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Bleeding disorders Flashcards

1
Q

The process of coagulation requires

A

–Functioning platelets
–Functioning endothelium
–Coagulation factors

Balance
–Coagulant vs. anticoagulant factors

Imbalance
–Thrombosis
–Bleeding

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2
Q

What happens when you cut yourself?

A

Blood vessel damage
Disrupt endothelium

Exposure of
–Tissue Factor
–Collagen

Primary haemostasis
–Recruitment of platelets

Secondary haemostasis
–Activation of coagulation factors

Occur simultaneously

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3
Q

Primary haemostasis

A

Cut in the blood vessels exposes collagen and tissue factor

Also causes the exposure of von willebrand, which atrracts and binds platelets (through glycoprotein 1b_V-IX).

As platelets adhere to von willebrand, they become activated

Activation releases granular contents which cause aggregation and further activation of platelets

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4
Q

Secondary haemostasis

A

Activation of coaguation factors

Cascade of events:

  • Initation - extrinsic pathway
  • Propagantion- intrinsic pathway
  • thromin generation
  • fibrin producition - the clot
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5
Q

Initiation

A

ii- prothrombin

Prothrombinase complex- Xa + II (requires Va)

IIa- thrombin

thrombin activates XIII to cause cross linking of fibrin

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6
Q

Propagation

A

Thrombin feedsback to factor XI (becomes activated)

Interacts with IX and causes activation

Thrombin also activates factor VIIIa

VIIIa + IXa feedback to the prothrombinase complex and causes further fibrin to be made

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7
Q

Regulation

A

Antithrombin is a naturally occuring anti-coagulant that downreguates factor (7,10) (9,11) (10 +2) (9a + 2a)

Thrombomodulin is found on the endothelium. When thrombin is made it binds to thrombomodulin and then feedbacks and interacts with protein C. Protein C is activated to APC. APC plus another co-factor Protein S. Together these factors downregulate factor 5 and 8.

Tissue factor pathway inhibitor - downregulates pathway between tissue factor and factor VII

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8
Q

Fibrinolysis

A

Plasmin degrades fibrin

Plasmin comes from plasminogen (fibrin stimulates activation of plasminogen through tPA and uPA)

This process is regulated by alpha antiplasmin and PAI-1 and 2

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9
Q

Laborator analysis of coagulation

A

Assessment of primary haemostasis
–in vivo – Bleeding Time (cut the patient, measure clotting time)
–ex vivo – FBC (platelet count), platelet function

Assessment of secondary haemostasis
–Prothrombin time (PT)- measures the extrinsic system and the final common pathway- increased with warfarin
–Activated partial thromboplastin time (APTT)- measures the intrinsic and final common pathway - increased with heparin
–Thrombin clotting time (TCT) - measures the final part of the common pathway
–Individual coagulation factor assays

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10
Q

Samplle requirements

A

Plasma sample (blood thats not already clotted)

Prevent clotting

  • citrate sample (chelates all calcium prevents clotting
  • centrifugation (separates cellular component, add in synthetic phospholipid)

All results expressed

  • seconds
  • ration to normal plasma
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11
Q

What Clotting factors does PT measure?

A

Factors in extrinsic and common pathways

Factors VII

Factors X, V, II and fibrinogen

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12
Q

Acticated partial thromboplastin time (APTT) process?

A

Add
–Patient’s plasma
–Contact factor e.g. Kaolin or silica
–Phospholipid ( ‘partial thromboplastin’ )
Warm to 37°C
Add calcium
Time taken to clot
Normal range 26 - 38 secs
Ratio Patient/Average of 20 normals

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13
Q

Which clotting factors and clotting pathway does APTT measure?

A

–Factors in intrinsic and common pathways
–Factors VIII, IX, XI & XII
–and Factors X, V, II & Fibrinogen

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14
Q

Thrombin clotting time (TCT) process

A

Add at 37°C
–Patient’s plasma
–Bovine thrombin
–Less Calcium or phospholipid dependent
Time to clot
Normal 10-16 secs
Ratio Patient TT/Average of 20 normal TTs

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15
Q

What does TCT depend on and what is it inhibited by?

A

What does TCT depend on?
–How much fibrinogen is present in plasma
–How well that fibrinogen functions

But will also be prolonged by
–Inhibitors of thrombin (e.g. heparin, dabigatran)
–FDPs
Inhibitors of fibrin polymerisation (paraproteins

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16
Q

Simplified patterns of coagulation screen abnormality

A
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17
Q

Patterns of coaglation screen abnormality

18
Q

Clotting factor disorder definition

A

Congeital or acquired conditions that impair the body’s ability to control blood clotting resulting in inappropriate bleeding

Congenital

  • haemophillia A
  • haemophilla B
  • Von willebrands disease

Acquired

  • Liver disease
  • warfarin
  • Disseminated intravascular coagulation
19
Q

Disseminated intravascular coagulation (DIC) definition

A

Acquired, consumptive process
–Activation of coagulation cascade (Microthrombi)
–Exhaustion of coagulation cascade(Bleeding)

20
Q

Causes of disseminated intravascular coagulation (DIC)

A

–Sepsis
–Malignancy
–Massive haemorrhage
–Severe trauma
–Pregnancy complications e.g. pre-eclampsia, placental abruption, amniotic fluid embolism

21
Q

Pathophysiology of disseminated intravascular coagulation

22
Q

Laboratory Investigations DIC

A

LOOK FOR UNDERLYING CAUSE
–sepsis, trauma, cancer, obstetric disaster

  • Coagulation PT, APTT, Fibrinogen
  • D-dimers
  • FBC + film platelets, RBC fragments
23
Q

Treatment of DIC

A

TREAT UNDERLYING CAUSE

FFP +/- platelets if bleeding or high risk for bleeding

? Heparin 300-500u/h if thrombotic phenotype
? AT concentrate (reduces mortality 56% -> 44%)
? Protein C concentrate (meningococcal sepsis)
? Activated Protein C

24
Q

Two types of clotting factor disorders

A

Inherited

Acquired

25
Clinical features of Disseminated intravascular coagulation
- pyrexia - Acute abdomen - Paracolic abscess at laparotomy Raised PT time Raised APTT Very elevated D-DImers
26
How to treat warfarin bleeding ?
Any patients with haemorrhage and a raised INR - stop warfarin - Give coagulation factors ( II, VII, IX, X) Prothrombin complex concentrates
27
Dabigatran
Direct factor II PT- no effect APTT- if normal, insifnificant dabigatran effect TCT- highly sensitive at very low concentration
28
Rivaroxaban
DIrect factor Xa inhibitor PT- most sensitive (if normal, minimal rivaroxaban effect) APTT not useful s non-linear
29
Coagulopathy in liver disease
Liver produces all the coagulation factors except for vWf liver disease is therefore, associated iwith clotting factor deficiency and poor clearance In addition, biliary obstrucion can lead to malabsorption and deficiency of fat-soluble vitamin K Portal hypertension can lead to splenomegaly resulting in increased spelnic sequestration of plates - low WBC and plts
30
Haemophllia A ## Footnote Deficiency Pattern of inheritance Diagnosis Presentation Management
Normal primary haemostasis Deficiency of Factor VIII Sex linked recessive disorder (X-linked recessive) Diagnosos: Prolonged APTT - factors 8, 9 , 11, 12 and decreased factor 8 Presentation: depends on severity and is often in early life or after surgery/trauma - with bleeds into joints leading to criplling arthropathy and into muscles causing haematomas Management: Avoid NSAIDs, IM injections. Minor bleeds- desmopressin, pressure elevation. Major bleeds (e,g haemarthosis) require factor VIII
31
Haemophillia B
Christmas disease - factor IX deficiency inherited, x-linked recessive
32
Von willebrand disease ## Footnote Pattern of inheritance Cause : Clinical features Diagnosis Treatment
Autosomal dominant condition Commonest inherited coagulopathy in the UK Caused by quantitative or qualitative abnormality of vWF production vWF is made on endothelial cells. It is the glue that sticks platelets to damaged subendothelium Disease manifests with bruising, superficial purpura, menoorhagia, nose bleeds, bleeding from cuts and **mucous membranes - think primary haemostatic problem!!** Diagnosis is made by a. low factor VIII;c b. low factor vWF: Ag c. Prolonged bleeding time d. deficient ristocetin-induced platelet aggregation Treatment is with ddAVP if mld and with vWF concentrate
33
Types of von willebrand factor disease
**Type 3-** no von willebrand facor **Type 2-** Qualitative( von willebrand factor present but not functional) **Type 1-** Quantitave (Partial von willebrand functional, other half not)
34
Thrombophillia types
_Congenital_ 1. Deficencies of: * anti-thrombin III * Protein C * Protein S 2. Abnormal prothrombin molecule (increases prothrombin levels\_ 3. Dysfibrinogenaemia 4. Fibrinolytic defects 5. Factor V leiden mutation (renders factor V less sensitive to APC) _Acquired causes_ 1. Polycythaemia Rubra vera and essentiial thrombocythaemia 2. Lupus anticoagulant/antiphospholipid syndrome
35
Treatment of platelet disorders
- Pressure - Tranexamic acid / Desmopressin [DDAVP] - Platelet transfusion [HLA matched] - rFVIIa
36
Definition of thrombophillia
Disorders if haemostasis that increase the tendancy of blood to clot
37
Prolonged APPT test
Inhibits the coagulation process Prolonged APTT test Give 50:50 diltion (ml patient and ml of normal APTT) If factor deficiency is corrected then factor deificency If partial correction then inhibitor of APTT process - known as a lupus anticoagulant
38
Lupus anti-coagulant
- Phospholipid dependent antibody - Interferes with phospholipid dependent tests i.e. APTT - APTT prolonged - If persistent, may be associated with prothrombotic state - Persisting Lupus anticoagulant + thrombosis [or recurrent fetal loss] =Antiphospholipid Syndrome
39
Testing for lupus anticoagulant
APTT – often prolonged APTT 50:50 dilution – only partially corrects DRVVT ratio prolonged DRVVT ratio corrects with XS phospholipid
40
Warfarin
* extrinsic pathway * monitor with the INR (international normalized ratio) test * vitamin K-dependent pathway (vitamin K is a fat-soluble vitamin essential for the production of factors II, VII, IX and X; it enables the γ-carboxylation of the profactors to their active state) * the peak effect of warfarin occurs 48 h after ingestion – * warfarin has an early prothrombotic effect action as a result of its effects on proteins C + S (the body’s natural anticoagulants).
41
Heparin Important facts
* intrinsic pathway * monitor with the APTT (activated partial thromboplastin time) test * heparin potentiates the action of anti-thrombin 3 (which in turn activates thrombin and clotting factors VIII, IX, XI and XII) * half-life 2 h – low-molecular-weight heparins do not prolong the APTT; they have a predictable anticoagulant effect and do not require monitoring unless in long-term use; in this case use the factor Xa assay to assess the degree of anticoagulation * heparin-induced thrombocytopenia (HIT) is an immune reaction; it occurs in 5 per cent of patients and presets with thrombosis. Platelet activating arhibodies cause platelets to clump. This causes simultaneous thrombosis and thrombocytopaenia.
42
Thrombophillia definition
Disorders of haemostasis that increas the tendancy of bloot to clot.

Haematology (11 decks)

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