Hemostasis: Approach to Patient

Question 1

What are the four events in platelet plug (primary hemostasis)?

Answer 1

• Platelet adhesion
• Platelet activation
• platelet aggregation
• Fibrin formation and support of local coag.

Question 2

What are the major events in secondary hemostasis?

Answer 2

the platelet plug is stabilized by formation of a fibrin network generated through the coagulation cascade.

Question 3

Name and explain the important platelet functions.

Answer 3

• 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

Question 4

In the PFA-100 test having a normal ADP and an abnormal Epi gives what result?

Answer 4

The aspirin effect- mild vW disease or platelet defect with low hct and low platelets

Question 5

In the PFA-100 test having an abnormal ADP and an abnormal Epi gives what result?

Answer 5

Abnormal platelet function- very low hct and very low platelets

Question 6

Do abnormal values of a PFA100 predict intraoperative bleeding risk?

Answer 6

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.

Question 7

what does a big spleen mean for platelets?

Answer 7

increased risked for platelet sequestration because can keep a lot of platelets in there. splenomegaly–>splenic sequestration of platelets

Question 8

platelets adhere to the vessel wall via ______ and ______

Answer 8

collagen and vWF

Question 9

Where is glycoprotein Ib and what does it do?

Answer 9

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.

Question 10

Explain pharmacologically how aspirin changes the affect of platelets?

Answer 10

platelets secrete TXA2 as part of platelet activation. TXA2 is in the cyclooxygenase pathway which is inhibited by aspirin.

Question 11

Explain in basic terms how platelets aggregate and get activated?

Answer 11

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.

Question 12

How do you treat a patient with pseudothrombopenia?

Answer 12

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.

Question 13

What are causes of thrombocytopenia?

Answer 13

1. decreased production of platelets
2. increased destruction of platelets
3. distribution disorders (i.e. increased sequestration due to splenomegaly)
4. Dilution (i.e. after a massive transfusion

Question 14

Is vW disease (hereafter vWD) an acquired or a congenital disorder?

Answer 14

both.

it is the most common congenital bleeding disorder. It can be an acquired disorder if antibodies develop against the vWF molecule.

Question 15

What are common findings that distinguish vWD from Hemophilia A?

Answer 15

vWD- mucocutaneous bleeding

Hemo A- big bleeds including in the retroperitineum, soft tissue, joint, and other deep bleeds

Question 16

distinguish type 1, 2, 3 vWD

Answer 16

type 1- partial quantitative deficiency
type 2- qualitative defects
type 3- near complete absence of vWF

Question 17

lack of vWD leads to abnormal __________ interaction.

Answer 17

platelet/endothelial

Question 18

with severe vWD we will also see a functional _______ deficiency

Answer 18

factor VIII

Question 19

If multiple cell lines are lowered including platelets we call it what? what else should you think about in this case?

Answer 19

pancytopenia. Have to worry about more serious stuff like MDS etc…

Question 20

How do you treat the different types of vWD?

Answer 20

type 1- DDAVP- arginine vasopressin (this will not work however for type 2 and 3)
type 2 and 3- can use factor replacement sometimes

Question 21

Common causes of decreased platelet count

Answer 21

• malignancies
• bone marrow failure
• nutritional deficiencies
• EtOH
• chemo/radiation
• viral/bacterial infection (with viral remember specifically Hep C and HIV)

Question 22

Why is it that liver disease can cause abnormal clotting?

Answer 22

Many clotting factors are made there.

Question 23

Why might type O blood people get over diagnosed with vWD?

Answer 23

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.

Question 24

Glanzmann thrombasthenia is a disease caused by a defective _______.

Answer 24

GPIIb/IIIa

Question 25

Immune thrombocytopenic purpura (ITP) is often preceded by _______ and is often associated with _______

Answer 25

a viral infection

concurrent autoimmune disorders

Question 26

Make a diagnosis: Patient has negative bone marrow biopsy for malignancies, megakaryocytes are present at high numbers, no infections or meds, decreased platelet count.

Answer 26

ITP!

the antibodies are attacking the platelets.

Question 27

Treatment options for ITP.

Answer 27

• steroids
• rituximab
• splenectomy
• IVIG
• IPO (thrombopoietin receptor agonist)

Question 28

Causes of increased destruction of platelets?

Answer 28

ITP, DIC, TTP (thrombocytopenic purpura), autoimmune stuff (like lupus), sepsis