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Year 2 - MCD Haem > Abnormalities of Haemostasis > Flashcards

Abnormalities of Haemostasis Flashcards

1
Q

What is included in minor bleeding symptoms?

A

Easy bruising
Gum bleeding
Epistaxes (frequent nosebleeds)
Menorrhagia (women)

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2
Q

What counts as significant bleeding history?

A
  • Epistaxis not stopped by 10mins of compression
  • Cutaneous haemorrhage/bruise WITHOUT apparent trauma
  • Prolonged bleeding from trivial wounds
  • Menorrhagia requiring treatment or leads to anaemia
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3
Q

Why do people have abnormal haemostasis?

A
  1. LACK of a specific factor

o Failure of production - congential or acquired
o Increased consumption/clearance

  1. DEFECTIVE FUNCTION of a specific factor

o Genetic defect
o Acquired defect - drugs, synthetic defect, inhibition

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4
Q

Where can the problem lie with 1o haemostasis?

A

Formation of unstable platelet plug (2)

SO

Defects can lie in:
o platelets
o vWF
o collagen

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5
Q

How can a defect in platelets result in abnromal haemostasis?

A
  1. Low numbers - THROMBOCYTOPENIA

o Bone marrow failure e.g. leukaemia, B12 deficiency
o Accelerated clearance e.g. ITP, DIC
o Pooling and destruction in splenomegaly

  1. Impaired funcion

o Hereditary absence of glycoproteins (GpIIb/IIIa/Ib) /storage-granules (ATP etc.)
o Acquired from drugs e.g. aspirin, NSAIDs, Clopidogrel

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6
Q

How does auto-ITP work?

A

Auto-Immune Thrombocytopenic Purpura

  1. Anti-platelet Abs attack platelets
  2. These are engulfed by splenic macrophages

VERY common cause of thrombocytopenia

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7
Q

What can thrombocytopenia cause?

A
  1. Failure of platelet production by megakaryocytes
  2. Shortened half-life of platelets
  3. Increased pooling of platelets in an enlarged spleen (hypersplenism)
    - also reduces its half-life in the spleen
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8
Q

What can a defect in vWF lead to?

A

Von Willebrand Disease

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9
Q

Explain the two forms Von Willebrand disease can form

A
  1. Hereditary DECREASE of quanity & function (most common form)
    o Type 1 & 3 = DEFICIENCY of vWF
    o Type 2 = ABNORMAL FUNCTION of vWF
  2. Acquired due to an Ab (RARE)
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10
Q

What 2 functions does vWF have in haemostasis?

A
  1. Binding to collagen (to capture platelets)

2. Stabilising F8 (F8 may be low if vWF is very low)

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11
Q

Explain how defects in collagen/vessel wall can lead to abnormal haemostasis

A

o Inherited (rare)

  • hereditary haemorrhagic telangisctasia
  • Ehlers-Danlos syndrome (ONENOTE!)
  • connective tissue disorders

o Acquired

  • scruvy
  • steroid therapy
  • ageing (senile purpura)
  • vasculitis
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12
Q

How can thrombocytopenia & severe vWF present clinically?

A

Thrombocytopenia = PETECHIAE
(very characteristic of LOW platelet count)

Severe vWF = haemophilia-like bleeding

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13
Q

What tests can you do to test disorders of 1o haemostasis?

A
  1. Platelet count / morphology
  2. Bleeding time (PFA100 in lab)
  3. Assays of vWF
  4. Clinical observation
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14
Q

Where can the problem lie with 2o haemostasis?

A

Stabilsiation of the plug with fibrin (3)

SO

with blood coagulation i.e. CROSSLINKED FIBRIN

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15
Q

Haemophilia Factor 8?

A

Failure of THROMBIN GENERATION
(due to F8 defects)

Thrombin provides much of the +VE feedback to convert fibrinogen –> fibrin

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16
Q

What does haemophilia Factor 8 mean for small and large vessel injury then?

A

Small vessel injury = 1o platelet plug is sufficient

Large vessel injury = 1o platelet plug will FALL apart

(remember - fibrin stabilises the platelet plug!)

17
Q

Define haemophilia

A

Failure to generate fibrin to stabilise the platelet plug

18
Q

What can decreased crosslinked fibrin be due to then?

A
  1. Deficiency of factor production

OR

  1. Increased consumption of factors
19
Q

Explain how deficiency of factor production can lead to decreased crosslinked fibrin

A

Either hereditary or acquired

1. Hereditary
 o F8/9 - Haemophilia A/B
   - severe but compatible w. life
   - haemarthrosis (joint/muscle bleeding)
 o F2 (prothrombin)
   - lethal!
 o F11
   - bleed after trauma
   - NOT spontaneous
 o F12
   - NO excess bleeding at all
  1. Acquired - MORE COMMON
    o Liver disease (decreased production)
    • most coagulation factors synthesised here

o Dilution e.g. transfusions
- RBC transfusions do NOT contain plasma unless major transfusion

o Anticoagulant drugs e.g. Warfarin

20
Q

Explain how increased consumption of factors can lead to decreased crosslinked fibrin

A

ALWAYS ACQUIRED

o DIC - disseminated intravascular coagulation

  • Generalised activation of coagulation via. TF
  • Associated w. sepsis, major tissue damage, inflammation
  • Consumers & depletes coagulation factors, platelets and fibrinogen (via. activation of fibrinolysis)
  • Deposits of fibrin in vessels = organ failure

o Immune - auto-Abs

21
Q

Typical bleeding patterns in 2o haemostasis coagulation disorders?

A
  1. Superficial cuts do NOT bleed - as platelets
  2. Bruising is common BUT nosebleeds are RARE
  3. Spontaneous bleeding is deep, into muscles & joints
  4. Bleeding after trauma may be delayed and is prolonged
  5. Bleeding frequently restarts after stopping
22
Q

What should be avoided in patients w. haemophilia (or a 2o defect)?

A

Intramuscular injections!!

look at ONENOTE picture

23
Q

Clinical distinction between bleeding due to platelet and coagulation defects?

A

Platelet/Vascular
o SUPERFICIAL bleeding into skin, mucosal membranes
o Bleeding IMMEDIATELY after injury

Coagulation
o Bleeding into DEEP tissues, muscles, joints
o DELAYED but SEVERE after injury
o Bleeding often PROLONGED

24
Q

Tests for 2o haemostasis?

A
  1. Screening tests (‘clotting screen’)
    o Prothrombin time (PT)
    • Extrinsic & common pathway defects (12,11,9,8,5,10,2)
      o Activated partial thromboplastin time (APTT)
    • Intrinsic & common pathways defects (7,5,10,2)
      o FBC (for platelets)
  2. Factor assays e.g. for F8
  3. Tests for inhibitors
25
Q

How will haemophilia present through the tests?

A

NORMAL PT & TT (thrombin time)

BUT

and ABNORMAL APTT
- as the intrinsic pathway is affected

26
Q

What bleeding disorders are NOT detected by routine clotting tests?

A

o Mild factor deficiencies
o vW disease
o F13 deficiency (to cross-link fibrin)
- common pathway measured in BOTH APTT & PT

o platelet disorders
o excessive fibrinolysis
o vessel wall disorders
o metabolic disorders e.g. uraemia
o thrombotic disorders
27
Q

Where can the problem lie with fibrinolysis?

A

Dissolution of clot and vessel repair (4)

Issue lies with fibrinolysis

28
Q

Explain disorders of fibrinolysis

A

Can cause abnormal bleeding but are RARE

o Hereditary - antiplasmin deficiency

o Acquired

  • drugs e.g. tPA
  • DIC
29
Q

Genetics of haemophilia?

A

Sex-linked recessive

30
Q

Genetic of Von Williebrand Disease?

A

Autosomal!

Type 1 & 2 = dominant
Type 3 = recessive

31
Q

Genetics of the other common bleeding disorders?

A

E.g. Factor 5 Leiden etc.

Autosomal recessive
and therefore MUCH less common

32
Q

Treatment of 3 main reasons for abnormal haemostasis?

A
  1. Failure of production/function
    o Replace missing factors/platelets (prophylacticlly or therapeutically)
    o STOP drugs causing it
  2. Immune destruction
    o Immunosuppression e.g. prednisolone
    o Splenectomy for ITP
  3. Increased consumption
    o Treat cause
    o Replace as necessary
33
Q

2 main therapies for abnormal haemostasis treatment?

A
  1. FACTOR replacement therapy
    o Plasma - contains ALL coagulation factors

o Cryoprecipitate - rich in fibrinogen, F8, vWF, F13

o Factor concentrates - concentrated available for all factors EXCEPT F5
(prothrombin complex concentrates F2,7,9,10 - PCC)

o Recombinant forms of F8 and F9

  1. PLATELET replacement therapy
    o pooled platelet concentrates available
34
Q

3 additional haemostatic treatments?

A
  1. DDAVP
  2. Tranexamic acid
  3. Fibrin glue/spray
35
Q

DDAVP?

A

Desmopressin - vasopressin derivative

Results in 2-5x rise in vWF and F8
- by stimulating endothelial cells to release internal stores (endogenous stores)

o ONLY useful in mild disorders
o Only when DO NOT have enough (NOT for intrinsic dysfunction)

36
Q

Tranexamic acid?

A

SLOWS DOWN the breakdown of clots

o Inhibits fibrinolysis
o Widely distributed in the body
- can cross the placenta
- BUT does have a [low] in breast milk

Delivered by IV, oral or mouthwash

Year 2 - MCD Haem (11 decks)

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