Haemostasis And Thrombosis Flashcards
What does successful haemostasis rely on?
The vessel wall, platelets, the coagulation system and fibrinolytic system
What is haemostasis?
The body’s response to stop bleeding and loss of blood
What do platelets do?
Adhere to the damaged cell wall and to eachother to form a platelet plug
What is the platelet release reaction?
ATP is converted to ADP. This releases chemicals. ADP and thromboxane cause platelet aggregation. Platelet factor 3 (PF3) is released which is important for coagulation.
What does a cascade reaction allow?
Control, regulation and amplification
What is made in coagulation?
Prothrombin to thrombin
which causes the change of
fibrinogen to fibrin
How is the coagulation cascade regulated?
Thrombin positively feedback on factors V, VIII and XI.
There are thrombin inhibitors such as anti-thrombin III, α-1 antitrypsin and protein C/S
What is thrombophilia?
An inherited deficiency in the thrombin inhibitors antithrombin III or protein C/S
What is thrombosis?
The formation of a solid mass of blood within the circulatory system in life
Give some reasons for thrombosis
Abnormalities in the vessel wall such as injury, atheroma or inflammation
Abnormalities in blood flow - stagnant/turbulent
Abnormalities of blood components - in smokers, post partum, post op
What is the difference between clot and thrombosis
A clot is physiological - happens when you cut yourself and is outside of the circulatory system
Thrombosis is always pathological
What is the appearance of an arterial thrombus?
Pale, granular tissue, lines of Zahn, fewer red blood cells
What is the appearance of a venous thrombus?
Softer and gelatinous
Higher cell content
What are the outcomes of thrombosis?
Lysis Propagation Organisation Recanalisation Embolism
What is lysis?
Complete dissolution to the thrombus. Activation if fibrinolysis (with help of streptokinase). Blood flow is re-established.
What is propagation of a thrombus?
Progressive spread of the thrombus. Distally in arteries and proximally in veins.
What is organisation of a thrombus?
A reparative process with in-growth of fibroblasts and capillaries. The lumen remains obstructed
What is recanalisation of a thrombus?
Blood flow is re established but usually incompletely. One or more channels are formed through organisation.
What is an embolism?
Blockage of a blood vessel by a solid, liquid or gas at a site distant to its origin.
What are the effects if an arterial thrombus?
Ischaemia and infarction. Depends on site and collateral circulation.
What are the effects of a venous thrombus
Congestion, oedema, ischaemia, infarction
Types of embolism?
Thrombo-emboli Air Amniotic fluid Tumour cells Nitrogen Fatty embolism after a fracture Medical equipment
Where can thrombo-embolisms from systemic veins travel to?
To the lungs and cause a pulmonary embolism.
Where can embolism in the heart travel to?
The aorta to renal, mesentric and other arteries
Where can atheromatous carotid arteries travel to?
The brain and cause a stroke
Where can atheromatous abdominal aortic ones travel to?
Arteries of legs
Causes of a deep vein thrombosis?
Immobility/bed rest Post-o Pregnancy and post partum Oral contraceptives Severe burns Cardiac failure Disseminated cancer
Prevention of DVT?
High risk patients can by offered prophylaxis - heparin subcutaneously and leg compression during surgery
Treatment of a DVT?
Intravenous heparin followed by oral warfarin
Symptoms of a fat embolism?
Rash, shortness of breath, confusion
What can a cerebral embolism be caused by?
Atrial fibrillation
What is an iatrogenic embolism?
One caused by medical treatment such as air from an injection
What is disseminated intra vascular coagulation?
Pathological activation of coagulation mechanisms that happen in response to a variety of diseases.
What happens in disseminated intravascular coagulation?
Small clots form throughout the body, disrupting normal coagulation because they use up all the clotting factors.
Triggers of disseminated intravascular coagulation?
Infection
Trauma
Liver disease
Obstetric complications
What is haemophilia?
An X-linked recessive disease where there is a deficiency in clotting factors. Due to a nonsense point mutation.
What do type A and type B haemophilia each have a deficiency in?
Type A - factor VIII
Type B - factor IX
What symptoms can you get in haemophilia?
Haemorrhage into major joints
Synovial hypertrophy
Pain
Muscle bleeding causes pressure and necrosis of nerves
Can haemorrhage into retroperitoneum/urinary tract
How is haemophilia treated?
Factor replacement therapy
What is thrombocytopenia?
Low platelet count due to either failure of platelet production, increase in platelet destruction or sequestering of platelets.
What is thrombocytopenia usually accompanied with?
A bone marrow dysfunction such as leukaemia or anaemia
What is Virchow’s triad?
Hypercoagulability Haemodynamic changes (turbulence/stasis) Endothelial injury
