Blood coagulation Flashcards
Steps of normal hemostasis
Vasospasm (reduce blood flow and enhance platelet aggregation+coagulation). Formation of platelet plug. Thombin catalyzes fibrinogen to fibrin. Fibrin clot formation. Fibrinolysis by plasmin.
When are the different coagulation pathways activated?
Intrinsic pathway: surface contact with a foreign body or extravascular tissue.
Extrinsic pathway: Thromboplastin
Coagulation factors that are dependent on vitamin K
II - prothrombin.
VII - proconvertin (no longer considered a coagulation factor).
IX - plasma thromboplastin component.
X - Stuart factor.
Major rate limiting step in coagulation cascade
Activation of factor X
Thrombin - effects
Catalyzes fibrinogen to fibrin, and is a powerful stimulus for platelet aggregation.
Stimulus for platelet aggregation and coagulation
Atherosclerosis, venous pooling, thrombophlebitis
White vs red thrombi - location and mechanism
White thrombi: arterial circulation - often caused bu platelet aggregation.
Red thrombi: venous ciculation - often caused bu coagulation.
Main types of anticoagulants
Vitamin K antagonists.
Drugs that potentiate antithrombin III.
Drug that directly inhibit thrombin or active factor X.
Which coagulation factors are inhibited by warfarin, and in which pathway are these factors found?
IX - intrinsic VII - extrinsic X - both pathways Prothrombin - both pathways (all are inactive factors)
Which coagulation factors are inhibited by heparin?
All active coagulation factors
Intrinsic coagulation pathway - cascade
1) Surface contact
2) XII (Hageman factor) activation
3) XI activation
4) IX activation
5) X (Stuart factor) activation
6) II (prothrombin) activation.
7) activation of fibrin, and formation of stabilized fibrin by factor XIII
Extrinsic coagulation pathway - cascade
1) Tissue factor.
2) VII (proconvertin) activation
3) Activation of X (Stuart factor)
4) II (prothrombin) activation.
5) activation of fibrin, and formation of stabilized fibrin by factor XIII
Drugs that may increase prothrombin time (15 drugs)
mnemonic, letter for each drug) ADD CAMP CHARTS FA(st
Amiodarone Cimetidine Disulfiram Fluconazole Metronidazole Phenylbutazone Sulfinpyrazone Trimethoprim-sulfamethoxazole Aspirin (high doses) Cephalosporins, third-generation Heparin, argatroban, dabigatran, rivaroxaban, apixaban
Body factors that may increase prothrombin time
Hyperthyroidism, hepatic disease
Drugs that may decrease prothrombin time
Barbiturates Cholestyramine Rifampin Diuretics Vit K
