Clotting

Question 1

What is the difference between primary and secondary hemostatis

Answer 1

Primary hemostasis involves the initial, rapid response to vascular injury, forming a temporary platelet plug, while secondary hemostasis reinforces this plug with a fibrin mesh through the activation of the coagulation cascade

Question 2

What is Prothrombin Time (PT)?

Answer 2

A primary tool for evaluating secondary hemostasis, specifically the extrinsic and common coagulation pathways.

PT is crucial for assessing the blood’s ability to clot, particularly in cases of bleeding disorders.

Question 3

Which coagulation pathways does PT evaluate?

Answer 3

Extrinsic and common coagulation pathways.

These pathways are vital for normal blood clotting processes.

Question 4

Why is the extrinsic pathway sensitive to vitamin K factors?

Answer 4

Due to factor VII’s short half-life.

Vitamin K is essential for the synthesis of several coagulation factors.

Question 5

What factors are associated with the extrinsic pathway?

Answer 5

Factors III (tissue factor), VII, X.

Calcium play a role

Question 6

What can cause an elevation in PT?

Answer 6

• fVII deficiency
• Early or low-dose itamin K antagonist
• Mild Vitamin K deficiency
• Early to mild hepatic insufficiency

These conditions can impair the coagulation process, leading to prolonged PT.

Question 7

What does aPTT stand for?

Answer 7

Activated partial thromboplastin time

Question 8

What aspect of hemostasis does aPTT evaluate?

Answer 8

Secondary hemostasis

Question 9

Which pathways is aPTT associated with?

Answer 9

Intrinsic or common pathway

Question 10

Name causes leading to elevated aPTT.

Answer 10

• Factor VIII, IX, or XI deficiency
• Unfractionated heparin
• DIC
• Severe vWF dz
• Hepatic failure
• Circulating anticoagulant

Question 11

True or False: aPTT is only associated with the extrinsic pathway.

Answer 11

False

Question 12

Fill in the blank: Elevated aPTT can be caused by ____ factor deficiencies.

Answer 12

fVIII, IX, or XI deficiency

Question 13

What is one condition that can cause elevated aPTT related to blood coagulation factors?

Answer 13

Severe von Willebrand disease (vWF dz)

Question 14

Which anticoagulant is associated with elevated aPTT?

Answer 14

Unfractionated heparin

Question 16

What percentage drop in amount of a factor needed to see prolongation in PT and PTT?

Answer 16

25-30%

Question 17

How should marked prolongation in PT and PTT be interpreted?

Answer 17

Usually significant

Question 18

How should mild prolongation in PT and PTT be interpreted?

Answer 18

With caution

Question 19

Is there value in assessing hypercoagulability with PT and PTT?

Answer 19

No value

Question 20

What PT or aPTT level poses a risk for bleeding in surgery?

Answer 20

> 1.5x control

Question 21

What are potential causes for prolonged PT or aPTT?

Answer 21

• fX deficiency
• V deficiency
• II deficiency
• Fibrinogen deficiency
• Vitamin K deficiency
• Hepatic failure
• DIC
• Massive bleeding
• Dilutional coagulopathy
• Unfractionated heparin

Question 22

What pathway does Activated Clotting Time primarily measure?

Answer 22

Intrinsic and common pathway

Question 23

Which factor is activated by Activated Clotting Time?

Answer 23

Factor XII

Question 24

Is Activated Clotting Time more or less sensitive than aPTT?

Answer 24

Less sensitive than aPTT

Question 25

What is the normal Activated Clotting Time for dogs?

Answer 25

Usually less than 110 sec

Question 26

What is the normal Activated Clotting Time for cats?

Answer 26

Usually less than 75 sec

Question 27

What substances can be used to activate factor XII in the context of Activated Clotting Time?

Answer 27

Whole blood + colite, kaolin, glass beads

Question 28

What is another substance that induces Activated Clotting Time?

Answer 28

Diatomaceous earth

Question 29

What is the primary use of D-dimers in medical testing?

Answer 29

Sensitive test for thromboembolism and DIC ## Footnote Unknown if indicator of hypercoagulability or predictor of thrombosis

Question 30

Which test is considered the best for diagnosing hypercoagulability?

Answer 30

TEG ## Footnote TEG stands for Thromboelastography

Question 31

In TEG, what does a hypercoagulable tracing indicate?

Answer 31

↑ G value; R and K values generally ↓ and/or MA and α values ↑ ## Footnote Indicates increased clot strength and reduced clotting time

Question 32

What does an increase in MA in TEG testing suggest?

Answer 32

PLT hyperaggregability ## Footnote Indicates increased platelet aggregation contributing to clot formation

Question 33

What does a decrease in R value in TEG testing indicate?

Answer 33

Enzymatic hyperactivity ## Footnote Suggests faster clot formation due to enhanced enzymatic activity

Question 34

Fill in the blank: D-dimers are a sensitive test for _______.

Answer 34

thromboembolism and DIC

Question 35

True or False: TEG is not useful for diagnosing hypercoagulability.

Answer 35

False ## Footnote TEG is specifically used for this purpose

Question 36

What is the role of platelets in primary hemostasis?

Answer 36

Provide a source of preformed chemokines stored in intracellular storage granules

Question 37

What do activated platelets synthesize that helps in recruiting and activating additional platelets?

Answer 37

Secondary agonists: prostanoids (TxA2) and ADP

Question 38

Which pathway is TxA2 produced by via the platelets?

Answer 38

COX-1 pathway ## Footnote Thromboxane A2 (TxA2), a prostanoid produced by platelets through the COX-1 pathway, is a potent vasoconstrictor and platelet activator, playing a crucial role in thrombosis and cardiovascular health

Question 39

What happens once the platelet integrin alphaIIbBeta3 is activated by an agonist?

Answer 39

Binding domains for fibrinogen are exposed, leading to interplatelet cohesion and aggregation ## Footnote Platelet integrin αIIbβ3 (also known as GPIIb/IIIa) is activated by agonists through a process called "inside-out signaling," where agonists induce conformational changes that increase the integrin's affinity for its ligands.

Question 40

True or False: Platelets play more of a role in secondary hemostasis than primary hemostasis.

Answer 40

False | Platelets play a larger role in primary hemostasis