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Haematology > Disorders of haemostasis > Flashcards

Disorders of haemostasis Flashcards

1
Q

What are some common but minor bleeding conditions?

A
  • Easy bruising
  • Gum bleeding
  • Frequent nosebleeds
  • Bleeding after tooth extraction
  • Post operative bleeding
  • Family history
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2
Q

What are some common bleeding problems in women?

A
  • Menorrhagia

- Post partum bleeding

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3
Q

What are some elements that would be found through a history in a person with a bleeding disorder?

A
  • Epistaxis not stopped by 10 minutes of compression or requiring medical attention/transfusion
  • Bruising without apparent trauma
  • Prolonged (>15m) bleeding from trivial wounds/in oral cavity/recurring spontaneously in 7 days after wound
  • Spontaneous GI bleeding leading to anaemia
  • Menorrhagia requiring treatment or leading to anaemia
  • Heavy, prolonged or recurrent bleeding after surgery or dental extractions
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4
Q

What 2 things cause abnormal haemostasis?

A
  • lack of a specific factor (not made: congenital or acquired or increased consumption/clearance)
  • defective function (genetic of acquired through drugs etc)
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5
Q

What is primary and secondary haemostasis?

A
  • primary: formation of unstable platelet plug involving adhesion and aggregation
  • secondary: stabilisation with fibrin
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6
Q

What are the components of primary haemostatsis?

A
  • The platelets, with their receptors (GlpIa/GlpIb)
  • Von Willebrand factor (acting as a bridge between the platelet and the damaged endothelial surface)
  • The vessel wall
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7
Q

What are the 2 ways in which platelets can bind to form the platelet plug?

A

You have either direct binding of the platelets by GlpIa to collagen, or indirect binding via vWF by GlpIb. Platelets become activated, and aggregate via GlpIIb/IIIa to form the platelet plug

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8
Q

What can cause problems with primary haemostasis - platelets?

A

Low Numbers

  • Bone marrow failure e.g. malignancy (leukaemia), megaloblastic anaemia (B12 deficiency)
  • Accelerated clearance of platelets e.g. DIC, auto ITP
  • Pooling and destruction in an enlarged spleen

Impaired function

  • Hereditary absence of glycoproteins or storage granules
  • Acquired due to drugs: aspirin, NSAIDs
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9
Q

What is autoimmune thrombocytopenia purpura (auto-ITP)?

A
  • Platelet autoantibodies are coating the platelet, sensitising it
  • These complexes are cleared by the reticulo-endothelial system.
  • Autoimmune thrombocytopenia purpura is a common cause of thrombocytopenia
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10
Q

What are the mechanisms and causes of thrombocytopenia?

A
  1. Failure of platelet production by megakaryocytes
  2. Shortened half life of platelets
  3. Increased pooling of platelets in an enlarged spleen (hypersplenism) + shortened half life
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11
Q

What are some hereditary platelet defects?

A

Glanzmann’s thrombasthenia: rare, autosomal recessive disorder, in which GpIIb/IIIa is lacking

Bernard Soulier syndrome: autosomal recessive, lack of Gp1b

Storage Pool Disease: broad term, referring to issues with granular storage and release

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12
Q

What is VW disease?

A

Hereditary decrease of quantity +/ function

OR
Acquired due to antibody – acquired von Willebrand Syndrome

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13
Q

What are the 2 functions of VWF in haemostasis?

A
  • Binding to collagen and capturing platelets

- Stabilising Factor VIII

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14
Q

What is type 1,2 and 3 VWD?

A

Type 1 most common – you make some VWF
Type 3 – you make no VWF
Type 2 – qualitative defects so what you’re making doesn’t work

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15
Q

What are some disorders of primary haemostasis - vessel wall?

A

Inherited (rare): hereditary haemorrhagic telangiectasia, Ehlers-Danlos syndrome and other connective tissue disorders

Acquired defects of the vessel wall: scurvy, steroid therapy, ageing (senile purpura), vasculitis

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16
Q

What is the pattern of bleeding in people with primary haemostasis defects?

A
  • Immediate, prolonged bleeding
  • Easy bruising
  • Nosebleeds (prolonged: >20 mins)
  • Gum bleeding (prolonged)
  • Menorrhagia (anaemia)
  • Bleeding after trauma/surgery
  • Petechiae (specific for thrombocytopenia)
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17
Q

What is petechiae?

A
  • small blood spots
  • occur in people who are thrombocytopenic
  • appear spontaneously
  • characteristic of low platelet count
18
Q

What are the tests done for disorders of abnormal haemostasis?

A
  • Platelet count, platelet morphology (using microscopy)
  • Bleeding time
  • Assays of VWF
  • Clinical observation
19
Q

What is a thrombogram?

A
  • Shows thrombin generation
  • Someone with haemophilia produces very little thrombin
  • The role of the coagulation cascade is to generate a burst of thrombin, which will convert fibrinogen to fibrin
  • Deficiency of any coagulation factor results in a failure of thrombin generation and hence fibrin formation
20
Q

Why is the platelet plug not sufficient?

A
  • The primary platelet plug is sufficient for small vessel injury
  • In larger vessels it will fall apart
  • Fibrin formation stabilises the platelet plug
21
Q

Why do people with secondary haemostasis disorders have delayed bleeding?

A
  • Someone with haemophilia has a very feeble thrombin burst (not very big)
  • They have the primary platelet plug
  • They need to generate fibrin mesh – not enough thrombin -> plug will fall apart -> delayed bleeding
22
Q

What are some disorders of secondary haemostasis (deficiency or defect of factors)?

A

Genetic: Haemophilia A/B

Acquired: Liver Disease
Most coagulation factors are synthesised in the liver. However, anticoagulants are also made by the liver – so this tends to balance out

Acquired: Drugs (warfarin - inhibits synthesis of coagulation factors)

Acquired: Dilution (results from volume replacement) – you need to give RBC and Plasma

Acquired: Disseminated intravascular coagulation

23
Q

Describe how severe lethal each of the following factor deficiencies are:

  • prothrombin
  • 11
  • 12
  • 8 and 9 (haemophilia)
A

haemophilia: severe but compatible with life
prothrombin: lethal

11 - bleed after trauma not spontaneous so not as severe

12 - no excess bleeding at all

24
Q 
What is DIC?
Cause?
When does it happen?
What is the mechanism?
How can it lead to organ failure?
A
  • Also called consumptive coagulopathy
  • Results from abnormal activation of coagulation
  • Generalised activation of coagulation - Tissue Factor is triggered -> uncontrolled coagulation
  • Consumes and depletes coagulation factors and platelets -> platelets consumed
  • Activation of fibrinolysis depletes fibrinogen -> lots of fibrin degradation products
  • Deposition of fibrin in vessels causes organ failure
  • Associated with sepsis, some obstetrics causes, major tissue damage, inflammation
25
Q

What are the consequences of DIC?

A
  • Widespread bleeding, from IV lines, bruising, internal

- Deposition of fibrin in vessels causes organ failure

26
Q

What is the pattern of bleeding in secondary haemostasis?

A
  • Often delayed (after primary haemostasis)
  • Prolonged – but may come into hospital several times due to stop-start bleeding
  • Deeper: joints and muscles - Don’t tend to get excessive bleeding from small cuts (primary haemostasis is ok)
  • Bruising is common
  • Nosebleeds are rare
  • Bleeding after trauma/surgery may be delayed, and is prolonged
  • Bleeding after intramuscular injection
27
Q

What is haemarthrosis?

A

Hallmark of haemophilia– bleeding into the joints

  • This is a characteristic feature of severe haemophilia A and B
  • They bleed into joints -> pressure builds up -> the joint becomes swollen and painful
  • Haemophiliac patients have prophylaxis to prevent this
28
Q

What should never be given to a person with a clotting factor deficiency?

A

intramuscular injection

29
Q

What are the tests for secondary haemostasis disorders?

A
  • Screening tests (‘clotting screen’): PT, APTT (measure time taken for clottting) and full blood count (platelets)
  • Factor assays (for Factor VIII etc.)
  • Tests for inhibitors
30
Q

What happens to PT and APTT in haemophila and why?

A
  • APTT is prolonged because you are not making factor 8 or 9

- PT will be normal (extrinsic pathway not affected)

31
Q

What is APTT and PT?

A

PT measures the integrity of the extrinsic system as well as factors common to both systems

Partial Thromboplastin Time (PTT), which measures the integrity of the intrinsic system and the common components

32
Q

What are some bleeding disorders not detected by routine clotting tests?

A
  • Mild factor deficiencies
  • Von Willebrand disease
  • Factor XIII deficiency
  • Platelet disorders
  • Excessive fibrinolysis
  • Vessel wall disorders
  • Metabolic disorders (e.g. uraemia)
33
Q

What are the disorders of fibrinolysis?

A

Hereditary: antiplasmin deficiency

Acquired: drugs such as tPA, DIC

34
Q

How is haemophilia inherited?

A
  • Haemophilia is a sex-linked recessive disorder
  • Haemophilia A and B are both X-linked
  • The varying degrees of lyonization (one X randomly inactivated) results in the varying levels of genes being carried
35
Q

How is VWD inherited?

All three types

A
  • Von Willebrand disease is autosomal
  • Type 1 can be dominant, 2 is autosomal dominant
  • Type 3 is recessive
36
Q

How is abnormal haemostasis treated?

A

Failure of production/function

  • Replace missing factor/platelets
  • Stop drugs causing this

Immune destruction (e.g. immune thrombocytopenia)

  • Immunosuppression (e.g. prednisolone)
  • Splenectomy for ITP

Increased consumption

  • Treat the cause of the DIC
  • Replace what is missing as necessary
37
Q

What are the different factors replacement therapies?

A

Plasma: Contains all coagulation factors

Cryoprecipitate: Rich in Fibrinogen, FVIII, VWF, Factor XIII

Factor concentrates

  • Concentrates available for all factors except factor V
  • Prothrombin complex concentrates (PCCs) Factors II, VII, IX, X
  • Recombinant forms of FVIII and FIX are available

Gene therapy: for haemophilia A and B

Novel approaches: antibodies, antithrombin RNAi

Platelet replacement therapy: pooled platelet concentrates available

38
Q

What are some other haemostatic treatments?

A

DDAVP (desmopressin) – release the body’s own stores of VWF and F8 (for von Willebrand disease)

Tranexamic acid – anti-fibrinolytic

Fibrin glue/spray

39
Q

What is desmopressin?

A
  • A vasopressin derivative (analogue)
  • It causes a 2-5 fold rise in VWF and VIII (there is a secondary rise in F8)
  • It causes the release of these from endogenous stores – hence it is only useful in mild disorders
40
Q

What is tranexamic acid?

A
  • Inhibits fibrinolysis – competitively inhibits binding of tPA to fibrin
  • Widely distributed, and crosses the placenta (but low concentration detected in breast milk)
  • Useful adjunctive therap
41
Q

How is DDVAP administered?

A

This can be given as a nasal spray or intravenously

  • Intranasally: 300 micrograms administered -> peak response seen in 60-90 minutes
  • Intravenously: 0.3 micrograms/kg -> peak response seen in 30-60 minutes
42
Q

How is tranexamic acid administered?

A
  • Intravenous: 0.5g tds
  • Oral: 1.5g tds
  • Mouthwash: 1g (10ml 5%) qds

Haematology (11 decks)

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