Coagulation Flashcards
Hemostasis
Stopping the flow of blood
What does hemostasis prevent
The minor bumps and bruises of daily life from being fatal
What are the three phases of the separate mechanisms?
Mechanical phase
Chemical phase
Final Phase
What two responses make up the mechanical phase?
Vascular response
Platelet response
Vascular response
The arteries and arterioles contract and reduce the size of the lumen when the vessels are damaged
What does the constriction of the vessels do?
Decreases blood flow so less blood is lost
Turbulence activates platelets
Platelet response
When the platelets hit connective tissue or injury they activate and become sticky, grabbing onto each other, creating a plug
von Willebrand’s factor
Required for platelets to stick to the site of injury
Chemical phase
Coagulation mechanism response aka clotting cascade
Involves a number of clotting factors
What two pathways does the chemical phase involve?
Intrinsic and extrinsic pathways
What does the chemical phase result in?
Fibrinogen being converted into fibrin
Final Phase
Degradation of the fibrin clot
Coagulation Mechanism Response or Clotting Cascade
Fibrinogen and other substances in the blood are inactive and when activated they change from a liquid to a semi-solid substance
When activated, what are fibrinogen and other substances called?
Clotting factors
Numbered I-XIII
VI is missing
Activation of clotting factors: Intrinsic Pathways
Activated without tissue contact
Example: IV Catheter placement without proper anti-coagulant
Activation of clotting factors: Extrinsic Pathways
More commonly activated
Activated with tissue contact outside of the blood vessel (injury)
What is important to remember in sample collection for coagulation?
Minimize tissue damage
Minimal venous stasis
Why must you never use an indwelling catheter to obtain a sample for coagulation testing?
Because it may have fibrinogen, fibrin, and platelets around the catheter
What is the preferred method to collect blood for coagulation testing?
Vacutainer or monovette
The proper ratio of anticoagulant to blood
Coagulation tests: aPTT
Activated partial thromboplastin time
What does aPTT measure?
The contact activation (intrinsic) pathway is initiated by the activation of the “contact factors” of plasma
Coagulation tests: PT
Prothrombin time test
What does the PT test measure?
The tissue factor (extrinsic) pathway is initiated by the release of tissue factor
In-House Analyzers
Use fresh or citrated anticoagulated blood
IDEXX Coag DM; Q-labs Insight
Thromboelastograph
Measures initial clot to fibrinolysis
Clot formation time
Strength of clot
Breakdown time
Platelet Function Analyzers
Assessment of platelet adhesion and aggregation
Blood is drawn through an aperture and platelets adhere to the membrane
Measures the time it takes to occlude aperture with platelets is recorded
