Classification by etiology
Depending on the factors causing the blood flow disturbance, four main types of arterial anemia are distinguished:
- Angiospastic. Occurs due to arterial spasm triggered by neural, hormonal, or pharmacological influences (for example, in stress, angina pectoris, or appendicular colic). The pathogenesis is dominated by an excess of vasopressor agents in the blood: angiotensin II, vasopressin, and catecholamines. The course is always acute.
- Obstructive. Associated with partial or complete closure of the arterial lumen from within. The acute form is triggered by a thrombus or embolus, while the chronic form is driven by the gradual growth of an atherosclerotic plaque.
- Compressive. Develops when a vessel is compressed from the outside. Causes may include a tourniquet, severe edema, or a growing tumor. The process can be either acute or chronic.
- Redistribution. Occurs after the rapid relief of external compression (for example, upon rapid removal of ascitic fluid or a large tumor). Blood rushes abruptly into previously ischemic vessels, depriving neighboring organs. The course is always acute.
Clinical and pathophysiological manifestations
The symptoms of ischemia directly depend on reduced blood supply and profound microcirculatory disorders. The ischemic area undergoes a series of characteristic changes:
- Pallor and local hypothermia. The organ becomes pale due to the constriction of superficial vessels and a decrease in the number of functioning capillaries. Tissue temperature drops because the inflow of warm arterial blood decreases and oxidative processes are suppressed (heat production falls).
- Hemodynamic shifts. Arterial pulsation weakens. Hydrodynamic pressure drops, and the linear and volumetric blood flow velocities decrease. Arteries, veins, and microcirculatory vessels constrict. A sharp drop in capillary pressure ultimately leads to the cessation of blood movement — stasis.
- Decreased turgor and volume. The tissue becomes flabby, and the organ itself decreases in size. This happens due to a drop in vascular filtration and the loss of intercellular fluid.
- Impaired lymph circulation. Lymph formation and lymphatic drainage processes are significantly weakened.
- Pain syndrome and paresthesias. Patients experience numbness, tingling ("pins and needles"), and severe pain. Pain arises from the accumulation of specific mediators in the hypoxic zone: kinins, histamine, prostaglandins, potassium ions ($K^+$), as well as lactic and pyruvic acids.
Morphology and outcomes of ischemia
The basis of any damage in ischemia is hypoxia. The nature and severity of morphological changes depend on the duration and degree of anemia, the presence of collateral vessels, and the sensitivity of the specific organ to oxygen deprivation.
- In acute ischemia, dystrophic and necrotic changes develop rapidly in tissues (infarction forms).
- In chronic ischemia, the process is slower: collateral circulation manages to form, which partially compensates for hypoxia. As a result, atrophic and sclerotic changes come to the forefront.
A huge role is played by the functional state of the organ, which determines the intensity of metabolism and oxygen demand. The higher the functional activity, the more severe the damage. This principle is used in medicine: for example, artificial hypothermia reduces the tissue demand for $O_2$, allowing cardiac surgery to be performed safely under conditions of cardiopulmonary bypass.
Briefly: answers to topical questions
What types of infarctions by color (macroscopic appearance) form during acute ischemia in various organs?
Based on macroscopic appearance, three main types of infarctions forming in various organs are distinguished.
- White (ischemic, bloodless) — occurs in the spleen and brain.
- White with a hemorrhagic rim — characteristic of the heart (myocardium) and kidneys. The rim is formed due to the zone of demarcation inflammation at the tissue border.
- Red (hemorrhagic) — develops in the lungs, intestines, ovaries, and brain. The mechanism is associated with the impregnation of necrotic tissues with blood during venous congestion or dual blood supply.
A rare dark red or black red (venous) infarction of the spleen is also distinguished.
What sequential stages of morphogenesis does an infarction undergo?
The classical morphogenesis of an infarction includes three sequential stages.
- Ischemic (pronecrotic) — metabolic disorders and energy deficits increase. The stage is reversible with timely reperfusion.
- Necrotic — development of the necrosis focus itself.
- Organization stage (scarring) — scar formation.
In cerebral infarction, microscopic changes go through the following stages: development of necrosis, softening or resorption (onset of organization), and formation of a glio-mesodermal scar (or cyst).
To memorize the causes of ischemia, use the acronym SOCI: Spasm (angiospastic), Obstruction (closure from within), Compression (external pressure), Irradiation/Redistribution (outflow to adjacent zones).
Class and exam questions
Why does severe pain occur in ischemia?
Under conditions of hypoxia, pain mediators accumulate in tissues: lactic and pyruvic acids, histamine, kinins, prostaglandins, and potassium ions. They irritate nerve endings, causing pronounced pain syndrome.
Which organs are most sensitive to arterial anemia?
The brain has the highest sensitivity. It is followed in decreasing order of vulnerability by the kidneys and myocardium. The lungs and liver are also classified as sensitive organs.
How do the outcomes of acute and chronic ischemia differ?
Acute ischemia leads to rapid dystrophic changes and tissue necrosis. Chronic ischemia proceeds more slowly, is accompanied by the development of collaterals, and ends with cell atrophy and their replacement by connective tissue (sclerosis).
What else to study on this topic
- Mechanisms of thrombus and embolus formation in acute obstructive ischemia.
- Pathogenesis of stasis development in microcirculatory vessels.
- The role of vasopressor agents (angiotensin II, catecholamines) in the development of angiospasm.
- Infarction as the ultimate manifestation of acute ischemia: types and morphology.
- Features of collateral circulation formation in chronic anemia.
Master the entire topic in the "Pathological Anatomy" course
This is a summary. The course covers everything tested in classes and exams.
- Complete study guide on "Ischemia" and 4,414 other subject pages
- Assignments and quizzes after every topic — just like in a colloquium
- AI tutor answers questions on the topic anytime
- 153 video lessons on the subject
Other topics in the section "Disorders of Blood and Lymph Circulation"
Free video lessons: pathological anatomyShort lessons with study notes — no registration required.
Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.