Intro to haemostasis Flashcards
what is haemostasis
the arrest of bleeding and the maintenance of vascular patency
requirements of haemostasis
permanent state of readiness
prompt response
localised response
protection against unwanted thrombosis
what are the components of the normal haemostatic system
formation of a platelet plug - primary haem - should be enough
formation of a fibrin clot - secondary haem - if needs more - on the platelet surface
fibrinolysis - breaking down of the fibrin clot
anticoagulant defences
how are platelets formed and where
in the bone marrow by budding from megakaryocytes
what are platelets and their life span
small anucleate disc with a mean life span of 7-10 days
what does the endothelial damage expose and what does this mean
exposes collagen and releases Von Willebran Factor and other proteins to which platelets have receptors
platelet adhesion at the site of injury
what leads to aggregation of platelets at the site of injury
secretion of various chemicals from the platelets
how long before a surgery should aspirin be stopped and why
7 days
platelets life span is 7-10 days
what are some causes of failed platelet plug formation
vascular - lack of collagen which is usually in old age, inflammation that affected the vessel wall
platelet causes - reduced number (thrombocytopenia), reduced function
von willibrand factor - reduced levels or doesn’t function properly - inherited
what are the consequences of failed platelet plug formation
spontaneous bruising and purpura
mucosal bleeding - epistles, GI, conjunctival, menorrhagia
intra cranial haemorrhages
retinal haemorrhages
screening tests for primary haemostasis
platelet count is the only one
causes of failure of a fibrin clot formation
single clotting factor deficiency - usually hereditary such as haemophillia
multiple clotting factor deficiencies - usually acquired such as DIC
increased fibrinolysis usually part of complex coagulopathy
consequences of failure of fibrin clot formation
may be combined primary and secondary
pattern of bleeding depends on single/multiple abnormalities and the clotting factors involved
haemophilia bleeding
bleed into joint and muscles esp in ankles and knees
screening tests for fibrin clot formation
Prolonged prothombin – problem on the side of factor 7
APT prolonged – problem with factor 8 or 9 but also can be 11/12
If both prolonged – multiple clotting factors or one up the middle
Less commonly the ones in the middle
Warfarin affects the prothrombin side more – 7 is more sensitive so prothrombin time is used to monitor
And herparin – APT is used to monitor as it affects that side more
Tissue factor and phospholipid
