Coagulopathies - BB Flashcards
3 groups to break down bleeding disorders into:
- Abnormal coagulation cascade
- – Haemophelia, vitamin K deficiency - Abnormal platelets
- — Bernard-Soulier, Glanzmann’s Thrombasthenia
- ITP
- TTP
- Uraemia - Mixed disorders
- Von Willebrand Disease, DIC, Liver disease
Coagulation tests and what they look at: (x5)
- Bleeding time - platelet function
- PTT - Intrinsic pathway of clotting cascade
- PT - Extrinsic pathway
- INR - PT (patient)/ PT (control)
- Thrombin time - Tests for presence of thrombin inhibitor
- Thrombin added and time to clot measured - thrombin far down cascade so specific
Difference in types of bleeding between coagulation cascade and platelet abnormalities
Abnormal platelets - mucosal/ skin bleeding (superficial)
- Petechiae (small red dots)
Abnormal coagulation factors - joint bleeding, deep tissue bleeding
Haemophelia: general
X-Linked recessive
Familial and also de novo (dont assume that no fam history means not a haemophelia)
Haemophelia A - deficiency in factor VIII
Haemophelia B - deficiency in factor IX (christmas disease)
Presentation of haemophelia:
Spontaneous or easy bruising
Recurrent joint bleeding - common presentation
PTT prolonged - (because VIII and IX are intrinsic pathway factors)
PT, bleeding time and platelet count all NORMAL
Treatment for haemophelia: (x3)
- Replacement of factor VIII/IX (inravenous)
- – Either scheduled regularly or before when they need it
- Desmopressin (dDAVP)
- – Used in mild haemophelia A
- – Analogue of vasopressin (ADH) with no pressor activity but …
- – Increases vWF and fVIII levels from weibel-palade bodies of endothelial cells
- also useful in von Willebrand
- Aminocaproic acid
- – Antifibrinolytic drug
- – Inhibits plasminogen –> plasmin conversion
- – Less breakdown of clots formed
- Cryoprecipitate
- – Obsolete now but was used for haemophelia A (before factor VIII could be isolated)
- – Mixture that is high in factor VIII and fibrinogen
Desmopressin side effects and other uses:
Has vasodilating properties and thus side effects are:
- Flushing and headache
Other uses:
- von Willebrand disease
- Central diabetes insipidus - mimicks ADH
- Betwetting in children - (decreases urine volume)
Cryoprecipitate:
Precipitate that forms when FFP (fresh frozen plasma) is thawed
Seperated from plasma by centrifugation
High in factor VIII and fibrinogen — Also factor XIII and vWF
Nowadays used as a source of fibrinogen in:
- DIC
- Massive trauma with blood transfusions
Coagulation factor inhibitors:
Antibodies directed at clotting factors
They inhibit activity or increase clearance of the clotting factors
Antibodies against factor VIII are the most common - present similar to haemophelia A
Coagulation factor inhibitors often occur in association with:
Malignancy
Post-partum
Autoimmune disorders
Treatment of coagulation factor inhibitors
Can be treated with prednisolone
HENCE important to distinguish between haemophelia A
Presentation of coagulation factor inhibitors - how to differentiate between haemophelia A
Deficient activity of VIII - causing bleeding
Prolonged PTT
Differentiated from haemophelia A using mixing study
- haemophelia will correct to normal
- PTT will still be raised in presence of inhibitors
Vitamin K deficiency
Results in bleeding
Deficiency in vitamin K dependent factors:
- II, VII, IX, X (both intrinsic and extrinsic - but extrinsic are first to fall because they have a shorter half life)
Lab findings in patient with vitamin K deficiency:
Elevated PT/INR
Elevated PTT posible - but less sensitive (intrinsic pathway K dependent factors have longer half life)
Causes of a vitamin K deficiency:
Dietary deficiency is rare because …
GI bacteria produce sufficient quantities
Common causeses:
1. Warfarin therapy - antagonises vitamin K
- Antibiotics - deplete GI bacteria that produce vitamin K
- Newborns - that have sterile GI tract
- – Given vitamin K injection at birth
- Malabsoption - vitamin K is fat soluble so anything that leads to poor absorption of fat soluble vitamins
- Blood transfusions - large vol. transfusions dilute clotting factors - treated with FFP (fresh frozen plasma)
