4.1 Primary Hemostasis and Related Bleeding Disorders Flashcards
What is the function of primary hemostasis?
Formation of a weak platelet plug
What is the function of secondary hemostasis?
Stabilization of the platelet plug formed in primary hemostasis
What are the 2 sources of von Willebrand’s Factor?
- Platelets
- Endothelial cells in the Weibel-Palade body
What is the protein that binds the platelets to vWF?
GP Ib
What is the first response to blood vessel damage?
Vasoconstriction
After vasoconstriction in response to injury, what occurs next?
vWF will bind to collagen on the disrupted tissue and then platelet adhesion to vWF will occur via GP Ib binding
What happens to the platelets after adhesion?
Adhesion will lead to platelet activation with a change in the conformation of the platelets and lead to the release of ADP which will expose GP IIb/IIIa and TXA2, which will promote platelet aggregation
What occurs during platelet aggregation?
Platelets link to each other with GP IIb/IIIa via fibrinogen and form a weak platelet plug, marking the end of primary hemostasis.
What are the 2 major types of primary hemostasis disorders?
Quantitative and Qualitative
What is the major symptom of primary hemostasis disease?
Skin and mucosal bleeding - epistaxis is a major one
What is immune thrombocytopenic purpura (ITP)?
Autoimmune disease where IgG is made in the spleen against GP IIb/IIIa
Who gets ITP most often?
The acute form is most often found in children.
The chronic form is most often found in adult women.
What are the lab findings in ITP?
- Decreased platelet count
- Normal PT/PTT
- Increased megakaryocytes in bone marrow
What is microangiopathic hemolytic anemia?
Pathologic formation of platelet micro thrombi in small vessels which consumes the platelets and leads the the shearing of the RBCs
With what other syndromes is microangiopathic hemolytic anemia seen with?
Thrombotic Thrombocytopenic Purpura
Hemolytic Uremic Syndrome
What is the cause of TTP?
Due to decreased ADAMTS13 which normally cleaves vWF multimers into monomers. The multimers will lead to abnormal platelet adhesion and result in the micro thrombi
What are the general findings of TTP and HUS?
Skin and mucosal bleeding
Microangiopathic hemolytic anemia
Renal failure (HUS)
CNS abnormalities (TTP)
What is Bernard-Soulier Syndrome caused by?
GP Ib defect that impair platelet adhesion to vWF
What is Glanzmann Thrombasthenia cause by?
GP IIb/IIIa defect that impairs platelet aggregation
What is the effect of uremia on platelets?
Uremia disrupts platelet function so both adhesion and aggregation are impaired
