lecture 2 Flashcards
(24 cards)
What are the main components of haemostasis?
Blood vessel wall, platelets,
von Willebrand factor (vWF),
coagulation factors, fibrinogen
, and fibrinolysis.
How does the blood vessel wall regulate haemostasis?
Endothelial cells produce negative regulators (e.g., prostacyclin, nitric oxide) and the sub-endothelium contains activators (e.g., collagen, tissue factor, vWF).
What are the roles of von Willebrand factor in haemostasis?
Mediates platelet adhesion to collagen and stabilizes coagulation factor VIII.
What are the primary functions of platelets in haemostasis?
Adhere to sub-endothelial proteins, activate and aggregate with other platelets, and support coagulation factor activation
What is the coagulation cascade’s main goal?
To convert soluble fibrinogen into insoluble fibrin, forming a stable clot.
Which cofactors and enzymes are required for the coagulation cascade?
Calcium, phospholipids, vitamin K, and serine proteases (e.g., FII, FVII, FIX, FX).
What is fibrinogen’s role in haemostasis?
It binds platelets for aggregation and is polymerized by thrombin to form a fibrin clot.
What is the role of thrombin in haemostasis?
Polymerizes fibrinogen into fibrin and fully activates platelets.
How is clot formation regulated?
By thrombin inhibitors (e.g., antithrombin, protein C system) and the ADAMTS-13 enzyme regulating vWF adhesivity.
What is fibrinolysis?
The process of clot breakdown by plasmin, producing fibrin degradation products like D-dimer.
What are the core laboratory tests to assess haemostasis?
Platelet count, prothrombin time (PT), activated partial thromboplastin time (APTT), fibrinogen level, and D-dimer level.
What does a prolonged PT indicate?
Issues with the extrinsic pathway, often due to factor VII deficiency
What does a prolonged APTT indicate?
Issues with the intrinsic pathway, involving factors VIII, IX, or XI.
What might cause a prolonged PT and APTT?
Common pathway deficiencies (e.g., factors II, V, X), vitamin K deficiency, or liver dysfunction.
What are normal plasma fibrinogen levels?
1.5–4.0 g/L.
What can elevated D-dimer levels indicate?
Disseminated intravascular coagulation (DIC), venous thrombosis, pregnancy, sepsis, or malignancy.
How are fibrinogen levels measured?
Using a clotting assay similar to PT/APTT tests.
Why might fibrinogen levels be low?
Conditions such as liver disease, DIC, or massive transfusion.
What are point-of-care tests, and when are they useful?
Rapid tests performed near the patient, useful in urgent settings like trauma or major surgery.
Name a key point-of-care test for assessing haemostasis.
Thromboelastography (TEG) or thromboelastometry (ROTEM).
What does thromboelastography assess?
The dynamic process of clot formation, strength, and fibrinolysis.
How does thromboelastography help in clinical decision-making?
It identifies haemostatic defects, such as hyperfibrinolysis, to guide treatments like antifibrinolytic drugs.
What does the CoaguChek test measure?
The effect of warfarin on clotting time.
What does a D-dimer point-of-care test help diagnose?
The likelihood of venous thrombosis.
