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Year 2 Collin > Haem 8 - Abnormalities of haemostasis > Flashcards

Haem 8 - Abnormalities of haemostasis Flashcards

1
Q

Platelet adhesion can occur via VWF or?

A

GP1A directly to endothelial cells

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2
Q

How does platelet aggregation occur?

A

ADP and TXA2 release–> platelet aggregation via GP2B/3A receptors

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3
Q

Primary haemostasis can go wrong at 3 points, which are

A
  1. Platelet
  2. VWF
  3. Vessel wall
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4
Q

Disorders of primary haemostasis may occur due to problems in platelets. How

A

Low numbers

  1. Bone marrow failure - e.g. leukaemia, B12 deficiency
  2. Accelerated clearance - e.g. immune thrombocytopenia, DIC

Impaired function

  1. Hereditary absence of glycoproteins or storage granules (e.g. Glanzmanns thrombasthenia - defective GP2B, Bernard Soulier syndrome -GP1B, Storage pool disease - problem with dense granules)
  2. Acquired due to drugs - aspirin, NSAIDs, clopidogrel
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5
Q

What is immune thrombocytopenia

A

Antiplatelet autoantibodies attach onto sensitised platelet –> cause it to be phagocytosed by a macrophage

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6
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 platelet pooling in an enlarged spleen (hypersplenism) and shortened half life
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7
Q

Disorders of primary haemostasis may be due to VWF. How

A
  1. Von Willebrand Disease - hereditary decrease of quantity and/or function OR acquired due to antibody

VWD is usually hereditary - Deficiency = type 1/3
Abnormal function = type 2

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8
Q

What are the roles of VWF

A
  1. Bridge between platelet and subendothelium (collagen)

2. Carrier protein for F8

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9
Q

Disorders of primary haemostasis may be due to vessel wall. How

A
  1. Inherited (rare) hereditary haemorrhagic telangiectasia / (Ehlers Danlos syndrome) and other connective tissue disorders
  2. Acquired - scurvy/steroid therapy/ageing/vasculitis
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10
Q

What is characteristic of thrombocytopenia (primary haemostasis)

A

Petechiae

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11
Q

What are the tests for disorders of primary haemostasis

A
  1. Platelet count, platelet morphology
  2. Bleeding time
  3. VWF assays
  4. Clinical observations
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12
Q

Primary platelet plug is sufficient for small vessel injury. In larger vessels it falls apart. Fibrin formation stabilises the platelet plug. So describe what the disorders of coagulation could be

A

Deficiency of coagulation factor production -

  1. Hereditary e.g. haemophilia A/B - F8/9
  2. Acquired - liver disease, dilution, anticoagulant drugs

Increased consumption -

  1. Disseminated intravascular coagulation (DIC)
  2. Immune - antibodies
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13
Q

Coagulation factor deficiencies can vary in severity. Describe

A

Haemophilia A/B = severe, but compatible with life. Spontaneous joint and muscle bleeding

Prothrombin deficiency (F2) = lethal

Factor 11 deficiency = bleed after trauma but not spontaneously

F12 deficiency = no excess bleeding at all

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14
Q

Describe what Disseminated intravascular coagulation is

A

It is generalised activation of coagulation - tissue factor.

Occurs in sepsis, major tissue damage, inflammation, etc

It consumes and depletes coagulation factors (so they can’t be used when actually needed)

Platelets consumed, and activation of fibrinolysis depletes fibrinogen

Fibrin deposition in vessels causes organ failure

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15
Q

Describe bleeding pattern in coagulation disorders

A
  1. Superficial cuts don’t bleed
  2. Bruising common, nosebleeds rare
  3. Spontaneous bleeding is deep, into muscles and joints
  4. Bleeding after trauma may be delayed and is prolonged
  5. Frequently restarts after stopping
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16
Q

What is the hallmark of haemophilia

A

Haemarthrosis - bleeding of joints

17
Q

NEVER GIVE HAEMOPHILIA PATIENTS

A

Intramuscular injection

18
Q

Differentiate bleeding due to coagulation defects vs platelet defects

A

Platelet defects = superficial bleeding into mucous/skin membranes. Bleeding immediate after injury

Coagulation defects = deep bleeding into tissues, muscles, joints. Delayed but severe bleeding, may be prolonged

19
Q

What are the tests done to test for coagulation disorders

A
  1. Screening tests (“clotting screen”) - Prothrombin time (PT), activated partial thromboplastin time (APTT), Full blood count (platelets)
  2. Factor assays (for F8 etc)
  3. Tests for inhibitors

APTT would be low if f9/12/8 missing

20
Q

Most bleeding disorders are not detected by routine clotting tests

A

T

21
Q

Describe how there may be disorders of fibrinolysis

A

Fibrinolysis disorders = rare, but can cause abnormal bleeding

Hereditary -
1. Antiplasmin deficiency

Acquired -

  1. Drugs e.g. tPA
  2. DIC
22
Q

Describe the genetics of haemophilia

A

X-linked recessive disorder

23
Q

Describe the genetics of VWD

A

Autosomal dominant disorder

except type 3 (rare) - recessive

24
Q

Describe the genetics of bleeding disorders (except haemophilia or VWD)

A

Autosomal recessive - much less common

25
Q

Describe the treatment plan of abnormal haemostasis

A

If failure of production/function - replace missing factor/platelets (prophylactic / therapeutic), stop drugs

If immune destruction - immunosuppression (e.g. prednisone), splenectomy for ITP

If increased consumption - treat cause, replace as necessary

26
Q

Describe some of the things we have to treat haemostatic disorders causing bleeding

A
  1. Factor replacement therapy - plasma (contains all coagulation factors), cryoprecipitate (rich in fibrinogen, F8, VWF, F13), factor concentrates (all factors minus f5, or prothrombin complex concentrates w/ f2, f7, f9, f10)
  2. Gene therapy - Haemophilia b/a
  3. Platelet replacement therapy
  4. Novel approaches - e.g. bispecific antibody, anti-TFPI antibody, antithrombin RNAi
27
Q

What are some other haemostatic treatments that are used

A
  1. DDAVP (iv) - releases endogenous stores (used in mild disorders)
  2. Tranexamic acid - inhibits fibrinolysis, widely distributed - crosses placenta. Low conc in breast milk. Useful adjunctive therapy
  3. Fibrin glue/spray
28
Q

Moderate haemophilia B will prolong which time?

A

APPT

29
Q

Prolongation of the PT may result from

A

F7 deficiency

30
Q

When are prothrombin complex concentrates used?

A

If no f2,7,910

31
Q

What treatment may be used for VWD

A

Oral contraceptive, intermediate purity VWF concentrates, ddavp, tranexamic acid

Year 2 Collin (114 decks)

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