Hemostasis: Approach to Patient Flashcards
What are the four events in platelet plug (primary hemostasis)?
- Platelet adhesion
- Platelet activation
- platelet aggregation
- Fibrin formation and support of local coag.
What are the major events in secondary hemostasis?
the platelet plug is stabilized by formation of a fibrin network generated through the coagulation cascade.
Name and explain the important platelet functions.
- adhesion- to the vascular subendothelium at sites of injury to begin the hemostatic process
- activation- platelets get activated and release intracellular granules to enhance platelet plug
- aggregation- to form platelet plug
- support of thrombin generation- by providing a phospholipid surface for the coag. cascade
In the PFA-100 test having a normal ADP and an abnormal Epi gives what result?
The aspirin effect- mild vW disease or platelet defect with low hct and low platelets
In the PFA-100 test having an abnormal ADP and an abnormal Epi gives what result?
Abnormal platelet function- very low hct and very low platelets
Do abnormal values of a PFA100 predict intraoperative bleeding risk?
No. She said it only helps to assess what their risk of bleeding might be. Which doesn’t entirely make sense but she had a red box around this point on her slides.
what does a big spleen mean for platelets?
increased risked for platelet sequestration because can keep a lot of platelets in there. splenomegaly–>splenic sequestration of platelets
platelets adhere to the vessel wall via ______ and ______
collagen and vWF
Where is glycoprotein Ib and what does it do?
It is on the platelet surface and it forms a temporary bond with the sub endothelial surface as platelets roll past injured vessels. This is one of the first steps in platelet adhesion.
Explain pharmacologically how aspirin changes the affect of platelets?
platelets secrete TXA2 as part of platelet activation. TXA2 is in the cyclooxygenase pathway which is inhibited by aspirin.
Explain in basic terms how platelets aggregate and get activated?
once platelets adhere they become activated and secrete cytokines. These attract other platelets which, upon attaching to the first platelets, will become activated and release more cytokines to continue the process.
How do you treat a patient with pseudothrombopenia?
Trick question fool! psuedothrombopenia is something that happens when the lab test doesn’t run properly. It is caused by a reaction with EDTA in the test tube and leads to platelet clumping. The point of this is to emphasize that you always check the smear when you get low platelet counts.
What are causes of thrombocytopenia?
- decreased production of platelets
- increased destruction of platelets
- distribution disorders (i.e. increased sequestration due to splenomegaly)
- Dilution (i.e. after a massive transfusion
Is vW disease (hereafter vWD) an acquired or a congenital disorder?
both.
it is the most common congenital bleeding disorder. It can be an acquired disorder if antibodies develop against the vWF molecule.
What are common findings that distinguish vWD from Hemophilia A?
vWD- mucocutaneous bleeding
Hemo A- big bleeds including in the retroperitineum, soft tissue, joint, and other deep bleeds
distinguish type 1, 2, 3 vWD
type 1- partial quantitative deficiency
type 2- qualitative defects
type 3- near complete absence of vWF
lack of vWD leads to abnormal __________ interaction.
platelet/endothelial
with severe vWD we will also see a functional _______ deficiency
factor VIII
If multiple cell lines are lowered including platelets we call it what? what else should you think about in this case?
pancytopenia. Have to worry about more serious stuff like MDS etc…
How do you treat the different types of vWD?
type 1- DDAVP- arginine vasopressin (this will not work however for type 2 and 3)
type 2 and 3- can use factor replacement sometimes
Common causes of decreased platelet count
- malignancies
- bone marrow failure
- nutritional deficiencies
- EtOH
- chemo/radiation
- viral/bacterial infection (with viral remember specifically Hep C and HIV)
Why is it that liver disease can cause abnormal clotting?
Many clotting factors are made there.
Why might type O blood people get over diagnosed with vWD?
they have a lower baseline vWF count from the start so if don’t correct for it can look like the disease when its not.
Glanzmann thrombasthenia is a disease caused by a defective _______.
GPIIb/IIIa
Immune thrombocytopenic purpura (ITP) is often preceded by _______ and is often associated with _______
a viral infection
concurrent autoimmune disorders
Make a diagnosis: Patient has negative bone marrow biopsy for malignancies, megakaryocytes are present at high numbers, no infections or meds, decreased platelet count.
ITP!
the antibodies are attacking the platelets.
Treatment options for ITP.
- steroids
- rituximab
- splenectomy
- IVIG
- IPO (thrombopoietin receptor agonist)
Causes of increased destruction of platelets?
ITP, DIC, TTP (thrombocytopenic purpura), autoimmune stuff (like lupus), sepsis
