Outline of the week and introduction to Haemostasis

Question 1

What is haemostasis​?

Answer 1

The arrest of bleeding and ​
the maintenance of vascular patency​

Question 2

Requirements of Haemostasis​ (4)

Answer 2

-Permanent state of readiness​
-Prompt response​
-Localised response​
-Protection against unwanted thrombosis​

Question 3

Components of Normal Haemostatic System (6)

Answer 3

Formation of platelet plug​= Primary Haemostasis​

Formation of fibrin clot​= Secondary Haemostasis​

Fibrinolysis​

Anticoagulant Defences​

Question 4

How are platelets formed?

Answer 4

in the bone marrow by ‘budding’ from megakaryocytes​

Question 5

Platelet structure and function (3)

Answer 5

Platelets are small anucleate discs with a mean life-span of 7-10 days

Endothelial (vessel wall) damage exposes collagen and releases Von Willebrand Factor (VWF), and other proteins to which platelets have receptors – platelet adhesion at the site of injury

There is then secretion of various chemicals from the platelets, which leads to aggregation of platelets at the site of injury.​

Question 6

Failure of Platelet Plug Formation - causes​ (5)

Answer 6

Vascular​

Platelets​
= Reduced number (thrombocytopenia)​
=Reduced function​

Von Willebrand Factor​

Question 7

Failure of Platelet Plug Formation- consequences (8)

Answer 7

Spontaneous Bruising and Purpura​

Mucosal Bleeding​
=Epistaxes​
=Gastrointestinal​
=Conjunctival​
=Menorrhagia​

Intracranial haemorrhage​

Retinal haemorrhages

Question 8

Screening Tests for Primary Haemostasis (2)

Answer 8

Platelet count​

No simple screening tests for other components of primary haemostasis​
​

Question 9

Fibrin Clot Formation

Answer 9

Secondary Haemostasis

Question 10

Failure of Fibrin Clot Formation - causes (8)

Answer 10

Single clotting factor deficiency​
=usually hereditary​
=eg Haemophilia​

Multiple clotting factor deficiencies​
usually acquired​
=eg Disseminated Intravascular =Coagulation​

Increased fibrinolysis​
= usually part of complex coagulopathy​

Question 11

Failure of Fibrin Clot Formation- consequences (5)

Answer 11

No characteristic clinical syndrome​

May be combined primary/secondary haemostatic failure​

Pattern of bleeding depends on​
=Single/multiple abnormalities​
=The clotting factors involved​

Question 12

Screening Tests for Fibrin Clot Formation​

Question 13

Clinical approach to bleeding disorders (7)

Answer 13

History​
=Bleeding/bruising​
=Duration (?life-long)​
=Previous surgery/dental extractions​

Drug History​

Family History​

Examination​

Question 14

Naturally occurring anticoagulants​ (2)

Answer 14

serine protease inhibitors

protein c + s

Question 15

Thrombophilia​ (3)

Answer 15

Deficiency of naturally occuring anticoagulants may be hereditary​

Increased tendency to develop venous thrombosis (deep vein thrombosis/pulmonary embolism)​

Also see venous thrombosis lecture​