Principles of Hemostasis Flashcards Preview

AP: Cumulative > Principles of Hemostasis > Flashcards

Flashcards in Principles of Hemostasis Deck (44):
1

define hemostasis

a complex physiological process that balances forces of coagulation and anticoagulation to protect the vasculature from uncontrolled bleeding or excessive clotting

2

what are the three phases of hemostasis?

primary= formation of platelet plug
secondary= coagulation
tertiary= fibrinolysis (vascular repair)

3

what are the three steps of forming a platelet plug?

platelet adhesion
platelet activation
platelet aggregation

4

what is von Willebrand factor?

large, heterogeneous multimeric glycoprotein.

5

what does von Willebrand factor do?

-protects coagulation factor VIII from rapid inactivation
-binds platelets via the glycoprotein receptor complex (causes platelets to adhere to injured part of wall)

6

what makes vWF bind to platelets?

change in shear rate (blood flow)

7

what happens to the conformation of vWF when the sheer rate changes?

it unravels

8

how do vWF and collagen bind platelets?

vWF via glycoprotein Ib receptor
collagen via the glycoprotein VI receptor and a2b1 integrin

9

what is the most common congenital bleeding disorder?

von Willebrand disease

10

what is von Willebrand disease?

deficiency in vWF
manifests as impaired platelet function
-bruise easily
-bleeding gums
-epistaxis

11

how can von Willebrand disease be treated?

transfusion of FFP, cryo, DDAVP or vWF/FVIII concentrate

12

how are platelets activated?

by agonists at the site of injury -collagen*, thrombin*, ADP and epinephrine

13

what happens when platelets are activated?

1.change morphology
2.Release the contents of their alpha granules and dense granules – ADP, serotinin, factor V, factor VIII, vWF, fibrinogen
3.Release substances synthesized in the cytosol (thromboxane A2) into the environment
4.**Express new negatively-charged receptors on their surface membrane

14

why does aspirin inhibit platelet aggregation?

it's a "cox blocker"
blocks cyclooxygenase (COX)

15

what are the three main platelet surface receptors?

thrombin
ADP
Fibrinogen

16

what are the primary platelet aggregation adhesive molecules?

fibrinogen and vWF

17

platelet aggregation is mediated by....

the surface receptor-glycoprotein IIb/IIIa receptor

18

what is the fibrin stabilizing factor?

Factor VIII

19

what are the direct effects of aspirin on fibrinogen and FXIII?

aspirin acetylates fibrinogen-clot structure is looser and easier to lyse

20

the proper interaction of coagulation factors requires the presence of what?

a negatively charged phospholipid membrane

21

where are most coagulation factors synthesized?

the liver

22

which factor is the only one with extra-hepatic origin?

Factor VIII

23

what is the principle function of vitamin K?

catalyzes the carboxylation of glutamic acid

24

what does coumadin do?

inhibits carboxylation of the vitamin K dependent factors by vitamin K

25

which has the shortest half life of the vitamin K dependent factors?

FVII

26

hemophilia A is a deficiency of _____
hemophilia B is a deficiency of _____

A = FVIII
B = FIX

27

what is also known as "Christmas disease?"

Hemophilia B

28

of the two models of coagulation, which is considered to be the older model?

coagulation cascade

29

what is the main objective of the coagulation cascade?

essence is to create thrombin

30

what are the three pathways of the coagulation cascade?

common, intrinsic, extrinsic

31

name some of the hemostatic actions of thrombin

cleavage of fibrinogen to fibrin
activates platelets
activates F V, VII, VIII, IX, XIII

32

what are the three overlapping stages in the cell-based model of coagulation?

initiation, amplification and propagation

33

in the cell-based model of coagulation, what is initiation?

a procoagulant stimulus generates enough thrombin to initiate coagulation process

34

in the cell-based model of coagulation, what is amplification?

platelets and coagulation factors are activated

35

in the cell-based model of coagulation, what is propagation?

large amounts of thrombin are generated on the activated platelet surface

36

prothrombin is converted to thrombin in which step of the cell-based model of coagulation?

initiation

37

name three regulators of coagulation

Tissue Factor Pathway Inhibitor (TFPI)
Antithrombin (AT): biggest inhibitor of thrombin in adults
Protein C (PC)

38

what is the primary anticoagulant action of heparin?

its ability to inhibit thrombin activity

39

what are some of the effects heparin on AT?

binds to AT and causes a conformational change in the molecular structure of AT (need ~ 80% to be effective)
transforms AT from a slow to a rapid inhibitor of thrombin

40

neonates have low levels of what?

procoagulant and anticoagulant factors

41

neonatal platelet counts are what percent of adults?

100%...they're the same

42

what is the relationship between vWF and age?

decreases with age

43

the FDA has approved the use of recombinant activated factor VII for what uses?

patients with hemophilia A and B with developed inhibitors against FVIII and FIX
patients with FVII deficiency

44

rFVIIa has a huge affinity for what?

Tissue factor