MEDICAL BIOLOGY, ANATOMY, HUMAN PHYSIOLOGY AND PATHOLOGY - Ya.I. Fedoniuk 2010

ANATOMY, PHYSIOLOGY, PATHOLOGY

SECTION 1. ORGAN. ORGAN SYSTEM. ORGANISM

GENERAL RESPONSES OF THE ORGANISM TO INJURY

2. SHOCK

Shock (from English shock — blow, concussion) is a typical pathological process characterized by a phased course and caused by impaired neurohumoral regulation. Its development is triggered by extreme factors and a sharp decrease in tissue Blood supply. The general hallmarks of shock include acute progressive microcirculatory failure, leading to Hypoxia, Metabolic Disorders, and ultimately morphological changes. A critical reduction of capillary BLOOD FLOW IN the affected Organs poses a life-threatening danger.

In the Middle Ages, the term "shock" was used to describe the dazed state experienced by knights colliding in tournaments. As a medical term for a pathological process and a clinical Diagnosis, it was introduced by the French military surgeon Landrand, who published a treatise on the subject in Amsterdam in 1741.

According to MODERN CONCEPTS OF primary etiological factors and developmental mechanisms, shock is classified into hypovolemic, hemorrhagic, traumatic (including burn shock), dehydration, anaphylactic, and other types (totaling over 100 varieties).

1. Primary hypovolemic shock. The onset of hypovolemic shock is associated with external or internal blood loss (trauma, including postoperative, vascular damage in pathologically altered organs, blood clotting disorders); plasma loss (Burns, tissue crushing); loss of fluid and electrolytes (intestinal obstruction, pancreatitis, Peritonitis, enterocolitis, overheating); and blood redistribution (thrombosis and embolism of major Veins).

The resulting blood volume deficit leads to a decrease in venous return to The Heart, Cardiac Output, and ARTERIAL BLOOD PRESSURE. Stimulation of peripheral vascular adrenergic receptors increases heart rate and peripheral vascular resistance, which helps restore blood pressure and blood supply, primarily to The Heart and Brain.

The insufficiency of these mechanisms, along with the negative consequences of vasoconstriction, is accompanied by a sharp reduction in Organ and tissue Blood supply and the characteristic signs of shock.

2. Traumatic shock occurs in cases of major injuries to bones, Muscles, and Internal Organs, and is invariably accompanied by damage to nerve endings, trunks, and plexuses. Traumatic shock is complicated by Hemorrhage and wound infection. Its clinical course comprises two stages: the excitation (or erethistic) stage (from Latin erectus — tense) and the inhibition (or torpid) stage (from Latin torpidus — sluggish).

The First stage is short-lived and characterized by Central Nervous system excitation, resulting in heightened activity of the circulatory and respiratory systems, as well as certain Endocrine glands, which release excessive amounts of so-called stress Hormones into the blood, increasing METABOLISM and stimulating organ function.

The Second Stage is more prolonged (ranging from several hours to a day). It is characterized by inhibitory processes in the central nervous system and depressed Functions of vital organs and systems.

As shock progresses, "shock" parenchymal organs develop. For instance, the severity of shock is indicated by urine output: if less than 30 ml of urine is produced per hour, renal function is incompatible with life ("Shock Kidney").

In The Mechanism of origin and development of traumatic shock, a certain role is played by toxemia resulting from the release of decay products from non-viable Tissues into the bloodstream. The Significance of this factor was demonstrated by W. Cannon using the example of "tourniquet shock," which occurs 4 hours or more after the removal of a tourniquet or after the release of prolonged compression of body parts during structural collapses in mines, quarries, earthquakes, bombings, etc.

3. Cardiogenic shock occurs due to a decline in the heart's pumping function (myocardial infarction, myocarditis), severe heart rhythm disorders, or cardiac tamponade (effusion or Hemorrhage into the pericardial cavity).

The leading mechanism in The Development of cardiogenic shock is reduced cardiac output caused by impaired pumping function or obstacles to ventricular filling. As in hypovolemic shock, adrenergic receptor excitation leads to tachycardia and increased peripheral vascular resistance, which only exacerbate hemodynamic disturbances.

4. Vascular forms of shock. These include septic and anaphylactic shock. The common feature in the development of vascular forms of shock is primary vascular tone dysregulation, leading to microcirculatory disorders.

Septic, or infectious-toxic, shock can be triggered by A wide variety of microorganisms: Viruses, rickettsia, parasites, Protozoa, anaerobic flora, but most commonly gram-negative Bacteria. This pathology can result from urinary or biliary tract infections (especially in debilitated and elderly patients), respiratory infections (particularly in the presence of a tracheostomy), septic labor complications, septic abortion, and peritonitis of any Etiology. In the mechanism of septic shock, alongside circulatory failure, toxemia plays a major role, leading to Liver, kidney, and heart damage. In terms of frequency, infectious-toxic shock ranks after hypovolemic and cardiogenic shock, but it ranks first in mortality (50–80%).

Anaphylactic shock develops As a result of hypersensitivity of the Organism to antigenic substances. The most common Antigens include various protein-based drugs, protein-containing sera and Vaccines, anatoxins, organ extracts, and insect and animal venoms. Among medications, anaphylactic shock is primarily triggered by penicillin, streptomycin, sulfonamides, iodine preparations, local anesthetics (novocaine), and aspirin. The Pathogenesis of shock involves the pooling of massive blood volumes in the periphery due to decreased vascular tone; the loss of plasma volume secondary to increased vascular permeability; and respiratory compromise caused by bronchiolar spasm. The clinical picture has an acute, sometimes fulminant course: shock can last literally minutes and result in death.

Thus, the term "shock" is a collective concept uniting extreme states of vital bodily functions that arise as a result of extraordinarily intense or prolonged impacts or external/internal disruptions, manifesting as a complex of physiological system disorders, primarily affecting Circulation, metabolism, and the central nervous system. Sometimes it groups together conditions that are vastly different in their etiological, pathogenetic, and Clinical Features. Nevertheless, the term correctly directs our attention to the extreme and hazardous Nature of the patient's condition.

Pre-existing conditions (radiation sickness, anemia, malnutrition, etc.) reduce the body's resistance to shock. The pediatric organism is particularly sensitive to shock due to its physiological characteristics, namely: a high rate of fluid metabolism, rapid heart rate, low stroke volume, and immature vascular tone and thermoregulation control.