Flashcards in Haematology Deck (51)
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1
What is APTT?
Activated partial thromboplasmin time
2
What is haemostasis?
Process whereby haemorrhage following vascular injury is arrested
Tightly regulated by vascular endothelium, platelets, coagulation factors and fibrinolysis
3
What is activated in injury of the vascular wall?
Tissue factor-> coagulation cascade
Collagen exposure and vWF-> platelet activation
Vasoconstriction-> stable plug
4
How does the endothelium usually act as an anticoagulant?
Prostacyclin, NO, heparin sulphate
5
What are platelets derived from?
Megakaryocyte shards
6
What stimulates platelet production?
Thrombopoetin
7
How long do platelets circulate for before being destroyed?
6-8 days
8
Describe the extrinsic pathway in the coagulation cascade
Tissue injury-> tissue factor and phospholipids
F7->F7a
F8-> F10->F10A
Prothrombin-> thrombin
Fibrinogen-> fibrin
9
Describe the extrinsic pathway in the coagulation cascade
-ve surface (collagen/plastic)
F12-F12A
F11-F11A
F9->F9A
F10-> F10A
Prothrombin-> Thrombin
Fibrinogen-> Fibrin
10
What initiates fibrinolysis?
Coagulation cascade
tPA (tissue plasminogen activator)
urokinase-like plasminogen activator
11
Plasminogen does what?
Turns into plasmin, degrades factor 5&7
Fibrin-> soluble products
12
What does a blood count and film show?
Number and morphology of platelets
May show leukaemia
13
When is PT (prothrombin time) extended?
Abnormal factor II, V, VII, X
Liver disease
Warfarin
Vitamin K deficiency
DIC
14
What is DIC?
Disseminated intravascular coagulation
Seen in septicaemia and post partum haemorrhage
15
When is APTT prolonged?
Deficiency/inhibition of II, V, VII, IX, X, XI, XII
Unfractionated heparin therapy
Vitamin K deficiency
DIC
16
What is a correction test?
Add normal plasma to patient's plasma so its 50:50
See if clotting time corrects
If it does it is a deficiency not an inhibitor
17
What do you look for in a bleeding disorder examination?
Signs of systemic diseases
Skin, mouth, fundi, joints
Easy bruising?
Purpura, bruising, petechiae
18
What is scurvy?
Vitamin C deficiency
19
What are Henoch-Schönlein purpura?
Small vessel vasculitis
Purple nodules that do not disappear on pressing
Intradermal bleeding
Seen in young males
+glomerulonephritis, joint pain, abdo pain
20
What is haemorrhagic telangiectasia?
Small red/purple clusters if dilated capillaries on skin or surface of organs
21
What is thrombocytopenia?
Low platelet count
Failure of production?
Increased consumption?
Dilutional?
Abnormal distribution?
22
What would cause a failure in the production of platelets?
Selective megakaryocyte depression
Dugs/chemicals/viral infections
Part of generalised bone marrow failure
Leukaemia, lymphoma, cancer
Aplastic anaemia
HIV
23
What would cause an increased consumption of platelets?
Immune/autoimmune
Drug induced (heparin)
Infections
DIC
24
What would cause dilutional thrombocytonpenia?
Massive blood transfusion
25
What do you treat congenital disorders if platelet function with?
Tranexamic acid, platelet transfusion
Avoid antiplatelet drugs
26
Give 2 examples of congenital disorders of platelet function
Bernard-Soulier
Glanzmann's
27
What would cause an acquired disorder of platelet function?
Antiplatelet agents (aspirin, NSAIDs)
Renal failure
Gammaglobulins
Cardiopulmonary bypass
Myeloproliferative disorders
28
Name 4 congenital coagulation disorders
Haemophilia A, Hameophilia B, vWF disease, Factor XI deficiency
29
What is tranexamic acid?
Blocks fibrinolysis
Used in haemophila and platelet function disorders
30
