom enoximone therapy reduced the need for mechanical assistance by 62%. At the time of device implantation shock-related organ impairment such as cerebral, renal, hepatic, and respiratory dysfunction was present in 62% of patients. In addition, 7 patients had pneumonia. During mechanical support complete recovery of end-organ failure and resolution of pneumonia was observed in the majority of patients. The results indicate that end-organ dysfunction per se should not be considered a contraindication to mechanical circulatory support as a bridge to cardiac transplantation. However, further clinical investigations are needed to identify predictive indicators of irreversible organ damage.

Adult↗
PubMed1990

[Pressure distribution pattern in relation to foot structure during muscular active and passive load impacts].

A piezoelectric pressure distribution platform (1000 elements) was employed, to investigate the mechanical behavior of three different foot structures. Ten male subjects in each of the foot groups Cavus, Rectus, and Planus performed voluntarily controlled jumps with one leg onto the pressure distribution platform. Using a trap door arrangement, the subjects fell in a second set of experiments unexpectedly onto the sensor matrix. In order to exclude a voluntary foot muscle response, the time duration of falling was restricted by choosing a falling height of only 20 cm. Comparing the data from both impact conditions the influence of active foot muscle involvement could be investigated. The analysis of the temporal pressure pattern, the local peak pressures and the regional impulses permitted an insight into the mechanical characteristics of the different foot structures.

Adolescent↗
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↗
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

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↗
PubMed1988

Preliminary results with an apico-aortic valved conduit (AAVC) using polyurethane and aortic allograft valves.

Stenosis of the left ventricular outflow tract is one of the most frequent congenital cardiac anomalies in dogs. The subvalvular stenosis is described as a ring of fibrous tissue located in the left ventricular outflow tract immediately below the aortic valve. The best method of surgical treatment in dogs seems to be relief of the aortic obstruction with a ventricular aortic prosthesis. A new trileaflet valve manufactured out of polyurethane has been developed. For the conduit a woven Dacron graft has been used. In 5 male dogs a valved conduit was implanted between the apex of the left ventricle and the aorta thoracica without using hypothermia and/or cardiopulmonary bypass. Four dogs survived the surgical procedure and showed no clinical symptoms postoperatively. Blood flow through the conduit was demonstrated postoperatively by angiocardiography for a maximum of 22 days, the longest surviving time being 8 weeks. Trials for the replacement of the artificial valve in the conduit by a canine aortic allograft valve are in progress. Studies were done with the cryopreservation of fresh aortic valves. Sterilization, cryoconservation, and storage methods for the allograft are described.

Animals↗