Secondary Hemostasis and Related Disorders

Question 1

What is the purpose of secondary hemostasis?

Answer 1

Stabilizes the weak platelet plug via the coagulation cascade

Question 2

What is generated during the coagulation cascade?

Answer 2

Thrombin

Question 3

What does thrombin convert during the coagulation cascade?

Answer 3

Fibrinogen→ fibrin in the platelet plug

Question 4

What is the outcome of secondary hemostasis?

Answer 4

Platelet-fibrin thrombus stabilizing the platelet plug

Question 5

Factors of the coagulation pathway are produced by the liver in an inactive form. What are the 3 requirements for activation of these factors?

Answer 5

1) Exposure to an activating substance
2) Phospholipid surface of platelets
3) Calcium (derived from platelet dense granules)

Question 6

What are the common clinical features seen with disorders of secondary hemostasis?

Answer 6

Deep tissue bleeding into muscles and joints (hemarthrosis) and rebleeding after surgical procedures

Question 7

What does prothrombin time (PT) measure?

Answer 7

Measures extrinsic (Factor VII) and common (factors II, V, X and fibrinogen) pathways of the coagulation cascade

Question 8

What does partial throboplastin time (PTT) measure?

Answer 8

Intrinsic (factors XII, XI, IX, VIII) and common (factors II, V, X, and fibrinogen) pathways of the coagulation cascade

Question 9

Factor VIII deficiency that can either be X-linked recessive or arise from a new mutation without family history…

Answer 9

Hemophilia A

Question 10

What is the common presentation for Hemophilia A?

Answer 10

Deep tissue, joint, and postsurgical bleeding

Question 11

What are the findings on laboratory studies of a patient with Hemophilia A with respect to PT, PTT, FVIII, platelet count, and bleeding time?

Answer 11

PT: normal
PTT: elevated
FVIII: decreased
Platelet count: normal
Bleeding time: normal

Question 12

What is the treatment for Hemophilia A?

Answer 12

Give recombinant FVIII

Question 13

Factor IX deficiency that resembles Hemophilia A, except Factor IX is deficient…

Answer 13

Hemophilia B

Question 14

Disease involving an acquired antibody against a coagulation factor that results in impaired factor function…

Answer 14

Coagulation factor inhibitor

Question 15

What is the most common antibody involved in coagulation factor inhibitors?

Answer 15

Anti-FVIII

Question 16

How is a coagulation factor inhibitor anti-FVIII differentiated from Hemophilia A?

Answer 16

A mixing study

Mix normal plasma with patient’s plasma—If PTT is corrected then Hemophilia A and if PTT remains elevated then its most likely a coagulation factor inhibitor against FVIII

Question 17

The most common inherited coagulation disorder…

Answer 17

Von Willebrand disease

Question 18

How does Von Willebrand disease present?

Answer 18

With mild mucosal and skin bleeding

Question 19

What causes the mild mucosal and skin bleeding seen with Von Willebrand disease?

Answer 19

Low vWF impairing platelet adhesion

Question 20

What is found on the labs of a patient with Von Willebrand disease with respect to bleeding time, PTT, and PT?

Answer 20

Bleeding time: increased
PTT: increased—vWF is needed to stabilize FVIII
PT: normal

Question 21

What abnormal test is found when performed on patients with Von Willebrand disease?

Answer 21

Ristocetin test

Ristocetin induces platelet agglutination by causing vWF to bind platelet GPIb—No vWF=impaired agglutination→ abnormal test

Question 22

What is the treatment for Von Willebrand disease?

Answer 22

Desmopression and ADH analog

Question 23

Desmopression is used for the treatment of Von Willebrand disease. What is the mechanism of action of desmopression?

Answer 23

Increases vWF released from Weibel-Palade bodies of endothelial cells

Question 24

What is disrupted when an individual has a vitamin K deficiency?

Answer 24

Disruption of multiple coagulation factors

Question 25

Where and how is Vitamin K activated?

Answer 25

Activated in the liver by epoxide reductase

Question 26

What is the function of activated vitamin K?

Answer 26

Gamma carboxylates factors II, VII, IX, X, proteins C and S This is necessary for factor function

Question 27

What are the 3 most common causes of Vitamin K deficiency?

Answer 27

- Newborn - Long-term antibiotic therapy - Malabsorption

Question 28

Why is vitamin K deficiency common in newborns?

Answer 28

Lack of GI colonization by bacteria that normally synthesize vitamin K

Question 29

What is given to newborns to prevent hemorrhagic disease?

Answer 29

Vitamin K injection

Question 30

How does long-term antibiotic therapy cause a vitamin K deficiency?

Answer 30

The antibiotic disrupts the vitamin K-producing bacteria in the GI tract

Question 31

How does malabsorption cause a vitamin K deficiency?

Answer 31

Malabsorption causes a deficiency of fat-soluble vitamins—AEDK

Question 32

How does liver disease cause abnormal secondary hemostasis?

Answer 32

Decreased production of coagulation factors Decreased activation of vitamin K by epoxide reductase

Question 33

Which laboratory test is used to follow the effect of liver failure on secondary hemostasis?

Answer 33

PT

Question 34

How does a large-volume transfusion cause abnormal secondary hemostasis?

Answer 34

Dilutes the coagulation factors