Haemostasis, Thrombosis And Embolism (6) Flashcards
How do platelets help reduce blood loss?
- Adhere to damaged vessel wall
- Adhere to each other
- Forms a platelet plug
What does homeostasis depend on?
- Vessel wall
- Platelets
- Coagulation system
- Fibrinolytic system
What is the platelet release reaction?
- ATP -> ADP
- ADP thromboxane A2 cause platelet aggregation
- 5HT platelet factor 3 also released
- PF3 important in coagulation
- Platelets coalesce after aggregation
How does coagulation occur?
- Series of inactive components -> active components (cascade)
- Prothrombin -> thrombin
- Thrombin stimulates fibrinogen -> fibrin
How is coagulation tightly regulated?
- Balance of pro coagulant and anticoagulant factors
What is Fibrinolysis?
- Breakdown of fibrin
- Plasminogen -> plasmin (catalysed by plasminogen activation)
Give 2 examples of fibrinolytic factors
- Streptokinase
- TPA
Give 4 examples of endothelium anti-thrombotic factors.
- Plasminogen activators
- Prostacyclin
- Nitrous oxide (NO)
- Thrombomodulin
What is a thrombosis?
- Formation of a solid mass of blood within circulation system
Why may a thrombosis form?
- Abnormalities of vessel wall
- Abnormalities of blood flow
- Abnormalities of blood components
How may abnormalities of the vessel wall occur?
- Atheroma
- Direct injury
- Inflammation
Why may abnormalities of blood flow occur?
- Stagnation
- Turbulence
How may abnormalities of blood components occur?
- Smoking
- Post-op
- Post-partum (post-natal)
What is the appearance of an arterial thrombus?
- Pale
- Granular
- Lines of Zahn
- Lower cells content
What is the appearance of a venous thrombi?
- Soft
- Gelatinous
- Deep red (higher cell content)
What are the 5 main outcomes of thrombosis?
- Lysis
- Propagation
- Organisation
- Recanalisation
- Embolism
What is lysis?
- Complete dissolution of a thrombus
- Fibrinolytic system active
- Bloodflow re-established
- Most likely when thrombi are small
What is propagation?
- Progressive spread of thrombosis
- Distally in arteries
- Proximally in veins
What is organisation as an outcome of thrombosis?
- Reparative process
- Ingrowth of fibroblasts and capillaries (like granulation tissue)
- Lumen remains obstructed
What is recanalisation?
- Bloodflow re-established but usually incomplete
- One or more channels formed through organising thrombus
What are the arterial effects of thrombosis?
- Ischaemia
- Infarction
- Depends of site and collateral circulation
What are the venous effects of thrombosis?
- Congestion
- Oedema
- Ischaemia
- Infarction
What is an embolism?
- Blockage of a blood vessel by solid, liquid or gas at a site DISTANT from its origin
What is the main type of embolism?
- Thrombo-embolism
What are the other possible types of embolisms?
- Air
- Amniotic
- N2
- Medical equipment
- Tumour cells
Where can thrombo-emboli originate from?
- Systemic veins pass to the lungs (PE)
- Heart pass via aorta to renal, mesenteric and other arteries
- Atheromatous carotid arteries pass to brain
- Atheromatous abdominal aorta pass to arteries of legs
What are the pre-disposing factors of deep vein thrombosis?
- Immobility
- Post-op
- Pregnancy and post natal
- Oral contraceptives
- Severe burns
- Cardiac failure
- Disseminated cancer
How can DVT be prevented?
- Heparin sub-cutaneously
- Leg compression during surgery
What treatment is there for DVT?
- Intravenous heparin
- Oral warfarin
What is a massive PE?
- > 60% reduction in bloodflow
- Rapidly fatal
What is a major PE?
- Medium sized vessels blocked
- SOB +/- cough and blood stained sputum
What is a minor PE?
- Small peripheral pulmonary arteries blocked
- Asymptomatic or minor SOB
What can recurrent minor PEs lead to?
- Pulmonary hypertension
