Detoxification hemosorption

Therapeutic hemosorption is based on the fixation of chemical compounds on non-selective carbon sorbents of natural or synthetic origin, which is determined by the forces of molecular adhesion of Van der Waals, the strength of which is due to the formation of covalent bonds between the toxicant and the sorbent. Effective sorption of target metabolites is ensured by a large total surface area of the sorbent - up to 1000 m2 ^/ g, and the surface area of the carbon formed by pores significantly exceeds the external surface area of the carbon, and the total pore volume is up to 1 ml /g. The degree of sorption mainly depends on the capacity of the micropores of the sorbent, as well as on the polarizability and geometric characteristics of the sorbed toxic substance.

In general, the sorption capacity of activated carbon is very high: 1 g of activated charcoal can sorb 1.8 g of mercuric chloride, 1 g of sulfonamides, 0.95 g of strychnine, 0.9 g of morphine, 0.7 g of atropine, 0.7 g of barbital, 0.3-0.35 g of phenobarbital, 0.55 g of salicylic acid, 0.4 g of phenol and 0.3 g of ethanol from inorganic solutions.

The kinetics of sorption in the outer layer of the sorbent is determined by the sorbate supply and is limited by the molecular diffusion of the sorbed component in a non-stirred thin layer directly adjacent to the surface of the granules, called the Nernstian film, which is destroyed only with intensive turbulence of the biological fluid flow. The sorption rate in this case is inversely proportional to the effective radius of the granules, and the activation energy of external diffusion is relatively low and is only 4-20 kJ/mol. The rate of the process increases with turbulence of the flow, reducing the thickness of the Nernstian film, as well as with an increase in the concentration of the sorbed component.

Intra-diffusion kinetics, in turn, is determined by the concentration of the sorbent in the micropores and its diffusion gradient. The sorption rate in this case is inversely proportional to the squared radius of the sorbent granules. The activation energy of diffusion for this type of kinetics is significantly higher and is 40-120 kJ/mol. Thus, for intra-diffusion kinetics, it is desirable to use sorbents with the smallest possible granule size, which allows for a significant intensification of the process. The most stable fixation of toxic substances and the fastest kinetics are noted in micropores. In addition, due to the high adsorption potential in the micropore area, larger molecules can also be fixed.

A large number of natural (mineral, animal, plant) and synthetic sorbents have been synthesized, and the activity of plant sorbents is recognized as higher than others.

The mechanism of the therapeutic effect of hemosorption is divided into three main components: etiospecific, associated with the accelerated removal of the etiologic factor, i.e. the toxicant that caused the poisoning, pathospecific, detected during the elimination of pathogenetically significant factors ("medium molecules", circulating immune complexes, etc.), nonspecific, manifested in relation to the correction of homeostasis parameters. The main advantage of hemosorption is considered to be the intensive extraction of hydrophobic and fat-soluble toxic substances from the blood (clearance 70-150 ml/min), which allows for a short time to reduce the concentration of the toxicant in the blood from lethal or critical to the threshold and thereby minimize the spatiotemporal delay of therapeutic measures in relation to the moment of poisoning. The immediate detoxifying effect of hemosorption is supplemented by the purification of the blood from "medium molecules", the clearance of which reaches 25-30 ml/min.

Among the non-specific effects of hemosorption, its influence on hemorheological indices is most noticeable, primarily related to the disaggregation of formed elements (erythrocytes, thrombocytes). Blood viscosity and hematocrit decrease, fibrinolytic activity of blood plasma increases, which leads to the removal of fibrin destruction products from the microcirculatory bed, as a result of which the degree of development of DIC syndrome and related organ disorders significantly decreases. On the 1st-3rd day after hemosorption, the content of functionally most complete, highly stable erythrocytes in the blood increases significantly and the number of low-resistant cells decreases.

The beneficial effect of hemosorption on homeostasis parameters is accompanied by a significant acceleration of the elimination of toxic substances from the body, which is manifested by a reduction in the half-life of toxicants in the blood (barbiturates, chlorinated hydrocarbons, chlorinated hydrocarbons) by 3-10 times, in addition, the resistance of tissues to the action of toxicants in high concentrations increases significantly. High clinical and laboratory efficiency of hemosorption is noted in poisoning with psychotropic and hypnotic drugs (barbiturates, benzodiazepines, phenothiazines, leponex, etc.), chlorinated hydrocarbons, salicylates, quinine, pachycarpine hydroiodide, anti-tuberculosis drugs and many other toxicants, hemosorption is most effective in the early stages of poisoning with poisonous mushrooms (death cap, false champignons, etc.).

The clinical effect of hemosorption in the toxicogenic stage of poisoning is manifested by a reduction in the duration of toxic coma, correction of laboratory indicators of endotoxicosis, which contributes to a more favorable course or prevention of organ disorders, especially hepatorenal and neurological. As a result, the duration of inpatient treatment of patients is reduced.

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Method of detoxifying hemosorption in acute poisoning

Equipment	Hemosorption devices Perfusion units for HD devices, plasmapheresis, hand pump For short-term (within 30-40 min) arteriovenous perfusion, a perfusion unit is not needed
Mass transfer device	When performing hemosorption at the prehospital stage, the amount of sorbent can be reduced to 75-100 ml with a corresponding reduction in the size of the mass exchanger.
Highway system	Disposable special When using bottles with sorbent - additionally a universal slotted nozzle to ensure blood flow through the sorbent
Vascular access	Catheterization of the main vein, when using the subclavian vein - followed by X-ray examination of the chest organs, arteriovenous shunt
Preliminary preparation
Hemodilution	12-15 ml of fluid per 1 kg of the patient's body weight until the hematocrit decreases within 35-40% and the central venous pressure reaches about 60-120 mm H2O
Auto-coating of the sorbent surface with blood	When using natural (uncoated) carbons Perfusion through a sorbent of a special protective solution (5 ml of the patient's blood + 400 ml of 0.85% sodium chloride solution) with the addition of sodium heparin (5000 U) for 10-15 minutes In case of unstable hemodynamics, 50 mg of prednisolone and 1-2 ml of 0.1% norepinephrine solution (or adrenaline and ephedrine) are added to the protective solution
Heparinization	General, 350-500 U of sodium heparin per 1 kg of patient's body weight. In case of risk of bleeding - dosed heparinization with a reduction in the dose of sodium heparin by 1.5-2 times with its constant intravenous drip administration in isotonic glucose or electrolyte solutions or regional heparinization with inactivation of sodium heparin with protamine sulfate at the outlet of the sorption column.
Blood perfusion method	Blood is taken from the vessel using a pump, it enters the detoxifying column, contacts with the sorbent and returns to the blood; it is taken from the vessel using a pump; it enters a bottle containing activated carbon, through the internal channel of the universal perfusion slot nozzle, contacts with the sorbent and returns to the bloodstream through the second vessel through the external channel of the slot nozzle; gravity flow of blood (in the presence of an arteriovenous shunt) through a column or bottle with sorbent - in the presence of unstable hemodynamics with the risk of worsening its disorders; venoarterial perfusion of blood using a pump in the development of hemodynamic disorders - within 30-40 minutes to avoid an increase in acidotic changes in arterial blood
Blood perfusion rate	During the first 5-10 minutes of the operation - gradual increase in the blood perfusion rate from 50-70 ml/min to 100-150 ml/min with maintenance of the achieved blood flow rate until the end of the operation
Blood perfusion volume	1-1.5 BCC (6-9 l) during one hemosorption session (1 hour)
Recommended modes	The duration of one hemosorption session is 1 hour. When using columns with a volume of 150 ml, the duration of operation of each column is 30 minutes. The number of hemosorption sessions is no more than 3. During breaks between sessions, forced diuresis is performed, measures are taken to correct water-electrolyte and acid-base balance and other homeostasis parameters.
Indications for use	Clinical poisoning with poorly dialyzable poisons, pronounced clinical picture of poisoning with poisons that circulate in the blood for a long time Laboratory presence in the blood of lethal concentrations of poisons and critical concentrations of poorly dialyzable poisons
Contraindications	Hypotension refractory to therapy. Gastrointestinal and cavitary bleeding.
Premedication	Chloropyramine (1-2 ml of 1% solution), prednisolone (30-60 mg) intravenously