Haemostasis Flashcards
What is haemostasis?
- the arrest of bleeding
- maintenance of vascular patency
What is needed for haemostasis?
- permanent state of readiness
- prompt response
- localised response (don’t want blood clots happening everywhere!)
- protection against UNWANTED thrombosis
What is involved in a NORMAL haemostatic system?
- formation of Platelet plug = Iary haemostasis
- formation of fibrin clot = IIary haemostasis
- fibrinolysis—prevent complete blockage of vessel
- anticoagulant defences
How are platelets formed?
- in the bone marrow by BUDDING from megakaryocytes (LARGE multinucleated cells)
How do platelets appear?
- enucleate cells
- –lasts for 7-10 dyas in the peripheral system
WHat occurs with endothelial damage?
- exposure of collagen occurs —-signals platelet to come
- release of VWF and other proteins with platelet receptors
- platelet adhesion at the site
- secretion of chemicals from the platelets > AGGREGATION of platelets
What does the VWF do>
- helps the platelet to stick to on another anf to the collagen
Why platelet plug formation does not occur?
- vascular (deficient COOLAGEN- in scurvy/ older people)
- Platelets (reduced #- BM fxn is poor/ incr. destruction OR reduced fxn—-those on ASPIRIN or corticosteroids)
- VWF
Consequences of FAILURE of platelet plug formation.
- Bruising and purpura (seen mostly in legs)
- Mucosal bleeding (Epistaxes/ GI/ conjunctival/ menorrhagia)
- intracranial hemorrhages
- retinal aemorrhages
Would bruising dissappear with glas pressure?
NO
How to screen for Primary haemostasis?
- PLATELET COUNT
- no simple screening tests for other components
WHat occurs with def. pf VWF?
- FACTOR viii deficiency
- IIary haemostasis problems
How does a fibrin clot form?
TF activates VII, activates V/X> activates THROMBIN (from prothrombin)> activate FIBRIN (from fibrinogen)
Explain the +ve feedback mechanism present to make a fibrin clot.
—-+ve feedback —presence of thrombin further activates VIII/Ixa> activate V/Xa even more —-more thrombin formed!
What is seen in single clotting factor deficiency?
- deficiency of factor VIII or IX (Hemoph. B)
- —usually hereditary (HEMOPHILIA)
WHen may Multiple clotting factor deficiencies occur>
- Acquired
- occurs with massive TISSUE damage: cancer/ RTA/ wrong blood given
- –(DIC)
Name another cause of incr. fibrinolysis .
- part of complex coagulopathy
WHat occurs in fibrinolysis?
What is the main enzyme?
- fibrin broken down to FDP
—–tPA needed to activate plasminogen in to PLASMIN
How to test for EXCESS fibrinolysis in the body?
D-dimers test
——check for why BLOOD clots may be forming (PE/ DVT)
What clinical pattern will you see in SINGLE clotting factors deficiency?
bleeding in to the JOINTs (ankle/ knee jts)
(HEMOPHILIA) —SWOLLEN
How may DIC appear?
- mass bruising (Purpura)/ INTERNAL bleeding
How do you know if pt has def. of VII ?
PT will be prolonged
How do you know if the pt has def. of VIII and IX?
- APTT will be prolonged
If PT and APTT is prolonged, what does it suggest>
MULTIPLE clotting factor deficiency
What are key qs to ask the pt?
—-have you bled for a LONG time after a dental extraction (good 3 days)
What to look for on P.E?
- spleen palpation
- checking muscles and joints for bleeding in hemophilia
- general internal bleeding
How does Heparin work?
- helps anti-thrombin to the job of INHIBITING thrombin
What does Protein C and protein S do?
inhibits factor V and VIII
What occurs with thrombophilia?
- def. of anticoagulants
- –incr. tendency to develop DVT and PE
- —seen in pts with PC/PS and anti-thrombin def.
