Session 5 - Haemostasis + Thrombosis Flashcards
What four things does successful Haemostasis depend on?
- The vessel wall
- Platelets
- Coagulation system
- Fibrinolytic system
How can blood vessels ensure successful Haemostasis?
They constrict to limit blood loss
How can platelets help to ensure successful Haemostasis?
- adhere to damaged vessel walls + to each other
- form a platelet plug
How can Coagulation help to ensure successful Haemostasis?
- cascade series of the conversion of inactive -> active components
- Fibrinogen -> Fibrin
- balance of procoagulant and anticoagulant forces
How can the formation of thrombin have an effect on the Coagulative system?
It positively feeds back on factors V, VIII and XI causing the number of active molecules to increase
Name some thrombin inhibitors (4)
- Anti-thrombin III
- Alpha 1 anti-trypsin
- Alpha 2 macroglobulin
- Protein C/S
What do the inherited disorders in Anti-thrombin III and Protein C/S cause?
Thrombophilia and Thrombosis
What is fibrin broken down by?
Plasmin
In clot busters, what is the active ingredient and give two examples of when they may be used?
Active ingredient - Streptokinase which actives plasminogen
Uses:
- Coronary artery occlusion
- Thrombus cutting off circulation to a limb
What is thrombosis?
The formation of a solid mass of blood within the circulatory system during life
Name the three components of Virchow’s Triad, give examples for each
- Change in blood flow (Stagnation, turbulence)
- Changes in vessel wall (atheroma, injury, inflammation)
- Changes in blood components (smokers, pregnancy)
Name some features of an arterial thrombus
- pale
- granular
- lines of zahn
- lower cell content
Name some features of a Venus thrombus
- deep red
- soft
- gelatinous (jelly like)
- higher cell content
What are the effects of thrombosis in arteries?
- Ischaemia
- infarction
- depends on site + collateral circulation
Name some effects on a venous thrombus
- congestion
- oedema
- Ischaemia and infarction (only if tissue pressure > arterial pressure)
Name the five possible outcomes of thrombosis
- Lysis - (most likely with small thrombi)
- Propagation (distal in arteries, proximal in veins)
- Organisation (reparative process, in-growth of fibroblasts + capillaries, lumen remains obstructed)
- Recanalisation (channels through thrombus form, limited blood flow)
- Embolism
Define an embolism
Blockage of a blood vessel by a solid, liquid or gas at a site distant from its origin
Name the different types of emboli
- Thrombo-emboli (most common - 90%)
- air
- amniotic fluid
- nitrogen (the bends)
- medical equipment
- tumour cells
Where will a thrombus embolise if it forms in a systemic vein?
It will pass to the lungs forming a pulmonary emboli
Where will a thrombus embolise if it forms in the heart?
Pass via the aorta to renal, Mesenteric and other arteries
Where will a thrombus embolise if it forms in the atheromatous carotid arteries?
To the brain causing a stroke
Where will a thrombus embolise if it forms in the atheromatous abdominal arteries?
To the arteries of the legs
What can recurrent minor pulmonary embolisms cause?
Pulmonary hypertension
If a pulmonary embolism cuts off blood supply to >60% of the lungs, what is the most likely outcome?
Death
What are some likely causes of a deep vein thrombosis?
- immobility
- post-op or postpartum
- oral contraceptives
- severe burns
- cardiac failure
- disseminated cancer
What two ways do we treat DVT?
- intravenous Heparin - anticoagulant, co-factor for anti-thrombin III
- oral Warfarin - interferes with synthesis of Vit K dependent clot factors, slower acting
How can atrial fibrillation cause a cerebral embolism?
- AF leads to stasis and then a thrombus
- if in left heart, can go to brain + cause a stroke or transient Ischaemic attack
What is and what can cause an Iatrogenic embolism?
- embolism due to medical treatment
- air embolism from an injection
What can cause a nitrogenic embolism?
The bends
Nitrogen bubbles form in the blood with rapid decompression
What causes a fat embolism?
- fractures of long bones
- lacerations of adipose tissue
- causes a rash, shortness of breath and confusion
What is a disseminated Intravascular coagulation?
Pathological activation of coagulation mechanisms that happens in response to a variety of diseases.
Small clots form throughout the body using up all the clotting factors
Results in abnormal bleeding from the skin
What may trigger a disseminated Intravascular coagulation?
Infection, trauma, liver disease, obstetric complications
What is Haemophilia and what does it cause?
- X-linked recessive disorder causing a nonsense point mutation
- Factor VIII (type A) or Factor IX (type B) deficiency
- causes haemorrhage in retroperitoneum/ urinary tract
- haemorrhage into major joints, synovial Hypertrophy = pain
- muscle bleeding causes pressure and necrosis of nerves occurs
How is haemophilia treated?
Self-administered factor replacement therapy
Define Haemostasis
The body’s response to stop bleeding and loss of blood
What is the defect in Thrombocytopenia?
The platelet count is way below below reference range
What three things may cause the defect in thrombocytopenia?
- failure in platelet production Or - increase in platelet destruction Or - sequestering of platelets
