14 - Haemostasis 2

Question 1

What is haemostasis?

Answer 1

a state of equilibrium between fibrinolytic factors and anticoagulant proteins, and coagulation factors and platelets

Question 2

What are the characteristics of abnormal bleeding?

Answer 2

• spontaneous
• out of proportion to trauma/injury
• unduly prolonged
• restarts after appearing to stop

Question 3

What are the symptoms of primary haemostasis disorders?

Answer 3

• prolonged bleeding
• easily bruised
• prolonged epistasis
• prolonged menorrhagia
• get petechiae with thrombocytopenia

Question 4

What is petechiae?

Answer 4

• typical of thrombocytopenia
• small pin-prick type bleeding spots (more distal on legs)
• appear spontaneously
• not found with VWD

Question 5

What are the 3 types of von willebrand disease and their characteristics?

Answer 5

• type 1: not enough vWF produced
• type 2: uncorrect vWF produced
• type 3: no vWF produced

Question 6

What are the 3 defects of primary haemostasis?

Answer 6

• collagen (vessel wall)
• von willebrand factor
• platelets

Question 7

What are the features of a collagen defect in primary haemostasis?

Answer 7

• due to steroid therapy, age and scurvy
• less able to support blood vessels as get older
• vitamin c required to cross-link fibrin for security
• steroid therapy makes blood vessels more fragile and breaks down supporting tissue

Question 8

What are the features of a platelet defect in primary haemostasis?

Answer 8

• due to aspirin and thrombocytopenia
• aspirin inhibits platelet activity
• receptors on platelets can be missing
• thrombocytopenia is when there aren’t enough platelets

Question 9

What are the features of haemophilia?

Answer 9

• haemophilia a: lack of FVIII
• haemophilia b: lack of FIX
• genetic/hereditary
• no thrombin generated so no fibrin produced
• can form primary haemostatic plug
• plug not stabilised so bleeding continues

Question 10

What are some defects of secondary haemostasis?

Answer 10

• deficiency or defects of coagulation factors
• poor thrombin burst
• poor fibrin mesh
• genetic or acquired

Question 11

What are the acquired causes of secondary haemostasis?

Answer 11

• liver disease: less liver synthesis so less coagulation factors produced
• drugs: heparin and warfarin cause too much bleeding
• dilution: lower conc. of coagulation factors
• consumption
• disseminated intravascular coagulopathy: excessive activation of clotting cascade leads to depletion of coagulation factors and fibrinogen

Question 12

What are some genetic causes of secondary haemostasis?

Answer 12

• haemophilia
• antithrombin or protein s/c deficiency
• factor V leiden

Question 13

What is Virchow’s Triad and its features?

Answer 13

• vessel wall injury: increases thrombus risk with pro-coagulant haemostatic disorder, more likely to be arterial thrombus
• hypercoagulability: more likely to be venous thrombus
• stasis

Question 14

What is a thrombosis dependent on?

Answer 14

• speed of flow (stasis)
• blood composition (hypercoagulability)
• endothelium integrity (vessel wall injury)

Question 15

What are the features of thrombophilia?

Answer 15

• increases risk/tendency to form thrombosis
• occurs at young age
• treated with anti-coagulants

Question 16

What is the treatment and prevention of thrombosis?

Answer 16

• treatment to lyse clots (fibrinolytics and tPA)
• treatment to limit recurrence/extension/emboli:
  
  • heparin: increases anticoagulant activity
  • warfarin: lowers procoagulant factors
  • rivaroaxaban, apixaban and dabigatran: inhibit
    procoagulant factors
• prophylactic antithrombotic therapy

Question 17

What is the bleeding pattern of secondary haemostasis?

Answer 17

• delayed after primary haemostasis
• prolonged
• deeper (in joints and muscles)
• not from small cuts
• nosebleeds are rare
• bleeding after trauma/surgery
• after injections
• bleeding stops and starts

Question 18

What is a thrombosis?

Answer 18

• blood clot occurring where its not needed (intravascularly)
• intact blood vessel with clot in it
• venous or arterial (arterial driven by damage to vessel wall)

Question 19

What is the prevalence of venous thromboembolism?

Answer 19

• 1 in 1000-10000 per annum
• incidence doubles with each decade
• cause of 10% of hospital deaths

Question 20

What are the consequences of a thromboembolism?

Answer 20

• death
• recurrence
• thrombophlebitic syndrome
• pulmonary hypertension

Question 21

What are the effects of a thrombosis?

Answer 21

• obstructed blood flow (in artery causes MI, stroke and ischaemia and in vein causes pain and swelling)
• embolism - migration of thrombus (venous to lungs and arterial from heart)

Question 22

What are the effects of fibrinolysis?

Answer 22

• for vessel repair and dissolution of clot
• cell migration/proliferation
• restores vessel integrity
• defect of clot stability
• excess fibrinolytic (plasmin/tPA) - therapeutic administration and some tumours
• antiplasmin deficiency

Question 23

What is disseminated intravascular coagulation?

Answer 23

• generalised activation of coagulation (TF overdrive)
• associated with sepsis, inflammation and major tissue damage
• consumes and depletes coagulation factors and platelets
• activation of fibrinolysis depletes fibrinogen stores
• causes widespread bleeding and deposition of fibrin in vessel (causes organ failure)