Coagulation Flashcards
Which pathway does endothelial injury initiate?
Extrinsic pathway
What problems can arise with vessels that lead to bleeding?
Hereditary haemorrhagic telangectasia (dilated micro vascular swellings –> GI bleed)
Steroids
Neisseria meningitidis
Vit c deficiency
How does liver disease affect coagulation?
Reduced protein synthesis
Reduced clotting factors and fibrinolytic components
Reduced thrompoietin production–> thrombocytopenia
Reduced clotting and clot degradation: prolonged bleeding time and DIC
Vitamin k deficiency affects clotting factors
Portal hypertension–> splenomegaly–> platelet sequestering
What is disseminated intravascular coagulation?
Systemic intravascular coagulation
Exhaustion of clotting factors and platelets– increased bleeding time
Excess fibrin formation – microvascular thrombi cause organ ischaemia
What would the coagulation profile of a patient with DIC look like?
Increased coagulation time
Thrombocytopenia
Increased fibrin degradation products
(Schistocytes on blood film (=fragmented RBCs))
What might cause a problem with clotting factors?
Congenital: haemophilia A (VIII) and B (IX)
Acquired: liver disease, vitamin k deficiency (II, VII, IX, X)
Describe the presentation of clotting factor associated bleeding.
Haemarthroses–> joint pain and deformity
Muscle haematomas
Increased bleeding post dental extraction
Post operative and trauma bleeding
Intra cerebral haemorrhage
What can cause a platelet disorder?
Drugs- aspirin (no TxA2), Clopidogrel (ADPr block)
Uraemia inhibits function
Hypergammaglobulinaemia
Myeloproliferative diseases
Describe the presentation of platelet associated bleeding.
Affects skin and mucous membranes: epistaxis, gum bleeding, bruising
Prolonged bleeding after trauma: menorrhagia, dental extraction, post op
*haemarthroses and muscle haematomas rare
What is the the role of von Willebrand’s factor?
Released from endothelium in response to damage
Binds collagen on exposed tissue
Platelets bind to factor via receptors
= carrier and protector for factor VIII
What is the mechanism in von Willebrand’s disease?
Reduced production and activity of von Willebrand’s factor
Leads to reduced platelet adhesion and reduced amount and activity of VIII.
How can the intrinsic coagulation cascade pathway be assessed?
APTT- activated partial thromboplastin time
How can the extrinsic pathway be assessed?
PT- prothrombin time
What does thrombin time assess?
Activity of thrombin to convert fibrinogen to fibrin
What may increase APTT?
Clotting factor deficiencies- XII, XI, IX (haemophilia B), VIII (haemophilia A)
Heparin therapy- affects X and II
