Clotting Cascade

Question 1

Action of Warfarin

Answer 1

Decreases the amount of active vit K, which is required by y-glutamylcarboxylase, due to its ability to inhibit epoxide hydrolase.

Question 2

y-glutamylcarboxylase is required in the synthesis of Ca2+ binding proteins, which are (6)

Answer 2

Factors II, VII, IX, X
Protein C
Protein S

Question 3

Extrinsic clotting pathway (2)

Answer 3

Activated by external trauma.

Quicker than the intrinsic pathway.

Question 4

Intrinsic clotting pathway (3)

Answer 4

Activated by trauma inside the vasculature.
Activated by platelets, exposed epithelium, collagen.
Slower that extrinsic pw.

Question 5

Draw the Intrinsic PW

Answer 5

See notes.

Question 6

Draw the Extrinsic PW

Answer 6

See notes.

Question 7

Primary hemostasis

Answer 7

Platelets in blood aggregate at tissue site and form a plug.

Question 8

Secondary hemostasis

Answer 8

Platelet plug is reinforced by fibrin mesh through a coagulation cascade.

Question 9

Major roles of Thrombin (5)

Answer 9

Convert prothrombin to thrombin.
Convert V and VIII to Va and VIIIa.
Convert fibrinogen to fibrin.
Activate platelets.
Convert XIII to XIIIa cross linked fibrin.

Question 10

2 types of oral anticoagulants

Answer 10

Hydroxycoumarins

Indanediones

Question 11

Long term control of INR requires:

Answer 11

Vitamin K

Question 12

Daily oral vitamin K requirements:

Answer 12

50-100 mg

Question 13

Vitamin K activation cycle

Answer 13

Draw

Question 14

What enzyme is the target for warfarin?

Answer 14

Vitamin K epoxide reductase (VKOR)

Now cannot activate factor II, VII, IX, X and Protein C or S.

Question 15

Warfarin exists in a _________ and the _____ is more predominant

Answer 15

Racemic mixture

S form

Question 16

Warfarin has a high degree of ___________

Answer 16

Drug interactions. Must take them into consideration.

Question 17

Main roles of protein S and C (2)

Answer 17

Maintain vascular permeability.

Inactivates factor Va and factor VIIIa.

Question 18

A genetic deficiency in protein C increases the risk of:

Answer 18

Venous thrombosis.

Question 19

Recommendations for patients taking coumadin

Answer 19

Check meds
Check INR
Watch for signs of bleeding
Stomach pain, ulcers, fever, nausea are common side effects.
Carry an ID card.
Watch diet.

Question 20

Hemophilia A is a deficiency in what?

Answer 20

Factor VIII

Question 21

PT measures

PTT measures

Answer 21

Extrinsic pathway

Intrinsic pathway

Question 22

Factor with the shortest half-life

Answer 22

Factor VII

Question 23

End-stage liver disease’s affect on PT and PTT

Answer 23

Tends to increase PT before PTT due to deficient production of factor VII.

Question 24

ISI

Reference values

Answer 24

International sensitivity index.
Indicates how a particular batch of tissue factor compares to an international reference tissue factor.
Usually between 0.94 and 1.4 for more sensitive and 2.0-3.0 for less sensitive preps.

Question 25

INR

Answer 25

Ratio of a patient’s prothrombin time to a normal sample raised to the power of the ISI value.