week 2 Flashcards
requirements of haemostasis
permanent state of readiness
prompt response
localised response
protection against unwanted thrombosis
lifespan of platelet
7-10 days
function of a platelet
endothelial damage exposed collagen and releases von willebrand factor and other proteins to which platelets have receptors- platelet adhesion at the site of injury
secretion of various chemicals from the platelets leads to aggregation of platelets at the site of injury
consequences of failure of platelet plug formation
spontaneous bruising and purpura
mucosal bleeding
- epistaxes
- GI
- conjunctival
- menorrhagia
intacranial haemorrhage
retinal haemorrhages
failure of fibrin clot formation- causes
single clotting factor deficiency
- usually hereditary (haemophilia)
multiple clotting factor deficiencies
- usually acquired (DIC)
increased fibrinolysis
- usually part of complex coagulopathy
naturally occurring anticoagulants
serine protease inhibitors
protein C and protein S
failure of platelet plug formation- causes
vascular (hereditary of acquired)
platelets
- reduced number (thrombocytopenia)
- reduced function
von willebrand factor
causes of thrombocytopenia
hereditary
acquired
- reduced production
- increased destruction
causes of peripheral platelet destruction
coagulopathy: DIC
autoimmune: immune thrombocytopenic purpura
hypersplenism
acquired platelet functional defects
drugs (aspirin, NSAIDs)
renal failure
hereditary causes of thrombocytopenia
vWF deficiency
multiple factor deficiencies leading to failure of fibrin clot formation
liver failure
vit K deficiency/warfarin therapy
complex coagulopathy: DIC
screening tests for multiple factor deficiencies
prolonged prothrombin time and APTT
where are coagulation factors synthesised
hepatocytes
causes of vit K deficiency
poor dietary intake
malabsorption
obstructive jaundice
vit K antagonists- warfarin
haemorrhagic disease of the newborn
causes of DIC
sepsis
obstetric emergencies
malignancy
hypovolaemic shock
what is haemophilia A
factor VIII deficiency
what is haemophilia B
factor IX deficiency
screening test results in haemophilia
prolonged APTT
bleeding time, thrombin time, PT normal
clinical presentation of severe haemophilia
recurrent haemarthroses
recurrent soft tissue bleeds
prolonged bleeding after dental extractions, surgery and invasive procedures
most common inherited bleeding disorder
von willebrand’s disease
role of von willebrand factor
large glycoprotein which forms massive multimers
promotes platelet adhesion to damage endothelium
carrier molecule for factor VIII
investigation results for vWF
FBC-may be normal or may show microcytic anaemia or low platelet count
prolonged bleeding time
APTT may be prolonged
factor VIII levels may be moderately reduced
management of vWF
tranexamic acid for mild bleeding
desmopressin: raises levels of vWF by inducing release of vWF from weibel-palade bodies in endothelial cells
treatment of arterial thrombosis
aspirin and other anti-platelet drugs
treatment of venous thrombosis
heparin/warfarin/ new oral anticoagulant
treatment of ITP
- Prednisolone
- IV immunoglobulins
- Blood transfusionsif required
- Platelet transfusionsonly work temporarily
clinical presentation of ITP
- Usually present in children under 10 years old
- Often there is a history of a recent viral illness
- The onset of symptoms occurs over 24-48 hours:
- Bleeding, for example from the gums, epistaxis or menorrhagia
- Bruising
- Petechialorpurpuric rash, caused by bleeding under the skin
pathophysiology of ITP
- Caused by atype II hypersensitivity reaction
- It is caused by the production ofantibodies that target and destroyplatelets
- This can happen spontaneously, or it can be triggered by something, such as a viral infection
