MIORELAXANTS(Greek mys, my muscle + Latin relaxare to weaken, soften; syn. muscle relaxers) - drugs that reduce the tone of skeletal muscles and, in connection with this, cause a decrease in motor activity up to complete immobility.

Distinguish M. of the central and peripheral types of action.

K M. peripheral action carry curariform substances (see), to-rye cause a relaxation of skeletal muscles due to blockade of neuromuscular transmission (see. Synapse). In accordance with the nature of the effect on neuromuscular transmission, among the drugs of this group, substances of depolarizing (ditilin, etc.), non-depolarizing (tubocurarine diplacin, qualidil, etc.) and mixed (dioxonium, etc.) types of action are distinguished. In addition, pharmacologically active compounds that have a direct inhibitory effect on the tone and contractility of skeletal muscles by reducing the release of Ca 2+ ions from the sarcoplasmic reticulum of muscle tissue can be attributed to M. of peripheral action. Unlike curare-like agents, such compounds inhibit direct excitability of skeletal muscles and do not affect neuromuscular transmission. Thus, these substances can be considered as peripheral M. of direct myotropic action.

This group includes dantrolene (Dantrolene; 1-[(5-arylfurfurylidene) amino]-hydantoin), which is used in honey. practice ch. arr. in the form of sodium salt (Dantrolene sodium; syn. Dantrium). Along with muscle relaxation, dantrolene has a nek-swarm depressing effect on c. n. With. However, unlike M. of the central type of action, it does not affect the central mechanisms of regulation of muscle tone (see). The sensitivity of different groups of skeletal muscles to dantrolene is not the same (the muscles of the limbs are more sensitive to its action than the respiratory muscles). The drug is satisfactorily absorbed by various routes of administration, including from went. - kish. a path, is slowly metabolized in a liver and is allocated by kidneys mainly in the form of inactive metabolites and partially in not changed look. Its half-life from the body is approx. 9 o'clock

K M. central action are referred to as mianesin-like (mefenesin-like) substances, to-rye, in their properties and mechanism of muscle-relaxing action, are close to mianesin (mefenesin), the first drug of this group introduced into honey. practice. According to chem. M.'s structure of central action can be divided into the following groups: 1) propanediol derivatives - mianesin, meprotan (see), isoprotan (see), etc.; 2) oxazolidine derivatives - metaxolone, chlorzoaxazone; 3) benzodiazepines - diazepam (see), chlordiazepoxide (see), etc.; 4) preparations of various chem. structures - orphenadrin, etc. M.'s properties of the central action are also possessed by midokalm.

In the experiment, M. of central action reduce the spontaneous motor activity of animals and reduce muscle tone. At very high doses, they cause flaccid paralysis of the skeletal muscles and apnea due to the relaxation of the respiratory muscles. In subparalytic doses, M. of central action eliminates the phenomena of decerebrate rigidity and hyperreflexia in animals, weakens convulsions caused by strychnine and electric current. Besides, the majority of M. of the central action possesses sedative, and nek-ry preparations (eg, benzodiazepines, meprotan) tranquilizing properties and ability to potentiate action of sleeping pills and analgesics.

Unlike M. of peripheral action, central M., even in sublethal doses, have practically no effect on neuromuscular transmission or direct excitability of skeletal muscles. The mechanism of the muscle-relaxing action of drugs in this group is due to their inhibitory effect on the synaptic transmission of excitation in the c. n. With. The general property of central M. is ability to suppress activity of intercalary neurons of polysynaptic reflex ways of a spinal cord and nek-ry overlying departments of c. n. With. In this regard, M. of the central action actively inhibit polysynaptic reflexes and do not significantly affect monosynaptic reflexes. The suppression of descending inhibitory and facilitating influences from a number of suprasegmental structures (the reticular formation, subcortical nuclei) on the motor centers of the spinal cord also has a certain significance in the mechanism of action of the central M..

M. is used in various areas of honey. practices to reduce skeletal muscle tone. At the same time, the choice of drugs for a particular purpose is carried out taking into account the breadth of their myoparalytic action. So, the vast majority of curare-like substances of depolarizing, non-depolarizing and mixed types of action, which have a small breadth of myoparalytic action, are used for total muscle relaxation of ch. arr. in anesthesiology, as well as in the treatment of tetanus and for the prevention of traumatic complications during electroconvulsive therapy.

Central M., dantrolene and curare-like drugs from among tertiary amines - mellictin (see), etc. - have a wide range of myoparalytic action, which allows them to be used to reduce muscle tone without inhibiting or turning off spontaneous respiration. Such drugs are used for diseases accompanied by patol, increased skeletal muscle tone. In nevrol, practice, for example, they are used in spastic conditions of various origins (cerebral and spinal paralysis, Little's disease, spastic torticollis, etc.). M. central action is also used for muscle contractures of traumatic or inflammatory (eg, rheumatic diseases) origin. The use of drugs of this group with this pathology contributes not only to a decrease in pain in the muscles of the affected area (due to a decrease in muscle tone), but also allows for more efficient rehabilitation of patients, since the elimination of contractures facilitates the treatment. physical education. In anesthesiology, M.'s practice of central action and dantrolene are used relatively less frequently than curare-like substances, and are used for other indications.

Side influence of M. of the central action and dantrolene is shown by hl. arr. weakness, drowsiness, dizziness, dyspeptic disorders. Possible allergic reactions. The specified preparations should not be appointed during work to persons, a profession to-rykh demands exact and fast mental and motive reactions (drivers of transport, etc.).

The use of muscle relaxants in anesthesiology

In anesthesiology, to achieve deep muscle relaxation during surgical interventions, certain diagnostic procedures and mechanical ventilation, drugs from the group of curariform substances are used. Depending on the expected duration of the surgical intervention or diagnostic procedure, the choice of individual curare-like drugs is made taking into account the duration of their action. So, for short-term (within a few minutes) muscle relaxation (with tracheal intubation, reduction of dislocations, reposition of bone fragments, short-term operations and diagnostic procedures), it is advisable to use short-acting curare-like drugs, for example, dithylin (see), tubocurarine (see), anatruksoniy (see), pavulon, etc.; preparations with a long duration of action apply hl. arr. to maintain long-term muscle relaxation during operations under anesthesia with controlled breathing, with artificial lung ventilation, complex and lengthy diagnostic procedures. Ditilin to achieve long-term muscle relaxation can only be used if it is administered by a fractional method or by drip infusion. With the help of curare-like drugs, it is possible to cause a total or partial blockade of neuromuscular transmission. Total blockade is resorted to during long-term operations that require deep muscle relaxation and are performed, as a rule, under conditions of endotracheal general anesthesia (see Inhalation anesthesia).

In cases where total muscle relaxation is not required. but during the operation, it may be necessary to relax the muscles of a certain part of the body (abdomen, limbs), a partial blockade of the skeletal muscles is carried out by introducing small doses of curare-like drugs. The most convenient for this purpose are drugs of a non-depolarizing type of action.

In connection with the preservation of spontaneous respiration, surgical interventions in this case can be performed under mask anesthesia, subject to careful monitoring of the state of gas exchange and readiness to compensate for violations of auxiliary or artificial ventilation of the lungs (see Artificial respiration). The technique of carrying out total muscle relaxation during anesthesia, carried out with the help of special masks (see Mask for anesthesia) without tracheal intubation, has not received wide distribution.

With the combined use of curare-like drugs, it should be remembered that the introduction of the usual dose of non-depolarizing substances (eg, tubocurarine) after repeated injections of dithylin causes a deeper and more prolonged neuromuscular block than under normal conditions. Repeated administration of dithylin after the use of non-depolarizing drugs in normal doses, following short-term antagonism, leads to a deepening of the neuromuscular block of the competitive type and a delay in the recovery period of muscle tone and respiration. To assess the nature of the neuromuscular blockade caused by curare-like drugs, the method of electromyography can be used (see). Electromyographically, a non-depolarizing neuromuscular block is characterized by a gradual decrease in the amplitude of the muscle action potential without previous relief of neuromuscular transmission and muscle fasciculations, a pronounced pessimum in the frequency of irritation, and the phenomenon of post-tetanic relief. Depolarizing (biphasic) neuromuscular block is characterized by a transient relief of neuromuscular transmission, accompanied by muscle fasciculations, and a rapid subsequent development of neuromuscular block. In the first phase, the amplitude of a single muscle action potential is reduced, the tetanus is stable, and the phenomenon of post-tetanic relief is absent. In the second phase, a more or less pronounced pessimum in the frequency of irritation and the phenomenon of post-tetanic facilitation of neuromuscular transmission are revealed. Electromyographic signs of the second phase are noted already at the first injection of dithylin and dioxonium, and with an increase in the number of injections, the severity and stability of these signs increase.

The use of curare-like drugs in myasthenia is a particular problem. Patients with myasthenia gravis (see) are extremely sensitive to drugs of the depolarizing type. The introduction of a standard dose of dithylin leads to the development of a two-phase neuromuscular block with pronounced signs of the second phase, and therefore repeated injections of the drug can lead to excessively prolonged and deep muscle relaxation, impaired respiratory recovery and muscle tone. In the surgical treatment of myasthenia gravis, the method of autocurarization has become widespread, which consists in reducing the dose or canceling anticholinesterase drugs before surgery, using the minimum dose of dithylin during intubation and hyperventilating during surgery, which avoids repeated injections of this drug or limits it to its minimum doses.

There are no absolute contraindications to the use of curare-like drugs, however, with certain diseases, individual drugs of this group may be contraindicated. Therefore, a rational and reasonable choice of curare-like drugs is of great importance, taking into account the nature of the underlying and concomitant diseases. So, in patients with renal insufficiency, impaired water and electrolyte balance, acidosis, hypoproteinemia, there is an increased sensitivity to M. from the group of curare-like substances of a non-depolarizing type of action (tubocurarine, etc.), as well as to curare-like drugs of a mixed type of action (dioxonia, etc. ) due to impaired distribution and elimination of these drugs. A frequent reason for the unusually long action of dithylin is a decrease in the activity of pseudocholinesterase, an enzyme that hydrolyzes this drug (with genetic defects in the enzyme, liver diseases, malignant neoplasms, hron, suppurative processes, bleeding, exhaustion). It is undesirable to use dithylin during eye operations and in patients with increased intracranial pressure due to its ability to increase intraocular and intracranial pressure. The use of dithylin is also dangerous in people with extensive burns, paraplegia, and prolonged immobilization.

Complications in the use of curare-like drugs are largely due to the irrational choice of drugs for a given patient, as well as the use of drugs without taking into account the nature of their interaction with each other and with drugs from other groups of drugs. The most common complication in the use of curare-like drugs in anesthesiology is prolonged apnea - an unusually long-term respiratory depression and muscle tone after using an average dose of the drug. After the introduction of drugs of a competitive type, as well as dioxonia, prolonged apnea may develop in patients with renal failure, acidosis, impaired water and electrolyte balance, hypovolemia, and as a result of the potentiating effect of certain drugs (general and local anesthetics, ganglionic blockers, quinidine, diphenine, beta - adrenoblockers). Repeated injections of dithylin prior to the introduction of tubocurarine may also contribute to the development of prolonged sleep apnea. The myoparalytic effect of dithylin is clearly potentiated by anticholinesterase agents, propanidide, chlorpromazine, cytostatics (cyclophosphamide, sarcolysine), and trasylol. In addition, hypercapnia (see) and respiratory acidosis (see) can be the cause of delayed recovery of breathing and muscle tone after the use of ditilin. For decurarization, anticholinesterase agents (prozerin, galanthamine, etc.) are widely used, blocking cholinesterase and thereby contributing to the accumulation of acetylcholine in neuromuscular synapses, which leads to facilitation of neuromuscular transmission, normalization of respiration and muscle tone. It is also possible to use agents that increase the synthesis and release of acetylcholine in neuromuscular synapses (jermine, pimadin and less effective hydrocortisone, calcium pantothenate).

Terrible, although relatively rare complication associated with the use of curare-like substances, is recurarization. Recurarization is understood as a deepening of residual muscle relaxation up to apnea or severe respiratory depression, which develops, as a rule, in the first two hours after surgery under the influence of a number of factors that disrupt the distribution, metabolism and elimination of drugs. These factors include respiratory and metabolic acidosis, disturbances in water and electrolyte balance, hypovolemia, arterial hypotension, exposure to certain drugs (antibiotics from the group of aminoglycosides, quinidine, trasilol, cyclophosphamide), inadequate decurarization with anticholinesterase agents at the end of the operation.

After the administration of dithylin and, to a lesser extent, dioxonium, noticeable amounts of potassium are released from skeletal muscles into the extracellular fluid, resulting in often transient bradycardia, less often atrioventricular block, and very rarely asystole (the last two complications are described only after the use of dithylin).

Tubocurarine and qualidil have the ability to release histamine, and therefore there is a transient tachycardia that usually does not require special treatment. Rare complications associated with the use of tubocurarine and other curare-like substances of non-depolarizing action include the so-called. proserin-resistant curarization. Usually, the reason for the ineffectiveness of anticholinesterase agents used for the purpose of decurarization is their administration against the background of a very deep blockade of neuromuscular transmission or against the background of metabolic acidosis. Cases of proserin-resistant curarization after the use of an average dose of tubocurarine against the background of repeated preliminary administration of dithylin are described.

Treatment of complications: ensuring adequate artificial ventilation of the lungs up to the restoration of normal muscle tone and elimination of the cause of the complication.

In anesthesiology, M. is also used for other indications. So, M. of central action, which have a pronounced tranquilizing effect, for example, diazepam, meprotan, can be used as a means for premedication before anesthesia (see). Mydocalm is used during electroanesthesia (see). Diazepam in combination with the narcotic analgesic fentanyl is used for the purposes of the so-called. ataralgesia (balanced anesthesia) during certain surgical interventions. Besides, M. of the central action is sometimes used for suppression of a muscular trembling and decrease in heat production at a hyperthermic syndrome (see). Dantrolene also has the ability to stop the manifestations of this syndrome, which sometimes occurs after the use of inhalation anesthetics (eg, halothane) and dithyline.

Bibliography: Kharkevich D. A. Pharmacology of curare-like drugs, M., 1969; The pharmacological basis of therapeutics, ed. by L. S. Goodman a. A. Gilman, p. 239, N. Y. a. o., 1975; Physiological pharmacology, ed. by W. S. Root a. F. G. Hoffmann, v. 2, p. 2, N. Y.-L., 1965; PinderR.M. a. o. Dantrolene sodium, a review of its pharmacological properties and therapeutic efficacy in spasticity, Drugs, v. 13, p. 3, 1977.

V. K. Muratov; V. Yu. Sloventantor, Ya. M. Khmelevsky (anest).

These drugs are practically an indispensable element of combined anesthesia. With their help, muscle relaxation is achieved not by a dangerous increase in the concentration of inhalation anesthetics, but by a break in the impulse from the nerve to the muscle. There are 4 types of muscle relaxants: depolarizing, competitive, mixed and central. The last two types are used very rarely in the clinic.

Depolarizing muscle relaxants (ditylin, listenone) cause persistent depolarization of the end plate of the neuromuscular synapse. As a result, after a short-term excitation (fibrillation), complete relaxation of the striated muscles occurs for 3-5 minutes. Under general anesthesia, the duration of action of depolarizing muscle relaxants is prolonged..

The mechanism of action of competitive muscle relaxants (tubarin, arduan, norcuron) is fundamentally different. It is based on their ability to prevent the interaction of acetylcholine with neuromuscular junction receptors. As a result, depolarization of the end plate of the synapse becomes impossible and persistent relaxation of the skeletal muscles occurs, lasting 40-60 minutes.

By providing muscle relaxation, muscle relaxants allow for more superficial anesthesia, mechanical ventilation during surgery, creating the best conditions for the surgeon to perform the most complex surgical interventions..

Additional drugs. During anesthesia and surgery, it becomes necessary to use methods that allow you to actively influence some body functions. Thus, controlled hypotension, achieved with the introduction of short-acting ganglionic blockers (arfonad, hygronium), can reduce systemic blood pressure, reduce blood loss from the surgical wound, and improve microcirculation. The inhalation anesthetic halothane has the same effect.

With the help of infusion therapy, it is possible to change the volume of circulating plasma according to indications, influence the level of osmotic and oncotic pressure, change the concentration of electrolytes in the blood plasma, affect the blood rheology.

IVL does not just take on the functions of an external respiration apparatus. It improves gas exchange by increasing the functional capacity of the lungs, reduces energy consumption for the work of breathing. By changing the parameters of ventilation, it becomes possible to actively influence pCO 2 , CBS, vascular tone, and, consequently, the blood supply to tissues.

A combination of drugs for anesthesia: tranquilizers, neuroleptics, analgesics, anesthetics, muscle relaxants - and drugs and methods that actively affect the functions of organs and systems of the body, and defines the concept - modern combined anesthesia.

There are many combinations. At the same time, it is advisable to use "standard", tested by practice combinations of drugs for anesthesia, which define the concepts of "type of anesthesia" and "method of anesthesia".

There are combined inhalation general anesthesia, basic anesthesia, neuroleptanalgesia, ataralgesia, central analgesia. Combined anesthesia underlies methods such as controlled hypotension (hypertension) and artificial hypothermia (hyperthermia).

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Muscle relaxants - tubocurarine, diplacin, paramion, fluxedil, dithylin, prokuran and others - block the transmission of nerve impulses from the motor nerve to the striated muscle, causing relaxation of the skeletal muscles, including respiratory, up to apnea. Skeletal muscles, depending on the dose and the individual characteristics of the wounded person, relax in a certain sequence.

The muscles of the neck and limbs are paralyzed first, then the abdominals, ribs, and finally the diaphragm. However, in some people, even with a small dose of a relaxant, relaxation of the entire musculature can immediately occur. In addition, relaxation of the muscles of the limbs and the abdominal press while maintaining spontaneous breathing does not mean at all that the respiratory muscles remained outside the action of the relaxant. Their function inevitably suffers, which leads to disruption of gas exchange.

Therefore, muscle relaxants cannot be used without assisted or controlled breathing.

With sufficient provision of gas exchange, these drugs, paralyzing the skeletal muscles, do not have any negative effect on the functions of other organs and systems.

All muscle relaxants are available in the form of ampouled powders or aqueous solutions that retain activity for a long time; they are administered intravenously. Only dithylin in solution loses activity, therefore, for long-term storage, it is produced in the form of an amulated powder of 0.1; 0.25; 0.5; 1.0, which is dissolved before use in sterile distilled water or in saline.

To relax the muscles of the limbs and abdominals, 100 mg of diplacin, 6-8 mg of paramion, 2-3 mg of procuran, 20-25 mg of ditilin are sufficient. At the same time, ventilation of the lungs decreases by 40-50%, which requires auxiliary breathing. When carrying out the latter, the anesthetist tries to get in time with the natural breathing of the anesthetized, increasing the volume of inhalation by squeezing the bag of the anesthesia machine.

However, assisted breathing is less effective than artificial respiration. Therefore, if possible, artificial lung ventilation should be used, for which dinlacip is administered at a dose of 360-380 mg, and paramion at a dose of 14-16 mg.

The action of these drugs in the indicated doses lasts 40-50 minutes. If it is necessary to prolong muscle relaxation, repeated doses of diplacin and paramion are reduced by half and three times. Most corresponds to military field conditions ditilin. It is used for prolonged muscle relaxation in the form of fractional injections of 100-200 mg.

Complete relaxation of the muscles after the introduction of ditilin occurs in 30-40 seconds and lasts 7-15 minutes. The dose of prokuran is 6-8 mg, while apnea persists for 20-25 minutes.

The action of relaxants after anesthesia can be considered completely stopped after the patient can, at the request of the doctor, arbitrarily change the frequency and depth of breathing, shake hands, and raise his head. If, after anesthesia with muscle relaxants, the patient remains hypopneic, then against the background of ongoing artificial respiration, the so-called decurarization should be performed.

To do this, 0.5-1.0 mg of atropine is administered intravenously, and after the appearance of tachycardia, 1.5-2.5 mg of prozerin is also injected intravenously, but very slowly (3.0-5.0 ml of a 0.05% solution) . With a pronounced slowing of the pulse and abundant salivation, an intravenous injection of atropine at a half dose is quickly repeated.

The described decurarization is effective both after the use of antidepolarizing relaxants - diplacin and paramion, and in hypopnea after anesthesia with nrocurane and dithylin. Prozerin against the background of the action of atropine effectively eliminates hypopnea caused by the "double block" or "second phase" of the action of procurane and ditilin.

Muscle relaxants, causing muscle relaxation, facilitate the work of the surgeon, create conditions for a less traumatic surgical intervention. They weaken the reflex reactions going along the somatic pathways and cause weak inhibition in the ganglia of the autonomic nervous system, which increases the resistance of the operated person to shock. Anesthesia can be carried out at the superficial (most safe) level.

Muscle relaxants in the wounded at the stages of medical evacuation with mandatory assisted or artificial respiration can be used in the following cases:
1) to facilitate intubation after induction anesthesia with sodium thiopental, hexenal, halothane, ether, nitrous oxide;

2) in order to provide the most perfect superficial anesthesia with low consumption of the main narcotic substance and to increase the resistance of the operated person to shock;

3) to relax muscles during endotracheal anesthesia during operations: a) on the organs of the abdominal and thoracic cavities, b) on the limbs to facilitate the reposition of bone fragments and the reduction of dislocations;

4) to turn off natural respiration if it is necessary to use artificial lung ventilation as a method of treating respiratory failure and terminal conditions.

A.N. Berkutov

All muscle relaxants belong to the group of curare-like drugs that act mainly in the area of ​​​​the end of the motor nerves. They have the ability to relax the muscles of the striated muscles of the body, reduce muscle tone, while reducing the movement of the body as a whole. Sometimes this can lead to the fact that he becomes completely immobilized. For example, the South American Indians used the juice of plants containing strychnine as an arrow poison to immobilize animals.

Previously, muscle relaxants were often used only in anesthesiology to relieve muscle spasms during surgical interventions. To date, the scope of these drugs in modern medicine and cosmetology has increased significantly.

Muscle relaxants are divided into two groups:

Use of central muscle relaxants

According to their chemical features, they are characterized by the following classification:

• end compounds of glycerol (prenderol);
• components of benzimidazole (flexin);
• a combination of mixed components (baclofen and others).

Muscle relaxants have the function of blocking polysynaptic impulses by reducing the activity of spinal insertion neurons. At the same time, their influence on monosynaptic reflexes is reduced to a minimum. However, they have a central relaxing effect and are designed to relieve spasmodic reactions, and are also able to affect the body in various ways. Due to this, such drugs are widely used in modern medicine. They are used in the following industries:

1. Neurology (in cases of diseases that are characterized by an increase in muscle tone, as well as in diseases accompanied by a violation of the functionality of the body's motor activity).
2. Surgery (when it is necessary to relax the abdominal muscles, when conducting complex hardware analysis of certain diseases, as well as when conducting electroconvulsive treatment).
3. Anesthesiology (when natural respiration is turned off, as well as for preventive purposes after traumatic complications).

The use of peripheral muscle relaxants

Today there are such types:

• Medications of non-depolarizing action (arduan, diplacin);
• depolarizing agents (ditilin);
• mixed action (dixony).

All these species in their own way affect the musculoskeletal cholinergic receptors, so their use is carried out in order to ensure local relaxation of muscle tissues. Their use in tracheal intubation greatly facilitates such manipulations.

Muscle relaxants are not drugs, they do not cure, they are used by anesthesiologists only in the presence of anesthesia and respiratory equipment.

Before relaxants, sedatives and, preferably, analgesics are necessarily administered, since the patient's consciousness must be turned off. If a person is conscious, then he will experience great stress, because he will not be able to breathe on his own and will understand this, experience great fear and horror. This condition can even bring the patient to the development of myocardial infarction!

Consequences and side effects

They have a fairly large effect on the nervous system. Because of this, they can cause the following characteristic symptoms:

• weakness, apathy;
• drowsiness;
• dizziness and severe headaches;
• muscle microdamage;
• convulsions;
• nausea and vomiting.

Contraindications to the use of a particular drug is determined by the anesthesiologist during surgery, anesthesia and in the postoperative period.

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1. Providing conditions for tracheal intubation.

2. Ensuring muscle relaxation during surgical interventions to create optimal working conditions for the surgical team without excessive doses of drugs for general anesthesia, as well as the need for muscle relaxation during some diagnostic procedures performed under general anesthesia (for example, bronchoscopy).

3. Suppression of spontaneous breathing for the purpose of mechanical ventilation.

4. Elimination of convulsive syndrome with the ineffectiveness of anticonvulsants.

5. Blockade of protective reactions to cold in the form of muscle tremors and muscle hypertonicity during artificial hypothermia.

6. Muscle relaxation during reposition of bone fragments and reduction of dislocations in the joints, where there are powerful muscle masses.

Characteristics of the main drugs, methods of their application

The only currently used representative of depolarizing muscle relaxants is succinylcholine (ditylin, listenone).

The main qualities that determine its popularity despite numerous side effects are a very fast onset of action (from 30 to 60 seconds) and its short duration (less than 10 minutes). The drug is administered at a dose of 1-1.5 mg/kg. However, it should be noted that if precurarization is used, then the intubation dose of succinylcholine is increased by 1.5 times.

Succinylcholine is rapidly degraded by plasma pseudocholinesterase. After a dose of 1 mg / kg, its duration of action is 6-8 minutes. Sometimes it is also used to maintain relaxation by infusion at a rate of 20 to 110 mcg / kg / min (average - 60 mcg / kg / min), especially for short-term manipulations (for example, bronchoscopy) and operations.

Given the large number and severity of side effects, often negating the positive qualities of succinylcholine, at present, indications for its use are increasingly narrowing. It is believed that it makes sense to use depolarizing relaxants only when difficult intubation is expected (to quickly restore muscle tone and transfer the patient to spontaneous breathing in case of failure - although even this provision is debatable, a number of authors believe that in this situation, the use of muscle relaxants should be completely abandoned) or at a high risk of regurgitation and aspiration ("full" stomach), in order to most quickly perform tracheal intubation and transfer the patient to mechanical ventilation, the low qualification of the anesthesiologist (in terms of tracheal intubation) must be added to the indications for the use of ditilin.

Elimination of the drug is carried out due to its destruction by pseudocholinesterase (butyrylcholinesterase) of blood plasma into choline and succinylmonocholine, followed by further hydrolysis of the latter into succinic acid and choline.

The metabolism of the drug is disturbed by hypothermia (slowing down of hydrolysis) and at low concentrations or a hereditary defect of pseudocholinesterase. Non-depolarizing relaxants exhibit an antagonistic effect on succinylcholine. So even precurarization (as mentioned above) forces you to increase the dose of succinylcholine by 50-100%. The exception here is pancuronium. It enhances the action of succinylcholine by inhibiting the activity of pseudocholinesterase.

From a fairly large list of non-depolarizing relaxants, we will consider only the most commonly used ones. And we'll start with the idea of ​​an ideal muscle relaxant.

Properties of the "ideal" muscle relaxant (slide):

high activity;

competitive mechanism of action;

selectivity of action on n-cholinergic receptors of skeletal muscles;

rapid onset of action;

short-term block of neuromuscular transmission (with a single injection, no more than 15 minutes);

lack of potentiation or cumulation upon repeated administration;

no side effects;

low toxicity;

lack of physiological and toxic activity of metabolites and their rapid excretion from the body;

the presence of effective antagonists;

storage stability;

profitability for industrial production.

Table 4

Modern muscle relaxants (1)

Table 5

Modern muscle relaxants (2)

According to the literature, the most used non-depolarizing muscle relaxants in the world today are atracurium and cisatracurium, doxakurium, mivacurium, vecuronium, and the rapidly gaining popularity of rocuronium. Pancuronium (pavulon) and pipecuronium (arduan) are still widely used in our country. In this regard, we will dwell in more detail on the main and side effects of these particular representatives of the class of non-depolarizing relaxants.