Haemostatis and Bleeding Disorders Flashcards
define haemostasis
arrest of bleeding and maintenaince of vascular patency
what is the primary stage of haemostasis?
formation of platelet plug
what is the secondary stage of haemostasis?
formation of fibrin clot
what is the lifespan of platelets and why is this important with regards to surgery?
7-10 days, if someone on anti-platelets need to stop medication week before surgery to achieve normal homeostasis level
failure of the platelet pluf formation can be caused by what?
vascular
platelets
Von willebrand factor
what are vascular causes of failure to form the platelet plug?
hereditary i.e. marfans
aquired i.e. vasculitis (HS purpura)
inc in age (lack of collagen)
what are platlet casues of failure to form platelet plug?
thrombocytopenia (reduced number)
renal disease (reduced function)
failure of platelet plug formation can result in what?
spontaneous bruising and purpura
mucosal bleeding
intracranial haemorrhage
retinal haemorrhage
what are the three ‘stages’ of platelet plug formation?
initiation
propagation
amplification
TF and VIIa activate what?
V and Xa
V and Xa activate what?
prthrombin
prothrombin is converted to what during platelet plug formation?
thrombin
thrombin stimulates further relase of which factors?
VIII and IXa
VIII and IXa activate more of which other factors?
V and Xa
fibrin is broken down by what?
plasmin
what converts plasminogen to plasmin?
tissue plasminogen activator
what is looked at in a coagulation screen?
prothrombin time
activated partial thromboplasmin time
FBC
what is the prothrombin time measuring?
Tissue factor and VIIa
what is the activated partial prothrombin time measuring?
VIII and IXa
what is the FBC used to look at in a coagulation screen?
platelet count
what is thrombophilia?
deficiency of naturally occuring anti-coagulants
what is the commenest cause of primary haemostatic failure?
thrombocytopenia
what can cause secondary haemostatic failure (fibrin clot)?
multiple or single clotting factor deficiences
what can cause multiple clotting factor deficiencies?
liver failure
Vit K deficiency/warfarin therapy
DIC
why does a vit K deficiency affect clotting factors?
required to make 2,7,9,10
how can obstrucitve jaundice i.e. pancreatic cancer/gallstones cause a clotting factor deficiency?
need bile salts for absoprtion of Vit K- without vit K can’t carboxylate 2,7,9,10
what can cause DIC?
sepsis
obstetirc emergencies
malignancy
hypovolaemic shock
what is a single clotting factor deficiency?
hameophilia
which is more common haemophilia A or B?
A
which clotting factor is deficient in haemophilia A and in B?
A - factor VIII
B- factor IX
what mode of inheritance is haemophilia?
X-linked
what occurs in someone with haemophilia?
recurrent haemarthroses, soft tissue bleeds
prolonged bleeding after dental extractions/surgery
atypical picture of menorrhagia and easy bruising would suggest deficiency of what?
Von Willebrand Factor
where do people with haemophilia most commnly suffer haemarthroses?
ankle/knee- this is where you’re most liekly to bump/twist
elevated PT time would indicate deficeincy in?
TF and VII
elevated APTT would indicate deficiency in?
VIII and IX
platelet adhesion at injury sites occut via what?
glycoprotein 1b and VWF
what is dipyridamole?
phosphodiesterase inhibitor- reduces cAMP production
