Hemostasis Flashcards
Hemostasis
Stopping blood loss in response to vascular injury
Steps of hemostasis
- vascular constriction
- formation of platelet plug
- formation of the blood clot
- Fibrous organization
Vascular constriction
Reduces blood flow to site of injury
Formation of platelet plug
Adhesion and aggregation of platelets at the site of injury
What two factors aid in formation of platelet plug
vWF and fibrinogen
Formation of a blood clot
Fibrinogen is converted to fibrin which then adheres more firmly to the platelets (sticky). Blood is also transformed into a gel
Fibrous organization
Fibrin mesh is produced all around the platelet plug and holds this in place, eventually goes into fibrinolysis (which breaks down the clot and allows for normal blood flow to resume)
Petechiae
Small red or purple spot caused by bleeding into the skin
Purpura
A rash of purple spots on the skin caused by internal bleeding from small blood vessels
Vasculitis
Inflammation of blood vessels (thickening, wearing down, narrowing, scarring)
hematoma
Solid swelling or mass of clotted blood within the tissue
Ecchymosis
Discoloration of the skin due to bleeding underneath (usually internal structural bleeding)
Thrombosis
Local coagulation or clot in circulatory system
Embolism/thromboembolism
The obstruction of a blood vessel due to a blood clot or foreign substance that lodges itself in vessel. Migrates from some place else (PE)
Infarction
Tissue death (necrosis) due to lack of O2
What is the big cell that makes platelets
megakaryocytes
What is the life span of a platelet
7-10 days
What factor do platelets contain
vWF
What is the role of vWF
acts as the glue in platelet plug
What is the initial step of the platelet in clotting
Adherence to collagen on the surface of injured vessel
What does collagen do at site of injury
It triggers the activation of the platelets which causes them to adhere and aggregate to each other
Which factor converts prothrombin to thrombin
Factor X(a)
Where does conversion of prothrombin to thrombin occur during the pathways
It occurs where intrinsic and extrinsic join
What catalyzes the conversion of fibrinogen to fibrin
Thrombin. It stabilizes and solidifies the aggregates
Primary hemostasis
Platelet plug formation
Secondary hemostasis
Coagulation of fibrin
Fibrinolytic system
Breaks the fibrinogen clot in order for blood flow to be reestablished once vessel is healed
What is vitamin K involved in forming
- Prothrombin
- Factors VII, IX, and X
- Protein C
Where do you get vitamin K from
- Normal diet
2. Bacteria in the gut
Which blood test measures intrinsic pathway factors
PTT
Which blood test measures extrinsic pathway factors
PT
What affect will a vitamin K deficiency have
Will cause an increase in PT and PTT because it changes the way the pathways function (basically an increase in bleeding, clotting cascade not working properly)
Hemophilia
Severe bleeding disorders
Hemophilia A
Factor VIII deficiency
Hemophilia B
Factor IX deficiency
vWF role in disorders
most common cause of bleeding disorders (when absent), aids w/platelet adhesion
DVT
Thrombus occurs in lower extremity vein, can detach and travel to lungs (PE)
Thrombocytopenia
Abnormally low platelet count in blood stream. Usually anything below 50,000. Pt will not clot properly. Very asymptomatic but may have frequent nosebleeds or petechia
Pulmonary embolism
An embolus, meaning it is a clot that has migrated to the lungs from other parts of the body. Usually comes from the lower legs
Disseminated intravascular coagulation (2 step process)
- Starts when there is over activation of clotting cascade, results in blood clots in small blood vessels (organ damage)
- As the coagulation cascade consumes these clotting factors, normal clotting is disrupted elsewhere and severe bleeding can occur
Bleeding time
Measures platelet function. Make a small incision on pt forearm (2-9mins)
Platelet count
Only test that determines platelet number and concentration (150,000-450,000)
partial thromboplastin time (PTT)
Measurement of the intrinsic pathway. Assess the patients response to heparin.
Prothrombin time (PT)
Measurement of the extrinsic pathway. Assess the patients response to coumadin/calcium
D-dimer
Test for DVT/PE but better to rule out than rule in. Tests the fibrin degradation product in the blood (this occurs after the breakdown of clot)
Platelet function test
Measures the ability of the platelets to aggregate. Helps identify bleeding disorders
What mechanisms prevent excess thrombosis
- TFPI - inhibits extrinsic pathway
- Antithrombin 3 - inhibits VII, IX, XI and thrombin
- Activated protein C (w/protein S) - inhibits X and thrombin
- Plasmin - fibrinolysis
Adhesion
1st step in blood clot formation, platelets stick to endothelium
Aggregation
2nd step in blood clot formation. Platelets clump together due to fibrin
Spreading
3rd step in blood clot formation, platelets change shape, becomes more gel like
What factors contribute to developing pathologic thromboses
- Congenital
- Acquired -cancer, anemia, IBS
- Fibrinolytic abnormalities
- Situational - prolonged immobilization, pregnancy, surgery, birth control
What are two compounds that are involved in fibrinolysis
urokinase, tPA
