Bleeding Disorders Flashcards
when is a fibrin clot added to a platelet plug?
when injury is more severe and plug needs stabilised
what parts of the haemostatic system usually fail to cause bleeding disorders?
platelet plug (primary haemostasis) fibrin clot (secondary haemostasis)
3 main components of platelet plug?
vascular endothelial wall
platelets
von willebrand factor
what platelet issues can cause problems forming platelet plug?
reduced number (thrombocytopaemia) reduced function
how to problems with VWF usually occur?
inherited
usually reduced amount
what can cause vascular abnormalities?
hereditary (marfans syndrome, collagen problems etc)
acquired
- vasculitis (e.g Henoch schonlein purpura in children)
- scurvy (vit C deficiency causing collagen issues in vessel wall)
where might purpura appear?
fundus
mouth
lower limb
across chest while coughing (during increased pressure)
is thrombocytopaenia usually hereditary or acquired?
acquired
causes of acquired thrombocytopaenia?
reduced production of platelets (bone marrow problem (leukaemia, lymphoma, infiltration etc)
increased destruction of platelets (often immune issue)
clues of increased platelet destruction on blood film?
platelets get a lot smaller as they approach end of lifespan
what can cause peripheral platelet destruction?
coagulopathy (DIC - lots of clotting and breakdown of clots uses up clotting factors, can occur in trauma eg RTA)
autoimmune (immune thrombocytopaenic purpura etc)
hypersplenism (platelets get trapped in spleen reducing overall platelet count)
what can cause platelet problems when platelet count is normal?
platelet functional defects
can be hereditary or acquired (most commonly acquired)
what can cause acquired platelet functional defects?
drugs (aspirin, NSAIDs, drugs used to prevent thrombosis) renal failure (toxins e.g uraemia which build up in failing kidney can cause problems in platelets)
Von Willebrand Factor (vWF) deficiency is usually hereditary or acquired?
hereditary
- autosomal dominant
how will vWF deficiency present?
usually mild mucosal bleeding (nose bleeds, bleeding gums, menorrhagia etc)
commonest cause of primary haemostatic failure?
thrombocytopaenia usually acquired (e.g marrow failure or peripheral destruction)
what usually causes multiple clotting factor deficiency (failure of formation of fibrin clot)?
generally acquired (Eg complex coagulopathy such as DIC - clotting factors used up faster than you can make them, so clotting problem then becomes bleeding problem) can be due to liver failure vit K deficiency/warfarin therapy
what can cause DIC?
trauma
sepsis
what usually causes single clotting factor deficiency (failure of formation of fibrin clot)?
generally hereditary (e.g haemophilia)
why does liver failure cause multiple clotting factor deficiency?
CFs all made in hepatocytes of liver
which clotting factors need vitamin K?
2, 7, 9 and 10 are carboxylated by vit K
- therefore vit K deficiency can cause deficiency and bleeding problem
vit K sources?
diet
bacteria in the bowel synthesis vit K
- babies don’t have the bacteria so need a vit K injection at birth to prevent bleeding (haemorrhagic disease of newborn)
where is vit K absorbed?
upper intestine
required bile salts
causes of vit K deficiency?
poor dietary intake (lack of green leafy veg) malabsorption obstructive jaundice vit K antagonists (warfarin) haemorrhagic disease of newborn
what is disseminated intravascular coagulation?
tissue damage leading to excessive and inappropriate activation of all aspects of the haemostatic system (primary, secondary and fibrinolysis)
first response to damage leads to microvascular thrombus formation causing end organ failure (kidneys, lungs etc)
body then tries to break down all the clots while more clots continue to form
clotting factors are used up quickly leading to bruising, purpura and generalised bleeding
which clotting factor has the shortest lifespan?
CF 7
- therefore prothrombin time tested first as CF 7 will be the first one affected if theres a problem
causes of DIC?
sepsis
obstetric emergencies (abruption)
malignancy (tends to be more chronic and slow progressive, common in adenocarcinoma and bowel cancer)
hypovolaemic shock
how is DIC managed?
treat underlying cause replacement therapy - platelet transfusions - plasma transfusions - fibrinogen replacement (cryoprecipitate)
what is haemophilia?
hereditary disorder in which abnormally prolonged bleeding recurs episodically at one or a few sites on each occasion
causes fragile blood vessels?
lack of CF 8 or 9
how is haemophilia inherited?
X linked (only affects males)
types of haemophilia?
A = CF 8 deficiency (5X more common) B = CF 9 deficiency
problems in haemophilia?
no abnormality of primary haemostasis
- can form platelet plug fine so small cuts (e.g paper cut isn’t affected)
large bleeding from medium to large blood vessels
can be mild-mod-severe depending on level of CF8/9
screening tests in haemophilia?
prothrombin time is normal (TF, CF7, CF5 and CF10 are normal)
very prolonged activated partial thromboplastin time
clinical features of haemophilia?
recurrent haemarthroses
recurrent soft tissue bleeds (bruising in toddlers etc)
prolonged bleeding after dental extractions, surgery and invasive procedures
how can haemophilia be managed?
IV clotting factor every second day
