Secondary Hemostasis Flashcards
What are clinical features of secondary hemostasis? How is it assessed in the laboratory?
Clinical features include deep tissue bleeding into muscles and joints (hemarthrosis) and re bleeding after surgery.
Lab studies include
1. Prothrombin time - measures extrinsic and common pathway
2. Partial thromboplastin time - measures intrinsic and common pathway
What are the products of the coagulation cascade? Where are the coagulation factors produced? What three things are required for their activation?
Thrombin is converted to fibrinogen which is converted to fibrin which is cross linked to yield a stable platelet fibrin thrombus. They are produced in the liver in an inactive state. Activation requires
- Exposure to tissue thrombo plastin to activate factor 7 for extrinsic pathway and sub endothelial collagen to activate factor 12 for the intrinsic pathway
- Phospholipid surface of platelets
- Calcium from dense platelet granules
What is the difference between hemophilia A and B?
Hemophilia A is factor 8 deficiency and hemophilia B (Christmas disease) is factor 9 deficiency. They have simile presentations.
A 37 year old model who underwent surgical procedure presents with bleeding in her joints. Upon doing some testing, you find that she is deficient in factor 8. What disease does she have? How is it inherited and who does it affect usually? What are some lab findings? How would you treat her?
She has hemophilia A which is X linked recessive and predominantly affects males. Can also be denovo mutation. Lab findings include increased PTT, normal PT, normal platelet count and bleeding time, low factor 8 which has to be supplemented by recombinant factor 8.
How do you identify if there is a coagulation factor inhibitor? How does it arise?
PTT does not correct upon mixing normal plasma with patient’s plasma due to inhibitor. Mimics hemophilia A especially since most cases are factor 8 inhibition due to acquired antibody against it.
A 24 year old tennis player presents to your clinic with complaints of bleeding in the mouth. She also has bleeding on her skin. Genetic studies shows that she has an inherited coagulation disorder. What could it be? What is the inheritance pattern? What are some lab findings? How would you treat?
She has a genetic vWF disorder which is autosomal dominant with decreased vWF levels. This impairs platelet adhesion. Lab findings include increased bleeding time, increased PTT because vWF stabilizes factor 8. Normal PT. Ristocetin test is abnormal because agglutination will be impaired due to lack of vWF. Treat with Desmopressin which increases vWF release from Weibel-Palade bodies of endothelial cells.
Where is vitamin K activated? Which factors does it gamma carboxylase? Which three areas is deficiency seen?
Activated in liver by peroxide reductase. Gamma carboxylates factors 2,7,9,10 and proteins C and S. Deficiency occurs in a. New borns due to lack of GI colonization by bacteria where vitamin aka is produced b. Long term antibiotic activity c. Malabsorption.
What are other causes of abnormal secondary hemostasis.
Liver days function and large volume transfusion which dilutes coagulation factors.
