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Biomedical subjects

N K Zimin

Publications and source records attributed to N K Zimin.

At least 19 recordsLinked to original sources
PubMed1992

[Morphohistochemical characteristics of heart myocardiocytes under profound donor hypothermia].

Hearts of 52 pups were studied histochemically and electron-microscopically at various stages of total-body hypothermia. The dependence of the myocardiocyte metabolic alterations on the factors acting in the myocardium during different stages of hypothermia and during subsequent warming is shown. The vitality of the cooled heart is largely determined by retaining not only of its function, but by its anatomo-physiological links with the organism. The method of the profound hypothermia of the donor organism is, according to the authors, one of the ways to sustain the donor heart vitality before transplantation.

Animals↗
PubMed1991

Present and future of the artificial heart driving system.

The totally artificial heart (TAH) is now in development in two trends. First, there is the development of a bridge system for temporary support of cardiac function. The TAH with the extracorporeal pneumatic driving system Sinus-IS is more efficient and safer. Parallel with this, a portable pneumatic driving system has been developed. That can be considered a stage in the development of the second trend: a totally implantable TAH. This article reviews problems of building of the Micron energy system to be used in implantable TAH designs.

Animals↗
PubMed1991

Centrifugal blood pumps--a brief analysis: development of new designs.

Analysis of 350 different sources of information from leading countries of the world enabled us to determine the availability of 20 different designs of centrifugal and rotary blood pumps. Most of them are for extracorporeal applications with radial pumping wheels of disc or vane type. The prospect of improving these designs was suggested by a combination of these two types. Five new designs based on the Biomedicus have been produced. Basic calculations are given for one of these with respect to limitations for shear stresses. It is proposed that the suggested designs will allow reductions in thrombosis and haemolysis which are the main problems for these pump designs.

Animals↗
PubMed1990

[The first clinical experience with heart transplantation].

The article analyses the first clinical experience in orthotopic allotransplantation of the heart at the Scientific Research Institute of Transplantology and Artificial Organs, USSR Ministry of Health, in the period from October, 1986 to July, 1989 (26 transplantations of the heart and one two-stage transplantation of the heart with the use of "Poisk-10M" artificial heart for 3.5 days in the first stage). Eleven patients are alive. Follow-up periods: maximum over 2.5 years, minimum 3 months. Sixteen patients died in different periods (up to 12 months). Three-component therapy (cyclosporine A, methylprednisolone, azathioprine) was applied for immunosuppression. The authors analyse the problems of the selection of potential recipients (indications and contraindications) and donor, the optimum surgical techniques, complications of immunosuppressive therapy, and infectious complications. The first clinical experience in two-stage transplantation of the heart is analysed. The first experience in transplantation of the heart in patients allows the conclusion that the use of this method for the management of the terminal stage of congestive cardiac insufficiency is a reality.

Adult↗
PubMed1987

Use of an ellipsoid artificial heart.

Experiments with the Poisk model of an ellipsoid artificial heart are reported. With a modified model of the diaphragm type made from polyurethane, calves survived for a mean of 55 days, with a maximum survival of 3 months. With adequate anticoagulation therapy, no thrombogenesis was observed in the blood chamber (except for the inlet valves); a low level of plasma hemolysis was observed postoperatively. Good correlation was demonstrated between the stroke volume and left and right atrial pressures. Changes in the blood coagulation indices are reported. Implantation of a clinical variant of this prosthesis into human cadavers demonstrated no difficulties in placing the heart in the pericardial cavity. Developmental efforts are continuing.

Animals↗
PubMed1986

Some aspects of experimental heart transplantation.

In 144 experiments carried out on dogs, the possibility was proved to use for the recipient's protection during transplantation either deep immersion hypothermia or total artificial circulation without it being filled with the donor's blood. In order to maintain cardiac activity after clinical death of a non-heparinized organism for the purpose of later heart transplantation the authors propose to use the direct mechanical cardiac massage (DMCM) which makes possible not only to restore adequate pulsating blood flow in the dead body but also to assess after restoration of the heart's pump function the suitability of using it for transplantation. Functional adaptation of a transplanted heart proceeds in 3 stages: pronounced heart failure (5-15 min), functional heart failure (4-6 hours), stabilization of cardiac activity (2-3 days). Implantation of a second heart in experimental left ventricular failure of the recipient helped to achieve an effective and prolonged reduction of excessive functional overload of the affected heart.

Adaptation, Physiological↗
PubMed1983

In vitro assessment of the hemocompatible properties of polymers.

Based on the available data in the literature and personal results, a system of in vitro tests, consisting of two levels of selection, was proposed for assessment of hemocompatible properties of polymers. The first level consists of rapid methods for preliminary assessment (clotting time, hemolytic activity of the sample, and number of adhesive platelets). The second level involves methods for final selection and consists of measurement of the kinetics of the initial stages of adsorption of albumin, the degree of activation of the complement system, the intensity of radical oxidation of the lipid fraction of the blood, and the degree of platelet spreading. Comparative experimental assessment of these methods was conducted with a number of polymers and revealed the confidence limits for the application of each test and suggested quantitative criteria for selection.

Biocompatible Materials↗
PubMed1983

Biomedical aspects of cardiac massage in experiments and clinical practice.

Despite current successes in modern cardiology and heart surgery, the problem of restoring and maintaining cardiac function in cases of sudden arrest or ventricular insufficiency is still urgent. Different methods of mechanically assisting the heart and replacing its pumping function exist, and direct mechanical cardiac massage (DMCM) is one of the more important. Experimental results with dogs and calves on 2- to 4-h DMCM, cardiac massage lasting for up to 48 h, subsequent restoration of cardiac activity, and cardiac massage during experimentally induced myocardial infarction permitted clinical application in patients with myocardial infarction complicated by ventricular fibrillation. DMCM also permits extension of the possibilities of obtaining and transplanting donor organs. It is one of the variants for solving the problem of total and partial replacement of the pump function of the heart, and now makes it possible to solve some important problems in transplantation and cardiac resuscitation.

Animals↗
PubMed1980

[Thromboresistant properties of polyelectrolyte complexes based on weak polyelectrolytes].

Thrombogenic resistant polyelectrolyte compositions were obtained on the basis of weak polyelectrolytes used in different quantity proportions. The investigations were performed in vitro on rabbit blood and in vivo on 21 dogs and 5 calves in the conditions of acute and chronic experiments. The optimal compositions of polymers were selected for the implantation. The appropriate polyelectrolyte compositions on the basis of weak polyelectrolytes, and polymers modified by polyacryl acid with polyethylene piperazine (1:1, 2:1, 3:1), were found to be thrombogenic resistant and did not cause any significant blood cells damage. The investigations performed the possibility for their practical application.

Animals↗
PubMed1979

[Maintenance of the circulation and the restoration of heart function in the donor body by means of direct mechanical heart massage for subsequent transplantation (an experimental study)].

The possibility of maintenance of circulation and subsequent restoration of the function of the heart in the organism of the donor, after 10-minute arrest of circulation, for transplantation of the heart was investigated. Study of the hemodynamic, biochemical, metabolic, and structural changes in the myocardium after 2-hour mechanical massage without and with pharmacological protection of the myocardium (glucose--insulin--potassium, hydrocortisone, dipyridamole), without and with restoration of cardiac activity in the organism of the donor and the recipient after transplantation of the second heart by the method suggested by Moory et al. in artificially created left ventricular insufficiency showed that direct mechanical massage of the heart may be used for its short-term preservation in the donor organism.

Animals↗
PubMed1977

[Experimental autotransplantation of the heart].

The paper analyses the results of 15 heart autotransplantations undertaken in puppies under deep hypothermia. The employed method of autotransplantation without division of the atrial septum is described. The characteristics of a adaptation of the cardiac autotransplant in the recipient body are presented along with the principles of correction of the changes observed in the early postoperative period.

Animals↗
PubMedDate not supplied

[Centrifugal blood pumps (new possibilities of design improvement)].

Based on an analysis of 300 world information sources, 19 types of centrifugal blood pumps were ascertained. Five new designs suggested have an idea in common: combination of the inlet of the disk pump and of the outlet of the impeller pump. This allows uniting the merits of the above pumps and excluding their shortcomings. The designs suggested make it possible to solve the two basic problems: hemolysis and thrombogenesis inside the pumps. The use of the pumps designed on such a basis will afford a simple and reliable approach to heart function replacement.

Animals↗
PubMedDate not supplied

[Centrifugal pumps for forcing blood: technical aspects (review)].

The paper is concerned with one of the trends in the design of outfits for blood forcing, namely with centrifugal pumps. Advantages and shortcomings of such pumps are assessed as compared to roller and other type pumps for blood. Unsolved problems are outlined. Based on a comparative analysis, six main designs are distinguished, the principles of the action, the scope of uses and characteristics are depicted. The conclusion is made that this type of pumps holds promise for the use in cardiosurgical clinics of the USSR.

Equipment Design↗
PubMedDate not supplied

[A portable, movable pneumatic drive for an artificial heart with an autonomous electrochemical source of energy].

The authors have designed a pneumatic drive, which differs from the known ones in that it contains two electromagnetic two-linear and two-positioned air distributors while the motor operates in the mode excluding the change of its axis direction. This affords using a standard crank mechanism as a transformer of rotary motion to translational motion and reducing several times the power consumed. Besides, the two-linear and two-positioned air distributors allow a possibility of exercising a separate control over the time of the systole-diastole phases of the left and right ventricles. In this case both ventricles can work at 100% filling whereby maintaining the capacity of the artificial heart without additional energy consumption.

Electric Power Supplies↗