Lecture 7: Thrombosis and Hemostasis Flashcards
What is the most common cause of bleeding?
Thrombocytopenia
Which pathway does the prothrombin time (PT) assess; deficiencies of which factors and drugs cause prolongation?
- Extrinsic pathway
- Prolonged in deficiencies of Factors II, V, VII, and X as well as fibrinogen
- Prolonged in pt’s taking warfarin or dicoumarol
Which pathway does the partial thromboplastin time (PTT) assess; deficiencies of which factors and drugs cause prolongation?
- Assesss the intrinsic system
- Prolonged in deficiencies of factors VIII, IX, XI, XII (8, 9, 11, 12)
- Prolonged in pt’s on heparin
Platelet aggregation studies are important in determining what defects?
Platelet abnormalities when platelets are normal in numbers i.e., “qualitative platelet defects”
What is the most common cause of abnormal platelet function?
- Meds such as aspirin or NSAIDS due to impaired arachidonate metabolism
- Very important to make sure pt has not taken these drugs for at least 7 days prior to doing a platelet aggregation study
What is the utility of using a 1:1 mixing study in pt with bleeding abnormality?
- Differentiates factor deficiency from presence of a factor inhibitor by mixing pt plasma w/ normal plasma
- Factor deficiencies will correct with mixing
What is the diagnostic testing utilized for Von Willebrand Disease (wWD)?
- Platelet function analysis (PFA) –> may be normal in mild cases
- vWF antigen level, vWF activity assay, factor VIII level
- Platelet aggregation tests are abnormal –> especially to ristocetin
What is first-line tx for Von Willebrand Disease (wWD); what else can be given?
- Desmopressin; administered IV or intranasally
- Can give intermediate-purity factor VIII concentrates, which contain vWF
- Cryoprecipitate is rich in wWF but carries risk of transfusion-transmitted infection!
In regards to Hemophilia A and B, what does the term “target joints” refer to?
One or two joints that patients have recurrent bleeds into
Acquired inhibitors of coagulation factors are most likely to manifest how clinically?
As a life-threatening bleed; pt’s may present w/ severe soft tissue bleeding, but not hemarthrosis
Acquired inhibitors of coagulation is often seen in association with what meds and underlying disorders?
- Meds = phenytoin, sulfa drugs, and penicillin
- Autoimmune disorders = SLE and RA
Long-term management of acquired inhibitors of coagulation requires what therapy?
Immunosuppressive therapy
Which laboratory test for coagulopathy is sensitive indicator of hepatic synthetic function?
PT; due to the short half-life of factor VII, which a failing liver cannot maintain
Which therapy is useful in liver disease if the the fibringoen level is <100 mg/dL?
Cryoprecipitate
Which clotting factors and proteins requires Vitamin K-dependent gamma-carboxylation for full activity?
Factors II, VII, IX, and X, as well as protein C and protein S