Thromboembolic Disease & Shock-Parsa Flashcards
Intrinsic pathway of coagulation
Activated by thrombogenic surfaces, even glass
Extrinsic pathway of coagulation
- Involves tissue factor
* Requires Vitamin K
Common pathway of coagulation
Where intrinsic and extrinsic converge on factor ten (fX)
How can you inhibit thrombosis formation?
- Herparin-like molecules
- Thrombomodulin
- Tissue factor pathway inhibitor
- Endothelial cell-derived PGI2
How can you activate thrombosis formation?
- Endothelial injury
- Tissue factor
- Platelets
- Platelet-derived TxA2
How does aspirin prevent thrombosis?
By blocking platelet aggregation (TxA2 synthesis)
How does Coumadin prevent thrombosis?
Acts as an antagonist to Vitamin K which is a coagulation promoter
How does Heparin prevent thrombosis?
Inhibits coagulation
What is Heparin-Induced Thrombocytopenia (HIT)?
- Heparin binds with platelet factor 4 (PF4) which produces antibodies
- These antibodies bind to platelets and lead to thrombosis
How does Plasmin prevent thrombosis?
- Breaks down fibrin (clots)
* Drugs - streptokinase and urokinase
How does plasminogen activator (t-PA) prevent thrombosis?
Breaks break down already formed thrombi
What is Disseminated Intravascular Coagulation (DIC)?
- The sudden or insidious onset of widespread fibrin thrombi in the microcirculation
- Causes prolonged PT (prothrombin time)/PTT (partial thromboplastin time)
How is DIC activated?
• Release of thromboplastic substances into circulation
- Seen on OB complications, trauma and burns
• Widespread injury to endothelial cells
- Seen in G-sepsis
What is Microangiopathic Hemolytic Anemia (MAHA)?
The destruction of RBS in small vessels that are partially plugged by abnormal aggregates of fibrin and platelets
What is a schistocyte?
A fragmented red cell (resemble helmets)
What is an embolus?
- An embolus is a detached intravascular solid, liquid, or gaseous mass that is carried by the blood to a site distant from its point of origin
- It lodges in blood vessels and obstructs the flow of blood
Thromboemboli
- Venous side and lodges in lungs
* Arterial side resulting in ischemic changes in hands and feet
Paradoxical emboli
Emboli that originate in venous system → right heart and go thru a right-to-left passage (patent foramen ovale) in the wall between atria and ventricles (septal defect)(cause systemic effect).
Fat emboli
- From fat alone or hematopoietic cells from bone marrow.
- Due to bone fractures where fatty marrow gets into bloodstream.
- Destination: brain and skin.
Atheroma emboli
- Atherosclerotic plaque that embolizes following rupture.
* Example: after an angiogram.
Amniotic fluid emboli
• Amniotic fluid during delivery can embolize and kill the mother
Gas emboli
- From deep diving (dissolved nitrogen), rapid ascent leads to bubbles that clog up vessels in brain or lungs
- Also from delivery or abortion, accidental trauma in pneumothorax, and injury to chest
What is ischemia?
- Inadequate blood supply to a tissue
* Can result in infarction (red of white)
Local ischemia
Almost always caused by arterial obstruction due to atherosclerosis, thrombosis and embolism
What is ischemia dependent on?
- Collateral circulation
- Rate of development of obstruction
- Tissue susceptibility to ischemia
What is shock?
Prolonged systemic hypoperfusion resulting from insufficient cardiac output or reduction in the effective circulating blood volume
Hypovolemic shock
- Large reduction in intravascular blood volume
* Causes: diarrhea and vomiting (fluid loss), hemorrhage (blood loss) and burns (plasma loss)
Cardiogenic shock
- Pump failure
* Causes: massive pulmonary embolism or massive MI
What are the 3 way general vasodilation can occur?
- Anaphylactic shock
- Neurogenic shock
- Septic shock
Anaphylactic shock
A severe, allergic Type I Hypersensitivity reaction caused by degranulation of mast cells
Neurogenic shock
May occur secondary to spinal cord trauma, brain injury or use of general anesthesia causing loss of vascular tone
Septic shock
Caused by infectious agents, usually associated with endotoxin producing Gram- bacilli
What are the 3 stages of shock?
- Compensation
- Impaired tissue perfusion
- Decompensation
Compensation
- Non-progessive
- Sympathetic reflex
- Increased HR, peripheral vasoconstriction, sweating, rapid shallow breathing, cold, clammy and diminishing urine output
Impaired tissue perfusion
- Progressive
- Excessive vasoconstriction impairs tissue perfusion resulting in hypoxia and impaired fluid exchange
- Lots of organs get anoxic
Decompensation
- Irreversible
* Complete loss of reflex vasoconstriction, kidney failure, extremely low cardiac output, cerebral hypoxia, and death
