Ischemia and stasis – classification, etiology, pathogenesis, and clinical manifestations.
I. Ischemia
Ischemia is a local reduction or complete interruption of blood supply to a tissue, resulting in inadequate delivery of oxygen and nutrients and impaired removal of metabolic waste.
Classification
Etiology
- Arterial thrombosis or embolism.
- Severe vasospasm (e.g., Raynaud phenomenon).
- External compression (e.g., tumor, tight bandage).
- Atherosclerotic stenosis.
- Mechanical factors (volvulus or hernia in bowel ischemia).
Pathogenesis
- Decreased blood supply → reduced oxygen (hypoxia) and nutrient delivery.
- Impaired ATP production → shift to anaerobic glycolysis → lactic acidosis.
- Ion pump failure → cell swelling, calcium influx → activation of degradative enzymes.
- If prolonged → irreversible cell injury → infarction.
Clinical manifestations
- Pain (sharp and severe in acute ischemia).
- Pallor (due to lack of blood).
- Paresthesias (tingling, numbness).
- Pulselessness.
- Poikilothermia (coldness).
- Paralysis (in severe cases).
Classic "6 Ps" of acute limb ischemia:
II. Stasis
Stasis refers to slowing or stagnation of blood flow in vessels, usually in veins and capillaries.
Classification
Etiology
- Prolonged immobility (e.g., bed rest, long flights → DVT risk).
- Chronic heart failure → venous congestion.
- Varicose veins.
- External compression of veins (casts, tight dressings).
Pathogenesis
- Reduced or stagnant blood flow → increased hydrostatic pressure.
- Fluid transudation into interstitium → edema.
- Decreased oxygen delivery and impaired removal of metabolic waste → local hypoxia.
- Endothelial damage → increased risk of thrombosis (part of Virchow’s triad).
Clinical manifestations
- Edema (especially in dependent areas, e.g., ankles).
- Cyanosis (bluish discoloration due to deoxygenated blood pooling).
- Heavy or aching sensation in legs.
- Increased risk of skin ulcers and infections (stasis dermatitis).
- Predisposition to thrombosis.