Vascular Disorders & Thrombosis 5 Flashcards
Active increased blood flow into microvasculature is also called…
Hyperemia
Passive accumulation of blood due to decreased outflow is also called…
Congestion
Decreased tissue perfusion is also called…
Ischemia
(This results in coagulative necrosis/infarction!)
What is the macroscopic appearance of hyperemia?
Tissue appears bright red and warm
Acute heart failure, GDV, and euthanasia are all causes of which type of congestion?
Acute passive congestion
Chronic left-sided heart failure and chronic right-sided heart failure are both causes of which type of congestion?
Chronic passive congestion
What is the macroscopic appearance of congestion?
Tissue appears dark red and swollen
Inadequate tissue perfusion which occurs when metabolic needs of the tissues are not met; typically caused by vascular obstruction, congestion, or decreased cardiac output
Ischemia
What are three factors that determine tissue susceptibility to ischemia and infarct?
- Anatomy of vascular supply
- Rate of occlusion
- Tissue vulnerability to hypoxia
Which organs are most susceptible to ischemia and infarct, due to having high metabolic needs and poor collateral circulation?
Brain and heart
Which organs are only at a moderate risk for ischemia and infarct, due to generally receiving more blood than they need under normal conditions?
Lungs, GI tract, kidneys, skin
Which organs are least susceptible to ischemia and infarct, due to only receiving blood based on immediate needs under normal conditions?
Skeletal muscle
Rank these 3 tissues based on their susceptibility to hypoxia (from most to least susceptible):
Myocardial cells, neurons, fibroblasts
- Neurons (death after 3 to 4 minutes)
- Myocardial cells (death after 20 to 30 minutes)
- Fibroblasts (remain viable after several hours of hypoxia)
True or False: Reperfusion after a brief period of ischemia can result in a full recovery
True
Reperfusion after a prolonged period of ischemia causes inflammation and oxidative damage, which is also called ___________ ________.
Reperfusion injury
What occurs if ischemia is not corrected?
Tissue necrosis (infarct)
A depressed, tan, firm, fibrotic infarct
Chronic pale infarct
An angular/wedge-shaped area of infarct with an occluded vessel at the base; swollen/dark red (hemorrhagic) or tan
Acute hemorrhagic infarct
Systemic hypotension due to reduced cardiac output or reduced blood volume
Shock (cardiovascular collapse)
What is the pathogenesis of shock (cardiovascular collapse)?
- Hypotension causes impaired tissue perfusion and cellular hypoxia
- Result: anaerobic metabolism, cell injury, and cell death
What are the three general categories of shock (cardiovascular collapse)?
- Cardiogenic shock (circulatory shock)
- Hypovolemic shock
- Blood maldistribution (vasogenic shock)
Shock that occurs due to failure of the heart to adequately pump blood; causes include myocardial infarct, arrhythmia, cardiomyopathy, and obstruction of blood flow
Cardiogenic shock
GDV is a catalyst for ___________ shock, because it causes obstruction of blood flow
Cardiogenic
What is the pathogenesis of GDV?
- Gastric dilation causes gastric volvulus & splenic/esophageal displacement, leading to venous infarct in gastric mucosa
- Ischemia & necrosis set in, which decreases venous return via portal vein/caudal vena cava
- Reduced perfusion of intra-abdominal organs & reduced cardiac output causes cardiogenic shock, then death
Shock that occurs due to blood loss from hemorrhage or fluid loss from V+, D+, and severe burns
Hypovolemic shock
The most common malignant tumor of the canine spleen involving neoplasm of the endothelium; single to multiple discrete to coalescing splenic masses; can cause hemoabdomen; poor prognosis, metastasis common
Splenic hemangiosarcoma
What is the pathogenesis of splenic hemangiosarcoma?
- Ruptured splenic hemangiosarcoma leads to hemoabdomen, resulting in severe blood loss
- Severe blood loss causes hypovolemic shock
Shock due to decrease in peripheral vascular resistance with pooling of blood in peripheral tissues due to anaphylaxis, sepsis, etc.
Blood maldistribution
What type of hypersensitivity is anaphylactic shock?
Generalized type I hypersensitivity
What is the pathogenesis of anaphylactic shock?
- IgE binds to mast cells, causing widespread mast cell degranulation & release of vasoactive mediators
- Systemic vasodilation occurs, which increases vascular permeability
- Result: hypotension & tissue hypoperfusion
What causes septic shock?
(Think at the microbial level)
Gram-positive / gram-negative bacteria, and fungi
What is the pathogenesis of septic shock?
- Gram-neg bacteria release microbial substances (especially LPS), and this causes endothelial activation and injury (vascular leakage)
- Leukocytes are stimulated to release inflammatory cytokines, activate complement, and promote coagulation
- Result: vasodilation, hypotension, tissue hypoperfusion
What are the 3 stages of shock?
- Non-progressive stage (compensatory) (inc cardiac output)
- Progressive stage
- Irreversible stage
What occurs during the non-progressive stage of shock?
Compensatory mechanisms activate and vital organ perfusion is maintained (tachycardia, peripheral vasoconstriction, renal fluid conservation)
What occurs during the progressive stage of shock?
Peripheral vasodilation and blood pooling, tissue hypoperfusion & hypoxia, metabolic derangement (like acidosis), and cell necrosis
(Compensatory mechanisms no longer adequate)
What occurs during the irreversible stage of shock?
Widespread peripheral vasodilation, anaerobic metabolism, severe cellular and tissue injury leads to multiple organ dysfunction, then DIC and eventually death
(This stage is the point of no return - repair not possible)
