Flashcards in Hematology - Hemostasis 1 Deck (57)
What are the stages of hemostasis?
Primary, secondary, and tertiary hemostasis
What occurs during primary hemostasis?
The formation of the platelet plug
What is primary hemostasis sufficient for?
small vessel injury
What occurs during secondary hemostasis?
The formation of the fibrin clot through the coagulation cascade
What is secondary hemostasis needed for?
medium/large vessel injury
What occurs during tertiary hemostasis?
Fibrinolysis to re-establish blood flow through vessels
What clinical signs are associated with primary hemostatic defects?
Mucosal surface bleeding: petechiae, ecchymoses, epistaxis, hemoptysis, hematuria, hematemesis, melena, hematochezia, ocular bleeding, and CNS bleeding
What are the key cellular players in primary hemostasis?
endothelial cells and platelets
What are the key protein adhesive agents in primary hemostasis?
Von Willebrand factor (vWF), collagen, and fibrinogen
What are the key protein agonist agents in primary hemostasis?
ADP, thromboxane A2 (TXA2), and thrombin
What prevents platelet adhesion in the normal vessel?
Negatively charged endothelium, NO, prostacyclin, and ADPase
When subendothelium is exposed, what occurs during primary hemostasis?
von Willebrand facort binds to the subendothelium, a platelet enzyme binds to the subendothelial vWF, and the aggregation receptor becomes activated. Then another receptor binds to fibrinogen and in simple terms, more platelets are recruited and aggregate.
How do activated platelets set stage for secondary hemostasis?
Activated platelets flip their membranes which exposes phosphatidylserine and then provide a docking site for clotting factors needed in secondary hemostasis
Generally, what can go wrong with primary hemostasis?
Low platelet number, impaired platelet function, deficient vWF number, impaired vWF function
What is the most common acquired disorder of primary hemostasis?
What can cause thrombocytopenia?
Use, destruction, and decreased production
What inherited disorder can lead to thrombocytopenia?
What breeds is congenital macrothrombocytopenia common in?
Cavalier King Charles Spaniels, Norfold Terriers, and others
What occurs in congenital macrothrombocytopenia?
The patients don’t bleed because their platelets are too big
What are common acuired causes of thrombocytopenia?
Immune-mediated, infectious disease, DIC, and drugs
What is thrombopathia?
What are the forms of thrombopathia?
inherited and acquired
What are the acquired causes of thrombopathia?
DIC, renal and liver disease, and drugs
What is the most common inherited primary hemostatic disorder?
von Willebrand's disease
What breeds is vWD most common in?
Dobermans, German shorthaired pointers, scottish terriers, and many others
If you suspect a hemostatic defect, what testing should be done?
Platelet count and coagulation profile
How do you estimate the platelet count from a blood smear?
count in a 100x field - 1 per field equals 20,000 platelets/ul
At what platelet count will spontaneous bleeding occur?
Less than 30,000
How do you do vWD testing?
With vWF:Ag testing