Coagulation

Question 1

What are the 4 steps of hemostasis?

Answer 1

• vascular spasm
• primary hemostasis (platelet plug)
• secondary hemostasis (coagulations and formation of fibrin)
• fibrinolysis

Question 2

What causes vasospasm and why?

Answer 2

• vascular injury → TxA2 released (vasoactive) → vasospasm

Question 3

What is the process of platelet plug formation?

Answer 3

• platelets ADHERE to exposed vWF in the endothelium which also releases tissue factor (factor III) → ACTIVATES platelets which then release substances (ADP & TxA2) → activates other platelets (and propogates secondary hemostasis) → AGGREGATION → platelet plug formation

Question 4

Which factor is essential in all pathways?

Answer 4

• calcium (factor IV)

Question 5

When is the extrinsic pathway activated? What is the initiating step? Goal? Factors involved? Lab to assess?

Answer 5

• Activated when cascade is initiated outside intravascular space, fast (15 sec)
• Initiating step: injured endothelium releases factor III
• goal being thrombin production
• Factors: III, VII
• PT/INR

Question 6

When is the intrinsic pathway activated? What is the goal? Factors involved? Lab to assess?

Answer 6

• activated when cascade is activated inside intravascular space, slow (6 min)
• amplifies thrombin generating effect of the extrinsic pathway
• Factors: VIII, IX, XI, XII
  
  • “you can’t buy It for $12, but you can but It for $11.98”
• aPTT/ACT

Question 7

What happens in the final common pathway? What factors are involved?

Answer 7

• Prothrombin (II) converted to thrombin → fibrinogen to fibrin → cross linked fibrin
• Factors: I, II, V, X, XIII
  
  • “On the 13th of the month, at the 5 and dime (10) shops, you can buy It for 1 or 2 bucks.”

Question 8

What is the process of fibrinolysis?

Answer 8

• plasminogen via TPA or urokinase converted to plasmin → breaks down fibrin to fibrin degradation products → measured by D - dimer.

Question 9

Mnemonic for factors (table)

Answer 9

Question 10

How does heparin work?

Answer 10

• increases action of antithrombin III → inhibiting intrinsic pathway → measured by aPTT/ACT
• also works on common pathway through inhibition of activated factor X

Question 11

How does coumadin work?

Answer 11

• inhibits vitamin K factors (II, VII, IX, X) → factor VII (shortest half life) is extrinsic pathway → extrinsic pathway blocked → meausured by PT/INR
  
  • inhibits intrinsic (factor IX) and common pathways (factor II and X)

Question 12

FFP contains which blood products?

Answer 12

• all coagulation factors
• no platelets

Question 13

What is cryoprecipitate and which blood products does It contain?

Answer 13

• fraction of plasma that precipitates once FFP is thawed
• contains high concentrations of factor VIII, XIII, vWF, and fibrinogen (I)

Question 14

What is desmopressin and what does It do?

Answer 14

• synthetic ADH
• stimulates release of endogenous vWF and increases [endogenous] factor VIII activity