Etiology: what triggers the shock response
Shock is caused by an extreme factor of high intensity. As a rule, such an impact leads to massive destruction of structural elements in tissues and organs.
The main causes of the pathology include:
- Extensive trauma. This includes tissue tears and crushing, extensive burns, and severe electric shock.
- Massive blood loss. In most clinical cases, it is combined with severe trauma.
- Hemotransfusion complications. They occur when a patient is transfused with a large volume of incompatible donor blood.
- Allergic reactions. They develop when specific allergens enter the internal environment of a previously sensitized organism.
- Acute organ damage. The condition can be triggered by significant ischemia or extensive necrosis of vital structures (heart, kidneys, liver, intestines).
Risk factors (predisposition)
Not every extreme impact leads to shock. The probability of its development largely depends on the initial state of the organism. Factors that increase the risk (predisposition) include:
- Extreme temperature exposures (severe hypothermia or hyperthermia).
- Prolonged nutritional starvation.
- Pronounced nervous or mental overexcitation.
- Significant physical fatigue and exhaustion.
- Impairment of general body reactivity (formation of hyperergic or hypoergic states).
- Presence of severe comorbid chronic diseases.
- Individual high sensitivity of the patient to a specific extreme impact.
Classification of shock types
In modern pathophysiology, there is no single universally accepted classification. The main criterion for differentiating these conditions is the cause (etiology).
Clinically significant types of shock:
- Traumatic (wound) and hemorrhagic.
- Burn and electrical.
- Post-transfusion.
- Allergic (anaphylactic).
- Cardiogenic.
- Toxic and septic.
- Psychogenic (mental).
In practical medicine, classification by severity is also used. Three grades are distinguished:
- Grade I shock (mild).
- Grade II shock (moderate).
- Grade III shock (severe).
Stages of the pathological process
Regardless of the cause and severity of clinical manifestations, the pathogenesis of shock always proceeds in two consecutive stages.
1. First stage Historically, it is called ererectile. Modern designations: adaptive, compensatory, non-progressive, or early stage. Clinically and pathophysiologically, it is characterized by generalized excitation. During this period, both specific and non-specific adaptive reactions aimed at maintaining life and combating the extreme factor are urgently activated in the body.
2. Second stage The main condition for its development is the insufficiency of the body's adaptive processes. Previously, it was called the stage of general inhibition or torpid (from Lat. torpidus — sluggish). The modern medical designation is the stage of maladaptation or decompensation.
The second stage is heterogeneous and includes two substages:
- Progressive: there is complete exhaustion of the body's compensatory reactions, leading to pronounced tissue hypoperfusion (reduced blood supply).
- Irreversible: characterized by the development of critical structural and functional changes incompatible with life.
Briefly: answers to topical questions
What specific compensatory mechanisms are activated during the erectile stage of shock?
During the erectile stage of shock, mechanisms aimed at urgent compensation of hypoxia and centralization of blood circulation are activated. Key reactions include:
- Neuroendocrine activation — a significant increase in the activity of the sympathoadrenal and adrenocortical systems.
- Vascular response — compensatory vasoconstriction (primarily of the skin and intestinal vessels), ensuring the preservation of blood supply to vital organs.
- Hemodynamic changes — increased blood pressure, tachycardia, and increased blood flow velocity.
What is the detailed pathogenesis of the progressive substage of shock at the microcirculatory level?
In the progressive substage of shock, sources cite:
- Exhaustion of adaptive mechanisms / compensatory reactions.
- Tissue hypoperfusion of all organs due to mounting arterial dilation.
- Profound collapse and a pronounced clinical picture.
- Development of metabolic and circulatory disorders.
Regulation at this stage is also described by:
- progressive decrease in the effects of neural and hormonal influences up to their complete absence;
- the cause of this decrease is receptor hyposensitization;
- factors: mounting acidosis, intra- and extracellular ion imbalance, altered state of cell membranes, especially neurons.
What hemodynamic parameters and criteria are used to determine the severity of hemorrhagic shock?
To assess the severity of shock and associated blood loss, the Allgower shock index is used.
It is based on the fact that during shock, the heart rate increases while systolic blood pressure decreases.
Formula:
Index = heart rate (bpm) / systolic BP (mmHg)
Interpretation:
| Index value | Interpretation |
|---|---|
| 0,5 | Normal |
| 1,0 | Transition from early stage to pronounced shock |
| 1,5 | Developed shock |
Assessment of blood loss using the Allgöwer index:
- index 1 ≈ blood loss of 20–30% of total blood volume (TBV);
- index > 1 ≈ blood loss of 30–50% of TBV.
The higher the index, the more severe the shock and the graver the prognosis.
What pathomorphological changes occur in the so-called "shock organs"?
Changes develop in "shock organs" due to the centralization of blood circulation, circulatory hypoxia, and disseminated intravascular coagulation (DIC) syndrome. Main manifestations:
- Shock kidney — acute tubular necrosis (necrosis of the convoluted tubule epithelium), blood sludge and thrombi in vessels, interstitial edema.
- Shock lung — foci of atelectasis, serous-hemorrhagic edema, fibrin strands precipitation (hyaline membranes).
- Brain — ischemic encephalopathy (edema, petechial hemorrhages, foci of necrosis).
- Heart — subendocardial hemorrhages, myocardial necrosis, fatty degeneration of cardiomyocytes, and phenomena of their hypercontraction.
To avoid confusing the stages, remember the rule of two "E"s and two "T"s. The first stage is the Erection stage (characterized by Emergency excitation and adaptation). The second stage is the Torpid stage (manifested by Severe Torpor and decompensation).
Class and exam questions
Is spontaneous recovery of the body from a state of shock possible?
As a rule, no. Recovery from this extremely severe condition is possible only through emergency and effective medical interventions. Without treatment, the process progresses to a terminal state.
What is the main criterion in classifying types of shock?
Since there is no single universally accepted classification, the etiological factor (direct cause) acts as the main differentiation criterion, for example: trauma, burn, allergen, or incompatible blood.
Why is the erection stage replaced by the torpid stage?
The transition to the second stage (decompensation) occurs due to the insufficiency of adaptive processes. When specific and nonspecific compensatory reactions are depleted, generalized excitation is replaced by general inhibition and tissue hypoperfusion.
What else to study on this topic
- Mechanisms of tissue hypoperfusion development in the progressive substage.
- Specific and nonspecific adaptive reactions of the erection stage.
- Pathogenesis of transfusion shock during incompatible blood transfusion.
- Criteria for the transition from the progressive substage to the irreversible one.
- The role of the nervous and endocrine systems in the formation of compensatory reactions.
Master the entire topic in the "Pathophysiology" course
This is a summary. The course covers everything tested in classes and exams.
- Full study guide on "Shock" and 4,913 more pages of the subject
- Assignments and quizzes after every topic — just like in a colloquium
- AI tutor answers questions on the topic anytime
- 135 video lessons on the subject
Other topics in "Chapter 20. Extreme and Terminal States"
Free video lessons: pathophysiologyShort lessons with lecture notes — no registration required.
Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.