(W3) Haemorrhage, Haemostasis and Thrombosis

Question 1

What is haemorrhage and what causes it?

Answer 1

the escape of blood from vessels

Can be due to abnormal function or loss of integrity of:

• vessel or endothelium
• platelets
• coagulation factors

Question 2

What causes the abnormal function or loss of integrity of vessels and endothelium?

Answer 2

Congenital or acquired abnormalities in vessels:

• e.g. ruptured aneurysm
• e.g. abnormal collagen in Ehlers-Danlos syndrome, vitamin C deficiency (abnormal collagen in both causes abnormal wall integrity)

Trauma:
- physical disruption of vessels

Vascular erosion:
- e.g. fungal eroding vessel walls (e.g. fungal infection of guttural pouch - carotid erosion and consequent acute epistaxis nose bleed)

Endothelial injury:
- endotoxin, endotheliotropic viruses, immune complex deposition, uraemic toxins

Uraemia:
- caustic and lead to damage of vessel lining

Question 3

What causes decreased numbers (decreased production and increased loss) and abnormal function of platelets?

Answer 3

Decreased platelet numbers (thrombocytopenia):

• decreased production (radiation injury, oestrogen toxicity, viral, cytotoxic drugs)
• increased loss (e.g. immune mediated destruction, viral)
• Increased use (e.g. DIC- disseminated intravascular coagulation)

Abnormal platelet function:
- Congenital defects in platelet function
- NSAIDs (e.g. Aspirin)
- Uraemia
- Von Willibrand’s disease or von Willibrand destruction (lack of platelet
adhesion to site of clot formation)

Question 4

What is what is DIC, give an example of a condition where it occurs (leading to increased use of platelets)?

Answer 4

DIC = disseminated intravascular coagulation
- something is getting the body to use the platelets very fast

E.g. haemangiosarcoma - tumour consisting of blood vessels and forming abnormal blood vessels
○ Abnormal vessels mean that the tumour bleeds more frequently - platelets come to stop bleeding so platelets used up more than they can be produced