The vascular endothelium protects platelets from subendothelial aggregating substances i.e. collagen
Vasoconstriction around injured site helps coagulation how?
Reduced blood flow decreases pressure and loss of blood
Reduced blood flow brings coagulation factors into tissue contact more readily
Reduced blood flow decreases wall diameter, decreasing size of breach
Why is Fibrinolysis necessary?
It prevents inappropriate extension of the fibrin plug
Prevents clotting from damaging nearby cell
Prevents clotting in case of infected blood
To prevent inappropriate prevention of coagulation, where are coagulation inhibitors limited to?
Intact endothelium
Breached endothelium
Free flowing blood
Inhibitors are triggered by late products of coagulation
What is inhibited by the Tissue Factor Pathway Inhibitor?
FX reversibly
FX permanently
FVII
FV
Anthithrombin deactivates several enzymes of the coagulation system
Protein S & C work the same way
The Protein C pathway is initiated by what?
Thrombin
Antithrombomodulin
Antithrombin
Thrombomodulin works in the free flowing blood
Both thrombin and thrombomodulin work on the endothelial cell surface
What is the role of thrombomodulin?
Conversion of Thrombin to Antithrombin
Conversion of Thrombin to a Coagulation Inhibitor
Removal of platelets
Excess thrombin binds to thrombomodulin on intact cells, which allows it to be altered
Protein C acts as an anticoagulant by degrading Factors
V
VIII
Protein C needs Mg in order to function
Which of the following support Protein C activity?
Protein S
Inactive F V
Active F V
60% of patients with thrombophilia have a
Factor II deficiency
Protein C deficiency
Protein S deficiency
VTE = Venous Thromboembolism
What is thrombosis?
An increased liklihood of spontaneous clotting
An inability to form blood clots
Name the risk factors for thrombophilia
Alteration in blood components i.e. pregnancy
Circulatory stasis i.e. venous problems
Artificial surfaces i.e. a STENT
VTE occurs when blood coagulation overwhelms fibrogenlysis/anticoagulant mechanisms
Thrombophilia is linked to Lupus Anticoagulant Syndrome
Name some examples where Anticoagulation therapy is necessarry
Patient with a myocardial infarction (MI)
Patients with Lupus/APS
Deep Vein Thrombosis/ Primary Embolism
How is Heparin administered?
Intravenously
Subcutaneously
Ingestion
How does Heparin work?
Increases action of Antithrombin
Increases Protein C activity
Increases degredation of platelets
Why is Low Molecular Weight Heparin better?
100% bioavalibility
Longer half life
Less frequent osteoporosis
Dabigatran is only used in cases of Atrial Fibrilation
Dabigatran is a FX inhibitor, Rivaroxabin is a thrombin inhibitor
Warfarin works how?
Directly inhibits thrombin
Inhibits Vit K metabolism
Lyses platelets
Without Vitamin K, why is coagulation so much slower?
Non carboxylated factors cannot bind to Ca2+
Non carboxylated factors cannot bind to phosphorylated
Non carboxylated factors cannot be inhibited
Warfarin is used when all four clotting factors are low
What is the leading dose of Warfarin?
6mg for 3 days
3mg for 6 days
What test is used to monitor warfarin activity?
Prethrombin time
Activated Partial Thromboplastin Time
Fibrin Assay
What is the reference for Prethrombin Time?
Standard reference thromboplastin
Potency is ISI- International Sensitivity Index
Standard reference antithrombin
INR = Prethrombin Time/ Mean Normal Prethrombin Time
Match the dangerous INR ranges- A= (2-3) B= (3-4)
A= Prosthetic Heart Valves B = DVT
A = DVT B = Prosthetic Heart Valves
When using Warfarin, stop if the INR <2 for two consecutive days
