DIALYSIS (grech, dialysis decomposition, department) — the method of removal of low-molecular substances from solutions of colloid and high-molecular substances based on property of some membranes to pass low-molecular substances and ions and to detain colloid particles and macromolecules. Is widely applied in experimental and clinical medicine.
The liquid subjected to D. is separated from pure solvent the corresponding membrane, through to-ruyu molecules and ions diffused in solvent and at rather frequent change of solvent almost entirely are removed from the dialyzed liquid. D.'s phenomenon was for the first time described by Graham (T. Graham) in 1862.
As membranes apply natural membranes (a bull or pork bubble, a swimming bubble of fishes) and artificial films from nitrocellulose to D., cellulose acetate, cellophane, a kuprofan, a nefrofan and other materials. Artificial membranes have advantage before natural since they can be prepared with various and well reproduced permeability. At the choice of material for a membrane it is often necessary to take into account a charge of a membrane in this or that solvent which results from dissociation of the substance of a membrane or preferential adsorption on it of ions, or uneven distribution of ions on both sides of a membrane (see. Membrane equilibrium ). Existence of a charge at a membrane can sometimes serve as the reason coagulations (see) at D. of colloid solutions which particles bear the charge opposite on a sign to a charge of a membrane.
There is a big variety of devices for carrying out D. called by dialyzers. All these devices are constructed by the general principle: the dialyzed liquid («internal liquid») is in a vessel, in Krom it is separated from water or other solvent («external liquid») by a membrane, permeable for low-molecular substances and not permeable for colloid particles and macromolecules. D.'s speed increases with increase in a surface of a membrane, with temperature increase, during the stirring of the dialyzed liquid and at increase in a difference of concentration of low-molecular substances between internal and external liquids.
Graham's dialyzer (fig. 1) — a glass or plastic cone, the bottom to-rogo it is tightened by parchment or an animal bubble. The dialyzer with the dialyzed liquid is immersed in the vessel filled with solvent (often a dist, water). Low-molecular substances diffuse through a membrane in solvent and are removed from the dialyzed liquid. In Graham D. dialyzers lasts for weeks and it is accompanied by a big consumption of external liquid. It is convenient to of small amounts of liquid to carry out in sacks from the collodion or cellophane attached to a funnel with a short and wide throat (fig. 2).
Zhigmondi's dialyzers used earlier to laboratory researches — Geyera, Gutbir are replaced with dialyzers in which use semipermeable membranes in the form of sheets, hoses and capillaries (see. Artificial kidney ). Exists apprx. 100 various models of dialyzers. If the dialyzed liquid does not change during the heating, then for D.'s acceleration conduct during the heating.
For D.'s acceleration carry out in electric field. D.'s process happening at the same time is called by electro-dialysis, and by the devices used to this purpose — electrodialyzers. The dialyzed liquid is placed in the average cell between dializatsionny membranes. In side cameras there is a solvent (dispersion medium) in which electrodes are shipped. During the imposing on electrodes of constant potential difference ions of low-molecular substances from the average camera are transferred to side cameras, and molecules of nonelectrolytes are removed by means of electroosmosis (see).
Apply in the following cases. 1. For establishment of existence of colloids and high-molecular substances in liquids. 2. For purification of colloid solutions and solutions of high-molecular substances (e.g., proteins) from impurity of low-molecular substances. 3. For preparation of a number of medicines. 4. For definition of concentration of the low-molecular substances which are in colloid solution in the free, not connected with a colloid state. Such definitions make by means of compensation D., the essence to-rogo is that liquid in the dialyzer is washed away not by pure solvent (e.g., water), and solutions with various concentration of the defined substance. E.g., the free sugar in blood serum which is not connected by serum proteins is defined by D. by serums against isotonic solution of sodium chloride, to Krom add various amounts of sugar. Concentration of sugar in salt solution does not change at D. only in that case when it is equal to concentration of free sugar in serum. During the definition of concentration of free electrolytes by compensation D. in colloid solutions it is necessary to consider uneven distribution of electrolyte on both sides of a membrane owing to establishment membrane equilibrium (see). 5. For extraction of low-molecular substances from biological liquids. So, for example, J. J. Abel with sotr. (1913) applied to extraction of low-molecular substances from the circulating animal D.' blood, called them vividiffusion. In the figure 3 the scheme of the dialyzer for vividiffusion is given. In the glass cylinder there are a little (to 32 and more) tubules from a collodion to dia. 8 mm and 20 cm long. The ends of tubules are connected to a number of the V-shaped glass tubes soldered to the introduction and output tubes passing through the rubber bungs locking the ends of the glass cylinder. After filling of tubes and the cylinder isotonic solution of sodium chloride the introduction tube is connected to a carotid artery of an animal, and output — to a vein; the liquid washing collodion tubes is supported at the level of temperature of blood by means of the thermostat. For prevention of coagulation add hirudine to blood. Thus, blood of an animal can pass a long time through the dialyzer without disturbance of the normal course of blood circulation. In an outside fiziol, solution diffuse from blood the low-molecular substances dissolved in it which can be defined qualitatively and quantitatively. The method of vividiffusion is applied to extrarenal clarification of blood (see. Hemodialysis ) for the purpose of removal of toxicants from it.
Use of dialysis in clinical practice
From 40th 20 century the principle D. began to be used widely both in experimental, and in a wedge, medicine. For the first time proofs to lay down. D.'s opportunities presented Abel and soavt., created the first prototype of the device called by them «an artificial kidney». Perfusing blood of animals through system of the semipermeable tubes washed by the dialyzing solution they established that at the same time it is possible to delete from it metabolites and toxicants of an exogenous origin. A row modern to lay down is based on the principle D. the interventions combined by the term «vivodializ».
The main indicators to use of methods D. in clinic are intoxications endogenous (acute and hron, a renal failure) and exogenous (poisoning with poisons which can be removed by means of D.) origins.
All methods of a vivodializ can be divided into two groups: extracorporal and intrakorporalny. The first group combines all methods where clarification of an organism is carried out ekstrakorporalno, for what biol, the Wednesday which is subject to processing (blood, a lymph, etc.), is brought from an organism and cleared by means of special devices; the second — methods at which semipermeable properties of the preexisting natural membranes in the organism are used.
Extracorporal. includes a hemodialysis, a lymph dialysis and pulmonary dialysis (with use ekstrakorporalno of the connected lung). Found the broadest application in clinic hemodialysis (see) by means of devices artificial kidney (see). Hemodialysis — the most powerful of all means of extrarenal clarification. Implemented in to lay down. to the practician after creation in 1943 by U. Kolff of the first suitable for a wedge, uses of the device and in 1946 N. Alvall of the device for ultrafiltration, it provided considerable decrease in a lethality at an acute renal failure and allowed throughout a long time (up to 10 years and more) to support life of patients at whom kidneys are removed or their function is absent, and also to remove poisons at acute poisoning. A hemodialysis — the main method of training of patients for transplantation of a kidney and in case of need maintenance of their life in the post-transplant period. Both the method, and the equipment for a hemodialysis are constantly improved. One of the most important directions — system development, to-ruyu the patient could carry at itself. The possible solution of such task is creation of «an artificial kidney», edges could work at the minimum quantity of the dialyzing solution. Other perspective direction — development of the device, the principle of action to-rogo will approach the mechanism of work of a natural kidney (use of active ultrafiltration of perfusing blood with the subsequent compensation of the components of plasma necessary for the patient which passed into an ultrafiltrate).
A peculiar option of extracorporal D. — a so-called dialogical parabiosis, or cross D. Predposylkaya for development of a method was served by the assumption that thus will be created an opportunity to provide exchange between Analytical partners of such substances which are removed in the dialyzing solution or a lack of which is available for the patient and cannot be grown stout at a usual hemodialysis. Its essence is that instead of the dialyzing solution in the device blood of the dialytic partner circulates or the same dialyzing solution moves via both dialyzers of dialysis partners. Animals of one or different types (e.g., a pig — a pig, a dog — a goat) can be partners. Attempts to use the Analytical parabiosis and in clinic (the person — a sheep) are made. The method, however, did not leave a stage of experimental studying. One of possible dangers during the use of parabionts of different types is connected with the possibility of transition of small amounts of heterogeneous protein proved now through a membrane of the dialyzer.
The method of a lymph dialysis is based on collecting the lymph (containing metabolites practically in the same concentration as well as plasma) with afterpurification by means of D. and return to her patient. The lymph is received by means of a fistula of a chest channel,
Efficiency of clarification at the same time is limited by a small amount of a lymph, a cut it is possible to receive — as a rule, it is not higher than 10 l in days (at a hemodialysis about 1 l of blood in 5 min.). A lack of a method — relative short duration of function of a fistula (usually no more than several months). As in a lymph cellular forms are presented generally by lymphocytes, attempts to use a method at the same time and for immunol, preparation for transplantation of a kidney were made (due to removal of the lymphocytes which are contained in a lymph and creation of an artificial lymphopenia as the background facilitating the subsequent transplantation).
Connection of allogenic or xenogenic lungs in an experiment also used in the form of one of options extracorporal D. Metodicheski this type of D. make by connection of vascular system of the isolated lungs (through the main vessels) to vascular system of the recipient. The lungs placed in the special cell fill through bronchial tubes with the dialyzing solution which is periodically replaced with fresh. In an experiment by means of such reception it was possible to receive essential decrease in concentration of metabolites (urea). There were separate attempts to apply this method the patient with a renal failure.
It is necessary to refer to this group of methods also clarification by means of D. of ascitic liquid. Ascitic liquid quite often contains a significant amount of complete protein (to 2,5%, is more rare more) and other substances necessary for an organism (amino acids, hormones etc.). Ascitic liquid can be deleted by means of the catheter entered into an abdominal cavity allowing to carry out repeatedly and atraumatic this manipulation. After release from slags of ascitic liquid by means of D. it is returned to the patient (intravenously) again. For reduction of volume of the entered liquid it is subjected in case of need ultrafiltrations (see).
Intrakorporalny. includes peritoneal, pulmonary, pleural, went. - kish., etc. It is most effective from the listed group of methods — peritoneal dialysis (see), offered for the first time by Gunter (G. Ganter, 1923). It consists in introduction to an abdominal cavity of the dialyzing solution into which on the basis of dialytic interaction can pass products of metabolism and toxic agents. This type of D. is used or as fractional (introduction for the determined time of a certain volume of the dialyzing solution with the subsequent its removal and replacement with a new portion) or as flowing (continuous perfusion of solution through an abdominal cavity). On indicators of clarification it approximately by 3 — 4 times concedes to a hemodialysis. Apply it to treatment of patients with an acute renal failure and acute poisonings. For treatment of patients with hron, a renal failure peritoneal D. is applied seldom. For atraumatic repeated connection use a special catheter, are created and the automated systems are applied to preparation and administration of the dialyzing solution according to the planned program.
The pulmonary D. offered by Van-Gemert (A. G. M of van Gemert) with sotr. (1957), consists in periodic filling with the dialyzing solution of own lung or its share. By pilot studies it is established that pulmonary D. allows to delete both products of metabolism, and toxic agents of an exogenous origin (barbiturates, Thiocyanates).
At the pleural D. for the first time offered by Gunter as a semipermeable membrane use a pleura. Drainages through which it is periodically irrigated with a dialysis fluid are entered into a pleural cavity. Use of this type of D. allowed to increase terms of experience of dogs with experimental uraemia, however on indicators of clarification it concedes to peritoneal D. V literature there are messages on several cases of use of pleural D. at a renal failure when use of other methods of extrarenal clarification was impossible. The first attempts of its use at an empyema of a pleura in the postoperative period at wounded in a breast were effective therefore also this type of D. enters a wedge, practice.
Zhel. - kish. (gastrointestinal) D. is subdivided into several versions depending on an action area went. - kish. path and features of a technique. Gastric D. (gastrodialysis, tour lavage) at the ordinary technician of its use (periodic filling with the dialyzing solution of a gastric cavity with the subsequent its removal) can lead to the undesirable shifts connected with removal together with solution of a significant amount of a gastric secret, in particular electrolytes. For prevention of it introduction to a gastric cavity of the cylinder from a semipermeable membrane filled with the dialyzing solution is offered. Eliminating a possibility of disturbance of water and electrolytic balance, this equipment reduces efficiency of clarification. Intestinal D. (perfusion of a small intestine) is usually carried out by means of special probes for introduction and removal of the dialyzing solution. Through a large intestine is carried out usually through a rectum. Sometimes apply a fistula of an appendix to this purpose. Also methods D. practically of all intestines at which the dialyzing solution is entered into a stomach or into a small bowel and is removed through a rectum are developed. The last method demands, however, especially careful control both of a condition of the patient, and of parameters of perfusion. The special option of intestinal D. — perfusion by the dialyzing solution of the isolated site of a small bowel (1,8 — 2,5 m) removed through a front abdominal wall Because of the insufficient speed of clarification and complications this method is unsuitable for long use and therefore it is practically not applied. All kinds of gastrointestinal D. (especially D. of a large intestine) are characterized by low indicators of clarification and considerably concede to peritoneal D. and especially a hemodialysis. In this regard they, as a rule, can be used only as a temporary measure when for one reason or another it is impossible to apply more effective methods of extrarenal clarification. At D.'s carrying out it is necessary to pay special attention to correctness of drawing up the dialyzing solution that provides the necessary correction of electrolytic composition of plasma. Regulation of a water balance is reached by a variation of osmotic pressure of solution. It is also necessary to consider that various departments went. - kish. a path also waters in a gleam of intestines are characterized by the unequal speed of transition of nitrogen-containing metabolites, electrolytes. Advantage of the majority of methods of this group — their relative simplicity.
Attempts to use for D. a mucous membrane of a uterus and a bladder by perfusion of the corresponding cavities revealed their very low performance in this connection they were not studied in detail. At a wedge, use of the considered ways D. the choice of this or that method is defined by features of the patient and conditions to whom therapy is carried out. In some cases on the course of treatment reasonable is a change of a method (e.g., peritoneal D.'s replacement with a hemodialysis, etc.). All options D. used in clinic should be considered as compound though it is frequent also decisive, a part of complex treatment of the patient.
Bibliography: Voyutsky S. S. Course of colloid chemistry, page 10, 255, M., 1975, bibliogr.; Goligorsky S. D. and T ER of e x about in H. T. Acute renal failure, Kiev, 1972, bibliogr.; Deryabin I. I. M. N ilizanets. Peritoneal dialysis, M., 1977; Lopat-kin N. A. and Kuchinsky I. N. Treatment of an acute and chronic renal failure, M., 1972, bibliogr.; Putilova I. N. The guide to a practical training to colloid chemistry, M., 1961; Pytel A. Ya. and d river. Artificial kidney and its clinical use, M., 1961, bibliogr.; A chronic renal failure, under the editorship of S. I. Ryabova, L., 1976; Clinical aspect of uremia and dialysis, ed. by S. G. Massry a. A. L. Sellers, Springfield, 1976, bibliogr.; Praxis der Dialysebehandlung, hrsg. v. H. E. Franz, Stuttgart, 1973, Bibliogr.
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