Anterior spinal artery. Blood supply to the spinal cord

It is provided by an anastomotic chain of branches of several (usually 4-8) anterior and smaller (usually 15-20) posterior radicular (radiculomedullary) branches of the vertebral artery, which reach the substance of the spinal cord and form one anterior and two posterior arterial tracts. They supply blood to the spinal cord, roots, spinal nodes and meninges.

There are two types of blood supply to the spinal cord - main and loose. With the main type, there is a small number of radicular arteries (3-5 anterior and 6-8 posterior), with loose such arteries there are more (6-12 anterior, 22 or more posterior).

Two arterial basins can be distinguished along the length of the spinal cord. The upper basin of the vertebral-subclavian arteries (a. vertebralis, a. cervicalis ascendens, truncus costocervicalis) includes a. spinalis anterior and a. spinalis posterior, supplying C1-C4 segments, and 3-7 radicular arteries to supply all other cervical and two to three upper thoracic segments. The lower aortic basin (aa. intercostales posterior, aa. lumbales, rr. sacrales laterales a. iliolumbalis) - radicular branches for supplying all thoracic, starting from Th4, lumbar and sacral segments. The radicular arteries are divided in the spinal canal into anterior and posterior and accompany the corresponding roots of the spinal cord. Each such artery, approaching the surface of the spinal cord, dichotomously divides into ascending and descending branches, which anastomose with similar branches of the superior and inferior radicular arteries, forming the anterior in the anterior median fissure of the spinal cord, and in the posterior lateral grooves - two posterior spinal arteries. Thus, the spinal arteries are not continuous vessels, and the blood flow in them can have opposite directions with the formation of border zones of blood supply along the length of the spinal cord (levels C4, Th4, Th9-L1). With the main type of blood supply, the anterior spinal artery in the zone of the lower pool is formed by branches of one (20%) or two radicular arteries: the anterior radicular (a. radicularis anterior, Adamkevich) and the lower (Desproges-Gotteron artery) or the upper additional radicular artery. The anterior radicular artery enters the spinal canal with one of the spinal roots from Th5 to L5 (usually Th11-Th12), usually on the left, the lower additional one - from L5 or S1; upper additional - from Th3 to Th6.

Three zones of blood supply are distinguished on the diameter of the spinal cord. The first of them covers the anterior horns, the anterior gray commissure, the base of the posterior horns, the adjacent areas of the anterior and lateral cords (central zone) and is provided by the striated-commissural branches of the anterior spinal artery.

From the capillary network of the spinal cord, blood is drained through radially arranged veins into the venous plexuses of the pia mater. From there, it enters through the winding longitudinal collector veins (anterior and posterior spinal veins) and the anterior and posterior radicular veins (from 12 to 43) formed from them into the internal vertebral venous plexuses located in the epidural space. Then, through the intervertebral veins, blood flows into the external venous vertebral plexuses and further into the vertebral, intercostal, lumbosacral, unpaired, superior and inferior vena cava. Partially, blood from the internal vertebral venous plexuses is drained through the foramen magnum into the sinuses at the base of the skull.

The beginning of the study of the blood supply to the spinal cord dates back to 1664, when the English physician and anatomist T. Willis pointed out the existence of the anterior spinal artery.

According to the length, three arterial basins of the spinal cord are distinguished - cervicothoracic, thoracic and lower (lumbar-thoracic):

n The cervicothoracic basin supplies the brain at the C1-D3 level. In this case, the vascularization of the uppermost parts of the spinal cord (at the level C1-C3) is carried out by one anterior and two posterior spinal arteries, which branch off from the vertebral artery in the cranial cavity. Throughout the rest of the spinal cord, blood supply comes from the system of segmental radiculomedullary arteries. At the middle, lower cervical and upper thoracic levels, the radiculomedullary arteries are branches of the extracranial vertebral and cervical arteries.

n In the thoracic basin, there is the following scheme for the formation of radiculomedullary arteries. The intercostal arteries depart from the aorta, giving off dorsal branches, which in turn are divided into the musculocutaneous and spinal branches. The spinal branch enters the spinal canal through the intervertebral foramen, where it divides into the anterior and posterior radiculomedullary arteries. The anterior radiculomedullary arteries merge to form one anterior spinal artery. The posterior form the two posterior spinal arteries.

n In the lumbar-thoracic region, dorsal branches depart from the lumbar arteries, lateral sacral arteries, and iliac-lumbar arteries.

Thus, the anterior and posterior lumbar arteries are a collection of terminal branches of the radiculomedullary arteries. At the same time, along the course of the blood flow, there are zones with opposite blood flow (at the places of branching and junction).

There are zones of critical circulation where spinal ischemic strokes are possible. These are the junction zones of the vascular basins - CIV, DIV, DXI-LI.

In addition to the spinal cord, the radiculomedullary arteries supply blood to the membranes of the spinal cord, spinal roots, and spinal ganglia.

The number of radiculomedullary arteries varies from 6 to 28. At the same time, there are fewer anterior radiculomedullary arteries than the posterior ones. Most often, there are 3 arteries in the cervical part, 2-3 in the upper and middle thoracic, and 1-3 in the lower thoracic and lumbar.

The following major radiculomedullary arteries are distinguished:

1. Artery of the cervical thickening.

2. Large anterior radiculomedullary artery of Adamkevich. It enters the spinal canal at the level of DVIII-DXII.

3. Inferior radiculomedullary artery of Desproges-Gutteron (available in 15% of people). Included at the LV-SI level.

4. Superior accessory radiculomedullary artery at the DII-DIV level. Occurs with the main type of blood supply.

According to the diameter, three arterial pools of blood supply to the spinal cord are distinguished:

1. The central zone includes the anterior horns, the periependymal gelatinous substance, the lateral horn, the base of the posterior horn, Clark's columns, the deep sections of the anterior and lateral columns of the spinal cord, and the ventral part of the posterior cords. This zone is 4/5 of the entire diameter of the spinal cord. Here, the blood supply comes from the anterior spinal arteries due to the striated submerged arteries. There are two of them on each side.

2. The posterior arterial zone includes the posterior columns, the tops of the posterior horns, and the posterior sections of the lateral columns. Here the blood supply comes from the posterior spinal arteries.

3. Peripheral arterial zone. The blood supply here is carried out from the system of short and long circumflex arteries of the perimedullary vasculature.

The venous system of the spinal cord has a central and peripheral sections. The peripheral system collects venous blood from the peripheral parts of the gray and mainly the peripheral white matter of the spinal cord. It flows into the venous system of the pial network, which forms the posterior spinal or posterior spinal vein. The central anterior zone collects blood from the anterior commissure, the medial and central parts of the anterior horn, and the anterior funiculus. The posterior central venous system includes the posterior cords and posterior horns. Venous blood flows into the striated veins, and then into the anterior spinal vein, located in the anterior fissure of the spinal cord. From the pial venous network, blood flows through the anterior and posterior radicular veins. The radicular veins merge into a common trunk and drain into the internal vertebral plexus or intervertebral vein. From these formations, venous blood flows into the system of the superior and inferior vena cava.

The blood supply to the spinal cord, its membranes and roots is carried out by numerous vessels extending at the level of the neck from the vertebral, thyroid and subclavian arteries, at the level of the thoracic and lumbar spinal cord - from the branches of the aorta (intercostal and lumbar arteries). More than 60 paired segmental radicular arteries, formed near the intervertebral foramina, have a small diameter (150-200 microns) and supply blood only to the roots and the membranes adjacent to them. In the blood supply of the spinal cord itself, 5-9 unpaired arteries of large caliber (400-800 microns) are involved, entering the spinal canal at different levels, either through the left or through the right intervertebral foramen. These arteries are called radiculomedullary, or trunk, vessels of the spinal cord. Large radiculomedullary arteries are variable in number and occur in the cervical spinal cord from 2 to 5, in the thoracic - from 1 to 4 and in the lumbar - from 1 to 2.

After entering the subdural space, these arteries that reach the spinal cord divide into two terminal branches - anterior and posterior.

The anterior branches of the radiculomedullary arteries have the leading functional significance. Passing to the ventral surface of the spinal cord to the level of the anterior spinal fissure, each of these branches is divided into ascending and descending branches, forming a trunk, and more often a system of vessels called anterior spinal artery. This artery provides blood supply to the anterior 2/3 of the diameter of the spinal cord due to the striated arteries, the area of ​​distribution of which is the central zone of the spinal cord. Each half of it is supplied with an independent artery. There are several striated arteries per segment of the spinal cord. The vessels of the intramedullary network are usually functionally terminal. The peripheral region of the spinal cord is provided by another branch of the anterior spinal artery - circumferential- and its branches. Unlike the striated arteries, they have a rich network of anastomoses with vessels of the same name.

The posterior, usually more numerous (on average 14) and smaller in diameter, branches of the radiculomedullary arteries form a system posterior spinal artery, its short branches feed the posterior (dorsal) third of the spinal cord.

The anterior spinal artery extends caudally to only a few cervical segments. Below, it does not represent a single vessel, but is a chain of anastomoses of several large radiculomedullary arteries. It is no coincidence that the blood flow in the anterior spinal artery is carried out in different directions: in the cervical and upper thoracic sections of the spinal cord from top to bottom, in the middle and lower thoracic - from bottom to top, in the lumbar and sacral - down and up.

Anatomically, the vertical and horizontal arterial basins of the spinal cord differ.

In the vertical plane, 3 vascular basins of the spinal cord are distinguished:

1. Upper (cervico-dorsal), feeding the spinal cord in the zone of segments C 1 - Th 3.

2. Middle, or intermediate - segments Th 4 - Th 8.

3. Lower, or lumbar - below the Th 9 segment.

The cervical thickening is the functional center of the upper limbs and has an autonomous vascularization. Not only the vertebral arteries, but also the occipital artery (a branch of the external carotid artery), as well as the deep and ascending cervical arteries (branches of the subclavian artery) take part in the blood supply of the cervicothoracic spinal cord. Consequently, the upper vascular pool has the best conditions for collateral circulation.

The collaterals at the level of the middle basin are much poorer and the blood supply to the Th 4 - Th 8 segments is significantly worse. This region is exceptionally vulnerable and is a selective site of ischemic injury. The middle thoracic region of the spinal cord is a transition zone between two thickenings representing the true functional centers of the spinal cord. Its weak arterial blood supply corresponds to the undifferentiated functions.

The lumbar thickening of the spinal cord and its sacral section are sometimes supplied with blood only by one large (up to 2 mm in diameter) Adamkevich artery, which most often enters the spinal canal between the 1st and 2nd lumbar vertebrae. In some cases (from 4 to 25%), the additional artery of Desproges-Gotteron, which enters the canal between the IV and V lumbar vertebrae, participates in the blood supply to the cone of the spinal cord.

Consequently, the conditions of blood supply to different parts of the spinal cord are not the same. The cervical and lumbar sections are supplied with blood better than the thoracic. Collaterals are more pronounced on the lateral and posterior surfaces of the spinal cord. Blood supply is most unfavorable at the junction of vascular pools.

Inside the spinal cord (in the transverse plane), 3 relatively discrete (separated) areas of blood supply can be distinguished:

1. Zone fed by the central arteries - branches of the anterior spinal artery. It occupies from 2/3 to 4/5 of the diameter of the spinal cord, including most of the gray matter (anterior horns, base of the posterior horns, substantia gelatinosa, lateral horns, Clark's pillars) and white matter (anterior cords, deep sections of the lateral and ventral sections of the posterior cords).

2. Zone supplied by the artery of the posterior sulcus - a branch of the posterior spinal artery. Includes the outer sections of the posterior horns and the posterior cords. At the same time, Gaulle's bundle is better supplied with blood than Burdach's bundle - due to anastomotic branches from the opposite posterior spinal artery.

3. Zone supplied by the marginal arteries emerging from the perimedullary corona. The latter is formed by small arteries, which are collaterals of the anterior and posterior spinal arteries. It provides blood supply to the superficial parts of the white matter of the spinal cord, as well as a collateral connection between the extra- and intramedullary vasculature, that is, the vessels of the pia mater and the central and peripheral arteries of the spinal cord.

Most softening foci in the spinal cord are almost always localized in the central basin and, as a rule, they are observed in the border zones, i.e. deep in the white matter. The central pool, which is supplied by one source, is more vulnerable than the zones that are fed simultaneously from the central and peripheral arteries.

Venous outflow

The veins entering the venous plexus of the spinal cord are interconnected in the subarachnoid space with the radicular arteries. The outflow from the radicular veins is carried out into the epidural venous plexus, which communicates with the inferior vena cava through the paravertebral venous plexus.

Veins of the spinal cord. Radicular, anterior and posterior spinal veins (Suh Alexander, 1939)

Distinguish anterior and posterior outflow systems. The central and anterior outflow tracts go mainly from the gray commissure, anterior horns, and pyramidal bundles. The peripheral and posterior pathways start from the posterior horn, posterior and lateral pillars.

The distribution of venous basins does not correspond to the distribution of arterial ones. The veins of the ventral surface drain blood from one area, which occupies the anterior third of the diameter of the spinal cord, from the rest of the blood enters the veins of the dorsal surface. Thus, the posterior venous pool is more significant than the posterior arterial one, and vice versa, the anterior venous pool is smaller in volume than the arterial one.

The veins of the surface of the spinal cord are united by a significant anastomotic network. Ligation of one or more radicular veins, even large ones, does not cause any spinal injury or damage.

Intravertebral epidural venous plexus has a surface approximately 20 times larger than the ramifications of the corresponding arteries. It is a valveless path extending from the base of the brain to the pelvis; blood can circulate in all directions. The plexuses are built in such a way that when one vessel closes, the blood immediately flows out in another way without deviations in volume and pressure. The pressure of the cerebrospinal fluid within physiological limits during breathing, heart contractions, coughing, etc. is accompanied by varying degrees of filling of the venous plexuses. An increase in internal venous pressure during compression of the jugular veins or veins of the abdominal cavity, with complexion of the inferior vena cava is determined by an increase in the volume of the epidural venous plexus, an increase in the pressure of the cerebrospinal fluid.

The connective tissue surrounding the epidural plexus prevents varicose veins.

Compression of the inferior vena cava through the abdominal wall is used in spinal intraosseous venography to obtain better visualization of the venous plexus of the vertebrae.

Although in the clinic it is often necessary to state some dependence of the blood circulation of the spinal cord on the total arterial pressure and the state of the cardiovascular system, the current level of research work allows us to assume autoregulation of the spinal blood flow.

Thus, the entire central nervous system, unlike other organs, has protective arterial hemodynamics.

Not established for the spinal cord minimum blood pressure figures, below which circulatory disorders occur (for the brain, these are figures from 60 to 70 mm Hg (J. Espagno, 1952). It seems that a pressure of 40 to 50 mm Hg cannot be in a person without the appearance of spinal ischemic disorders or damage (C. R. Stephen et coll., 1956)

The delivery of essential nutrients to the soft tissues of the spine is provided by the circulatory system. Any violations lead to a deterioration in the transmission of nerve impulses, the development of pathological changes, hernias, impaired motor and reflex functions.

The blood supply to the spinal cord is provided by two large arteries, as well as additional systems and mediators that help extract nutrients.

How is the blood circulation of the brain of the back

1. Anterior and posterior spinal arteries.
2. Liquor.
3. Pachion granulations.
4. Neurotransmitters.

spinal arteries

Since the internal plexus of the spine is located along the entire spinal column and is in contact with the dura mater of the brain, anatomically the most favorable conditions are provided for the nutrition of soft tissues.

Liquor and pachyon granulations

The spinal cord is suspended, surrounded by cerebrospinal fluid (CSF). The fluid not only serves as a shock-absorbing and protective layer that prevents mechanical damage, but also facilitates the transport of nutrients from the blood to the soft tissues of the brain.

The cerebrospinal fluid is in constant motion. Circulation starts from the choroid plexuses of the ventricles of the brain. Liquor is sent to the subarachnoid space. The final outflow of fluid into the venous sinuses is carried out with the help of granulation of the arachnoid membrane.

neurotransmitters

Circulatory disorders in the spinal cord are often associated with the number and activity of neurosecretory mediators in one cell of nerve fibers.

The general principle of blood supply to the spinal cord is associated with the constant circulation of blood and cerebrospinal fluid. Any violations lead to serious malfunctions in the body.

Causes of disorders of the spinal circulation

According to the ICD 10 code, it is customary to distinguish three main catalysts for violations:

Regardless of the cause of the disorders, transient and chronic disorders of the spinal circulation require timely and qualified treatment.

Treatment of circulatory disorders of the spinal cord

When diagnosing, take into account:

According to the results of the study, the patient is prescribed a course of drug therapy. In acute signs of insufficiency, surgery will be required.

Drugs that improve blood circulation are prescribed with extreme caution. The presence of internal bleeding is an absolute contraindication to taking drugs of this type.

Acute violation of the spinal circulation can be caused by many factors: aneurysm rupture, thrombotic plaque, trauma that provoked a narrowing of the spinal lumen. The task of the attending staff is to accurately diagnose the cause of pathological changes, as well as prescribe timely and qualified treatment.

The spinal cord receives blood mainly from two sources: from the unpaired anterior spinal artery and a pair of posterior spinal arteries(Fig. 16-8). The paired posterior spinal arteries have a rich collateral network and supply the white and gray matter of the posterior spinal cord. The posterior spinal arteries arise from the arteries of the circle of Willis and have numerous collaterals with the subclavian, intercostal, lumbar, and sacral arteries.

Rice. 16-4. Spinal cord

Rns. 16-5. Vertebra, spinal cord with meninges, spinal nerves: transverse section. (From: Waxman S, G., deGroot J. Correlative Neuroanatomy, 22nd ed. Appieton & Langc, 1995. Reproduced with modifications, with permission.)

Due to the rich collateral network, if the arterial segment is damaged, spinal cord ischemia in the basin of the posterior spinal artery is unlikely. A different situation in the basin of the unpaired anterior spinal artery, which supplies the ventral part of the spinal cord, is formed as a result of the fusion of two branches of the vertebral artery and has numerous collaterals with segmental and radicular branches of the cervical, thoracic (intercostal arteries) and lumbosacral (Fig. 16- 9). Posterior lateral spinal arteries - branches of the vertebral artery, passing down, supply the upper thoracic segments with blood. Unpaired segmental branch of the aorta (Adamkiewicz artery, or large radicular artery) provides almost all blood supply in the lower thoracic and lumbar segments. Damage to this artery entails the risk of ischemia of the entire lower half of the spinal cord. Adamkevich's artery passes through the intervertebral foramen, most often on the left,

Physiology

The physiological effects of the central blockade are due to the interruption of afferent and efferent impulses to autonomic and somatic structures. Somatic structures receive sensitive (sensory) and motor (motor) innervation, while visceral structures receive autonomic ones.

Rice. 16-6. Scheme of the relative positions of the vertebral bodies, segments, spinal cord and the roots of the spinal nerves emerging from them. (From: Waxman S. G., deGroot J. Correlative Neuroanatomy, 22nd ed. Appieton & Lange, 1995. Reproduced with modifications, with permission.)

Rice. 16-7. Regional differences in the structure of the spinal cord

Somatic blockade

Pain prevention and skeletal muscle relaxation are the most important goals of central blockade. A local anesthetic of the appropriate duration of action (selected depending on the duration of the operation) is injected into the subarachnoid space after a lumbar puncture. The anesthetic mixes with the cerebrospinal fluid and acts on the spinal cord. The spread of the anesthetic along the long axis of the spinal cord depends on a number of factors, including gravity, cerebrospinal fluid pressure, the position of the patient, the temperature of the solution, etc. The local anesthetic mixes with the cerebrospinal fluid, diffuses and penetrates into the substance of the central nervous system. Blockade requires that the anesthetic penetrate the cell membrane and block the sodium channels of the axoplasm. This process occurs only at a certain minimum threshold concentration of local anesthetic (Km, from English, minimum concentration - minimum concentration). But nerve fibers are not homogeneous. There are structural differences between the fibers that provide motor, sensory and sympathetic innervation.

There are three types of fibers, referred to as A, B and C. Type A has subgroups α, β, γ and δ . The functions of fibers depending on the type and subgroup are given in Table. 16-1. The nerve root is made up of fibers of various types, so the onset of anesthesia will not be instantaneous. In other words, the minimum concentration of local anesthetic (Km) required to interrupt a nerve impulse varies depending on the type of fiber (chap. 14). For example, small and myelinated fibers are easier to block than large and unmyelinated ones. Now it's clear why A γ- and B fibers are easier to block than large Aα and unmyelinated c fibers. Since there is diffusion and dilution of the local anesthetic, complete blockade of the most resistant fibers may not occur. As a result, the border of sympathetic blockade (which is judged by temperature sensitivity) can be two segments higher than the border of sensory blockade (pain and tactile sensitivity), which in turn is two segments higher than the border of motor blockade. Segments in which a blockade of some is received and no blocking of others occurs are called zone of differential blockade. When evaluating anesthesia, it is important to keep in mind which blockade has been achieved: temperature (sympathetic), pain (sensory, sensitive) or motor (motor), because the maximum severity of each of them is not the same in different segments.

Varying degrees of somatic fiber blockade can create clinical problems. The sensation of strong pressure or significant motor influences is transmitted through C-fibers, which are difficult to block. Similarly, the border of motor blockade can be much lower than sensory. Consequently, the patient retains the ability to move in the operated limb, which may interfere with the work of the surgeon. In addition, especially anxious patients may perceive tactile

Rice. 16-8. Arterial blood supply to the spinal cord

sensations from touch as painful. Sedation and good psychological contact with anxious patients can prevent unwanted perception of proprioceptive reception as pain.

Visceral blockade

Most of the visceral effects of the central blockade are due to the interruption of the autonomic innervation of various organs.

Circulation

Interruption of sympathetic impulses causes hemodynamic changes in the cardiovascular system, the severity of which is directly proportional to the degree of medical sympathectomy. The sympathetic trunk is connected to the tora-coabdominal region of the spinal cord. The fibers that innervate the smooth muscles of the arteries and veins depart from the spinal cord at the level of the T V -L I segments. With medical sympathectomy using a local anesthetic, arterial tone is predominantly preserved (due to the action of local mediators), while venous tone is significantly reduced. Total medical sympathectomy causes an increase in the capacity of the vascular bed, followed by a decrease in venous return and arterial hypotension. Hemodynamic changes with partial sympathectomy (blockade up to T VIII level) are usually compensated by vasoconstriction mediated by sympathetic fibers above the level of blockade. In fair-skinned people, vasoconstriction can be seen with the naked eye. Sympathetic fibers that go as part of the thoracic cardiac nerves (T 1 -T 4) carry impulses that speed up heart contractions. With high central blockade, the tonic activity of the vagus nerve becomes unbalanced, which causes bradycardia. Lowering the head end of the body and infusion of fluid cause an increase in preload, venous return increases and cardiac output normalizes. Holinoblockers eliminate bradycardia.

The severity of arterial hypotension determines the choice of therapeutic measures. The most sensitive target organs are the heart and brain. A moderate decrease in oxygen delivery to the heart is compensated by a decrease in myocardial work and oxygen consumption. The afterload is significantly reduced, and the work of the heart associated with overcoming the total peripheral vascular resistance is also reduced. With a significant and untreated decrease in preload, these compensatory reactions are untenable. Autoregulation of cerebral circulation is a mechanism by which the brain is largely protected from arterial hypotension.

In healthy people, cerebral blood flow remains unchanged until the mean arterial pressure falls below 60 mm Hg. Art. (ch. 25).

Treatment and prevention of arterial hypotension are organically linked with the understanding of the mechanisms of its development. Immediately before performing the blockade and after that, during anesthesia, fluid infusion is carried out.

Rice. 16-9. Segmental nature of the blood supply to the spinal cord (A, B)

TABLE 16-1. Classification of nerve fibers

Infusion of crystalloids at a dose of 10-20 ml/kg partially compensates for the deposition of blood in the veins caused by medical sympathectomy.

Treatment includes a number of measures. Lowering the head end (or raising the foot end) potentiates the action of infusion solutions, which contributes to a rapid increase in preload. With severe bradycardia, anticholinergics are used. If these measures are ineffective or there are contraindications to massive infusions, then adrenomimetics of direct or indirect action are used. Adrenomimetics of direct action (for example, phenylephrine) restore venous tone, cause arteriolar vasoconstriction and increase preload. The theoretical disadvantage of direct-acting adrenomimetics is an increase in afterload, leading to an increase in myocardial work. Adrenomimetics of indirect action (for example, ephedrine) increase myocardial contractility (central effect) and cause vasoconstriction (peripheral effect). The peripheral effect of indirect agonists cannot be realized when endogenous catecholamines are depleted (for example, during long-term treatment with reserpine). With deep arterial hypotension, the introduction of adrenaline allows you to restore coronary perfusion and prevent cardiac arrest due to myocardial ischemia.

Breath

Interrupting impulses along the motor nerves of the body, the central blockade affects breathing. The intercostal muscles provide both inhalation and exhalation, and the muscles of the anterior abdominal wall provide forced exhalation. The blockade will impair the function of the intercostal muscles at the level of the respective segments, and the function of the abdominal muscles will suffer in all cases (except perhaps for a particularly low blockade). The function of the diaphragm is not affected, because the transmission of the nerve impulse along the phrenic nerve is rarely interrupted even with high blocks in the cervical region. This resistance is not due to the fact that the local anesthetic solution cannot reach the segments of the spinal cord from which the roots of the phrenic nerve (C 3 -C 5) depart, but due to insufficient concentration of anesthetic. Even with total spinal anesthesia, the concentration of anesthetic is significantly lower than that at which blockade of type Aα fibers in the phrenic nerve or blockade of the respiratory center in the brainstem is possible. Apnea associated with high central blockade is transient, lasts much less than the anesthetic continues to act, and is most likely due to brainstem ischemia due to hypotension.

Even with a high blockade at the level of the thoracic segments, the gas composition of the arterial blood does not differ from the norm. Tidal volume, minute volume and maximum inspiratory volume are usually dependent on diaphragmatic function. Functional residual capacity and forced expiratory volume decrease in proportion to the decrease in activity of the abdominal and intercostal muscles. In healthy people, ventilation disorders do not occur, which cannot be said about patients with chronic obstructive pulmonary disease, who must use auxiliary muscles for active exhalation. The loss of tone of the rectus abdominis muscles makes it difficult to fix the chest, and the loss of tone of the intercostal muscles prevents active exhalation, therefore, in chronic obstructive pulmonary disease, central blockade can lead to a decrease in ventilation. Early signs of such a decrease include a subjective feeling of lack of air and increased dyspnea. These phenomena can rapidly progress to a feeling of suffocation and the onset of panic, although oxygenation and ventilation are maintained at the initial level. Ultimately, hypercapnia can turn into acute hypoxia even with oxygen therapy. Patients with severe restrictive lung diseases or acute bronchospasm, in whom the auxiliary muscles are involved in the act of inhalation, are also at risk due to a decrease in the tone of the intercostal and abdominal muscles.

Regional anesthesia is indicated for patients with concomitant lung diseases (there is no need for manipulations in the airways, no need for mechanical ventilation, there is no increase in the ventilation-perfusion ratio) - but only on condition that the upper limit of motor blockade does not extend above the level of the T VII segment. In cases where a higher level of blockade is needed (surgeries on the organs of the upper abdominal cavity), isolated regional anesthesia is not the method of choice for concomitant lung diseases.

In the immediate period after operations on the organs of the chest cavity and the upper floor of the abdominal cavity, regional anesthesia (which is performed only if sensory blockade without motor blockade is technically possible) prevents pain and the reflex shallow breathing associated with it. At the same time, productive coughing and deep breathing are possible, which allows you to evacuate the secret from the respiratory tract and prevent the occurrence of atelectasis.