Haemorrhage, haemostasis and thrombosis

Question 1

What is a haemorrhage?

Answer 1

• bleeding
• red blood cells escaping from a blood vessel

Question 2

What can cause a haemorrhage?

Answer 2

• abnormal function
• loss of integrity of:
  • vessels or endothelium
  • platelets
  • coagulation factors

Question 3

How can changes in vessels and endothelium cause a haemorrhage?

Answer 3

• Congenital/ acquired abnormalities in vessels
  
  • e.g. ruptures aneurysm
  • abnormal collagen in Ehlers-Danlos syndrome (abnormal wall strength)
  • Vit C deficiency
• Trauma
• Vascular erosion
  
  • e.g. fungi eroding vessel walls
• • Endothelial injury
    
    • endotocin, endotheliotropic viruses, uraemic toxins

Question 4

What issues can occur with platelets causing haemorrhage?

Answer 4

• decreased platelet numbers (thrombocytopenia)
  
  • decreased production (e.g. radiation)
  • increased loss (e.g. immune mediated)
  • increased use (e.g. DIC)
• abnormal platelet function (thromboctopathy)
  
  • congenital defects in platelet function
  • NSAIDs (asparin)
  • Uremia
  • vWD (lack of platelet adhesion)

Question 5

How do coagulation factor deficiencies cause haemorrhage?

Answer 5

• Congenital deficiencies
• Acquired deficiencies
  • severe liver diseases resulting in decreased synthesis of factors
  • Vit K deficiency (factor II, VII, IX, protein C + S reduction)

Question 6

What is this showing?

Answer 6

• Petechia (Peterchiae) = a pinpoint haemorrhage
• Ecchymosis (Ecchymoses) = a larger (2/3cm) haemorrhage

Question 7

What can cause petechiae?

Answer 7

• electricution (stunning)

Question 8

What is ‘Suffusive haemorrhage’?

Answer 8

• affects larger areas of tissue

Question 9

What is this showing?

Answer 9

• spleen
• Haematoma = haemorrhage confined to a focal space

Question 10

What is this showing?

Answer 10

• Haemopericardium

Question 11

What would you call a haemorrhage in the thorax, pericardium and abdomen?

Answer 11

• Thorax - haemothorax
• Pericardium - haemopericardium
• Abdomen - haemoabdomen/ haemoperitoneum

Question 12

What are the antithrombotic factors?

Answer 12

• tPA (fibrinolysis)
• thrombomodulin (blocks coagulation cascade)

Question 13

Describe the important points of the coagulation cascade

Answer 13

• amplifying series of enxymatic conversions of proenzymes to active enzymes
• culminates in thrombin formation
• thrombin is the most important

Question 14

What is the role of thrombin?

Answer 14

• acts at numerous stages in cascade
• coverts soluble fibrinogen into fibrin monomers
• fibrin monomers polymerise into insoluble fibrin gel encasing platelets and circulating cells into a haemostatic plug

Question 15

Describe the process of fibrinolysis

Answer 15

• begins as soon as injury occurs
• limits size of haemostatic plug and then remove it after vessel is healed
• plasminogen is cleaved to form plasmin
• plasmin binds fibrin to limit growth of fibrin clot
• fibrin degradation products interfere with fibrin polymerisation, inhibit thrombin, and coat platelets to inhibit aggregation

Question 16

Describe Virchow’s Triad (and what is thrombosis?)

Answer 16

• thrombosis - formation of an inappropriate clot on the wall of a blood or lymphatic vessel or free in lumen

Question 17

What is this and why does it occur?

Answer 17

• arterial mural thrombosis
• the clot becomes more linear as it grows, due to the fast flowing blood in the arteries

Question 18

What is this showing?

Answer 18

• Lines of Zahn = alternating layers of platelets and fibrin admixed with erythrocytes
  
  • clot grows layer by layer
  • will look different if dead

Question 19

What is this showing and why does it occur in this way?

Answer 19

• Venous thrombosis - typically occlusive
  
  • blood is going slower - the clot can grow and fill the space

Question 20

What is this showing?

Answer 20

• thrombosis

Question 21

What levels of thromosis are these 3 showing?

Answer 21

• A - smaller thrombi removed by thrombolysis
• B - larger thrombi removed by phagocytosis of thrombolytic debris and granulation tissue formation, fibrosis and regrowth of endothelium on surface
• C - Occlusive thrombi- invaded by new fibroblasts and then recanalised by new vascular channels

Question 22

• What is this showing?

Answer 22

• Recanalisation

Question 23

What is ‘Emboli’?

Answer 23

• material travelling within blood vessels

Question 24

What is thromboemboli?

Answer 24

• fragments of thrombi

Question 25

What is fat emboli

Answer 25

* fat travelling within blood

Question 26

What is neoplastic emboli?

Answer 26

* tumour cells travelling in blood (one way tumours spread(

Question 27

What is air emboli?

Answer 27

* gas travelling within vessels

Question 28

What is bone or tissue emboli?

Answer 28

* bone or tissue fragments within blood

Question 29

What is fibrocartiagenous emboli?

Answer 29

* fibrocartilage from the intervertebral discs travelling in blood

Question 30

What is septic emboli?

Answer 30

* fragments of abscess or other infectious material travelling within blood

Question 31

What does this show?

Answer 31

* thromboemboli * saddle thrombus at the iliac bifurcation in a cat with hypertrophic cardiomyopathy