RU2743425C1 - Hemostatic agent based on chitosan aerogel - Google Patents

Abstract

FIELD: medicine.SUBSTANCE: group of inventions relates to the field of medicine, namely to a hemostatic agent based on chitosan, characterized in that it is produced using a non-woven material with a surface density of 20 g/m2to 105 g/m2, impregnated with chitosan aerogel. The invention relates to a method for producing a chitosan-based hemostatic agent, which consists in preparing a chitosan solution followed by supercritical drying, characterized in that a ready-made chitosan solution with a concentration of 1 to 4 mol/l is poured into a non-woven material to form a chitosan gel for at least 6 hours. After that, the product is washed to a neutral pH and the solvent is replaced with a step-by-step increase in the solvent concentration to 10-50-70-90-100-100-100% by weight and subsequent drying of the hemostatic agent using the supercritical drying process.EFFECT: group of inventions provides increased efficiency in the use of a hemostatic agent.6 cl, 3 tbl

Description

The invention relates to medicine, namely to means for stopping external bleeding of varying intensity, including from large blood vessels, and can be used in hospital, field, as well as living conditions for first aid and medical care for wounds and injuries as a local hemostatic agent, including bleeding, in which massive blood loss is the leading cause of death.

Modern materials used for the production of local hemostatic agents differ in their nature, mechanism of action, form of release, scope and features of application, side effects, method of production.

Any hemostatic material has the following characteristics: composition, mechanism of action, range of application (for capillary, parenchymal, venous and arterial bleeding), efficiency (speed of achievement and stability of hemostasis); biocompatibility (the possibility of long-term presence of the material in the body or the need to remove it after short-term use), the possibility and rate of biodegradation, as well as the convenience of surgical treatment after its use.

According to their composition, modern hemostatic materials of local action can be divided into the following groups:

- materials based on biological factors of blood coagulation obtained from animals or humans: collagen, thrombin, fibrin, fibrinogen, plasma and others;

- materials based on cellulose derivatives;

- materials based on synthetic polymers;

- materials based on inorganic compounds (zeolite, silica gel);

- materials based on plant extracts;

- materials based on chitin and chitosan.

Currently, local hemostatic agents based on chitosan, a natural polysaccharide, which can be obtained from the shells of aquatic crustaceans by chemical / enzymatic treatment of chitin or extracted from the culture of fungi, are becoming more widespread. The main properties of chitosan, which determine its successful use, include solubility in aqueous solutions of organic and inorganic acids, the viscosity of the resulting solutions, the ability to form films and granules, biological compatibility, low toxicity, and the ability to degrade in biological media. It is a high molecular weight compound, the macromolecule of which contains a large number of free amino groups, which allows it to bind hydrogen ions and acquire an excess positive charge. Upon contact with blood, positively charged chitosan attracts blood cells (erythrocytes and platelets), the membranes of which are negatively charged, which leads to activation and adhesion of platelets and the formation of a clot, even in the case of defibrinated / heparinized blood. In addition, the positive charge of chitosan promotes the aggregation of negatively charged albumin. It is possible that chitosan promotes the activation of the blood coagulation cascade.

Local hemostatic agents based on chitosan are effective even under hypothermic conditions and, unlike zeolites, do not cause an exothermic reaction upon dissolution or contact with blood.

Known hemostatic agent for topical application based on chitosan salts in a mixture with at least one inert material, which does not cause heat release when mixed with blood, is biologically compatible with body tissues, and has a sufficiently high hemostatic activity (International application WO 2007/074326, publ. 05.07. 2007). The disadvantages of such a hemostatic agent are insufficiently high sorption capacity for blood and, as a consequence, a relatively long period of onset of hemostasis.

Known local hemostatic agent for stopping massive bleeding, obtained on the basis of a salt of chitosan and polyhexamethylene guanidine hydrochloride, covalently cross-linked with a polyfunctional compound from a number of glycidyl ethers (Patent RU 2519220, publ. 10.06.2014). This agent has a high sorption capacity for blood, a short time of onset of hemostasis and high antimicrobial activity. At the same time, the chitosan salt is selected with an average particle size of 0.2-2.0 mm, a degree of chitosan deacetylation of 0.75-0.95, and a molecular weight of 10-500 kDa. The production of funds in the following versions is mastered: powder, granules, bandage and plaster. However, for none of the forms it was possible to achieve a reduction in the time to achieve stable hemostasis, and after applying a powder or bandage, it is necessary to perform compression for 5-7 minutes. In addition, when applying the bandage, there is a pronounced shedding of the hemostatic material.

Known hemostatic medical product made in the form of a one-sided or two-sided multilayer dressing, consisting of at least a substrate and an active layer of nonwoven material based on chitosan nanofibers. The active hemostatic layer is placed on one side on the surface of the substrate, which is a non-woven material with a specific weight of not more than 15 g / m ² , consisting of at least chitosan nanofibers obtained by electrospinning. The substrate consists of one or more layers and contains at least one technological and / or contact layer, each contact layer being placed in close proximity to the active layer and represented by a nonwoven material consisting of aliphatic polyamide nanofibers obtained by electrospinning. The technological layer is made of cellulosic or synthetic material. Between the contact and active layers, a gel-forming layer can be placed, which is a nonwoven material consisting of carboxymethyl cellulose nanofibers obtained by electrospinning. (Patent for PM No. 135,921, publ. 27.12.2013). The patent was implemented in the development of a sterile hemostatic agent "Hemoflex", the "Instructions for use" of which states that after being applied directly to the source of bleeding, manual compression must be carried out for 2-3 minutes.

The disadvantage is the relatively low efficiency of the hemostatic agent and, accordingly, the relatively low quality of first aid and medical care for external arterial and venous bleeding, as well as the possibility of wound infection due to shedding of chitosan particles.

Also, hemostatic agents are described in International patent applications WO 2009/130485, publ. 10/29/2010 and WO 2012/123728 publ. 09/20/2012 (applicant MedTrade Products Ltd) and are commercially available under the trade name Celox®. Powder packaging is the main and basic type of Celox product. Celox granules are the original form of hemostatic agent, which is the basis for all other types of the drug. Celox-A is a hybrid of a syringe and a tampon sleeve containing Celox granules inside. It is used to deliver a hemostatic agent to the immediate source of bleeding in penetrating wounds.

Known version of Celox Gauze in the form of a bandage. It is a dense non-woven (viscose) fabric completely covered with a Celox granule solution. Available as a traditional "round" bandage in a roll ("Celox bandage") and as a flat bandage with a Z-fold ("Celox dressing - Z-folded hemostatic dressing"). In accordance with the "Instructions for use", in order to achieve stable hemostasis after applying the dressing / bandage, it is necessary to perform compression for a duration of 3 to 6 minutes. After removing the dressing / bandage from the package, shedding of the hemostatic material is noted, and after contact with blood, the dressing / bandage loses its softness and flexibility, as a result of which the contact area with the wound surface decreases.

The closest analogue of the claimed agent is a "wound healing and hemostatic agent based on chitosan and a method for its production", in which the agent has the form of spherical particles, and the method for obtaining a hemostatic agent based on chitosan is that a sample of dry high molecular weight chitosan is dissolved in 0.1- 0.2 M acetic acid solution with constant stirring until a homogeneous solution of chitosan in acetic acid is obtained, a solution of a crosslinking agent is prepared in the form of a concentrated alkali solution, a solution of chitosan in acetic acid is introduced in the form of drops into a concentrated alkali solution and the resulting particles are kept in concentrated alkali solution for 24 hours, after which they are repeatedly washed with distilled water until the pH of the medium is 7-8, and the water is replaced with a solvent in several stages, at each of which the particles are placed in a water-alcohol mixture and kept for 3 4 hours, and consecutively on each next At the next stage, the concentration of alcohol in the mixture is increased in increments of 30-60-90-100% by weight, the last step being repeated twice, and finally supercritical drying is carried out for 6 hours at a temperature of 40 ° C, a pressure in the range from 120 to 140 atm and consumption of carbon dioxide 0.2 kg / h. (Patent RU No. 2709462, publ. 12/18/2019).

The general disadvantages of the above technical solutions include the relatively low efficiency of the application, which leads to:

- the need for prolonged compression on the wound area after the application of local hemostatic agents;

- low frequency of primary hemostasis;

- high incidence of recurrent bleeding;

- instability of a blood clot formed at the site of damage to the vessel, with mechanical movement of the limbs.

The disadvantage of funds in the form of powder or granules is the possibility of their washing out with the blood flowing from the wound (especially with massive bleeding) during use, which is especially pronounced in relation to granules with a low specific gravity. In addition, hemostatic granules and powder are often difficult to remove from the wound due to tight adhesion to the wound surface and the edges of the wound, which can lead to the detachment of a blood clot and renewal of bleeding. When in a wound, hemostatic granules and powder can change the local blood circulation of the tissues of the wound cavity (wound canal), which manifests itself in a change in their color and the appearance of edema after removing the hemostatic agent.

When using funds in which particles or granules of chitosan are applied to any base (substrate), shedding of particles of hemostatic material is noted, regardless of the method of application, and after contact with blood, such agents tend to lose their softness and flexibility, which reduces the area of contact with the wound surface, especially in the presence of pockets or a deep wound channel.

The objective of the invention is to create an effective and biocompatible hemostatic agent based on chitosan airgel, local (local) action, having a high sorption capacity for blood, a short time of clot formation and high atraumaticity when removing the agent from the wound, excluding the possibility of damage to a blood clot formed at the site of vessel damage , and recurrent bleeding.

The technical result is to increase the efficiency in the use of a hemostatic agent.

This is achieved by the fact that in the inventive hemostatic agent a single or multilayer nonwoven material is impregnated with chitosan airgel. The method for producing a hemostatic agent based on chitosan consists in preparing a solution of chitosan, which impregnates a nectan material, followed by supercritical drying, according to the invention, a nonwoven material of the required size is poured with a ready-made solution of chitosan with a concentration of 1 to 4 mol / l to form a chitosan gel for a less than 6 hours, after which the agent is washed to neutral pH and the solvent is replaced with a stepwise increase in the concentration of the solvent 10-50-70-90-100-100-100% of the mass and subsequent drying of the hemostatic agent using the supercritical drying process.

Aerogels are materials with high porosity, extremely low density, high specific gravity and a developed inner surface, which can be made from various biopolymers, including chitosan. The use of chitosan-based aerogels for the creation of hemostatic agents will not only allow to achieve rapid stopping of bleeding, but also provide effective, fast and safe treatment of various wounds and injuries due to the sorption of excess wound exudate and its toxic components, antimicrobial action, prevention of secondary wound infection and protection from external traumatic influences.

In particular, one of the most urgent directions is the development of a complex material obtained by impregnating a nonwoven carrier with chitosan airgel. The accelerated hemostatic effect in this case is due to a number of factors:

(1) binding the positively charged functional groups of the chitosan airgel to negatively charged blood cells;

(2) the high sorption capacity of the chitosan airgel used to impregnate the nonwoven material and its developed inner surface, which makes it possible to increase the contact area of blood cells with positively charged amino groups of chitosan;

(3) the physicochemical properties of the complex material, which exclude the washing out of the airgel with the blood flow from the wound, and also ensure the preservation of softness and flexibility after contact with blood, which ensures an increase in the area of contact with the wound surface;

(4) sorption and mechanical properties of the carrier itself, due to which the absorption of an additional volume of liquid and the effect of compression on the damaged vessel is ensured.

The use of the developed complex material will provide effective stopping of massive venous and arterial bleeding while reducing the compression time to 1-2 minutes. The features of this material are biocompatibility with human tissues and the absence of cytotoxicity.

To obtain aerogels, the technology of supercritical fluids is used, namely the supercritical drying process.

The claimed hemostatic agent is a complex medical product, namely a nonwoven material modified by applying a chitosan airgel. Such a tool can be made in the form of a bandage, napkin or bandage. The modification is carried out due to the method of impregnation of the starting material with chitosan gel followed by the application of supercritical drying technology. Due to the properties of chitosan airgel applied to a non-woven material, when it hits the wound surface, it stops bleeding.

A method of obtaining a hemostatic agent based on chitosan airgel.

Obtaining a hemostatic agent, which is a nonwoven material impregnated with chitosan airgel, is carried out in several stages: dissolving chitosan (1), impregnating the agent with a chitosan solution and forming a gel (2), drying the resulting agent (3). The main initial component required to obtain the final material is chitosan. The properties of chitosan should be within the following limits: molecular weight from 100 to 500 kDa (the use of chitosan with a lower molecular weight does not allow for the success of the gel formation stage, and the use of chitosan with a higher molecular weight reduces the hemostatic effect of the final material, that is, its effectiveness), the degree of deacetylation is from 75 to 95% (the use of chitosan, the degree of deacetylation of which is below the specified limits, significantly reduces the hemostatic effect of the final material, that is, its effectiveness; the use of chitosan with a higher value of the degree of deacetylation reduces its solubility and worsens biocompatibility). The carrier of chitosan in within the framework of the invention is a material obtained from natural fibers without the addition or with the possible addition of synthetic fibers (not more than 40%), made by nonwoven technology, the basis weight of which should be in the range from 20 to 300 g / m ² (preferably tionary from 40 to 75 g / m ^2). The use of a material of lower density will not make it possible to obtain a carrier with satisfactory mechanical characteristics, and a material of a higher density will significantly reduce the relative content of chitosan in the final material and, thus, reduce its efficiency.

(1) In the first step of the process, dry chitosan powder is dissolved in an aqueous acid solution. The content of chitosan in the solution should be in the range from 0.5 to 3% by weight, the use of a less concentrated solution does not allow the stage of impregnation and gel formation to be successfully carried out, and a solution of a higher concentration cannot be obtained due to the limited solubility of chitosan. For the preparation of the specified aqueous acid solution, weak organic acids can be used, for example, acetic, lactic, oxalic, etc. An aqueous acid solution is prepared so as to provide the pH of the solution in the range from 2 to 5 units, it is within these limits that the dissolution of chitosan is possible. It is also important to note that the pH of the aqueous acid solution is selected depending on the molecular weight of chitosan. The higher the molecular weight, the lower the required pH of the aqueous acid solution. Thus, a predetermined amount of chitosan powder is introduced into an aqueous solution of an acid of a given composition, which dissolves with vigorous stirring for at least 6 hours. After that, if there is a solid precipitate in the solution, it is filtered off.

(2) Impregnation of the original nonwoven support is carried out after it is placed in the container by direct pouring with the previously prepared chitosan solution. In particular, when impregnating a bandage, the process is carried out in forms of a given size (length 1.5 m, width 8 cm, height 2 cm). In this case, the amount of chitosan solution per bandage is 100-200 ml, depending on the surface density of the original bandage. After impregnation of the agent with a solution of chitosan, it is placed in an aqueous solution of a base, for example, sodium hydroxide, potassium hydroxide, etc. The concentration of this base should be in the range from 1 to 4 mol / L, the use of a solution of a lower concentration will not lead to the successful formation of a chitosan gel. and exceeding the specified concentration limit does not make sense. In the base solution, the formation of chitosan gel is carried out in the volume of the impregnated agent from a nonwoven material due to the volumetric deposition of chitosan, accompanied by the formation of its fibrillar structure. This process lasts at least 6 hours. Next, the obtained product, impregnated with chitosan gel, is washed to neutral pH and the solvent is replaced. Replacing the solvent is necessary for the successful implementation of the next stage of obtaining the finished product, its supercritical drying, since the water that was used in all the previous stages does not mix with carbon dioxide (see stage 3). Replacement is carried out with an appropriate organic solvent, infinitely miscible with carbon dixide, for example, ethanol, isopropanol. To successfully replace the solvent, the concentration of alcohol is increased step by step: 10-50-70-90-100-100-100% of the mass. Only such a step-by-step replacement allows you to obtain a satisfactory shrinkage of the gel during replacement, that is, to maintain the specified structural characteristics of the material and increase the efficiency of the final product.

(3) The chitosan gel impregnated agent obtained in the previous steps is further dried using a supercritical drying process. A feature of the supercritical drying process is the use of supercritical carbon dioxide as a drying agent. The specified substance is miscible with certain organic solvents, for example, ethanol and isopropanol. In the course of supercritical drying, no phase boundary is formed inside the material to be dried, and, therefore, capillary effects do not occur and the developed structure of the resulting material is not destroyed. Only with the use of supercritical drying can aerogels be obtained, which are distinguished by high porosity up to 99% and the presence of a significant proportion of mesopores. The process of drying the agent impregnated with chitosan is carried out using high-pressure apparatus in a flow-through mode. The parameters of the supercritical drying process: pressure 120 atm, temperature 40 ° C, the consumption of carbon dioxide is selected depending on the volume of the apparatus so as to ensure the drying process time is not more than 6 hours.

The finished hemostatic agent is stored in a sterile package.

The inventive hemostatic agent is used as follows.

If bleeding is detected, a hemostatic tourniquet or tourniquet is applied above the bleeding wound or, if this is not possible, the bleeding is stopped by finger pressing. Then the wound is cleaned of blood clots and foreign bodies with a sterile bandage. Next, the package with the claimed hemostatic agent is opened and it is applied by introducing it into the depth of the wound as close as possible to the source of bleeding. A medical dressing package is applied over the wound (according to GOST 1179-93) and a manual or other type of wound compression is provided for 1-3 minutes. Then a pressure bandage is applied over the wound with gauze or other bandage. At the stage of rendering specialized medical care, the claimed hemostatic agent is completely removed from the wound. In most cases, this occurs atraumatically without pain and trauma to the underlying tissues. In this case, after removing the hemostatic agent, the wound remains clean, since the particles of the active composition do not crumble into the wound, and blood clots are adsorbed on the surface of the hemostatic agent; the color of the underlying tissues after removal of the hemostatic agent is not changed. Recurrence of bleeding after removal of the hemostatic agent associated with failure or detachment of a thrombus at the site of vessel damage is not observed. When removing the agent adhering to the wound, it is recommended to moisten it for less trauma to the wound tissues and eliminate pain effects in patients.

The tool in the form of a bandage is convenient to use to stop massive bleeding.

The agent in the form of a napkin or bandage is convenient to use when applied to a wound with light to moderate bleeding. In this case, after removing the napkin, the wound remains clean, since the particles of the active composition remain on the surface of the napkin and do not enter the wound. When using a chitosan airgel napkin, it is necessary to apply it to the wound and hold until the bleeding stops completely.

Examples of the use of the proposed hemostatic agent.

1) The amount of chitosan (in the form of chitosan airgel), which remained after impregnation on the samples of carriers obtained from different nonwoven materials of different density, was estimated. A chitosan sample with a molecular weight of 160 kDa and a degree of deacetylation of 93.1% was used. In the course of the study, the mass of each sample before impregnation with chitosan gel (m ₁ is the initial “empty substrate”) and the mass of the final dried substrate (m ₂ ) were weighed. Based on these data, the mass loading of chitosan was determined, which was calculated by the formula:

(m ₂ -m ₁ ) / m ₂ * 100%

The concentration of the initial chitosan solution in all cases was 2%. The highest "loading" was noted for the samples with the lowest density, and with an increase in the density of the material, the mass loading indicator decreased.

These examples illustrate, but do not limit the proposed technical solution.

2) In experiments in vitro, the properties of materials obtained by impregnating nonwoven carriers with chitosan airgel and used for the manufacture of bandages, dressings and napkins, which can determine hemostatic activity in vivo, were evaluated. Studied procoagulant activity and absorption capacity in relation to water and whole blood for nonwoven carriers (cellulose and bicomponent staple fiber in the ratio 69:31) with a density of 45 g / m ² and 70 g / m ² impregnated with chitosan airgel. For the experiments, we used a chitosan sample with a molecular weight of 125 kDa and a degree of deacetylation of 75%. For comparison, a local hemostatic agent "Celox dressing - Z-folded hemostatic dressing" was used.

To assess the procoagulant activity, a 10 mm * 10 mm sample of material was placed on the bottom of the tube, after which 1.5 ml of native donor blood, obtained from healthy male volunteers aged 25-40 years old, containing 3.8% citrate, was added to the tube. sodium in a ratio of 9: 1. Blood coagulation was initiated by the addition of 0.2 M CaCl ₂ solution, after which the contents of the tube were mixed. The time of clot formation was recorded when the blood in the tube stopped flowing. Each experiment was carried out at least three times.

The assessment of the absorption capacity (under the conditions of excess liquid) was carried out in relation to whole blood and distilled water for a standard sample with dimensions 50 * 50 mm (area 250 mm²), whose weight was denoted as W_one... The test sample was placed in a Petri dish at 37 ° C and 20 ml of donor blood or distilled water was added. After 30 min, the sample was removed with tweezers at one corner, the liquid was allowed to drain for 30 s, and weighed (W₂). Absorption capacity W_wetcalculated by the formula:

W _{wet (blood)} (W _{wet (wet)} ) = (W ₂ -W ₁ ) * 4,

where W _{wet (blood)} is the mass of blood absorbed by 100 cm ^{2 of the} test material

W _{wet (water)} is the mass of water absorbed by 100 cm ^{2 of the} test material.

The analysis was repeated three times for each sample, the average value was taken as the result. The local hemostatic agent Celox - Z-folded hemostatic dressing was used as a comparison sample. As a control sample, we used a non-woven support of the appropriate density, not impregnated with chitosan.

To determine the water absorbency (with partial immersion of the sample), the test sample of a section (tape) 200 mm * 25 mm in size was fixed vertically on a tripod above a container with water. At 37 ° C, the samples were immersed in water so that the bottom edge was 10 mm in water. After 10 min, the height of the wetted part of the sample was measured. The analysis was repeated three times for each sample, the average value was taken as the result. The local hemostatic agent Celox - Z-folded hemostatic dressing was used as a comparison sample. A non-woven support without chitosan was used as a control sample.

The procoagulant activity of the material obtained by impregnating the nonwoven carrier with chitosan airgel was higher than the procoagulant activity in the comparison group. At the same time, the density of the material from which the dressings were made did not have a pronounced effect on the rate of blood coagulation.

The absorption capacity of the material obtained by impregnating the non-woven carrier with chitosan airgel (under conditions of excess liquid) was lower than the corresponding indicator in the comparison group - "Celox-Z-folded hemostatic dressing" and in the control group for both water and for whole blood, regardless of the original density of the material. The material with a density of 70 g / m ² , impregnated with chitosan airgel, was characterized by a higher absorption capacity than a material with a density of 45 g / m ² , both with respect to distilled water and with respect to blood.

On the contrary, the water absorbency during partial immersion was the highest for the nonwoven fabric impregnated with chitosan, both in relation to the reference sample and in relation to the control sample. This indicator increased with increasing density of the nonwoven fabric.

The results obtained indicate that the hemostatic properties of the material may not be directly related to its absorption capacity.

These examples illustrate, but do not limit the proposed technical solution.

3) To assess the effectiveness of the claimed agent, experimental studies were carried out on a model of severe groin injury with damage to the vascular femoral bundle on Romanov sheep. The experiment was performed under general anesthesia on 20 animals, divided into 4 groups: three experimental (group 1 - 4 individuals; group 2 - 6 individuals; group 3 - 6 individuals) and one comparison group - 4 individuals.

The experimental animals used a hemostatic agent obtained by impregnating a nonwoven material with a chitosan airgel. For impregnation used:

- chitosan with a molecular weight of 343-420 kDa and a degree of deacetylation of 90%;

chitosan with a molecular weight of 125 kDa and a degree of deacetylation of 75%;

- nonwoven fabric with a density of 70 g / m, obtained from cellulose fiber (69%) and staple fiber (31%).

In each experimental group, an equal number of samples obtained from chitosan with different physicochemical properties were used.

In the animals of the comparison group, a local hemostatic agent "Celox dressing - Z-folded hemostatic dressing" was used.

Before the experiments, the sizes and weights of the compared MGMs were compared, and the amount of chitosan used in the manufacture of one bandage was calculated.

It was shown that with similar geometrical dimensions:

- 4 times less chitosan is used for the production of an MGS sample based on chitosan airgel than for the production of an MGS sample "Celox dressing - Z-folded hemostatic dressing";

- the technology of manufacturing MGM based on chitosan airgel makes it possible to achieve an almost 4-fold reduction in the weight of the final product.

The use of MGS samples was performed after free bleeding from the femoral artery for 30 s. After placement in the wound, manual compression was performed with various durations:

- group 1-3 min (4 individuals);

- group 2-2 min (6 individuals);

- group 3 - 1 min (6 individuals).

In the animals of the comparison group, in accordance with the “Instructions for use” of the local hemostatic agent “Celox dressing - Z-folded hemostatic dressing”, compression was performed for 3 minutes.

During compression and during further observation, no local thermal reaction in the wound area was noted in any of the cases.

The use of the claimed agent made it possible to achieve stable hemostasis after 120 minutes in most animals:

- in group 1 - in 4 cases out of 4 (100%) with a compression time of 3 minutes;

- in group 2 - in 6 cases out of 6 (100%) with a compression time of 2 minutes;

- in group 3 - in 5 cases out of 6 (83.3%) with a compression time of 1 min.

In 94% of cases (in 15 animals out of 16), along with stable hemostasis after 120 min, primary hemostasis was recorded, which was defined as the absence of bleeding during visual examination of the wound 5 min after injury. The total blood loss per 1 kg of animal weight was 6.7 ± 3.22 ml / kg.

Carrying out a "march test" (five forced flexions and five extensions of the hind limb) after removing the bandage did not cause recurrence of bleeding in any of the cases. In one animal, in which hemostasis was not achieved after 120 minutes, the march test was not performed.

In the comparison group, with a compression time of 3 minutes, hemostasis after 120 minutes was achieved in 3 cases out of 4 (75%). The total blood loss per 1 kg of animal weight was 9.2 ± 4.25 ml / kg. After the "march test" in one case, a relapse of bleeding was recorded. Thus, the final hemostasis 120 minutes after the injury and the application of the local hemostatic agent "Celox dressing - Z-folded hemostatic dressing" was recorded in 2 cases out of 4 (50%).

The use of the claimed agent was more convenient compared to the comparison group in terms of the following indicators:

- the claimed agent was softer and more flexible, without a hard "scratching" coating, and did not form sharp and hard edges when bent, which allowed subjectively more quickly to place the agent in the wound and more quickly to remove it from the wound, and also excluded additional trauma to the skin and the wound surface when using the agent;

- the mechanical properties of the claimed agent (softness and flexibility) did not change significantly after contact with blood, which provided a large contact area of the agent with the wound surface;

- the claimed agent, when placed in the wound, easily took its shape, which made it possible to better "fulfill" all wound cavities, pockets and wound canal;

- when using the claimed agent, practically no shedding of the composition used for impregnation was observed.

From the presented research materials, it can be concluded that, when using the claimed agent, an effective stop of massive arterial bleeding was ensured with a compression time of 1-2 minutes, which significantly exceeds the comparison tool, for which the compression time is 3-6 minutes. The total volume of blood loss when using the claimed agent was 6.7 ± 3.22 ml / kg and was less than when using the comparator - 9.2 ± 4.25 ml / kg, despite the fact that the manufacture of the claimed agent went into 4 times less chitosan than for the manufacture of a comparison tool. In terms of hemostatic activity and ease of use, the claimed agent is also superior to the local hemostatic agent "Celox dressing - Z-folded hemostatic dressing" used as a comparison tool.

Thus, the advantages of the claimed hemostatic agent are:

1. Providing high procoagulant activity of hemostatic material and high absorbency in vitro.

2. Stopping massive arterial bleeding when used in vivo is possible within 1 minute after application.

3. High frequency of primary hemostasis, low frequency of recurrent bleeding, including after the "march test".

4. Absence of allergic reactions and local irritating effects after application.

5. Lack of thermal reaction upon contact with blood, which excludes the possibility of burns during use.

6. Ensuring tight contact and a large area of contact of the hemostatic agent with the wound surface due to the absence of changes in physical and chemical properties after contact with blood.

7. Ease of application and extraction of the hemostatic agent from the wound after application, no signs of impaired blood flow and edema in the walls of the wound cavity (wound channel).

8. Possibility of using the claimed means without changing the geometric width in wounds with a narrow and long wound channel.

9. Significant reduction in the amount of chitosan (up to 4 times), which is used to make one sample of MGS.

10. Low crumbling of chitosan airgel used to impregnate the nonwoven carrier (less than 1%).

11. Stopping bleeding even with the use of antiplatelet agents and anticoagulants.

12. Resistance to radiation exposure.

Claims (6)

1. A hemostatic agent based on chitosan, characterized in that to obtain it, a nonwoven material with a surface density of 20 g / m ² to 105 g / m ² impregnated with chitosan airgel is used. 2. The hemostatic agent according to claim 1, characterized in that for its production, a nonwoven material obtained from cellulose fibers and bicomponent staple fiber from polyethylene terephthalate and polyethylene is used. 3. The hemostatic agent according to claim 1, characterized in that for its production a nonwoven material obtained from 69% cellulose fibers and 31% bicomponent staple fiber from polyethylene terephthalate and polyethylene is used. 4. The hemostatic agent according to claim 1, characterized in that a nonwoven material with a density of 45 g / m ^{2 is} used to obtain it. 5. The hemostatic agent according to claim 1, characterized in that a nonwoven material with a density of 70 g / m ^{2 is} used to obtain it. 6. A method for producing a hemostatic agent based on chitosan according to claim 1 consists in preparing a chitosan solution followed by supercritical drying, characterized in that a carrier made of a nonwoven material is poured into a ready-made chitosan solution with a concentration of 1 to 4 mol / l to form a chitosan gel during for at least 6 hours, after which the agent is washed to a neutral pH and the solvent is replaced with a stepwise increase in the concentration of the solvent 10-50-70-90-100-100-100% of the mass and subsequent drying of the hemostatic agent using the supercritical drying process.