Etiology and Classification
The underlying mechanism of collapse is a sudden and significant absolute or relative decrease in circulating blood volume (CBV) relative to the capacity of the vascular bed. Based on the initial pathogenic link, three main types are distinguished:
- Cardiogenic. Occurs due to an acute drop in cardiac output. Causes are divided into cardiac factors (acute heart failure secondary to valvular defects, severe tachycardia, or bradycardia) and factors obstructing venous return to the heart (embolism, valvular or pulmonary artery stenosis).
- Hypovolemic. Associated with a rapid reduction in CBV. It develops in massive hemorrhage, plasma loss (extensive burns), or severe dehydration (intractable vomiting, profuse diarrhea, excessive sweating, poisoning). This group also includes blood redistribution with pooling in veins and capillaries during shock, intoxications, or gravitational overloads.
- Vasodilatory. Caused by an acute drop in total peripheral vascular resistance. Blood vessels (arterioles and venules) lose tone due to endocrinopathies (adrenal insufficiency, hypothyroidism), drug overdoses (ganglionic blockers, sympatholytics, narcotics, calcium channel blockers), or humoral factors (hypocapnia, deep hypoxia, excess histamine, kinins, and adenosine).
In clinical practice, an etiological classification is also used, distinguishing infectious, toxic, radiation, pancreatic, post-hemorrhagic, and other forms. The rate of onset is heavily influenced by environmental factors (temperature, humidity, barometric pressure) and individual reactivity.
Pathogenesis and Organ Effects
Regardless of the etiology, the general pathogenesis leads to progressive tissue hypoperfusion. Initially, circulatory hypoxia occurs, followed later by hemic and tissue hypoxia. This triggers a cascade of multiorgan dysfunction:
- Cardiovascular System: Stroke volume and cardiac output decrease, venous stasis occurs, along with centralized circulation and capillariotrophic insufficiency. Coronary insufficiency develops.
- Nervous System: The patient becomes apathetic and lethargic, neuromuscular excitability decreases, and finger tremor or seizures may occur.
- Respiratory System: Tachypnea (rapid, shallow breathing) develops, with hypoxemia and hypercapnia detected in blood leaving the lungs.
- Kidneys: Excretory function is impaired—diuresis drops (oliguria), urine becomes concentrated (hypersthenuria), and blood levels of nitrogenous waste products increase (hyperazotemia).
- Blood System and Hemostasis: Blood viscosity increases, erythrocytes and platelets undergo hyperaggregation, leading to microthrombosis and sludge syndrome.
In severe cases, the liver is involved, leading to partial or total hepatic failure. To save the patient in hypovolemic collapse, emergency administration of blood components, packed red blood cells, plasma expanders, and solutions with ions and buffer systems is required. The body attempts to compensate for the loss by activating hematopoiesis.
Orthostatic Collapse
Orthostatic collapse warrants special attention. It occurs when a person transitions rapidly from a lying or sitting position to a vertical one, especially after prolonged physical inactivity (hypodynamia) or vestibular center irritation.
The initial trigger is systemic vasodilation—the walls of arterioles and capacitance vessels abruptly lose tone due to the dominance of cholinergic influences. The key pathogenic factor here is reduced vascular wall reactivity to vasopressors (angiotensin, catecholamines). This is frequently observed in adrenal insufficiency (glucocorticoid deficiency) or dysfunction of the cardiomotor center and hypothalamus.
Distinction from Syncope
In the International Classification of Diseases (ICD-10), syncope and collapse are grouped under the same rubric (R55), yet they are clinically distinct conditions.
Syncope (fainting) is a transient loss of consciousness caused by acute cerebral hypoperfusion. It begins acutely and is characterized by rapid spontaneous recovery of symptoms (within 5–25 seconds, rarely a few minutes).
In collapse, consciousness is not initially lost, although the patient may be severely lethargic or confused. However, progressive collapse can precipitate a syncopal episode.