Disorder of Clot Flashcards
What is a measure of the extrinsic pathway?
Prothrombin Time (PT)
What is a measure of the intrinsic pathway?
activated partial thromboplastin time (APTT)
What is a measure of the common pathway?
Fibrinogen
What are the 2 most common causes of prolonged PT?
Warfarin, Factor VII deficiency
What are causes of prolonged APTT?
Heparin, Factor VIII, iX, XI or XIII deficiency, Von Willebrand’s Disease
What causes prolonged PT and APTT?
Vit K deficiency + low fibrinogen
Disseminated Intravascular Coagulation
Heparin toxicity
Which factors are vit K dependent?
II, VII, IX, X, protein C and S
What does PT measure?
VII, X, V, prothrombin and fibrinogen (classic ‘extrinsic’ pathway)
What does APTT measure?
measures XII, XI, IX, VIII, X, V, prothrombin and fibrinogen (‘intrinsic’ pathway)
What prolongs thrombin time?
fibrinogen deficiency
What is haemophilia A?
a disorder where the blood cannot clot properly due to a deficiency of a clotting factor called Factor VIII.
How does heparin work?
increases effect of Anti-thrombin III by 2000 fold inhibiting clot formatio
How does warfarin work?
reduces Vit K dependent factors
What investigations would you carry out in a bleeding patient?
FBC with platelet count
PT - Pro-thrombin time
APTT -Activated partial thromboplastin time Fibrinogen
How do you confirm a coagulation factor deficiency?
If abnormal PT or APTT, mix 50:50 patient’s and normal plasma. A deficiency is present if the the PT/APTT corrects.
What type of disorder is Haemophilia A
Factor VIII deficiency. X-Linked recessive pattern.
What are the clinical features of Haemophilia A?
Spontaneous bleeding into skin, muscle and joints. Retroperitoneal and intracranial bleeding. Muscle haematoma.
How is Haemophilia A diagnosed?
Increased APTT, 50:50 Plasma correction, decreased Factor VIII on assay
How is Haemophilia A managed?
Desmopressin - minor bleeds
recombinant Factor VIII - major/life-threatening bleeds
How does desmopressin work?
causes release of von Willebrand factor (vWF) and releases stored factor VIII
What is haemophilia B?
• Aberrations of the factor IX gene, which is also present on the X chromosome, result in a reduction of the plasma factor IX level, giving rise to haemophilia B.
How is haemophilia B treated?
Factor IX concentrate
How does tranexamic acid work?
slows down plasmin/plasminogen system and prevents fibrinolysis, allows clot to stay intact for longer
What is von Willebrand’s disease?
It is a bleeding disorder caused by quantitative (types 1 and 3) or qualitative (type 2) deficiency of von Willebrand factor (vWF),
What does vWf do?
involved in both platelet function and coagulation. Carries Factor VIII.
What is type 1 vW disease
reduced amount of normal vW protein
What is vW disease type 2?
abnormal vW protein
What is vW disease type 2b?
Overactive protein which can result in thrombocytopenia
What is vW disease type 3?
little or no vW
What tests are used in vW disease?
Factor VIII, von willebrand antigen, vW activity
How do you differentiate between type 1 and type 2 vW disease?
vWF Activity to vWF Antigen is >0.6 = Type 1 and if <0.6 = Type 2
How do you treat type 1 vw disease?
DDAVP + tranexamic acid
How do you treat type 2 and type 3 vW disease
vWFactor
