ARTIFICIAL CIRCULATION

From Big Medical Encyclopedia

ARTIFICIAL CIRCULATION (synonym: extracorporal blood circulation, artificial perfusion) — a way of maintenance of a blood-groove in an organism, separate body or the certain area in the artificial way.

For the first time a thought of an opportunity «to keep in a live state any part of a human body» with the help And. to. the fr. physiologist Legallua stated (Page J. J. Legallois, 1812). Further many physiologists tried to carry out this idea in an experiment on the isolated bodies of animals or the person.

Sh. Broun-Sekar (1858) for the first time managed to recover signs of life of the head of a dog which is dissected away from a trunk at a transmission through her vessels of an arterial blood by means of the syringe. Martin and Gopkins (H. Martin, J. Hopkins, 1881), Frederik (L. A. Fredericq, 1890), E. Starling (1898), etc. carried out perfusion of separate bodies by means of cross circulation or the isolated heart-lung preparation. Various options I. to. usually provide at the same time artificial oxygenation of the blood coming from an organism to the device and returned in it. And. to. it can be carried out as by means of heart and lungs of other organism, and by means of special mechanical devices — cardiopulmonary bypasses (agrarian and industrial complex).

The first primitive device for And. to., turning on mechanical devices for oxygenation and forcing of blood, it was created by Frey and Gruber (M. Frey, M. Gruber, 1885).

The largest contribution to development And. to. there were basic researches of S. S. Bryukhonenko and his followers of S. I. Chechulin, H. N. Terebinsky and V. D. Yankovsky. These researches begun at the beginning of the 20th 20 century were fundamental in the solution of problems I. to., connected with designing of the device «heart — lungs», development of ways of stabilization of Coagulant system of blood, and also use And. to. for revival of the whole organism and a heart surgery. The created S. S. Bryukhonenko and S. I. Chechulin the device called by them «avtozhektor» (see Bryukhonenko an avtozhektor), and its further modifications actually were the first devices suitable for implementation full And. to. in an experiment on animals. They served as a prototype of the whole series of domestic devices I. to., found further broad application in clinic.

The first open heart operations using And. to. in an experiment H are carried out. N. Terebinsky in 1930, and in clinic — in 1953, the Gibbon (J. N of Gibbon) in the USA.

In the USSR pioneers of development of a method I. to. in clinic there were collectives directed by H. M. Amosov, A. A. Vishnevsky, A. N. Bakulev, S. A. Kolesnikov, P. A. Kupriyanov, B. V. Petrovsky, etc. The first successful operation with And. to. in the USSR it is executed by A. A. Vishnevsky in 1957.

Practical application in clinic was found by three main methods I. to.: the general And. to., regional And. to. and various options artificial circulatory support (see).

The general And. to. — the most widespread method. It provides full replacement of pumping function of heart and gas exchange function of lungs with mechanical devices by short time. The main aspect of its use — a heart surgery.

Regional And. to. — perfusion of separate body or the area of an organism which is temporarily isolated from other vascular system. The hl is applied. obr. in oncology and purulent surgery for leading of big concentration of medicinal substances directly to the center of defeat. One of options regional And. to. — coronary and carotid perfusion — is used by nek-ry authors for a heart surgery. In combination with a moderate hypothermia (see. Hypothermia artificial ) it allows to carry out heart lasting up to 30 min. operations. And. to. for a heart surgery was widely adopted. In many clinics of the world practically all heart operations are carried out in conditions And. to.

Cardiopulmonary bypasses

And. to. it is carried out by means of the perfused device (AIK).

To modern AIK for the general And. to. impose the following main requirements: 1) the device shall support reliably throughout all perfusion the set minute volume of blood circulation in an organism (about 4 — 5 l for the adult patient) and the set temperature of the circulating blood; 2) the oxygenator shall provide adequate to arterialization) blood: saturation by its oxygen not below than to 95% and maintenance of pCO2 at the level of 35 — 45 mm of mercury.; 3) the volume of filling of AIK shall be small (no more than 3 l at perfusion of adult patients); 4) the device shall be supplied with the device for return to a circulator contour of the blood streaming from the opened cardial cavities and the damaged fabrics; 5) the injury of blood in the device shall be minimum (no more than 40 mg of % of free hemoglobin of plasma in the first hour of perfusion); 6) fiziol, the AIK block shall be produced from non-toxic material, chemically inert in relation to blood; its design shall provide a possibility of cleaning and sterilization in the conditions of clinic.

Fig. 1. Scheme of the cardiopulmonary bypass: 1 — a coronary suction; 2 — the manometer; 3 — the filter trap; 4 — the heat exchanger; 5 — the arterial pump; 6 — the oxygenator; 7 — a decanter.

Any AIK consists of two blocks: physiological and mechanical. To fiziol, to the block all details adjoining to blood belong. Main nodes fiziol. the block the oxygenator, or «an artificial lung», and the arterial pump, or «artificial heart» are. Here different tanks and hoses by means of which nodes fiziol, the block connect among themselves, forming extracorporal system — a so-called circulator contour of the device belong, on Krom blood moves to time And. to. In the figure 1 the typical scheme AIK, used in a heart surgery for the general is submitted And. to.

A venous blood from vessels of the patient with drift is transfused in the oxygenator, the located lower than the level of the operating table where it is saturated with oxygen, exempted from excess of carbonic acid and further is forced by the arterial pump in a blood channel of the patient.

Before getting to a blood channel of the patient blood passes through the heat exchanger (the device for maintenance of necessary temperature of blood) and the filter trap protecting from hit in a vascular bed of the patient of emboluses (the trombotichesky mass, pieces of calcium from valves and vials of gas). Blood from the opened cardial cavities and the damaged fabrics is evacuated in AIK by means of the special device — a so-called coronary suction.

Oxygenators are divided into two main classes: oxygenators in which gas exchange is carried out at direct contact of oxygen with blood, and oxygenators where blood and oxygen are divided by a gas-permeable membrane.

Two types enter the first class: bubble and film. The second class received the name of membrane oxygenators.

Bolshaya Square of contact of oxygen with blood in bubble oxygenators is reached by supply of gaseous oxygen directly in blood.

Gas exchange of oxygen with blood in film oxygenators is reached thanks to creation of a pellicle of blood on any firm basis placed in the atmosphere of oxygen. In membrane oxygenators gas exchange between blood and oxygen is carried out through a gas-permeable membrane (see. Oxygenators ).

Pumps. The design and production of the devices performing delivery function of heart meet less difficulties, than a solution of the problem of artificial arterialization of blood. The pumps having productivity approximately equal to the minute volume of heart in rest i.e. about 5 l/min are created, however at their designing the specific requirements imposed to «artificial heart» are considered.

Practical application in AIK was found by two main classes of pumps: valve and valveless.

Fig. 2. Schemes of valve (1 and 2) and valveless (3 and 4) pumps: 1 — the membrane pump; 2 — the chamber pump; 3 — the roller pump; 4 — the finger-type pump; and and — consecutive provisions of mobile parts (the direction of movement is specified by black shooters) the pump at various moments of its running cycle; the direction of the movement of blood is specified by white shooters.
Fig. 3. Schemes of heat exchangers: above — a tubular heat exchanger: blood proceeds through a number of the parallel tubes placed in the cylindrical capacity through which water circulates; below — the slot-hole «heat exchanger a pipe in a pipe»: blood proceeds through a narrow crack between internal and outside pipes (with double walls) on which water circulates; the direction of the movement of blood is specified by white shooters, waters — dotted shooters.

Valve pumps are subdivided into pumps with internal and outside valves. The most typical representatives of valve pumps are membrane and chamber pumps (fig. 2, 1 and 2).

Valveless pumps work by the principle of expression of blood from an elastic tube by rolling on it of a roller or alternate crossclamping her mechanical «fingers» (roller and finger-type pumps, fig. 2, 3 and 4). During the designing of pumps for AIK consider rheological properties of blood (viscosity, speed of a blood flow on highways of the device, etc.) to minimize traumatization of its cells.

Additional nodes. Additional nodes fiziol, the AIK block are the heat exchanger and system of a coronary suction. The first is necessary for maintenance of the necessary temperature of blood and consequently, and body temperatures of the patient in the course And. to. In AIK two types of heat exchangers found application: tubular and slot-hole which design is given in the figure 3. Cooling or warming up of blood is reached due to change of the water temperature washing the heat exchanger.

The system of a coronary suction returns blood in a circulator contour of the device. Depending on a design of AIK it is carried out with the help of either a vacuum suction, or one or several roller pumps.

To auxiliary nodes fiziol, the block different vessels for the reserve and removed with a suction blood, filters traps for air traps, etc. belong.

The case of the device with drives of pumps and mobile parts of the oxygenator, and also the measuring equipment for determination of productivity of pumps, a consumption of gases, temperatures of blood, etc. belongs to the AIK mechanical block. As an energy source electricity or compressed gas is used. An obligatory element of the mechanical block is the emergency hand gear.

Fig. 4. AIK-5M cardiopulmonary bypass.
Fig. 5. The cardiopulmonary bypass of firm of Sarns with the physiological block disposable of firm Travenol (USA).

All devices I. to., used in clinic, represent a combination of the AIK various elements (the tab.; fig. 4 and 5). Devices for partial perfusion differ from devices for the general perfusion of the adult in smaller dimensions and productivity (to 1 — 1,5 l/min). In them there is no device for suction of blood.

A special type of the equipment in a set of AIK-5M and IS of L-4 — the device for coronary perfusion. It is intended for protection of a myocardium against a hypoxia during open operations on valves of an aorta when the natural blood stream on vessels of heart stops. The device for coronary perfusion consists of two pumps of small productivity (to 500 ml/min.) allowing to carry out separate perfusion of both coronary arteries with rate of volume flow and under pressure, corresponding to that under natural conditions. The device for coronary perfusion has no own oxygenator and is a prefix to the device for the general perfusion.

The general tendency in further improvement of devices is more and more broad use in them fiziol, the block disposable, microporous filters in the arterial line and transition to membrane oxygenators.

Characteristic of some devices I. to. it is given in the table.

A technique and the equipment of artificial circulation

Indications to And. to. constantly extend in connection with improvement of the equipment and a technique of perfusion. The AIK large cardiac centers use at all endocardiac operations, reconstructive operations on coronary vessels and many other operative measures on large main vessels.


Preparation of AIK. A necessary condition of use of the perfused equipment — absolute purity of its surfaces adjoining to blood. It is reached by processing of all elements fiziol, the block detergents (see) or the concentrated solutions of alkalis with the subsequent washing by water. Only after it the device is assembled and sterilized.

Depending on material, from to-rogo separate elements fiziol are produced, the block, use either autoclaving, or a cold way of sterilization by means of a germicidal gas (ethylene oxide) or solution (Diocidum, beta propiolactone). Abroad ready for application sterile depyrogenized perfused systems disposable were widely adopted.

Completely collected AIK is filled with blood or a blood substitute and at a certain stage of operation connected to the patient.

Connection of AIK. The scheme and technology of connection of AIK can be various depending on operational access and a type of pathology of heart (or a vessel). For forcing of blood use one of femoral or ileal arteries from where retrogradno blood comes to a ventral and chest aorta more often, then in its arch, passing in the vessels feeding a brain and heart (coronary vessels). Sometimes arterializirovanny blood is forced through a cannula in the ascending department of an aorta. Drainage of venous system is made or by means of two plastic catheters entered into both venas cava through the right auricle or by means of one catheter entered into the right auricle or a ventricle. A venous blood comes to the AIK oxygenator where it is saturated with oxygen, and the pump AIK goes to arterial system of the patient. Both of these manipulations produce after introduction to blood of sick heparin in a dose 2 — 3 mg on 1 kg of body weight. For bigger safety of the patient cannulate of arterial system shall precede catheterization of a venous bed.

Carrying out artificial circulation is begun with turning on of the arterial pump on small productivity and a simultaneous release of clamps from the venous line of the device. However at the same time full outflow of blood from an organism of the patient is not allowed. Synchronously increasing pump delivery and size of a venous inflow, within 1 — 2 min. lead up rate of volume flow of perfusion to settlement, edges shall make 2,2 — 2,4 l/min on 1 sq.m of a body surface.

Further the size of rate of volume flow and a duty of the oxygenator are supported, being guided by criteria of adequacy of perfusion. As those, in addition to standard in a wedge, anesthesiology of indicators (the ABP, venous pressure), oxygenation or pO2 of an arterial and venous blood on the basis of which can be calculated the general oxygen consumption, percent of its utilization etc. and indicators of an acid-base state define (pH, pCO2, SB, BE, etc.).

Duration I.k. depends on the nature of pathology and fluctuates of several minutes (sewing up of defect of an interatrial partition, elimination of the isolated valve stenosis of a pulmonary trunk) till 3 and more o'clock (simultaneous prosthetics of several valves of heart). Always it is necessary to aim at the minimum terms of perfusion and to limit its use only to those stages of operation which cannot be executed without And. to.

Transition to natural blood circulation is begun with the gradual or single-step termination of intake of blood in the device with simultaneous reduction of productivity of the arterial pump.

Forcing of blood in an artery is completely stopped on reaching the optimum volume of the circulating blood in a vascular bed of the patient what judge but the size of the central venous pressure, edge shall make 150 — 180 mm w.g. at this moment.

In case of long And. to. (St. 1 hour) it is reasonable to combine it with the general cooling of an organism (see. Hypothermia artificial ) due to giving in the heat exchanger of a cold water (so-called hypothermal perfusion). The hypothermia is followed by decrease in need of an organism for oxygen that gives the chance to reduce rate of volume flow of perfusion, and thereby and an injury of uniform elements of blood. Extent of cooling can be various and is defined by conditions of operation. The moderate hypothermia is in most cases sufficient (temperature in a gullet not lower than 28 °). The deep hypothermia to 15 — 10 ° is applied extremely seldom, in case of need temporary dead stop of blood circulation (correction of rare anomalies of development of heart, debugging in the perfused equipment).

During the carrying out And. to. widely apply a method of so-called managed hemodilutions (see), i.e. dilution of the circulating blood blood-substituting liquids (see). As the last use various low-molecular solutions of electrolytes, sugars or proteins. It, in addition to reduction of amount of donor blood, significantly improves fabric a blood stream due to increase in rheological properties of blood and reduces traumatization of erythrocytes. Degree of the applied hemodilution depends on the oxygen capacity of blood of sick (hemoglobin content) and its specific features. The zone of optimum rheological effect of cultivation, by data A. N. Filatova, F. V. Ballyuzek (1972), is in range of 20 — 30%.

Pathological physiology

And. to. puts an organism of the patient in unusual, phylogenetic unprecedented conditions. Such «abnormalities» in an organism as a retrograde blood flow in an aorta, falloff of pressure in cardial cavities or their full zapustevaniye, switching off of a small circle from blood circulation, existence in blood of products of destruction of its uniform elements and fabrics, cause patol. reactions of an organism to perfusion.

During operation with And. to. the state coming to it a cut is observed arises at massive damage of fabrics in combination with big blood loss, i.e. to to hemorrhagic shock (see). Anesthesia is not able to make an organism completely insensitive to influences And. to., especially to its humoral component.

Changes of a hemodynamics are most characteristic. Since the minute volume of blood circulation during perfusion is supported by operation of the arterial pump, these changes are caused by hl. obr. shifts in system of vessels.

For And. to. decrease in the general peripheric resistance and the ABP is characteristic. At the same time resistance in various sites of vascular system changes differently, causing redistribution of a blood-groove in an organism; at the same time two tendencies are observed: so-called protective redistribution and centralization of blood circulation.

Protective redistribution consists in relative increase in a blood-groove in internal vitals due to its reduction in superficial bodies and fabrics. This phenomenon is expressed to those more, than rate of volume flow of perfusion is lower. In usual conditions such reaction of vessels is characteristic of hemorrhagic shock, at Krom it has really protective character. In conditions And. to. it hinders the achievement of an optimum blood-groove in peripheral fabrics even at high rate of volume flow of perfusion. Centralization of blood circulation consists in decrease in a fabric blood-groove against the background of rather invariable and even the increased blood-groove in large vessels. To deterioration in a fabric blood-groove in time And. to. also increased tendency of erythrocytes to intravascular aggregation promotes (see. Aggregation of erythrocytes ).

Hypothermal perfusion doubly influences a hemodynamics. On the one hand, cold braking of the vasculomotor center, causing the general vazodilatation, interferes with development of a phenomenon of «protective» redistribution of a blood-groove. At the same time decrease in temperature of blood increases its viscosity and tendency of erythrocytes to aggregation. It leads to deterioration microcirculation (see) and further centralization of blood circulation.

Are a direct consequence of the described hemodynamic changes quite often observable in time And. to. a hypoxia of fabrics (see. Hypoxia ) and signs of a metabolic acidosis in blood (see. Acidosis ). Pathogenetic prevention of these undesirable phenomena shall be directed first of all to improvement of microcirculation, elimination of phenomena of «protective» redistribution and centralization of blood circulation. The most effective measures in this respect — the managed hemodilutions and artificial hypotonia. Apply ganglioblokator to this purpose (arfonad, gigroniya) which have the powerful decentralizing influence on blood circulation and completely eliminate a phenomenon of «protective» redistribution of a blood-groove (see. Hypotonia artificial ). And. to., carried out against the background of an artificial vazoplegiya, is followed by a hypoxia of fabrics and a metabolic acidosis less often.

Complications

the Vascular embolism of a brain, coronary vessels and vessels of other vitals can be caused by gas, trombotichesky mass, particles of calcium, drops of fat, etc. Prevention of similar complications comes down to a complex of the consecutive events directed to deaerating and various particles from cameras of heart and filling with their blood which are held before inclusion of heart in blood circulation. Tactics of the perfuziolog managing work of the system draining the left cameras of heart is of great importance for prevention of an air embolism during this period. Reduction of its productivity and full switching off can be undertaken only according to instructions of the surgeon or anesthesiologist. As a universal measure of prevention of an air embolism many surgeons apply supply of carbon dioxide gas in an operational wound before sealing of cardial cavities. Carbon dioxide gas is well dissolved in liquids and quicker, than air, leaves a gleam of a vessel.

Hit of vials of oxygen from the oxygenator to the arterial line of the device — the second possible reason of a gas embolism. Due to the improvement of the perfused equipment and increase in its reliability this complication meets seldom.

Use microporous arterial filters disposable to the prevention of an embolism. These filters are installed in the AIK arterial line. They are capable to detain particles up to 40 microns in size.

The vascular embolism of a brain can have various symptoms (from insignificant nevrol, signs to a deep brain coma) and quite often comes to an end with the death of the patient. Therapy of this complication shall be directed first of all to prevention and treatment of wet brain (see. Swelled also swelling of a brain ).

One of the most effective to lay down. actions at a gas embolism the immediate room of the patient in the camera with the increased barometric pressure is (see. Barotherapy , Hyperbaric oxygenation ).

The hypoxia of vitals can be a consequence of two main reasons: insufficient productivity of the oxygenator or arterial pump and disturbance of microcirculation. A wedge, a symptom of a hypoxia is increase of a metabolic acidosis during perfusion. Effects of a hypoxia happen various and depend on its degree and duration.

At the modern equipment I. to. this complication threatens with death only at a sharp deviation of perfusion from its normal current. Failure of the perfused equipment and too big shunting of the blood forced in a circulatory bed of the patient via the struck aortal valve or a bronchial anastomosis can be the reasons. Falloff of a blood-groove in an organism can lead in this case to irreversible changes in vitals. Prevention of post-hypoxemic wet brain in time And. to. immediate cooling of the forced blood by means of the heat exchanger is. In case of need it is reasonable to continue a hypothermia of a brain also in the post-perfused period.

Hematologic complications can be caused by group or proteinaceous incompatibility of blood of the donor and patient, reaction of the patient to a massive hemotransfusion of the citrated blood raised by an injury of blood in the device, disturbance of a blood coagulation and water and electrolytic balance. A wedge, manifestations of these complications are various. Reaction of the patient to alien blood is shown by the whole complex of the symptoms which are often combined under the name «syndrome of homologous blood».

Prevention of the complications connected with introduction to an organism of stored blood shall be directed first of all to reduction of its quantity. The crucial role is played use of devices with a small volume of filling and use of hemodilution here. Degree of traumatization of blood depends on a number of factors: duration and way of preservation of donor blood, perfection of the perfused equipment and technique of its use, duration of perfusion. Modern devices I. to. injure blood a little, and the size of hemolysis during the work with them usually does not exceed 30 — 40 mg of % of free hemoglobin of plasma at perfusion lasting up to 1 hour that, as a rule, is well transferred by patients. It is impossible to plan borders of marginal hemolysis since tolerance to it strongly varies at different groups of patients. It depends on a reference state of its parenchymatous bodies — kidneys, a liver. Various wedge, symptoms of dysfunction of these bodies are more often observed at patients with the acquired heart diseases which are followed by disturbance of blood circulation. Decisive conditions for reduction of extent of hemolysis are hemodilutions and economical use of a coronary suction — the main source of hemolysis.

Disturbance of a blood coagulation after operation with And. to. it is observed quite often. Inadequate neutralization of heparin of protamin sulfate, defibrination of plasma and destruction of thrombocytes in AIK can be its most frequent reasons. Effective measures of fight against this complication are introduction of additional doses of protamin of sulfate under control of repeated titration of blood of the patient, transfusion of fibrinogen and trombotsitny weight.

More rare, but a dangerous complication of operations with And. to. is fibrinolysis (see). Are the main reasons for its emergence a massive hemotransfusion against the background of And. to. Patients with the acquired heart diseases which are followed by functional disturbances of parenchymatous bodies are more predisposed to emergence of a fibrinolysis. Measures of the prevention of a fibrinolysis are preventive introduction to blood to or in time And. to. an epsilon - aminocaproic to - you, failure from transfusion of large amounts of stored blood at the expense of hemodilution, timely correction of a metabolic acidosis. The best results of treatment of the developed fibrinolysis are yielded by use of high doses of Trasylolum. An effective measure of fight against any form of disturbance of a blood coagulation is transfusion of whole donor blood.

The general anesthesia

the General anesthesia at use And. to. has a number of specific features. And. to. causes in an organism a row patofiziol, disturbances that along with surgical intervention (crossclamping of an aorta, the termination of a coronary blood-groove, fibrillation of ventricles of heart, a section and sewing together of a muscle of heart, replacement of valves, correction of endocardiac defects etc.) demands the coordinated work of the surgeon and specialists of other profiles ensuring safety of operation.

For the prevention of negative emotional reactions and disturbances of a homeostasis and compensatory mechanisms of an organism Premedication patients with heart diseases shall have a multicomponent premedication (tranquilizers, antihistaminic drugs, analgetic and vagolytic means). In essence Premedication at heart operations in the conditions of PI. to. does not differ from that at other heart operations.

An introduction anesthesia

there are various ways of introduction to an anesthesia of patients with heart diseases and large vessels. At the same time it is important to observe the following philosophy: a) preservation of optimum parameters of external respiration and hemodynamics during administration of anesthetic and a relaxant; b) use of the minimum doses of anesthetics and optimum doses of relaxants; c) carrying out an intubation against the background of adequate relaxation of muscles and a hyperventilation oxygen; d) bystry establishing artificial ventilation of the lungs with supply of the main anesthetic; e) constant control behind cordial activity and a vascular tone.

For direct introduction of the patient to an anesthesia with identical success barbiturates of ultrashort action in 1% solution, drugs for a neyroleptanalgeziya (Droperidolum and fentanyl), an ataralgeziya (Seduxenum + an analgetic) in the corresponding doses per 1 kg of weight of the patient can be used. It is possible to apply also inhalation anesthetics (Ftorotanum, nitrous oxide, cyclopropane). At small children reasonablly intramusculary (in chamber) to enter Ketaminum (5 mg/kg).

Period of maintenance of an anesthesia. Specifics of operations with artificial circulation dictate need of allocation of three periods of the main anesthesia: 1) preperfused; 2) perfused; 3) post-perfused.

Preperfused period. In this period it is reasonable to allocate three stages: 1) before opening of a pericardium; 2) manipulations on heart and the main vessels; 3) from the moment of introduction of venous cannulas prior to perfusion.

The first stage — an anesthesia does not differ from that at operations on bodies of a chest cavity.

The second stage — disturbances of a hemodynamics owing to a variety of reasons can be observed: restretchings a ranorasshiritel of edges of a wound of a chest wall and reduction of inflow of blood to heart, shifts of heart at manual inspection, various disturbances of a heart rhythm during these manipulations, disturbance of a blood-groove at allocation of venas cava, etc.

The disturbances of a rhythm of cordial activity leading to decrease in the ABP demand the temporary termination of manipulations on heart and vessels and acceptances of necessary measures for improvement of cardiac performance, and in the absence of effect of cardial therapy — an auxiliary cardiac massage and the emergency connection of AIK.

The third stage — the most responsible. With introduction of catheters to venas cava inflow of blood to heart significantly decreases and there are phenomena of stagnation in venous system. Stagnation in system of an upper vena cava is especially dangerous, developing of hypostasis of a brain can be result to-rogo.

For the prevention of this complication it is necessary to observe the following sequence of connection of AIK: arterial highway, lower vena cava, upper vena cava.

During this period it is reasonable to pass to manual artificial ventilation of the lungs, creating if necessary positive pressure both on a breath, and on an exhalation, during filling of catheters etc.

For maintenance of an anesthesia in the preperfused period apply nitrous oxide with oxygen in combination with drugs to a neyroleptanalgeziya Ftorotanum (0,5%) or metoksiflurany (0,3 — 0,5%). From muscle relaxants give preference to drugs of not depolarizing type of action (tubocurarine) in usual dosages.

The perfused period

Feature of this period is that the narcotic state and a relaxation should be supported by administration of the corresponding drugs directly in the AIK oxygenator. Because lungs of the patient do not participate in gas exchange, inflate them nitrous oxide with oxygen (4:1) under pressure of 10 — 12 cm w.g. in order to avoid development of atelectases.

The post-perfused period

enters tasks of the anesthesiologist maintenance of an adequate hemodynamics, edges after correction of defect and shutdown of AIK is normalized not at once. For maintenance of a hemodynamics Novodrinum, a glucagon, a hydrocortisone, strophanthin, calcium chloride, etc. are entered. Artificial ventilation of the lungs is carried out to a complete recovery of independent breath, in need of a current of several days.

The prolonged ventilation of the lungs allows to stabilize gas exchange at optimum level and on this background to korrigirovat other disturbances. In particular, the hemodynamics, an acid-base state give in to regulation easier, temperature is normalized. The last occurs without shiver and, therefore, without increase in the oxygen consumption so undesirable in the direct postoperative period when mechanisms of compensation quite often are on the verge of failure. Parallel to actions for maintenance of a hemodynamics the anesthesiologist should recover normal coagulability of blood, neutralizing heparin of protamin sulfate and entering sodium bicarbonate or Trisaminum at acidosis.

The anesthesiologist shall pay special attention to adequate compensation of blood loss and normalization of volume of the circulating blood.

CHARACTERISTIC OF SOME CARDIOPULMONARY BYPASSES



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V. P. Osipov; A. A. Bunyatyan (anest.).

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