Hemostasis: Approach to Patient Flashcards
Primary hemostasis is _________.
platelet plug formation
One megakaryocyte can divide into ________ platelets.
2,000
Platelets can circulate for _______ in the bloodstream.
7-10 days
Platelet maturation (from hematopoietic stem cells) is induced by _________.
thrombopoietin
Following damage to the endothelium, _____ (on the platelets) bind _______ (in the sub-endothelium).
GPIb; von Willebrand factor
What platelet receptor binds to both vWF and fibrinogen?
GPIIb/IIIa
Safe platelet count for surgery is generally > ___________.
50,000
What are the categories of thrombocytopenia?
(1) increased destruction; (2) decreased production; (3) increased sequestration; and (4) pseudo-thrombocytopenia, when platelets aggregate on the slide
Infection–both viral and bacterial–can cause __________.
thrombocytopenia
Marrow production can be affected by __________.
ETOH, malignancies, chemotherapy, radiation, viral infections, and nutritional deficiencies
What is ITP?
Immunogenic Thrombocytopenia Purpura (formerly known as idiopathic thrombocytopenia purpura); it can happen acutely, following viral infection, or chronically, often accompanied by HIV, autoimmune, or malignancy
How is ITP treated?
With steroids (to dampen the immune response), rituximab (to kill B cells and lower the amounts of IgG), or splenectomy (to remove the site of sequestration
The most common congenital bleeding disorder is ________.
von Willebrand disease
Patients with von Willebrand disease present with _________.
mucosal bleeding, nose bleeding, GI bleeds, menorrhagia, and bleeding after surgery
Besides adhering platelets to collagen, vWF also ________.
carries factor VIII, and without vWF factor VIII has a short half life
The most common type of VWD is _________.
partial quantitative defect of vWF (complete absence is rare)
In patients with a normal spleen, what percent of platelets are circulating?
80%
What procoagulant proteins do alpha granules contain in platelets?
Factor V, fibrinogen, and von Willebrand factor
What role do platelets play in coagulation?
They (1) bind to sub-endothelial collagen and clog sites of injury; (2) activate receptors to interact and form the primary plug; (3) activate phosphatidylserine lipids to serve as sites of extrinsic tenase, intrinsic tenase, and prothrombinase activity; and (4) they release factor V, von Willebrand factor, and fibrinogen from their granules
Describe the role of thromboxane A2 in platelet activation.
Platelet activation stimulates phospholipase A2 that cleaves off arachidonic acid; arachidonic acid then is converted to thromboxane A2 by COX1 and then activates other platelets.
Glanzmann thrombasthenia is __________.
a rare autosomal recessive bleeding disorder in which patients lack GPIIb/IIIa; it causes easy bruising and petechiae
Plavix (clopidogrel) and Ticlid (ticlopidine) are _________.
ADP receptor antagonists
Immunogenic thrombocytopenic purpura is caused by ____________.
IgG against platelet antigens; acute cases (often following viral infection) usually auto-resolve; chronic cases don’t
Thrombotic thrombocytopenic purpura results from __________.
damage to endothelial cell walls that leads to micro-clotting throughout the body and eventual consumption of platelets
Multiple bleeding sites suggest _________, while mucocutaneous bleeding sites suggest ___________.
general hemostatic disorder; platelet dysfunction
